Visual neurons in the pigeon brain encode the acceleration of stimulus motion.
Seeing target motion is a vital capability of the visual system in humans and animals. Physically, motion is described by its acceleration, speed, and direction. Motion-sensitive neurons in all the visual areas examined to date are selective for the direction and speed of motion. Here, we show by single-unit recording that one-third of motion-sensitive neurons in the pigeon's pretectal nucleus also encode the acceleration of stimulus motion. These neurons are characterized by plateau-shaped speed-tuning curves in which the firing rate is the same over a wide range of speeds, a feature that allows these neurons to encode unambiguously the rate of change of speed over time. Acceleration-sensitive neurons also show transient responses to the offset of motion in the preferred and/or nonpreferred directions; acceleration-insensitive neurons do not. We observed the same sensitivity to target acceleration for brief ramps of stimulus speed and for sinusoidal modulation of speed. The locations of acceleration-sensitive and -insensitive neurons are segregated in the pretectal nucleus. The visual responses of pretectal neurons indicate that the visual and vestibular systems share not only a spatial but also a temporal reference frame that can detect the acceleration produced by self-motion of an organism.
Cao
Peng
P
Laboratory for Visual Information Processing, Institute of Biophysics, and Graduate School, Chinese Academy of Sciences, Beijing 100101, China.
Gu
Yong
Y
Wang
Shu-Rong
SR
D000054:Acceleration; D000200:Action Potentials; D000818:Animals; D001931:Brain Mapping; D010856:Columbidae / Q000502:physiology*; D008636:Mesencephalon / Q000502:physiology*; D008959:Models, Neurological; D009039:Motion Perception / Q000502:physiology*; D009474:Neurons / Q000145:classification / Q000502:physiology*; D017120:Nystagmus, Optokinetic / Q000502:physiology; D010775:Photic Stimulation; D014722:Vestibule, Labyrinth / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*