Dynamic Coding for Cognitive Control in Prefrontal Cortex

Abstract

SummaryCognitive flexibility is fundamental to adaptive intelligent behavior. Prefrontal cortex has long been associated with flexible cognitive function, but the neurophysiological principles that enable prefrontal cells to adapt their response properties according to context-dependent rules remain poorly understood. Here, we use time-resolved population-level neural pattern analyses to explore how context is encoded and maintained in primate prefrontal cortex and used in flexible decision making. We show that an instruction cue triggers a rapid series of state transitions before settling into a stable low-activity state. The postcue state is differentially tuned according to the current task-relevant rule. During decision making, the response to a choice stimulus is characterized by an initial stimulus-specific population response but evolves to different final decision-related states depending on the current rule. These results demonstrate how neural tuning profiles in prefrontal cortex adapt to accommodate changes in behavioral context. Highly flexible tuning could be mediated via short-term synaptic plasticity.

The neural basis of attentional control in visual search

“…Although spatially global working memory representations do exist in visual cortex [15], the question whether preparatory goalselective patterns of visual activity are generally position-invariant, and whether this is a necessary requirement for their role as attentional templates still needs to be systematically addressed. 5 In line with the involvement of prefrontal cortex in visual working memory (Box 1), preparatory activation patterns that are sensitive to current task goals have also been observed in prefrontal areas [13,20,21]. These effects may be linked to top-down aspects of attentional preparation, with prefrontal cortex controlling target-selective preparatory modulations of visual activity, but could also reflect explicit representations of search goals.…”

Stable population coding for working memory coexists with heterogeneous neural dynamics in prefrontal cortex

“…To minimize bias in characterizing population activity, neurons were not preselected for tuning properties. We used a pseudopopulation approach to study the statespace dynamics of population activity (8,12,16,17), rather than the properties of the heterogenous individual neurons (Figs. S1 and S2).…”

“…Because only a small proportion of WM-related PFC neurons show well-tuned, stable persistent activity, attractor dynamics may not be the dominant form of WM coding. Researchers have emphasized alternative forms of population coding, specifically dynamic coding, in which the mnemonic representation shifts over time during WM maintenance (7,8). In turn, such observations have motivated theoretical proposals for alternative neural circuit mechanisms for WM that produce dynamical and heterogeneous activity (9,10).…”

EPS Mid-Career Award 2014

“…It is possible that such spatially global search templates may not be found at all in visual-perceptual areas, but only in higher-level attentional control regions such as prefrontal cortex, where visual information is represented in a largely position-independent fashion. In fact, patterns of neural activity in prefrontal cortex that are sensitive to current search targets have indeed been observed during the preparation for attentional tasks (Peelen & Kastner, 2011;Warden & Miller, 2010;Stokes et al, 2013). However, it might be premature to completely rule out visual cortex as a possible additional locus for position-independent preparatory attentional templates.…”