All events, 2011

Predictive Sparse Coding:A Dynamical Circuit Model of Early Sensory Processing

Lecture
Date:
Wednesday, May 4, 2011
Hour: 12:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Prof. Dmitri Chklovskii
|
Janelia Farm, HHMI, USA

In early sensory systems, such as retina and olfactory bulb in vertebrates or optic and antennal lobes in invertebrates, information about the world converges from a large number of receptors onto a much smaller number of projection neurons. Such bottleneck in the communication channel to the higher brain areas (Attneave, 1954, Barlow & Levick, 1976) can be overcome for sensory stimuli containing correlations by the predictive coding strategy (Srinivasan et al, 1982). In case of the retina, instantaneous subtraction of the least squares prediction compresses information and results in center-surround biphasic receptive fields. However, explaining variation of receptive fields with SNR (Srinivasan et al, 1982, Van Hateren, 1992, Atick & Redlich, 1990) would require circuit re-wiring which is unlikely on short time scales. Here we develop the predictive coding idea by proposing that a non-linear recurrent neuronal circuit can implement predictive coding adaptively: stimuli of different SNR result in different inhibitory surrounds. We solve the transient dynamics of this circuit in response to a step-like stimulus and demonstrate that it communicates a residual of the regularization path to higher brain areas. Thus, we are able to map a non-trivial computation on a concrete neuronal circuit and provide a theoretical framework to understand neural coding for many physiological experiments.

Flip sides of the same brain: Words and faces are both mediated by universal computational principles

Lecture
Date:
Wednesday, April 27, 2011
Hour: 12:30
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Marlene Behrmann
|
Carnegie Mellon University, Pittsburgh Psychology/Center for the Neural Basis of Cognition

A key issue that continues to generate controversy concerns the nature of the psychological, computational and neural mechanisms that support the visual recognition of objects such as faces and words. While some researchers claim that visual recognition is accomplished by category-specific modules dedicated to processing distinct object classes, other researchers have argued for a more distributed system with only partially specialized cortical regions. Considerable evidence from both functional neuroimaging and neuropsychology would seem to favor the modular view, and yet close examination of those data reveal rather graded patterns of specialization that support a more distributed account. This talk presents theoretical and empirical data that explore a theoretical middle ground in which the functional specialization of brain regions arises from general principles and constraints on neural representation and learning that operate throughout cortex but that nonetheless have distinct implications for different classes of stimuli such as faces and words.

Microcircuit Dynamics in the Striatum

Lecture
Date:
Thursday, April 14, 2011
Hour: 12:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Gilad Silberberg
|
Assistant Professor, Dept of Neuroscience Karolinska Institute, Stockholm

Motor behaviour requires the meaningful integration of a multitude of sensory information. The basal ganglia are essential for such sensory-motor processing and underlie motor planning, performance, and learning. The striatum is the input layer of the basal ganglia, acting as a “hub” that receives glutamatergic and dopaminergic inputs from different brain regions. The intrastriatal microcircuit is a predominantly inhibitory GABAergic network comprised of a majority of projection neurons (medium spiny neurons, MSNs) and a minority of interneurons. In order to understand the operation of striatum it is essential to have a good description of the dynamic properties of the striatal microcicuitry and how it affects the activity striatal projection neurons. We use patch-clamp recordings in slice and in vivo combined with fluorescent microscopy and optogenetics to reveal the striatal microcircuit properties underlying sensorimotor processing

Mechanisms of axonal degeneration in health and disease

Lecture
Date:
Tuesday, April 12, 2011
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Avraham Yaron
|
Dept of Biological Chemistry, WIS

In the developing peripheral nervous system, many neurons die shortly after their axons have reached their target fields. This neuronal elimination serves as a mean to achieve a precise match between the number of neurons and the target innervation requirements. In addition, this process ensures that misguided axons, which do not reach their appropriate targets, will be eliminated. The regulation of this process is based on the limited production of various neurotrophic factors, insufficient to sustain the entire neuronal population. Since this loss usually occurs after the axons have already fully extended, some kind of axonal disintegration must escort the death of the cell body. The talk will describe our efforts to uncover the mechanisms of axonal elimination during this process, and their relevance to axonal degeneration in pathological condition

Brain Sciences Open Day

Lecture
Date:
Monday, April 11, 2011
Hour: 09:30 - 14:00
Location:
Gerhard M.J. Schmidt Lecture Hall

Conscious Perception in USN

Lecture
Date:
Tuesday, April 5, 2011
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Nachum Soroker
|
Dept of Neurological Rehabilitation, Loewenstein Hospital, Raanana, and Sackler Faculty of Medicine Tel Aviv University

Patients with right hemisphere damage often exhibit a symptom complex where contra-lesional objects and events fail to induce an appropriate behavioral reaction. The most puzzling aspect of this syndrome - termed unilateral spatial neglect (USN) - is the failure of salient left-sided stimuli to attract attention and generate conscious perception. This phenomenon, which is often multi-modal, may happen in cases where the sensory pathways and the primary cortical areas are completely intact. Following a short description of the clinical manifestations, underlying anatomy and recovery patterns of USN, I will present data gathered in a series of studies done in our hospital, which aimed to clarify the nature of processing received by stimuli on the neglected side, and the effect of some theory-motivated manipulations aimed to ameliorate the impaired processing.

Dynamics of cortical activity

Lecture
Date:
Wednesday, March 30, 2011
Hour: 14:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Prof. David A. McCormick
|
Yale University School of Medicine, New Haven, CT

Do all Japanese paintings look the same? Styles and Schools in Japanese Art

Lecture
Date:
Tuesday, March 29, 2011
Hour: 14:00 - 18:00
Location:
Dolfi and Lola Ebner Auditorium
Prof. Itamar Procaccia
|
Department of Chemical Physics, WIS

Engineered neuronal networks

Lecture
Date:
Tuesday, March 29, 2011
Hour: 12:30
Location:
Jacob Ziskind Building
Prof. Elisha Moses
|
Department of Physics of Complex Systems, WIS

Neuronal cultures grown from hippocampal neurons exhibit a distinct all-or-none burst firing pattern. We introduce quantitative tools to investigate the properties of the network which lead to this kind of behavior, and identify the distribution of input connections as the dominant factor governing the behavior of the network. We show that one-dimensional networks display a significantly simpler behavior, and use this observation to design some computational neuronal circuits.

Mechanisms of Associative Learning in Young and Aging Brain

Lecture
Date:
Tuesday, March 22, 2011
Hour: 15:00
Location:
Gerhard M.J. Schmidt Lecture Hall
Prof. John Disterhoft
|
Dept of Physiology Northwestern University Chicago, IL

The neuronal alterations which occur in important neuron populations in young adult animals and changes in those processes which occur during aging and cause age-related learning deficits are beginning to be understood with cellular to systems level analyses. We have studied these processes with hippocampus-dependent trace eyeblink conditioning tasks. Calcium and calcium-activated potassium currents, that help control intrinsic neuronal excitability and are altered during learning and in aging, have been extensively studied. In vivo recording studies of CA1 hippocampal pyramidal neurons during and after associative eyeblink conditioning demonstrate functional alterations during learning and aging. We have examined mechanisms underlying these alterations in firing rate by examining CA1 neurons in brain slices. These current and voltage clamp studies of alterations in the calcium-activated potassium currents that increase neuronal excitability during associative learning in young animals and age-associated changes in these currents that occur in learning-impaired aging animals will be described. Behavioral pharmacological studies have demonstrated that age-associated behavioral changes can be reversed by compounds targeting neuronal excitability. Intracellular signaling pathways and alterations in calcium currents that may lead to these changes in intrinsic excitability during learning are being explored.

Pages

All events, 2011

Microcircuit Dynamics in the Striatum

Lecture
Date:
Thursday, April 14, 2011
Hour: 12:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Gilad Silberberg
|
Assistant Professor, Dept of Neuroscience Karolinska Institute, Stockholm

Motor behaviour requires the meaningful integration of a multitude of sensory information. The basal ganglia are essential for such sensory-motor processing and underlie motor planning, performance, and learning. The striatum is the input layer of the basal ganglia, acting as a “hub” that receives glutamatergic and dopaminergic inputs from different brain regions. The intrastriatal microcircuit is a predominantly inhibitory GABAergic network comprised of a majority of projection neurons (medium spiny neurons, MSNs) and a minority of interneurons. In order to understand the operation of striatum it is essential to have a good description of the dynamic properties of the striatal microcicuitry and how it affects the activity striatal projection neurons. We use patch-clamp recordings in slice and in vivo combined with fluorescent microscopy and optogenetics to reveal the striatal microcircuit properties underlying sensorimotor processing

Mechanisms of axonal degeneration in health and disease

Lecture
Date:
Tuesday, April 12, 2011
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Avraham Yaron
|
Dept of Biological Chemistry, WIS

In the developing peripheral nervous system, many neurons die shortly after their axons have reached their target fields. This neuronal elimination serves as a mean to achieve a precise match between the number of neurons and the target innervation requirements. In addition, this process ensures that misguided axons, which do not reach their appropriate targets, will be eliminated. The regulation of this process is based on the limited production of various neurotrophic factors, insufficient to sustain the entire neuronal population. Since this loss usually occurs after the axons have already fully extended, some kind of axonal disintegration must escort the death of the cell body. The talk will describe our efforts to uncover the mechanisms of axonal elimination during this process, and their relevance to axonal degeneration in pathological condition

Brain Sciences Open Day

Lecture
Date:
Monday, April 11, 2011
Hour: 09:30 - 14:00
Location:
Gerhard M.J. Schmidt Lecture Hall

Conscious Perception in USN

Lecture
Date:
Tuesday, April 5, 2011
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Nachum Soroker
|
Dept of Neurological Rehabilitation, Loewenstein Hospital, Raanana, and Sackler Faculty of Medicine Tel Aviv University

Patients with right hemisphere damage often exhibit a symptom complex where contra-lesional objects and events fail to induce an appropriate behavioral reaction. The most puzzling aspect of this syndrome - termed unilateral spatial neglect (USN) - is the failure of salient left-sided stimuli to attract attention and generate conscious perception. This phenomenon, which is often multi-modal, may happen in cases where the sensory pathways and the primary cortical areas are completely intact. Following a short description of the clinical manifestations, underlying anatomy and recovery patterns of USN, I will present data gathered in a series of studies done in our hospital, which aimed to clarify the nature of processing received by stimuli on the neglected side, and the effect of some theory-motivated manipulations aimed to ameliorate the impaired processing.

Dynamics of cortical activity

Lecture
Date:
Wednesday, March 30, 2011
Hour: 14:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Prof. David A. McCormick
|
Yale University School of Medicine, New Haven, CT

Do all Japanese paintings look the same? Styles and Schools in Japanese Art

Lecture
Date:
Tuesday, March 29, 2011
Hour: 14:00 - 18:00
Location:
Dolfi and Lola Ebner Auditorium
Prof. Itamar Procaccia
|
Department of Chemical Physics, WIS

Engineered neuronal networks

Lecture
Date:
Tuesday, March 29, 2011
Hour: 12:30
Location:
Jacob Ziskind Building
Prof. Elisha Moses
|
Department of Physics of Complex Systems, WIS

Neuronal cultures grown from hippocampal neurons exhibit a distinct all-or-none burst firing pattern. We introduce quantitative tools to investigate the properties of the network which lead to this kind of behavior, and identify the distribution of input connections as the dominant factor governing the behavior of the network. We show that one-dimensional networks display a significantly simpler behavior, and use this observation to design some computational neuronal circuits.

Mechanisms of Associative Learning in Young and Aging Brain

Lecture
Date:
Tuesday, March 22, 2011
Hour: 15:00
Location:
Gerhard M.J. Schmidt Lecture Hall
Prof. John Disterhoft
|
Dept of Physiology Northwestern University Chicago, IL

The neuronal alterations which occur in important neuron populations in young adult animals and changes in those processes which occur during aging and cause age-related learning deficits are beginning to be understood with cellular to systems level analyses. We have studied these processes with hippocampus-dependent trace eyeblink conditioning tasks. Calcium and calcium-activated potassium currents, that help control intrinsic neuronal excitability and are altered during learning and in aging, have been extensively studied. In vivo recording studies of CA1 hippocampal pyramidal neurons during and after associative eyeblink conditioning demonstrate functional alterations during learning and aging. We have examined mechanisms underlying these alterations in firing rate by examining CA1 neurons in brain slices. These current and voltage clamp studies of alterations in the calcium-activated potassium currents that increase neuronal excitability during associative learning in young animals and age-associated changes in these currents that occur in learning-impaired aging animals will be described. Behavioral pharmacological studies have demonstrated that age-associated behavioral changes can be reversed by compounds targeting neuronal excitability. Intracellular signaling pathways and alterations in calcium currents that may lead to these changes in intrinsic excitability during learning are being explored.

Lazy Neurons for Good Shape or Filling in the Gaps...The Mind's Way

Lecture
Date:
Tuesday, March 15, 2011
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Ohad Ben-Shahar
|
Dept of Computer Science Ben Gurion University

The phenomenon of visual curve completion, where the visual system completes the missing part (e.g., due to occlusion) between two contour fragments, is a major problem in perceptual organization research, both behaviorally and computationally. Previous computational approaches for the shape of percetually completed curves typically follow an axiomatic approach via formal descriptions of desired, image-based perceptual properties (e.g, minimum total curvature, roundedness, etc...). Unfortunately, however, it is difficult to determine such desired properties psychophysically and indeed there is no consensus in the literature for what they should be. Instead, in this paper we suggest to exploit the fact that curve completion occurs in early vision in order to formalize the problem in a space that abstracts the primary visual cortex (For the technically inclined, this space is called the unit tangent bundle associated with R2). We show that a single basic principle of “minimum energy consumption” in this space not only results in a rigorous, non axiomatic, computational theory, but also makes excellent predictions and explanations for recent perceptual findings in the literature

Distinct layers or a continuum? A morphological and functional analysis of pyramidal cells in the supragranular layers of rat barrel cortex

Lecture
Date:
Thursday, March 10, 2011
Hour: 14:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Jochen Staiger
|
Dept of Neuroanatomy University of Göttingen

Pyramidal neurons in supragranular layers II and III of rodent sensory cortices are a main target of ascending sensory information conveyed by columnar projections of layer IV as well as contextual information from neighboring columns or higher cortical areas. However, layer II is not separable from layer III on cytoarchitectonic grounds. We therefore investigated to which extent pyramidal neurons in the supragranular layers differ in their input-output connectivity. We obtained detailed spatial maps of layer-specific intracortical functional input connectivity for electrophysiologically and morphologically identified supragranular pyramidal neurons by combining local photolysis of caged glutamate with whole-cell patch-clamp recordings using biocytin-containing pipettes in rat barrel cortex in vitro. The main source of excitatory inputs onto all supragranular pyramidal cells was layer IV of the same column. This translaminar excitatory source was even more prominent than local and transcolumnar excitatory inputs from within the supragranular layers, both in density and strength. Additionally, many pyramidal neurons received a prominent excitatory layer Va input, often originating from beyond the “home” column. Among those pyramidal neurons we detected a significantly higher fraction of cells located in a putative layer II than in TZ or putative layer III. Our results indicate a strong but differential information transmission from layer IV as well as layer Va, both important cortical entry points for parallel streams of sensory information, toward the supragranular layers. Within supragranular layers, information processing in pyramidal neurons can be "fine tuned" through local and transcolumnar excitatory networks. Finally this integrated information is forwarded with a prominent transcolumnar component by putative layer II pyramidal cells but with an intracolumnar preponderance, including significant layer IV-backprojections, by putative layer III pyramidal neurons

Pages

All events, 2011

There are no events to display

All events, 2011

There are no events to display