Learning to see

How do we learn to see? Proper visual experience during the first weeks and months of life is critical for the proper development of the visual system. But how does experience modify neural circuits so that they exhibit the proper responses to visual stimuli? Knowledge of the mechanisms by which the brain is constructed early in development should inspire new therapies for repairing the brain if it develops improperly or is damaged by disease or injury.

At the present time, it is not possible to directly view all or even most connections within a living neural circuit. Therefore, neuroscientists often build computational models to study how these circuits may be constructed and how they may change with experience. A good model allows scientists to understand how these circuits may work in principle, and offers testable predictions that can be examined in the living animal to either support or refute the model.

Undergraduate Ian Christie ’16 was interested in understanding how neural circuits in the ferret visual system become selective to visual motion. At the time of eye opening, neurons in ferret visual cortex respond to an object moving in either of two opposite directions. With about a week of visual experience, each neuron develops a preference for only one of these directions, and greatly reduces its responses to the opposite direction.

Previous models of this process posited that the primary source of the change was in the organization and pattern of inputs to the cortex. But, recent experiments from the Van Hooser lab (Roy/Osik/Ritter et al., 2016) showed that stimulating the cortex by itself was sufficient to cause the development of motion selectivity, which suggests that some changes within the cortex itself must be underlying the increase in selectivity, at least in part. Further, other experiments in the lab of former Brandeis postdoc Arianna Maffei (Griffen et al., 2012) have shown that the cortex becomes less excitable to focal stimulation over the first weeks after eye opening.

Ian constructed families of computational models that could account for both of these observations. In the model, columns of neurons in the cortex already receive input that is slightly selective for motion in one of two opposite directions, but the connections between these cortical columns are so strong that both columns respond to both directions. However, the activity that is caused by simulated visual experience activates synaptic plasticity mechanisms in the model, that served to greatly reduce the strength of these connections between the columns, allowing motion selectivity to emerge in the cortical columns. The project was supervised by faculty members Paul Miller and Stephen Van Hooser, and the results were published in Journal of Neurophysiology (Christie et al., 2017).

Future experiments will now look for evidence of weaker connectivity between cortical neurons with visual experience.

This work was supported by the “Undergraduate and Graduate Training in Computational Neuroscience” grant to Brandeis University from NIH, and by the National Eye Institute grant EY022122. It also used the Brandeis University High Performance Computing Cluster.

IGERT Video Poster Competition Voting Open

Tony Ng (a grad student in Paul Miller’s lab in Neuroscience) writes:

I’m entering a nationwide video/poster competition organized by the National Science Foundation (NSF) under the IGERT program.  There are over 100 three-minute-videos/posters in the competition.  The videos/posters are divided into 18 fields, all of which are multidisciplinary.  Mine covers cognition/biology/physics.

The competition has a Public Choice award.  Winning the award requires Facebook “likes” on my page.  I need on the order ~1000 “likes” to be in contention.  The bar has been raised from last year’s.  The competition is fierce.  Each/every vote from the Brandeis community counts!

The competition opens today (5/21) and ends Thursday (5/23) at 10pm.  For a vote to count, it is imperative to click on the “Public Choice” button, which would then trigger a Facebook “like” sign-in.  Anyone with an existing Facebook account can contribute.

Here’s the link to my 3-minute video/poster:

http://posterhall.org/igert2013/posters/402

Act now! Tthe competition closes on Thursday at 10pm!

Hope you enjoy the videos!

Update (2 pm):

Andrew Russell from the Petsko-Ringe lab also has a poster in the competition on studying Aβ oligomers to understand Alzheimer’s Disease – check it out — vote early, vote often?

http://posterhall.org/igert2013/posters/416

Dynamic Coding in Neural Signals Workshop on July 29

The Center of Excellence for Learning in Education, Science and Technology (CELEST) is holding a workshop on its cross-function initiative Dynamic Coding in Neural Signals at Boston University (677 Beacon Street, Room B02) on July 29, 2011. from 1:00 – 5:45 pm. The workshop is free and open to the public. There will be talks by invited speakers from 1 – 4:15, including presentations by Don Katz (“Perceptual processing via coherent sequences of ensemble states”) and Paul Miller (“Stochastic transitions between discrete states in models of taste processing and decision-making”). a student and postdoc poster session will follow, with ample opportunity for discussion between presenters and workshop attendees.

CELEST is a joint venture of scientists at four Boston-area universities including Brandeis and is sponspored by the National Science Foundation. Robert Sekuler, Louis and Frances Salvage Professor of Psychology at Brandeis, is a co-Principal Investigator, and Biology and Neuroscience faculty Gina Turrigiano and Paul Miller are also involved in the center.

New in Pubmed

Have no time to write News and Views, but there are a few new papers from our labs that have recently popped up in Pubmed.

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