לוח שנה משולב

"Sensory disconnection" – conditions when the same sensory stimulus does not reliably affect behavior or subjective experience - is a defining feature of sleep, and similar processes may occur during light anesthesia or during cognitive lapses in wakefulness. What are the changes in brain activity that mediate sensory disconnection? In a series of studies in humans and rodents, we investigate how "disconnected" states affect sensory processing. The first set of studies reveals differences in neuronal responses to identical sensory stimuli across states. We find that in humans, cognitive lapses after sleep deprivation involve attenuated and delayed single-neuron responses in MTL co-occurring with local slow/theta waves. In the auditory domain, we show in both rodents and humans that responses in sleep and light anesthesia are preserved up to A1, challenging the classic "thalamic gating" notion, but robust attenuation occurs later in high-level cortical regions. In addition, sleep affects more strongly responses that require integration over long time intervals, and responses to high-frequency content. The second set of studies investigates the underlying mechanisms, testing the potential role of locus coeruleus-noradrenaline (LC-NE) neuromodulation. In rats, we test how NE signaling affects the probability to wake up from sleep in response to sounds. We establish a new approach for selective in-vivo LC optogenetics by showing effects on spiking activity, evoked sleep-wake transitions, and pupil dilation. Combined LC and auditory stimulation synergistically increases the probability of awakenings beyond independent effects of sound and laser alone, supporting a role for LC-NE activity in mediating sensory responses. We also tested the effects of NE levels on sensory perception and sensory-evoked activity (EEG, fMRI) in awake humans. Pharmacologically manipulating NE levels in double-blind placebo-controlled experiments, we found that NE modulates sensitivity and accuracy of visual perception without significant effects on decision bias (criterion). In addition, NE increased the fidelity of late EEG visual responses, and selectively modulated BOLD fMRI responses in high-order visual cortex, suggesting that NE plays an enabling causal role in visual awareness by affecting late visual processing.

When an ultra-short pulse of radiation is scattered on a complex medium, the emerging radiation pulse is broadened in time. This can be intuitively explained as due to the existence of a large number of paths of varying lengths through which the radiation can traverse the scattering medium. Recently, novel methods to produce ultra-short light pulses were introduced, and they opened a new horizon for experiments were the distribution of delay-times induced by scattering from complex targets can be measured. These developments emphasize the need for theoretical tools to aid planning of new experiments and interpret the measured results. I shall review a general approach for studying the delay-time distribution in both the classical and the quantum (wave) dynamical frameworks. In particular, I shall discuss the delay time distribution in scattering from a random medium where, due to Anderson Localization, there is no classical analogue to this genuine wave phenomenon.

TBA

Fingerprints of the three-dimensional organization of genomes have emerged using recent advances, but genome dynamics is poorly understood. Here, we create the Chromosome Copolymer Model (CCM) by representing chromosomes as a copolymer with two epigenetic loci types corresponding to euchromatin and heterochromatin. We establish quantitatively that the chromosomes 5 and 10 topology from our model and from experiment are in good agreement. Chromatin exhibits glassy dynamics with coherent motion on micron scale. The broad distribution of the diffusion exponents, which quantitatively agrees with experiments, is suggestive of highly heterogeneous dynamics, reflected in the cell- to-cell variations in the contact maps. Chromosome organization is hierarchical, involving the formation of chromosome droplets, followed by coalescence, reminiscent of Ostwald ripening.

In my PhD I led three projects probing human behavioral and physiological responses to olfactory stimuli in health and disease. In these projects I used every-day olfactory occurrences in order to infer on biological underpinnings of human behavior.
In my main project I tested olfactory processing in autism, using the sniff response, a ten-minute non-verbal measure of respiratory response to odors. I found this objective measure to be profoundly altered in children with autism, and furthermore, to be highly correlated with autism severity. Using computational methods, I demonstrated 81% correct ASD classification based on differences in olfactory processing alone. These results provide proof-of-concept for a potential biomarker for autism (Rozenkrantz et al, Curr Bio, 2015).
In a second and soon-to-be-submitted project, I investigated olfactory social communication in recurrent pregnancy loss (RPL), resting on a phenomenon in rodents in which females miscarry following exposure to bodily odors of non-stud males. I found that women with RPL display heightened social olfactory abilities, which were significantly correlated with number of miscarriages. Additionally, women with RPL showed significantly altered hormonal, physiological and neural responses to body odors of unfamiliar men. This project provides novel evidence for altered olfactory processing in human recurrent miscarriages.
The third project is also my first foothold in placebo effect research, which I will pursue in my postdoc. Taking advantage of the non-invasive nature of olfactory stimuli, I used an odor as the placebo carrier, and tested two groups of subjects for different creativity tests. Both groups smelled the odor, but only the placebo group was told that it increases creativity (placebo manipulation). I found that following this simple manipulation, the placebo group displayed significantly enhanced creativity (Rozenkrantz et al., PLoS one, 2017).
Taken together, these projects convey my deep interest in the interplay between human behavior and physiology.