The Effect of Temporal Modulation on Image Recognition
Abramov, Israel
City University of New York
2019
116
Ph.D.
City University of New York
2019
A primary goal of vision is to identify objects rapidly and efficiently. Successful object and scene recognition results from the integration of both feed-forward and feedback processes that correspond a two-dimensional retinal image to a representation of its content stored in memory (Bar, 2003). One general organizing principle may be that the visual system analyzes images and scenes according to their spatial components in a coarse- (low spatial frequency) to-fine (high spatial frequency) sequence (Bullier, 2001; Hegde, 2008). An individual's sensitivity to these spatial components is described by contrast sensitivity function (CSF), which indicates the minimum contrast required for the detection of patterns of various sizes. A consistent finding is that, when temporally modulated at a moderate rate, sensitivity to lower spatial frequency gratings is heightened relative to its static counterpart (Robson, 1966; Abramov et al., 2012). This suggests that temporal modulation may enhance image detectability, especially so for those coarsest spatial components-the lower spatial frequencies-that seem to be most important for detection and categorization of objects and scenes. We presented participants with an array of grayscale images depicting objects and scenes under 3 spatial (3cpd-filtered, 4cpd-filtered, and unfiltered full-spectrum) and 3 temporal (static, 6Hz counterphase flicker, and 250ms presentation) conditions, at 4 levels of near-threshold contrast. Responses were open-ended identifications. Temporal modulation was hypothesized to improve recognition in all spatial conditions, while short-duration presentation was predicted to result in performance comparable to the full-duration static condition. Males were hypothesized to perform better than females based on previously reported (Abramov, et al., 2012) sensitivity differences. Results partially supported our hypotheses: temporal modulation at 6Hz had recognition enhancement effects only for the lowest spatial frequency-cutoff-3 cpd. We describe a distinction among the neurological underpinnings of the CSF into two separate mechanisms responsible for the lower and upper halves of the CSF.