AS vs Autism Neuroimaging

Arch Gen Psychiatry. 2004 Mar;61(3):291-8.  Investigation of neuroanatomical differences between autism and Asperger syndrome.

Lotspeich LJ, Kwon H, Schumann CM, Fryer SL, Goodlin-Jones BL, Buonocore MH, Lammers CR, Amaral DG, Reiss AL.

Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305, USA.

Linda.Lotspeich@stanford.edu

CONCLUSIONS: Lack of replication between previous autism MRI studies could be due to intersite differences in MRI systems and subjects' age and IQ. Cerebral gray tissue findings suggest that ASP is on the mild end of the autism spectrum. However, exploratory assessments of brain-IQ relationships reveal differences between HFA and ASP, indicating that these conditions may be neurodevelopmentally different when patterns of multiple measures are examined. Further investigations of brain-behavior relationships are indicated to confirm these findings.

Functional connectivity in an fMRI working memory task in high-functioning autism.

Neuroimage. 2005 Feb 1;24(3):810-21. Epub 2004 Nov 24.

Koshino H, Carpenter PA, Minshew NJ, Cherkassky VL, Keller TA, Just MA.

Center for Cognitive Brain Imaging, Carnegie Mellon University, Pittsburgh, PA 15213, USA; Department of Psychology, California State University, San Bernardino, CA 92407, USA.

An fMRI study was used to measure the brain activation of a group of adults with high-functioning autism compared to a Full Scale and Verbal IQ and age-matched control group during an n-back working memory task with letters. The behavioral results showed comparable performance, but the fMRI results suggested that the normal controls might use verbal codes to perform the task, while the adults with autism might use visual codes. The control group demonstrated more activation in the left than the right parietal regions, whereas the autism group showed more right lateralized activation in the prefrontal and parietal regions. The autism group also had more activation than the control group in the posterior regions including inferior temporal and occipital regions. The analysis of functional connectivity yielded similar patterns for the two groups with different hemispheric correlations. The temporal profile of the activity in the prefrontal regions was more correlated with the left parietal regions for the control group, whereas it was more correlated with the right parietal regions for the autism group.

Semin Pediatr Neurol. 2004 Sep;11(3):205-13.

Imaging data in autism: from structure to malfunction.

Acosta MT, Pearl PL.

Department of Neurology, Children's National Medical Center, The George Washington University School of Medicine and Health Sciences, Washington, DC 20010-2970, USA. macosta@cnmc.org

During the last two decades, neuroimaging studies have improved our knowledge of brain development and contributed to our understanding of disorders involving the developing brain. Differences in cerebral anatomy have been determined in autism spectrum disorder (ASD). Morphological studies by magnetic resonance imaging have provided evidence of structural differences in ASD compared with the normal population. This has enhanced our view of autism as a neurobiological disorder corresponding with different stages and events in brain development. Alterations in volume of the total brain and specifically the cerebellum, frontal lobe, and limbic system have been identified. There appears to be a pattern of increased and then decreased rate of brain growth over time. We integrate these observations with neurobehavioral findings to provide a developmental hypothesis of the pathophysiology of autism.

Dev Med Child Neurol. 2004 Nov;46(11):760-4.

Voxel-based morphometry elucidates structural neuroanatomy of high-functioning autism and Asperger syndrome.

Kwon H, Ow AW, Pedatella KE, Lotspeich LJ, Reiss AL.

Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California, USA. howerk@alum.mit.edu

Efforts to examine the structural neuroanatomy of autism by using traditional methods of imaging analysis have led to variable findings, often based on methodological differences in image acquisition and analysis. A voxel-based computational method of whole-brain anatomy allows examination of small patterns of tissue differences between groups. High-resolution structural magnetic resonance images were acquired for nine males with high-functioning autism (HFA; mean age 14y [SD3y 4mo]), 11 with Asperger syndrome (ASP; mean age 13y 6mo [SD2y 5mo]), and 13 comparison (COM) participants (mean age 13y 7mo [SD 3y 1mo]). Using statistical parametric mapping, we examined contrasts of gray matter differences between the groups. Males with HFA and ASP had a pattern of decreased gray matter density in the ventromedial regions of the temporal cortex in comparison with males from an age-matched comparison group. Examining contrasts revealed that the COM group had increased gray matter density compared with the ASP or combined HFA and ASP group in the right inferior temporal gyrus, entorhinal cortex, and rostral fusiform gyrus. The ASP group had less gray matter density in the body of the cingulate gyrus in comparison with either the COM or HFA group. The findings of decreased gray matter density in ventromedial aspects of the temporal cortex in individuals with HFA and ASP lends support to theories suggesting an involvement of these areas in the pathophysiology of autism, particularly in the integration of visual stimuli and affective information.

PMID: 15540637 [PubMed - indexed for MEDLINE]

Hippocampus and amygdala volumes in parents of children with autistic disorder.

Am J Psychiatry. 2004 Nov;161(11):2038-44.

Rojas DC, Smith JA, Benkers TL, Camou SL, Reite ML, Rogers SJ.

Department of Psychiatry, University of Colorado Health Sciences Center, Box C268-68 CPH, 4200 E. 9th Ave., Denver, CO 80262, USA. Don.Rojas@uchsc.edu

OBJECTIVE: Structural and functional abnormalities in the medial temporal lobe, particularly the hippocampus and amygdala, have been described in people with autism. The authors hypothesized that parents of children with a diagnosis of autistic disorder would show similar changes in these structures. METHOD: Magnetic resonance imaging scans were performed in 17 biological parents of children with a diagnosis of DSM-IV autistic disorder. The scans were compared with scans from 15 adults with autistic disorder and 17 age-matched comparison subjects with no personal or familial history of autism. The volumes of the hippocampus, amygdala, and total brain were measured in all participants. RESULTS: The volume of the left hippocampus was larger in both the parents of children with autistic disorder and the adults with autistic disorder, relative to the comparison subjects. The hippocampus was significantly larger in the adults with autistic disorder than in the parents of children with autistic disorder. The left amygdala was smaller in the adults with autistic disorder, relative to the other two groups. No differences in total brain volume were observed between the three groups. CONCLUSIONS: The finding of larger hippocampal volume in autism is suggestive of abnormal early neurodevelopmental processes but is partly consistent with only one prior study and contradicts the findings of several others. The finding of larger hippocampal volume for the parental group suggests a potential genetic basis for hippocampal abnormalities in autism.

PMID: 15514404 [PubMed - indexed for MEDLINE]

Cerebellar function in autism: functional magnetic resonance image activation during a simple motor task.
Biol Psychiatry. 2004 Aug 15;56(4):269-78.
Allen G, Muller RA, Courchesne E.

Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, Texas, USA.

BACKGROUND: The cerebellum is one of the most consistent sites of neuroanatomic abnormality in autism, yet it is still unclear how such pathology impacts cerebellar function. In normal subjects, we previously demonstrated with functional magnetic resonance imaging (fMRI) a dissociation between cerebellar regions involved in attention and those involved in a simple motor task, with motor activation localized to the anterior cerebellum ipsilateral to the moving hand. The purpose of the present investigation was to examine activation in the cerebella of autistic patients and normal control subjects performing this motor task. METHODS: We studied eight autistic patients and eight matched normal subjects, using fMRI. An anatomic region-of-interest approach was used, allowing a detailed examination of cerebellar function. RESULTS: Autistic individuals showed significantly increased motor activation in the ipsilateral anterior cerebellar hemisphere relative to normal subjects, in addition to atypical activation in contralateral and posterior cerebellar regions. Moreover, increased activation was correlated with the degree of cerebellar structural abnormality. CONCLUSIONS: These findings strongly suggest dysfunction of the autistic cerebellum that is a reflection of cerebellar anatomic abnormality. This neurofunctional deficit might be a key contributor to the development of certain diagnostic features of autism (e.g., impaired communication and social interaction, restricted interests, and stereotyped behaviors).

Less white matter concentration in autism: 2D voxel-based morphometry.

Neuroimage. 2004 Sep;23(1):242-51.
Chung MK, Dalton KM, Alexander AL, Davidson RJ.
Department of Statistics, University of Wisconsin-Madison, Madison, WI 53706, USA.
mchung@stat.wisc.ed

Autism is a neurodevelopmental disorder affecting behavioral and social cognition, but there is little understanding about the link between the functional deficit and its underlying neuroanatomy. We applied a 2D version of voxel-based morphometry (VBM) in differentiating the white matter concentration of the corpus callosum for the group of 16 high functioning autistic and 12 normal subjects. Using the white matter density as an index for neural connectivity, autism is shown to exhibit less white matter concentration in the region of the genu, rostrum, and splenium removing the effect of age based on the general linear model (GLM) framework. Further, it is shown that the less white matter concentration in the corpus callosum in autism is due to hypoplasia rather than atrophy.

Author: 
Various Authors
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