The Edmond and Lily Safra Center for Brain Sciences at The Hebrew University of Jerusalem
invites you to the symposium:
Advances in Brain Sciences 2018:
Glimpses of the Future
09:00 – 10:00
Combined voltage imaging and optogenetic stimulation reveals brain-state dependent changes in hippocampal subthreshold dynamics and excitability
A technology to record membrane potential from multiple neurons, simultaneously, in behaving animals will have a transformative impact on neuroscience research. Parallel recordings could reveal the subthreshold potentials and intercellular correlations that underlie network behavior. Paired stimulation and recording could further reveal the input-output properties of individual cells or networks in the context of different brain states. Genetically encoded voltage indicators are a promising tool for these purposes, but were so far limited to single-cell recordings with marginal signal to noise ratio (SNR) in vivo. We developed improved near infrared voltage indicators, high speed microscopes and targeted gene expression schemes which enabled recordings of supra- and subthreshold voltage dynamics from multiple neurons simultaneously in mouse hippocampus, in vivo. The reporters revealed sub-cellular details of back-propagating action potentials and correlations in sub-threshold voltage between multiple cells. In combination with optogenetic stimulation, the reporters revealed brain state-dependent changes in neuronal excitability, reflecting the interplay of excitatory and inhibitory synaptic inputs. These tools open the possibility for detailed explorations of network dynamics in the context of behavior.
10:00 – 11:00
Investigations into the functional architecture of the human brain; lessons from neurofeedback
National Institutes of Science
Behavior is dependent on the configuration and activity of many different networks. Examining spontaneous activity allows us to characterize these networks, and the relationships between them. Moreover, the patterns of spontaneous activity, and the correlations between different brain regions, are predictive of individual differences, both within the normal range of task performance, and in the severity of clinical symptoms. I will provide a framework for probing the relationship between network configurations and behavior in a more causal manner, through the use of covert neurofeedback. This technique allows us to perturb brain networks by reinforcing desired network states directly, through a reward orthogonal to the networks being trained. This allows us to directly alter a feature of interest in the brain, such as the correlation between different brain regions, and then assess changes in behavior, rather than training behavior, and then searching for changes in networks. I will describe three studies: the first showing that covert neurofeedback can be entirely implicit, and works even without learning intent on the part of participants; the second that it is possible to change targeted aberrant connections, even in a patient population; and the third, moving on to more circumscribed networks and behavior, to best test how changes in networks bring about changes in behavior.
11:15 – 12:15
Sleep and memory consolidation: the importance of long-term sleep patterns and how sleep contributes to insight
Accumulating evidence from the last two decades suggests that sleep facilitates memory consolidation. The mechanisms underlying this effect, however, are anything but clear. Two questions in the field have often received little attention: (1) Are the effects of sleep mostly state- or trait-dependent? and (2) how does sleep facilitates higher-cognitive functions, such as the gain of insight? In my talk, I will present a series of studies addressing these questions. In the first line of studies, I make the case that regular baseline levels of sleep measured over multiple nights – particularly Slow-Wave Sleep (SWS) and Rapid-Eye Movement (REM) sleep – are more influential on cognitive and emotional processing than any single night of sleep. Importantly, I demonstrate that individual variability in the baseline amounts of REM and SWS can predict subsequent brain activation during fear learning in humans, a result that might imply a trait-dependent predisposition to Post-Traumatic-Stress-Disorder. In the second line of studies, I present a novel “temporal scaffolding” hypothesis regarding the way sleep may inspire insight learning. I claim that existing experimental results show sleep supports insight mainly when it involves the discovery of temporal rules, and that this phenomenon can be explained by the time-compressed reactivation of memories (“memory replay”) occurring in the hippocampus during SWS. I then present computational and experimental evidence to support these claims.
12:15 – 13:15
Mesoscale dissection of neuronal populations underlying complex behaviors
University of Zurich
One of the fundamental functions of the brain is to integrate incoming sensory stimuli, perceive and associate these integrations with internal representations, and make fast and reliable decisions and actions. Although these processes have been extensively studied, we are still missing a comprehensive understanding of the exact spatiotemporal dynamics at a mesoscale level, i.e. at the neuronal population level spanning many cortical and sub-cortical areas. In my opinion, the key to understanding these processes is to measure from large populations of neurons within a single trial as a subject performs a complex behavior. In my talk, I will present a variety of evidence from primates and mice backing up this claim and shortly discuss my future plans. In one of the projects, we imaged calcium signals from the whole dorsal cortex of mice performing a whisker-based texture discrimination task with a short-term memory component. Mice use different behavioral strategies to solve the task either deploying an active strategy — engaging their body and whiskers towards the approaching texture — or passively awaited the touch. Based on this strategy, short-term memory was located in frontal secondary motor cortex (M2) in active mice whereas in a newly identified posterior area (P) in passive mice. Optogenetic perturbation of these areas impaired performance specifically in the associated strategy. In some cases, mice overcame the perturbation by switching to the alternative strategy. Thus, depending on behavioral strategy within single trials, cortical population activity is routed differentially to hold information either frontally or posteriorly before converging to similar action. Additional projects, using different tasks, neuronal subtypes and during learning highlight the importance of observing and dissecting mesoscale dynamics during complex behaviors.
14:00 – 15:00
Social-spatial neuronal representations: from bats to primates
Weizmann Institute, the Neurobiology Department
Social animals have to know the spatial positions of conspecifics. However, it is unknown how the position of others is represented in the brain. In my talk I’m going to present my recent study on “Social place-cells” – cells in the dorsal hippocampus of freely flying bats which represent the position of other conspecifics. To reveal these social-spatial representations I designed a spatial observational-learning task, in which an observer bat mimicked a demonstrator bat while I recorded the activity of hippocampal dorsal-CA1 neurons from the observer bat. A neuronal subpopulation represented the position of the other bat, in all centric coordinates. About half of these “social place cells” represented also the observer’s own position—that is, were place cells. The representation of the demonstrator bat did not reflect self-movement or trajectory planning by the observer. Some neurons represented also the position of inanimate moving objects; however, their representation differed from the representation of the demonstrator bat. This suggests a role for hippocampal CA1 neurons in social-spatial cognition.