A combined experimental and computational approach to investigate emergent network dynamics based on large-scale neuronal recordings

Sviluppo di un approccio integrato computazionale-sperimentale per lo studio di reti neuronali mediante registrazioni elettrofisiologich

Processing of signals in the peripheral auditory system in relation to aural perception

Imperial Users onl

Genetically encoded molecular probes for analyzing neural circuits

Precise electrochemical signaling is essential for neural network computation. Over the past century, we have learned much about the links between behavior and the activity patterns of specific neurons. The development of optogenetic tools to control and monitor specific neurons in the living brain has enabled the causal analysis of neuron populations with unique genetic identity in brain computation. In this thesis, we developed a novel genetically encoded voltage indicator (GEVI), SomArchon, for optical voltage recording in behaving mice, and assembled a viral toolbox of genetically encoded synaptic tags. Overall, these novel genetically encoded tools will facilitate the study of synaptic wiring and neural activity in a wide variety of neuroscience applications. Optical voltage imaging enables the monitoring of neural activity with millisecond temporal precision and cellular resolution. However, current state-of-the-art GEVIs only report spiking activity in 1-2 cells simultaneously in vivo. We developed a soma-localized GEVI, SomArchon, compatible with optogenetic control and capable of reporting subthreshold and spiking activity in populations of individual neurons in awake mice. We found that highly coherent subthreshold activity does not govern highly coherent spike outputs in neighboring neurons. Overall, SomArchon outperforms existing sensors and enables in vivo population voltage imaging suitable for a diversity of neuroscience experiments. Synaptic labeling is important in understanding the wiring of neural circuits or the synaptic changes involved in development, plasticity, and disease. Fibronectin intrabodies generated with mRNA display (FingRs) are genetically encoded fluorescent synaptic labels that do not alter synaptic transmission. Here, we generated a set of adeno-associated virus (AAV) FingR variants for labeling of excitatory or inhibitory synapses in multiple brain regions, and in specific cell types in cre-transgenic mice. We optimized a red synaptic tag for inhibitory synapses that allowed for dual labeling of both excitatory and inhibitory synapses in the same cells. Finally, we generated FingR retroviruses and tracked synaptic development of adult born hippocampal granule cells. These AAV and retrovirus variants label excitatory or inhibitory synapses in specific cell types and provide a comprehensive viral toolbox for multi-color, cell type specific synaptic labelling for studying synaptic architecture, synapse development, and synaptic plasticity.2021-06-04T00:00:00

Regulation of spike timing in visual cortical circuits

A train of action potentials (a spike train) can carry information in both the average firing rate and the pattern of spikes in the train. But can such a spike-pattern code be supported by cortical circuits? Neurons in vitro produce a spike pattern in response to the injection of a fluctuating current. However, cortical neurons in vivo are modulated by local oscillatory neuronal activity and by top-down inputs. In a cortical circuit, precise spike patterns thus reflect the interaction between internally generated activity and sensory information encoded by input spike trains. We review the evidence for precise and reliable spike timing in the cortex and discuss its computational role

Regulation of spike timing in visual cortical circuits

A train of action potentials (a spike train) can carry information in both the average firing rate and the pattern of spikes in the train. But can such a spike-pattern code be supported by cortical circuits? Neurons in vitro produce a spike pattern in response to the injection of a fluctuating current. However, cortical neurons in vivo are modulated by local oscillatory neuronal activity and by top-down inputs. In a cortical circuit, precise spike patterns thus reflect the interaction between internally generated activity and sensory information encoded by input spike trains. We review the evidence for precise and reliable spike timing in the cortex and discuss its computational role

The characteristics and the implications of electrical activity within the nervous system

Abstract Not Provided

Touching is believing: creating illusions and feeling of embodiment with mid-air haptic technology

Over the last two decades, the sense of touch has received new attention from the scientific community.Several haptic devices have been developed to address the complexity of the sense of touch, the latest addition being mid-air (contactless) haptic technology. An interesting series of previous research has suggested an easier way to tackle the complexity of designing convincing tactile sensations by exploiting tactile illusions. Tactile illusions rely on perceptual shortcuts based on the psychophysics of the tactile receptors. Currently, studies exploring the perceptual space of mid-air haptics and its applicability in the tactile illusions field are still limited in number. This thesis aims to contribute to the field of Human-Computer Interaction (HCI) by investigating the perceptual design space of ultrasonic mid-air haptics technology. Specifically, in a first set of three studies, we investigate the absolute thresholds (minimal amount of a property of astimulus that a user can detect) for control points (CP) at different frequencies on the hand and arm (Study 1). Then we investigate the optimal sampling rate needed to drive the device in an optimal fashion and its relationship with shape size (Study 2). Next, we apply a new technique to increase users’ performance in a shape discrimination task (Study 3). In Study 4, we start the exploration of a tactile illusion of movement using contact touch and later, we apply a similar procedure to investigate the feasibility of creating a tactile illusion of movement between the two non-interconnected hands by using mid-air touch (Study 5). Finally, in Study 6, we explore our sense of touch in VR, while providing an illusion of rain drops through mid-air haptics, to recreate a virtual hand illusion (VHI) to explore the boundaries of our sense of embodiment. Therefore, the contribution of this work is threefold: a) we contribute by adding new knowledge on the psychophysical space for mid-air haptics, b) we test the potential to create realistic tactile sensations by exploiting tactile illusions with mid-air haptic technology, and c) we demonstrate how tactile illusions mediated by mid-air haptics can convey a sense of embodiment in VR environments

Lexicosemantic processing in normal and pathological aging

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal