Abstract
The apparent size of visual stimuli depends on where in the visual field they appear. We recently presented a model of how size perception could be biased by stimulus encoding in retinotopic cortex. However, it remains unclear if such perceptual biases are instead trivially related to discrimination ability and if they are temporally stable. An independent test of the model is also still outstanding. Here, I show that perceptual biases are stable across stimulus durations between 50 and 1,000 milliseconds, even though discrimination ability unsurprisingly improves with duration. Furthermore, perceptual biases are stronger along the vertical than the horizontal meridian, which mirrors reported differences in spatial vision and the positional selectivity of early visual cortex. Taken together, these findings support our model of how size is inferred from cortical responses.
Highlights
Our impression of a seamless and accurate perception across our visual field belies the fact that the neural representation of the visual field is highly heterogeneous
We showed that idiosyncratic spatial patterns in population receptive field (pRF) spread correlate with the spatial heterogeneity of size perception biases across the visual field
Using Multiple Alternatives Perceptual Search (MAPS) (Figure 1(a)), I tested how perceptual biases and discrimination ability depended on stimulus duration
Summary
Our impression of a seamless and accurate perception across our visual field belies the fact that the neural representation of the visual field is highly heterogeneous. The apparent size of stimuli decreases in the periphery (Anstis, 1998; Bedell & Johnson, 1984; Newsome, 1972), where its spatial location is encoded less precisely in retinotopic cortex, as measured by population receptive field (pRF) spread (Dumoulin & Wandell, 2008; Moutsiana et al, 2016; Smith, Singh, Williams, & Greenlee, 2001). We showed that idiosyncratic spatial patterns in pRF spread correlate with the spatial heterogeneity of size perception biases across the visual field. This model could explain both decreases and increases in apparent size under different stimulus conditions (Moutsiana et al, 2016)
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