A physiological analysis of subcortical and commissural projections of areas 17 and 18 of the cat.

Abstract

1. The corticotectal, corticothalamic and commissural projections of areas 17 and 18 of the cat have been examined using electrical stimulation techniques. 2. In both area 17 and area 18, almost all corticotectal neurones are C cells and have binocular receptive fields. Some of these cells respond equally well to both small moving spots and elongated stimuli, while others only respond to stimuli of restricted length (cf. Palmer & Rosenquist, 1974). Both types are highly direction-selective. A third type of corticotectal C cell responds optimally to long edges or bars and shows only weak direction selectivity. Corticotectal cells generally have fast conducting axons and the majority are encountered in lamina V. About 25% of all cells recorded in lamina V can be antidromically activated from the superior colliculus. 3. Striate and parastriate cells efferent to the thalamus can have either S or C type receptive fields. Corticothalamic S cells are the most common type of efferent cell in lamina VI and have more slowly conducting axons than C cells. Efferent S cells are almost always direction-selective and about half have binocular receptive fields. 4. It is suggested that there may be at least three subgroups within the corticothalamic cells: lamina V C cells project to the pulvinare complex (the same cells may also send axons to the superior colliculus), lamina VI C cells project to the perigeniculate nucleus and lamina VI S cells provide the cortical input to neurones within the lateral geniculate nucleus. 5. In contrast to the corticotectal and corticothalamic projections, the receptive fields of cells projecting through the corpus callosum forth a heterogenous group. All major striate and parastriate receptive field classes are efferent to the contralateral cortex. Their receptive field centres are located close to the vertical mid line and most cells respond best to stimuli moving towards the ipsilateral visual hemifield. Efferent neurones are mostly encountered in lamina III, within about 1mm either side of the 17-18 border zone. 6. Cells orthodromically excited after commissural stimulation have mostly C or B type receptive fields. Unlike efferent callosal neurones, orthodromically activated cells are encountered up to 3 mm into area 18 and can have receptive fields located up to 9 degrees from the vertical mid line. 7. The results are discussed with regard to the possible functional significance of each of the corticofugal pathways.

An intracellular analysis of geniculo‐cortical connectivity in area 17 of the cat.

“…(Gilbert, 1977;Harvey, 1980b;Tsumoto & Suda, 1980). This suggestion was not confirmed by the present experiments.…”

Electrically Evoked Responses in Onset Chopper Neurons in Guinea Pig Cochlear Nucleus

“…Collision has traditionally been used to confirm that a shock-evoked spike is antidromically conducted to the cell body (for explanation see Bishop et al 1962;Harvey 1980). This situation is illustrated in Fig. 2A.…”

“…We used extracellular recording from cochlear nucleus neurons to obtain detailed characterization of neuronal type and combined this with midline electrical stimulation at a location known to activate MOCS axons. The nature of spikes evoked in cochlear nucleus neurons by such electrical stimulation was investigated using an extension of the classical collision technique (Bishop et al 1962;Harvey 1980).…”

Directional asymmetries in the length‐response profiles of cells in the feline dorsal lateral geniculate nucleus.

“…However, work from our laboratory has already shown that the length tuning of dLGN cells is in fact strongly influenced by the feedback projection from the visual cortex (Murphy & Sillito, 1987;Sillito, Cudeiro & Murphy, 1993). This projection arises from orientationtuned cells in layer VI of the visual cortex (Gilbert, 1977;Harvey, 1980) and each dLGN cell seems to be influenced by a complete subset of the orientation columns representing that location in visual space (Sillito et al 1993). Interestingly the properties of this feedback effectively generate orientation-tuned end-zones (Sillito et al 1993).…”