Integrated Calendar

Cognitive function and emotional homeostasis, and the aspiration to decipher their neuronal basis have stood at the heart of neuroscience since its inception. The complexity of the circuits underlying these processes is immense, and new techniques are necessary to provide novel efficient ways to make a significant progress in brain research. Optogenetic tools enable temporally and spatially precise in-vivo activation or inactivation of genetically defined cell populations, thus enabling deconstruction of systems that were not available for research. An example for that is my work re-examining the role of the hippocampus in remote memory. The prevailing theory suggests that the process of remote memory consolidation requires early involvement of the hippocampus, followed by the neocortex. In the course of this process, an influence of hippocampus on neocortex may enable the hippocampus to facilitate the remote cortical storage of memory, rather than stably store the memory itself. Indeed, contextual fear memories in rodents are completely unaffected by hippocampal lesions or pharmacological inhibition on the remote timescale of weeks after training, but do depend on the hippocampus over the recent timescale of days after training. However, in exploring the contribution of defined cell types to remote memory using optogenetic methods (which are orders of magnitude faster in onset and offset than earlier methods), we found that even weeks after contextual conditioning, the contextual fear memory recall could be abolished by optogenetic inhibition of excitatory neurons in the CA1 region of the hippocampus- at times when all earlier studies had found no detectable influence of hippocampus. We also optogenetically confirmed the remote-timescale importance of anterior cingulate cortex. In exploring mechanisms, we found that loss of hippocampal involvement at remote timepoints depended on the timescale of hippocampal inhibition, since 1) we replicated earlier pharmacological work using longer-lasting drug-mediated inhibition of hippocampus (revealing the recent, but not remote, effects on memory); and 2) extending optogenetic inhibition of hippocampus to match typical pharmacological timescales converted the remote hippocampus-dependence to remote hippocampus-independence. These findings uncover a remarkable dynamism in the mammalian memory retrieval process, in which underlying neural circuitry adaptively shifts the default structures involved in memory—normally depending upon the hippocampus even at remote timepoints, but flexibly moving to alternate mechanisms when the hippocampus is offline on the timescale of minutes. This new model is further supported by the finding that contextual memory was instantaneously suppressed by CA1 inhibition even in the midst of a single freely-moving behavioral session, after the memory was already retrieved. Our findings have broad implications for the interpretation of drug or lesion data in other systems, and may open an exciting therapeutic avenue for PTSD patients, in which a pathology-inducing contextual memory could be stopped as it appears without permanently affecting other memories.

In recent years topological insulators have been in the center of attention of many in the condensed matter community. The initial theoretical prediction of a topological insulator (Kane and Mele '05) was done in the context of graphene and was inspired by the Haldane model of Landau levels without magnetic field in the honeycomb lattice. Experimentally, the notion that a non-trivial Chern number may arise from band structure which was demonstrated in graphene has led to the discovery of topological insulators in systems with band inversion. Nevertheless, a graphene based topological insulator has not yet been realized. In this talk I will discuss ways in which graphene heterostructures can be engineered to give a variety of phases, including a topological insulator.

Prior to large clinical trial studies where data is collected from multiple scanners, across scanner validation should be performed to ensure that the data from multiple scanners can be pooled for statistical analysis. This talk with present high-resolution magnetic resonance imaging (hrMRI) in vivo of the distal radius from multiple scanners, analysis of bone micro-architecture (BMA) parameters from these images, and analysis of the reproducibility for both the subjects scanned repeatedly at the same scanner and the same subjects scanned on multiple scanners. The reproducibility scans were acquired on General Electric (Waukesha, WI, USA) Signa™ 1.5T scanners at nine MRI centers, and the analysis results show that the hrMRI method for BMA parameter measurement is consistent across multiple scanners. Methods and data will also be shown for microscopic phantom studies that can be used to monitor scanner performance over time, and clinical investigation studies showing the utility of the BMA parameters in reflecting bone quality

Many different physical realizations of quantum bits have been studied over the past decade, including trapped ions, nuclear spins of molecules in solution, Josephson junctions and more. Among the different possible realizations, solid-state implementations have attracted considerable interest due to their promise in miniaturization and scaling, taking advantage of existing technology for fabrication. The spin qubit is one such example where a quantum bit of information is encoded in the spin state of a single electron confined to a small spatial dimension.
In this talk I will discuss some of our recent work on single electron spin qubits in GaAs quantum dots and color centers in diamond. In these systems spin decoherence arises predominantly from the interaction with proximal paramagnetic spins such as nuclear spins of the host lattice. However, the slow dynamics of this environment lends itself to effective decoupling schemes that allow extending coherence to nearly a millisecond. Paradoxically, coupling to the seemingly random environment of nuclear spins provides valuable resources for storage, single shot readout and fast manipulation of quantum information with important applications to quantum information processing and metrology.