Cerebral Economics: Resource Competition within but not Between Hemispheres.

Abstract : In this paper, we test a model in which it is assumed that the left and right cerebral hemispheres have access to independent supplies of resources, which they may each use in most kinds of information processing situations. Eight male subjects were specifically selected for having demonstrated a strong right-hand superiority on several manual tasks, and a strong RVF-LH superiority for processing the stimuli we would be using as a verbal memory load in a dual-task situation. Their performance was then measured on the memory load task, on a target task in which pairs of stimuli were presented to either visual field and subjects performed physical or name identity judgments, and in a situation in which both tasks were combined. In our approach, right and left visual field trials of the target task combined with the verbal memory load are treated as two different dual-task situations, comprising cases of complete vs. no overlap in demand for left hemisphere resources, respectively. Subjects were paid for both single and dual-task performance; in the latter case, the payoff ratios rewarded them more for either their memory or target task accuracy. Decrements from single-task performance were less severe on both tasks when subjects were performing physical rather than name matches, and importantly, when the target stimuli were presented to the LVF rather than the RVF. The data support the idea that the resource supplies of the left and right hemispheres are independent, and have implications for both cerebral specialization and divided attention issues.