title: Predominance of Movement Speed Over Direction in Neuronal Population Signals of Motor Cortex: Intracranial EEG Data and A Simple Explanatory Model.
abstract: How neuronal activity of motor cortex is related to movement is a central topic in motor neuroscience. Motor-cortical single neurons are more closely related to hand movement velocity than speed, that is, the magnitude of the (directional) velocity vector. Recently, there is also increasing interest in the representation of movement parameters in neuronal population activity, such as reflected in the intracranial EEG (iEEG). We show that in iEEG, contrasting to what has been previously found on the single neuron level, speed predominates over velocity. The predominant speed representation was present in nearly all iEEG signal features, up to the 600-1000 Hz range. Using a model of motor-cortical signals arising from neuronal populations with realistic single neuron tuning properties, we show how this reversal can be understood as a consequence of increasing population size. Our findings demonstrate that the information profile in large population signals may systematically differ from the single neuron level, a principle that may be helpful in the interpretation of neuronal population signals in general, including, for example, EEG and functional magnetic resonance imaging. Taking advantage of the robust speed population signal may help in developing brain-machine interfaces exploiting population signals.
authors.affiliation: Epilepsy Center, University Medical Center Freiburg, 79106 Freiburg, Germany Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany Department of Paediatric Neurology, 2nd Faculty of Medicine and Motol University Hospital Department of Neurology, 2nd Faculty of Medicine and Motol University Hospital, Charles University, 150 06 Prague, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Hammer
authors.affiliation: Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany Bernstein Center Freiburg, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Pistohl
authors.affiliation: Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany CorTec GmbH, 79110 Freiburg, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Fischer
authors.affiliation: Department of Paediatric Neurology, 2nd Faculty of Medicine and Motol University Hospital.
authors.forename: Pavel
authors.initials: P
authors.lastname: Kršek
authors.affiliation: Department of Neurology, 2nd Faculty of Medicine and Motol University Hospital, Charles University, 150 06 Prague, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Tomášek
authors.affiliation: Department of Neurology, 2nd Faculty of Medicine and Motol University Hospital, Charles University, 150 06 Prague, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Marusič
authors.affiliation: Epilepsy Center, University Medical Center Freiburg, 79106 Freiburg, Germany Bernstein Center Freiburg, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schulze-Bonhage
authors.affiliation: Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany Bernstein Center Freiburg, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Ad
authors.initials: A
authors.lastname: Aertsen
authors.affiliation: Epilepsy Center, University Medical Center Freiburg, 79106 Freiburg, Germany Bernstein Center Freiburg, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Tonio
authors.initials: T
authors.lastname: Ball
mesh_terms: D000293:Adolescent; D000328:Adult; D001132:Arm / Q000502:physiology; D001696:Biomechanical Phenomena; D000069280:Electrocorticography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009483:Neuropsychological Tests; D055815:Young Adult
keywords: ECoG; brain–machine interface; population signals; tuning; velocity