11 July 2022 - Research

The Farrow lab reports how integration of brain-wide information in the superior colliculus allows for flexibility in innate responses to visual threats

The Farrow lab put its latest results on how pathway-specific inputs to the superior colliculus can lead to flexible innate behaviours on the biorxiv pre-print server.

The work was done by Chen Li and Norma Kühn, together with Ilayda Alkislar, Arnau Sans Dublanc, Firdaouss Zemmouri, Soraya Paesmans and co-senior authors Katja Reinhard and Karl Farrow.

Animals are born with a collection of instinctive and stereotypic behaviours, for example freezing or escape in response to danger. Still, these instinctive behaviors can be remarkably flexible.

The superior colliculus plays a crucial role in processing visual information from the retina to mediate such innate behaviours; however, how other, brain-wide inputs to the superior colliculus are organised to modulate visual processing and enable flexible behavior remains unknown. To determine these rules, the team led by Karl Farrow focused on inhibitory projection (Gad2) neurons in the mouse superior colliculus.

“Trans-synaptic tracing and neuronal recordings revealed that Gad2 neurons projecting to the dorsal lateral geniculate nucleus (LGd) and the parabigeminal nucleus (PBG) form two separate anatomical and functional populations, where each circuit received a different set of non-retinal inputs,” says Chen Li, co-first author on the study. “For example, the Gad2-PBG circuit receives more motor and touch info, and Gad2-PBG neurons are more strongly modulated by locomotion.”

Bioarxiv Farrow Lab

“Inhibiting LGd or PBG projecting Gad2 neurons resulted in opposing effects on behaviour; increasing freezing or escape, respectively; and activation of selected inputs to each circuit caused similar behaviour changes consistent with which pathway they innervated. ,” adds Norma Kühn, the other co-first author.

Farrow: “This work lays out a circuit design principle that enables the independent adjustment of the feed-forward transfer of visual threat in different output pathways of the superior colliculus to produce context specific behavior.”

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