Reading the Neural Code: What do Spikes Mean for Behavior?

The present study reveals the existence of an intrinsic spatial code within neuronal spikes that predicts behavior. As rats learnt a T-maze procedural task, simultaneous changes in temporal occurrence of spikes and spike directivity are evidenced in “expert” neurons. While the number of spikes between the tone delivery and the beginning of turn phase reduced with learning, the generated spikes between these two events acquired behavioral meaning that is of highest value for action selection. Spike directivity is thus a hidden feature that reveals the semantics of each spike and in the current experiment, predicts the correct turn that the animal would subsequently make to obtain reward. Semantic representation of behavior can then be revealed as modulations in spike directivity during the time. This predictability of observed behavior based on subtle changes in spike directivity represents an important step towards reading and understanding the underlying neural code

The First Detection of Gravitational Waves

This article deals with the first detection of gravitational waves by the advanced Laser Interferometer Gravitational Wave Observatory (LIGO) detectors on 14 September 2015, where the signal was generated by two stellar mass black holes with masses 36 $M_{\odot}$ and 29 $M_{\odot}$ that merged to form a 62 $M_{\odot}$ black hole, releasing 3 $M_{\odot}$ energy in gravitational waves, almost 1.3 billion years ago. We begin by providing a brief overview of gravitational waves, their sources and the gravitational wave detectors. We then describe in detail the first detection of gravitational waves from a binary black hole merger. We then comment on the electromagnetic follow up of the detection event with various telescopes. Finally, we conclude with the discussion on the tests of gravity and fundamental physics with the first gravitational wave detection event.Comment: 20 pages, 9 figures, Published in a special issue of Universe "Varying Constants and Fundamental Cosmology

Non-equilibrium breakdown of quantum Hall state in graphene

In this report we experimentally probe the non-equilibrium breakdown of the quantum Hall state in monolayer graphene by injecting a high current density ($\sim$1A/m). The measured critical currents for dissipationless transport in the vicinity of integer filling factors show a dependence on filling factor. The breakdown can be understood in terms of inter Landau level (LL) scattering resulting from mixing of wavefunctions of different LLs. To further study the effect of transverse electric field, we measured the transverse resistance between the $\nu=2$ to $\nu=6$ plateau transition for different bias currents and observed an invariant point.Comment: to appear in PRB Rapi