Somatosensory neurons densely innervate skin, our largest sensory organ. Adult skin continually remodels throughout the lifespan to maintain a protective barrier for our bodies. How sensory neurons maintain their peripheral endings in the face of continual turnover of their target tissue is not well understood. To address this gap in knowledge, I analyzed the temporal dynamics and mechanisms of structural plasticity of touch receptors in healthy adult skin. My studies focused on the terminals of Merkel-cell afferents in mouse touch domes. These two-part touch receptors comprise epithelial Merkel cells innervated by branching axons of fast-conducting sensory neurons. I show that Merkel cells and their afferents are structurally plastic over the course of hair growth in adults. These two components simplify during active hair growth, with fewer terminal neurites and fewer Merkel cells per touch dome at this stage compared with other phases of hair growth. Merkel-cell removal was observed with multiple molecular markers. Additionally, mice showed diminished touch-evoked behavior during hair growth compared with follicle quiescence. Next, I showed that Sarm1, a key effector of Wallerian degeneration, is not required for structural plasticity of Merkel cell-neurite complexes in young adulthood. Finally, I developed a technique to perform time-lapse in vivo imaging of identified Merkel cells and afferent terminals over the course of a month. These structures were highly plastic, with afferent terminals undergoing frequent growth and regression, as well as both Merkel cells and terminal branches being added or removed. Together, these studies reveal that peripheral nerve terminals undergo a previously unsuspected amount of structural plasticity in healthy tissue.

Dendritic spines are the major sites for receiving excitatory synaptic inputs and play important roles in neuronal signal transduction, memory storage and neuronal circuit organization. Structural plasticity of dendritic spines is correlated with functional plasticity, and is critical for learning and memory. Visualization of the changes of dendritic spines at the ultrastructural level that specifically correlated with their function changes in high throughput would shed light on detailed mechanisms of synaptic plasticity. Here we developed a correlative light and electron microscopy workflow which combines two-photon MNI-glutamate uncaging, pre-embedding immunolabeling, Automatic Tape-collecting Ultramicrotome sectioning and scanning electron microscopy imaging. This method bridges two different visualization platforms, directly linking ultrastructure and function at the level of individual synapses. With this method, we successfully relocated single dendritic spines that underwent long-term potentiation (LTP) induced by two-photon MNI-glutamate uncaging, and visualized their ultrastructures and AMPA receptors distribution at different phases of LTP in high throughput. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

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The purpose of this study was to explore the possibility that music and movement instruction could cause improvement in language arts skills, due to evidence that music and language share processing mechanisms related to auditory perception as described by Patel (2007, 2011a, 2011b, 2014) in the shared syntactic integration resource hypothesis (SSIRH) and OPERA hypothesis. Sixty-two Kindergarten students from a suburban school, near a city in the Midwest, were selected via random assignment to be a part of an experimental or control group. Each group participated in pre- and posttests measuring entrainment and pre-reading skills. ANCOVA results of pre and posttest data revealed no significant difference between the groups. The music and movement instruction did not improve entrainment so results were inconclusive in regard to the impact of entrainment on phonological processing and rapid naming. Future studies might consider a pretest/posttest design with a group that focuses on entrainment without specific music language (Patel, 2008) and a group that conducted music class with the usual songs and descriptive language, to provide evidence regarding whether or not language needs to be combined with music to cause a cognitive transfer of skills. A further comparison of a group that learned to play singing games with a group that learned instrumental music might provide further evidence regarding the role that the combination of music and language might have on reading. Another line of inquiry might involve increasing the length of the intervention period to determine if a year is needed to cause cognitive transfer and ensure that the control group does not receive any music instruction. An additional consideration may be that improvement in entrainment provides a foundation for language processing that does not fully develop or present itself until children reach more challenging levels of reading fluency. Studies that measure student improvement over time would be one way to find evidence that music provides a neurological basis for reading, and language development. Further study possibilities are described in the conclusions of the dissertation. / 2022-11-15T00:00:00Z

Der moderne Leistungs- und Wettkampfsport verfolgt das anspruchsvolle Ziel, die Effizienz von Trainingsprozessen zu steigern und damit die motorische Leistungsfä-higkeit von SportlerInnen zu optimieren. In diesem Zusammenhang kommt dem zentralen Nervensystem eine entscheidende Bedeutung zu, da das Gehirn als Initia-tor jeglicher Willkürbewegungen gilt, indem es neuronale Impulse erzeugt, welche die Ausführung von Bewegungen steuern. Aktuellen neurowissenschaftlichen Untersu-chungen zufolge führen körperliche Aktivität im Allgemeinen und motorisches Lernen sowie regelmäßiges Training im Speziellen zu permanenten funktionellen und struk-turellen Anpassungen des Gehirns (Neuroplastizität). Darüber hinaus konnten bei SportlerInnen neuronale Expertise-Effekte nachgewiesen werden, die sich sowohl in einer angepassten Hirnmorphologie als auch in einer erhöhten Effizienz der neurona-len Verarbeitung manifestieren. Die Rolle des Gehirns und insbesondere motorisch relevanter Hirnareale bei der Ausführung einfacher und/oder komplexer (sportartspe-zifischer) Bewegungen sowie der Einfluss des Gehirns auf die motorische Leistungs-fähigkeit sind bisher jedoch nur unzureichend erforscht. Das Ziel der vorliegenden kumulativen Dissertation war daher unter Anwendung mo-dernster nicht-invasiver Bildgebungs- und Stimulationsverfahren in einem sportbezo-genen Kontext gegenwärtige Forschungslücken zu schließen. Dazu wurden zwei Studien durchgeführt, in denen neuronale Besonderheiten bei SportlerInnen im Ver-gleich zu Nicht-SportlerInnen untersucht wurden. Mit Hilfe der funktionellen Nahinfra-rotspektroskopie (fNIRS) konnte gezeigt werden, dass (1) die Hirnaktivität in Abhän-gigkeit zur Intensität während einer Radsportbelastung zunimmt, was darauf hindeu-tet, dass eine erhöhte Rekrutierung von Muskelfasern ein höheres Maß an neurona-len Ressourcen erfordert. In einer weiteren Studie wurde gezeigt, dass (2) die Erhö-hung der Erregbarkeit in motorisch relevanten Hirnarealen mittels transkranieller Gleichstromstimulation (tDCS) nicht per se zu positiven Effekten auf Verhaltensebe-ne führt, dass jedoch (3) bestimmte Parameter einer motorischen Leistung selektiv moduliert und optimiert werden können. Zusammenfassend unterstreichen die vorliegenden Ergebnisse das Potential nicht-invasiver Bildgebungs- und Stimulationsverfahren in einem sportbezogenen Kontext und tragen neue Erkenntnisse zu einem innovativen Forschungsgebiet bei. Die sys-tematische Anwendung dieser Methoden eröffnet neue Perspektiven in der zukünfti-gen Sportwissenschaft, um Trainingsergebnisse zu diagnostizieren, zu steigern und die motorische Leistungsfähigkeit von SportlerInnen zu optimieren. Dennoch bleiben einige Fragen bezüglich der zugrundeliegenden Mechanismen und möglichen Erklä-rungsansätzen noch unbeantwortet und müssen daher adressiert werden, um das gesamte Potential des Gehirns im Sport nutzen zu können. / Modern competitive and elite sports pursue the challenging goal of increasing the efficiency of training processes and thereby optimizing motor performance in ath-letes. In this context, the central nervous system is of crucial importance, since the brain is considered the initiator of any voluntary movements by generating neural impulses that control the execution of movements. According to current neuroscien-tific research, physical activity in general and motor learning and regular training in particular lead to permanent functional and structural brain adaptations (neuroplastic-ity). Moreover, neuronal expertise effects have been demonstrated in athletes, which are manifested both in adapted brain morphology and in increased efficiency of neu-ronal processing. However, the role of the brain and more specifically of motor-related brain areas during the execution of simple and/or complex (sport-specific) movements as well as the brain’s influence on motor performance still need to be clarified. Hence, the aim of the present cumulative dissertation was to apply state-of-the-art non-invasive brain imaging and stimulation techniques in a sports-related context focusing on current research gaps. Therefore, two studies were conducted to inves-tigate neuronal particularities in athletes compared to non-athletes. Using functional near-infrared spectroscopy (fNIRS), it has been demonstrated that (1) brain activa-tion increases as a function of intensity during a cycling exercise, indicating that in-creased recruitment of muscle fibers requires a higher level of neuronal resources. In a further study, it has been shown that (2) the increase of excitability in motor-related brain areas by means of transcranial direct current stimulation (tDCS) does not per se translate into positive effects on a behavioral level, but that (3) certain parameters of motor performance can be selectively modulated and optimized. In summary, the present findings underline the potential of non-invasive brain imag-ing and stimulation techniques in a sports-related context and contribute novel knowledge to an innovative research field. The systematic application of these meth-ods provides new perspectives in future sports science in order to diagnose and in-crease training outcomes and optimize motor performance in athletes. However, several questions with regards to underlying mechanisms and potential explanations still remain elusive and need to be addressed to use the brain's entire potential in sports.

Objective: To examine the effectiveness of the Listening and Communication Enhancement (LACE) program as a supplement to standard-of-care hearing aid intervention in a Veteran population. Design: A multisite randomized controlled trial was conducted to compare outcomes following standard-of-care hearing aid intervention supplemented with (1) LACE training using the 10-session DVD format, (2) LACE training using the 20-session computer-based format, (3) placebo auditory training (AT) consisting of actively listening to 10 hr of digitized books on a computer, and (4) educational counseling - the control group. The study involved 3 VA sites and enrolled 279 veterans. Both new and experienced hearing aid users participated to determine if outcomes differed as a function of hearing aid user status. Data for five behavioral and two self-report measures were collected during three research visits: baseline, immediately following the intervention period, and at 6 months postintervention. The five behavioral measures were selected to determine whether the perceptual and cognitive skills targeted in LACE training generalized to untrained tasks that required similar underlying skills. The two self-report measures were completed to determine whether the training resulted in a lessening of activity limitations and participation restrictions. Outcomes were obtained from 263 participants immediately following the intervention period and from 243 participants 6 months postintervention. Analyses of covariance comparing performance on each outcome measure separately were conducted using intervention and hearing aid user status as between-subject factors, visit as a within-subject factor, and baseline performance as a covariate. Results: No statistically significant main effects or interactions were found for the use of LACE on any outcome measure. Conclusions: Findings from this randomized controlled trial show that LACE training does not result in improved outcomes over standard-of-care hearing aid intervention alone. Potential benefits of AT may be different than those assessed by the performance and self-report measures utilized here. Individual differences not assessed in this study should be examined to evaluate whether AT with LACE has any benefits for particular individuals. Clinically, these findings suggest that audiologists may want to temper the expectations of their patients who embark on LACE training.

Meditation has in recent decades received attention mainly for its health benefits in western society, not least in the field of neuroscience. Researchers are frequently exploring the link between plasticity in the brain, and the practice of meditation. This systematic review aims to investigate the underlying functional and structural differences in brain mechanisms between long-term meditators and non-meditators, involving different meditation forms. A total of seven peer-reviewed articles were included after being screened for, and meeting inclusion criteria. Final outcomes demonstrated differences between meditators and non-meditators in both functional and structural measures. Some brain regions where changes were identified in meditators included higher-order cognitive areas (i.e., frontal and temporal brain regions). These brain regions are known to be involved in emotional, attentional and memory processing. Reduced connectivity within the default mode network (DMN) is known to be associated with meditation, which was supported in two of the studies. Furthermore, larger gray matter density was found in autonomous control centers (i.e., the brainstem), and larger callosal thickness in meditators. Based on the findings, the practice of long-term meditation appears to be linked with functional and structural changes in various regions of the brain. The findings give insight into the underlying neural correlates and brain plasticity in meditators compared to non-meditators. Nevertheless, future research is necessary for understanding the long-term effects of various meditation forms.

Song production in songbirds is controlled by parts of the brain known as the song control regions (SCRs). During spring, gonads increase in size, males sing to attract mates, and SCRs become larger. This neuroplasticity is controlled by the change in day length and increased plasma testosterone (T) levels. Plasma T can be reduced by stress through the production of corticosterone (CORT), through the production of beta-endorphin, or through direct effects on the testes via the nervous system. We determined the T, estradiol, and CORT hormonal profiles of wild House Finches by capturing and sampling blood from the finches every season for two years. To track SCR neuroplasticity in the wild, we also measured the volume of two specific SCRs, the HVC and RA, every season. We then examined the effects of stress on the finch endocrine system in the wild by performing a 30-minute restraint stress protocol once every season and took blood samples before and after the restraint. To determine whether stress and/or CORT affect neuroplasticity in SCRs, we captured male house finches during winter and brought them into captivity. They were allowed to acclimate to captivity for one month on short days (8L:16D) before we transferred them to long days (16L:8D) and restraint stressed half the birds. We measured their gonads, plasma T and CORT levels, volumes of the HVC and RA, and the number of new neurons in the HVC. HVC volumes were smaller in stressed than non-stressed birds, while RA volumes did not differ. There was no difference in number of new neurons or estimated total number of neurons in the HVC between control and restrained birds. Because the HVC is involved in song production, it is possible that stress negatively impacts singing behavior and reproductive success in House Finches. Future work should address how natural stressors may affect neuroplasticity in birds.

Thèse de doctorat présenté en vue de l'obtention du doctorat en psychologie - recherche intervention, option neuropsychologie clinique (Ph.D) / Selon les dernières estimations mondiales, plus de 43,3 millions d’individus seraient atteints d’une privation visuelle. Autrement dit, l’aptitude de ces individus à percevoir visuellement le monde et les détails qui le composent est presque ou totalement nulle. Bien que privés de l’un des sens les plus importants, ces derniers parviennent à s’adapter et interagir, de façon remarquable, avec l’environnement, et ce, en s’appuyant principalement sur leurs sens préservés. La navigation dans l’espace, la localisation et l’identification d’objets ou de personnes ainsi que la lecture ne sont que quelques exemples permettant d’illustrer la compensation comportementale réalisée par l’entremise des autres canaux sensoriels chez les individus atteints de cécité. L’accomplissement fructueux de telles activités nécessite certes un apprentissage chez les individus aveugles, mais permet également de mettre en lumière qu’au-delà d’une différence de perception visuelle, l’adaptation à une existence vécue dans l’obscurité la plus complète occasionne des changements dans le traitement de l’information en provenance des autres modalités sensorielles. Ces transformations comportementales, issues principalement de la réorganisation cérébrale occasionnée par un déficit perceptif, constitue un sujet d’intérêt pour la communauté scientifique depuis de nombreuses années. Bien que l’apparition des techniques d’imagerie cérébrale non-invasives a permis d’élucider jusqu’à présent de nombreux mystères concernant l’incroyable capacité du cerveau à se modifier sous l’effet de l’expérience, de nombreuses questions demeurent sans réponse. Ainsi, les articles composant cette thèse ont pour objectif principal de contribuer à l’état des connaissances actuelles concernant la réorganisation cérébrale chez les individus atteints de cécité, tant au niveau fonctionnel que structurel, et ce, afin de mieux saisir les répercussions de ces changements cérébraux sur le comportement des non-voyants. Plus particulièrement, nous avons souhaité investiguer l’impact de la privation visuelle précoce sur les régions cérébrales impliquées dans traitement des informations chimiosensorielles (olfactives et trigéminales). Pour ce faire, nous avons d’abord souhaité préciser les mécanismes de réorganisation cérébrale de type structurel prenant place au sein des régions traitant l’information de nature olfactive auprès d’aveugles congénitaux, et ce en comparaison à leurs pairs voyants. L’article 1 de cette thèse révèle que les individus aveugles présentent de multiples altérations cérébrales dans les régions composant le système olfactif. Bien que les aveugles congénitaux inclus dans notre étude présentent des volumes significativement réduits au niveau des bulbes olfactifs, du cortex orbitofrontal et du complexe parahippocampique, leurs performances olfactives, mesurées à l’aide d’épreuves standardisées, demeurent comparables à celles obtenues chez leurs pairs voyants. Nos résultats supportent ainsi la présence d’une réorganisation intramodale au sein du système olfactif chez les aveugles congénitaux, laquelle n’ayant aucune incidence mesurable sur leurs performances olfactive. D’autre part, nous avons souhaité explorer, par le biais de l’imagerie par résonnance magnétique fonctionnelle, si, tout comme pour le traitement de stimuli auditifs et tactiles, les régions habituellement dévolues au traitement visuel participaient, chez l’individu atteint cécité au traitement particulier d’une odeur. Plus précisément, l’article 2 de cette thèse révèle que les aveugles congénitaux sollicitent davantage leur cortex occipital que leurs pairs voyants lors d’une tâche de localisation d’odeurs. Toutefois, lorsque ces mêmes odeurs doivent être identifiées, aveugles et voyants présentent des niveaux d’activité cérébrales comparable dans les régions occipitales. Nos résultats supportent ainsi la présence d’un recrutement intermodal lors du traitement chimiosensoriel de différentes odeurs. Mis ensemble, ces résultats contribuent à une meilleure appréciation des changements cérébraux à la suite d’une privation visuelle, notamment en ce qui concerne les régions impliquées dans le traitement des informations de nature chimiosensorielle. Cette thèse doctorale s’inscrit de façon intéressante au sein des théories de la compensation comportementale présente chez l’individu aveugles, de même que les mécanismes sous-tendant la neuroplasticité structurelle et fonctionnelle des systèmes sensorielles. / According to the latest global estimates, more than 43.3 million people suffer from visual deprivation. In other words, the ability of these individuals to visually perceive the world and the details that compose it is almost or totally absent. Although deprived of one of the most important senses, they manage to adapt and interact with their environment, and this, by relying mainly on their remaining senses. Navigating in space, locating and identifying objects or people, and reading are just few examples that illustrate the behavioral compensation achieved through other sensory channels among individuals living with blindness. The successful accomplishment of such activities certainly requires learning or adaptation. However, it also highlights that beyond a difference in visual perception, adaptation to an existence lived in complete darkness causes changes in the processing of information from other sensory modalities. These behavioral transformations, resulting from the cerebral reorganization caused by a perceptual deficit, have been a subject of interest in the scientific community for many years. Although the emergence of non-invasive brain imaging techniques has, so far, elucidated many mysteries concerning the incredible capacity of the brain to change under the effect of experience, many questions remain unanswered. Thus, the articles included in this thesis have the main objective of contributing to the current knowledge of cerebral reorganization found in individuals living with blindness. More specifically, we wanted to investigate the impact of early visual deprivation on brain regions involved in the processing of chemosensory information (olfactory and trigeminal). To do this, we first evaluated the structural cerebral reorganization taking place among congenitally blind individuals within the olfactory regions. The first study of this thesis reveals that blind individuals present multiple cerebral alterations in the regions composing the olfactory system. More precisely, we found that congenitally blind individuals present significantly reduced olfactory bulb volume, as well as reduction in grey matter density in the orbitofrontal cortex and the parahippocampal complex. Despite this, their olfactory performances, measured using standardized tests, remain comparable to those obtained by their seeing counterparts. Therefore, our results support the presence in congenitally blind individuals of an intramodal reorganization within the olfactory system, which has no measurable impact on their olfactory performance. Through functional magnetic resonance imaging, we wanted to explore if regions that are usually devoted to visual processing are in congenitally blind individuals engaged for the processing of different components of an odor (i.e. olfactory and trigeminal components). More specifically, compared to their sighted counterparts, we found stronger activation in the occipital cortex of blind individuals during our odor localization task. However, when identifying the same odorants, blind and sighted individuals show comparable levels of brain activity in the occipital regions. Our results thus support the presence of cross-modal recruitment during the chemosensory processing of odors. Taken together, these results contribute to a better appreciation of cerebral changes following visual deprivation, particularly in regions involved for the processing of chemosensory information. In an interesting way, the results of this doctoral thesis fit some of the theories stated for blind individuals, such as the structural and functional neuroplasticity of sensory systems.

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