Neurophysiology: Differentiating Functional Contributions across Prefrontal Cortex

Excerpt

A long history of research in neuropsychology has supported the idea that there is functional specialization within the prefrontal cortex (PFC). To better understand how a region subserves a specific function, neuron activity is often recorded from multiple areas as subjects engage in prefrontal-dependent cognitive tasks. Contrary to expectations, these studies have generally found that neurons across PFC encode all manner of task-relevant information, with relatively little difference among regions. These data are important because they demonstrate the vast representational capacity and flexibility of PFC, yet they have been less useful when trying to glean a mechanistic understanding of how regions differ and interact with each other. In this chapter, these data are first reviewed, then considerations are proposed that might better direct future studies. Discussion includes the anatomy and evolutionary origins of the primate PFC, which suggest a gradient organization, with a main division between dorsal and ventral trends, rather than a series of smaller discrete regions. These gradients are observable in neural recordings within and across regions and may provide insights into the functional organization of PFC. It is important to note that gradients are consistent with functional differentiation across PFC, but they suggest continuous rather than discrete changes in function. Second, recent advances in neural analysis are reviewed, which focus on representations and temporal dynamics in neural populations, as opposed to individual neurons. These population codes may reveal unique insights into local function and cross-regional interactions and help us understand the unique properties of the main divisions of PFC.