Distinct neural representational geometries of numerosity in early visual and association regions across visual streams
Abstract Visual numerosity, traditionally linked to the parietal cortex, is now thought to be represented across a broader cortical network, including early visual and associative areas in both streams. However, how numerosity is encoded relative to other visual features remains unclear. We conducte...
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| Format: | Article |
| Language: | English |
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Nature Portfolio
2025-07-01
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| Series: | Communications Biology |
| Online Access: | https://doi.org/10.1038/s42003-025-08395-z |
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| author | Alireza Karami Elisa Castaldi Evelyn Eger Manuela Piazza |
| author_facet | Alireza Karami Elisa Castaldi Evelyn Eger Manuela Piazza |
| author_sort | Alireza Karami |
| collection | DOAJ |
| description | Abstract Visual numerosity, traditionally linked to the parietal cortex, is now thought to be represented across a broader cortical network, including early visual and associative areas in both streams. However, how numerosity is encoded relative to other visual features remains unclear. We conducted a whole-brain functional magnetic resonance imaging (fMRI) study with thirty-one adults performing a numerosity estimation task on visual sets varying in number, item size, total item area, field area, and density, ensuring tight stimulus control. Using model-based representational similarity analyses, we found numerosity represented independently of other visual properties in early visual areas and amplified in retinotopic and non-retinotopic associative regions across both streams. Dimensionality reduction of BOLD patterns revealed distinct geometries: a one-dimensional representation of numerical rank in early visual and ventral retinotopic areas, and a curved structure encoding rank and distance-to-endpoints in associative dorsal and ventral regions. These results demonstrate distinct neural coding schemes for numerosity across cortical regions. |
| format | Article |
| id | doaj-art-57816ba3479741b28b2a6eb8d383a7a5 |
| institution | DOAJ |
| issn | 2399-3642 |
| language | English |
| publishDate | 2025-07-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Communications Biology |
| spelling | doaj-art-57816ba3479741b28b2a6eb8d383a7a52025-08-20T03:05:56ZengNature PortfolioCommunications Biology2399-36422025-07-018111310.1038/s42003-025-08395-zDistinct neural representational geometries of numerosity in early visual and association regions across visual streamsAlireza Karami0Elisa Castaldi1Evelyn Eger2Manuela Piazza3Center for Mind/Brain Science, University of TrentoDepartment of Neuroscience, Psychology, Pharmacology and Child Health, University of FlorenceCognitive Neuroimaging Unit, CEA DRF/Joliot, INSERM, Université Paris-Saclay, NeuroSpin CenterCenter for Mind/Brain Science, University of TrentoAbstract Visual numerosity, traditionally linked to the parietal cortex, is now thought to be represented across a broader cortical network, including early visual and associative areas in both streams. However, how numerosity is encoded relative to other visual features remains unclear. We conducted a whole-brain functional magnetic resonance imaging (fMRI) study with thirty-one adults performing a numerosity estimation task on visual sets varying in number, item size, total item area, field area, and density, ensuring tight stimulus control. Using model-based representational similarity analyses, we found numerosity represented independently of other visual properties in early visual areas and amplified in retinotopic and non-retinotopic associative regions across both streams. Dimensionality reduction of BOLD patterns revealed distinct geometries: a one-dimensional representation of numerical rank in early visual and ventral retinotopic areas, and a curved structure encoding rank and distance-to-endpoints in associative dorsal and ventral regions. These results demonstrate distinct neural coding schemes for numerosity across cortical regions.https://doi.org/10.1038/s42003-025-08395-z |
| spellingShingle | Alireza Karami Elisa Castaldi Evelyn Eger Manuela Piazza Distinct neural representational geometries of numerosity in early visual and association regions across visual streams Communications Biology |
| title | Distinct neural representational geometries of numerosity in early visual and association regions across visual streams |
| title_full | Distinct neural representational geometries of numerosity in early visual and association regions across visual streams |
| title_fullStr | Distinct neural representational geometries of numerosity in early visual and association regions across visual streams |
| title_full_unstemmed | Distinct neural representational geometries of numerosity in early visual and association regions across visual streams |
| title_short | Distinct neural representational geometries of numerosity in early visual and association regions across visual streams |
| title_sort | distinct neural representational geometries of numerosity in early visual and association regions across visual streams |
| url | https://doi.org/10.1038/s42003-025-08395-z |
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