title: Response to rates of luminance change of sustained and transient cells in the cat lateral geniculate nucleus and optic tract.
abstract: We recorded the response of sustained (X) and transient (Y) cells in the cat lateral geniculate nucleus (LGN) and optic tract to a stationary spot while the spot luminance was increased and decreased with a constant rate (linear luminance functions), or modulated sinusoidally. The spot filled the receptive field center, and was surrounded by an annulus of fixed luminance. The LGN X cells seemed to perform a differentiation-like operation in the time domain at slow temporal modulations, giving information about rate of luminance change. To the linear luminance functions the cells responded with a constant firing rate. The on-center cells were activated during increasing luminance, the off-center cells during decreasing luminance. This firing rate increased monotonically with rate of luminance change. To low-frequency sinusoidal modulations the cells had a marked negative phase shift. The response of the LGN Y cells had a transient component shortly after the luminance started to increase (on-center cells) or decrease (off-center cells), followed by a secondary, gradually changing component. The peak of the transient component occurred on average when the response of the X cells increased most rapidly. To low-frequency sinusoidal modulation the average negative phase shift of this peak was twice the average of the X cells. The Y system could accordingly provide information about rate of change in the response of the X system. In the optic tract the X fiber response resembled the LGN X cell response in most respects. The Y fibers had only a weak transient response component, so this component was accentuated in the thalamic relay. Also the sensitivity for rate of luminance change was increased in LGN.
authors.affiliation: Institute of Neurophysiology, University of Oslo, Norway.
authors.forename: P
authors.initials: P
authors.lastname: Heggelund
authors.forename: H E
authors.initials: HE
authors.lastname: Karlsen
authors.forename: G
authors.initials: G
authors.lastname: Flugsrud
authors.forename: T
authors.initials: T
authors.lastname: Nordtug
mesh_terms: D000200:Action Potentials; D000818:Animals; D002415:Cats; D005829:Geniculate Bodies / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D012160:Retina / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000145:classification / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*