First‐ and second‐order stimulus length selectivity in New World monkey striate cortex

Abstract

Motion is a powerful cue for figure-ground segregation, allowing the recognition of shapes even if the luminance and texture characteristics of the stimulus and background are matched. In order to investigate the neural processes underlying early stages of the cue-invariant processing of form, we compared the responses of neurons in the striate cortex (V1) of anaesthetized marmosets to two types of moving stimuli: bars defined by differences in luminance, and bars defined solely by the coherent motion of random patterns that matched the texture and temporal modulation of the background. A population of form-cue-invariant (FCI) neurons was identified, which demonstrated similar tuning to the length of contours defined by first- and second-order cues. FCI neurons were relatively common in the supragranular layers (where they corresponded to 28% of the recorded units), but were absent from layer 4. Most had complex receptive fields, which were significantly larger than those of other V1 neurons. The majority of FCI neurons demonstrated end-inhibition in response to long first- and second-order bars, and were strongly direction selective. Thus, even at the level of V1 there are cells whose variations in response level appear to be determined by the shape and motion of the entire second-order object, rather than by its parts (i.e. the individual textural components). These results are compatible with the existence of an output channel from V1 to the ventral stream of extrastriate areas, which already encodes the basic building blocks of the image in an invariant manner.

Neurons in monkey visual cortex detect lines defined by coherent motion of dots

“…Neurons that signalled lines from coherently moving dots were similarly selective for the orientation of these objects as for the optimal conventional stimulus. This result is similar to that found for kinetic contours (Chaudhuri & Albright, 1997; Marcar et al ., 2000; Bourne et al ., 2002, 2004; Zeki et al ., 2003). Neurons that signalled kinetic contours usually also responded to conventional stimuli and preferred similar orientations for the two types of stimulus.…”

Relationship between Size Summation Properties, Contrast Sensitivity and Response Latency in the Dorsomedial and Middle Temporal Areas of the Primate Extrastriate Cortex

“…All procedures followed the guidelines of the Australian Code of Practice for the Care and Use of Animals for Scientific Purposes . Data were collected from 18 adult New World monkeys ( Callithrix jacchus , the common marmoset), as part of a series of experiments that also included single-unit recordings from other areas, and analyses of neuronal responses to other types of stimulus [17], [28], [29], [30], [31], [32], [33]. These animals were bred for the purpose of scientific research at the Australian National Primate Facility, sponsored by the National Health and Medical Research Council.…”

“…Curve fitting was based on the entire matrix of single trial responses, rather than the mean responses to each stimulus condition. The fittings were always constrained by the requirement that the resulting curves should cross the level of spontaneous activity at zero values of length, width or contrast [29]. Both parametric and non-parametric statistical tests were used in the analyses, as specified in “Results”.…”

The marmoset monkey as a model for visual neuroscience

“…The detailed anatomy and physiology has been recently reviewed and is in most respects very similar to that of the macaque (for a recent comprehensive review, see Solomon and Rosa, 2014). Area V1 has been studied in great detail (Sengpiel et al, 1996; Webb et al, 2003; Bourne et al, 2002; Tinsley et al, 2003; Bourne et al, 2004; Forte et al, 2005; Barraclough et al, 2006; Guo et al, 2006; Zinke et al, 2006; Buzas et al, 2008; Hashemi-Nezhad, 2008; Nowak and Barone, 2009; Cheong et al, 2013; Yu et al, 2010; Yu et al, 2014; Solomon et al, 2014). Electrophysiological mapping has revealed that the visual field layout and basic neural selectivity of this area are similar to that of macaques.…”