The effects of contrast on visual orientation and spatial frequency discrimination: a comparison of single cells and behavior

“As predicted by a linear response model, the shape of a simple cell’s orientation tuning curve is invariant to changes in stimulus contrast (Sclar and Freeman 1982; Skottun et al. 1987): a change in contrast scales all responses by a constant, rather than changing the form of the response tuning curve.”

“Although stimulus contrast is not expected to influence V1 orientation selectivity at the neuronal level (Ferster and Miller, 2000; Sclar and Freeman, 1982; Skottun et al., 1987), it is known to influence V1 BOLD response amplitude (Boynton et al.”

“…targets (Morgan & Regan, 1987; Levi, Jiang & Klein, 1990) spatial frequency discrimination (Regan, Bartol, Murray & Beverley, 1982; Thomas, 1983; Skottun, Bradley, Sclar, Ohzawa & Freeman, 1987; Bowne, 1990) and orientation discrimination (Regan & Beverley, 1985; Skottun et al., 1987; Bowne, 1990).”

“The feedforward model is challenged by the fact that spiking responses in simple cells are invariant to changes in stimulus contrast (Sclar and Freeman 1982; Skottun et al. 1987): under this model, inputs at non-optimal orientations are expected to be subthreshold at low contrast but become suprathreshold at higher co…”

“The spike sum used in this study, however, permits our findings to be compared with previous work (Heggelund and A1bus 1978; Bradley et al. 1987; Skottun et al. 1987).”

“Below, we focus on results from V1, which is best informed by neurophysiological results (Sclar and Freeman, 1982; Skottun et al., 1987; Carandini et al., 1997).”

“Both processes face the same problem: to prevent the cell from losing its response selectivity when input strength increases 46 .”

“…invariant to temporal frequency, as has been shown for stimulus contrast (Alitto and Usrey 2004; Anderson et al. 2000; Sclar and Freeman 1982; Skottun et al. 1987), this finding would indicate that the neuronal circuitry mediating the construction and maintenance of orientation tuning is…”

“For instance, orientation discrimination thresholds decrease (ie, the sensitivity increases) rapidly with contrast just above detection threshold and then levels off and remains relatively constant over the rest of the contrast range.(31) Yet, to attribute this to the magnocellular system would face the problem that n…”

“…whole story because it has difficulties with other observations, especially the contrast invariance of orientation tuning (Sclar and Freeman 1982; Skottun et al. 1987) and the effects of cortical inhibition blockade (Sillito 1975; Sillito et al. 1980; Tsumoto et al. 1979; for thorough reviews…”

“…stimuli are presented to ask an ideal observer (e.g., a single neuron or an organism) to discriminate between two stimuli that have small differences in parameters such as orientation, contrast, or spatial frequency of the visual stimulus (Thomas, 1983; Bradley et al., 1987; Skottun et al., 1987).”

“The orientation tuning bandwidth of neurons in V1 is essentially invariant with contrast (Sclar and Freeman, 1982; Skottun et al., 1987).”

“…models arose from the findings that receptive field properties, such as for example orientation and spatial frequency tuning, appeared to be contrast invariant (i.e. Albrecht & Hamilton, 1982; Bradley, Skottun, Ohzawa, Sclar, & Freeman, 1987; Sclar, Maunsell, & Lennie, 1990; Skottun et al., 1987).”

“Finally, in the nonlinear model response amplitude and orientation selectivity are unaffected by contrast and so it accounts for the contrast invariance of psychophysical orientation discrimination at suprathreshold contrasts (Bowne, 1990; Nasanen, Kukkonen, & Rovamo, 1997; Skottun et al., 1987; Smith & Thomas, 1989)…”

“…al., 1981; Sclar & Freeman, 1982; Albrecht & Hamilton, 1982; Albrecht et al., 1984; Sclar et al., 1985; Ohzawa et al., 1985; Debruyn & Bonds, 1986; Skottun et al., 1987; Vidyasagar, 1990; Bonds, 1991; Morrone et al., 1991; Geisler & Albrecht, 1992; Pfleger & Bonds, 1995; Albrecht, 1995), monkeys…”

“Why should orientation decoding improve with increased response amplitudes as measured with fMRI? Single-unit recording studies have found that higher firing rates are accompanied by a proportional increase in variance, such that increases in stimulus contrast lead to relatively small improvements in the signal-to-noi…”

“…levels of sensory stimulation (examples cited above and Bradley et al. 1987; Britten et al. 1992; Newsome et al. 1989; Parker and Hawken 1985; Skottun et al. 1987; Tolhurst et al. 1983; Vogels and Orban 1991), a major advance came when investigators began directly linking modulations in…”

“Cells were identified as simple if the amplitude of the fundamental Fourier harmonic ~F1! exceeded the elevation in mean firing rate for the stimulus that produced the maximum spike rate ~Skottun et al., 1987!.”

“Further, in cases where it has been possible to vary the neuronal response level (by varying the stimulus contrast) and to make direct comparisons between neuronal responses and psychophysical performance, it has been shown that even in the case of relatively simple tasks (such as orientation and spatial-frequency dis…”

“This prediction is wrong: the selectivity of firing-rate responses in V1 is remarkably invariant with contrast; increasing contrast does make the responses get larger, but it does not broaden their selectivity (Skottun et al., 1987).”

“…provided that the LGN-driven inhibition was stronger than the direct LGN excitation, this circuitry could account for the invariance with stimulus contrast of orientation tuning (Sclar and Freeman 1982; Skottun et al. 1987) and for a number of other intracellular and extracellular observations.”

“Well studied is also the dependence of firing rate on the stimulus orientation [10, 24], but we are not aware of studies investigating the dependence of firing irregularity on the orientation.”

“…by saturation (Robson, 1975) is largely prevented by a contrast gain control in striate cortex, which preserves the CRF shape for nonoptimal stimuli (Albrecht & Hamilton, 1982; Skottun et al., 1987; Albrecht & Geisler, 1991; Bonds, 1991; Geisler & Albrecht, 1992; Carandini & Heeger, 1994).”

“, 1998), including such functional response properties as the invariance of orientation tuning to stimulus contrast (Anderson et al., 2000b; Sclar and Freeman, 1982; Skottun et al., 1987; Troyer et al., 1998) and the temporal tuning properties of V1 cells (Krukowski and Miller, 2001).”

“This is in agreement with the contrast invariance of tuning width that was found experimentally by Sclar and Freeman (1982) and by Skottun et al (1987).”

“It is also worth noting that, in the cat, not only orientation tuning, but also spatial frequency tuning is largely independent of stimulus contrast [5,8].”

“For that purpose, we consider an example that has also been analyzed by Somers et al. (1995) and Carandini and Ringach (1997).”

“Indeed, contrast invariance is a well known and well studied feature of the visual cortex, and particularly of the V1 area [5,6].”

“This behavior can indeed be detectedin cat data (Skottun et al., 1987).”

“The Weber fraction for spatial-frequency discrimination (a form of size/separation discrimination) averages about 5% across a range of spatial frequencies (Burbeck & Regan, 1983; Caelli et al., 1983; Hirsch & Hylton, 1982; Skottun et al., 1987).”

“For example, contrast-invariant orientation tuning emerges in V1 and cannot be accounted for by the mean firing rate of the feed forward LGN relay cells, as they are not selective for stimulus orientation (Hubel and Wiesel, 1961; Skottun et al., 1987; Troyer et al., 1998).”

“…analysing the width of the orientation response function, it was suggested that contrast changes do not affect the orientation tuning of simple cells (Sclar & Freeman, 1982; Skottun et al., 1987; Heeger, 1992; Anderson et al., 2000; Ferster & Miller, 2000; Palmer & Miller, 2007; Finn et al., 2007).”

“A critical failure of the anking-suppression model is the fact spatial frequency bandwidths are invariant to changes in contrast (Albrecht and Hamilton, 1982; Skottun et al., 1987).”

“V1 neurons in WT mice exhibit similar orientation tuning at different contrasts, like in cats and monkeys (Sclar and Freeman 1982; Skottun et al. 1987; Troyer et al. 1998; Ferster and Miller 2000; Niell and Stryker 2008).”

“, the shape andwidth of orientation tuning curves remain the same for different stimulus contrasts (Sclar and Freeman, 1982; Skottun et al., 1987; Finn et al., 2007; Priebe, 2016).”

“For example, the just noticeable difference (jnd) in orientation is known to be almost independent from stimulus contrast over a large range of contrasts (Skottun et al 1987).”

“, 1994) makes it possible to establish correlations between the properties of single cells and orientation discrimination (Skottun et al., 1987; Vogels and Orban, 1990).”

“Skottun BC, Bradley A, Sclar G, Ohzawa I, Freeman RD.”

“Studies have demonstrated that the processing of higher-intensity stimulation was faster than that of lower-intensity stimulation (Glickfeld et al. 2013; Stone and Thompson 1992; Parker and Salzen 1982; Skottun et al. 1987).”

“In particular, peak and bandwidth values for orientation (Sclar and Freeman 1982) and spatial frequency (Skottun et al. 1987) remain constant at different contrast levels.”

“…tuning, with stronger selectivity at higher contrast, agreeing with monkey, cat, and ferret V1 data (Alitto & Usrey 2004; Johnson et al., 2008; Skottun et al., 1987); 3) it produced maps of cortical activity across the surface of V1 that were stable with contrast as was reported in V1 optical…”

“Similar invariance with contrast has been described for orientation tuning (Sclar & Freeman, 1982; Skottun et al., 1987).”

“Contrast-invariant V1 simple cells have been found in different mammals such as, cats [47, 48] or ferrets [49], based on sinusoidal gratings with different contrast strength.”

“(2008a) reported that the orientation tuning of S1 cortical neurons was indentation-depth invariant, similar to the contrastinvariant tuning of visual cortical neurons (Skottun et al. 1987).”

“Recurring evidence of contrast-invariant orientation tuning in V1 (Sclar & Freeman, 1982; Skottun et al. 1987; Anderson et al. 2000; Alitto & Usrey, 2004) has been used to challenge the classic Hubel and Wiesel (Hubel & Wiesel, 1962) explanation, that converging excitatory feed-forward afferents…”

“…on 07/05/2016 Experiment 1: Direct estimation from psychophysical trials The data in Skottun et al. (1987) only provides thresholds, and therefore our estimates of g(1) ¼ (n, c50) T were not obtained as in most psychophysical…”

“0 cyc/deg) and decreases to zero at higher spatial frequencies (DeAngelis, Ohzawa, & Freeman, 1993; Skottun et al., 1987).”