Single-unit responses to whole-field visual stimulation in the pretectum of Rana pipiens.
Visually responsive single units were recorded from the pretectal region that includes the large-celled nucleus lentiformis mesencephali (nLM) in the leopard frog, Rana pipiens. During monocular stimulation of the contralateral eye, 60 single units responding to movement of a large-field, random-dot pattern were quantitatively analyzed using horizontal and vertical directions at each of four pattern velocities (0.4-40 degrees/s). All units were spontaneously active, motion sensitive, and the majority showed 'on'-'off' responses. Several different response profiles were observed, including velocity-sensitive units with peak response at 10 degrees/s, most of which showed directional selectivity, and speed-sensitive units that showed increasing spike frequencies as pattern velocity increased, but little or no directional selectivity. About one-third of all unit analyzed were direction-selective, and 55% of those responded optimally to the temporal-to-nasal (T-N) direction of motion. T-N units were recorded primarily from an area that lies dorsolaterally between nLM and the optic tectum, in the 'peri-nLM' region. The pronounced monocular optokinetic nystagmus (OKN) response asymmetry that occurs in anurans appears to be reflected in the response profiles of the T-N direction selective units.
Li
Z
Z
Neuroscience and Behavior Program, University of Massachusetts, Amherst 01003, USA.
Fite
K V
KV
Montgomery
N M
NM
Wang
S R
SR
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D004594:Electrophysiology; D009475:Neurons, Afferent / Q000502:physiology; D009759:Nystagmus, Pathologic / Q000503:physiopathology; D010775:Photic Stimulation; D011894:Rana pipiens; D013477:Superior Colliculi / Q000166:cytology / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology