Spatiotemporal tuning of directional neurons in mammalian and avian pretectum: a comparison of physiological properties

Abstract

Responses were recorded from 72 neurons in the wallaby's nucleus of the optic tract (NOT) during stimulation with drifting sinusoidal gratings at a range of temporal and spatial frequencies (TF and SF). Most cells (70/72) were TF tuned, but two were velocity tuned. The neurons are placed into two descriptive groups: fast and slow cells, which prefer SF/TFs of 0.06-0.6 cpd/0.4-20 Hz and 0.13-1 cpd/<1 Hz, respectively. The peak spatiotemporal tunings of the neurons are compared for motion in preferred and anti-preferred directions with little variation observed in most cases. The spatiotemporal properties of wallaby NOT are compared with those of pigeon lentiformis mesencephali: the avian homologue of NOT. The neurons in the pigeon and wallaby nuclei segregate into fast and slow cells that operate in similar spatiotemporal domains. The fast and slow cells segregate largely on the basis of TF in wallabies and SF in pigeons, but their respective velocity tuning properties are very similar. In both species, the mean velocity tuning for fast and slow cells is approximately 50 degrees/s and 1 degrees/s, respectively.