Human Anterior Cingulate Cortex Neurons Encode Cognitive and Emotional Demands

The cortical mechanisms and substrates of cognitive and emotional demands are poorly understood. Lesion studies and functional imaging implicate the anterior cingulate cortex (ACC). The caudal ACC (cACC) has been implicated in cognitive processes such as attention, salience, interference, and response competition, mostly on the basis of neuroimaging results. To test the hypothesis that individual cACC neurons subserve these functions, we monitored neuronal activity from single cells in the cACC while subjects were engaged in a mental arithmetic task, the cognitively demanding counting Stroop task, and/or the emotional Stroop interference task. We now report the first direct measures of single neurons in humans identifying a population of cACC neurons that respond differentially or in a graded manner to cognitively demanding high- and low-conflict Stroop tasks, including those with emotional valence. These data indicate that cACC neurons may be acting as salience detectors when faced with conflict and difficult or emotional stimuli, consistent with neuroimaging results of cACC responses to abrupt sensory, novel, task-relevant, or painful stimuli.