Practice makes a hemisphere perfect: The advantage of interhemispheric recruitment is eliminated with practice.

As task performance improves with practice, oftentimes fewer brain areas are recruited to aid in processing. However, relatively little research has investigated how practice affects interactions between brain regions. Given prior work indicating that interhemispheric division of processing is most advantageous when task demands are high, we predicted that interactions between the cerebral hemispheres would be less advantageous after practice than before practice. This hypothesis was confirmed by reanalysis of data from two previously published studies. Practice reduced (1) the degree to which interhemispheric interaction facilitated performance for two letter-matching tasks (Experiment 1), and (2) the extent to which interhemispheric interaction reduced interference in a global-local perception task (Experiment 2). These findings illustrate the dynamic nature of neural recruitment in response to changing task demands.