Kelly Garner

Re-characterising the functional neural changes underlying cognitive enhancement.

For as long as we have systematically studied the function of the human brain, we have recognised that practice improves cognition . Despite this longstanding recognition, much remains to be learned about how these improvements are realised in the human brain. To date, two theoretical assumptions have been particularly influential in the characterisation of the functional neural changes underpinning practice-related improvements in cognition. The first assumption is that practice related decreases in brain activity reflect a decrease in functional contribution of that brain region to the cognitive operation . The second assumption is that practice transitions dependence from an ‘effortful’ frontoparietal network to a sensorimotor-striatal network (now referred to as the cortical-to-striatal model). Both of these assumptions, grounded in human functional imaging literature, are at odds with models derived from animal learning studies. Using multitasking as a case study, we conducted a large-scale fMRI study to interrogate the validity of these assumptions. Contradictory to the first assumption, we show that regions showing practice-related activity decreases actually show increases in measures of task-related information, and that this increase predicts performance improvements. This suggests that regional reductions in brain activity do not always reflect a decreased involvement of that region in the cognitive operation under interrogation. Furthermore, by modelling connectivity changes between brain regions, we find that in contradiction to the second assumption, models derived from the animal literature that emphasise the importance of striatal-cortical connections early in learning, and cortical-cortical connections late in learning, provide a better account for the data than the cortical-to-striatal model. Overall, these findings challenge the current characterisation of the functional neural architecture underpinning performance improvements derived from cognitive practice.