[show abstract][hide abstract] ABSTRACT: The present study investigated whether dividing critical information across the hemispheres in the auditory and tactile modalities aids performance more for computationally complex rather than computationally simpler task-a pattern previously observed in the visual modality [Cortex 26 (1990) 77; Neuropsychology 12 (1998) 380; Neuropsychologia 30 (1992) 923]. We conducted two experiments, one in the auditory and one in the tactile modality, that were analogous to those previously performed in the visual modality. In agreement with previous findings, for both modalities we observed that the performance advantage exhibited for within-hemisphere processing in the computationally simpler condition (that required fewer steps to reach a decision) was diminished in the computationally more complex condition. In the auditory experiment we also manipulated computational complexity by varying the amount of time available for processing information. The within-hemisphere advantage in performance was also significantly reduced when complexity was increased through temporal manipulations. These findings suggest that the brain may use interhemispheric interaction as a general strategy to increase computational resources, independent of sensory modality and the manner in which computational demands are increased.
[show abstract][hide abstract] 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.
[show abstract][hide abstract] ABSTRACT: This study examined whether children with early-treated phenylketonuria (ETPKU) exhibited a disruption in communication between the hemispheres as a function of computational complexity (Banich & Belger, 1990; Belger & Banich, 1992, 1998) when compared to neurologically uncompromised children who were matched in age and IQ. This investigation was motivated by findings that phenylketonuria affects myelination of neurons, including those that make up the corpus callosum, the main neural conduit for interhemispheric interaction. Children performed 2 tasks: a less complex physical-identity task and a more complex name-identity task. For both tasks, we compared performance on across-hemisphere trials, which require interhemispheric interaction, and on within-hemisphere trials, in which no hemispheric interaction is required. On the more complex name-identity task, children with ETPKU exhibited less of a benefit from across-hemisphere processing than did neurologically intact children. These results suggest that the interhemispheric interaction required to complete computationally complex tasks is compromised in children with ETPKU. Such an insufficiency may explain some of the attentional deficits observed in this group of children.