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Colloquium Series 2022-2023

Colloquia are generally on Tuesdays at 2:30 p.m., once per month. For the first two talks of Fall 2022 they will be online (links forthcoming). We anticipate a return to live events imminently. If you'd like to be on the mailing list announcing these events, please sign up here.


Here is a list of our speakers for the 2022-2023 (this will be updated as additional speakers are scheduled).

Fall 2022 Term

Oct 25 14:30 Adrien Peyrache (McGill)

Title:

The origin of symmetry: Reciprocal feature encoding by cortical excitatory and inhibitory neurons.  

Abstract: In the cortex, the interplay between excitation and inhibition determines the fidelity of neuronal representations. However, while the receptive fields of excitatory neurons are often fine-tuned to the encoded features, the principles governing the tuning of inhibitory neurons are still
elusive. We addressed this problem by recording populations of neurons in the postsubiculum (PoSub), a cortical area where the receptive fields of most excitatory neurons correspond to a specific head-direction (HD). In contrast to PoSub-HD cells, the tuning of fast-spiking (FS) cells, the
largest class of cortical inhibitory neurons, was broad and heterogeneous. However, we found that PoSub-FS cell tuning curves were often
fine-tuned in the spatial frequency domain, which resulted in various radial symmetries in their HD tuning. In addition, the average frequency
spectrum of PoSub-FS cell populations was virtually indistinguishable from that of PoSub-HD cells but different from that of the upstream
thalamic HD cells, suggesting that this population co-tuning in the frequency domain has a local origin. Two observations corroborated this
hypothesis. First, PoSub-FS cell tuning was independent of upstream thalamic inputs. Second, PoSub-FS cell tuning was tightly coupled to
PoSub-HD cell activity even during sleep. Together, these findings provide evidence that the resolution of neuronal tuning is an intrinsic
property of local cortical networks, shared by both excitatory and inhibitory cell populations. We hypothesize that this reciprocal feature
encoding supports two parallel streams of information processing in thalamocortical networks.

Nov 1 14:30 Yalda Mohsenzadeh (Western)

Talk Title: Understanding, Predicting, and Manipulating Image Memorability with Representation Learning

Abstract: Everyday, we are bombarded with hundreds of images on our smart phone, on television, or in print. Recent work shows that images
differ in their memorability, some stick in our mind while others are fade away quickly, and this phenomenon is consistent across people. While it
has been shown that memorability is an intrinsic feature of an image, still it’s largely unknown what features make images memorable. In this
talk, I will present a series of our studies which aim to address this question by proposing a fast representation learning approach to modify and
control the memorability of images. The proposed method can be employed in photograph editing applications for social media, learning aids, or
advertisement purposes.

Dec 6 14:30 Leyla  Isik (Johns Hopkins) Virtual on Zoom

Title: The neural computations underlying real-world social interaction perception


Abstract: Humans perceive the world in rich social detail. We effortlessly recognize not only objects and people in our environment, but also social interactions between people. The ability to perceive and understand social interactions is critical for functioning in our social world. We recently identified a brain region that selectively represents others’ social interactions in the posterior superior temporal sulcus (pSTS) in a manner that is distinct from other visual and social processes, like face recognition and theory of mind. However, it is unclear how social interactions are processed in the real world where they co-vary with many other sensory and social features. In the first part of my talk, I will discuss new work using naturalistic movie fMRI paradigms and novel machine learning analyses to understand how humans process social interactions in real-world settings. We find that social interactions guide behavioral judgements and are selectively processed in the pSTS, even after controlling for the effects of other co-varying perceptual and social information, including faces, voices, and theory of mind. In the second part of my talk, I will discuss the computational implications of social interaction selectivity and present a novel graph neural network model, SocialGNN, that instantiates these insights. SocialGNN reproduces human social interaction judgements in both controlled and natural videos using only visual information, but requires relational, graph structure and processing to do so. Together, this work suggests that social interaction recognition is a core human ability that relies on specialized, structured visual representations. 



Colloquium Series 2021-2022

Colloquia are generally on Tuesdays at 2:30 p.m., once per month. For the Fall 2021 they will be online (link to be provided shortly). We anticipate a return to live events in Winter 2022 (formerly held in E5-6111). Abstracts are posted as available. If you'd like to be on the mailing list announcing these events, please sign up here.


Here is a list of our speakers so far for the 2021 and 2022 academic year:

Winter 2022 Term

Feb 22 Richard Naud (U Ottawa)

March 8 Mayank Mehta (UCLA)

Title: From virtual reality to reality: How neurons make maps

A part of the brain called the hippocampus is thought to be crucial for learning and memory and implicated in many incurable disorders ranging from Autism to Alzheimer's. Hence, it is crucial to understand how the hippocampus works. Decades of research shows that hippocampal damage in humans causes loss of episodic or autobiographical memory. But, such memory traces in hippocampal single neurons are hard to find. Instead research in the rodent hippocampus shows that the neurons encode spatial maps, or place cells. Place cells are common in rodents but rare in humans or nonhuman primates. These major discrepancies have hampered not only scientific progress, but also diagnosis and treatment of major disorders including ADRD. I will share our findings using virtual reality that address these questions and provide surprising answers that can significantly advance translation of basic science to treatments.

Karim Jerbi (UdeM)

April (TBD) We are rescheduling in hope of doing this live and in-person.

(titles, abstracts, and times to follow)


Fall 2021 Term

Kohitij Kar MIT

Lyle Muller Western

Andreas Burkhalter Washington University St. Louis


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Sue Ann Campbell Presents at International Conference on Mathematical Neurosci 2022

Sue Ann Campbell (Applied Math/CTN core member) recently presented "Modulation of Synchronization by a Slowly Varying Current"  in July 2022 at the International Conference on Mathematical Neuroscience; Watch it on YouTubesue ann campbell presentation image of spikes

CTN Research Day Sept 27 15:00-17:30 DWE 3516

The Centre for Theoretical Neuroscience will be hosting its first Research Day. This will be a chance to start the new academic year by getting re-acquainted with each other and the diversity of research conducted by CTN core and affiliate faculty. The format will be to have a number of CTN faculty share short overviews of their lab's and projects (15:00-16:00) and then, following a short coffee break (16:00-16:30), hear from a dozen current graduate students and post-docs giving short three minute talks on an aspect of their current research (16:30-17:30).

Bots and Beasts. New book by CTN Founding Member Paul Thagard

Paul Thagard, philosopher, cognitive scientist, Killam prize winner, and founding CTN member has a new book out: Bots and Beasts. bots and beasts book cover