title: Dorsal premotor cortex: neural correlates of reach target decisions based on a color-location matching rule and conflicting sensory evidence.
abstract: We recorded single-neuron activity in dorsal premotor (PMd) and primary motor cortex (M1) of two monkeys in a reach-target selection task. The monkeys chose between two color-coded potential targets by determining which target's color matched the predominant color of a multicolored checkerboard-like Decision Cue (DC). Different DCs contained differing numbers of colored squares matching each target. The DCs provided evidence about the correct target ranging from unambiguous (one color only) to very ambiguous and conflicting (nearly equal number of squares of each color). Differences in choice behavior (reach response times and success rates as a function of DC ambiguity) of the monkeys suggested that each applied a different strategy for using the target-choice evidence in the DCs. Nevertheless, the appearance of the DCs evoked a transient coactivation of PMd neurons preferring both potential targets in both monkeys. Reach response time depended both on how long it took activity to increase in neurons that preferred the chosen target and on how long it took to suppress the activity of neurons that preferred the rejected target, in both correct-choice and error-choice trials. These results indicate that PMd neurons in this task are not activated exclusively by a signal proportional to the net color bias of the DCs. They are instead initially modulated by the conflicting evidence supporting both response choices; final target selection may result from a competition between representations of the alternative choices. The results also indicate a temporal overlap between action selection and action initiation processes in PMd and M1.
authors: Groupe de recherche sur le système nerveux central (Fonds de recherche du Québec-Santé), Département de Neurosciences, Faculté de Médecine, Université de Montréal, succursale Centre-Ville, Montréal, Québec, Canada; and.
authors: Émilie
authors: É
authors: Coallier
authors: Université Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, Bordeaux, France; and Centre National de la Recherche Scientifique, Institut des Maladies Neurodégénératives, UMR 5293, Bordeaux, France.
authors: Thomas
authors: T
authors: Michelet
authors: Groupe de recherche sur le système nerveux central (Fonds de recherche du Québec-Santé), Département de Neurosciences, Faculté de Médecine, Université de Montréal, succursale Centre-Ville, Montréal, Québec, Canada; and john.francis.kalaska@umontreal.ca.
authors: John F
authors: JF
authors: Kalaska
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001245:Association Learning / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology*; D003116:Color; D008253:Macaca mulatta; D008297:Male; D009044:Motor Cortex / Q000166:cytology*; D009474:Neurons / Q000502:physiology*; D009949:Orientation; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013223:Statistics as Topic
keywords: decision making; primary motor cortex; reaching