Regional differences in the effects of task difficulty and motor output on blood flow response in the human anterior cingulate cortex

Abstract

We reviewed 107 blood flow activation studies carried out with positron emission tomography and published between January 1993 and November 1996. These studies had reported their findings as peaks of significant difference in cerebral blood-flow (CBF) between two scans/tasks and had located the peaks in standardized stereotaxic space. We coded each task along several dimensions, including the type and rate of input and output, the types of cognitive processes, and the relative difficulty of tasks within a study. Based on this coding, a difference score (A-B) was calculated for each subtraction. Subsequently, the frequency distributions of the difference scores for subtractions yielding a peak in the anterior cingulate region (cingulate peak) were compared with those distributions obtained from subtractions without a cingulate peak (no cingulate-peak). The cingulate peak subtractions (n = 158) differed from the no cingulate peak subtractions (n = 229) in terms of difficulty level (p = 0.001) and the presence of a remote memory component (p = 0.01). Regional differences in the frequency distribution of certain task parameters, such as difficulty level, recent memory and the use of the hand for responding, were also observed when peaks found in the anterior cingulate cortex (ACC) were further classified as located in the rostral vs caudal ACC, supracallosal vs subcallosal ACC, and limbic vs paralimbic parts of the supracallosal ACC. We conclude that task difficulty plays a major role in modulating blood-flow response in the ACC, possibly interacting with other parameters such as the nature of the response and memory demands.

Conflict monitoring and anterior cingulate cortex: an update

“…With this in mind, it is interesting to consider the hypothesis that conflict might serve as an index of the demand for mental effort. Consistent with this, it has been noted that the ACC becomes active in just those task settings that are experienced as cognitively difficult [37,76]. Indeed, as we have argued elsewhere [4], the induction of conflict can plausibly be considered to be a defining feature of difficult tasks.…”

The Anterior Cingulate and Error Avoidance

“…This leaves open the confound that increased mental effort on larger set sizes may have driven the greater ACC activation (Paus et al, 1998), rather than rejection per se. However, a secondary analysis on a subset of events in which the error and reject trials were equated for the numbers of large and small set sizes (across subject average of 37 events of small size and 22 events of large size in both conditions) identified an ACC region, encompassing both ACC regions (BA 24 and BA 32) identified above, that showed greater activity for rejections than errors (2269 l; x ϭ 2, y ϭ 11, z ϭ 41; t (12) ϭ 3.14; p Ͻ 0.01).…”

Effects of Expectancy and Abstinence on the Neural Response to Smoking Cues in Cigarette Smokers: an fMRI Study

“…Several theories of ACC function have been proposed, most commonly invoking a role in attention and arousal. Paus et al (1998) argue that supracallosal ACC activation across a wide range of cognitive and emotional tasks is due to engagement of nonspecific arousal systems Expectancy affects the neural response to drug cues D McBride et al that project from the brainstem via the thalamus to the ACC. Our finding of an increase in functional connectivity between the ACC and dorsomedial thalamus when comparing the smoking to the control videos, at coordinates identical to those identified in previous studies of arousal (Hofle et al, 1997;Paus, 2000), suggests that smoking cues act on thalamo-cortical arousal systems.…”