Interhemispheric interaction during childhood: I. Neurologically intact children.
ABSTRACT This study examined the development of interaction between the hemispheres as a function of computational complexity (Banich & Belger, 1990; Belger & Banich, 1992) in 24 children aged 6.5 to 14 years. Participants performed 2 tasks: a less complex physical-identity task and a more complex name-identity task. Children, like adults, exhibit an across-hemisphere advantage on the computationally more complex name-identity task, and neither a within-nor an across-hemisphere advantage for the computationally less complex physical-identity task. Correlations indicated that the younger the child, (a) the greater the size of the within-hemisphere advantage on the less complex task, (b) the greater the size of the across-hemisphere advantage on the more complex task, and (c) the poorer the ability to ignore attentionally distracting information in a selective attention paradigm. These results suggest that interhemispheric interaction in children, like that in adults, serves to deal with the heightened processing demands imposed by increased computational complexity.
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ABSTRACT: The present study investigated whether dividing information between the hemispheres becomes more advantageous to task performance as computational complexity increases. We hypothesized that interhemispheric processing would benefit performance especially for computationally complex tasks, whereas it would hinder performance for relatively simple ones. A letter-matching task was given to 23 subjects at three levels of computational complexity. Complexity was varied either by increasing the number of inputs to be processed or by the nature of the decision to be made. The results indicated that each of these manipulations of complexity influenced performance by making it more advantageous to have both hemispheres involved in processing rather than just one. Furthermore, the effects of each manipulation were separable.Neuropsychologia 11/1992; 30(10):923-9. · 3.48 Impact Factor
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ABSTRACT: The role of the corpus callosum versus other cerebral commissures in the interhemispheric integration of visual information was studied in four individuals with complete agenesis of the corpus callosum, two individuals with partial agenesis, one total commissurotomy patient, and normal individuals. Evoked potential (EP) indices of interhemispheric transmission of visual sensory responses were observed during matching of unilateral and bilateral visual field letters and patterns. Neither the commissurotomy nor any of the acallosal patients had ipsilateral hemisphere visual EPs (P1 and N1), demonstrating that the posterior callosum is necessary for interhemispheric transmission of these components of visual evoked potentials. While the commissurotomy patient could not compare bilaterally presented letters, the anterior commissure of the acallosal patients appeared to be sufficient for interhemispheric comparison of single letters. However, bilateral comparison of more complex visual patterns resulted in considerable difficulty for complete agenesis patients, while comparison of patterns was more nearly normal when anterior callosal fibers were present (partial agenesis).Neuropsychologia 10/1999; 37(10):1165-80. · 3.48 Impact Factor
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ABSTRACT: The present studies investigated how dividing processing between the hemispheres affects task performance. In particular, they examined whether dividing processing between the hemispheres leads to a performance advantage only when task demands exceed a certain threshold. In Experiment 1 processing demands were manipulated by varying the difficulty of the decision process. In the more difficult task, subjects decided as quickly as possible whether two of three letters had the same name (e.g. A a), whereas in the less difficult task they simply decided whether two of the three were physically identical (e.g. A A). As expected, dividing processing between the hemispheres aided performance for the more difficult name-identity task whereas it actually hindered performance for easier physical-identity task. In Experiment 2, subjects made a physical-identity decision about a different stimulus, digits. The pattern of results found in Experiment 1 for the physical-identity task was replicated; interhemispheric processing hindered task performance. These results indicate that the physical characteristics of a stimulus have minimal influence on the extent to which interhemispheric processing aids task performance. In Experiment 3, subjects were required to make more difficult decisions about digits. In one task, they decided whether the sum of two of the three digits was greater than or equal to 10, and in the other they decided if the value of a particular digit was less than either of the other two. Dividing processing between the hemispheres led to faster performance for both tasks, similar to the results for the name-identity condition. In sum, these experiments suggest that when task requirements are demanding, performance is enhanced by distributing processing across the hemispheres.Cortex 04/1990; 26(1):77-94. · 6.16 Impact Factor