Human dorsal anterior cingulate cortex neurons mediate ongoing behavioural adaptation.
ABSTRACT The ability to optimize behavioural performance when confronted with continuously evolving environmental demands is a key element of human cognition. The dorsal anterior cingulate cortex (dACC), which lies on the medial surface of the frontal lobes, is important in regulating cognitive control. Hypotheses about its function include guiding reward-based decision making, monitoring for conflict between competing responses and predicting task difficulty. Precise mechanisms of dACC function remain unknown, however, because of the limited number of human neurophysiological studies. Here we use functional imaging and human single-neuron recordings to show that the firing of individual dACC neurons encodes current and recent cognitive load. We demonstrate that the modulation of current dACC activity by previous activity produces a behavioural adaptation that accelerates reactions to cues of similar difficulty to previous ones, and retards reactions to cues of different difficulty. Furthermore, this conflict adaptation, or Gratton effect, is abolished after surgically targeted ablation of the dACC. Our results demonstrate that the dACC provides a continuously updated prediction of expected cognitive demand to optimize future behavioural responses. In situations with stable cognitive demands, this signal promotes efficiency by hastening responses, but in situations with changing demands it engenders accuracy by delaying responses.
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ABSTRACT: In this study on functional coupling in bimanual grasping movements, nine normal subjects had to reach and grasp two different objects simultaneously. Both objects could be either small or large, resulting in four different conditions of bimanual grasping. The main dependent variables were the coupling coefficients calculated either between the hand displacements or between the grip apertures of both hands, serving as variables for the coupling of the reach and the grasp component respectively. The correlation was significantly higher for the reach component than for the grasp component, with only the latter one changing significantly with variation of object size. These findings suggest different temporo-spatial coupling modes for the reach and the grasp components of bimanual grasping movements.Neuroreport 12/2000; 11(17):3787-91. · 1.66 Impact Factor