NEURONAL CORRELATES OF SENSORIMOTOR ASSOCIATION IN STIMULUS-RESPONSE COMPATIBILITY

Neuronal mechanisms underlying stimulus-response (S-R) associations in S-R compatibility tasks were identified in 2 experiments with monkeys . Visual stimuli were presented on the left and right calling for left -right movements under congruent and incongruent S-R mapping instructi ons. High- and low-pitched tones calling for left-right movements were presented to the left and right ear, and the stimulus side was irrele vant. Single neurons sensitive to the S-R mapping rule were found in t he primary motor cortex. The large overlap between the neuronal popula tions sensitive to the stimulus side, the S-R mapping rule, and the re sponse side, respectively, is consistent with the idea that sensory-to -motor transformation is a continuous rather than a discrete process. Results partly support the hypothesis that the increase in reaction ti me with incongruent mapping is caused by the automatic activation of t he congruent, but erroneous, response.