Proefschrift_Holstein

Chapter 6

Abstract The ability to adapt behavior based on environmental cues (e.g. task switching) is an important aspect of cognitive functioning, one that can be influenced by the prospect of reward. However, experimental evidence elucidating the exact neural mechanism by which changes in reward motivation inform flexible control is lacking. A primary candidate for this function is the nucleus accumbens core (AcbC), which has been proposed as a link between motivation and cognition by several theoretical accounts. The current study aimed to develop a rewarded task-switching paradigm in rodents, in parallel to a paradigm extensively studied in humans. Using this paradigm, we subsequently aimed to test whether lesions of the AcbC disrupt the integration of reward information and cued flexible control. First, rats learned to discriminate between two auditory (A1 - A2) and two visual (V1 - V2) stimuli, which were associated with a distinct task cue. Further, training and testing took place in high (3 pellet) and low (1 pellet) reward contexts. On test, animals were presented with response-incongruent compound stimuli (A1V2 / A2V1) and had to rely on the task cue to disambiguate which of the stimuli (i.e. auditory or visual) would yield a rewarded response. Within this test, on a trial-by-trial basis, the task cue could either switch (e.g. auditory -> visual) or remain the same (e.g. auditory -> auditory), allowing the assessment of proactive flexible control by comparing switch and repeat trials. Task-switching performance improved in the high reward condition, but only in animals with an intact AcbC (prior to surgery or after sham surgery). These findings provide direct evidence that the AcbC is involved in using reward information to optimize cognitive control.

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