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TL;DR

Distinct synaptic connections cortex->pulvinar = distinct oscillatory patterns. Significant implications for visual processing in the cortex, especially for attention.

Context

The pulvinar, thalamic nucleus, is right next to the lateral geniculate nucleus (LGN). Size of the pulvinar correlates with neocortex expansion throughout mammalian evolution [1]. Hence, pulvinar being the largest nucleus of primates’ thalamus. Unique extensive (and reciprocal) synaptic connections with all visual cortical areas.

Synaptic connections from cortex to pulvinar not uniform. Differ by cortical origin. Low-level areas (e.g., V1) cause post-synaptic depression; higher-level areas (e.g., V4) cause post-synaptic facilitation [2].

Takeaways

We created a spiking neural network model of the pulvinar. Studied effects of varying synapse types on pulvinar activity.

Model showed V4 and V1 projections have opposing effects on the pulvinar’s state. Alpha oscillatory state from V1 input shifts to non-oscillatory spiking activity with V4 input, and vice versa.

With direct cortical connectivity in the model, V1-generated alpha oscillations in the pulvinar propagate to V4. V4 synaptic activity transitions system to non-oscillatory state, closing the oscillation loop.

Relevance

Canonical view: visual processing in the cortex as hierarchical communication. Our paper: alpha oscillations - typically seen as high-to-low level feedback/attention can travel opposite direction through the pulvinar.

References

[1] Hutchins, B., & Updyke, B. V. (1989). Retinotopic organization within the lateral posterior complex of the cat. Journal of Comparative Neurology, 285(3), 350-398.

[2] Abbas Farishta, R., Boire, D., & Casanova, C. (2020). Hierarchical organization of corticothalamic projections to the pulvinar. Cerebral Cortex Communications, 1(1).

On a personal note

First peer-reviewed paper. Exciting milestone!\