Spikes are usually initiated at the axon initial segment (AIS), the most excitable site of a neuron. Yet other regions of the neuron are also excitable. While there are many studies on somatic and dendritic excitability, axon excitability has yet to be thoroughly investigated in most neurons because the small size of the axon precludes intracellular recordings. Using a novel optogenetic approach, recent experiments from our lab have shown that axon spikes transiently in response to sustained depolarization. Although the optogenetic method has many advantages, it still has some limitations: first, light is not focused on one point, meaning stray light may hit other regions of the neuron; second, since voltage changes are recorded from the soma, the location of spike initiation must be inferred indirectly. These experimental limitations necessitated simulations to definitively interpret the experimental results. We built a multicompartment model of a CA1 pyramidal neuron with a detailed myelinated axon that reproduced our experimental data. The model confirmed the site of spike initiation based on the shape (kinkiness) of spikes recorded in the soma. Simulations also confirmed that even when targeting the axon for photostimulation, a small degree of stray light can hit the dendrites and evoke spikes in the AIS. The results ultimately confirm that the AIS spikes repetitively during sustained depolarization, consistent with analog to digital transduction of information, whereas the axon responds with transient spiking only during abrupt changes in depolarization. Simulations show that the stimulus the axon receives during spike propagation is a very intense and short depolarization, which is precisely the input to which it is tuned to respond.

Transient spike initiation supports digital information transfer in axons: simulations in a biophysically detailed model

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PS-2-B -  Neural Excitability, Synapses, and Glia: Cellular Mechanisms

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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

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Nooshin Abdollahi

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Transient spike initiation supports digital information transfer in axons: simulations in a biophysically detailed model

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