Spatial Resolution and Contrast Sensitivity of Single Neurons in Area 19 of Split‐chiasm Cats: A Comparison With Primary Visual Cortex

Abstract

Electrophysiological recordings were carried out in the callosal recipient zone of area 19 in normal and split-chiasm cats and, for comparison purposes, at the border of areas 17 and 18 of split-chiasm cats. The influences of retinothalamic and callosal inputs on a single cortical neurons were thereby evaluated. Extracellular recordings of single cells were made in anaesthetized and paralysed cats in the zone representing the central visual field. Receptive field properties were assessed using sine wave gratings drifting in optimal directions. Results showed that in area 19 and areas 17/18 one-third of the cells were binocularly driven after section of the optic chiasm. In area 19, the spatial resolution and contrast sensitivity of cells driven via the dominant eye were similar in the normal and split-chiasm groups. In areas 17/18 and area 19 of split-chiasm cats, binocular cells showed significant interocular matching of their receptive field properties (spatial resolution and contrast threshold), although small differences were observed. These small interocular differences were related to the cell's ocular dominance rather than to the signal transmission route (thalamic or callosal).

Silencing “Top-Down” Cortical Signals Affects Spike-Responses of Neurons in Cat’s “Intermediate” Visual Cortex

“…Consistent with numerous earlier reports (Hubel and Wiesel, 1965; Duysens et al, 1982a, b; Rapaport et al, 1982; Dreher, 1986; Pettigrew and Dreher, 1987; Tanaka et al, 1987; Guillemot et al, 1993; Tardif et al, 1997), area 19 neurons exhibit clear orientation selectivity (see however Saito et al, 1988). Orientation selectivity of V1 neurons relies on multiple mechanisms, including mechanisms that are intrinsic to the area as well as the orientation biased inputs from the geniculate (for reviews, see Vidyasagar et al, 1996; Vidyasagar and Eysel, 2015) and feedback signals from layer 5 (Alonso et al, 1993b) or layers 2/3 (Martinez-Conde et al, 1999) of visuotopically corresponding parts of area 18 and/or higher-order visual cortices (e.g., Wang et al, 2000, 2010; Huang et al, 2007).…”

“…In these termed end-stopped cells, stimulation of suppressive regions resulted in ≥50% reduction in the number of spikes (see hypercomplex cells of Hubel and Wiesel, 1965; see also Dreher, 1972). The proportion of end-stopped cells in our sample is at the lower end of the range reported previously (25%–38%: Hubel and Wiesel, 1965; Duysens et al, 1982b; Rapaport et al, 1982; Pettigrew and Dreher, 1987; Tanaka et al, 1987; Guillemot et al, 1993; Tardif et al, 1997; Bergeron et al, 1998; Mimeault et al, 2002). However, in the present sample, inactivation did not have a clear effect on the presence and relative strength of suppressive regions of RFs.…”

“…Consistent with previous studies (see Tusa et al, 1979; Dreher et al, 1980; Duysens et al, 1982b; Rapaport et al, 1982; Dreher, 1986; Mulligan and Sherk, 1993), the RFs located more peripherally tended to be larger (Figure 1D). As indicated in Figure 1E, the majority of cells (85.5%; 66/77) were binocular and could be activated by appropriate stimuli presented via either eye (see Duysens et al, 1982a; Rapaport et al, 1982; Dreher, 1986; Pettigrew and Dreher, 1987; Tanaka et al, 1987; Guillemot et al, 1993; Tardif et al, 1997; Bergeron et al, 1998). About half of binocular cells (53%; 35/66) responded more strongly to stimuli presented via the contralateral eye (class 2 vs. class 4 cells—Figure 1E) with only a few cells (9/66; 13.5%) responding equally well to stimuli presented via either eye (class 3 cells).…”

“…On the other hand, the proportions of simple or simple-like (see S cells, Sh cells and A cells of Henry, 1977) cells defined on the basis of existence of spatially distinct on (light bar) and/or off (dark bar) discharge regions are quite similar (25%—Dreher, 1986; Pettigrew and Dreher, 1987; to 31%—Duysens et al, 1982b) to that reported here. However, the reported proportions of simple-like cells defined on the basis of modulation ratio of the responses to moving luminance-modulated sinusoidal achromatic gratings (Skottun et al, 1991) with one exception (27%—Tanaka et al, 1987) were much lower (~10%—Tardif et al, 1997; Bergeron et al, 1998; Mimeault et al, 2002). …”

Drifting grating stimulation reveals particular activation properties of visual neurons in the caudate nucleus

“…The CN cells clearly preferred drifting gratings with extremely low spatial frequencies: the mean optimal spatial frequency of the CN cells was 0.05 c/°. This is a much lower value than those of the X and Y cells of the lateral geniculate nucleus (LGN; Saul & Humphrey, 1990; Humphrey & Murthy, 1999), the lateral posterior–pulvinar complex (LP‐Pul) of the thalamus (Casanova et al ., 1989), and almost all striate and extrastriate visual cortical areas (Movshon et al ., 1978b; Zumbroich & Blakemore, 1987; Tardif et al ., 1996, 1997; Morley & Vickery, 1997; Bergeron et al ., 1998; Nagy et al ., 2003a), but comparable with those of the SC, the W cells of the LGN and the LM‐Sg (Pinter & Harris, 1981; Saul & Humphrey, 1990; Paróczy et al ., 2006; Waleszczyk et al ., 2007; Humphrey & Murthy, 1999 Mimeault et al ., 2004).…”