title: The Largest Response Component in the Motor Cortex Reflects Movement Timing but Not Movement Type.
abstract: Neural activity in monkey motor cortex (M1) and dorsal premotor cortex (PMd) can reflect a chosen movement well before that movement begins. The pattern of neural activity then changes profoundly just before movement onset. We considered the prediction, derived from formal considerations, that the transition from preparation to movement might be accompanied by a large overall change in the neural state that reflects when movement is made rather than which movement is made. Specifically, we examined "components" of the population response: time-varying patterns of activity from which each neuron's response is approximately composed. Amid the response complexity of individual M1 and PMd neurons, we identified robust response components that were "condition-invariant": their magnitude and time course were nearly identical regardless of reach direction or path. These condition-invariant response components occupied dimensions orthogonal to those occupied by the "tuned" response components. The largest condition-invariant component was much larger than any of the tuned components; i.e., it explained more of the structure in individual-neuron responses. This condition-invariant response component underwent a rapid change before movement onset. The timing of that change predicted most of the trial-by-trial variance in reaction time. Thus, although individual M1 and PMd neurons essentially always reflected which movement was made, the largest component of the population response reflected movement timing rather than movement type.
authors.affiliation: Neurosciences Program, Stanford University, Stanford, California 94305; Department of Electrical Engineering, Stanford University, Stanford, California 94305; Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724.
authors.forename: Matthew T
authors.identifier: 0000-0002-8072-023X
authors.initials: MT
authors.lastname: Kaufman
authors.affiliation: Department of Neuroscience.
authors.forename: Jeffrey S
authors.identifier: 0000-0002-4242-8422
authors.initials: JS
authors.lastname: Seely
authors.affiliation: Neurosciences Program, Stanford University, Stanford, California 94305; Department of Electrical Engineering, Stanford University, Stanford, California 94305.
authors.forename: David
authors.initials: D
authors.lastname: Sussillo
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California 94305; Department of Neurosurgery, Palo Alto Medical Foundation, Palo Alto, California 94301.
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Ryu
authors.affiliation: Neurosciences Program, Stanford University, Stanford, California 94305; Department of Electrical Engineering, Stanford University, Stanford, California 94305; Department of Bioengineering, Stanford University, Stanford, California 94305; Department of Neurobiology, Stanford University, Stanford, California 94305; Howard Hughes Medical Institute, Stanford University, Stanford, California 94305.
authors.forename: Krishna V
authors.identifier: 0000-0003-1534-9240
authors.initials: KV
authors.lastname: Shenoy
authors.affiliation: Department of Neuroscience; Grossman Center for the Statistics of Mind, David Mahoney Center for Brain and Behavior Research, Kavli Institute for Brain Science, Columbia University Medical Center, New York, NY 10032.
authors.forename: Mark M
authors.initials: MM
authors.lastname: Churchland
mesh_terms: D000200:Action Potentials; D000818:Animals; D001132:Arm / Q000502:physiology; D004576:Electromyography; D008253:Macaca mulatta; D008297:Male; D008839:Microelectrodes; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009483:Neuropsychological Tests; D011930:Reaction Time; D013997:Time Factors
keywords: condition-invariant signal; dPCA; movement initiation; movement triggering; reaction time; state space