Visual adaptation reveals non-opponent multichannel coding for numerosity
Year: 2020
Type: article
Abstract: Visual numerosity is represented automatically and rapidly, but much remains unknown about the computations underlying this visual encoding. Although it has been suggested that numerosity is represented with opponent-channel coding, where all values are represented by the relative activity of two pools of neurons (i.e., those tuned to small and large numerosities), in contrast to multichannel coding where all values are represented directly (with separate pools of neurons for each numerosity), this suggestion has not been systematically investigated. Using adaptation, we assessed whether visual encoding of numerosity is better characterized by an opponent-channel or multichannel system. Critically, these systems make distinct predictions regarding the pattern of after-effects exhibited when adapted to an intermediate numerical value (50 dots). Opponent-channel coding predicts no after-effects because both pools of neurons adapt equally. By contrast, multichannel coding predicts repulsive after-effects, wherein numerical values smaller than the adapter are underestimated and those larger than the adapter are overestimated. Importantly, even if 50 does not reflect a perceptually intermediate value within the approximate number system, an opponent channel system nonetheless predicts symmetrical after-effects, regardless of the numerical range presented, contra the predictions for a multichannel system. Consistent with multichannel coding, adaptation to an intermediate value (50 dots) yielded repulsive after-effects. Specifically, participants underestimated stimuli ranging from 10-50 dots (Exp. 1A), and overestimated stimuli ranging from 50-250 dots (Exp. 1B). Taken together, these findings provide novel evidence that the visual encoding of numerosity is supported by a multichannel, not opponent-channel, coding system and raise important questions regarding the contributions of different cortical regions, such as the ventral and lateral intraparietal areas, to the representation of numerosity (Nieder & Merten, 2007; Roitman et al., 2007).
Source: Journal of Vision
Authors: Lauren Aulet, Stella Lourenco
Institution: Emory University
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $1,850
OpenAlex ID: W3096796938