Tangential high-density electrode insertions allow to simultaneously measure neuronal activity across an extended region of the visual field in mouse superior colliculus

Abstract

The superior colliculus (SC) is a midbrain structure that plays a central role in visual processing. Although we have learned a considerable amount about the function of single SC neurons, the way in which sensory information is represented and processed on the population level in awake behaving animals and across a large region of the retinotopic map is still largely unknown. Partially because the SC is anatomically located below the cortical sheet and the transverse sinus, it is technically difficult to measure neuronal activity from a large population of neurons in SC. To address this, we propose a tangential recording configuration using high-density electrode probes (Neuropixels) in mouse SC in vivo that permits a large number of recording sites (~200) accessibility inside the SC circuitry. This approach thereby provides a unique opportunity to measure the activity of SC neuronal populations composing up to ~2 mm of SC tissue and characterized by receptive fields covering an extended region in the visual field. Here we describe how to perform tangential recordings along the anterior-posterior and the medio-lateral axis of the mouse SC in vivo and how to combine this approach with optogenetic tools for cell-type identification on the population level.

Efficient mapping of the thalamocortical monosynaptic connectivityin vivoby tangential insertions of high-density electrodes in cortex

“…To ensure the tangential insertion of the Neuropixels probe through the cortical layers 4, and the quantity of TCA in the recording, we strongly advise to look at RF mapping and TCA waveforms plotting together. To do so, the short sparse noise stimulus was displayed and the neuronal activity recorded 22 . The first main verification is to use an adaptation of the “make_fig.m” script from Kilosort (Extended Data Fig.…”

“…1c purple area). Second , a more classical online analysis will confirm the placement of the probe in the visually driven channels by mapping receptive fields (RF) as published recently by the lab 22 .…”

“…To do so, the short sparse noise stimulus was displayed and the neuronal activity recorded 22 . The first main verification is to use an adaptation of the "make_fig.m" script from Kilosort (Extended Data Fig.…”

“…The analysis used for the visualization of putative TCAs is available on the laboratory GitHub repository 23 . Furthermore, the online analysis used to represent the visually driven MUA activity has been published in a separate publication 22 .…”