Probing cortical function with electrical stimulation
In a News and Views piece (“Stimulating research on Motor Cortex” 2002, 5:714), Strick comments on our recent finding that microstimulation of motor cortex evokes complex, coordinated behavior (1). A major concern that he raises is that, “one might ask whether electrical stimulation of the cortex is capable of revealing its function.” We agree that one should always ask such questions about all experimental methods. However, a large body of recent work, conspicuously not cited in Strick’s piece, successfully probes cortical function using electrical stimulation. For example, Newsome and colleagues (2) stimulated monkey visual area MT and influenced the monkey’s perceptual decisions about the direction of motion of visual stimuli. Romo and colleagues (3) stimulated primary somatosensory cortex and influenced the monkey’s perceptual decisions about tactile stimuli. Shadlen and colleagues (4) stimulated the frontal eye fields and influenced the monkey’s target selection. Many researchers have used electrical stimulation to study functional maps of eye and head movement (5-7). We took the well-established protocol of stimulating on a behaviorally relevant time scale and applied it to motor cortex. The stimulation durations that we used are within the range of these previous studies, and the current intensities are within the range used in the oculomotor studies. As in previous studies, we evoked meaningful behaviors.