Integrated Calendar

: A central question in neuroscience is how local processing and long-range influences work together to create behaviorally relevant neural dynamics. We address this issue by examining the song control pathway in the zebra finch. We find sufficient synaptic information is present in a key cortical structure to enable propagation of song-related sequences. We further demonstrate that long-range inputs from the motor thalamus can engage this circuitry in the service of behavior and large-scale brain synchronization. Our findings suggest that thalamic inputs may play an important initiating role for behaviorally-relevant cortical activity across species.

 
Energy materials are crystalline, solid-state substances with technological applications in energy-conversion or storage devices that include solar cells and batteries. In our work, we are particularly interested in scenarios where these systems show unusual structural dynamical effects. These effects trigger many puzzling questions in regard to updated structure-property relations and improved theoretical understandings of these solids. In my talk, I will present our recent findings regarding theoretical treatments of structural dynamics in energy materials and how we may use them to improve our understanding of their finite-temperature properties. The results will focus on halide perovskite as well as nitride semiconductors and solid-state ion conductors, which we typically investigate in tandem with experiment.

Femtosecond pump-probe experiments on nanocrystals are interpreted primarily in terms of state filling of the states involved in the intense band edge absorption features, and bi-exciton shifting which changes the resonance energy of the probe pulse due to presence of pump induced excitations. Results have been interpreted to show 1) that “hot” excitons will relax to the lowest available levels in the conduction band in ~1 ps, and 2) that said intense band edge exciton transition will be bleached linearly with excitons until the underlying states are completely filled. In the talk we describe a new approach involving “spectator excitons” to test these accepted views. It consists of comparing pump-probe experiments on pristine samples, with equivalent scans conducted on the same sample after it has been saturated in cold mono-excitons. We show how this method has uncovered previously unrecognized spin blockades in the relaxation of hot multi-exciton states in CdSe NCs, and simply detects stimulated emission signals even in presence of overlapping absorption. We report specific difficulties of applying this approach on perovskite crystals leading to controversial determination that in quantum confined CsPbBr3 bi-exciton interactions are positive (repulsive) and describe recent time resolved emission data which challenges this result.

The effect of the detailed connectivity of a neural circuit on its function and the resulting
behavior of the organism, is a key question in many neural systems Here, I study the circuit for
nociception in C elegans which is composed of the same neurons in the two sexes, that are wired
differently I set out to elucidate how the topological design of a compact neuronal circuit affects its
behavioral output, how genetic sex affects the connectivity and dynamics of a circuit, and how
specific circuit components orchestrate together to establish the behavioral sexual dimorphism I
used behavioral assays, optogenetics calcium and glutamate imaging, measurement of protein
expression, artificial connectivity, molecular and genetic tools, and show that the nociceptive sensory
neurons respond similarly in the two sexes, yet the animals display sexually dimorphic behaviors to
the same aversive stimuli To uncover the role of the downstream network topology in shaping
behavior, I measured the neuronal activity of a key interneuron, and found dimorphic responses to
the stimulus as well as dimorphic intrinsic basal interneuron activity I then showed that neuron
specific genetic sex plays a role in shaping connectivity and circuit dynamics, and proceed to an
artificial subtle synaptic rewiring which flips behavior between sexes Interestingly, when presented
with aversive cues, rewired males were compromised in finding mating partners, suggesting that
network topologies that enable efficient avoidance of noxious cues have a reproductive " My
results present a deconstruction of the design of a neural circuit that controls sexual behavior, and
how to reprogram it

We will discuss a generalization of the celebrated Minimax Theorem (von Neumann, 1928) for binary zero-sum games. A simple game which fails to satisfy Minimax is Ephraim Kishon's "Jewish Poker" (see [1,2] below). In this game, each player picks a number and the larger number wins. The payoff matrix in this game is *infinite triangular*. We show this is the only obstruction: if a game does not contain triangular submatrices of unbounded sizes then the Minimax Theorem holds. This generalizes von Neumann's Minimax Theorem by removing requirements of finiteness or compactness.

[1] http://www.ephraimkishon.de/en/my_favorite_stories.htm (english)
[2] https://gesherfilmfund.org.il/documents/מקבץ יצירות - אפרים … (hebrew, third story)

ydrogen transfer reactions play a prominent role in nature and many technological applications. Despite appearing to be simple reactions, they constitute complex processes where nuclear quantum effects (NQE) such as zero-point energy and nuclear tunneling play a decisive role even at ambient temperature. In this talk, I will show how state-of-the-art methodologies based on the path integral formulation of quantum mechanics in combination with the density functional approximation provide the unique possibility to theoretically address these effects in complex environments. The first part of the talk will focus on the porphycene molecule in the gas phase and adsorbed on metallic surfaces. The porphycene molecule constitutes a paradigmatic example of a molecular switch and has recently received great attention due to its intriguing hydrogen dynamics. I will demonstrate how a correct treatment of NQE, as well as the inclusion of multidimensional anharmonic couplings, are essential to obtain qualitatively correct results regarding the non-trivial temperature dependence of the hydrogen transfer rates and vibrational spectra [1-3]. Finally, I shall also mention some of our recent results for hydrogen diffusion on metals for which non-adiabatic effects, in addition to NQE, play a significant role and can lead to “quantum localization” [4-6].

[1] Y. Litman, J. O. Richardson, T. Kumagai, and M. Rossi, J. Am. Chem. Soc. 141, 2526 (2019)
[2] Y. Litman, J. Behler, and M. Rossi, Faraday Discuss. 221, 526 (2020)
[3] Y. Litman and M. Rossi, Phys. Rev. Lett. 125, 216001 (2020)
[4] Y. Litman, E. S. Pos. C. L. Box, R. Martinazzo, R. J. Maurer, and M. Rossi, J. Chem. Phys. 156, 194106 (2022)
[5] Y. Litman, E. S. Pos. C. L. Box, R. Martinazzo, R. J. Maurer, and M. Rossi , J. Chem. Phys. 156, 194107 (2022)
[6] O. Bridge, R. Martinazzo, S. C. Althorpe, Y. Litman, in preparation (2023)