Prefrontal Activation Evoked by Infrequent Target and Novel Stimuli in a Visual Target Detection Task: An Event-Related Functional Magnetic Resonance Imaging Study

Abstract

An event-related functional magnetic resonance imaging study of prefrontal cortex was conducted during which subjects performed a visual "oddball" target detection task. Exemplars of three stimulus categories were presented at a rate of one per 1.5 sec for 10 runs, each consisting of 132 trials. Standards were color squares of varying sizes that were presented on ϳ92% of trials. Targets were color circles of varying sizes presented irregularly on ϳ4% of trials. Novels were pictures of everyday objects that were also presented irregularly on ϳ4% of trials. Ten subjects participated in two separate sessions in which they were required to count mentally or to push a button whenever a target appeared. Targets evoked activation within prefrontal cortex, primarily within the middle frontal gyri (MFG). This MFG activation did not differ as a function of the required response. Novels did not evoke significant activity within this region despite evidence from a separate behavioral and event-related potential study demonstrating their strong influence on processing. In additional imaging sessions with two subjects, the rules were reversed to require a button press whenever an object, but not a circle, appeared. These former novels now evoked activation in the MFG, but the former target circles did not. These experiments indicate that MFG activation is reliably evoked by exemplars from arbitrary stimulus categories that are mapped by experimental rules onto an arbitrary covert or overt response.

Emotion?attention network interactions during a visual oddball task

“…The dorsal frontoparietal regions engaged by attentional targets in the present study are consistent with those reported in previous oddball tasks [4,8,9,25,35,49]. Furthermore, we show here that these dorsal regions respond to task-relevant oddball stimuli similarly despite variations in their emotional properties.…”

“…Finally, we test whether the oddball response in dorsal brain regions is invariant to emotional content. Because dorsal frontoparietal cortex is consistently activated in oddball tasks that have used a variety of target stimuli [8,9,25,35,49], we expect to see similar activity in these regions across the two experimental groups.…”

Updating P300: An integrative theory of P3a and P3b

“…Indeed, elegant cellular recording studies in primates indicate that information induced by changes in frontal activation during a matching-to-sample task is shunted to inferotemporal structures that index task context updating for future stimulus presentations (Desimone et al, 1995). Thus, it is reasonable to suppose that P3a and P3b generation stems from frontal and temporal/parietal activations (Ebmeier et al, 1995;Kirino et al, 2000).…”

Event-Related Brain Potentials in the Study of Inhibition: Cognitive Control, Source Localization and Age-Related Modulations

“…Polich and Comerchero (2003) and novel stimuli, which is linked to frontal lobe activity. The P3b is related to a controlled cognitive attentional process that is tied to the stimulus evaluation process, which is linked to temporal/parietal areas (Kirino et al 2000;Polich 2007). …”