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Updated: Mar 1, 2026

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Published on: February 8, 2020
Numerosity processing in early visual cortex.
Michele Fornaciai1, Elizabeth M Brannon2, Marty G Woldorff3
1Department of Psychological and Brain Sciences, University of Massachusetts Amherst, USA.
Early visual cortex, specifically areas V2 and V3, processes numerical information (numerosity) within 90ms. This finding challenges the parietal cortex
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Visual Perception
Background:
- Parietal cortex is traditionally linked to numerical magnitude representation.
- Previous event-related potential (ERP) studies suggest early visual cortex involvement in numerosity processing.
- The precise brain region responsible for early numerosity sensitivity remains unidentified.
Purpose of the Study:
- To determine if numerosity-sensitive neural signatures originate from the initial stages of the visual cortex.
- To localize the generator of early numerosity processing signals.
- To investigate the role of early visual areas V2 and V3 in numerosity perception.
Main Methods:
- Utilized event-related potentials (ERPs) to measure neural responses to dot arrays.
- Presented dot arrays (8-32 dots) in either the upper or lower visual hemifields.
- Analyzed ERP polarity inversion patterns to infer the location of neural generators.
Main Results:
- Neural responses around 90ms post-stimulus were significantly sensitive to numerosity.
- A distinct polarity inversion pattern in numerosity-sensitive activity at ~90ms suggested generation in V2 and V3.
- Later numerosity-sensitive activity (210-230ms) in occipito-parietal channels lacked polarity inversion, indicating dorsal stream involvement.
Conclusions:
- Numerosity processing initiates in early visual cortical areas, specifically V2 and V3.
- This challenges the notion that numerical magnitude representation is solely a function of later parietal processing.
- The findings highlight the role of early visual processing in fundamental numerical cognition.
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