This reminds us that there are many pathways outside the 'main' one to primary visual cortex (V1) that can function after V1 lesions. Some can even deliver conscious visual experiences. For example, conscious motion vision sometimes survives (aka Riddoch phenomenon) www.youtube.com/watch?v=9ABQ... - ThreadSky

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action-brain.bsky.social • 91 days ago

This reminds us that there are many pathways outside the 'main' one to primary visual cortex (V1) that can function after V1 lesions. Some can even deliver conscious visual experiences. For example, conscious motion vision sometimes survives (aka Riddoch phenomenon) https://www.youtube.com/watch?v=9ABQ-U6V0tY

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nataliepeluso.bsky.social•91 days ago

Yes! but it's the conscious or phenomenological experience of visual attributes for features normally processed beyond V1 which is unusual... I wonder if the seeing these patients describe is akin to mental imagery?

action-brain.bsky.social•90 days ago

There are inputs to visual cortical areas beyond V1 that receive input directly from the interlaminar regions of the LGN and indirectly from the superior colliculus (via the pulvinar). These and other intact pathways could mediate conscious experience and/or unconscious visually driven behavior.

michaelanes.bsky.social•88 days ago

I associate (some time ago now) Ramachandran with popularizing the notion of an SC to MT pathway subserving blindsight (on a PBS Nova program I think - I show it to my cog lab class) but don’t recall the story of the original research supporting that claim.

action-brain.bsky.social•88 days ago

Here's a recent paper showing that selective and reversible blockade of the pathway from SC to pulvinar impairs spared visually-guided saccades in macaques with V1 lesions. The Introduction cites several early studies investigating the putative SC-Pulv-MT pathway.
https://www.nature.com/articles/s41467-018-08058-0

nataliepeluso.bsky.social•88 days ago

Yes, thanks Mel, that's a good one - I've recommended the same paper to my students 🙂

action-brain.bsky.social•90 days ago

I might add though that your conjecture about the relationship between the phenomenology of patients with V1 lesions and imagery is interesting.

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