The Journal of Neurophysiology Vol. 84 No. 5 November 2000, pp. 2529-2540
Copyright ©2000 by the American Physiological Society
Spatiotemporal Properties of Fast and Slow Neurons in the
Pretectal Nucleus Lentiformis Mesencephali in Pigeons
Douglas R. W.
Wylie1,2 and
Nathan A.
Crowder2
1Department of Psychology and
2Division of Neuroscience, University of
Alberta, Edmonton, Alberta T6G 2E9, Canada
Wylie, Douglas R. W. and
Nathan A. Crowder.
Spatiotemporal Properties of Fast and Slow Neurons in the
Pretectal Nucleus Lentiformis Mesencephali in Pigeons. J. Neurophysiol. 84: 2529-2540, 2000. Neurons in the
pretectal nucleus lentiformis mesencephali (LM) are involved in the
analysis of optic flow that results from self-motion. Previous studies
have shown that LM neurons have large receptive fields in the
contralateral eye, are excited in response to largefield stimuli moving
in a particular (preferred) direction, and are inhibited in response to
motion in the opposite (anti-preferred) direction. We investigated the
responses of LM neurons to sine wave gratings of varying spatial and
temporal frequency drifting in the preferred and anti-preferred
directions. The LM neurons fell into two categories. "Fast" neurons
were maximally excited by gratings of low spatial [0.03-0.25
cycles/° (cpd)] and mid-high temporal frequencies (0.5-16 Hz).
"Slow" neurons were maximally excited by gratings of high spatial
(0.35-2 cpd) and low-mid temporal frequencies (0.125-2 Hz). Of the
slow neurons, all but one preferred forward (temporal to nasal) motion.
The fast group included neurons that preferred forward, backward, upward, and downward motion. For most cells (81%), the spatial and
temporal frequency that elicited maximal excitation to motion in the
preferred direction did not coincide with the spatial and temporal
frequency that elicited maximal inhibition to gratings moving in the
anti-preferred direction. With respect to motion in the anti-preferred
direction, a substantial proportion of the LM neurons (32%) showed
bi-directional responses. That is, the spatiotemporal plots contained
domains of excitation in addition to the region of inhibition. Neurons
tuned to stimulus velocity across different spatial frequency were rare
(5%), but some neurons (39%) were tuned to temporal frequency. These
results are discussed in relation to previous studies of the responses
of neurons in the accessory optic system and pretectum to drifting
gratings and other largefield stimuli.
