Temporal-frequency tuning of direction selectivity in cat visual cortex

Abstract

Responses of 71 cells in areas 17 and 18 of the cat visual cortex were recorded extracellularly while stimulating with gratings drifting in each direction across the receptive field at a series of temporal frequencies. Direction selectivity was most prominent at temporal frequencies of 1-2 Hz. In about 20% of the total population, the response in the nonpreferred direction increased at temporal frequencies of around 4 Hz and direction selectivity was diminished or lost. In a few cells the preferred direction reversed.One consequence of this behavior was a tendency for the preferred direction to have lower optimal temporal frequencies than the nonpreferred direction. Across the population, the preferred direction was tuned almost an octave lower. In spite of this, temporal resolution was similar in the two directions. It appeared that responses in the nonpreferred direction were suppressed at low frequencies, then recovered at higher frequencies.This phenomenon might reflect the convergence in visual cortex of lagged and nonlagged inputs from the lateral geniculate nucleus. These afferents fire about a quarter-cycle apart (i.e. are in temporal quadrature) at low temporal frequencies, but their phase difference increases to a half-cycle by about 4 Hz. Such timing differences could underlie the prevalence of direction-selective cortical responses at 1 and 2 Hz and the loss of direction selectivity in many cells by 4 or 8 Hz.

Surround Suppression of V1 Neurons Mediates Orientation-Based Representation of High-Order Visual Features

“…This is in contrast to responses of the CRF to luminance gratings, for which about half of the neurons show the index Ͼ0.5 (DeAngelis et al 1993). Although we examined the direction selectivity at low temporal frequencies (0.5 and 0.75 Hz), many V1 neurons show direction selectivity for conventional luminance gratings at these rates (Saul and Humphrey 1992). Therefore it is unlikely that the center-surround interactions are strongly involved in motion processing for the contrast borders.…”

Does Corticothalamic Feedback Control Cortical Velocity Tuning?

“…Intracortical circuits can in principle even generate their own direction selectivity by selectively inhibiting responses to nonpreferred motion Suarez et al, 1995;Maex & Orban, 1996). Our modeling is complementary to the latter in that we emphasize the influence of geniculate inputs on cortical RF properties that is suggested by numerous studies (Saul & Humphrey, 1992a;Saul & Humphrey, 1992b;Reid & Alonso, 1995;Alonso et al, 1996;Ferster et al, 1996;Toth et al, 1997;Jagadeesh et al, 1997;Murthy et al, 1998;Hirsch et al, 1998), in order to bring out effects that are specific to the geniculate contribution to spatiotemporal tuning.…”

“…The layout of geniculate inputs ( Figure 2B) matches the basic structure of a single on-or off-region in an RF of a directional simple cell in cortical layer 4B onto which the GRCs are envisaged to project (Saul & Humphrey, 1992a;Saul & Humphrey, 1992b;DeAngelis et al, 1995;Jagadeesh et al, 1997;Murthy et al, 1998). To complete the geniculate input to a RF of this type, this lagged-nonlagged unit would have to be repeated with alternating on-off-polarity and a spatial offset that would determine the simple cell's preference for some spatial frequency.…”

“…At least for simple cells in layer 4B, this RF structure determines the response to moving visual features (McLean & Palmer, 1989;McLean et al, 1994;Reid et al, 1991;Albrecht & Geisler, 1991;DeAngelis et al, 1993;DeAngelis et al, 1995;Jagadeesh et al, 1993;Jagadeesh et al, 1997;Murthy et al, 1998), and hence the cell's tuning for direction and speed 1 . Lagged and nonlagged inputs that converge, either directly or via other cortical neurons, on simple cells and segregate in separate subregions of the simple cells' RF are thus likely to contribute to the earliest level of cortical velocity selectivity (Saul & Humphrey, 1990;Saul & Humphrey, 1992a;Saul & Humphrey, 1992b;Ferster et al, 1996; 1 To avoid confusion, we point out that the term 'speed tuning' is sometimes used in a more restricted sense. Simple cells exhibit tuning for spatial and temporal frequencies that results in preference for speeds of moving gratings depending on their spatial frequency.…”

Speed Selectivity in V1: A Complex Affair

“…Along these lines, the direction selectivities of some neurons in cat area 17 have been reported to vary with temporal frequency (Saul and Humphrey, 1992) and contrast (Peterson et al, 2006). It remains to be determined whether speed-tuned macaque V1 neurons display these inconsistencies.…”