title: Separate spatial and temporal frequency tuning to visual motion in human MT+ measured with ECoG.
abstract: The human middle temporal complex (hMT+) has a crucial biological relevance for the processing and detection of direction and speed of motion in visual stimuli. Here, we characterized how neuronal populations in hMT+ encode the speed of moving visual stimuli. We evaluated human intracranial electrocorticography (ECoG) responses elicited by square-wave dartboard moving stimuli with different spatial and temporal frequency to investigate whether hMT+ neuronal populations encode the stimulus speed directly, or whether they separate motion into its spatial and temporal components. We extracted two components from the ECoG responses: (1) the power in the high-frequency band (HFB: 65-95 Hz) as a measure of the neuronal population spiking activity and (2) a specific spectral component that followed the frequency of the stimulus's contrast reversals (SCR responses). Our results revealed that HFB neuronal population responses to visual motion stimuli exhibit distinct and independent selectivity for spatial and temporal frequencies of the visual stimuli rather than direct speed tuning. The SCR responses did not encode the speed or the spatiotemporal frequency of the visual stimuli. We conclude that the neuronal populations measured in hMT+ are not directly tuned to stimulus speed, but instead encode speed through separate and independent spatial and temporal frequency tuning. Hum Brain Mapp 38:293-307, 2017. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, 3584 CX, The Netherlands.|Department of Radiology, University Medical Center Utrecht, Utrecht, 3584 CX, The Netherlands.
authors.forename: Anna
authors.initials: A
authors.lastname: Gaglianese
authors.affiliation: Department of Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, 3584 CS, The Netherlands.
authors.forename: Ben M
authors.identifier: 0000-0003-2694-618X
authors.initials: BM
authors.lastname: Harvey
authors.affiliation: Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, 3584 CX, The Netherlands.
authors.forename: Mariska J
authors.initials: MJ
authors.lastname: Vansteensel
authors.affiliation: Department of Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, 3584 CS, The Netherlands.
authors.forename: Serge O
authors.initials: SO
authors.lastname: Dumoulin
authors.affiliation: Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, 3584 CX, The Netherlands.
authors.forename: Nick F
authors.initials: NF
authors.lastname: Ramsey
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, 3584 CX, The Netherlands.
authors.forename: Natalia
authors.initials: N
authors.lastname: Petridou
mesh_terms: D001931:Brain Mapping; D000069280:Electrocorticography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D015233:Models, Statistical; D009038:Motion; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation; D013028:Space Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*
keywords: hMT+; human electrocorticography; neuronal population responses; speed encoding; visual motion