Biomedical subjects

Warren S Brown

Publications and source records attributed to Warren S Brown.

10 recordsLinked to original sources

PubMed2006

Emotional arousal in agenesis of the corpus callosum.

While the processing of verbal and psychophysiological indices of emotional arousal have been investigated extensively in relation to the left and right cerebral hemispheres, it remains poorly understood how both hemispheres normally function together to generate emotional responses to stimuli. Drawing on a unique sample of nine high-functioning subjects with complete agenesis of the corpus callosum (AgCC), we investigated this issue using standardized emotional visual stimuli. Compared to healthy controls, subjects with AgCC showed a larger variance in their cognitive ratings of valence and arousal, and an insensitivity to the emotion category of the stimuli, especially for negatively-valenced stimuli, and especially for their arousal. Despite their impaired cognitive ratings of arousal, some subjects with AgCC showed large skin-conductance responses, and in general skin-conductance responses discriminated emotion categories and correlated with stimulus arousal ratings. We suggest that largely intact right hemisphere mechanisms can support psychophysiological emotional responses, but that the lack of interhemispheric communication between the hemispheres, perhaps together with dysfunction of the anterior cingulate cortex, interferes with normal verbal ratings of arousal, a mechanism in line with some models of alexithymia.

Adult↗

PubMed2005

Paralinguistic processing in children with callosal agenesis: emergence of neurolinguistic deficits.

Recent research revealed impaired processing of both nonliteral meaning and affective prosody in adults with agenesis of the corpus callosum (ACC) and normal intelligence. Since normal children have incomplete myelination of the corpus callosum, it was hypothesized that paralanguage deficits in children with ACC would be less apparent relative to their peers. The Familiar and Novel Language Comprehension Test (FANL-C) and Prosody Test were given to 18 children with ACC and normal intelligence and 17 controls matched for age (7-13 years), education, and IQ (83-122). When controlling for age, children with ACC were significantly poorer in comprehension of the precise meaning of both literal and nonliteral items on the FANL-C. Adults with ACC had previously been shown to have difficulty only on nonliteral items. The effect size for nonliteral comprehension in children with ACC was smaller than that seen in adults. There was only a trend for the child ACC group to perform worse on the recognition of affective prosody. Thus, while deficits in paralinguistic processing were apparent, children with ACC were not as clearly different from age peers as adults, and were equally deficient at comprehending literal and nonliteral expressions. The differences in results between adults and children with ACC are thought to reflect incomplete callosal development in normal children, and the importance of the corpus callosum in the early stages of the development of the ability to process literal language.

Adolescent↗

PubMed2005

Comprehension of humor in primary agenesis of the corpus callosum.

Individuals with agenesis of the corpus callosum (ACC) can, in some cases, perform normally on standardized intelligence tests. Nevertheless, recent studies suggest that individuals with ACC and normal IQ scores have deficits in domains of fluid and social intelligence. Anecdotal reports from families suggest diminished appreciation of the subtleties of social interactions, and deficits in the comprehension of jokes and stories. In this research, both the cartoon and narrative joke subtests of a humor test (developed by Brownell et al. [Brownell, H., Michel, D., Powelson, J., & Gardner, H. (1983). Surprise but not coherence: sensitivity to verbal humor in right-hemisphere patients. Brain and language, 18(1), 20-27] and Bihrle et al. [Bihrle, A. M., Brownell, H. H., Powelson, J. A., & Gardner, H. (1986). Comprehension of humorous and non-humorous materials by left and right brain-damaged patients. Brain and Cognition, 5(4), 399-411]) were given to 16 adults with complete ACC (all with IQs>80) and 31 controls of similar age and IQ. Individuals with ACC performed worse than controls on the narrative joke subtest (p<.025) when VIQ was controlled. However, on the cartoon subtest the two groups were not significantly different. Covarying age, forms of IQ, narrative memory, set-switching, and literal language comprehension did not substantially alter the group difference. However, covarying comprehension of nonliteral language and proverbs eliminated the difference, suggesting a common origin for the comprehension of jokes, nonliteral language, and proverbs, most likely related to capacity for understanding second-order meanings.

Adolescent↗

PubMed2004

Social processing deficits in agenesis of the corpus callosum: narratives from the Thematic Appreciation Test.

Clinical observations suggest that individuals with agenesis of the corpus callosum (ACC) and normal IQ may have deficits in social intelligence. This study analyzed responses by normally intelligent individuals with ACC to pictures from the Thematic Apperception Test. A rating system was developed to assess three elements of story-generation: story logic, social understanding, and common content. Six individuals with ACC (five complete and one partial; IQs > 85) were compared to eight controls matched for sex, age, and IQ. Based on independent rankings of story protocols by two raters, the five individuals with complete ACC were found to be significantly impaired on all three criteria. The one individual with partial ACC performed better than the majority of controls in all three domains. Results demonstrated that individuals with complete ACC are impaired in understanding socially complex scenes and generating appropriate narratives. Absence of the anterior corpus callosum appears to be important for this deficit.

Adolescent↗

PubMed2004

Bimanual coordination in alcohol-exposed children: role of the corpus callosum.

The corpus callosum (CC) is one of several brain structures affected in children prenatally exposed to alcohol. This structure plays a major role in coordinating motor activity from opposite sides of the body, and deficits in bimanual coordination have been documented in individuals with agenesis of or damage to the CC, particularly when the task is performed without visual feedback. The Bimanual Coordination Test was used to assess speed and accuracy on a task where both hands must coordinate to guide a cursor through angled pathways providing measures of interhemispheric interaction or the ability of the two hemispheres to coordinate activity via the corpus callosum. Twenty-one children with fetal alcohol spectrum disorders (FASD) and 17 non-exposed control children (CON), matched closely in age, sex, and ethnicity were tested. For trials with visual feedback (WV), children with FASD were slower than CON children but were equally accurate. Although statistically significant group differences were not observed on most trials completed without visual feedback (WOV), accuracy of the FASD group on WOV trials was highly variable. Group differences in accuracy on WOV angles approached significance after accounting for performance on the WV angles, and children with FASD were significantly less accurate on an individual angle believed to be particularly sensitive to interhemispheric interaction. These results indicate that children with FASD are slower than CON children but equally accurate on basic visuomotor tasks. However, as task complexity and reliance on interhemispheric interaction increases, children with FASD demonstrate variable and inaccurate performance.

Adolescent↗

PubMed2004

Neural substrates of emotion as revealed by functional magnetic resonance imaging.

OBJECTIVES: To examine the brain circuitry involved in emotional experience and determine whether the cerebral hemispheres are specialized for positive and negative emotional experience. BACKGROUND: Recent research has provided a preliminary sketch of the neurologic underpinnings of emotional processing involving specialized contributions of limbic and cortical brain regions. Electrophysiologic, functional imaging, and Wada test data have suggested positive, approach-related emotions are associated with left cerebral hemisphere regions, whereas negative, withdrawal-related emotions appear to be more aligned with right hemisphere mechanisms. METHOD: These emotional-neural associations were investigated using functional magnetic resonance imaging in 10 healthy controls with 20 positively and 20 negatively valenced pictures from the International Affective Picture System in a counterbalanced order. Pictures were viewed within a 1.5 Telsa scanner through computerized video goggles. RESULTS: Emotional pictures resulted in significantly increased blood flow bilaterally in the mesial frontal lobe/anterior cingulate gyrus, dorsolateral frontal lobe, amygdala/anterior temporal regions, and cerebellum. Negative emotional pictures resulted in greater activation of the right hemisphere, and positive pictures caused greater activation of the left hemisphere. CONCLUSIONS: Results are consistent with theories emphasizing the importance of circuitry linking subcortical structures with mesial temporal, anterior cingulate, and frontal lobe regions in emotion and with the valence model of emotion that posits lateralized cerebral specialization for positive and negative emotional experience.

Adult↗

PubMed2003

Communicative deficits in agenesis of the corpus callosum: nonliteral language and affective prosody.

While some individuals with agenesis of the corpus callosum can perform normally on standardized intelligence tests, clinical observations suggest that they nevertheless have deficits in the domains of fluid and social intelligence. Particularly important for social competence is adequate understanding and use of paralinguistic information. This study examined the impact of callosal absence on the processing of pragmatic and paralinguistic information. Young adult males with agenesis of the corpus callosum (ACC) were evaluated in the areas of nonliteral language comprehension, proverb recognition and interpretation, and perception of affective prosody. Ten ACC individuals with normal Wechsler IQ were compared to 14 sex, age, and IQ matched normal controls. The Formulaic and Novel Language Comprehension Test (FANL-C), Gorham Proverbs Test, and LA Prosody Test were administered. ACC subjects exhibited significant impairment on the nonliteral items of the FANL-C, but no significant difference from controls in comprehension of literal items. ACC subjects also exhibited significant deficits in both self-generated interpretation and recognition of proverb meaning, and in recognition of affective prosody. These results demonstrate that normally intelligent individuals with ACC are impaired in the understanding of nonliteral language and emotional-prosodic cues that are important in social communication. In all three tests, the performance of individuals with ACC was similar to patients with right hemisphere brain damage. Thus, persons with ACC appear to lack interhemispheric integration of critical aspects of language processed by the right hemisphere.

Adolescent↗

PubMed2003

Normal development of bimanual coordination: visuomotor and interhemispheric contributions.

The corpus callosum is one of the last cortical pathways to develop, continuing to myelinate through the end of the first decade of life. However, the functional consequences of this late development are not entirely known. The importance of callosal development for bimanual motor coordination is suggested by the fact that bimanual coordination in younger children is similar to that of persons with commissurotomy or callosal agenesis. This study focused on the development of bimanual coordination in 67 normally developing children between 6 and 15 years of age using the computerized Bimanual Coordination Test (cBCT). Results indicated that right- and left-hand unimanual motor speed was significantly correlated with age (r = -.26 and -.44, respectively). Age was also significantly associated with accuracy of performance on trials demanding both symmetric (r = -.46) and asymmetric (r = -.50) bi-manual responding. The correlation with asymmetric bimanual responding (requiring greater interhand coordination) remained significant when covarying performance on symmetric response trials. Accuracy on asymmetric bimanual trials requiring greater left- than right-hand speed accounted for the largest portion of this unique, age-related variance. Thus, cBCT performance reveals child development in motor speed and visuomotor processing, as well as the unique contributions of interhemispheric interactions to bimanually coordinated motor activity.

Adolescent↗

PubMed2002

Callosal function in multiple sclerosis: bimanual motor coordination.

Evidence of callosal dysfunction in patients with multiple sclerosis (MS) was examined using a test of bimanual coordination. MS patients were slower than non-patients on the Bimanual Coordination Test (BCT) on both unimanual trials (simple motor speed) and bimanual trials (intermanual coordination). Further, when compared to normals, MS patients exhibited a substantially greater difference between bimanual and unimanual response time, suggesting a deficit in interhemispheric motor interactions. A subgroup of MS subjects who showed markedly inefficient callosal transmission had previously been identified on the basis of abnormal evoked potentials (low amplitude cross-callosal evoked potentials). In comparisons of MS subgroups, the deficit in bimanual motor coordination was found only in MS patients with EP evidence of inefficient callosal transmission. These data support the conclusion that deficits in bimanual motor coordination occur in MS and that these deficits are related to callosal dysfunction.

Adult↗

PubMed2002

Spatial attention in agenesis of the corpus callosum: shifting attention between visual fields.

The role of the corpus callosum in spatially selective visual attention is uncertain. Research using commissurotomy and callosotomy patients has attempted to determine if the corpus callosum plays a role in reorienting attention between visual fields, as if spatial attention is unitary or divisible between the cerebral hemispheres. Reorienting of selective visuospatial attention within versus between visual fields was tested in 10 individuals with agenesis of the corpus callosum (ACC) and nine matched controls. Spatially focused attention to the most likely location of target appearance was created using both peripheral sensory cues and central symbolic cues in separate tests. Results demonstrated that individuals with ACC have significantly greater difficulty reorienting attention to an invalidly cued target stimulus occurring in the opposite visual field. However, this effect did not interact with the type of cueing (sensory or symbolic). Individuals with ACC did not differ from controls either with respect to the laterality of within-field reorientation of attention, or with respect to the most efficient direction of between-field shifting of attention. Since congenital absence of the corpus callosum significantly reduces efficiency in the reorienting of attention between visual fields, spatial attention cannot be completely unified based on a subcortical mechanism and the mobilization of attentional resources within each hemisphere must depend on callosal processes.

Adult↗