Brisk and sluggish concentrically organized ganglion cells in the cat's retina

Abstract

1. Nine hundred and sixty cat retinal ganglion cells were evaluated with respect to receptive‐field organization and latency to antidromic activation of their axons from optic‐tract and mid‐brain positions. 2. The vast majority (92%) had the familiar concentric centre/surround organization. As in earlier work these could be classed as sustained or transient, independently of the centre type. About 13% of the concentric cells were characterized by relatively sluggish responses to conventional visual stimuli which yielded brisk responses from the others. The sluggish cells constituted a previously unspecified class of concentric receptive fields. 3. The responses of brisk and sluggish cells to a variety of stimuli were described with a view to developing procedures for distinguishing them on functional grounds. 4. Measurements of latency to antidromic activation of retinal axons confirmed earlier work in showing that cells classed as brisk‐transient had the shortest conduction times from the optic tract. Cells classed as brisk‐sustained had intermediate conduction times and from earlier work would constitute an important input to the lateral geniculate nucleus. A proportion of the brisk‐sustained axons reached the pretectal region (especially on‐centre types) and a small minority reached the superior colliculus (especially off‐centre types). 5. Sluggish cells had generally slower antidromic conduction times; despite some overlap with the brisk‐sustained class, the slower conduction provided independent support for the functional differentiation. Sluggish axons reached the pretectal region and superior colliculus. 6. The brisk‐sustained cells constituted the majority of the recordings in the area centralis. 7. A comparison with the morphological data of Boycott & Wässle is made which suggests that the brisk‐transient units corresponded with α cells, the brisk‐sustained with β cells, and the sluggish units were included amongst the γ cells.