A generalized role of interhemispheric interaction under attentionally demanding conditions: evidence from the auditory and tactile modality.

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.