SCGB NY-Area Postdoc Meeting

The Simons Collaboration on the Global Brain hosts a postdoc-focused NYC-area group meeting every other month to bring together postdocs interested in neural coding and dynamics, to discuss ideas and data.

PLEASE NOTE THE LOCATION AND TIME: 162 5th Ave, 3rd Floor, in the Flatiron Institute, 5:30 pm

The meeting is co-organized by Adam Calhoun (Princeton) and Jorge Jaramillo (NYU). The speakers this month are:

Alice Mosberger
Zuckerman Mind Brain Behavior Institute, Columbia University

Action discovery and refinement in the mouse forelimb

When an exploratory movement leads to reward, credit is assigned to certain dimensions of the movement, which are repeated over time – refining the action. To study this process, we have developed a head-fixed task, in which mice use their forelimb to move an unrestricted planar joystick. Through exploration of the 2D space, mice learn to move the joystick from a set start position to a reinforced target area in an uncued and self-paced manner. Over several sessions, animals learn to achieve high hit rates (repetition), while trajectories become less tortuous, more similar to each other, and show decreased directional variability (refinement). Once the mice reach high performance, the location of the target is changed, requiring them to explore the 2D space again, discover the new target, and refine a new action. Further, by unexpectedly shifting the start position of the joystick, I am investigating motor control strategies and allocentric/egocentric type target location encoding.

The corticostriatal network is hypothesized to implement this type of action learning through reinforcement by integrating sensorimotor information and outcome signals in the striatum. Thereby allowing assignment of credit to the relevant movement dimensions at corticostriatal synapses. Two distinct neuronal classes project from cortex to striatum that could convey such information: intratelencephalic and pyramidal tract neurons. For mouse forelimb circuitry, viral tracing shows that these cells are distributed across widespread cortical areas with specific localization profiles. I am using 2-photon calcium imaging of this anatomically characterized corticostriatal forelimb circuitry to identify dynamics of action discovery, repetition, and refinement through reinforcement.

Katie Ferguson
Yale University School of Medicine

Inhibitory Contributions to Cortical Circuit Dynamics

Visual information from the environment is rapidly and dynamically processed by a complex network of cortical neurons. Cortical activity patterns reflect not only changing sensory inputs, but also behavioral state (e.g., quiet wakefulness vs. active locomotion). Several lines of evidence suggest that inhibitory GABAergic interneurons (INs) may be key regulators of flexible cortical function. However, cortical GABAergic INs comprise several reciprocally connected, highly diverse subpopulations that are differentially activated during distinct states.

GABAergic INs expressing vasoactive intestinal peptide (VIP-INs) are strongly activated by neuromodulatory afferents during distinct behavioral states, and are thus uniquely situated to be key contributors to flexible cortical function. These cells predominantly inhibit somatostatin expressing interneurons (SST-INs), but until recently methodological limitations prevented the study of IN-IN interactions in vivo. The relative impact of these highly non-linear cortical interactions may vary with behavioral or environmental context, and thus VIP-SST interactions may have a complex and largely unexplored role in the regulation of cortical activity.

We use two-photon calcium imaging in awake behaving mice to identify cell type-specific GABAergic IN contributions to sensory processing, to determine how behavioral state modulates the impact of GABAergic inhibition, and to identify how distinct GABAergic IN populations regulate the correlational structure of visually evoked activity. Our results uncover underlying state-dependent excitation of SST-INs and suggest a complex role for VIP-INs in regulating large-scale changes to sensory processing across behavioral states.

Schedule:

Dinner and beverages will be served. Please forward this to colleagues that you think will be interested. We look forward to seeing you there!