Hippocampal Cholinergic Neurostimulating Peptide (HCNP) is an undecapeptide cleaved from cytosolic phosphatidyl ethanolamine binding protein (PEBP). HCNP promotes development of cholinergic systems in hippocampus (Ojika et al 2001), one of the regions affected in autism (Bauman 1994). Crystal structure of PEBP predicts an autocatalytic release of the bioactive peptide triggered by change in its conformation after binding with the head group of phosphatidyl ethanolamine in the inner leaflet of membrane bilayer (Banfield et al, 1998, and Serre et al. 1998), although Ojika et al (2001) have proposed a putative protease for this purpose. We hypothesize that the amount and the rate of release of HCNP during development is minimally determined by the relative rate of accumulation of PE in membrane, by the amounts of PEBP synthesized in the cell, and by the relative rate of autocatalytic or protease mediated release. And we further hypothesize that one or all these factors are altered in autism. Data from our preliminary experiments indicate a 2-3-fold decrease in the amount of PE in autistic individuals. This may result in a decreased number of PEBP binding sites, and the possibility of a decrease in the amount of HCNP during critical times of development with adverse consequences for development of cholinergic systems. However, the relative importance of this finding in overall regulation of HCNP production in autism can be judged only if other alternatives are also considered. Thus an abnormality in the stoichiometry of PE, PEBP, HCNP and the putative protease may lead to abnormality of the cholinergic systems in autism.
S4.2.2
GENETIC LINKAGE AND ASSOCIATION OF HAPLOTYPES AT THE SEROTONIN TRANSPORTER LOCUS IN A RIGID-COMPULSIVE SUBPHENOTYPE OF AUTISM. JS Sutcliffe*, JL McCauley, M.Dowd, LM Olson, T Amin, RD Blakely, SE Folstein, and JL Haines. Program in Human Genetics, Center for Molecular Neuroscience, Vanderbilt Univ, Nashville, TN 37232, and Dept of Psychiatry, Tufts Univ, Boston, MA 02111.
Locus heterogeneity has complicated efforts to identify genes for autism. To identify genetically more homogeneous family subsets, we performed a factor analysis of the ADI to define subphenotypes in autism. Linkage analysis in a subset of families with compulsive behaviors and rigidity identified significantly increased evidence for linkage on 17q11.2, with a maximum HLOD of 2.82 at D17S1294. The serotonin transporter locus (SLC6A4) maps nearby and is proposed as a candidate in autism, based upon the effect of selective serotonin reuptake inhibitors in treating compulsions and anxiety in autism and findings of hyperserotonemia in a subset of people with autism. We genotyped SNPs across the SLC6A4 gene in 149 multiplex families. Three of these SNPs were recently proposed to associate with autism (Kim et al, Mol Psychiatry 7: 278, 2002). Analysis for linkage disequilibrium (LD) revealed allelic effects for one SNP in intron 5 (P < 0.02) and two multi-SNP haplotypes defined by three other SNPs (P < 0.02 and P < 0.04). Examination of the rigid-compulsive subset revealed substantially increased LD for the same haplotypes (P < 0.002 and P < 0.005). These data support a role for SLC6A4 in the etiology of autism and related traits, demonstrate the utility of subphenotypes for defining more homogeneous datasets for genetic studies and show that analysis of haplotypes is crucial for detection of risk alleles in complex genetic disease.
S4.2.3
SEROTONIN TRANSPORTER POLYMORPHISMS IN AUTISM SPECTRUM DISORDERS: ROLE IN BEHAVIORAL EXPRESSION E.J. Mulder, G. M. Anderson, A. de Bildt, N. van Lang, A. Brugman, C. Ketelaars, J. den Boer, I.P. Kema, R. Minderaa. Child and Adolescent Psychiatry, University of Groningen, PO Box 660, 9700 AR Groningen, the Netherlands
OBJECTIVE: The serotonin transporter gene (HTT) promoter ins/del and intron 2 VNTR polymorphisms are of special interest given the platelet hyperserotonemia of autism, the treatment effects of SSRIís and the role of serotonin in neurodevelopment. This study explored the role of these polymorphisms in autism spectrum disorders. METHOD: Patients diagnosed (N=125, age range 5-20 yrs, ADI and ADOS assessements, DSM-IV based criteria) with autism and autism spectrum disorders and their parents were genotyped. The transmission disequilibrium test (TDT) was used to examine possible preferential transmission of promoter [long (l), short (s)] and VNTR (10 or 12) alleles. Multivariate analyses were used to examine the relationship of genotype with continuous measures of autism-related behavior. RESULTS: Promoter and VNTR alleles were not preferentially transmitted. Analyses of continuous measures of autism-related behavior revealed that subjects with the l/l and l/s genotype were significantly more impaired on the communication and social domains of the ADOS. Subjects with the 10/10 and 10/12 genotype of the VNTR were significantly more impaired on the ADOS communication domain. CONCLUSIONS: These results suggest that the HTT alleles examined do not influence the risk for autism. However, they (or nearby alleles in linkage disequilibrium) may play a role in the severity of autism-related behaviors in the communication and social domains.
S4.2.4
GABAA RECEPTORS MEASURED WITH [11C]FLUMAZENIL PET IN CHILDREN WITH AUTISM, ANGELMAN AND LANDAU-KLEFFNER SYNDROMES. Diane C. Chugani,* Zolt·n Pfund, Sreenivasa Chandana, Michael E. Behen, Otto Muzik, Csaba Juh·sz, Jennifer Lee, Harry T. Chugani. Wayne State University School of Medicine, Detroit, Michigan.
Several subunits of the GABAA receptor are located at chromosome 15q11-q13, and deletions of this region occur in Angelman syndrome. Linkage to this region has been reported in autism. We measured GABAA receptor binding with positron emission tomography (PET) using [11C] flumazenil (FMZ) in children with autism (n=11), Angelman (n=3) and Landau-Kleffner (n=7) syndromes. Statistical parametric mapping (SPM) was applied to define the pattern of FMZ binding in the patients compared to 10 normal adults and 8 age-matched children with temporal lobe epilepsy. At the cluster level, the SPM analysis showed decreased FMZ binding in the occipital, temporal, and parietal lobes in all patient groups, as well as reduced binding in the cerebellar cortex in children with autism and Landau-Kleffner syndrome. At the voxel level, decreased receptor binding was found in the precuneus, angular, middle temporal and lingual gyri in all groups. Further decreases of FMZ binding were detected in the cuneus, calcarine cortex, and middle occipital gyrus in the autistic and Landau-Kleffner syndrome groups, while the superior temporal gyrus was involved only in children with Angelman syndrome. A region of interest analysis confirmed the SPM results, and showed additional decreased in the cerebellar cortex of children with Angelman syndrome. Low hemispheric VD values were measured in 4 autistic children and 1 child with Landau-Kleffner syndrome. These findings demonstrate a similar pattern of abnormal GABAA receptors in the three groups and a global decrease in a subgroup of these children.
S4.2.5
NEUROCHEMICAL CORRELATES OF INCREASED BRAIN STRUCTURALVOLUMES IN AUTISM S Friedman, D Shaw, A Artru, T Richards, J Gardner, G Dawson, S Posse, S Dager. Radiology, Univ. of Wash. Seattle WA 98105
Neuroimaging studies of autism have demonstrated age-related abnormalities in brain development, postulated to be accelerated growth between birth and approximately age six. In a young sample of 3- to 4-year-old children with autism spectrum disorder (ASD)(N=45), idiopathic delayed development (DD)(N=14), and typical development (TD)(N=26), we found larger cerebral volumes in children with ASD, along with proportional increases in volumes of the cerebellum and certain brain nuclei. In a subsample of the same children (ASD=45, DD=12, TD=9), regional examination of brain chemical composition using proton echo planar spectroscopic imaging (PEPSI), a 32×32 array of 1cm3 voxels at two anatomical levels, revealed regional concentration reductions (NAA, Cre, inositol) and prolonged T2r (a measure of chemical environment) for ASD subjects, suggesting altered cellular composition at this developmental time-point. To further understand relationships between neurochemical alterations and increased brain structural volumes in ASD, regression analyses across all PEPSI voxels were performed. Specifically, for each sample of tissue, the neurochemical measures were regressed by their corresponding tissue class (i.e. the percentage of gray/white matter), yielding a slope corresponding to gray/white matter chemical composition. From these measures, group comparisons in the regression function slope and intercept are currently being explored, with the aim of understanding whether neurochemical abnormalities in ASD are limited to a specific tissue type, and more generally, what cellular features relate to the aforementioned brain structural findings in ASD.
S4.2.6
CHROMATIN-REMODELING IN DEVELOPING HUMAN CEREBRAL CORTEX. IMPLICATIONS FOR AUTISM. S. Akbarian1* and Edward G. Jones2 (1) Brudnick Neuropsychiatric Research Institute, Dept. of Psychiatry, University of Massachusetts Medical School, Worcester, MA 01613; (3) Center for Neuroscience, University of California at Davis, CA 95616.
At least three X-linked mental retardation syndromes (ATRX, Coffin-Lowry and Rett) are caused by deleritious mutations of genes encoding chromatin-associated proteins, dramatically illustrating that defects in chromatin remodeling-mechanisms and epigenetic regulation of gene expression are a key factor in the molecular pathology of some cases of autism and mental retardation. Despite these recent breakthroughs in genetics of developmental brain disorders, presently nothing is known about chromatin-remodeling in the developing and adult brain. The post-translational, covalent modification of specific lysine, arginine and serine residues at the amino-terminal tails of histones H3 and H4 is considered a ëfinal common pathwayí of many chromatin-remodeling complexes. The focus of this study is the developmental regulation of histone methylation, acetylation and phosphorylation in postmitotic, differentiating neurons of the cerebral cortex. Using postmortem brain tissue from patients and age-matched controls, we will search for potential alterations in histone composition in autism spectrum disorders and mental retardation. S4.3.1BASIC & SOCIAL IMPAIRMENTS IN AUTISM: ROLE-TAKING OR THEORY OF MIND? R.P.Hobson, A.Lee and R.Garcia-Perez, Developmental Psychopathology Research Unit, Tavistock Clinic and University College, London, NW35BA
The aim of the study was to investigate basic forms of social impairment in autism. Adopting two complementary approaches to the study of social role-taking, we tested closely matched groups of children with and without autism (as defined by DSM-IV, and confirmed by the Childhood Autism Rating Scale) on two kinds of task: (i) a test of imitation, focusing on imitation of the gentle or harsh style of actions, and self-orientated actions (where accurate imitation requires someone to transpose the other personís self-orientation to become their own self-orientation), and (ii) a test of role-taking originally devised by Feffer (1970), that invites children to recount a story from the point of view of first one and then another protagonist. The results indicate that children with autism have specific and profound deficits in imitation, and more subtle limitations in narrative role-taking. These abnormalities are not explicable in terms of theory of mind (ie conceptual) deficits. We argue that fundamental to autism is an abnormality in basic forms of identification with other people. Such an approach promises to explain the somewhat contradictory literature on imitation deficits in autism, and may account for the childrenís difficulties in developing theory of mind concepts. Reference: Feffer, M. (1970). Role-taking behaviour in the mentally retarded. Final report, office of education (DHEW), Washington, DC Bureau of Education for the Handicapped. Bureau number: BR-42-2029. ED:039.681
S4.3.2
THE EXPRESSION AND UNDERSTANDING OF JEALOUSY IN HIGH-FUNTIONING CHILDREN WITH AUTISM. N. Bauminger Bar Ilan Univ. Sch. Of Education, Ramat Gan, Israel 52900
Jealousy is a complex, unpleasant feeling. Two types of jealousy were identified: social relations jealousy (SRJ);feelings that arise in situations that questioned oneís exclusivity in a relationships, and social-comparison jealousy (SCJ);situations in which oneís superiority or equality is challenged. Both the ability to develop valued relationships with others and the ability to make comparisons based on the differentiation between the self and others are questionable in the understanding of autism. Thus, the examination of jealousy may shed light on the emotional deficit in autism. The expression and understanding of jealousy were investigated in 16 preadolescents and adolescents high functioning children with autism and 17 typically developing children matched for IQ, mental-age, chronological age, gender, and maternal education. Expression of jealousy was examined via the experimental childrenís behaviors, verbalizations, and affects demonstrated during two jealousy-provoking traidic scenarios (playing & SRJ and drawing & SCJ) enacted between the experimental child (autism or typical), the experimental childís main caregiver (mostly mothers), and a familiar peer or sibling. Children also asked to identify jealousy from a picture, to provide examples of times they felt jealous, and to offer suggestions for coping with jealousy. Main results revealed that children with autism expressed jealousy in similar situations as their typical age mates, but manifested it in different behaviors. Also, they revealed a less coherent understanding of the feeling. The meaning of the gap between demonstrating and understanding jealousy is discussed in light of the two central theoretical views conceptualizing the core emotional deficit in autism.
S4.3.3
SOCIAL INFORMATION PROCESSING IN CHILDREN WITH AUTISM H. Roeyers, A. Buysse, & K. Ponnet Research Group Developmental Disorders, Ghent University. Ghent, Belgium, B-9000
Research on cognitive schemas (Smith, 1998) has generated paradigms that are useful to shed more light on social information processing in people with autism. An activated schema affects the interpretation of related information. A second effect of an activated schema is to direct attention to both schema-consistent and inconsistent information. Schemas can also influence recall. It is generally assumed that schemas facilitate retrieval of consistent information that was not present in a particular situation. In addition, schema-relevant information is better recalled and recognized than schema-irrelevant information (Baldwin, 1992). In the present study, 36 high-functioning boys with autism, between the ages of 8 and 12, and 36 age- and IQ-matched controls, watched a video in which 2 boys, aged 9 and 10, talk about their leisure activities, family and school. Recognition of consistent, inconsistent and irrelevant information was evaluated by means of a questionnaire. The questionnaire consisted of items that were present in the video (hits) as well as of items that were not present (false alarms). It was hypothesised that the recognition of control children would be biased by their cognitive schemas, i.e more correct recognition of relevant information (both hits and false alarms) than of irrelevant information and more incorrect recognition of consistent than of inconsistent false alarms. Following the central coherence theory, it was predicted that recognition of children with autism would be unbiased: i.e. independent of relevance or consistency of the information. Children with autism were less able than control children to recognize hits and this was the case for all types of information. As for false alarms, there were no significant differences between both groups. As such the results suggest at least some impact of cognitive schemas on information processing in social situationns. A second study, in which level-of-processing task was used, led to similar conclusions.
S4.3.4
A COMPARATIVE STUDY OF FIGURATIVE LANGUAGE AND HUMOUR IN CHILDREN WITH AUTISTIC SPECTRUM DISORDERS G. MacKay & A. Shaw, Department of Educational Support & Guidance, University of Strathclyde, Glasgow, Scotland, G13 1PP.
Difficulties with figurative language and humour have been highlighted by many researchers and people with autism as a core problem in autism. This study evaluated figurative language skills and humour comprehension in able autistic children. A group of autistic children and a group of age matched non-autistic peers were compared using a test of figurative language and humour devised by the authors for the investigation. The test focuses on understanding the meaning of an utterance, and understanding the intentionality behind an utterance. The test incorporates eight types of figurative utterances and two types of verbal jokes. The study shows the discrepancies in understanding between the two groups of children across all parameters investigated. It also highlights some idiosyncrasies and trends specific to the autistic group. The results are discussed in terms of their clinical and theoretical importance. Possible explanations for the results are explored and implications for future research and practical application are proposed.
S4.3.5
INTERMODAL MATCHING OF EMOTIONAL EXPRESSIONS IN YOUNG CHILDREN WITH AUTISM R. Kahana-Kalman* and S. Goldman. Dept. of Pediatrics, Albert Einstein College of Medicine, Bronx, NY, 10461.
Young children with autism spectrum disorders (n=18, mean chronological age = 4 years; 1 mos.) and their age-matched normally developing peers (n=18) participated in a study of the ability to detect intermodal correspondence between facial and vocal information for affect in familiar and unfamiliar expressions. Participants were presented 12 pairs of videotaped facial expressions (happy, sad, and angry) portrayed by their mothers and by an unfamiliar woman. The facial expressions were presented side-by-side on two adjacent TV monitors. The soundtrack, affectively matching one facial expression but not the other was played from a central speaker. The soundtrack was desynchronized with both displays, and thus rhythmic synchrony information was reduced, making it more likely that participants used emotion information to make the match. In a control condition, 8 pairs of inanimate objects (toys) and their sounds were presented. Measures of looking times to the sound-matched versus non-sound matched displays were compared. Results indicated no group differences in intermodal matching in the condition using inanimate objects. As did their normally developing peers, children with autism looked significantly longer to the facial expressions that were accompanied by affectively matching vocal expressions portrayed by their mothers. However, unlike their normally developing peers they did not show preferences for sound-matched emotions of an unfamiliar woman. These results show that children with autism do not have a general inability to detect intermodal correspondences between visual and vocal events, including emotions, but that they were less sensitive than age-matched peers in some conditions. The increased sensitivity of children with autism to familiarity in their recognition of emotional expressions is discussed in terms of implications for early intervention. S4.4.1PHENOMENOLOGY OF RESTRICTED REPETITIVE BEHAVIOR IN AUTISM: COMPARISON TO NONSPECIFIC MENTAL RETARDATION J.W. Bodfish, D.E. Parker, J. L Hawkins, & M. H. Lewis UNC Human Development Research Institute, Western Carolina Center, Morganton, NC 28655
In the present study, we compared groups of adults with autism (n = 36) and nonspecific specific mental retardation (n = 36) on a standardized measure of repetitive behavior ñ the Repetitive Behavior Scale – Revised (RBS-R). The RBS-R is an empirically-derived rating scale for measuring the occurrence and severity of repetitive behaviors. The six subscales of the RBS-R provide measures of the varieties of repetitive behavior seen in individuals with autism ñ Stereotypy, Self-injury, Compulsions, Rituals, Sameness Behavior, Restricted Behavior. Comparisons of the AUT and MR groups revealed that each type of repetitive behavior occurred frequently in both groups, and no category was uniquely associated with autism. However, the prevalence (% of cases) of each behavior category was significantly higher in the autism group. Within the AUT group, overall repetitive behavior severity was significantly related (r = 0.57) to overall severity of autism. Further, with the exception of self-injury, the addition of each discrete category of repetitive behavior contributed significantly to a multiple regression equation predicting overall autism severity (adjusted ABC score). These results indicate that no single form of abnormal repetition is specific to autism, but that an elevated pattern of occurrence and co-occurrence appears to characterize the disorder. Also, the pattern of co-occurring repetitive behaviors associated with autism appears to involve both lower-order repetitive behaviors (stereotyped movements) and higher-order repetitive behaviors (rituals, sameness behavior).
S4.4.2
ENVIRONMENTAL DETERMINANTS OF SELF-INJURY, STEREOTYPY, AND AGGRESSION. B.A. Iwata, E.M. Roscoe, J. Conners, and B.A. Shore. Psychology Department, University of Florida, Gainesville, FL 32611.
Functional analysis methodology has been used extensively as a clinical-research tool on an individual basis to identify sources of reinforcement for problem behavior, to develop treatment procedures, and to select individuals for inclusion in studies on the effects of specific interventions. By contrast, relatively few studies have applied the methodology across large numbers of individuals presenting with the same problem behavior. This presentation will summarize results from four separate longitudinal studies in which functional analyses were conducted of (a) self-injurious behavior (SIB), (b) noninjurious stereotypic behavior (STPY), (c) hand mouthing (HM, which may or may not be self-injurious), and (d) aggression (AGG). Striking differences were observed in the distribution of behavioral function across responses: AGG was maintained exclusively by social reiforcement, whereas STPY and HM wee maintained almost exclusively by nonsocial (automatic) reinforcement. Finally, SIB was maintianed by multiple sources of control. Factors accounting for these differences, as well as implications for treatment, are noted.
S4.4.3
STRUCTURAL MRI MEASUREMENT OF THE BASAL GANGLIA IN PRESCHOOLERS WITH AUTISM Cody, H., Stephens, K., Gimpel, R., Taylor, D., and Piven, J. Department of Psychiatry, University of North Carolina, Chapel Hill, NC 27599.
The ritualistic, repetitive behaviors characteristic of autism have been associated with the basal ganglia, and specifically linked to the caudate nucleus. This component of the basal ganglia has been correlated with stereotypical behaviors in animal and lesion studies. The basal ganglia have also been implicated in other disorders, such as Obsessive-Compulsive Disorder and Touretteís Syndrome, that share some of these features (Rosenberg and Keshavan, 1988; Peterson et al., 1993). Sears, et al. (1999) found the caudate to be increased in two independent groups of adolescents and adults with autism. In their study, caudate volume was also significantly correlated with stereotyped, repetitive behaviors on the Autism Diagnostic Interview (ADI-R), but not with the social or communication domains. Specifically, there were correlations between caudate volume and compulsions and rituals, difficulties with minor change in environment and routine, and complex motor behaviors. Increased caudate volume has also been found to correlate with ritualistic-repetitive behaviors in Fragile X (Reiss et al., 1995). Since these behaviors often emerge early in development, we hypothesized that the findings of increased caudate size would be evident in a preschool sample of children with autism. In this study, we compared the size of the caudate, putamen, and globus pallidus in young children with autism (18-35 months) to that of typically developing peers and children with developmental delay. Our findings are discussed in relation to the role that the caudate may play in the stereotyped, repetitive behaviors associated with autism.
S4.4.4
An Animal Model of Restricted, Repetitive Behavior in Autism. M.H. Lewis, C.A. Turner & M.F. Presti. Dept. of Psychiatry, Univ. of Florida, Gainesville, FL, 32601.
A wide variety of abnormal repetitive behaviors (e.g., stereotypies, compulsions) occur in persons with autism. Although restricted, repetitive patterns of behavior are one of the defining features of this disorder, these behaviors have received much less attention than social and communication deficits. We have characterized an animal model of the repetitive behaviors seen in persons with autism and related developmental disorders. Laboratory reared deer mice exhibit high rates of spontaneous stereotyped behavior that occurs early in development and persists through much of the lifetime of the animal. Early experience in the form of environmental enrichment for 60 days post-weaning was found to markedly reduce vulnerability to develop these behaviors. Brain changes associated with such experiential effects on behavior were indexed using measures of neuronal metabolic activity (cytochrome oxidase histochemistry) and dendritic morphology (spine density). Enriched, stereotypic mice and mice housed in standard lab cages (stereotypic and non-stereotypic) did not differ on either of these measures. Enriched, non-stereotypic mice, however, were found to have higher levels of neuronal metabolic activity and increased dendritic spine density in motor cortex and basal ganglia compared to these groups. Our pharmacological findings have highlighted the importance of striatal glutamate and dopamine in the mediation of stereotyped behavior. Thus, biochemical, morphological and pharmacological findings point to the importance of the cortico-striato-thalamo-cortical circuitry in the development and expression of spontaneous stereotyped behavior in this animal model of repetitive behavior in autism.
S4.4.5
CHROMOSOME 15 AND AUTISM: CLINICAL CHARACTERIZATION OF PHENOTYPE 1Cuccaro M, 1Donnelly S, 1Shao S, 2Ravan S, 2Abramson R, , 1Wolpert C, 1Elston L, 1Wright H, 2Pericak-Vance MA. 1Center For Human Genetics, Duke Univ Med Center, Durham NC, USA 2William S. Hall Psychiatric Institute, Univ of South Carolina, Columbia SC, USA
Autism (AutD) is a complex neurodevelopmental disorder that is genetically and clinically heterogeneous. Chromosomal region 15q11-q13 is a candidate region based on cytogenetic linkage and association findings. Ordered subset analysis (OSA) is an analytic method that identifies a homogenous subset of individuals that contributes to linkage in a particular chromosomal region. Using a factor derived from restricted and repetitive behaviors as the OSA covariate, a subset of 23 AutD families were identified as contributors to linkage on Chr 15 (OSA N=46; 23 sibpairs). We compared these Chr 15 AutD sibpairs with the remaining AutD families that did not show evidence for linkage on composite indices from the Autism Diagnostic Interview-R (ADI-R) and Vineland Adaptive Behavior Scales (VABS). The OSA defined subset was more impaired on a measure of social functioning (VABS Socialization t=2.72, p=0.007)and showed a trend toward significance reflective of lower overall adaptive functioning (Adaptive Behavior Composite t=1.91, p=0.058). The groups did not differ on either the ADI-R or VABS communication indices. These results suggest a greater degree of social impairment in the OSA defined Chr15 AutD group. The results are consistent with the hypothesis that increased repetitive behavior exerts an effect on social and behavioral functioning. Additional efforts to investigate different phenotypic expression in AutD populations for application to genetic analysis will be extremely valuable in delineating the boundaries of AutD.SLIDE SESSION 4.2: NEUROCHEMISTRY
S4.2.1
HIPPOCAMPAL CHOLINERGIC NEUROSTIMULATING PEPTIDE IN AUTISM? Omanand Koul, UMass Medical School at Shriver Center, Waltham, MA 02452
Hippocampal Cholinergic Neurostimulating Peptide (HCNP) is an undecapeptide cleaved from cytosolic phosphatidyl ethanolamine binding protein (PEBP). HCNP promotes development of cholinergic systems in hippocampus (Ojika et al 2001), one of the regions affected in autism (Bauman 1994). Crystal structure of PEBP predicts an autocatalytic release of the bioactive peptide triggered by change in its conformation after binding with the head group of phosphatidyl ethanolamine in the inner leaflet of membrane bilayer (Banfield et al, 1998, and Serre et al. 1998), although Ojika et al (2001) have proposed a putative protease for this purpose. We hypothesize that the amount and the rate of release of HCNP during development is minimally determined by the relative rate of accumulation of PE in membrane, by the amounts of PEBP synthesized in the cell, and by the relative rate of autocatalytic or protease mediated release. And we further hypothesize that one or all these factors are altered in autism. Data from our preliminary experiments indicate a 2-3-fold decrease in the amount of PE in autistic individuals. This may result in a decreased number of PEBP binding sites, and the possibility of a decrease in the amount of HCNP during critical times of development with adverse consequences for development of cholinergic systems. However, the relative importance of this finding in overall regulation of HCNP production in autism can be judged only if other alternatives are also considered. Thus an abnormality in the stoichiometry of PE, PEBP, HCNP and the putative protease may lead to abnormality of the cholinergic systems in autism.
S4.2.2
GENETIC LINKAGE AND ASSOCIATION OF HAPLOTYPES AT THE SEROTONIN TRANSPORTER LOCUS IN A RIGID-COMPULSIVE SUBPHENOTYPE OF AUTISM. JS Sutcliffe*, JL McCauley, M.Dowd, LM Olson, T Amin, RD Blakely, SE Folstein, and JL Haines. Program in Human Genetics, Center for Molecular Neuroscience, Vanderbilt Univ, Nashville, TN 37232, and Dept of Psychiatry, Tufts Univ, Boston, MA 02111.
Locus heterogeneity has complicated efforts to identify genes for autism. To identify genetically more homogeneous family subsets, we performed a factor analysis of the ADI to define subphenotypes in autism. Linkage analysis in a subset of families with compulsive behaviors and rigidity identified significantly increased evidence for linkage on 17q11.2, with a maximum HLOD of 2.82 at D17S1294. The serotonin transporter locus (SLC6A4) maps nearby and is proposed as a candidate in autism, based upon the effect of selective serotonin reuptake inhibitors in treating compulsions and anxiety in autism and findings of hyperserotonemia in a subset of people with autism. We genotyped SNPs across the SLC6A4 gene in 149 multiplex families. Three of these SNPs were recently proposed to associate with autism (Kim et al, Mol Psychiatry 7: 278, 2002). Analysis for linkage disequilibrium (LD) revealed allelic effects for one SNP in intron 5 (P < 0.02) and two multi-SNP haplotypes defined by three other SNPs (P < 0.02 and P < 0.04). Examination of the rigid-compulsive subset revealed substantially increased LD for the same haplotypes (P < 0.002 and P < 0.005). These data support a role for SLC6A4 in the etiology of autism and related traits, demonstrate the utility of subphenotypes for defining more homogeneous datasets for genetic studies and show that analysis of haplotypes is crucial for detection of risk alleles in complex genetic disease.
S4.2.3
SEROTONIN TRANSPORTER POLYMORPHISMS IN AUTISM SPECTRUM DISORDERS: ROLE IN BEHAVIORAL EXPRESSION E.J. Mulder, G. M. Anderson, A. de Bildt, N. van Lang, A. Brugman, C. Ketelaars, J. den Boer, I.P. Kema, R. Minderaa. Child and Adolescent Psychiatry, University of Groningen, PO Box 660, 9700 AR Groningen, the Netherlands
OBJECTIVE: The serotonin transporter gene (HTT) promoter ins/del and intron 2 VNTR polymorphisms are of special interest given the platelet hyperserotonemia of autism, the treatment effects of SSRI’s and the role of serotonin in neurodevelopment. This study explored the role of these polymorphisms in autism spectrum disorders. METHOD: Patients diagnosed (N=125, age range 5-20 yrs, ADI and ADOS assessements, DSM-IV based criteria) with autism and autism spectrum disorders and their parents were genotyped. The transmission disequilibrium test (TDT) was used to examine possible preferential transmission of promoter [long (l), short (s)] and VNTR (10 or 12) alleles. Multivariate analyses were used to examine the relationship of genotype with continuous measures of autism-related behavior. RESULTS: Promoter and VNTR alleles were not preferentially transmitted. Analyses of continuous measures of autism-related behavior revealed that subjects with the l/l and l/s genotype were significantly more impaired on the communication and social domains of the ADOS. Subjects with the 10/10 and 10/12 genotype of the VNTR were significantly more impaired on the ADOS communication domain. CONCLUSIONS: These results suggest that the HTT alleles examined do not influence the risk for autism. However, they (or nearby alleles in linkage disequilibrium) may play a role in the severity of autism-related behaviors in the communication and social domains.
S4.2.4
GABAA RECEPTORS MEASURED WITH [11C]FLUMAZENIL PET IN CHILDREN WITH AUTISM, ANGELMAN AND LANDAU-KLEFFNER SYNDROMES. Diane C. Chugani,* Zoltán Pfund, Sreenivasa Chandana, Michael E. Behen, Otto Muzik, Csaba Juhász, Jennifer Lee, Harry T. Chugani. Wayne State University School of Medicine, Detroit, Michigan.
Several subunits of the GABAA receptor are located at chromosome 15q11-q13, and deletions of this region occur in Angelman syndrome. Linkage to this region has been reported in autism. We measured GABAA receptor binding with positron emission tomography (PET) using [11C] flumazenil (FMZ) in children with autism (n=11), Angelman (n=3) and Landau-Kleffner (n=7) syndromes. Statistical parametric mapping (SPM) was applied to define the pattern of FMZ binding in the patients compared to 10 normal adults and 8 age-matched children with temporal lobe epilepsy. At the cluster level, the SPM analysis showed decreased FMZ binding in the occipital, temporal, and parietal lobes in all patient groups, as well as reduced binding in the cerebellar cortex in children with autism and Landau-Kleffner syndrome. At the voxel level, decreased receptor binding was found in the precuneus, angular, middle temporal and lingual gyri in all groups. Further decreases of FMZ binding were detected in the cuneus, calcarine cortex, and middle occipital gyrus in the autistic and Landau-Kleffner syndrome groups, while the superior temporal gyrus was involved only in children with Angelman syndrome. A region of interest analysis confirmed the SPM results, and showed additional decreased in the cerebellar cortex of children with Angelman syndrome. Low hemispheric VD values were measured in 4 autistic children and 1 child with Landau-Kleffner syndrome. These findings demonstrate a similar pattern of abnormal GABAA receptors in the three groups and a global decrease in a subgroup of these children.
S4.2.5
NEUROCHEMICAL CORRELATES OF INCREASED BRAIN STRUCTURALVOLUMES IN AUTISM S Friedman, D Shaw, A Artru, T Richards, J Gardner, G Dawson, S Posse, S Dager. Radiology, Univ. of Wash. Seattle WA 98105
Neuroimaging studies of autism have demonstrated age-related abnormalities in brain development, postulated to be accelerated growth between birth and approximately age six. In a young sample of 3- to 4-year-old children with autism spectrum disorder (ASD)(N=45), idiopathic delayed development (DD)(N=14), and typical development (TD)(N=26), we found larger cerebral volumes in children with ASD, along with proportional increases in volumes of the cerebellum and certain brain nuclei. In a subsample of the same children (ASD=45, DD=12, TD=9), regional examination of brain chemical composition using proton echo planar spectroscopic imaging (PEPSI), a 32×32 array of 1cm3 voxels at two anatomical levels, revealed regional concentration reductions (NAA, Cre, inositol) and prolonged T2r (a measure of chemical environment) for ASD subjects, suggesting altered cellular composition at this developmental time-point. To further understand relationships between neurochemical alterations and increased brain structural volumes in ASD, regression analyses across all PEPSI voxels were performed. Specifically, for each sample of tissue, the neurochemical measures were regressed by their corresponding tissue class (i.e. the percentage of gray/white matter), yielding a slope corresponding to gray/white matter chemical composition. From these measures, group comparisons in the regression function slope and intercept are currently being explored, with the aim of understanding whether neurochemical abnormalities in ASD are limited to a specific tissue type, and more generally, what cellular features relate to the aforementioned brain structural findings in ASD.
S4.2.6
CHROMATIN-REMODELING IN DEVELOPING HUMAN CEREBRAL CORTEX. IMPLICATIONS FOR AUTISM. S. Akbarian1* and Edward G. Jones2 (1) Brudnick Neuropsychiatric Research Institute, Dept. of Psychiatry, University of Massachusetts Medical School, Worcester, MA 01613; (3) Center for Neuroscience, University of California at Davis, CA 95616.
At least three X-linked mental retardation syndromes (ATRX, Coffin-Lowry and Rett) are caused by deleritious mutations of genes encoding chromatin-associated proteins, dramatically illustrating that defects in chromatin remodeling-mechanisms and epigenetic regulation of gene expression are a key factor in the molecular pathology of some cases of autism and mental retardation. Despite these recent breakthroughs in genetics of developmental brain disorders, presently nothing is known about chromatin-remodeling in the developing and adult brain. The post-translational, covalent modification of specific lysine, arginine and serine residues at the amino-terminal tails of histones H3 and H4 is considered a ‘final common pathway’ of many chromatin-remodeling complexes. The focus of this study is the developmental regulation of histone methylation, acetylation and phosphorylation in postmitotic, differentiating neurons of the cerebral cortex. Using postmortem brain tissue from patients and age-matched controls, we will search for potential alterations in histone composition in autism spectrum disorders and mental retardation.
SLIDE SESSION 4.3: SOCIAL INFORMATION PROCESSING 2
S4.3.1
BASIC & SOCIAL IMPAIRMENTS IN AUTISM: ROLE-TAKING OR THEORY OF MIND? R.P.Hobson, A.Lee and R.Garcia-Perez, Developmental Psychopathology Research Unit, Tavistock Clinic and University College, London, NW35BA
The aim of the study was to investigate basic forms of social impairment in autism. Adopting two complementary approaches to the study of social role-taking, we tested closely matched groups of children with and without autism (as defined by DSM-IV, and confirmed by the Childhood Autism Rating Scale) on two kinds of task: (i) a test of imitation, focusing on imitation of the gentle or harsh style of actions, and self-orientated actions (where accurate imitation requires someone to transpose the other person’s self-orientation to become their own self-orientation), and (ii) a test of role-taking originally devised by Feffer (1970), that invites children to recount a story from the point of view of first one and then another protagonist. The results indicate that children with autism have specific and profound deficits in imitation, and more subtle limitations in narrative role-taking. These abnormalities are not explicable in terms of theory of mind (ie conceptual) deficits. We argue that fundamental to autism is an abnormality in basic forms of identification with other people. Such an approach promises to explain the somewhat contradictory literature on imitation deficits in autism, and may account for the children’s difficulties in developing theory of mind concepts. Reference: Feffer, M. (1970). Role-taking behaviour in the mentally retarded. Final report, office of education (DHEW), Washington, DC Bureau of Education for the Handicapped. Bureau number: BR-42-2029. ED:039.681
S4.3.2
THE EXPRESSION AND UNDERSTANDING OF JEALOUSY IN HIGH-FUNTIONING CHILDREN WITH AUTISM. N. Bauminger Bar Ilan Univ. Sch. Of Education, Ramat Gan, Israel 52900
Jealousy is a complex, unpleasant feeling. Two types of jealousy were identified: social relations jealousy (SRJ);feelings that arise in situations that questioned one’s exclusivity in a relationships, and social-comparison jealousy (SCJ);situations in which one’s superiority or equality is challenged. Both the ability to develop valued relationships with others and the ability to make comparisons based on the differentiation between the self and others are questionable in the understanding of autism. Thus, the examination of jealousy may shed light on the emotional deficit in autism. The expression and understanding of jealousy were investigated in 16 preadolescents and adolescents high functioning children with autism and 17 typically developing children matched for IQ, mental-age, chronological age, gender, and maternal education. Expression of jealousy was examined via the experimental children’s behaviors, verbalizations, and affects demonstrated during two jealousy-provoking traidic scenarios (playing & SRJ and drawing & SCJ) enacted between the experimental child (autism or typical), the experimental child’s main caregiver (mostly mothers), and a familiar peer or sibling. Children also asked to identify jealousy from a picture, to provide examples of times they felt jealous, and to offer suggestions for coping with jealousy. Main results revealed that children with autism expressed jealousy in similar situations as their typical age mates, but manifested it in different behaviors. Also, they revealed a less coherent understanding of the feeling. The meaning of the gap between demonstrating and understanding jealousy is discussed in light of the two central theoretical views conceptualizing the core emotional deficit in autism.
S4.3.3
SOCIAL INFORMATION PROCESSING IN CHILDREN WITH AUTISM H. Roeyers, A. Buysse, & K. Ponnet Research Group Developmental Disorders, Ghent University. Ghent, Belgium, B-9000
Research on cognitive schemas (Smith, 1998) has generated paradigms that are useful to shed more light on social information processing in people with autism. An activated schema affects the interpretation of related information. A second effect of an activated schema is to direct attention to both schema-consistent and inconsistent information. Schemas can also influence recall. It is generally assumed that schemas facilitate retrieval of consistent information that was not present in a particular situation. In addition, schema-relevant information is better recalled and recognized than schema-irrelevant information (Baldwin, 1992). In the present study, 36 high-functioning boys with autism, between the ages of 8 and 12, and 36 age- and IQ-matched controls, watched a video in which 2 boys, aged 9 and 10, talk about their leisure activities, family and school. Recognition of consistent, inconsistent and irrelevant information was evaluated by means of a questionnaire. The questionnaire consisted of items that were present in the video (hits) as well as of items that were not present (false alarms). It was hypothesised that the recognition of control children would be biased by their cognitive schemas, i.e more correct recognition of relevant information (both hits and false alarms) than of irrelevant information and more incorrect recognition of consistent than of inconsistent false alarms. Following the central coherence theory, it was predicted that recognition of children with autism would be unbiased: i.e. independent of relevance or consistency of the information. Children with autism were less able than control children to recognize hits and this was the case for all types of information. As for false alarms, there were no significant differences between both groups. As such the results suggest at least some impact of cognitive schemas on information processing in social situationns. A second study, in which level-of-processing task was used, led to similar conclusions.
S4.3.4
A COMPARATIVE STUDY OF FIGURATIVE LANGUAGE AND HUMOUR IN CHILDREN WITH AUTISTIC SPECTRUM DISORDERS G. MacKay & A. Shaw, Department of Educational Support & Guidance, University of Strathclyde, Glasgow, Scotland, G13 1PP.
Difficulties with figurative language and humour have been highlighted by many researchers and people with autism as a core problem in autism. This study evaluated figurative language skills and humour comprehension in able autistic children. A group of autistic children and a group of age matched non-autistic peers were compared using a test of figurative language and humour devised by the authors for the investigation. The test focuses on understanding the meaning of an utterance, and understanding the intentionality behind an utterance. The test incorporates eight types of figurative utterances and two types of verbal jokes. The study shows the discrepancies in understanding between the two groups of children across all parameters investigated. It also highlights some idiosyncrasies and trends specific to the autistic group. The results are discussed in terms of their clinical and theoretical importance. Possible explanations for the results are explored and implications for future research and practical application are proposed.
S4.3.5
INTERMODAL MATCHING OF EMOTIONAL EXPRESSIONS IN YOUNG CHILDREN WITH AUTISM R. Kahana-Kalman* and S. Goldman. Dept. of Pediatrics, Albert Einstein College of Medicine, Bronx, NY, 10461.
Young children with autism spectrum disorders (n=18, mean chronological age = 4 years; 1 mos.) and their age-matched normally developing peers (n=18) participated in a study of the ability to detect intermodal correspondence between facial and vocal information for affect in familiar and unfamiliar expressions. Participants were presented 12 pairs of videotaped facial expressions (happy, sad, and angry) portrayed by their mothers and by an unfamiliar woman. The facial expressions were presented side-by-side on two adjacent TV monitors. The soundtrack, affectively matching one facial expression but not the other was played from a central speaker. The soundtrack was desynchronized with both displays, and thus rhythmic synchrony information was reduced, making it more likely that participants used emotion information to make the match. In a control condition, 8 pairs of inanimate objects (toys) and their sounds were presented. Measures of looking times to the sound-matched versus non-sound matched displays were compared. Results indicated no group differences in intermodal matching in the condition using inanimate objects. As did their normally developing peers, children with autism looked significantly longer to the facial expressions that were accompanied by affectively matching vocal expressions portrayed by their mothers. However, unlike their normally developing peers they did not show preferences for sound-matched emotions of an unfamiliar woman. These results show that children with autism do not have a general inability to detect intermodal correspondences between visual and vocal events, including emotions, but that they were less sensitive than age-matched peers in some conditions. The increased sensitivity of children with autism to familiarity in their recognition of emotional expressions is discussed in terms of implications for early intervention.
SLIDE SESSION 4.4: REPETATIVE BEHAVIOR
S4.4.1
PHENOMENOLOGY OF RESTRICTED REPETITIVE BEHAVIOR IN AUTISM: COMPARISON TO NONSPECIFIC MENTAL RETARDATION J.W. Bodfish, D.E. Parker, J. L Hawkins, & M. H. Lewis UNC Human Development Research Institute, Western Carolina Center, Morganton, NC 28655
In the present study, we compared groups of adults with autism (n = 36) and nonspecific specific mental retardation (n = 36) on a standardized measure of repetitive behavior – the Repetitive Behavior Scale – Revised (RBS-R). The RBS-R is an empirically-derived rating scale for measuring the occurrence and severity of repetitive behaviors. The six subscales of the RBS-R provide measures of the varieties of repetitive behavior seen in individuals with autism – Stereotypy, Self-injury, Compulsions, Rituals, Sameness Behavior, Restricted Behavior. Comparisons of the AUT and MR groups revealed that each type of repetitive behavior occurred frequently in both groups, and no category was uniquely associated with autism. However, the prevalence (% of cases) of each behavior category was significantly higher in the autism group. Within the AUT group, overall repetitive behavior severity was significantly related (r = 0.57) to overall severity of autism. Further, with the exception of self-injury, the addition of each discrete category of repetitive behavior contributed significantly to a multiple regression equation predicting overall autism severity (adjusted ABC score). These results indicate that no single form of abnormal repetition is specific to autism, but that an elevated pattern of occurrence and co-occurrence appears to characterize the disorder. Also, the pattern of co-occurring repetitive behaviors associated with autism appears to involve both lower-order repetitive behaviors (stereotyped movements) and higher-order repetitive behaviors (rituals, sameness behavior).
S4.4.2
ENVIRONMENTAL DETERMINANTS OF SELF-INJURY, STEREOTYPY, AND AGGRESSION. B.A. Iwata, E.M. Roscoe, J. Conners, and B.A. Shore. Psychology Department, University of Florida, Gainesville, FL 32611.
Functional analysis methodology has been used extensively as a clinical-research tool on an individual basis to identify sources of reinforcement for problem behavior, to develop treatment procedures, and to select individuals for inclusion in studies on the effects of specific interventions. By contrast, relatively few studies have applied the methodology across large numbers of individuals presenting with the same problem behavior. This presentation will summarize results from four separate longitudinal studies in which functional analyses were conducted of (a) self-injurious behavior (SIB), (b) noninjurious stereotypic behavior (STPY), (c) hand mouthing (HM, which may or may not be self-injurious), and (d) aggression (AGG). Striking differences were observed in the distribution of behavioral function across responses: AGG was maintained exclusively by social reiforcement, whereas STPY and HM wee maintained almost exclusively by nonsocial (automatic) reinforcement. Finally, SIB was maintianed by multiple sources of control. Factors accounting for these differences, as well as implications for treatment, are noted.
S4.4.3
STRUCTURAL MRI MEASUREMENT OF THE BASAL GANGLIA IN PRESCHOOLERS WITH AUTISM Cody, H., Stephens, K., Gimpel, R., Taylor, D., and Piven, J. Department of Psychiatry, University of North Carolina, Chapel Hill, NC 27599.
The ritualistic, repetitive behaviors characteristic of autism have been associated with the basal ganglia, and specifically linked to the caudate nucleus. This component of the basal ganglia has been correlated with stereotypical behaviors in animal and lesion studies. The basal ganglia have also been implicated in other disorders, such as Obsessive-Compulsive Disorder and Tourette’s Syndrome, that share some of these features (Rosenberg and Keshavan, 1988; Peterson et al., 1993). Sears, et al. (1999) found the caudate to be increased in two independent groups of adolescents and adults with autism. In their study, caudate volume was also significantly correlated with stereotyped, repetitive behaviors on the Autism Diagnostic Interview (ADI-R), but not with the social or communication domains. Specifically, there were correlations between caudate volume and compulsions and rituals, difficulties with minor change in environment and routine, and complex motor behaviors. Increased caudate volume has also been found to correlate with ritualistic-repetitive behaviors in Fragile X (Reiss et al., 1995). Since these behaviors often emerge early in development, we hypothesized that the findings of increased caudate size would be evident in a preschool sample of children with autism. In this study, we compared the size of the caudate, putamen, and globus pallidus in young children with autism (18-35 months) to that of typically developing peers and children with developmental delay. Our findings are discussed in relation to the role that the caudate may play in the stereotyped, repetitive behaviors associated with autism.
S4.4.4
AN ANIMAL MODEL OF RESTRICTED, REPETITIVE BEHAVIOR IN AUTISM. M.H. Lewis, C.A. Turner & M.F. Presti. Dept. of Psychiatry, Univ. of Florida, Gainesville, FL, 32601.
A wide variety of abnormal repetitive behaviors (e.g., stereotypies, compulsions) occur in persons with autism. Although restricted, repetitive patterns of behavior are one of the defining features of this disorder, these behaviors have received much less attention than social and communication deficits. We have characterized an animal model of the repetitive behaviors seen in persons with autism and related developmental disorders. Laboratory reared deer mice exhibit high rates of spontaneous stereotyped behavior that occurs early in development and persists through much of the lifetime of the animal. Early experience in the form of environmental enrichment for 60 days post-weaning was found to markedly reduce vulnerability to develop these behaviors. Brain changes associated with such experiential effects on behavior were indexed using measures of neuronal metabolic activity (cytochrome oxidase histochemistry) and dendritic morphology (spine density). Enriched, stereotypic mice and mice housed in standard lab cages (stereotypic and non-stereotypic) did not differ on either of these measures. Enriched, non-stereotypic mice, however, were found to have higher levels of neuronal metabolic activity and increased dendritic spine density in motor cortex and basal ganglia compared to these groups. Our pharmacological findings have highlighted the importance of striatal glutamate and dopamine in the mediation of stereotyped behavior. Thus, biochemical, morphological and pharmacological findings point to the importance of the cortico-striato-thalamo-cortical circuitry in the development and expression of spontaneous stereotyped behavior in this animal model of repetitive behavior in autism.
S4.4.5
CHROMOSOME 15 AND AUTISM: CLINICAL CHARACTERIZATION OF PHENOTYPE 1Cuccaro M, 1Donnelly S, 1Shao S, 2Ravan S, 2Abramson R, , 1Wolpert C, 1Elston L, 1Wright H, 2Pericak-Vance MA. 1Center For Human Genetics, Duke Univ Med Center, Durham NC, USA 2William S. Hall Psychiatric Institute, Univ of South Carolina, Columbia SC, USA
Autism (AutD) is a complex neurodevelopmental disorder that is genetically and clinically heterogeneous. Chromosomal region 15q11-q13 is a candidate region based on cytogenetic linkage and association findings. Ordered subset analysis (OSA) is an analytic method that identifies a homogenous subset of individuals that contributes to linkage in a particular chromosomal region. Using a factor derived from restricted and repetitive behaviors as the OSA covariate, a subset of 23 AutD families were identified as contributors to linkage on Chr 15 (OSA N=46; 23 sibpairs). We compared these Chr 15 AutD sibpairs with the remaining AutD families that did not show evidence for linkage on composite indices from the Autism Diagnostic Interview-R (ADI-R) and Vineland Adaptive Behavior Scales (VABS). The OSA defined subset was more impaired on a measure of social functioning (VABS Socialization t=2.72, p=0.007)and showed a trend toward significance reflective of lower overall adaptive functioning (Adaptive Behavior Composite t=1.91, p=0.058). The groups did not differ on either the ADI-R or VABS communication indices. These results suggest a greater degree of social impairment in the OSA defined Chr15 AutD group. The results are consistent with the hypothesis that increased repetitive behavior exerts an effect on social and behavioral functioning. Additional efforts to investigate different phenotypic expression in AutD populations for application to genetic analysis will be extremely valuable in delineating the boundaries of AutD.
SATURDAY, NOVEMBER 2, 2002