@DegenRolf

##### Conversation[Rolf Degen](https://x.com/DegenRolf)[@DegenRolf](https://x.com/DegenRolf) The primary visual cortex, the receiving station for optical information in the higher brain, is not required for creating visual mental imagery. A long-standing assumption in cognitive neuroscience is that visual mental imagery is “visual perception in reverse” and, as such, requires reactivation of the primary visual cortex (V1). \[The primary visual cortex at the back side of the higher brain is like the receiver in a TV set because it takes raw, encoded signals transmitted from an outside source and decodes them into a coherent image that the rest of the brain can interpret.\] \[It is thought that\] visual mental imagery draws on the same machinery as vision: neural activity originates in prefrontal regions and ultimately re-enters primary visual cortex. On this view, total destruction of V1 should abolish visual mental imagery and provoke neurological aphantasia. We tested this prediction by reviewing 55 published cases of cortical blindness in which visual mental imagery abilities were assessed. Our first conclusion is straightforward and, given the size of the dataset, well supported: vivid visual mental imagery can be spared despite complete or near-complete bilateral destruction, disconnection, or functional loss of V1. The cases with the clearest anatomical or functional evidence of near-total V1 loss—all show preserved or even normal imagery, including structured imagery assessment. This pattern is difficult to reconcile with the dominant view that V1 is necessary for detailed imagery. Consistent with the present findings, many neuroimaging studies failed to find V1 activation during imagery. The V1-necessity hypothesis is also physiologically implausible if it treats V1 as a stable “mental screen.” Despite precise retinotopy, V1 does not provide a static picture of the visual field: retinal input is continually displaced by saccades, microsaccades, drifts, and tremors, and stabilized retinal images rapidly fade from awareness. Conscious visual content is therefore more plausibly supported by higher-level visual representations coordinated with frontoparietal control systems. The clinical record of cortical blindness, now spanning 136 years and 55 reviewed cases, does not support the view that primary visual cortex is necessary for visual mental imagery [View quotes](https://x.com/DegenRolf/status/2070728007447192050/quotes)[Cube Flipper](https://x.com/cube_flipper)[@cube\_flipper](https://x.com/cube_flipper) [3h](https://x.com/cube_flipper/status/2070902434029883821) do you think it might reside in LGN instead?[63](https://x.com/cube_flipper/status/2070902434029883821/analytics) ##### Discover more Sourced from across X The results of a 2024 study are among a growing number suggesting the heartbeat quietly shapes how the brain processes information. These findings also raise the uncomfortable possibility that internal rhythms frequently treated as background noise may be subtly skewing results [[image]](https://x.com/ScienceMagazine/status/2070545651960606871/photo/1)