Functional Specialization and Distributed Processing across Marmoset Lateral Prefrontal Subregions

A prominent aspect of the organization of primate lateral prefrontal cortex (lPFC) is its division into a number of cytoarchitecturally distinct subregions. Investigations in macaque lPFC using neurophysiological approaches have provided much insight into the functions associated with these subregions; however, our understanding is based largely on a patchwork of findings from many studies and across many animals, rarely covering the entire lPFC in individual subjects. Here, we leveraged the small size and lissencephalic cortex of the common marmoset ( Callithrix jacchus ) to characterize the responses of large numbers of single lPFC neurons to a diverse collection of test stimuli recorded across sets of lPFC subregions using high-density microelectrode arrays. Untethered extracellular electrophysiological recordings were obtained from two adult marmosets with 4 x 4 mm 96-channel Utah arrays implanted in lPFC, covering areas 8aD, 8aV, 9, 10, 46D, 46V and 47. We employed a test battery comprised of a variety of visual stimuli including faces and body parts, auditory stimuli including marmoset calls, and a spatial working memory task. Task-modulated units and units responsive to different stimulus modalities were distributed throughout the lPFC. Visual, auditory and call-selective units were distributed across all lPFC subregions. Neurons with contralateral visual receptive fields were found in 8aV and 8aD. Neurons responsive to faces and saccade-related units were found in 8aV, 8aD, 10, 46V and 47. These findings demonstrate that responses to some stimuli are relatively restricted within specific lPFC subregions, while others are more distributed throughout the marmoset lPFC.