All events, All years

A hierarchy of temporal receptive windows in human cortex

Lecture
Date:
Tuesday, February 12, 2008
Hour: 12:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Dr. Uri Hasson
|
New York University

Real-world events unfold at different time scales, and therefore cognitive and neuronal processes must likewise occur at different time scales. In the talk I will present a novel procedure that identifies brain regions responsive to the preceding sequence of events (past time) over different time scales. The fMRI activity was measured while observers viewed silent films presented forward, backward, or piecewise-scrambled in time. The results demonstrate that responses in different brain areas are affected by information that has been accumulated over different time scales, with a hierarchy of temporal receptive windows spanning from short (~4 s) to intermediate (~12 s) and long (~ 36 s). Thus, although we adopted an open-ended experimental protocol (free viewing of complex stimuli), we found that parametric manipulation of the temporal structure of a complex movie sequence produced lawful changes in cortical activity across different brain regions. In addition to the reliable cortical response patterns, I will also show that films exerted considerable control over the subjects' behavior (i.e., eye movements or galvanic skin responses). Finally, I will present few applications of this method for studying the neuronal correlates of complex human behaviors under more natural settings.

Information-theoretic analysis of neural data: why do it, why it is challenging, and what can be learned

Lecture
Date:
Tuesday, February 5, 2008
Hour: 12:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Jonathan Victor
|
Cornell University

Entropy and information are quantities of interest to neuroscientists, because of their mathematical properties and because they place limits on the performance of a neural system. However, estimating these quantities from neural spike trains is much more challenging than estimating other statistics, such as mean and variance. The central difficulty in estimating information is tightly linked to the properties of information that make it a desirable quantity to estimate. To surmount this fundamental difficulty, most approaches to estimation of information rely (perhaps implicitly) on a model for how spike trains are related. But the nature of these model assumptions vary widely. As a result, information estimates are useful not only in situations in which several approaches provide mutually consistent results, but also in situations in which they differ. These ideas are illustrated with examples from the visual and gustatory systems.

Consequences of the uncertainty principle of measurement for perception and action

Lecture
Date:
Wednesday, January 30, 2008
Hour: 13:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Dr. Sergei Gepshtein
|
Brain Science Institute, RIKEN, Japan The Salk Institute for Biological Studies, USA

What can we learn from the octopus about the evolution of neural system for learning and memory?

Lecture
Date:
Tuesday, January 29, 2008
Hour: 12:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Dr. Binyamin Hochner
|
Hebrew University, Jerusalem

The octopus is an active hunter, a remarkable invertebrate whose complex behaviors rely on exceptionally good visual and tactile senses coupled with highly advanced learning and memory (LM) abilities. Studying the octopus LM system may therefore reveal characteristics universally important for mediation of complex behaviors. We developed slice and isolated brain preparations of the LM area in the octopus brain to characterize the short- and long-term neural plasticity. The importance of these processes for LM are been tested in behavioral experiments. The results support the importance of LTP in behavioral LM and suggest new ideas regarding the organization of short- and long-term memory systems.

Decoding neural signals for the control of movement

Lecture
Date:
Tuesday, January 22, 2008
Hour: 12:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Sara Solla
|
Northwestern University

The activity of neurons in primary motor cortex provides the signals that control our ability to execute movements. One of the crucial questions, still unresolved, is that of identifying the coordinate system used in the execution of movements: is it an Euclidean representation of the external space, or an actuator representation of the state of the muscles? We address this question through the analysis of data obtained for an awake behaving monkey. The data includes simultaneous recording of the activity of about one hundred neurons in motor cortex and of the activity of about ten muscles in the relevant limb. The analysis of this data involves a variety of techniques, from linear regression models to nonlinear methods for dimensionality reduction. I will review the current level of achievement in this active area of research and discuss its implications, both for understanding aspects of neural information processing that relate to natural behaviors and for extracting from these neural signals the information needed to guide prosthetic limbs and other types of external devices.

Cortical Maps, Dyanamic Innformation Processing and Perception

Lecture
Date:
Monday, January 21, 2008
Hour: 13:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Christopher Moore
|
McGovern Institute for Brain Research, MIT

I am interested in how neural dynamics, changes in neural sensitivity on the time scale of milliseconds to seconds, support rapid changes in perceptual capability. Our key focus is in testing the hypothesis that dynamics in early sensory cortices, such as the primary somatosensory cortex, play a key role in perception. To examine these issues in a model where detailed invasive studies are possible, we study the vibrissa sensory system of rodents. To examine the broader relevance of these findings, we have a smaller parallel effort I human perception and imaging. A variety of our studies suggest that. In this seminar, I will describe work we have done to understand the 'natural scene' of vibrissa perception, the signals that are generated during active surface contact. I will then describe how these signals are encoded in 2 recently discovered cortical maps, a frequency map, shaped by the resonance properties of the vibrissae, and a direction map, encoding the angle of vibrissa motion. I will then discuss why having these cortical feature columns, with adjacent neurons sharing similar computational processing, may enhance information processing. Specifically, I will argue that this arrangement facilitates dynamic regulation of neural sensitivity by neuromodulators that have a more course spatial precision, on the order of 300-1000 microns. I will briefly mention the hemo-neural hypothesis, the proposal that changes in blood flow and volume may be one source of neural regulation on this spatial scale. I will then describe an example of the dynamic regulation of spatial activation across a cortical map, resulting from adaptation during robust thalamocortical input at 5-25 Hz. I will argue that this adaptation leads to a transition into a state that is enhanced for discrimination of alternative stimuli, but impoverished for detection of novel stimuli (decreased sensitivity). To test the hypothesis that these kinds of cortical dynamics in the primary somatosensory cortex regulate perception, I will describe human MEG experiments showing that changes in the amplitude of SI activation regulate detection probability, and showing that these changes in perception and cortical amplitude are predicted by ongoing rhythmic activity in human SI at 5-25 Hz (the 'mu' rhythm).

Neural Circuits Underlying Sexually Dimorphic Social and Reproductive Behaviors

Lecture
Date:
Wednesday, January 16, 2008
Hour: 12:00
Location:
Dolfi and Lola Ebner Auditorium
Dr. Tali Kimchi
|
Department of Molecular and Cellular Biology Harvard University

My long term interest lies in the mechanistic understanding of sensory processes underlying behavioral responses in laboratory as well as natural wild environments. External sensory cues control complex behaviors such as mating, predator avoidance or orientation in space that are essential for the animal survival and the propagation of the species. In rodents, pheromones play a major role in controlling innate social and sexual responses including mating, nursing and aggression. However, although these behaviors display striking sexual dimorphisms, surprisingly few anatomical and molecular features have been identified that differentiate the male from the female brain. Using genetic and behavioral tools, I have shown that the vomeronasal organ (VNO), an olfactory sensory organ in the nasal cavity of many mammals which detects pheromones, is responsible for the control of male- and female-specific social and sexual behaviors. Amazingly, female mice in which the VNO has been genetically or surgically inactivated engage in male-typical courtship and sexual behaviors including mounting, pelvic thrusting and courtship vocalization, that are indistinguishable from that of normal male mice. These findings suggest a model in which male and female circuits that regulate innate reproductive behaviors exist in the brain of both sexes, while a sex-specific chemosensory network enables pheromonal cues to control the sex-specificity of behavior. To gain a deeper understanding of the molecular and neuronal processes underling sex-specific innate behaviors my lab will combine molecular and genetic tools, together with unique behavioral approaches, to study animal behavioral responses under natural ethologically relevant conditions. Furthermore, to uncover novel VNO-mediated pheromone responses that might have degenerated or been suppressed in inbred laboratory mouse lines, wild-caught mouse strains will be studied in wide range of behavioral, genetically and physiological assays.

Who's Afraid of Chaotic Networks? Model of Sensory and Motor Processing in the Face of Spontaneous Neuronal Activity

Lecture
Date:
Tuesday, January 15, 2008
Hour: 12:15
Location:
Jacob Ziskind Building
Prof. Larry Abbott
|
Columbia University

Large, strongly coupled neural networks tend to produce chaotic spontaneous activity. This might appear to make them unsuitable for generating reliable sensory responses or repeatable motor patterns. However, this is not the case. Inputs can induce a phase transition, leading to responses uncontaminated by chaotic "noise". Likewise, appropriately trained feedback units can control the chaos, resulting in a wide variety of repeatable output patterns. These issues will be discussed accompanied by examples and demonstrations.

Beyond Hebbian Plasticity – A Dynamic View of Memory Processing

Lecture
Date:
Monday, January 14, 2008
Hour: 13:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Karim Nader
|
Psychology Dept, McGill University, Montreal

Memory scientists have been inspired and directed for decades in their search for brain mechanisms mediating learning and memory by the postulates of D.O. Hebb. Two of Hebb's most influential postulates include that co-incident activation of pre-and post-synaptic cells could be a mechanism for learning (Hebbian/associative long term potentiation). In addition once a memory is aquired, it initially exists in a fragile, labile state, after which it becomes stabilized/consolidated in the brain. While these postulates have been incredibly influential and largely correct, the data suggests it is may be time to move beyond these postulates. Data will be presented to demonstrate that synapses may not be sensitive to co-incidence of pre- and post-synaptic activation, rather they may be sensitive to probability of their co-activation. Second, we demonstrate that even old consolidated memories return to a labile state when they are remember, and must be reconsolidated in order to persist. This suggests that the traditional Consolidation Hypotheses, including Hebb's postulates, are no longer sufficient to explain the data.

Motor learning with unstable neural representations

Lecture
Date:
Wednesday, January 9, 2008
Hour: 11:30
Location:
Wolfson Building for Biological Research
Dr. Uri Rokhni
|
MIT

It is usually assumed that the brain learns by changing neural circuits that are otherwise stable. However, recent experiments in monkeys show that the neural representation of movement in motor cortex is continually changing even without learning, when practicing a familiar task. We set to investigate the reason for these changes. We analyzed the empirical data and found that the changes are slow and random. We constructed a theoretical model of a cortical network that learns a motor skill by changing synaptic strengths. Our model explains how the network can change its synaptic strengths, and neural activity, without changing the motor behavior. Additionally, our model replicates the observed changes when synaptic learning is assumed highly noisy. We speculate that this noise serves to explore different synaptic configurations during learning.

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Common mechanisms mediate synapse formation during development and synapse plasticity during learning and memory

Lecture
Date:
Monday, July 30, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Samuel Schacher
|
Center for Neurobiology & Behavior, Columbia University College, New York, NY

"The Effects of Age-Related Morphologic Changes

Lecture
Date:
Sunday, July 29, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Dr. Doron Kabaso
|
Department of Biomathematical Sciences Mount Sinai School of Medicine, New York, NY, USA

:3.14" A Constant That is Fundamental to Visual Cortex Design"

Lecture
Date:
Wednesday, July 18, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Fred Wolf
|
Research Group Theoretical Neurophysics Max Planck Institute for Dynamics and Self-Organization Gottingen, Germany

Circadian clocks in the limbic forebrain:

Lecture
Date:
Tuesday, July 10, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Shimon Amir
|
Concordia University Research Chair Center for Studies in Behavioral Neurobiology Department of Psychology Concordia University, Montreal, Canada

"A Functional Circuit Underlying Male Sexual Behaviour Uncovered in

Lecture
Date:
Sunday, July 8, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Dr. Tali Kimchi
|
Dept of Molecular & Cellular Biology, Howard Hughes Medical Institute, Cambridge, MA

Integrate & Play Theory of Hippocampal Function:

Lecture
Date:
Monday, July 2, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Dr. Dori Derdikman
|
Centre for the Biology of Memory Norwegian University of Science & Technology (NTNU) Trondheim, Norway

An alternative model to the Declarative-Memory & Cognitive Map theories of the function of the hippocampus is suggested. the new model may explain the deficits described in the famous case of H.M., who displayed total anterograde amnesia following a surgery in which a bilateral dissection of the whole medial-temporal lobe (MTL) was perfromed (Scoville and Milner, 1957) . According to the model, the main functions of the MTL are: (1) to act as an integrator (2) to detect novelty. The integrator function is used, for example, for generation of the place-cell and grid-cell system. Normally, the MTL is integrating an episode until it detects a novel situation. Once the MTL detects such a novel situation, it sends the executive brain (perhaps the basal ganglia and/or prefrontal cortex) a message that it is time to play a novel behavioral game. In the case of H.M., where the MTL is missing, the executive brain never gets the message that an episode is novel, and thus continues to play "old games". In principle, at least, if this model is correct, H.M. could be cured from his memory problem, if the executive brain would have received the missing novelty signals artificially.

Itch more than scratching the surface

Lecture
Date:
Monday, June 25, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Gil Yosipovitch
|
Dept of Dermatology, Neurobiology & Anatomy, & Regenerative Medicine, Wake Forest University Health Sciences Winston-Salem, NC

Predicting odor pleasantness from odor structure:Pleasantness as a reflection of the physical world

Lecture
Date:
Monday, June 18, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Noam Sobel
|
Dept of Neurobiology, WIS

The cell biology of Alzheimer's disease: Intracellular pathways to pathogenesis

Lecture
Date:
Monday, June 11, 2007
Hour: 12:00 - 13:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Scott A. Small
|
Columbia University, School of Physicians and Surgeons, New York, NY

The Hippocampus and Memory: Consolidation or Transformation?

Lecture
Date:
Tuesday, May 29, 2007
Hour: 12:00 - 13:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Dr. Gordon Winocur
|
Rotman Research Institute, Toronto, Ontario, Canada

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