Natural stimuli display complex spatiotemporal characteristics. In order to encode such stimuli efficiently, sensory systems must continuously adapt by changing their response properties. The computational role of such adaptation remains poorly understood because adaptation can increase coding ambiguity. We investigated how vestibular thalamocortical neurons (VTN) and their afferent input within the vestibular nuclei (VON) respond to simple artificial and complex natural selfmotion stimuli in rhesus macaques. We found that both groups displayed comparable response properties to artificial stimuli which led to ambiguity. While such ambiguity persisted for artificial stimuli for VON, VTN instead faithfully followed the timecourse of natural selfmotion stimuli. A model including gain adaptation successfully reproduced our experimental data. Our results challenge the common wisdom that adaptation leads to ambiguity by showing that such adaptation actually leads to unambiguous encoding of natural stimuli. Second, we investigated the role of these VTN in the perception of selfmotion. We tested whether their responses can account for violation of Weber's law, i.e. discrimination performance is enhanced at higher stimulus amplitudes. While neural gain decreased as a function of stimulus amplitude, neural variability saturated at high values. As a result, neural populations thresholds saturated and agreed with perception. Taken together, we provide novel insights as to how variability and gain control contribute to encoding of natural stimuli with continually varying statistics.

Gain adaptation and variability of vestibular corticothalamic neurons shape our perception of natural self motion stimuli

The transient sensations experienced by the vestibular system are critical for everyday activities such as gaze stabilization and the perception of self-motion. Accordingly, the investigation of vestibular neural coding would greatly benefit from the use of optogenetic methods; with which neuronal activity can be precisely and reliably modulated with high temporal precision. Due to our shared bipedality and close evolutionary origins, non-human primates (NHPs) are the ideal model animals. However, unlike application in invertebrates and rodents, optogenetic techniques using NHPs have not been well established, requiring researchers to infer the best approach. This project aims to provide robust results of NHP optogenetics in the vestibular system through in-vivo injection of an opsin adenovirus to key interconnected vestibular cortical and subcortical areas: the parietoinsular vestibular cortex (PIVC) and the vestibular nuclei in the brainstem of cynomolgus macaques. We can determine the efficacy and specificity of our vectors, chosen based on anatomical differences between the target regions, and evaluate opsin expression using histological methods such as immunohistochemistry and fluorescence microscopy. With the confirmation of histological expression, this project will open the door to confidently employing optogenetic methods to study vestibular electrophysiology and the behaviours it codes for, as well as to investigate feedback between our cortical and subcortical areas of interest.

Optogenetic expression in the cortical and subcortical areas of the non-human primate vestibular system

Previous studies have focused on the encoding of the first-order features of vestibular stimuli, but few studies, to date, have studied the encoding of the second-order attribute that consist of changes in vestibular stimuli amplitude or envelope. Because envelopes are critical for perception, we investigated if and how vestibular only neurons in the vestibular nuclei, known to mediate self-motion perception, encode the envelope attribute of the head motion stimulus. Specifically, we studied neural responses to stimuli consisting of a noisy waveform whose envelope varied sinusoidally at lower frequency. Importantly, stimulus amplitude was kept low such as not to elicit static nonlinearities from afferents (e.g., rectification, saturation). Our results show that the envelope attribute of the stimulus is encoded at single-neuron level in the vestibular nuclei. On average, we found that the gain of the neuron's response to the envelope remained constant across frequencies (p = 0.24). Moreover, the neuron's response shows a slight phase lead that increases as the frequency of the envelope increases (p=0.01). We found that static nonlinearities do not account for neural envelope response. Finally, we calculated the discrimination threshold and found higher values than that found in the Thalamus and for perception. Overall, our results will have important implication in our understanding of how early processing of vestibular signal can encode second-order attributes of head motion that will further be used to ensure stable perception of the world and accurate motor control.

Second-order attribute of head motion is encoded at single-neuron level in the vestibular nuclei

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PS-2-D -  Sensory and Motor Systems

poster

Colleagues and Friends:

I am very happy to welcome you to the 14th annual Canadian Neuroscience Meeting, and to the first virtual edition of our meeting. I want to highlight the important work the CAN meeting chair, **Roger Thompson** and co-chair, **Alyson Fournier**, did to put together the great program we are offering this year. Moving to a virtual format required a complete re-design of the program, and both Roger and Alyson did a splendid job in providing us with an appealing and well adapted program for our first virtual event. I wish to thank them for this very important effort.

Highlights of this year’s scientific meeting include invited speakers **Michael Hausser, Franck Polleux, Gwyneth Card, Magdalena Götz**and Brain Prize winner **Huda Zoghbi**. Plenary and parallel symposia, proposed by our members complete our diverse [scientific program.](https://can-acn.org/meeting-2021/program-2021/)

The 2021 Advocacy session, chaired and organized by CAN advocacy committee chair **Karun Singh**, will feature a special lecture and question period with Member of Parliament and past Science Minister **Kirsty Duncan**. This will be followed by a short overview of CAN’s advocacy activities over the last year. We invite you to participate in this session for insight from Dr. Duncan on the workings of Parliament Hill, and to learn more about what CAN has been doing to promote neuroscience research in Canada.

We are also excited to host **Lisa Willis** in the Equity Diversity and Inclusion session, organized by EDI committee chair **Jibran Khokhar**.

A special highlight of our meeting will be the lectures by award-winning young neuroscientists. We are please to host the CAN 2020 Young Investigator Award winner **Mihaela Iordanova**, and CAN 2021 Young Investigator Award winners **Aaron Phillips** and **Tabrez Siddiqui**. Highlights will also include presentation by the top three winners of the CAN-CIHR-INMHA Brain Star Award winners, **Claire Gizowski, Nuria Daviu Abant** and **Lukas Tamayo-Orrego**.

Independently organized satellite symposia complement and complete this exciting program, check them out here: https://can-acn.org/meeting-2021/2021-satellite-symposia/

Some of the most engaging sessions are always the poster sessions featuring the work of our trainees, so make sure to log in to Gather Town during the poster sessions to chat with the presenters.
We hope you enjoy this program, and look forward to welcoming you, virtually.

Shernaz Bamji

President of the Canadian Association for Neuroscience

![](https://assets.underline.io/uploads/markdown_image/1/image/b9aea25343a87d5aac3b9367dc780974.jpg)



Jerome Carriot

3

SHORT BIO

Presentations

Gain adaptation and variability of vestibular corticothalamic neurons shape our perception of natural self motion stimuli

Optogenetic expression in the cortical and subcortical areas of the non-human primate vestibular system

Second-order attribute of head motion is encoded at single-neuron level in the vestibular nuclei

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