Anterior cingulate activity during routine and non-routine sequential behaviors in macaques

Anterior cingulate cortex is important in monitoring action for new challen ges. We recorded neuron activity in the anterior cingulate sulcus of macaqu es while they performed a sequential problem-solving task. By trial and err or, animals determined the correct sequence for touching three fixed spatia l targets. After the sequence was repeated three times, we then changed the correct solution order, requiring a new search. Irrespective of component movements or their kinematics, task-related neurons encoded the serial orde r of the sequence. Neurons activated with sequence components (68%) differe d in activity between search and repetition. Search-related activity occurr ed when behavioral flexibility was required and ended as soon as the animal accumulated enough information to infer the solution, but had not yet test ed it. Repetition-related activity occurred in a regime of memory-based mot or performance in which attention to action is less necessary.