2007
All events, 2007
Computational physiology of the high frequency discharge and pauses of basal ganglia neurons
Lecture
Monday, January 15, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Computational physiology of the high frequency discharge and pauses of basal ganglia neurons
Prof. Hagai Bergman
Department of Physiology, Faculty of Medicine, The Hebrew University of Jerusalem
The neurons of many basal ganglia nuclei, including the external and internal globus pallidus (GPe, GPi respectively) and the substantia nigra pars reticulta (SNr) are characterized by their high-frequency (50-100 spikes/s) tonic discharge (HFD). However, the high firing rate of GPe neurons is interrupted by long pauses. To provide insight into the GPe pause physiology, we developed an objective criterion for the quality of the isolation of extracellularly recorded spikes and studied the spiking activity of 212 well-isolated HFD GPe and 52 GPi/SNr neurons from five monkeys during different states of behavioral activity. An algorithm which maximizes the surprise function was used to detect pauses and pauser-cells ("pausers").
Only 6% of the GPi/SNr neurons vs. as many as 56% of the GPe neurons were classified as pausers. The average pause duration equals 0.6s and follows a Poissonian distribution with a frequency of 13 pauses/minute. No linear relation was found between pause parameters (duration or frequency) and the firing rate of the cell. Pauses were preceded by various changes in firing rate but not dominantly by a decrease. The average amplitude and duration of the spike waveform was modulated only after the pause but not before it. Pauses of pairs of cells which were recorded simultaneously were not correlated. The probability of GPe cells to pause spontaneously was extremely variable among monkeys (30-90%) and inversely related to the degree of the monkey's motor activity.
These findings suggest that spontaneous GPe pauses are neither triggered by an intrinsic cellular mechanism nor by slow global changes in the extracellular medium and probably reflect a network property of the basal ganglia related to low-arousal and network exploration periods.
Conversion of sensory signals into perceptual decisions
Lecture
Monday, January 8, 2007
Hour: 14:00
Location:
Arthur and Rochelle Belfer Building for Biomedical Research
Conversion of sensory signals into perceptual decisions
Prof. Ranulfo Romo
National Autonomous University of Mexico
Multi-regional Interactions support memory formation: modulation of the Rhinal cortices by the Amygdala and the mPFC
Lecture
Monday, January 8, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Multi-regional Interactions support memory formation: modulation of the Rhinal cortices by the Amygdala and the mPFC
Dr. Rony Paz
Center for Molecular & Behavioral Neuroscience, Rutgert University, New-Jersey
When is it worth working: Behavioral, physiological, genetic, and modeling experiments investigating motivation and reward expectancy
Lecture
Sunday, January 7, 2007
Hour: 10:00 - 11:00
Location:
Nella and Leon Benoziyo Building for Brain Research
When is it worth working: Behavioral, physiological, genetic, and modeling experiments investigating motivation and reward expectancy
Dr. Barry J. Richmond
Chief, Section on Neural Coding and Computation Laboratory of Neuropsychology, National Institute of Mental Health,
NIH, DHHS, USA
The intensity or vigor of goal-directed behavior is a correlate of the motivation underlying it. Motivation is related to the subjective value of rewards and is moderated, or even completely dissipated, if the perceived effort or discomfort seems too great. Under what circumstances do we seek a goal or a reward? To study motivated behavior in monkeys, we use several variants of a task in which monkeys must perform some work, in this case detecting when a target spot turns from red-to-green, to obtain a drop of juice. We use another visual stimulus, a cue, to indicate how much discomfort must be endured, e.g., the number of trials to be worked, to obtain the reward. The monkeys learn about the cues quickly, often after just a few trials. The number of errors becomes proportional to amount of work remaining before reward, achieving our goal of manipulating motivation. This is a behavior in which the monkeys decrease their performance in response to an increased predicted workload. Temporal difference models have provided an important framework for interpreting goal directed-behavior, and in economics, game theory has been used to model choice behavior. A key concept in these models is to determine how the value of the reward is modulated by some parameter of the experiment, such as changing the reward size, or the amount of time needed to obtain the reward. In learning or adaptation the TD algorithm predicts that behavior should be (and in artificial systems is) adapted to maximize long-term reward. By examining the influence of reward size, waiting time, and amount of work, we can examine in what ways different model succeed and fail. Our data show that performances depend on work completed since preceding reward (sunk cost effect), and accumulated reward (over whole sessions) and work. In addition this behavior can be used to learn about categorization and rule learning. Using single neuronal recording, regional ablation, and molecular ablation of the D2 receptor we show that dopamine-rich brain regions have signals related to the balance between reward and work.
Stress and the Brain – a Molecular View
Lecture
Tuesday, January 2, 2007
Hour: 12:00 - 13:15
Location:
Nella and Leon Benoziyo Building for Brain Research
Stress and the Brain – a Molecular View
Dr. Daniela Kaufer
Department of Integrative Biology
Helen Wills Neuroscience Institute, University of California
Berkeley, CA
My lab studies the molecular basis of neural and hormonal mechanisms of stress responses. Using interdisciplinary multilevel approach we look at the plasticity of the brain in dealing with physiological and pathological events. In this talk I will describe three current projects: Hormonal Regulation of Neural Stem Cells. Determining the environmental and internal cues that control the proliferation and fate choices of stem cells in the adult hippocampus, and their role in functional plasticity. RNA Regulatory Mechanisms in Neural Stress Responses. RNA regulation, specifically, alternative splicing and microRNA expression as a fine tuning neural stress mechanism. The Molecular Mechanisms of post-trauma Epileptogenesis. Determine the mechanism underlying epileptogenesis following blood brain barrier damage.
Synaptic maintenance - Insights from live imaging experiments
Lecture
Monday, January 1, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Synaptic maintenance - Insights from live imaging experiments
Dr. Noam Ziv
Dept of Physiology, Faculty of Medicine, Technion
Recent studies suggest that central nervous system (CNS) synapses persist
for many weeks, months and even lifetimes, yet little is
known on the mechanisms that allow these structures to persist for so
long despite the many deconstructive processes acting at biological
systems and neurons in particular. As a step toward a better
understanding of synaptic maintenance we set out to examine some of the
deconstructive and reconstructive forces acting at individual CNS
synapses. To that end we studied the molecular dynamics of several
presynaptic and postsynaptic cytomatrix molecules. Fluorescence
recovery after photobleaching (FRAP) and photoactivation experiments
revealed that these molecules are continuously incorporated into and lost
from individual synaptic structures within tens of minutes.
Moreover, these dynamics can be accelerated by synaptic activity.
Finally, we find that synaptic molecules are continuously exchanged
between nearby synaptic structures at similar rates and that these rates
greatly exceed the rates at which synapses are replenished with molecules
arriving from somatic sources. Our findings indicate that the dynamics of
key synaptic matrix molecules may be dominated by local protein exchange
and redistribution, whereas protein synthesis and degradation serve to
maintain and regulate the sizes of local, shared pools of these proteins.
The nature of these dynamics raises intriguing questions as to how
synapses manage to maintain their
individual, use-dependent structural and functional characteristics over
long durations.
Pages
2007
All events, 2007
Multi-regional Interactions support memory formation: modulation of the Rhinal cortices by the Amygdala and the mPFC
Lecture
Monday, January 8, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Multi-regional Interactions support memory formation: modulation of the Rhinal cortices by the Amygdala and the mPFC
Dr. Rony Paz
Center for Molecular & Behavioral Neuroscience, Rutgert University, New-Jersey
When is it worth working: Behavioral, physiological, genetic, and modeling experiments investigating motivation and reward expectancy
Lecture
Sunday, January 7, 2007
Hour: 10:00 - 11:00
Location:
Nella and Leon Benoziyo Building for Brain Research
When is it worth working: Behavioral, physiological, genetic, and modeling experiments investigating motivation and reward expectancy
Dr. Barry J. Richmond
Chief, Section on Neural Coding and Computation Laboratory of Neuropsychology, National Institute of Mental Health,
NIH, DHHS, USA
The intensity or vigor of goal-directed behavior is a correlate of the motivation underlying it. Motivation is related to the subjective value of rewards and is moderated, or even completely dissipated, if the perceived effort or discomfort seems too great. Under what circumstances do we seek a goal or a reward? To study motivated behavior in monkeys, we use several variants of a task in which monkeys must perform some work, in this case detecting when a target spot turns from red-to-green, to obtain a drop of juice. We use another visual stimulus, a cue, to indicate how much discomfort must be endured, e.g., the number of trials to be worked, to obtain the reward. The monkeys learn about the cues quickly, often after just a few trials. The number of errors becomes proportional to amount of work remaining before reward, achieving our goal of manipulating motivation. This is a behavior in which the monkeys decrease their performance in response to an increased predicted workload. Temporal difference models have provided an important framework for interpreting goal directed-behavior, and in economics, game theory has been used to model choice behavior. A key concept in these models is to determine how the value of the reward is modulated by some parameter of the experiment, such as changing the reward size, or the amount of time needed to obtain the reward. In learning or adaptation the TD algorithm predicts that behavior should be (and in artificial systems is) adapted to maximize long-term reward. By examining the influence of reward size, waiting time, and amount of work, we can examine in what ways different model succeed and fail. Our data show that performances depend on work completed since preceding reward (sunk cost effect), and accumulated reward (over whole sessions) and work. In addition this behavior can be used to learn about categorization and rule learning. Using single neuronal recording, regional ablation, and molecular ablation of the D2 receptor we show that dopamine-rich brain regions have signals related to the balance between reward and work.
Stress and the Brain – a Molecular View
Lecture
Tuesday, January 2, 2007
Hour: 12:00 - 13:15
Location:
Nella and Leon Benoziyo Building for Brain Research
Stress and the Brain – a Molecular View
Dr. Daniela Kaufer
Department of Integrative Biology
Helen Wills Neuroscience Institute, University of California
Berkeley, CA
My lab studies the molecular basis of neural and hormonal mechanisms of stress responses. Using interdisciplinary multilevel approach we look at the plasticity of the brain in dealing with physiological and pathological events. In this talk I will describe three current projects: Hormonal Regulation of Neural Stem Cells. Determining the environmental and internal cues that control the proliferation and fate choices of stem cells in the adult hippocampus, and their role in functional plasticity. RNA Regulatory Mechanisms in Neural Stress Responses. RNA regulation, specifically, alternative splicing and microRNA expression as a fine tuning neural stress mechanism. The Molecular Mechanisms of post-trauma Epileptogenesis. Determine the mechanism underlying epileptogenesis following blood brain barrier damage.
Synaptic maintenance - Insights from live imaging experiments
Lecture
Monday, January 1, 2007
Hour: 12:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Synaptic maintenance - Insights from live imaging experiments
Dr. Noam Ziv
Dept of Physiology, Faculty of Medicine, Technion
Recent studies suggest that central nervous system (CNS) synapses persist
for many weeks, months and even lifetimes, yet little is
known on the mechanisms that allow these structures to persist for so
long despite the many deconstructive processes acting at biological
systems and neurons in particular. As a step toward a better
understanding of synaptic maintenance we set out to examine some of the
deconstructive and reconstructive forces acting at individual CNS
synapses. To that end we studied the molecular dynamics of several
presynaptic and postsynaptic cytomatrix molecules. Fluorescence
recovery after photobleaching (FRAP) and photoactivation experiments
revealed that these molecules are continuously incorporated into and lost
from individual synaptic structures within tens of minutes.
Moreover, these dynamics can be accelerated by synaptic activity.
Finally, we find that synaptic molecules are continuously exchanged
between nearby synaptic structures at similar rates and that these rates
greatly exceed the rates at which synapses are replenished with molecules
arriving from somatic sources. Our findings indicate that the dynamics of
key synaptic matrix molecules may be dominated by local protein exchange
and redistribution, whereas protein synthesis and degradation serve to
maintain and regulate the sizes of local, shared pools of these proteins.
The nature of these dynamics raises intriguing questions as to how
synapses manage to maintain their
individual, use-dependent structural and functional characteristics over
long durations.
Pages
2007
All events, 2007
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