Stimulus modality

Résumé

Stimulus modality, also called sensory modality, is one aspect of a stimulus or what is perceived after a stimulus. For example, the temperature modality is registered after heat or cold stimulate a receptor. Some sensory modalities include: light, sound, temperature, taste, pressure, and smell. The type and location of the sensory receptor activated by the stimulus plays the primary role in coding the sensation. All sensory modalities work together to heighten stimuli sensation when necessary. Multimodal perception is the ability of the mammalian nervous system to combine all of the different inputs of the sensory nervous system to result in an enhanced detection or identification of a particular stimulus. Combinations of all sensory modalities are done in cases where a single sensory modality results in an ambiguous and incomplete result. Integration of all sensory modalities occurs when multimodal neurons receive sensory information which overlaps with different modalities. Multimodal neurons are found in the superior colliculus; they respond to the versatility of various sensory inputs. The multimodal neurons lead to change of behavior and assist in analyzing behavior responses to certain stimulus. Information from two or more senses is encountered. Multimodal perception is not limited to one area of the brain: many brain regions are activated when sensory information is perceived from the environment. In fact, the hypothesis of having a centralized multisensory region is receiving continually more speculation, as several regions previously uninvestigated are now considered multimodal. The reasons behind this are currently being investigated by several research groups, but it is now understood to approach these issues from a decentralized theoretical perspective. Moreover, several labs using invertebrate model organisms will provide invaluable information to the community as these are more easily studied and are considered to have decentralized nervous systems. Lip reading is a multimodal process for humans.

Source officielle

https://en.wikipedia.org/wiki/Stimulus_modality

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Thalamic microcircuitry: neurons, synapses, and circuit motifs in receptive field structure and sensory processing

Jane Yi

Our perception of the world is first shaped by the thalamus, a structure composed of many nuclei in the center of our brains. Different nuclei hold different responsibilities - vision (dorsal lateral genicular nucleus; dLGN), audition (medial geniculate nucleus; MGN), somatosensation (ventro-basal nuclei; VB), though many properties across these sensory modalities appear to be universal. In this thesis, we completed a comprehensive characterization of the neurons, connections, and microcircuitries within the rodent VB thalamus. Our most prominent finding is the confirmation of the existence of local interneurons in the VB and the discovery of their profoundly active and diverse role in thalamic processes. Thus, we have observed that the fundamental excitatory and inhibitory neurons of dLGN and VB nuclei and their intrinsic circuit motifs are indistinguishable. Only a few notable differences are, however, present. (1), Principal excitatory neurons of the VB, the thalamocortical (TC) relays, have morphological types that appear to be distributed heteroge-neously throughout the VB whereas dLGN TC morphological types have regional preferences. (2), VB inhibitory local interneurons represent a smaller proportion of the total neuronal popula-tion compared to their dLGN counterparts. The similarities between these thalamic regions great-ly outnumber the differences. It then introduces new questions of how different vision and soma-tosensation of the physical world are when these senses are ultimately represented as binary sig-nals and are processed in similar manners in the thalamus. Following these questions may lead to new therapeutic solutions for retinally blind patients, tactile prostheses, or neurological disorders of sensory perception like schizophrenia.

EPFL2021

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Background: Exoskeletons for lower and upper extremities have been introduced in neurorehabilitation because they can guide the patient's limb following its anatomy, covering many degrees of freedom and most of its natural workspace, and allowing the control of the articular joints. The aims of this study were to evaluate the possible use of a novel exoskeleton, the Arm Light Exoskeleton (ALEx), for robot-aided neurorehabilitation and to investigate the effects of some rehabilitative strategies adopted in robot-assisted training. Methods: We studied movement execution and muscle activities of 16 upper limb muscles in six healthy subjects, focusing on end-effector and joint kinematics, muscle synergies, and spinal maps. The subjects performed three dimensional point-to-point reaching movements, without and with the exoskeleton in different assistive modalities and control strategies. Results: The results showed that ALEx supported the upper limb in all modalities and control strategies: it reduced the muscular activity of the shoulder's abductors and it increased the activity of the elbow flexors. The different assistive modalities favored kinematics and muscle coordination similar to natural movements, but the muscle activity during the movements assisted by the exoskeleton was reduced with respect to the movements actively performed by the subjects. Moreover, natural trajectories recorded from the movements actively performed by the subjects seemed to promote an activity of muscles and spinal circuitries more similar to the natural one. Conclusions: The preliminary analysis on healthy subjects supported the use of ALEx for post-stroke upper limb robotic assisted rehabilitation, and it provided clues on the effects of different rehabilitative strategies on movement and muscle coordination.

Biomed Central Ltd2016

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Extensive mapping of neuronal connections in the central nervous system requires high-throughput mm-scale imaging of large volumes. In recent years, different approaches have been developed to overcome the limitations due to tissue light scattering. These methods are generally developed to improve the performance of a specific imaging modality, thus limiting comprehensive neuroanatomical exploration by multi-modal optical techniques. Here, we introduce a versatile brain clearing agent (2,2'-thiodiethanol; TDE) suitable for various applications and imaging techniques. TDE is cost-efficient, water-soluble and low-viscous and, more importantly, it preserves fluorescence, is compatible with immunostaining and does not cause deformations at sub-cellular level. We demonstrate the effectiveness of this method in different applications: in fixed samples by imaging a whole mouse hippocampus with serial two-photon tomography; in combination with CLARITY by reconstructing an entire mouse brain with light sheet microscopy and in translational research by imaging immunostained human dysplastic brain tissue.

Nature Publishing Group2015