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Active Sensing by Bat Biosonar: Strategies of Information Flow Control

Lecture
Date:
Monday, August 17, 2009
Hour: 12:30
Location:
Nella and Leon Benoziyo Building for Brain Research
Dr. Marc Holderied
|
University of Bristol, UK

Abstract: Echolocation or biosonar is an alien sense to humans. For us as visually guided mammals it is hard to imagine what an echolocator's acoustic perception of its surroundings 'looks' like. Part of this difficulty arises because vision and biosonar differ fundamentally in a number of ways: a) Vision is based on two dimensional data, i.e. images focused on the retina in the eye, while bats evaluate a linear stream of echoes and have to reconstruct all directional/spatial information from the temporal and spectral properties of the echo stream; b) the number of sensory cells in hearing is much lower than in vision and c) biosonar is a case of active sensing, i.e. bats actively produce the signals with which they probe the environment, while vision (in the vast majority of cases) relies on external light sources. This combination of traits, i.e. limited bandwidth and active sensing has led to a number of behavioural adaptive strategies by which bats control what information about the environment becomes available to them. In a sense, external mechanisms to extract the relevant information from the plethora of available data are far more important in biosonar than in vision. Hence, biosonar offers unique opportunities to study behavioural strategies of information flow control by active sensing. We employed high resolution acoustic tracking techniques and 3D laser scanning of natural habitats to study free flying bats in forests. We investigated how they adapt flight patterns, calling behaviour and sonar signal design to optimize information flow.

Movement selectivity in the human mirror system

Lecture
Date:
Tuesday, July 28, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Ilan Dinstein New York University Visiting PhD Student – Malach Lab

Abstract: “Monkey mirror neurons are unique visuomotor neurons that respond when executing a particular movement (e.g. grasping, placing, or manipulating) and also when passively observing someone else performing that same movement. Importantly, subpopulations of mirror neurons respond in a selective manner to one preferred movement whether executed or observed. It has been proposed that the activity of mirror neurons underlies the monkey’s ability to perceive the goals and intentions of others. Human mirror neurons are thought to exist in two cortical areas, the anterior intraparietal sulcus (aIPS) and the ventral premotor (vPM), which have been called the human mirror system. A dysfunction in the responses of this system has been hypothesized to cause impairment in the ability to understand one another resulting in Autism. I will talk about three studies where we characterized the responses of the human mirror system using fMRI adaptation and classification techniques to assess their response selectivity for observed and executed hand movements. Two studies were performed with neurotypical individuals and the third with Autistic individuals.”

Role of Dopamine in Reward: Anatomical and Conceptual Issues

Lecture
Date:
Tuesday, July 14, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Satoshi Ikemoto NIDA (Nat. Inst. on Drug Abuse) Behavioral Neuroscience Research Branch NIH, USA

Abstract: The mesolimbic dopamine system from the ventral tegmental area (VTA) to the ventral striatum has been implicated in reward. Using intracranial self-administration procedures, we found that rats learn to self-administer cocaine or amphetamine into the medial portion of the ventral striatum more readily than the lateral ventral striatum. Rats learn to self-administer drugs such as opiates and cholinergic drugs into the posterior portion of the VTA more readily than the anterior VTA. Axonal tracer experiments revealed that the medial ventral striatum is preferentially innervated by dopamine neurons localized in the posterior VTA, while the lateral ventral striatum is preferentially innervated by dopamine neurons in the anterolateral VTA. Therefore, the mesolimbic dopamine system from the posterior VTA to the medial ventral striatum appears to be more responsive for rewarding effects of drugs. In addition, we have studied the nature of the rewarding effects of drugs. We found that noncontingent administration of cocaine or amphetamine into the medial ventral striatum increases leverpressing, when leverpressing contingently elicits visual signals. These results suggest that a function of dopamine in the ventral striatum is to facilitate actions in response to salient stimuli. Dopamine in the medial ventral striatum also appears to facilitate associative learning as shown by conditioned place preference of cocaine. We suggest that ventral striatal dopamine induces an arousing state that facilitates ongoing appetitive responding and reinforcement.

Collective Motion and Decision-Making in Animal Groups

Lecture
Date:
Thursday, July 9, 2009
Hour: 12:30
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Iain Couzin
|
Dept of Ecology and Evolutionary Biology and Program in Computational and Mathematical Biology Princeton University USA

Grouping organisms, such as schooling fish, often have to make rapid decisions in uncertain and dangerous environments. Decision-making by individuals within such aggregates is so seamlessly integrated that it has been associated with the concept of a “collective mind”. As each organism has relatively local sensing ability, coordinated animal groups have evolved collective strategies that allow individuals to access higher-order computational abilities at the collective level. Using a combined theoretical and experimental approach involving insect and vertebrate groups, I will address how, and why, individuals move in unison and investigate the principles of information transfer in these groups, particularly focusing on leadership and collective consensus decision-making. An integrated "hybrid swarm" technology is introduced in which multiple robot-controlled replica individuals interact within real groups allowing us new insights into group coordination. These results will be discussed in the context of the evolution of collective biological systems.

Neuronal Avalanches in the Cortex:A Case for Criticality

Lecture
Date:
Tuesday, July 7, 2009
Hour: 15:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Dietmar Plenz
|
Laboratory of Systems Neuroscience NIMH, USA

Complex systems, when poised near a critical point of a phase transition between order and disorder, exhibit scale-free, power law dynamics. Critical systems are highly adaptive and flexibly process and store information, which prompted the conjecture that the cortex might operate at criticality. This view is supported by the recent discovery of neuronal avalanches in superficial layers of cortex. The spatiotemporal, synchronized activity patterns of avalanches form a scale-free organization that spontaneously emerges in vitro as well as in vivo in the anesthetized rat and awake monkeys. Avalanches are established at the time of superficial layer differentiation, require balanced fast excitation and inhibition, and are regulated via an inverted-U profile of NMDA/dopamine-D1 interaction. Neuronal synchronization in the form of avalanches naturally incorporates nested theta/gamma-oscillations as well as sequential activations as proposed for synfire chains. Importantly, a singleavalanche is not an isolated network event, but rather its specific occurrence in time, its spatial spread, and overall size is part of an elementary organization of the dynamics that is described by three fundamental power laws. Overall, these results suggest that neuronal avalanches indicate a critical network dynamics at which the cortex gains universal properties found at criticality. These properties constitute a novel framework that allow for a precise quantification of cortex function such as the absolute discrimination of pathological from non-pathological synchronization, and the identification of maximal dynamic range for input-output processing.

Critical thoughts on critical periods: Are children better than adults at acquiring skills?

Lecture
Date:
Tuesday, July 7, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Prof. Avi Karni
|
Department of Human Biology University of Haifa

Physiological studies of the functional architecture of the basal ganglia neural networks

Lecture
Date:
Tuesday, June 30, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Prof. Hagai Bergman
|
Dept of Physiology and The Interdisciplinary Center for Neural Computation Hebrew University, Jerusalem

The basal ganglia (BG) are commonly viewed as two functionally related subsystems. These are the neuromodulators subsystem and the main-axis subsystem, in analogy with the critic-actor division of reinforcement learning agent. We propose that the BG main axis is performing dimensionality reduction of the cortical input leading to optimal trade-off between maximization of future cumulative reward and minimization of the cost (information bottleneck). In line with the information bottleneck dimensionality reduction model, BG main axis neurons maintain flat spike crosscorrelation functions, diverse responses to behavioral events, and broadly distributed values of signal and response correlations with zero population mean. On the other hand, the spontaneous and the evoked activity of BG dopaminergic and cholinergic modulators (critics) are significantly correlated. BG plasticity and learning are therefore controlled by homogenous modulators effects associated with local coincidences of cortico-striatal activity.

Brain and Reality: How Does the Brain Generate Perceptions and Actions

Lecture
Date:
Tuesday, June 23, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Prof. Eilon Vaadia
|
Dept of Medical Neurobiology Hadassah Medical School Hebrew University, Jerusalem

Evoked neural synchrony, visual attention and grouping

Lecture
Date:
Tuesday, June 16, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Prof. Marius Usher
|
Dept of Psychology, Tel Aviv University

Neural synchrony was proposed as a mechanism for visual attention, and more controversially, for grouping and figure-ground processing. In this talk I will first present evidence showing that evoked Gamma synchrony, via 50Hz subliminal flicker produces attentional orientation in the absence of awareness. Second, I will present data on the effects of evoked synchrony on grouping and figure-ground processing. The results indicate a fast temporal resolution for these processes (<20ms), which is mediated by lateral connections and which is sensitive to synchrony, but not to sustained oscillations of a specific frequency. Collaboration with: S Cheadle, F Bauer, H Mueller.

Large-scale brain dynamics: Functional MRI of spontaneous and optically-driven neural activity

Lecture
Date:
Monday, June 15, 2009
Hour: 12:45
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Dr. Itamar Kahn
|
Howard Hughes Medical Institute Harvard University

A fundamental problem in brain research is how distributed brain systems work together to give rise to behavior. I seek to advance our understanding of principles underlying the dynamic interaction between multiple neural systems, how the different systems co-operate and/or compete to give rise to goal-directed behavior, and the dynamics of the system when one or more of its components fail. Magnetic resonance imaging (MRI) methods allow us to simultaneously measure the function of multiple brain systems. In humans we can characterize the functional organization and specialization, and compare the system between health and disease. In animal models we can further dissect the circuits underlying these dynamics. In my work I aim to identify functional networks that span multiple cortical and subcortical regions, characterize their responses in the presence and absence of overt behavior, and modulate the observed dynamics. To advance these goals, I am developing new tools that will allow us to study large-scale neural systems across species. In this talk, I will review recent studies that use functional neuroimaging in humans and animal models. I will describe how spontaneous fluctuations of the blood oxygenation level-dependent (BOLD) signal measured with MRI in awake resting humans, reveal functional subdivisions in the medial temporal lobe memory system and parietal and prefrontal cortical components linked to it. I will describe results from non-human primates demonstrating that this functional organization persists across the species, highlighting cortical components that have undergone considerable areal expansion in humans relative to non-human primates, how this method can be used to identify homologue regions, and more generally, what can be learned from a comparative perspective. In the second part of my talk I will describe recent efforts to selectively modulate system dynamics. A lentivirus was used to target excitatory neurons in the rat cortex with light-activated cation channel channelrhodopsin-2. Using photostimulation to activate these neurons we were able to drive the BOLD response locally and in regions anatomically connected to the infected site in a variety of stimulation paradigms. I will discuss implications for understanding the BOLD signal and prospects for this approach in studying the microcircuit as well as large-scale brain dynamics. Finally, I will discuss the challenges and promises of whole-brain imaging in small animals, and how this work can provide avenues to bridge between a basic understanding of human behavior, large-scale neural dynamics, and psychiatric disorders where such dynamics are disrupted.

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Computing as modeling

Lecture
Date:
Tuesday, February 17, 2009
Hour: 12:30
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Oron Shagrir
|
Dept of Philosophy & Dept of Cognitive Science Hebrew University, Jerusalem

The view that the brain computes is a working hypothesis in cognitive and brain sciences. But what does it mean to say that a system computes? What distinguishes computing systems, such as brains, from non-computing systems, such as stomachs and tornadoes? I argue that a "structural" approach to computing cannot account for much of the computational work in cognitive neuroscience. Instead, I offer a modeling account, which is a variant of a "semantic" approach. On this modeling account, the key feature of computing is a similarity between the "inner" mathematical relations, defined over the representing states, and "outer" mathematical relations, defined over the represented states.

Changes in the brain during chronic nicotine: from thermodynamics to neuroadaptation

Lecture
Date:
Tuesday, February 17, 2009
Hour: 10:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Henry Lester
|
California Institute of Technology

The Development of Reading Pathways in School Age Children

Lecture
Date:
Thursday, February 12, 2009
Hour: 11:30
Location:
Nella and Leon Benoziyo Building for Brain Research
Dr. Michal Ben-Shachar
|
English Dept and the Gonda Brain Research Center Bar Ilan University

Learning to read involves exposure to large amounts of print in a focused period of time during childhood. How does this environmental transition affect cortical circuits for visual perception and shape recognition? I will present data from a developmental study of reading examining the relation between reading skill, cortical function and white matter properties in school age children. Functional properties in area MT+, and white matter properties in temporal callosal fibers, are both correlated with reading skill. I will discuss possible interpretations of these findings within a general model of the reading pathways.

Plasticity in the Human Ventral Stream:: Regional Differences Across Time Scales

Lecture
Date:
Monday, February 9, 2009
Hour: 12:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Kalanit Grill-Spector
|
Dept of Psychology & Neurosciences Institute Stanford University, CA

The human ventral stream consists of regions in the lateral and ventral aspects of the occipital and temporal lobes and is involved in visual recognition. One robust characteristic of selectivity in the adult human ventral stream is category selectivity. Category selectivity is manifested by both a regional preference to particular object categories, such as faces, places and bodyparts, as well as in specific (and reproducible) distributed response patterns across the ventral stream for different object categories. However, it is not well understood how experience modifies these representations and how do these representations come about throughout development. Here, I will describe two sets of experiments in which we addressed these important questions. First, I will describe experiments in adults in which we examined the effect of repetition on categorical responses in the ventral stream. Repeating objects decreases responses in the human ventral stream. However, repetition largely does not change the profile of category selectivity in the ventral stream, except for a place-selective region in the collateral sulcus in which long-lagged repetitions sharpened its responses. Second, I will describe experiments in which we examined changes in category selectivity throughout development from middle childhood (7-11 years), through adolescence (12-16) into adulthood. Surprisingly, we find that it takes more than a decade for the development of adult-like face and place-selective regions. In contrast, the lateral occipital object-selective region showed an adult-like profile by age 7. Finally, I will discuss the implications of these results on plasticity in the ventral stream and our theoretical models linking between fMRI measurements and the underlying neural mechanisms.

Neuronal Circuitry of Conditioned Fear

Lecture
Date:
Monday, February 2, 2009
Hour: 12:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Andreas L&uuml;thi
|
Friedrich Miescher Institute, Switzerland

Fearful Brains in an Anxious World

Lecture
Date:
Sunday, February 1, 2009
Hour: 15:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Joseph E. Ledoux
|
Center for Neural Science, New York University

Generation of temporal patterns in the olivo-cerebellar system

Lecture
Date:
Thursday, January 22, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Gilad Jacobson
|
Dept of Neurobiology Hebrew University, Jerusalem

The olivo-cerebellar system plays a crucial role in timing of both motor and non-motor tasks. The mechanisms underlying this timing capability are still unclear. Here I propose a plausible mechanism in which a temporal pattern reflects accurate phase relationships between the oscillatory activity of olivary neurons. I provide evidence from chronic multi-electrode recordings in awake rats that inferior olive oscillations possess hitherto unknown properties that: (1) Oscillations in different parts of the inferior olive can maintain constant, non-zero phase differences; (2) The oscillation frequency of olivary neurons is co-modulated; and (3) Phase differences are well maintained despite frequency changes. Thus, the inferior olive can generate not only &#8220;clock ticks&#8221; at the oscillation cycle duration, but more importantly shorter intervals that emerge by combining different parts of the olivary circuitry. This enables the olivo-cerebellar circuit to support timing in the range implicated by behavioural studies.

Personal theories and self-images: Critical tools in the rehabilitation from a severe brain injury

Lecture
Date:
Sunday, January 18, 2009
Hour: 14:45
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Yoram Eshet
|
Dept of Psychology & Education The Open University of Israel

The lecture is given by a person who suffers from a severe (right-parietal) brain injury from the Yom Kippur War (1973). It discusses the injury as it is perceived by the injured person. The lecture focuses on self-images of the injury and emphasizes the pivotal role of higher cognitive processes, such as personal theories and narratives, as critical tools for a successful; rehabilitation.

Learning to smell: Cortical plasticity and odor perception

Lecture
Date:
Wednesday, January 14, 2009
Hour: 10:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Donald Wilson
|
New York University School of Medicine & Emotional Brain Institute Nathan Kline Institute for Psychiatric Research

Odor perception - discrimination and recognition of volatile chemicals in the environment &#8211; is critical for wide ranging behaviors including kin recognition, mate selection, predator avoidance, homing, and feeding. Most naturally occurring odors are complex mixtures, often containing hundreds of different components. Furthermore, natural odors invariably occur against odorous backgrounds. Thus, olfaction and odor perception involves far more than simple odor ligands binding to receptors in the nose. I will describe recent work

The tempotron: applications to visual and time-warp invariant auditory processing

Lecture
Date:
Tuesday, January 13, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Robert Guetig
|
Racah Institute of Physics & Interdisciplinary Center for Neural Computation Hebrew University, Jerusalem

The timing of action potentials of sensory neurons contains substantial information about the eliciting stimuli. Although computational advantages of spike-timing-based neuronal codes have long been recognized, it is unclear whether and how neurons can learn to read out such representations. We propose a novel biologically plausible supervised synaptic learning rule, the tempotron, enabling neurons to efficiently learn a broad range of decision rules, even when information is embedded in the spatio-temporal structure of spike patterns and not in mean firing rates. We demonstrate the enhanced performance of the tempotron over the rate-based perceptron in reading out spike patterns from retinal ganglion cell populations. Extending the tempotron to conductance-based voltage kinetics, we show that this model can subserve time-warp invariant processing of afferent spike patterns. Furthermore, we show that the conductance-based tempotron can learn to balance excitation and inhibition to match its integration time constant to the temporal scale of a given processing task. We show that already a small population of neurons can solve the TI46 isolated digit speech recognition task with near perfect performance

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