All events, All years

Fragmenting the self: brainwide recording and the neurobiology of dissociation

Lecture
Date:
Wednesday, April 13, 2022
Hour: 12:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Dr. Isaac Kauvar
|
Postdoc, Neuroscience Institute, Stanford University

Advanced methods now allow fast, cellular-level recording of neural activity across the mammalian brain, enabling exploration of how brain-wide dynamical patterns might give rise to complex behavioral states, such as the clinically important state of dissociation. We established a dissociation-like state in mice, induced by administration of ketamine or phencyclidine. Large-scale neural recording revealed that these dissociative agents elicited a 1–3-Hz rhythm in layer 5 neurons of retrosplenial cortex, uncoupled from most other brain regions except thalamus. Additionally, using brain-wide intracranial electrical recording in a patient with focal epilepsy, the human experience of dissociation was linked to a similar ~3 Hz rhythm in posteromedial cortex (homologous to mouse retrosplenial cortex), and stimulation of this area induced dissociation.   

Daily normalization of E/I-ratio by light-driven transcription maintains visual processing by Dahlia Kushinsky, PhD Student, Advisor: Dr. Ivo Spiegel and Isolated correlates of perception in the posterior cortex by Michael Sokoletsky, PhD Student, Advisor

Lecture
Date:
Tuesday, April 12, 2022
Hour: 12:30 - 13:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Dahlia Kushinsky, PhD Student, Advisor: Dr. Ivo Spiegel and Michael Sokoletsky, PhD Student, Advisor: Prof. Ilan Lampl
|
Students Seminar Department of Brain Sciences

Dahlia Kushinsky- Daily normalization of E/I-ratio by light-driven transcription maintains visual processing Abstract: Consistent and reliable encoding of sensory information is essential for an animal’s survival. However, sensory input in an animal’s environment is constantly changing, likely resulting in changes in the brain at the level of molecules, synapses, and cellular circuitry. It is therefore unclear which elements of the system are stable or dynamic, and what mechanisms allow for overall stability of the brain throughout an animal’s life. To address this question, we focused on the visual cortex of adult mice and took advantage of the daily sensory transitions from the dark of night to daylight and back to darkness during a single day. By using RNA-seq, patch clamp slice electrophysiology, and in vivo longitudinal calcium imaging in awake mice, we monitor the light driven changes in molecules, synapses, and cells across a single day. At each of these levels (molecular, synaptic, and cellular), we find rapid sensory-driven increases shortly after transition from darkness to light which is then normalized later in the day. Based on these findings, we suggest that sensory-driven genetic changes maintain functional stability of neural circuits by regulating E/I ratio in excitatory neurons every day. Michael Sokoletsy- Isolated correlates of perception in the posterior cortex Abstract: To uncover the neural mechanisms of stimulus perception, experimenters commonly use tasks in which subjects are repeatedly presented with a weak stimulus and instructed to report, via movement, if they perceived the stimulus. The difference in neural activity between reported stimulus (hit) and unreported stimulus (miss) trials is then seen as potentially perception-related. However, recent studies found that activity related to the report spreads throughout the brain, calling into question to what extent such tasks may be conflating activity that is perception-related with activity that is report-related. To isolate perception-related activity, we developed a paradigm in which the same mice were trained to report either the presence or absence of a whisker stimulus. We found that isolated perception-related activity appeared within a posterio-parietal network of cortical regions contralateral to the stimulus, was on average an order of magnitude lower than the hit versus miss difference, and began just after the low-level stimulus response. In addition, we performed controls to check that it is specifically associated with performance and is not the result of differences in time or uninstructed movements across the tasks. In summary, we revealed for the first time in mice the cortical areas that are associated specifically with the perception of a sensory stimulus and independently of the report.

Conscious intentions during voluntary action formation

Lecture
Date:
Tuesday, April 5, 2022
Hour: 12:30 - 13:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Dr. Uri Maoz
|
Computational Neuroscience Chapman University Visiting Assistant Professor-UCLA Visiting Associate-Caltech

Investigating conscious intentions associated with spontaneous, voluntary action is challenging. Typical paradigms inherently lack the stimulus-response structure that is common in neuroscientific tasks (Haggard, 2019). Moreover, studying the onset of intentions has proven notoriously difficult, conceptually and empirically. Measuring the onset of intentions with a clock was shown to be inconsistent, biased, and unreliable (Maoz et al., 2015). Furthermore, probe methods estimated intention onset much earlier than clock-based methods (Matsuhashi & Hallett, 2008), complicating the reconciliation of these results. Some have even questioned the existence of intentions as discrete, causal neural states (Schurger & Utihol, 2015).

The impact of metabolic processes at the brain’s choroid plexus and of the gut microbiome on Alzheimer’s disease manifestation

Lecture
Date:
Thursday, March 24, 2022
Hour: 16:00
Location:
Afroditi Tsitsou-Kampeli
|
Prof. Michal Schwartz Lab Dept of Brain Sciences

The immune system and the gut microbiome are becoming major players in chronic neurodegenerative conditions. One of the key interfaces between the brain and the immune system with an impact on brain function is the choroid plexus (CP). The CP interface is central to the maintenance of brain homeostasis by exerting a plethora of different biological processes. However, in aging and Alzheimer’s disease (AD), interferon type-I (IFN-I) signaling accumulates at the CP and impedes part of its beneficial function by inducing a CP-pro-aging signature. My research contributed to the finding that IFN-I signaling at the CP induces an aging-like signature in microglia and impedes cognitive abilities in middle-aged mice in a microglia-dependent manner. In addition, I demonstrated that the brain-specific enzyme, cholesterol 24-hydroxylase (CYP46A1), is expressed by the CP epithelium and that its product, 24-hydroxycholesterol (24-OH), downregulates CP-pro-inflammatory signatures. Furthermore, in AD, CP CYP46A1 protein levels were decreased in both mice and humans and overexpression of Cyp46a1 at the CP in 5xFAD mice reversed brain inflammation, microglial dysfunction signatures, and cognitive loss. Finally, while the pro-inflammatory cytokine TNF-α impaired CP Cyp46a1 expression in vitro, boosting systemic immunity in vivo increased its levels in an IFNGR2-dependent manner. These results highlight CYP46A1 at the CP as a remote regulator of brain inflammation, which diminishes with neurodegeneration, but is amenable to rescue. Focusing on the gut microbiome, I found that 5xFAD mice devoid of microbiome exhibited a striking decrease of long-term spatial memory deficit and increased synaptic and neuronal survival. Spatial memory deficit in 5xFAD mice kept in germ free (GF) or specific-pathogen free (SPF) conditions, negatively correlated with the abundance of 2-hydroxypyridine, while systemic, chronic supply of 2-hydroxypyridine in SPF 5xFAD mice improved spatial memory deficits in comparison to phosphate-buffered saline (PBS)-supplied 5xFAD mice. Overall, these findings demonstrate a microbiome-dependent effect on AD pathology in the 5xFAD mouse model and suggest a connection between 2-hydroxypyridine and AD manifestation. In general, this research thesis addresses novel aspects of choroid plexus and gut microbiome metabolism and their relation to AD progression. Zoom link https://weizmann.zoom.us/j/98658552127?pwd=ZkZmWTBkd1AxZ0xPbGlpU3FPUWpzUT09 Meeting ID:986 5855 2127 Password:495213

Cracking the olfactory code using behavior

Lecture
Date:
Sunday, March 13, 2022
Hour: 10:00 - 11:00
Location:
Gerhard M.J. Schmidt Lecture Hall
Prof. Dmitry Rinberg
|
Dept of Neuroscience and Physiology, NYU

Two of the most fundamental questions of sensory neuroscience are: 1) how is stimulus information represented by neuronal activity? and 2) what features of this activity are read out to guide behavior? The first question has been the subject of a large body of work across different sensory modalities. The second question remains a significant challenge, since one needs to establish a causal link between neuronal activity and behavior. In olfaction, it has been proposed that information about odors is encoded in spatial distribution of receptor activation and the next level mitral/tufted cells, as well as in their relative timing and synchrony. However, the role of different features of neural activity in guiding behavior remains unknown. Using mouse olfaction as a model system, we developed both technological and conceptual approaches to study sensory coding by perturbing neural activity at different levels of information processing during sensory driven behavioral tasks. We developed methods for both one-photon spatiotemporal pattern stimulation using digital mirror devices at the glomerulus level in the olfactory bulb, and two-photon holographic pattern stimulation deeper in the brain, at the level of mitral/tufted cells. Using these techniques, we performed quantitative behavioral experiments to, first, measure psychophysical limits of the readability of different features of the neural code, and, second, to quantify their behavioral relevance. Based on these results, we built a detailed mathematical model of the behavioral relevance of the different features of spatiotemporal neural activity. Our approach can be potentially generalized to other sensory systems. Link: https://weizmann.zoom.us/j/95406893197?pwd=REt5L1g3SmprMUhrK3dpUDJVeHlrZz09 Meeting ID: 954 0689 3197 Password: 750421

Brain-computer interfaces for basic science

Lecture
Date:
Thursday, March 10, 2022
Hour: 12:30 - 13:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Prof. Byron Yu
|
Carnegie Mellon University, Pittsburgh

Abstract: Brain-computer interfaces (BCI) translate neural activity into movements of a computer cursor or robotic limb. BCIs are known for their ability to assist paralyzed patients. A lesser known, but increasingly important, use of BCIs is their ability to further our basic scientific understanding of brain function. In particular, BCIs are providing insights into the neural mechanisms underlying sensorimotor control that are currently difficult to obtain using limb movements. In this talk, I will demonstrate how a BCI can be leveraged to study how the brain learns. Specifically, I will address why learning some tasks is easier than others, as well as how populations of neurons change their activity in concert during learning. Brief bio: Byron Yu received the B.S. degree in Electrical Engineering and Computer Sciences from the University of California, Berkeley in 2001. He received the M.S. and Ph.D. degrees in Electrical Engineering in 2003 and 2007, respectively, from Stanford University. From 2007 to 2009, he was a postdoctoral fellow jointly in Electrical Engineering and Neuroscience at Stanford University and at the Gatsby Computational Neuroscience Unit, University College London. He then joined the faculty of Carnegie Mellon University in 2010, where he is a Professor in Electrical & Computer Engineering and Biomedical Engineering, and the Gerard G. Elia Career Development Professor. He is broadly interested in how large populations of neurons process information, from encoding sensory stimuli to driving motor actions. His group develops and applies novel statistical algorithms and uses brain-computer interfaces to study brain function. Link- https://weizmann.zoom.us/j/95406893197?pwd=REt5L1g3SmprMUhrK3dpUDJVeHlrZz09 Meeting ID: 954 0689 3197 Password: 750421

Neural representation geometry: a mesoscale approach linking learning to complex behavior

Lecture
Date:
Monday, March 7, 2022
Hour: 14:00 - 15:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Stefano Recanatesi
|
University of Washington, Seattle

I will demonstrate how neural representation geometry may hold the key to linking animal behavior and learning to circuit mechanisms. We will proceed in three steps. 1) We will start by establishing a connection between the sequential dynamics of complex behavior and geometrical properties of neural representations. 2) We will then link these geometrical properties to underlying circuit components. Specifically, we will uncover connectivity mechanisms that allow the circuit to control the geometry of its representations. 3) Finally, we will investigate how key geometrical structures emerge, de novo, through learning. To answer this, we will analyze the learning of representations in feedforward and recurrent neural networks trained to perform predictive tasks using machine learning techniques. As a result, we will show how both learning mechanisms and behavioral demands shape the geometry of neural representations.

Looking at night vision

Lecture
Date:
Tuesday, March 1, 2022
Hour: 12:30
Location:
Prof. Shabtai Barash
|
Department of Brain Sciences, WIS

The architecture of the primate visual system is based on the fovea-fixation-saccade system for high-acuity vision. This talk will describe an analogous system in night vision of monkeys. Processing is based not on the fovea but on a ‘scotopic center’. Unlike the fovea, which is fixed in the retina, the scotopic center relocates over a ‘scotopic band’, according to the intensity of the ambient light and, more generally, perceptual uncertainty. The eye movements involved have sensorimotor transformations specific to night vision. The discussion will touch on the evolution of vision, including relevance for humans. Link: https://weizmann.zoom.us/j/95406893197?pwd=REt5L1g3SmprMUhrK3dpUDJVeHlrZz09 Meeting ID: 954 0689 3197 Password: 750421  

Effects of physical exercise and adult neurogenesis on hippocampal neural codes

Lecture
Date:
Thursday, February 10, 2022
Hour: 09:00 - 10:00
Location:
Yoav Rechavi - PhD Thesis Defense on Zoom
|
Prof. Yaniv Ziv, Lab Department of Brain Sciences

ABSTRACT Physical activity plays a vital role in maintaining a healthy brain, augmenting memory and cognition in both humans and animals. Previous studies have identified multiple distinct molecular and cellular factors that mediate these effects, both within the brain and systemically. However, what remains unknown is how exercise affects the neural coding mechanisms that underlie these cognitive and memory abilities. In my work I addressed this question in the context of spatial cognition, and studied how chronic voluntary exercise affects the quality and the long-term stability of hippocampal place codes. I performed longitudinal imaging of calcium activity in the hippocampal CA1 of mice as they repeatedly explored initially novel environments over weeks, and compared the place codes of mice that voluntarily ran on wheels in their home cage to those of sedentary mice. As previously reported, physical activity enhanced adult neurogenesis rates in the hippocampal dentate gyrus in the running group. I found that running increased the firing rates and the information content that place cells carry about position. In addition, I discovered a surprising relationship between physical activity and long-term neural-code stability: although running mice demonstrated an overall more stable place code than sedentary mice, their place code exhibited a higher degree of representational drift when controlling for code quality level. Using a simulated neural network, I found that the combination of both improved code quality and faster representational drift in runners, but neither of these effects alone, could recapitulate my experimental results. Overall, these results imply a role for physical activity in both improving the spatial code and accelerating representational drift in the hippocampus. Zoom link-https://weizmann.zoom.us/j/93585241611?pwd=RGsxakU2aElVQ01nbUpuRjVqOWQ0QT09 Meeting ID: 935 8524 1611 Password: 243908

Theory of neural perturbome

Lecture
Date:
Tuesday, February 1, 2022
Hour: 12:30
Location:
Prof. Claudia Clopath
|
Department of Bioengineering Imperial College London, UK

To unravel the functional properties of the brain, we need to untangle how neurons interact with each other and coordinate in large-scale recurrent networks. One way to address this question is to measure the functional influence of individual neurons on each other by perturbing them in vivo. Application of such single-neuron perturbations in mouse visual cortex has recently revealed feature- specific suppression between excitatory neurons, despite the presence of highly specific excitatory connectivity, which was deemed to underlie feature-specific amplification. Here, we studied which connectivity profiles are consistent with these seemingly contradictory observations, by modeling the effect of single-neuron perturbations in large-scale neuronal networks. Our numerical simulations and mathematical analysis revealed that, contrary to the prima facie assumption, neither inhibition dominance nor broad inhibition alone were sufficient to explain the experimental findings; instead, strong and functionally specific excitatory–inhibitory connectivity was necessary, consistent with recent findings in the primary visual cortex of rodents. Such networks had a higher capacity to encode and decode natural images, and this was accompanied by the emergence of response gain nonlinearities at the population level. Our study provides a general computational framework to investigate how single-neuron perturbations are linked to cortical connectivity and sensory coding and paves the road to map the perturbome of neuronal networks in future studies. Zoom Link: https://weizmann.zoom.us/j/95406893197?pwd=REt5L1g3SmprMUhrK3dpUDJVeHlrZz09 Meeting ID: 954 0689 3197 Password: 750421

Pages

All events, All years

Daily normalization of E/I-ratio by light-driven transcription maintains visual processing by Dahlia Kushinsky, PhD Student, Advisor: Dr. Ivo Spiegel and Isolated correlates of perception in the posterior cortex by Michael Sokoletsky, PhD Student, Advisor

Lecture
Date:
Tuesday, April 12, 2022
Hour: 12:30 - 13:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Dahlia Kushinsky, PhD Student, Advisor: Dr. Ivo Spiegel and Michael Sokoletsky, PhD Student, Advisor: Prof. Ilan Lampl
|
Students Seminar Department of Brain Sciences

Dahlia Kushinsky- Daily normalization of E/I-ratio by light-driven transcription maintains visual processing Abstract: Consistent and reliable encoding of sensory information is essential for an animal’s survival. However, sensory input in an animal’s environment is constantly changing, likely resulting in changes in the brain at the level of molecules, synapses, and cellular circuitry. It is therefore unclear which elements of the system are stable or dynamic, and what mechanisms allow for overall stability of the brain throughout an animal’s life. To address this question, we focused on the visual cortex of adult mice and took advantage of the daily sensory transitions from the dark of night to daylight and back to darkness during a single day. By using RNA-seq, patch clamp slice electrophysiology, and in vivo longitudinal calcium imaging in awake mice, we monitor the light driven changes in molecules, synapses, and cells across a single day. At each of these levels (molecular, synaptic, and cellular), we find rapid sensory-driven increases shortly after transition from darkness to light which is then normalized later in the day. Based on these findings, we suggest that sensory-driven genetic changes maintain functional stability of neural circuits by regulating E/I ratio in excitatory neurons every day. Michael Sokoletsy- Isolated correlates of perception in the posterior cortex Abstract: To uncover the neural mechanisms of stimulus perception, experimenters commonly use tasks in which subjects are repeatedly presented with a weak stimulus and instructed to report, via movement, if they perceived the stimulus. The difference in neural activity between reported stimulus (hit) and unreported stimulus (miss) trials is then seen as potentially perception-related. However, recent studies found that activity related to the report spreads throughout the brain, calling into question to what extent such tasks may be conflating activity that is perception-related with activity that is report-related. To isolate perception-related activity, we developed a paradigm in which the same mice were trained to report either the presence or absence of a whisker stimulus. We found that isolated perception-related activity appeared within a posterio-parietal network of cortical regions contralateral to the stimulus, was on average an order of magnitude lower than the hit versus miss difference, and began just after the low-level stimulus response. In addition, we performed controls to check that it is specifically associated with performance and is not the result of differences in time or uninstructed movements across the tasks. In summary, we revealed for the first time in mice the cortical areas that are associated specifically with the perception of a sensory stimulus and independently of the report.

Conscious intentions during voluntary action formation

Lecture
Date:
Tuesday, April 5, 2022
Hour: 12:30 - 13:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Dr. Uri Maoz
|
Computational Neuroscience Chapman University Visiting Assistant Professor-UCLA Visiting Associate-Caltech

Investigating conscious intentions associated with spontaneous, voluntary action is challenging. Typical paradigms inherently lack the stimulus-response structure that is common in neuroscientific tasks (Haggard, 2019). Moreover, studying the onset of intentions has proven notoriously difficult, conceptually and empirically. Measuring the onset of intentions with a clock was shown to be inconsistent, biased, and unreliable (Maoz et al., 2015). Furthermore, probe methods estimated intention onset much earlier than clock-based methods (Matsuhashi & Hallett, 2008), complicating the reconciliation of these results. Some have even questioned the existence of intentions as discrete, causal neural states (Schurger & Utihol, 2015).

The impact of metabolic processes at the brain’s choroid plexus and of the gut microbiome on Alzheimer’s disease manifestation

Lecture
Date:
Thursday, March 24, 2022
Hour: 16:00
Location:
Afroditi Tsitsou-Kampeli
|
Prof. Michal Schwartz Lab Dept of Brain Sciences

The immune system and the gut microbiome are becoming major players in chronic neurodegenerative conditions. One of the key interfaces between the brain and the immune system with an impact on brain function is the choroid plexus (CP). The CP interface is central to the maintenance of brain homeostasis by exerting a plethora of different biological processes. However, in aging and Alzheimer’s disease (AD), interferon type-I (IFN-I) signaling accumulates at the CP and impedes part of its beneficial function by inducing a CP-pro-aging signature. My research contributed to the finding that IFN-I signaling at the CP induces an aging-like signature in microglia and impedes cognitive abilities in middle-aged mice in a microglia-dependent manner. In addition, I demonstrated that the brain-specific enzyme, cholesterol 24-hydroxylase (CYP46A1), is expressed by the CP epithelium and that its product, 24-hydroxycholesterol (24-OH), downregulates CP-pro-inflammatory signatures. Furthermore, in AD, CP CYP46A1 protein levels were decreased in both mice and humans and overexpression of Cyp46a1 at the CP in 5xFAD mice reversed brain inflammation, microglial dysfunction signatures, and cognitive loss. Finally, while the pro-inflammatory cytokine TNF-α impaired CP Cyp46a1 expression in vitro, boosting systemic immunity in vivo increased its levels in an IFNGR2-dependent manner. These results highlight CYP46A1 at the CP as a remote regulator of brain inflammation, which diminishes with neurodegeneration, but is amenable to rescue. Focusing on the gut microbiome, I found that 5xFAD mice devoid of microbiome exhibited a striking decrease of long-term spatial memory deficit and increased synaptic and neuronal survival. Spatial memory deficit in 5xFAD mice kept in germ free (GF) or specific-pathogen free (SPF) conditions, negatively correlated with the abundance of 2-hydroxypyridine, while systemic, chronic supply of 2-hydroxypyridine in SPF 5xFAD mice improved spatial memory deficits in comparison to phosphate-buffered saline (PBS)-supplied 5xFAD mice. Overall, these findings demonstrate a microbiome-dependent effect on AD pathology in the 5xFAD mouse model and suggest a connection between 2-hydroxypyridine and AD manifestation. In general, this research thesis addresses novel aspects of choroid plexus and gut microbiome metabolism and their relation to AD progression. Zoom link https://weizmann.zoom.us/j/98658552127?pwd=ZkZmWTBkd1AxZ0xPbGlpU3FPUWpzUT09 Meeting ID:986 5855 2127 Password:495213

Cracking the olfactory code using behavior

Lecture
Date:
Sunday, March 13, 2022
Hour: 10:00 - 11:00
Location:
Gerhard M.J. Schmidt Lecture Hall
Prof. Dmitry Rinberg
|
Dept of Neuroscience and Physiology, NYU

Two of the most fundamental questions of sensory neuroscience are: 1) how is stimulus information represented by neuronal activity? and 2) what features of this activity are read out to guide behavior? The first question has been the subject of a large body of work across different sensory modalities. The second question remains a significant challenge, since one needs to establish a causal link between neuronal activity and behavior. In olfaction, it has been proposed that information about odors is encoded in spatial distribution of receptor activation and the next level mitral/tufted cells, as well as in their relative timing and synchrony. However, the role of different features of neural activity in guiding behavior remains unknown. Using mouse olfaction as a model system, we developed both technological and conceptual approaches to study sensory coding by perturbing neural activity at different levels of information processing during sensory driven behavioral tasks. We developed methods for both one-photon spatiotemporal pattern stimulation using digital mirror devices at the glomerulus level in the olfactory bulb, and two-photon holographic pattern stimulation deeper in the brain, at the level of mitral/tufted cells. Using these techniques, we performed quantitative behavioral experiments to, first, measure psychophysical limits of the readability of different features of the neural code, and, second, to quantify their behavioral relevance. Based on these results, we built a detailed mathematical model of the behavioral relevance of the different features of spatiotemporal neural activity. Our approach can be potentially generalized to other sensory systems. Link: https://weizmann.zoom.us/j/95406893197?pwd=REt5L1g3SmprMUhrK3dpUDJVeHlrZz09 Meeting ID: 954 0689 3197 Password: 750421

Brain-computer interfaces for basic science

Lecture
Date:
Thursday, March 10, 2022
Hour: 12:30 - 13:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Prof. Byron Yu
|
Carnegie Mellon University, Pittsburgh

Abstract: Brain-computer interfaces (BCI) translate neural activity into movements of a computer cursor or robotic limb. BCIs are known for their ability to assist paralyzed patients. A lesser known, but increasingly important, use of BCIs is their ability to further our basic scientific understanding of brain function. In particular, BCIs are providing insights into the neural mechanisms underlying sensorimotor control that are currently difficult to obtain using limb movements. In this talk, I will demonstrate how a BCI can be leveraged to study how the brain learns. Specifically, I will address why learning some tasks is easier than others, as well as how populations of neurons change their activity in concert during learning. Brief bio: Byron Yu received the B.S. degree in Electrical Engineering and Computer Sciences from the University of California, Berkeley in 2001. He received the M.S. and Ph.D. degrees in Electrical Engineering in 2003 and 2007, respectively, from Stanford University. From 2007 to 2009, he was a postdoctoral fellow jointly in Electrical Engineering and Neuroscience at Stanford University and at the Gatsby Computational Neuroscience Unit, University College London. He then joined the faculty of Carnegie Mellon University in 2010, where he is a Professor in Electrical & Computer Engineering and Biomedical Engineering, and the Gerard G. Elia Career Development Professor. He is broadly interested in how large populations of neurons process information, from encoding sensory stimuli to driving motor actions. His group develops and applies novel statistical algorithms and uses brain-computer interfaces to study brain function. Link- https://weizmann.zoom.us/j/95406893197?pwd=REt5L1g3SmprMUhrK3dpUDJVeHlrZz09 Meeting ID: 954 0689 3197 Password: 750421

Neural representation geometry: a mesoscale approach linking learning to complex behavior

Lecture
Date:
Monday, March 7, 2022
Hour: 14:00 - 15:00
Location:
Nella and Leon Benoziyo Building for Brain Research
Stefano Recanatesi
|
University of Washington, Seattle

I will demonstrate how neural representation geometry may hold the key to linking animal behavior and learning to circuit mechanisms. We will proceed in three steps. 1) We will start by establishing a connection between the sequential dynamics of complex behavior and geometrical properties of neural representations. 2) We will then link these geometrical properties to underlying circuit components. Specifically, we will uncover connectivity mechanisms that allow the circuit to control the geometry of its representations. 3) Finally, we will investigate how key geometrical structures emerge, de novo, through learning. To answer this, we will analyze the learning of representations in feedforward and recurrent neural networks trained to perform predictive tasks using machine learning techniques. As a result, we will show how both learning mechanisms and behavioral demands shape the geometry of neural representations.

Looking at night vision

Lecture
Date:
Tuesday, March 1, 2022
Hour: 12:30
Location:
Prof. Shabtai Barash
|
Department of Brain Sciences, WIS

The architecture of the primate visual system is based on the fovea-fixation-saccade system for high-acuity vision. This talk will describe an analogous system in night vision of monkeys. Processing is based not on the fovea but on a ‘scotopic center’. Unlike the fovea, which is fixed in the retina, the scotopic center relocates over a ‘scotopic band’, according to the intensity of the ambient light and, more generally, perceptual uncertainty. The eye movements involved have sensorimotor transformations specific to night vision. The discussion will touch on the evolution of vision, including relevance for humans. Link: https://weizmann.zoom.us/j/95406893197?pwd=REt5L1g3SmprMUhrK3dpUDJVeHlrZz09 Meeting ID: 954 0689 3197 Password: 750421  

Effects of physical exercise and adult neurogenesis on hippocampal neural codes

Lecture
Date:
Thursday, February 10, 2022
Hour: 09:00 - 10:00
Location:
Yoav Rechavi - PhD Thesis Defense on Zoom
|
Prof. Yaniv Ziv, Lab Department of Brain Sciences

ABSTRACT Physical activity plays a vital role in maintaining a healthy brain, augmenting memory and cognition in both humans and animals. Previous studies have identified multiple distinct molecular and cellular factors that mediate these effects, both within the brain and systemically. However, what remains unknown is how exercise affects the neural coding mechanisms that underlie these cognitive and memory abilities. In my work I addressed this question in the context of spatial cognition, and studied how chronic voluntary exercise affects the quality and the long-term stability of hippocampal place codes. I performed longitudinal imaging of calcium activity in the hippocampal CA1 of mice as they repeatedly explored initially novel environments over weeks, and compared the place codes of mice that voluntarily ran on wheels in their home cage to those of sedentary mice. As previously reported, physical activity enhanced adult neurogenesis rates in the hippocampal dentate gyrus in the running group. I found that running increased the firing rates and the information content that place cells carry about position. In addition, I discovered a surprising relationship between physical activity and long-term neural-code stability: although running mice demonstrated an overall more stable place code than sedentary mice, their place code exhibited a higher degree of representational drift when controlling for code quality level. Using a simulated neural network, I found that the combination of both improved code quality and faster representational drift in runners, but neither of these effects alone, could recapitulate my experimental results. Overall, these results imply a role for physical activity in both improving the spatial code and accelerating representational drift in the hippocampus. Zoom link-https://weizmann.zoom.us/j/93585241611?pwd=RGsxakU2aElVQ01nbUpuRjVqOWQ0QT09 Meeting ID: 935 8524 1611 Password: 243908

Theory of neural perturbome

Lecture
Date:
Tuesday, February 1, 2022
Hour: 12:30
Location:
Prof. Claudia Clopath
|
Department of Bioengineering Imperial College London, UK

To unravel the functional properties of the brain, we need to untangle how neurons interact with each other and coordinate in large-scale recurrent networks. One way to address this question is to measure the functional influence of individual neurons on each other by perturbing them in vivo. Application of such single-neuron perturbations in mouse visual cortex has recently revealed feature- specific suppression between excitatory neurons, despite the presence of highly specific excitatory connectivity, which was deemed to underlie feature-specific amplification. Here, we studied which connectivity profiles are consistent with these seemingly contradictory observations, by modeling the effect of single-neuron perturbations in large-scale neuronal networks. Our numerical simulations and mathematical analysis revealed that, contrary to the prima facie assumption, neither inhibition dominance nor broad inhibition alone were sufficient to explain the experimental findings; instead, strong and functionally specific excitatory–inhibitory connectivity was necessary, consistent with recent findings in the primary visual cortex of rodents. Such networks had a higher capacity to encode and decode natural images, and this was accompanied by the emergence of response gain nonlinearities at the population level. Our study provides a general computational framework to investigate how single-neuron perturbations are linked to cortical connectivity and sensory coding and paves the road to map the perturbome of neuronal networks in future studies. Zoom Link: https://weizmann.zoom.us/j/95406893197?pwd=REt5L1g3SmprMUhrK3dpUDJVeHlrZz09 Meeting ID: 954 0689 3197 Password: 750421

To be announced

Lecture
Date:
Tuesday, January 25, 2022
Hour: 12:30
Location:
Gerhard M.J. Schmidt Lecture Hall
Alex Borst
|
Max Planck

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