All events, All years

An integrative approach towards understanding the neural basis of congenital prosopagnosia

Lecture
Date:
Tuesday, May 19, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Galia Avidan
|
Dept of Psychology and Zlotowski Center for Neuroscience Ben Gurion University of the Negev

Congenital prosopagnosia (CP) refers to the deficit in face processing that is apparently life-long in duration, arises in the absence of brain damage of any form and occurs in individuals with intact sensory and intellectual function. As such, CP provides a unique model in which to explore the psychological and neural bases of normal face processing. Despite the growing interest in CP, the neural mechanism giving rise to this disorder is still unclear. We addressed this issue by adopting an integrative approach in which both functional and structural imaging techniques were combined. Specifically, using fMRI, we have documented normal face selective activation in face -related regions in occipito-temporal cortex but in contrast, revealed abnormal activation in these individuals in frontal regions, suggesting that information propagation between frontal and occipito-temporal regions is disrupted in this disorder. Consistently with this account, diffusion tensor imaging (DTI) measures revealed that the two major posterior-anterior tracts (inferior longitudinal fasciculus, inferior fronto-occipital fasciculus) through the fusiform face area (FFA) had significantly fewer fibers and lower fractional anisotropy (FA) values in CP. Finally, along the same line, structural imaging data revealed a significant reduction in volume of the anterior fusiform gyrus in the CP group, but normal volume at the location of the functionally defined FFA. Thus, taken together, these findings provide, for the first time, a comprehensive account for the neural deficits underlying congenital prosopagnosia and shed light on the underlying distributed circuit mediating normal face processing.

Behavioral and neurophysiological correlates of GABA modulation in the basal ganglia

Lecture
Date:
Tuesday, May 5, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Izhar Bar-Gad
|
Gonda Brain Research Center Bar Ilan University

The cortico-basal ganglia pathway is involved in normal motor control and implicated in multiple movement disorders. We used focal microinjections of the GABA-A antagonist bicuculline to the sensorimotor putamen of behaving primates to induce stereotyped tics similar to those observed in human Tourette syndrome. The tics were accompanied by synchronized phasic changes in the local field potential and single cell activity of neurons throughout the cortico-basal ganglia loop. We also used focal injection of bicuculline to different functional domains of the globus pallidus external segment (GPe) to induce a variety of hyper-behavioral symptoms. These, symptoms varied between dyskinesia, stereotypy and attention deficit depending on injection site within the motor, limbic and associative domains respectively. The injections led to distributed uncorrelated changes in firing pattern throughout the cortico-basal ganglia loop. The neurophysiological findings and their implication on models of information processing in the basal ganglia will be discussed in the lecture.

Odotopic maps, odor coding, rats, mice, and behavior

Lecture
Date:
Monday, May 4, 2009
Hour: 12:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Burton Slotnick
|
Dept of Psychology American University

What is the neural code for odor quality perception? Perhaps the most widely accepted view is spatial: that different odors are represented at the level of the olfactory bulb by bulbar patterns of activation, a so-called odotopic combinatorial coding for the receptive fields of olfactory sensory neurons. The primary evidence for this view comes from variety of imaging studies demonstrating orderly relationships between chemical structure of odorants and sites of activation across the olfactory bulb. However, behavioral studies with rodents fail to support predictions based on anatomy but open new avenues for research on this still elusive sensory modality.

Interactions between environmental changes and brain plasticity in birds

Lecture
Date:
Monday, April 27, 2009
Hour: 12:30
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Anat Barnea
|
Dept of Natural and Life Sciences The Open University of Israel

Neurogenesis (birth of new neurons) occurs in many vertebrates, including humans. Most of the new neurons die before reaching destination. Those which survive migrate to various brain regions, replace older ones and connect to existing circuits. Evidence suggests that this replacement is related to acquisition of new information. Therefore, neuronal replacement is seen as a form of brain plasticity that enables organisms to adjust to environmental changes. However, direct evidence of a causal link between replacement and learning remains elusive. I will review a few of our studies which tried to uncover conditions that influence new neuronal recruitment and survival, and how these phenomena relate to the life of birds. We hypothesize that an increase in new neuron recruitment is associated with expected or actual increase in memory load, particularly in brain regions that process and perhaps store this new information. Moreover, since new neuronal recruitment is part of a turnover process, we assume that the same conditions that favor the survival of some neurons induce the death of others. I will offer a frame and rational for comparing neuronal replacement in the adult avian brain, and try to uncover the pressures, rules, and mechanisms that govern its constant rejuvenation. I will discuss a variety of behaviors and environmental conditions (food-hoarding, social change, parent-offspring recognition, migration) and their effect on new neuronal recruitment in relevant brain regions. I will describe various approaches and techniques which we used in those studies (behavioral, anatomical, cellular and hormonal), and will emphasize the significance of studying behavior and brain function under natural or naturalistic conditions.

Neural decoding and optimal filtering: on a reverse engineering view of neural information processing

Lecture
Date:
Monday, April 20, 2009
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Ron Meir
|
Faculty of Electrical Engineering Technion, Haifa

The representation of value in the human brain

Lecture
Date:
Tuesday, April 7, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Prof. Ifat Levy
|
Yale University

The neural representation of value is a matter of great debate. In particular, it is not clear whether multiple valuation systems exist, each representing value under different conditions, or whether a single system that uses a “common currency” for the representation of value under many different conditions can be identified. I will present two studies in which we combined experimental methods from behavioral economics with functional MRI to study the representation of value in the human brain. The first study compared choices under two terms of uncertainty: risk, when probabilities of different outcomes are known, and ambiguity, when such probabilities are not known. Our results show that although subjects exhibit markedly different choice behaviors under these two conditions, a single system, consisting of the striatum and the medial prefrontal cortex (MPFC) encodes choice values in both cases. In the second study we used MPFC activation elicited by passive viewing of goods in the scanner to predict subsequent choices between these goods made outside of the scanner. Our predictions were significantly above chance, suggesting that the same valuation system is engaged whether or not choice is required. Based on these results together with previous studies we suggest that the striatum and the MPFC are the final common pathway for valuation – other areas may be differentially involved in encoding value under different conditions, but all of these areas should transfer their output to the final system to guide choice behavior.

“LIS1, More or Less? Implications for Brain Development and Human Disease”

Lecture
Date:
Tuesday, March 31, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Prof. Orly Reiner
|
Dept of Molecular Genetics, WIS

Perception and Action Interactions:Evidence from Neuropsychology, Neuroimaging, and Transcranial Magnetic Stimulation

Lecture
Date:
Thursday, March 26, 2009
Hour: 11:30
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Jody Culham
|
Dept of Psychology, University of Western Ontario, Canada Visiting Senior Fellow, Institute of Advanced Studies University of Bologna, Italy

Although prominent theories of vision have emphasized dissociations between two visual streams specialized for perception and action, in some situations, the two streams must interact. One such situation is the performance of actions upon remembered objects. Neuropsychological evidence from two patients with occipitotemporal lesions suggests that while immediate actions can be performed using only the dorsal vision-for-action stream, delayed actions require integrity of the ventral vision-for-perception stream. My lab has investigated the interactions between the two streams during delayed grasping using functional magnetic resonance imaging and transcranial magnetic stimulation. Our results suggest that delayed actions re-recruit information about object properties such as shape, size and orientation from the ventral stream and early visual areas at the time the delayed action is performed

Synergistic Interactions Between Molecular Risk Factors of Alzheimer’s Disease

Lecture
Date:
Tuesday, March 24, 2009
Hour: 12:30
Location:
Jacob Ziskind Building
Prof. Daniel Michaelson
|
Dept of Neurobiology, Tel Aviv University

The allele E4 of apolipoprotein E (apoE4), the most prevalent genetic risk factor for Alzheimer’s disease, is associated with elevated levels of brain amyloid. This led to the suggestion that the pathological effects of apoE4 are mediated via synergistic pathological interactions with amyloid β (Aβ). We have recently shown that activation of the amyloid cascade by inhibition of the Aβ-degrading enzyme neprilysin in brains of apoE3 and apoE4 mice results in the isoform specific degeneration in apoE4 mice, of hippocampal CA1 neurons and of entorhinal and septal neurons. This is accompanied by the accumulation of intracellular Aβ and apoE and by pronounced cognitive deficits in the ApoE4 mice. We presently investigated the cellular mechanisms underlying the apoE4 dependent Aβ mediated neurodegeneration of CA1 and septal neurons and their neuronal specificity. Confocal microscopy kinetic studies revealed that the accumulated Aβ in CA1 neurons of apoE4 mice co-localizes with lysosomes and is associated with lysosomal activation and subsequent apoptotic neuronal cell death. Furthermore the accumulated Aβ is oligomerized. In contrast the degeneration of septal neurons is not associated with oligomerization of the accumulated Aβ. Instead intracellular Aβ in septal neurons co-localizes with the apoE receptor LRP whose levels are specifically elevated in these cells. These findings suggest that the apoE4 dependent Aβ mediated neurodegeneration is related, in CA1 but not in septal neurons, to oligomerization of the accumulated Aβ. In addition, neurodegeneration of CA1 but not of septal neurons is associated with inflammatory activation suggesting that the brain area specificity of the effects of apoE4 and Aβ are also related to brain area specific non neuronal mechanisms such as inflammation. Neuronal plasticity experiments revealed that apoE4 inhibits synaptogenesis and neurogenesis and stimulates apoptosis in hippocampal neurons of apoE4 mice that have been exposed to an enriched environment. These effects are also associated with the specific accumulation of apoE4 and oligomerized Aβ in the affected neurons. Additional experiments revealed that apoE4 up-regulates the expression of inflammation-related genes following i.c.v injection of LPS and that this effect is also associated with the accumulation of intra neuronal Aβ in hippocampal neurons. These findings suggest that the impaired neuronal plasticity and hyper inflammatory effects of apoE4 may also be mediated via cross talk interactions of apoE4 with the amyloid cascade.

Now I See It, Now I Don’t: Neural Basis of Simple Perceptual Decisions in the Human Brain

Lecture
Date:
Wednesday, March 18, 2009
Hour: 12:30
Location:
Nella and Leon Benoziyo Building for Brain Research
Dr. Tobias H. Donner
|
Center for Neural Science & Dept of Psychology New York University

It is frequently proposed that conscious perceptual decisions are produced by recurrent interactions among multiple brain areas. Sensory stimuli, which are close to psychophysical threshold or perceptually bistable, induce fluctuating percepts in the face of constant sensory input. Thus, these stimuli provide ideal tools for probing the intrinsic neural mechanisms underlying perceptual decisions, in the absence of extrinsic stimulus changes. I will present human neuroimaging (MEG and fMRI) studies, in which we used this approach for probing the large-scale neural mechanisms underlying decisions about the presence or absence of simple visual features. Our results suggest that neural population activity in parietal, prefrontal, and premotor areas reflects the decision process, and that population activity in extrastriate ventral visual cortex reflects perception. Further, cooperative and competitive long- range interactions, across multiple levels of the cortical processing hierarchy, both seem to underlie simple perceptual decisions.

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Representation of the visual field in object-selective cortex

Lecture
Date:
Wednesday, December 17, 2008
Hour: 15:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Dr. Rory Sayres
|
Dept of Psychology, Stanford University

Functional MRI (fMRI) studies have defined a series of visual processing regions in the human cortex, which are believed to enable visual recognition behaviors through a hierarchy of processing stages. At the higher stages in this hierarchy lie regions which preferentially respond to images of intact objects compared to other visual stimuli, a set of regions collectively termed object-selective cortex. Within object-selective cortex exist category-selective regions, which prefer particular categories of images over others (e.g., faces, body parts, houses or scenes). Initially these regions were considered non-retinotopic, but increasing evidence indicates substantial retinal position selectivity, and in some cases retinotopy, in these regions. What is the representation of the visual field in object-selective regions? Are separate object- and category-selective regions part of a single map or embedded within a set of distinct visual field maps? We scanned seven subjects on separate experiments to localize object/category-selective regions, and measure visual field maps (GE 3T scanner). For retinotopic experiments, subjects viewed moving bar stimuli containing different stimuli, including slowly drifting checkerboards and frontal face images. The bars extended out to around 14° eccentricity from the fovea, and had a width of ~2.6°. We employed a recently-developed method for estimating population receptive fields (pRFs) using fMRI (Dumoulin and Wandell, Neuroimage, 2008), which estimates pRF center and size for each cortical location. Face-containing bars produced substantially larger responses than checkerboards along the fusiform gyrus, improving our ability to measure visual field maps in these regions. Eccentricity maps revealed two foveal representations, which may correspond to visual field map clusters previously identified as VO and VT (Wandell et al., Neuro-opth. Jpn., 2006). These foveas are within or adjacent to fusiform face-selective regions, and separated by smoothly-varying extra-foveal maps which are less face-selective. For several subjects, pRF sizes systematically increased with eccentricity in face-selective regions. The distribution of pRF sizes were substantially larger than in earlier visual cortex, but comparable to recent measurements made in lateral occipital cortex. We find two spatially separate face-selective regions along the fusiform gyrus, with comparable visual field coverage, separated by a representation of intermediate eccentricities. This indicates these two regions are likely to fall within different visual field maps. Current work addresses possible effects of low-level visual features (e.g. spatial frequency) and stimulus visibility in driving the observed face-selective retinotopic responses. I will also present some preliminary data from retinotopic mapping with house-containing bars, and an examination of retinotopic organization in house- or scene-selective cortical regions.

Active sensing: from natural stimulus statistics to auditory object classification in echolocating bats

Lecture
Date:
Tuesday, December 16, 2008
Hour: 12:30
Location:
Jacob Ziskind Building
Yossi Yovel
|
(Post-doc Ulanovsky Group) Department of Neurobiology, WIS

Echolocating bats perceive their surroundings acoustically. They continuously emit sonar signals and analyze the returning echoes, which enables them to orient in space and acquire food in complete darkness. Natural echoes along with other natural sounds compose a major part of the bat's sensory world, and have likely played a key evolutionary role in shaping the design of the bat's echolocation system and the auditory computations in the bat brain. However, the statistics of natural complex echoes, as well as how bats utilize them, are poorly understood – especially in the context of sonar-based object classification. The goal of this work was to elucidate the natural acoustical stimuli in the bat's world. I will present data on the statistical properties of complex echoes from various classes of plants and will compare them to what is known about natural images. In addition I will use a machine learning approach to discuss ways that bats may use to classify these stimuli. Finally, I will also describe behavioral experiments that aimed to understand the strategy used by bats to classify natural stimuli.

Optogenetics: Application to Neuroscience and Neuropsychiatry

Lecture
Date:
Monday, December 15, 2008
Hour: 11:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Karl Deisseroth
|
Depts of Bioengineering & Psychiatry, Stanford University

Optogenetics, synthesizing microbial opsins and solid-state optics, has achieved the goal of millisecond-precision bidirectional control of defined cell types in freely behaving mammals, but has not yet been widely applied to neuroscience and neuropsychiatry experimental challenges. First, relevant to important basic science questions, we have now successfully developed methods to target and control several classes of modulatory neurons in behaving mammals and intact neural tissue, and we are probing and quantifying measures of altered circuit performance under optogenetic control of defined circuit elements to address longstanding questions about neural circuit dynamics. Second, relevant to neuropsychiatric disease questions, we have used this approach for depth targeting of hypothalamic cells (in this case, the hypocretin/orexin cells in the lateral hypothalamus), establishing for the first time a causal relationship between frequency-dependent activity of genetically defined neurons important in clinical neuropsychiatric disease and a complex orchestrated mammalian behavior. We also are now applying fast optical control and optical imaging to animal models of depression, Parkinson’s Disease, and altered social behavior relevant to autism. Insights into both normal circuit function and disease mechanisms are beginning to emerge from this multidisciplinary technological approach. Prof. Deisseroth is hosted by the students of the Department of Neurobiology, as a part of the departmental students-invited visiting scientist program.

Optogenetics:Technology Development

Lecture
Date:
Sunday, December 14, 2008
Hour: 14:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Karl Deisseroth
|
Depts of Bioengineering& Psychiatry, Stanford University

In 1979, Francis Crick delineated the major challenges facing neuroscience and called for a technology by which all neurons of just one type could be controlled, “leaving the others more or less unaltered”. A new set of technologies now called optogenetics, synthesizing microbial opsins and solid-state optics, has achieved the goal of millisecond-precision bidirectional control of defined cell types in freely behaving mammals. ChR2 was the first microbial opsin brought to neurobiology, where we initially found that ChR2-expressing neurons can fire blue light-triggered action potentials with millisecond precision, as a result of depolarizing cation flux, without addition of chemical cofactors; this approach has since proven versatile across a variety of preparations. Second, in work stimulated by the finding that the all-trans retinal chromophore required by microbial opsins appears already present within mammalian brains, so that no chemical cofactor need be supplied, we found that neurons targeted to express the light-activated chloride pump halorhodopsin from Natronomonas pharaonis (NpHR) can be hyperpolarized and inhibited from firing action potentials when exposed to yellow light in intact tissue and behaving animals; because of the excitation wavelength difference, the two optical gates can be simultaneously used in the same cells even in vivo5. Third, we employed genomic strategies to discover and adapt for neuroscience a third major optogenetic tool, namely a cation channel (VChR1) with action spectrum significantly redshifted relative to ChR2, to allow tests of the combinatorial interaction of cell types in circuit computation or behavior. Fourth, we have developed genetic targeting tools for versatile use of microbial opsins with existing resources including cell type-specific promoter fragments or Cre-LoxP mouse driver lines suitable for a wide variety of neuroscience investigations. Finally, we have developed integrated fiberoptic and solid-state optical approaches to provide the complementary technology to allow specific cell types, even deep within the brain, to be controlled in freely behaving mammals. Prof. Deisseroth is hosted by the students of the Department of Neurobiology, as a part of the departmental students-invited visiting scientist program.

As Our Brain Is, So We Are

Lecture
Date:
Monday, December 1, 2008
Hour: 12:15
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Prof. Fred Travis
|
Center for Brain, Consciousness, and Cognition Maharishi University of Management, Fairfield, IA

Brain functioning underlies perception of outer objects and supports behavioral responses to environmental challenges. As brain circuits mature in the first 20 years of life, so mental abilities emerge. This talk will examine the relation between brain maturation—synaptogenesis and myelination— and levels of cognitive, moral, and ego development. Learning disabilities, such as ADHD and reading disabilities will be explored in light of associated brain patterns. Effects of experiences on brain functioning will also be examined including effects of restrictive experiences such as stress, drug use and fatigue, and enhancing experiences, such as Transcendental Meditation practice. High levels of human potential will be discussed in terms of enhanced brain functioning.

Role of dopamine systems in addiction

Lecture
Date:
Wednesday, November 26, 2008
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Prof. Marco Diana
|
Laboratory of Cognitive Neuroscience Dept of Drug Sciences, University of Sassari, Italy

Dopamine neurons of the VTA, that project to the Nucleus Accumbens, have been involved in the initial rewarding properties of addicting compounds and, more appropriately, in the long-lasting changes observed after chronic drug administration and subsequent withdrawal. Indeed, alcohol, opiates cannabinoids and other substances provoke, upon withdrawal, a drastic and marked reduction of dopaminergic tone. In addition, aversive, non drug-related stimuli also reduce dopaminergic physiological tone. Furthermore, recent human studies reported an attenuated response to methylphenidate in alcoholic subjects and a lower (than controls) dopaminergic tone. These changes are paralleled by a lower number of D2 receptors and suggest a general “impoverishment” of dopamine transmission in the addicted brain. Accordingly, a dopamine deficit correlated with alcohol craving, which was associated with a high relapse risk. Similar results were reported for nicotine withdrawn rats. This hypodopaminergic state could be the target of therapies aimed at restoring the deficient dopamine transmission observed after chronic drug administration in preclinical and clinical investigations.

Interaction between the amygdala and the prefrontal cortex in emotional memory

Lecture
Date:
Tuesday, November 25, 2008
Hour: 12:30
Location:
Jacob Ziskind Building
Dr. Mouna Maroun
|
Department of Neurobiology and Ethology University of Haifa

The amygdala and the medial prefrontal cortex interact to guide emotional behavior. Alterations in the balance between these two structures can lead to persistent fear associations and to the development of anxiety disorders. In this talk I will present work from my laboratory studying the interaction between these two structures in normal conditions and when exposed to a fearful or stressful experience. We have recently found that fear and extinction learning induce differential changes in these two structures that could hint on the mechanisms by which these structures encode memories of fear and safety.

ON THE RELATIONSHIP BETWEEN MOTOR AND PERCEPTUAL BEHAVIOR –

Lecture
Date:
Wednesday, November 12, 2008
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Dr. Andrei Gorea
|
Laboratoire Psychologie de la Perception CNRS & Paris Descartes University

Starting with Goodale & Milner's (1992) neuropsychological observations, a large number of neuropsychological and psychophysical studies has documented a putative dissociation between perception and action. However, a closer inspection of this literature reveals a number of methodological and conceptual shortcomings. I shall present a series of experiments making use of a variety of psychophysical techniques designed to gauge the relationship between Response Times as well Saccade Perturbations and observers' Perceptual States as assessed for not-masked and masked (metacontrast) stimuli via Yes/No, Temporal Order Judgments and Anticipation Response Times paradigms. All these studies reveal a strong action-perceptual state correlation indicating that motor and perceptual responses are based on a unique internal response. A one-path-two-decisions stochastic race model drawing on standard Signal Detection Theory provides a fair account of some of these data, hence overruling the necessity of a two-paths model of visual processing.

New insights into the hallmarks of obsessive-compulsive disorder (OCD): The prevalence of incompleteness and pessimal behavior

Lecture
Date:
Tuesday, November 11, 2008
Hour: 12:15
Location:
Jacob Ziskind Building
Prof. David Eilam
|
Dept of Zoology, Tel Aviv University

Performance of OCD patients was compared with that of matched normal individuals who were asked to perform the same task that the patients ascribed to their performance. Sequences of consecutive functional acts were long in controls and short in OCD, whereas sequences of non-functional acts were short in controls and long in OCD. Non-functional acts accumulated as a "tail" after the natural termination of the task, supporting the notion of incompleteness as an underling mechanism in OCD. It is suggested that the identified properties are consistent with a recent hypothesis that the individual's attention in OCD shifts from a normal focus on structured actions to a pathological attraction onto the processing of basic acts, a shift that invariably overtaxes memory. Such characteristics and mechanisms of compulsive rituals may prove useful in objective assessment of psychiatric disorders, behavioral therapy, and OCD nosology.

An embedded subnetwork of highly active neurons in the cortex

Lecture
Date:
Wednesday, November 5, 2008
Hour: 14:30
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Dr. Lina Yassin
|
Dept of Biological Sciences & Center for the Neural Basis of Cognition Carnegie Mellon University, Pittsburgh, PA

In vivo and in vitro, spontaneous and evoked neuronal activity are sparsely distributed across neocortical networks, where only a small subset of cells show firing rates greater than 1 Hz. Understanding the stability, network connectivity, and functional properties of this active subpopulation has been hampered by an inability to identify and characterize these neurons in vitro. Here we use expression of a fosGFP transgene to identify and characterize the properties of cells with a recent history of elevated activity. Neurons that had induced fosGFP expression in vivo maintained elevated firing rates in vitro over the course of many hours. Paired-cell recordings indicated that fosGFP+ neurons have a greater likelihood of being connected to each other, both directly and indirectly. These findings indicate that highly active neuronal ensembles are maintained over long time periods and suggest that specific, identifiable groups of neurons may dominate the way information is represented in the neocortex.

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