Biology subjects

Masse, I. O.

Publications and source records attributed to Masse, I. O..

2 recordsLinked to original sources

bioRxiv2019

Afferent connections of the primary somatosensory cortex of the mouse for contextual and multisensory processing

Sensory information is conveyed from peripheral receptors through specific thalamic relays to primary areas of the cerebral cortex. Information is then routed to specialized areas for the treatment of specific aspects of the sensory signals and to multisensory associative areas. Information processing in primary sensory cortices is influenced by contextual information from top-down projections of multiple cortical motor and associative areas as well as areas of other sensory modalities and higher order thalamic nuclei. The primary sensory cortices are thus located at the interface of the ascending and descending pathways. The theory of predictive coding implies that the primary areas are the site of comparison between the sensory information expected as a function of the context and the sensory information that comes from the environment. To better understand the anatomical basis of this model of sensory systems we have charted the cortical and subcortical afferent inputs in the ipsilateral and contralateral hemispheres of the primary somatosensory cortex of adult C57Bl/6 mice. Iontophoretic injections of the b-fragment of cholera toxin were performed inside the mystacial caudal barrel field, more rostral barrel field and somatosensory cortex outside the barrel field to test the hypothesis that differences exist between these three parts and to compare their projections to the subnetworks built from the Mouse Connectome Project data. The laminar distribution of retrogradely labeled cell bodies was used to classify the projections as feedback, feedforward or lateral. Layer indices range between -1 and 1, indicating feedback and feedforward connections respectively. The primary somatosensory cortex and the barrel field have afferent connections with somatosensory areas, non-somatosensory primary sensory areas, multisensory, motor, associative, and neuromodulatory areas. The caudal part of the barrel field displays different and more abundant cortical and subcortical connections compared to the rest of the primary somatosensory cortex. Layer indices of cortical projections to the primary somatosensory cortex and the barrel field were mainly negative and very similar for ipsilateral and contralateral projections. These data demonstrate that the primary somatosensory cortex receives sensory and non-sensory information from cortical and subcortical sources.

neuroscience↗

bioRxiv2018

In vivo cerebral microdialysis validation of the acute central glutamate response in a translational rat model of concussion combining force and rotation

Concussions/mild traumatic brain injury (mTBI) represent a major public health concern due to persistent behavioral and neurological effects. The mechanisms by which concussions lead to such effects are partly attributable to an hyperacute indiscriminate glutamate release. Cerebral microdialysis studies in rodents reported a peak of extracellular glutamate 10 minutes after injury. Microdialysis has the advantage of being one of the few techniques allowing the quantification of neurotransmitters in vivo and at different time points following injury. In addition to the clear advantages afforded by microdialysis, the Wayne State weight-drop model induces an impact on the skull of a subject unrestrained by the fall of a weight. The latter model allows rapid acceleration and deceleration of the head and torso, an essential feature in human craniocerebral trauma and a factor that is missing from many existing animal concussion models. In the present study, we applied the Wayne State procedure and microdialysis to document, in awake rats, the acute changes in extracellular hippocampal glutamate and GABA levels resulting from concussive trauma. We studied the dorsal CA1 hippocampal region as it contains a high density of glutamatergic terminal and receptors, thus making it vulnerable to excitotoxic insult. Using HPLC, dialysate levels of hippocampal glutamate and GABA were measured in adult male Sprague-Dawley rats in 10 min increments for 60 min prior to, during and for 90 min following concussive trauma induced by the Wayne State weight-drop procedure. Sham control animals were treated in the same manner but without receiving the concussive trauma procedure. Our results show that concussive trauma is followed, within 10 min, by a robust, transient 3-fold increase in hippocampal glutamate levels; such changes were not seen in controls. In contrast, GABA levels were unaffected by the concussive trauma procedure. The findings derived from the approach used here are generally consistent with those of previous other studies. They also provide a crucial in vivo validation of the Wayne State procedure as a model with promising translational potential for pre-clinical studies on early therapeutic responses to concussion.

neuroscience↗