Cognitive Control Mechanisms Revealed by ERP and fMRI: Evidence from Repeated Task-Switching

Abstract

We investigated the extent to which a common neural mechanism is involved in task set-switching and response withholding, factors that are frequently confounded in task-switching and go/no-go paradigms. Subjects' brain activity was measured using event-related electrical potentials (ERPs) and event-related functional MRI (fMRI) neuroimaging in separate studies using the same cognitive paradigm. Subjects made compatible left/right keypress responses to left/right arrow stimuli of 1000 msec duration; they switched every two trials between responding at stimulus onset (GO task-green arrows) and stimulus offset (WAIT task-red arrows). With-holding an immediate response (WAIT vs. GO) elicited an enhancement of the frontal N2 ERP and lateral PFC activation of the right hemisphere, both previously associated with the "no-go" response, but only on switch trials. Task-switching (switch vs. nonswitch) was associated with frontal N2 amplification and right hemisphere ventrolateral PFC activation, but only for the WAIT task. The anterior cingulate cortex (ACC) was the only brain region to be activated for both types of task switch, but this activation was located more rostrally for the WAIT than for the GO switch trials. We conclude that the frontal N2 ERP and lateral PFC activation are not markers for withholding an immediate response or switching tasks per se, but are associated with switching into a response-suppression mode. Different regions within the ACC may be involved in two processes integral to task-switching: processing response conflict (rostral ACC) and overcoming prior response suppression (caudal ACC).

The Role of the Lateral Prefrontal Cortex and Anterior Cingulate in Stimulus-Response Association Reversals

“…This is consistent with a role for this area in endogenous maintenance of task rules/ goals in advance of task execution (Sakai & Passingham, 2003;MacDonald et al, 2000;Konishi, Kawazua, et al, 1999). Other studies have claimed a role for ventrolateral frontal regions in the suppression of automatically cued motor responses under conditions of task/rule conflict (Aron, Monsell, Sahakian, & Robbins, 2004;Swainson et al, 2003;Konishi, Nakajima, et al, 1999), as well as the learning of arbitrary mappings between visual stimuli and motor actions (Passingham, Toni, & Rushworth, 2000). All of these functions are compatible with a more general role for the lateral prefrontal cortex as a working University of Exeter, Exeter, UK memory buffer, within which the neural representation of current task rules are maintained and updated (Owen, 2000;D'Esposito et al, 1998) Task switching studies typically also reveal activity in areas of the medial prefrontal cortex, including the anterior cingulate gyrus.…”

Converging Evidence for a Fronto-Basal-Ganglia Network for Inhibitory Control of Action and Cognition: Figure 1.

“…Although stopping a response that is already initiated is a different form of control from such typical measures as Go/NoGo, switching, and interference resolution, much evidence suggests that all of these tasks recruit partly overlapping circuits, especially with respect to the preSMA and the IFC (Konishi et al, 1999;Swainson et al, 2003;Aron et al, 2004;Buchsbaum et al, 2005;Isoda and Hikosaka, 2007b;Nee et al, 2007). Importantly, the network described above may be effector independent, because preSMA, IFC, and the STN are also recruited by NoGo or stopping studies that have examined the control of eye movements (Stuphorn and Schall, 2006;Chikazoe et al, 2007;Hodgson et al, 2007;Isoda and Hikosaka, 2007a,b) and speech (Xue et al, 2006).…”

Get Aroused and Be Stronger: Emotional Facilitation of Physical Effort in the Human Brain

“…To be fair, we must mention that the VLPFC has also been implicated in nonemotional processing, such as attention switching or response inhibition (Swainson et al, 2003;Hampshire and Owen, 2006), although not consistently (Brody et al, 2001;Kübler et al, 2003). Consequently, one interpretation would be that the VLPFC activation reflected attentional disengagement from emotional pictures.…”