SCGB Boston-Area Postdoc Meeting Series

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Samberg Conference Center
50 Memorial Drive, Chang Building (E52)
Cambridge, MA 02142 United States

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Participation is by invitation only. All participants must register.

The Simons Collaboration on the Global Brain invites you to the Boston-area SCGB Postdoc Meeting. The purpose of these meetings is to bring together postdocs interested in neural coding and dynamics to discuss ideas and data. We will have two postdocs presentations, followed by dinner, drinks, and lively discussion.

The meeting is co-organized by Ali Yousefi, a postdoc at Harvard, and Sourish Chakravarty, a postdoc at MIT, and will take place at the Samberg Conference Center (6th Floor, Dining Room 3).

Hello Emily,
You are invited to the following event:

SCGB BOSTON-AREA POSTDOC MEETING SERIES
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Event to be held at the following time, date, and location:

Friday, April 26, 2019 from 6:30 PM to 9:30 PM (EDT)

Samberg Conference Center
CHANG BUILDING (E52) – 6th Floor Dining Room 3
50 MEMORIAL DRIVE
CAMBRIDGE MA

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The Simons Collaboration on the Global Brain invites you to the Boston-area SCGB Postdoc Meeting. The purpose of these meetings is to bring together postdocs interested in neural coding and dynamics to discuss ideas and data. We will have two postdocs presentations, followed by dinner, drinks, and lively discussion.

The meeting is co-organized by Ali Yousefi, a postdoc at Harvard, and Sourish Chakravarty, a postdoc at MIT, and will take place at the Samberg Conference Center (6th Floor, Dining Room 3).

The speakers are:

Emily P. Stephen

Postdoctoral Associate with Drs. Emery Brown and Patrick Purdon, MIT

Evidence that posterior and anterior phase amplitude coupling distinguish unconsciousness from unarousability in propofol anesthesia

In the last several years, a controversy has arisen regarding whether the neural correlates of consciousness are in the front or the back of the brain. The controversy has recently expanded to include studies of anesthesia-induced unconsciousness: in particular, whether frontal EEG indicators can reliably predict unconsciousness. The disagreement refers to the finding that alpha band (8-12 Hz) oscillations in frontal cortex interact differently with the slow wave depending on the depth of propofol anesthesia: at light doses, alpha power is strongest at the trough of the slow wave (troughmax) and a higher doses it is strongest at the peak of the slow wave (peakmax). Patients can be aroused from an unconscious state during frontal troughmax dynamics, but not, apparently, during peakmax dynamics.

By extending the phase amplitude coupling analysis (1) to non-frontal locations, (2) to other frequency bands beyond alpha, and (3) to the cortical surface using EEG source localization, we find that peakmax dynamics are a broadband phenomenon, suggesting that they may be reflective of cortical up- and down-states rather than coupled oscillations. In addition, posterior cortex exhibits broadband peakmax dynamics at lighter doses of propofol than frontal cortex, indicating that posterior cortical activity may be captured by cortical up- and down-states earlier than frontal cortex. This result supports the idea that loss of consciousness is not a singular phenomenon but rather involves several distinct shifts in brain state, relating to both unconsciousness and unarousability.

Kohitij Kar

Postdoctoral Associate, McGovern Institute for Brain Research, MIT (DiCarlo Lab)

Testing and improving primate ventral stream models of core object recognition

The recent progress in AI has led to the development of multiple high performing computational models that solve very similar tasks as humans, e.g., core object recognition. My current research approach is built under the premise that due to the shared behavioral goals of primates and such complex AI models, these class of models provide a formidable hypotheses space for testing neural representations and they contain the likely answers to many important questions in systems neuroscience. However, the neuroscience community often categorizes AI models of the brain as a “black-box” that is an overfit to the training data, too complicated, and too hard to comprehend — therefore not useful. In our latest study (Bashivan*, Kar* and DiCarlo, 2019, Science) we have demonstrated that, even though AI-based models of the brain are difficult for human minds to comprehend in detail, they embed knowledge of the visual brain function. With a series of closed loop neurophysiological recording and AI-based image synthesis experiments we have convincingly demonstrated that we can independently control both individual and a population of neurons in the macaque brain if we have a good neural network model of the same. The current models however are far from being perfect. So, in an attempt to study the shortcomings of such models, we compared the behavior of primates and off-the-shelf computer vision (CV) models. This led to the discovery of many images that are easy for primates but currently not solved by the CV models. Further investigation into the brain solutions for these images revealed evidence of feedback-related neural signals in the macaque inferior temporal cortex that are critical for solving these challenge images by the primates (Kar et al. 2019, Nature Neuroscience) currently unavailable in majority of the AI-based models. This study demonstrated how architectural limitations of feedforward AI systems can be exploited to gain insights into primate feedback computations. The results improve our understanding of the primate brain while providing valuable constraints for better brain-like AI. However, we do not yet know which brain circuits are most responsible for these additional, recurrent computations: circuits within the ventral stream? within IT? outside the ventral stream? all of the above? Following up on this, currently, I have developed various pharmacological and chemogenetic strategies to causally perturb specific neural circuits in the macaque brain during multiple object recognition tasks to further probe these questions and measure constraints for future models (both anatomically and functionally).

Dinner and beverages will be served. Please forward this to colleagues that you think will be interested.

*You may be eligible for transportation reimbursement to this event. Please email kscobie@simonsfoundation.org for more information.

We look forward to seeing you there!

To receive invitations for regional postdoc meetings, register here: https://goo.gl/forms/CvzxQvqiVWCwFSoN2

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