Tomas Knapen

Investigating individual-specific topographic organization has traditionally been a resource-intensive and time-consuming process. But what if we could map visual cortex organization in thousands of brains? Here we offer the community with a toolbox that can do just that! tinyurl.com/deepretinotopy

Our team's new publications cover the Nature portfolio! 🧪🧠

- Vision & touch (Nature, rdcu.be/eSsZR)
- Psychedelics (Nat Commun, rdcu.be/eSsZ2)
- Binocular rivalry (Nat Hum Behav, rdcu.be/eSsYW)
- CSF mobility (Nat Neurosci, rdcu.be/eSs0c)
- Numerical cognition (Commun Biol, rdcu.be/eSs0p)

Vicarious body maps bridge vision and touch in the human brain - Nature A mode of brain organization that connects visual and bodily reference frames may translate raw sensory impressions into more abstract formats that are useful for action, social cognition and semantic processing.

Nature research paper: Vicarious body maps bridge vision and touch in the human brain

go.nature.com/4839zaL

Massive congratulations to lead author @HedgerResearch, and co-authors Thomas Naselaris and @cvnlab .
Read the open-access paper here 👇
bit.ly/VisualBodyMaps

#Neuroscience #BrainMapping #VicariousTouch

This provides a mechanistic basis for everyday vicarious experiences — like flinching when you see someone fall — but the implications go far deeper:
• Social cognition
• Sensory and clinical neuroscience (e.g., ASD)
• Embodied AI & AGI development

The core discovery:
Visual cortex isn’t purely visual — it’s tiled with orderly somatotopic maps, aligned with the maps in primary somatosensory cortex.
Seeing recruits the same body-based computational machinery you use to feel your own body. x.com/HedgerResear...

New today in @Nature: your visual cortex contains touch-based body maps. bit.ly/VisualBodyMaps
Your brain transforms what you see into first-person, body-referenced codes: A previously unknown bridge between vision and touch.

On the nose

Very proud of Marco’s work in this project!

The paper demonstrating that #psilocybin alters contextual computations is out in @natcomms.nature.com : doi.org/10.1038/s414...

Thanks to the reviewers and coauthors : @marcoaqil.bsky.social , @tknapen.bsky.social , @gillesdehollander.bsky.social , and Nina Vreugdenhil

pRF fitting toolbox wish list With this form we are taking stock of the field's wishes when it comes to pRF fitting software implementations. We will be presenting the results from this form in our kick-off meeting, and will use t...

Hey everyone at @vssmtg.bsky.social! If you’re interested in pRF fitting, go visit Garikoitz Lerma-Usabiaga’s poster on pRF fitting methods!

For our development of these tools, we’re very interested to hear you want in these tools. Please fill out our questionnaire:

forms.gle/fx5UMs1362jv...

𝘗𝘦𝘳𝘴𝘰𝘯, 𝘴𝘵𝘢𝘯𝘥𝘪𝘯𝘨 𝘰𝘯 𝘵𝘩𝘦 𝘣𝘦𝘢𝘤𝘩 𝘥𝘰𝘪𝘯𝘨 𝘺𝘰𝘨𝘢, 𝘴𝘵𝘢𝘯𝘥𝘪𝘯𝘨 𝘰𝘯 𝘰𝘯𝘦 𝘧𝘰𝘰𝘵, 𝘸𝘪𝘵𝘩 𝘰𝘯𝘦 𝘩𝘢𝘯𝘥 𝘰𝘯 𝘵𝘩𝘦 𝘨𝘳𝘰𝘶𝘯𝘥, 𝘤𝘰𝘯𝘵𝘰𝘳𝘵𝘦𝘥 𝘪𝘯 𝘢𝘯 𝘶𝘯𝘶𝘴𝘶𝘢𝘭 𝘢𝘯𝘥 𝘤𝘩𝘢𝘭𝘭𝘦𝘯𝘨𝘪𝘯𝘨 𝘱𝘰𝘴𝘦, 𝘸𝘩𝘪𝘭𝘦 𝘤𝘰𝘯𝘵𝘦𝘮𝘱𝘭𝘢𝘵𝘪𝘯𝘨 𝘵𝘩𝘦 𝘪𝘥𝘦𝘢 𝘵𝘩𝘢𝘵 𝘨𝘦𝘯𝘦𝘳𝘢𝘵𝘪𝘷𝘦 𝘈𝘐 𝘩𝘢𝘴 “𝘸𝘰𝘳𝘭𝘥 𝘮𝘰𝘥𝘦𝘭𝘴”

A thread motivated by a new paper on body representations in the human brain at a fine-grained (multi-unit) level, spearheaded by J Garcia Ramirez, T Theys, and P Janssen, where I was a small part of a bigger collaboration that also included S Bracci, R Murty and @nancykanwisher.bsky.social. 1/n

And people sampling the videos with their eyes allows them to shape their own brain responses. This will likely generate an additional level of “individuality” to brain responses, lowering ISC

Our results indicate the brain uses aligned, 'multiplexed' topographic maps to structure connections between vision and somatosensation. The computational machinery classically attributed to the somatosensory system is embedded within/aligned with that of the "visual" system. 🧵

These findings complement recent work indicating that dorsolateral visual cortex is a fundamentally multi-sensory part of the brain whose role extends beyond passive visual analysis to encompass semantic and bodily information relevant to interactions with the world. 20/n

These encoding model fits revealed a new map of visual body-part selectivity, which overlapped with somatotopic tuning across the FBA, EBA and, strikingly, the visual word form area (VWFA). 19/n

To address this, we combined the Natural Scenes Dataset with a pose-detection algorithm fit a body-part tuning encoding model. This allowed us to generate a map of visual body part preference, organised along a similar toe-to-tongue axis as the somatotopic connectivity maps. 18/n

Much of visual cortex is body-part selective. If this tuning relates to our somatotopic connectivity, we should also be able to predict visual body part selectivity from somatotopic tuning and reveal multi-modal body-referenced alignment playing out at more semantic levels. 17/n

We did indeed find evidence for an alignment between visual field tuning and body part tuning beyond that expected by chance. We found this mostly dorsally and in the superior portion of EBA. 16/n

But do these bodily maps predict anything about visual function? For instance, could lower body part tuning (e.g. toes) predict lower visual field tuning? Such an alignment might facilitate interactions with the environment. 15/n

Yes! Throughout dorsolateral visual cortex, we see several body-part gradients separated by reversals. These maps were consistent across hemispheres and subject splits. 14/n

But what about the body part tuning of these somatotopic activations? Do these dorsolateral regions exhibit orderly gradients, as found in 'core' somatosensory regions around the central sulcus? The answer is... 13/n

We then repeated our somatosensory connectivity analyses separately on a movie section involving human agents and another without any humans. This demonstrated that somatotopic responses are not generic, but driven by movie content, specifically that featuring human action. 12/n

Our analysis allows us to contrast somatotopic and retinotopic explained variance. All dorsolateral (but not ventral!) visual regions were characterised by multimodal topographic connectivity. These regions care as much or more about the body as they do the visual scene! 11/n

We find that movie watching led to increased somatotopic connectivity in the somatosensory network outlined above. But strikingly, we now also find that dorsolateral visual cortex has structured connectivity with S1. Look at that red band across visual cortex! 10/n

So, we turned to the HCP movie watching experiment. This dataset allows us to investigate the relation of somatosensory connectivity to naturalistic visual experiences, where mental content is yoked to a visual stimulus. 9/n

So, during resting state, endogenous activations throughout frontal, parietal, and insular cortex resonate along scaffolding provided by the somatotopic structure of bodily sensations. But how this resonance relates to mental content in resting state is unclear... 8/n

Body part tuning revealed multiple somatotopic gradients and body-part tuning biases that are typically only revealed by exogenous stimulation (e.g. brushing people). Critically, we show that these same detailed principles can be revealed in the absence of sensory input! 7/n