Calendar

Center for Memory and Brain and the Systems Neuroscience Group

Symposium November 16, 2012  1:00 PM – 5:00 PM

Sargent College, Room 102, 635 Commonwealth Avenue

“New directions in behavioral and systems neuroscience”

Speakers:

Professor Alla Karpova, HHMI/Janelia Farm Research Campus

Title: Network Resets in the medial prefronal cortex mark the onset of behavioral uncertainty. Abstract: The ability of animals to display behavioral flexibility is thought to depend on an internal representation of the environment – a framework of beliefs that can be adjusted on the basis of experience. How beliefs are encoded remains unclear.  Some models posit only gradual updates to the internal representation, while others invoke abrupt jumps, or resets, in representation. Such resets may occur after a significant environmental change has been detected, causing prior information to be discarded. The environment is then re-sampled to construct a new internal representation. Sudden transitions from the pursuit of a single behavioral option to exploration have been described, supporting the notion that old beliefs can be abandoned in favor of a state of ‘knowing nothing’. Evidence that reset-like network dynamics accompany abrupt changes in beliefs is lacking, however. We have recorded neural ensemble activity from the medial prefrontal cortex (mPFC) of rats trained to perform a novel task that provides a readout of the transition to exploration and permits abrupt changes in encoding to be attributed to changes in the animal’s internal state. We detect abrupt and coordinated changes in neural activity across a large fraction of sampled neurons at moments when confidence in the existing representation of the task declines and sampling of alternative strategies is initiated. These transitions reflect network switches to a state of instability that gradually diminishes over the period of exploration, as a new stable representation is formed. Our results support the view that mPFC network activity tracks belief about the state of the world.

Professor Tony Zador Cold Spring Harbor Laboratory

Title: Cortical circuits underlying auditory circuits
Abstract: The neural pathways by which information about the acoustic world reaches the auditory cortex are well characterized, but how auditory representations are transformed into motor commands is not known. Here
we have used a perceptual decision-making task to study this transformation. I will describe results indicating that neurons in the auditory cortex that project to the auditory striatum play an unexpectedly important role in auditory decisions.  Striatal projections are widespread in cortex and may provide a general mechanism for the control of motor decisions by sensory cortex.

Professor Dmitry Rinberg, HHMI, Janella Farm

Title:  Timing in the Sense of Smell
Abstract:  Our nose can identify thousands of individual odors and group mixtures of odors into specific percepts. An odor is recognized independently of its concentrations and other background odors. A lot is known about an initial step of information processing: odors are sensed by a large family of olfactory receptors. Each odor excites multiple receptors and each receptor is activated by multiple odors. Information about the external world is transmitted to the brain in a combinatorial fashion.  How is this information processed by the brain?
To understand the principles of olfactory processing we studied temporal structure of neuronal code and timing of animal olfactory behavior. We recorded activity of mitral/tufted cells, the first recipient of odor information after receptors in the olfactory bulb of an awake mouse. We found that in spite of general intuition that the processing of olfactory information is slow, the temporal representation of odors in the brain is temporally very precise.
Is this observed temporal precision of the neuronal code relevant to further information processing? We proposed the model how such temporally precise code can be read by higher brain areas – olfactory cortices, and presented behavioral experiments demonstrating that such temporal resolution is accessible by animal at the perceptual level.

David W. Tank, Princeton University

Title:  TBD