Distinct neural dynamics in prefrontal and premotor cortex during decision-making

Dorsolateral prefrontal cortex (DLPFC) and dorsal premotor cortex (PMd) are two association brain areas implicated in decision making. However, whether these brain areas have similar or distinct decision-related dynamics remains an open question. In addition, anatomical studies suggest considerable connectivity heterogeneity between DLPFC areas and parietal lobe, temporal lobe, and ventrolateral prefrontal cortex. Whether different areas within the DLPFC also demonstrate distinct decision-related dynamics is also an open question.
We addressed these open questions by comparing the neural dynamics between these two brain areas of monkeys performing a decision-making task. In this task, monkeys discriminated the dominant color of a red-green checkerboard and reported their decision with an arm movement. Randomized target configurations allowed us to decouple color choice from action choice and allowed us to examine representation of task variables, including target configuration, color choice, and action choice (defined as arm reaching direction).
Examination of single-unit responses, principal and demixed principal components analysis, and decoding analysis all strongly suggested that neural activity in DLPFC is modulated by target configuration, color choice, and action choice. In contrast, neural activity in PMd was predominantly action choice related, with minimal target configuration and color choice signals across the whole trial. Decoding analysis suggested that all these decision-related variables were more strongly represented in deeper cortical areas of DLPFC compared to the more superficial cortical areas.
Our results suggest that during perceptual decisions, choice is computed in deep DLPFC and then emerges in superficial areas of prefrontal cortex and PMd, a result consistent with predictions of multi-area recurrent neural network models [2]. Simultaneous electrophysiological recordings are needed to test this hypothesis. In summary, DLPFC and PMd demonstrated distinct dynamics as DLPFC encodes target configuration, color, and direction signals, while PMd is largely responsive only to action choice.