Defining the broader phenotype of autism: genetic, brain, and behavioral perspectives

Achieving progress in understanding the cause, nature, and treatment of autism requires an integration of concepts, approaches, and empirical findings from genetic, cognitive neuroscience, animal, and clinical studies. The need for such integration has been a fundamental tenet of the discipline of developmental psychopathology from its inception. It is likely that the discovery of autism susceptibility genes will depend on the development of dimensional measures of broader phenotype autism traits. It is argued that knowledge of the cognitive neuroscience of social and language behavior will provide a useful framework for defining such measures. In this article, the current state of knowledge of the cognitive neuroscience of social and language impairments in autism is reviewed. Following from this, six candidate broader phenotype autism traits are proposed: (a) face processing, including structural encoding of facial features and face movements, such as eye gaze; (b) social affiliation or sensitivity to social reward, pertaining to the social motivational impairments found in autism; (c) motor imitation ability, particularly imitation of body actions; (d) memory, specifically those aspects of memory mediated by the medial temporal lobe-prefrontal circuits; (e) executive function, especially planning and flexibility; and (f) Language ability, particularly those aspects of language that overlap with specific language impairment, namely, phonological processing.

MRI findings differentiate between late-onset schizophrenia and late-life mood disorder

OBJECTIVES

Compare MRI scans of patients with late-onset schizophrenia, late-life depression and late-life bipolar disorder to age- and gender-matched controls. MRI head scans of 14 patients in each diagnostic group and 21 patients in the normal control group were compared. Subjects were recruited from inpatient and outpatient services.

MEASURES

The CERAD MRI rating algorithm was used to rate degree of atrophy.

RESULTS

Patients with bipolar and unipolar disorder had greater left sylvian fissure and left and right temporal sulcal enlargement, and more bilateral cortical atrophy than normals. Patients with late-onset schizophrenia had larger right temporal horns and larger third ventricles. These findings validate the distinctions between late-life affective disorder and late-onset schizophrenia and mirror changes reported in younger individuals. They may reflect underlying structural and functional abnormalities found in neuropathologic and functional imaging studies.

The use of herbal alternative medicines in neuropsychiatry. A report of the ANPA Committee on Research

Growing numbers of people throughout the United States (40% in 1998) are using various forms of alternative therapies. A MEDLINE literature search of journals from the past three decades and an Internet database query were performed to determine the types and frequency of alternative therapies used, with special attention given to the herbal medicines used in neuropsychiatric disorders. Clinical effects, mechanisms of action, interactions, and adverse reactions of the herbal treatments are detailed. Objective controlled trials will be needed to establish safety and efficacy of herbal supplements. Knowledge of the properties of these therapies can improve the care of neuropsychiatric patients.

Sex differences in inferior parietal lobule volume in schizophrenia

OBJECTIVE

The inferior parietal lobule is a heteromodal association cortical region that has been implicated in the pathophysiology of schizophrenia. Inferior parietal lobule gray matter volumes have been shown to differ between healthy male and female subjects, with male subjects having larger left volumes. The authors sought to determine whether these volumetric sex differences also exist in patients with schizophrenia.

METHOD

The authors used magnetic resonance imaging to measure inferior parietal lobule volumes of 15 pairs of male and female schizophrenic subjects who were individually matched to each other and to 15 pairs of healthy male and female subjects.

RESULTS

Male schizophrenic patients exhibited a reversal of the normal left-greater-than-right male asymmetry in this region and had left inferior parietal lobule gray matter volumes that were significantly smaller than those of healthy male subjects. Female schizophrenic patients did not differ significantly from healthy female subjects in left or right inferior parietal lobule volume or in asymmetry.

CONCLUSIONS

This study provides further evidence of brain morphology sex differences in schizophrenia that possibly contribute to the differential clinical disease expression in men and women.

Sex differences in the inferior parietal lobule

The inferior parietal lobule (IPL) - a neocortical region and part of the heteromodal association cortex (HASC) - has been hypothesized to exhibit sexual dimorphism, as do other HASC regions, particularly with regard to asymmetry. Using a reliable method for measuring IPL gray matter volume based upon individual sulcal-gyral landmarks, we measured this region on magnetic resonance imaging scans from a sample of 15 individually matched pairs of normal male and female subjects. Male subjects showed significantly larger left, but not right, IPL volumes when compared to females. Males also showed a leftward (left > right) asymmetry for the IPL, with a less marked opposite asymmetry in females. Such sexual dimorphisms may possibly underlie the subtle cognitive differences observed between the sexes.

When does Huntington's disease begin?

Recent studies have detected basal ganglia atrophy in clinically asymptomatic persons with the genetic mutation that causes Huntington's disease (HD). Whether reductions in caudate and putamen volume on MRI scans are associated with changes in cognitive and neurologic functioning was examined in 13 healthy adults with the IT-15 mutation. Reduced striatal volume was found to correlate with greater neurologic (largely motor) impairment, slower mental processing speed, and poorer verbal learning, although none of the participants met even liberal criteria for clinical diagnosis of HD. These correlations are strikingly similar to those observed in symptomatic HD patients, possibly reflecting the earliest manifestations of disease.

Mesial temporal lobe measurements on magnetic resonance imaging scans

Changes in the mesial temporal lobe, particularly in the hippocampus, amygdala, and entorhinal cortex, are reported to occur in several neuropsychiatric conditions. Neuroimaging provides a non-invasive means of studying these changes. We present a method for reliably measuring the hippocampus, amygdala, and entorhinal cortex on MRI. The advantages of our method include high reliability, the use of orthogonal views in delineating boundaries and circumscription of measurement such that no tissue of any one anatomic structure is included in the measurement of another structure.

Small planum temporale volume in Down's syndrome: a volumetric MRI study

OBJECTIVE

Down's syndrome is associated with structural brain abnormalities and language deficits. The aim of this study was to investigate whether the superior temporal gyrus and the planum temporale, both parts of the anatomic substrate for language, are abnormal in Down's syndrome.

METHOD

The authors examined volumetric magnetic resonance imaging (MRI) measures of the superior temporal gyrus and the planum temporale for 17 community-dwelling patients with Down's syndrome and 17 matched healthy comparison subjects. For the subjects with Down's syndrome, the correlations of the superior temporal gyrus and planum temporale volumes with performance on tests of language function were examined.

RESULTS

The planum temporale volume of the patients with Down's syndrome was smaller than that of the healthy subjects, even after differences in whole brain volume were controlled for. The volume of the superior temporal gyrus in the Down's syndrome patients was proportionally similar to that of the comparison group. For the subjects with Down's syndrome, neither superior temporal gyrus nor planum temporale volume was significantly correlated with performance on language tests after total brain volume was controlled for.

CONCLUSIONS

In Down's syndrome, planum temporale volume may be selectively smaller than normal, although the effect of this volume deficit on language is not clear.

Exploratory factor analysis of MRI brain structure measures in schizophrenia

Much of the literature shows various regional structural brain abnormalities in schizophrenia, but the complexity and variability of brain makes it difficult to determine how these regions are related. Statistical methods which estimate factors underlying patterns of covariance have not been widely used, but could be useful for analyzing such complex data. We applied exploratory and confirmatory factor analysis procedures to specific cortical and subcortical regional brain volume measures from MRI data in 60 normal and 44 schizophrenic subjects. Basal ganglia, heteromodal cortical gray, and medial temporal lobe factors were present in both the normal and the schizophrenia groups. The factor structure observed in the normal group showed a high degree of bilateral symmetry which is present but disrupted in the schizophrenia group. In the bilateral data, the disruption is most pronounced with medial and lateral temporal lobe structures including entorhinal cortex and anterior and posterior superior temporal gyri. There was a significant correlation between the basal ganglia factor and the heteromodal cortical gray factor in the normal group that was not present in the schizophrenia group. In the unilateral data, left posterior superior temporal gyrus did not load onto any factor in the schizophrenia group. Confirmatory factor analyses showed significant differences between the two groups in factor structure. A number of specific brain regions are affected in schizophrenia, and structural relationships between groups of regions also are abnormal. The results suggest that heteromodal dorsolateral prefrontal and superior temporal cortical gray regions are structurally related, whereas inferior parietal cortical gray is less so. These results should be viewed as preliminary as the ratio of parameters to subjects was relatively low, and replication is needed. However, the results demonstrate the potential utility of latent structure methods such as factor analysis in study of complex relationships in neuropsychiatric data.

Cingulate gyrus in schizophrenic patients and normal volunteers

Comparable magnetic resonance imaging (MRI) sections of right and left anterior and posterior cingulate gyrus were measured blindly with a method developed by the authors in 14 patients with schizophrenia (by DSM-III-R criteria) and 14 normal volunteers individually matched to the patients for age, sex, education, and parental socioeconomic status. Interrater reliability met or exceeded 0.92 (k) on all cingulate structures measured. Brain volume in the two groups differed by 2% (normal > schizophrenia), but the difference was not significant. All cingulate gyri measures were nonsignificantly smaller in the patient group by 3-5%. There was an inverse correlation between left anterior cingulate size and severity of hallucinations that was, however, not significant after Bonferroni correction. Lateral asymmetry of the cingulate regions measured was the same in both groups, with the left being nonsignificantly smaller than the right for all regions. We demonstrate a reliable method, unreported thus far in the literature, to measure the cingulate gyrus on MRI; the results suggest that left cingulate gyrus size may be inversely related to severity of hallucinations in schizophrenia.

Regional brain atrophy in HIV-1 infection: association with specific neuropsychological test performance

Quantified magnetic resonance imaging (MRI) was related to neuropsychological (NP) test scores in an asymptomatic HIV-1 seropositive group, a non-demented AIDS/ARC group, a group of subjects with HIV-1 dementia, and a seronegative control group. The MRIs were quantified using three planimetric measures of brain structure: the bicaudate ratio (a measure of caudate region atrophy), the bifrontal ratio (a measure of frontal region atrophy), and the ventricle to brain ratio (a measure of overall cerebral atrophy). Cognitive performance was assessed with standard NP tests. Significant correlations between the MRI ratios and many of the NP tests were observed. Of the tests grooved pegboard, part B of the trail making test, the verbal fluency test, and the digit span forward were associated with MRI abnormalities. The bicaudate ratio was most closely associated with the NP tests. These findings indicate that ventricular enlargement, especially in the region of the caudate, is closely related to poor NP test performance in HIV-1 infection.

Patterns of cerebral atrophy in HIV-1-infected individuals: results of a quantitative MRI analysis

Cerebral atrophy is a common radiologic manifestation of HIV dementia. To evaluate the relationship between cognitive impairment and cerebral atrophy, adjusting for age and immune status, we used standardized planimetry to measure the ventricle-brain ratio (VBR) and the bifrontal (BFR) and bicaudate (BCR) ratios, three measures of cerebral atrophy. We analyzed cranial MRIs of 23 HIV-1-seronegative controls (SN) and 116 HIV-1-infected individuals. Of the HIV-1-seropositive individuals, 37 had HIV dementia (DM group), 40 had neurologic or neuropsychological abnormalities insufficient for HIV dementia (NP+ group), and 39 were neurologically normal (NML group). We performed comparisons using analysis of covariance with correction for multiple comparisons. Both the VBR, a general measure of overall cerebral atrophy, and the BCR, a measure of atrophy in the region of the caudate nucleus, are significantly associated with dementia. The association is stronger for BCR enlargement than for VBR enlargement, suggesting that selective caudate region atrophy is associated with HIV dementia. These results indicate that overall cerebral atrophy and prominent caudate region atrophy are important radiographic features of HIV dementia.

Sylvian fissure size in schizophrenia measured with the magnetic resonance imaging rating protocol of the Consortium to Establish a Registry for Alzheimer's Disease

OBJECTIVE

Since previous work indicated smaller than normal temporal lobe structures in schizophrenic patients, the authors tested the hypothesis that this abnormality might be reflected in abnormally large sylvian fissures.

METHOD

The subjects were 48 schizophrenic patients and 51 normal comparison subjects matched groupwise with regard to age and sex. CSF spaces (sylvian fissures, temporal lobe sulci, temporal horns, third ventricle, lateral ventricles, and superficial cerebral sulci) were visually assessed with the magnetic resonance imaging rating protocol of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD).

RESULTS

The sylvian fissures of the schizophrenic patients were found to be bilaterally wider than those of the comparison subjects. There were no other significant differences.

CONCLUSIONS

Schizophrenic patients appear to have larger than normal sylvian fissures, which may reflect smaller superior temporal gyri.

Cortical magnetic resonance imaging changes in elderly inpatients with major depression

OBJECTIVE

The purpose of the study was to determine if magnetic resonance imaging (MRI) scans of elderly depressed patients differ from MRI scans of age-matched control subjects and age-matched patients with Alzheimer's disease.

METHOD

The authors studied 21 patients 60 years or older with major depression, 16 patients with Alzheimer's disease, and 14 age-matched control subjects.

RESULTS

Compared to control subjects, depressed patients had greater cerebral sulcal and temporal sulcal atrophy; larger sylvian fissures, lateral ventricles, third ventricles, and temporal horns; and greater severity of subcortical white matter lesions. Depressed patients also had more basal ganglia lesions but similar levels of periventricular hyperintensity. There were no differences between depressed patients with and without delusions on any MRI measure. Depressed patients who received ECT had more temporal horn atrophy and greater subcortical abnormality summary scores than normal subjects. Cortical sulcal atrophy correlated with age at onset of depression.

CONCLUSIONS

The findings suggest that elderly hospitalized depressed patients have greater cortical as well as subcortical atrophy and more basal ganglia lesions than age-matched normal control subjects. The correlation of these abnormalities with outcome remains unknown.

Neuroanatomy of fragile X syndrome: the posterior fossa

The occurrence and specificity of posterior fossa abnormalities as measured from magnetic resonance images of the brain were investigated in a group of 14 males with fragile X syndrome and comparison groups consisting of 17 males with other causes of developmental disability and 18 males with normal IQs. The size of the posterior cerebellar vermis was significantly decreased and the fourth ventricle significantly increased in the group of males with fragile X syndrome compared with males in both comparison groups. These neuroanatomical abnormalities appeared to be secondary to hypoplasia rather than atrophy.

Intelligence in schizophrenia: meta-analysis of the research

This article combines a review and meta-analysis of research on IQ in schizophrenia, with emphasis on areas of convergence in the findings, as well as questions that remain to be answered. Taken together, the findings suggest that early-onset and adult-onset schizophrenia are associated with intellectual deficits across the lifespan. Preschizophrenic children, adolescents, and young adults perform below matched controls on a variety of standardized measures of intelligence. Significant IQ deficits are also apparent after the onset of the disorder. Moreover, IQ is positively related to several indices of prognosis, and, among hospitalized patients, there is negative within-subject covariance between intellectual performance and symptom severity. Although there is fairly consistent evidence that Verbal IQ is higher than Performance IQ among schizophrenic patients, a more specific pattern of subtest performance is not apparent. A central question raised by the results is whether IQ is an independently determined factor that can serve to mitigate the vulnerability of individuals who are constitutionally predisposed to schizophrenia, or whether intellectual deficit is one manifestation of the constitutional predisposition to the disorder. The findings also raise the question of possible sex differences in the developmental determinants of schizophrenia: Meta-analyses revealed that premorbid IQ deficits are more prevalent among males than females.