fR Gravity Effects on Charged Accelerating AdS Black Holes Using Holographic Tools

We investigate numerically fR gravity effects on certain AdS/CFT tools including holographic entanglement entropy and two-point correlation functions for a charged single accelerated Anti-de Sitter black hole in four dimensions. We find that both holographic entanglement entropy and two-point correlation functions decrease by increasing the acceleration parameter A, matching perfectly with literature. Taking into account the fR gravity parameter η, the decreasing scheme of the holographic quantities persist. However, we observe a transition-like point where the behavior of the holographic tools changes. Two regions meeting at such a transit-like point are shown up. In such a nomination, the first one is associated with slow accelerating black holes while the second one corresponds to a fast accelerating solution. In the first region, the holographic entanglement entropy and two-point correlation functions decrease by increasing the η parameter. However, the behavioral situation is reversed in the second one. Moreover, a cross-comparison between the entropy and the holographic entanglement entropy is presented, providing another counterexample showing that such two quantities do not exhibit similar behaviors.

Hippocampal theta, gamma, and theta-gamma coupling: effects of aging, environmental change, and cholinergic activation

Hippocampal theta and gamma oscillations coordinate the timing of multiple inputs to hippocampal neurons and have been linked to information processing and the dynamics of encoding and retrieval. One major influence on hippocampal rhythmicity is from cholinergic afferents. In both humans and rodents, aging is linked to impairments in hippocampus-dependent function along with degradation of cholinergic function. Cholinomimetics can reverse some age-related memory impairments and modulate oscillations in the hippocampus. Therefore, one would expect corresponding changes in these oscillations and possible rescue with the cholinomimetic physostigmine. Hippocampal activity was recorded while animals explored a familiar or a novel maze configuration. Reexposure to a familiar situation resulted in minimal aging effects or changes in theta or gamma oscillations. In contrast, exploration of a novel maze configuration increased theta power; this was greater in adult than old animals, although the deficit was reversed with physostigmine. In contrast to the theta results, the effects of novelty, age, and/or physostigmine on gamma were relatively weak. Unrelated to the behavioral situation were an age-related decrease in the degree of theta-gamma coupling and the fact that physostigmine lowered the frequency of theta in both adult and old animals. The results indicate that age-related changes in gamma and theta modulation of gamma, while reflecting aging changes in hippocampal circuitry, seem less related to aging changes in information processing. In contrast, the data support a role for theta and the cholinergic system in encoding and that hippocampal aging is related to impaired encoding of new information.

On the performance of biological movement detectors and ideal velocity sensors in the context of optomotor course stabilization

It is often assumed that the ultimate goal of a motion-detection system is to faithfully represent the time-dependent velocity of a moving stimulus. This assumption, however, may be an arbitrary standard since the requirements for a motion-detection system depend on the task that is to be solved. In the context of optomotor course stabilization, the performance of a motion-sensitive neuron in the fly's optomotor pathway and of a hypothetical velocity sensor are compared for stimuli as are characteristic of a normal behavioral situation in which the actions and reactions of the animal directly affect its visual input. On average, tethered flies flying in a flight simulator are able to compensate to a large extent the retinal image displacements as are induced by an external disturbance of their flight course. The retinal image motion experienced by the fly under these behavioral closed-loop conditions was replayed in subsequent electrophysiological experiments to the animal while the activity of an identified neuron in the motion pathway was recorded. The velocity fluctuations as well as the corresponding neuronal signals were analyzed with a statistical approach taken from signal-detection theory. An observer scrutinizing either signal performs almost equally well in detecting the external disturbance.