Rule-Guided Executive Control of Response Inhibition: Functional Topography of the Inferior Frontal Cortex

Weidong Cai,Hoi-Chung Leung,Mark W. Greenlee

doi:10.1371/journal.pone.0020840

Abstract

BackgroundThe human inferior frontal cortex (IFC) is a large heterogeneous structure with distinct cytoarchitectonic subdivisions and fiber connections. It has been found involved in a wide range of executive control processes from target detection, rule retrieval to response control. Since these processes are often being studied separately, the functional organization of executive control processes within the IFC remains unclear.Methodology/Principal FindingsWe conducted an fMRI study to examine the activities of the subdivisions of IFC during the presentation of a task cue (rule retrieval) and during the performance of a stop-signal task (requiring response generation and inhibition) in comparison to a not-stop task (requiring response generation but not inhibition). We utilized a mixed event-related and block design to separate brain activity in correspondence to transient control processes from rule-related and sustained control processes. We found differentiation in control processes within the IFC. Our findings reveal that the bilateral ventral-posterior IFC/anterior insula are more active on both successful and unsuccessful stop trials relative to not-stop trials, suggesting their potential role in the early stage of stopping such as triggering the stop process. Direct countermanding seems to be outside of the IFC. In contrast, the dorsal-posterior IFC/inferior frontal junction (IFJ) showed transient activity in correspondence to the infrequent presentation of the stop signal in both tasks and the left anterior IFC showed differential activity in response to the task cues. The IFC subdivisions also exhibited similar but distinct patterns of functional connectivity during response control.Conclusions/SignificanceOur findings suggest that executive control processes are distributed across the IFC and that the different subdivisions of IFC may support different control operations through parallel cortico-cortical and cortico-striatal circuits.

Highlights

The inferior frontal cortex (IFC) has been associated with a variety of cognitive or executive control processes from target detection, rule retrieval to response control [1,2,3,4,5,6,7]
Studies of human adults with frontal lobe damage [9] and transcranial magnetic stimulation (TMS) of the healthy brain [10] have shown that the right inferior frontal gyrus (IFG), in particular the pars opercularis, is critical to the performance of the stop-signal task (SST), which is a cognitive control task requiring the inhibition of prepotent motor responses
Our results demonstrate that the executive control functions such as response inhibition, infrequent target detection and rule retrieval are distributed across the IFC

Summary

Introduction

The inferior frontal cortex (IFC) has been associated with a variety of cognitive or executive control processes from target detection, rule retrieval to response control [1,2,3,4,5,6,7]. Studies of human adults with frontal lobe damage [9] and transcranial magnetic stimulation (TMS) of the healthy brain [10] have shown that the right inferior frontal gyrus (IFG), in particular the pars opercularis, is critical to the performance of the stop-signal task (SST), which is a cognitive control task requiring the inhibition of prepotent motor responses In agreement with these findings, neuroimaging studies have shown activations in the posterior IFC during the SST [1,11,12,13,14,15,16,17]. The human inferior frontal cortex (IFC) is a large heterogeneous structure with distinct cytoarchitectonic subdivisions and fiber connections It has been found involved in a wide range of executive control processes from target detection, rule retrieval to response control. Since these processes are often being studied separately, the functional organization of executive control processes within the IFC remains unclear

Methods

Results

Conclusion