Dynamics of motion signaling by neurons in macaque area MT.
Most neurons in macaque area MT are selective for the direction of stimulus motion. By comparing direction selectivity for gratings and plaids, we classified MT neurons as pattern direction selective (PDS) or component direction selective (CDS). We compared the time course of responses in CDS and PDS neurons in opiate-anesthetized macaques, using a rapid pseudorandom sequence of gratings and plaids that moved in different directions. On average, responses began 6 ms earlier in CDS neurons than in PDS neurons. More importantly, the pattern-selective responses of PDS neurons did not reach their fully selective state until 50-75 ms after the responses of CDS neurons had stabilized. The population motion response of MT is therefore initially dominated by component motion signals, and does not completely represent pattern motion until substantially later. The circuits that compute pattern motion take more time to finish their work than those signaling component motion.
Smith
Matthew A
MA
Center for Neural Science, 4 Washington Place, New York University, New York, New York 10003, USA.
Majaj
Najib J
NJ
Movshon
J Anthony
JA
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D008252:Macaca fascicularis / Q000502:physiology*; D009038:Motion; D009039:Motion Perception / Q000502:physiology*; D009474:Neurons / Q000145:classification / Q000502:physiology*; D017711:Nonlinear Dynamics; D009949:Orientation / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D014793:Visual Cortex / Q000166:cytology* / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology