<p dir="ltr">Localizing movements in the external space is crucial for animals to navigate safely, find food, avoid predators, and interact with their surroundings. Efficient localization during body movements requires the brain to distinguish between externally generated movements and self-generated ones. This involves integrating external stimulation with a continuous estimate of one's body position, to isolate external motion by suppressing sensations arising from self-motion.</p><p dir="ltr">To explore the neural mechanisms underlying object localization during active touch, we focused on the mouse superior colliculus (SC), which harbors multiple egocentric maps of sensorimotor space. Our studies revealed that SC neurons exhibit a rapidly adapting tactile response during externally generated touch. The response is significantly attenuated during self-generated touch, thus enhancing the ability to distinguish between external and self-induced tactile stimuli. Additionally, the direction of external motion is precisely encoded in the firing rates of these tactile-responsive neurons, indicating a specialized localization mechanism within the SC.</p><p dir="ltr">In scenarios devoid of external stimuli, SC neural activity accurately reflects the kinematics of self-motion, such as whisker position and locomotion speed, capturing past, present, and future body positions. Half of the neurons that encode self-motion also respond to external tactile stimuli. This dual functionality suggests that these neurons not only track self-motion but also engage in the processing of external tactile information. The magnitude of the external tactile response in these neurons is modulated by the state of self-motion upon touch. These results suggest that SC neurons integrate internal estimates of body movements with external tactile inputs to compute the egocentric distance of objects.</p>

Sensorimotor integration processes play a central role in daily life and require that different sources of sensory information become integrated: i.e. the information related to the object being under control of the agent (i.e. indicator) and the information about the goal of acting. Yet, how this is accomplished on a neurophysiological level is contentious. We focus on the role of theta- and beta-band activities and examine which neuroanatomical structures are involved. Healthy participants (n = 41) performed 3 consecutive pursuit-tracking EEG experiments in which the source of visual information available for tracking was varied (i.e. that of the indicator and the goal of acting). The initial specification of indicator dynamics is determined through beta-band activity in parietal cortices. When information about the goal was not accessible, but operating the indicator was required nevertheless, this incurred increased theta-band activity in the superior frontal cortex, signaling a higher need for control. Later, theta- and beta-band activities encode distinct information within the ventral processing stream: Theta-band activity is affected by the indicator information, while beta-band activity is affected by the information about the action goal. Complex sensorimotor integration is realized through a cascade of theta- and beta-band activities in a ventral-stream-parieto-frontal network.

Thesis (MOccTher (Interdisciplinary Health Sciences. Occupational Therapy))--University of Stellenbosch, 2010. / AFRIKAANSE OPSOMMING: AGTERGROND Dit is bekend dat vroeggebore babas met ʼn baie lae geboortemassa ʼn hoër insidensie van ontwikkelings-, gedrags- en mediese agterstande en verskeie leerprobleme toon teen die tyd dat hulle skoolgaande ouderdom bereik. Kommer bestaan ook oor die omgewingseffek van die neonatale intensiewe sorgeenheid op die sensoriese ontwikkeling van die vroeggebore baba en hoe dit tot bogenoemde agterstande kan bydra. Daar is verskillende benaderings wat daarop aanspraak maak dat hulle die probleem kan oplos, met kangaroemoedersorg (‘kangaroo mother care’) en ontwikkelingsorg (‘developmental care’) wat in die literatuur uitgesonder is as besonders belowend. Met die aanvang van hierdie studie was daar nog geen empiriese studies in die literatuur gerapporteer wat enige aansprake van hierdie benaderings bevestig het nie. Daar was dus ʼn behoefte vir ʼn empiries-nagevorsde program wat prakties in die neonatale intensiewe eenheid toegepas kon word met die oog op die vermindering van omgewingstressors ten opsigte van die vroeggebore baba se sensoriese sisteme. DOEL Die doel met die studie was om die invloed te bepaal van ʼn Sensoriese Ontwikkelingsorgprogram (‘Sensory Developmental Care Programme’), wat ʼn spesifieke kangaroemoedersorg- protokol insluit, op die sensoriese ontwikkeling van die vroeggebore baba met 'ʼn baie lae geboortemassa tot en met die ouderdom van 18 maande (gekorrigeerde ouderdom). METODOLOGIE ʼn Ewekansig-gekontroleerde studie is uitgevoer. Die studiesteekproef het bestaan uit 89 vroeggebore babas met ʼn baie lae geboortemassa wat in ʼn periode van 24 maande toegelaat is tot die neonatale eenheid van Tygerberg Hospitaal in Kaapstad, Suid-Afrika. Die babas is gewerf op grond van sekere kriteria en is dan daarna ewekansig aan een van twee groepe toegeken: 1) die intervensiegroep het sorg ontvang volgens die Sensoriese Ontwikkelingsorgprogram vir 10 dae; en 2) die kontrolegroep het ook vir 10 dae die standaardsorg van die eenheid ontvang. Die intervensiegroep het uit 45 babas bestaan, van wie 22 die studie voltooi het, terwyl die kontrolegroep uit 44 babas bestaan het van wie 20 die studie voltooi het. Beide studiegroepe is opgevolg op 6, 12 en 18 maande (gekorrigeerde ouderdom), by welke geleentheid die Sensoriese Funksietoets vir Babas (‘Test of Sensory Functions in Infants’) telkens toegepas is vir die assessering van sensoriese ontwikkeling. Op 18 maande (gekorrigeerde ouderdom) is ʼn assessering met die Griffiths Ontwikkelingskaal ook gedoen om funksies in die ander ontwikkelingsareas van die babas te bepaal. Toetsresultate is geanaliseer met behulp van herhaalde ANOVAmetings en die Bonferoni t-prosedure om die effek van die Sensoriese Ontwikkelingsorgprogram op die sensoriese ontwikkeling van die babas tot en met 18 maande (gekorrigeerde ouderdom) te bepaal. RESULTATE Die resultate van die vergelyking van die prestasie van beide groepe (groep-effek), gemeet met behulp van die Sensoriese Funksietoets vir Babas, is van groot belang vir hierdie studie. Die intervensiegroep het betekenisvol verskil op die totale telling (p<0.00), sowel as op die volgende vier van die vyf subtoets-tellings: respons op diepdruk (‘tactile deep pressure’) (p<0.03); motoriese aanpassingsreaksies (p<0.03); visuele tas-integrasie (p<0.00); en respons op vestibulêre stimulasie (p<0.01). GEVOLGTREKKING Die resultate van die studie dui aan dat die babas in die intervensiegroep baat gevind het by die Sensoriese Ontwikkelingsorgprogram met betrekking tot hul sensoriese funksies tot en met die ouderdom van 18 maande (gekorrigeerde ouderdom). Die Sensoriese Ontwikkelingsorgprogram het geblyk prakties sowel as suksesvol te wees met betrekking tot sy doel. Die Program sou daarom met vrug in ander neonatale intensiewe sorgeenhede aangewend kon word. / ENGLISH ABSTRACT: BACKGROUND Premature infants of very low birth weight are known to be inclined to developmental, medical, behavioural and various learning deficiencies by the time they reach schoolgoing age. Concerns have been raised about the effect of the neonatal intensive care unit environment on the sensory development of the premature infant and how this could contribute to these deficiencies. Various approaches claim to address this problem, of which kangaroo mother care and developmental care have in the literature been singled out as particularly promising. However, at the commencement of this study no empirical studies had been reported in the literature to confirm any of the claims of these approaches. Therefore, a need existed for an empirically researched programme that could be practically applied in the neonatal intensive care unit with a view to reducing environmental stressors regarding the sensory systems of the premature infant. AIM The aim of this study was to determine the influence of a Sensory Developmental Care Programme, which incorporated a specific kangaroo mother care protocol, on the sensory development of the very low birth weight premature infant, up to the age of 18 months (corrected age). METHODOLOGY A randomised controlled study was conducted. The study sample consisted of 89 very low birth weight premature infants, admitted during a 24-month period to the neonatal care unit at Tygerberg Hospital in Cape Town, South Africa. The infants were recruited by means of certain criteria and then randomly assigned to one of two groups: 1) the intervention group was cared for according to the Sensory Developmental Care Programme for ten recorded days; and 2) the control group that received the standard care of the unit, also for ten days. The intervention group consisted of 45 infants of whom 22 completed the study, while the control group consisted of 44 infants of whom 20 completed the study. Both study groups were followed up at six, 12 and 18 months (corrected age) when the Test of Sensory Functions in Infants was used to do a sensory developmental assessment. At 18 months (corrected age) a Griffiths Developmental Scale assessment was also conducted to determine function in other areas of development. Test results were analysed using repeated measures of ANOVA, and the Bonferoni t procedure to determine the effect that the Sensory Developmental Care Programme had on the sensory development of the infant up to 18 months (corrected age). RESULTS The results of the comparison of the performance of both groups (group effect), measured by the Test of Sensory Functions in Infants are of great importance to this study. The intervention group had a significant difference on the total score (p<0.00), as well as on the following four of the five sub-tests scores: reactivity to tactile deep pressure (p<0.03); adaptive motor functions (p<0.03); visual-tactile integration (p<0.00); and reactivity to vestibular stimulation (p<0.01). CONCLUSION The results of this study signify that the infants in the intervention group benefited from the Sensory Developmental Care Programme concerning their sensory functions up to the age of 18 months (corrected age). The Sensory Developmental Care Programme was demonstrated to be both practical and successful in terms of its aims. The Programme could therefore be fruitfully utilised in other neonatal intensive care units.

Lorsque le système nerveux central est exposé à une nouvelle association visuoproprioceptive, l’adaptation de la carte visuomotrice est nécessaire afin d’exécuter des mouvements précis. L’efficacité de ces processus adaptatifs correspond aussi à la capacité à les transférer dans des contextes différents de l’apprentissage de cette nouvelle association, par exemple dans de nouvelles régions de l’espace extrapersonnel (généralisation spatiale). Comme le contexte exerce une influence considérable sur les processus adaptatifs, les composantes multidimensionnelles de la tâche et de la perturbation pourraient constituer des éléments affectant considérablement l’adaptation et la généralisation spatiale. Ce mémoire présente une étude exploratoire de l’adaptation à une perturbation triaxiale, introduite graduellement, réalisée dans un environnement virtuel tridimensionnel et sa généralisation spatiale. Nos résultats suggèrent que les trois axes de l’espace présentent des différences importantes quant aux processus adaptatifs qui les sous-tendent. L’axe vertical présente à la fois une plus grande variabilité et de plus grandes erreurs spatiales au cours de l’adaptation comparativement à l’axe sagittal et à l’axe horizontal, tandis que l’axe sagittal présente une plus grande variabilité que l’axe horizontal. Ces différences persistent lors de l’effet consécutif, l’axe vertical affichant une désadaptation importante. Le test de généralisation spatiale montre une généralisation à l’ensemble des cibles, cependant, la généralisation semble plus faible le long de l’axe vertical. Ces résultats suggèrent que l’adaptation à une translation tridimensionnelle se généralise à travers l’espace le long des trois axes de l’espace et renforcent l’idée que le système nerveux central utilise une stratégie de décomposition modulaire des composantes de l’espace tridimensionnel. / We explored visuomotor adaptation and spatial generalization in the context of three-dimensional reaching movements performed in a virtual reality environment using a learning paradigm composed of four phases: pre-exposure, baseline, learning, and post-exposure (aftereffect and generalization). Subjects started by performing five reaching movements to six 3D memorized target locations without visual feedback (pre-exposure). Next, subjects performed twelve reaching movements to the learning target with veridical visual feedback (baseline). Immediately after, the 3D visuomotor dissociation (horizontal, vertical and sagittal translations) between actual hand motions and visual feedback of hand motions in the 3D virtual environment was gradually introduced (learning phase). Finally, subjects aimed at the pre-exposure and baseline targets without visual feedback (post-exposure). Although subjects were unaware of the visuomotor perturbation, they showed movement adaptation for each component of the triaxial perturbation, but they displayed reduced adaptation rate along the vertical axis. Subjects persisted in applying the new visuomotor association when the perturbation was removed, but the magnitude of this post-exposure shift was lower along the vertical axis. Similar trends were observed for movement aimed at pre-exposure targets. Furthermore, these post-exposure shifts were, on average, greater along the horizontal and sagittal axes relative to the vertical axis. These results suggest that the visuomotor map may be more adaptable to shifts in the horizontal and sagittal directions, than to shifts in the vertical direction. This finding supports the idea that the brain may employ a modular decomposition strategy during learning to simplify complex multidimensional visuomotor tasks.

Contemporary understanding of human visual spatial attention rests on the hypothesis of a top-down control sending from cortical regions carrying higher-level functions to sensory regions. Evidence has been gathered through functional Magnetic Resonance Imaging (fMRI) experiments. The Frontal Eye Field (FEF) and IntraParietal Sulcus (IPS) are candidates proposed to form the frontoparietal attention network for top-down control. In this work we examined the influence patterns between frontoparietal network and Visual Occipital Cortex (VOC) using a statistical measure, Granger Causality (GC), with fMRI data acquired from subjects participated in a covert attention task. We found a directional asymmetry in GC between FEF/IPS and VOC, and further identified retinotopically specific control patterns in top-down GC. This work may lead to deeper understanding of goal-directed attention, as well as the application of GC to analyzing higher-level cognitive functions in healthy functioning human brain. / by Wei Tang. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

Le feedback auditif se définit comme un signal auditif qui contient de l'information sur un mouvement. Il a été montré que le feedback auditif peut guider le mouvement en temps réel, mais son influence sur l'apprentissage moteur est moins clair. Cette thèse a pour but d'examiner l'influence du feedback auditif sur l'apprentissage moteur, en se focalisant sur le contrôle temporel des mouvements. Premièrement, nous étudions l'apprentissage moteur chez les non-musiciens sains et montrons qu'ils bénéficient de l'information temporelle contenue dans le feedback auditif et qu'ils sont sensibles aux distortions de cette information temporelle. Deuxièmement, nous appliquons ces connaissances à la rehabilitation de patients cérébro-lésés. Nous trouvons que ces patients améliorent leurs capacités de mouvement mais ne dépendent pas de la correspondance temporelle entre le mouvement et le son. Paradoxalement, ces patients ont même benéficié des distortions temporelles dans le feedback. Troisièmement, nous étudions les experts musicaux, car ils ont établi des liens particulièrement forts entre leur mouvement et le son. Nous développons de nouveaux outils d'analyse qui nous permettent de séparer les déviations temporelles en variation systématique et non-systématique. Le résultat principal est que ces experts sont devenu largement indépendents du feedback auditif. La proposition centrale de cette thèse est que le feedback auditif joue un rôle dans l'apprentissage moteur de la regularité, mais la façon dont le cerveau l'utilise dépend de la population étudiée. Ces résultats donnent une nouvelle perspective sur l'intégration audio-motrice et contribuent au développement de nouvelles approches pour l'apprentissage de la musique et la réhabilitation.

Orientador: José de Anchieta de Castro e Horta Júnior / Resumo: O reflexo auditivo de sobressalto (ASR) é uma contração rápida e intensa da musculatura estriada esquelética da face e do corpo frente a um estímulo sonoro inesperado e de alta intensidade. O ASR pode ser modificado em diversas condições, como na inibição por estímulo prévio (PPI), que se caracteriza pela diminuição da amplitude do ASR quando o estímulo sonoro de alta intensidade é precedido por um estímulo de menor intensidade. As respostas de ASR e PPI são avaliadas de forma não invasiva no homem e em roedores com grande homologia e têm sido utilizadas na pesquisa básica e clínica. Além disso, se encontram alteradas em diversas afecções neurológicas e psiquiátricas que apresentam déficits no processamento sensório-motor. No homem, existem diferenças na PPI relacionadas ao gênero, que refletem as variações hormonais ao longo do ciclo menstrual. Entretanto, estudos em roedores se mostram conflitantes em relação às diferenças no ASR e na PPI entre machos e fêmeas, raramente mencionando as possíveis variações ao longo do ciclo estral, o que dificulta a interpretação de resultados experimentais em fêmeas e a sua translação para os resultados obtidos no homem. Para avaliar a influência do gênero e das fases do ciclo estral no ASR, foram estudados 10 machos e 28 fêmeas de ratos Wistar adultos. O ciclo estral das fêmeas foi acompanhado diariamente e todos os animais foram submetidos a sessões de avaliação do ASR e PPI. Nas fêmeas, as concentrações plasmáticas de estr... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The acoustic startle reflex (ASR) is a fast and intense motor reaction that promotes skeletal striated muscles contraction of face and body, in response to an unexpected and high-intensity sound stimulus. The ASR has many modulations such as prepulse inhibition (PPI) which is characterized by reduced amplitude of ASR when the triggering sound stimulus is preceded by a lower-intensity stimulus. The ASR and PPI responses can be measured non-invasively in humans and rodents with high homology and have been used for basic and clinical research. Additionally, they are disrupted in many neurological and psychiatric conditions that show deficits in sensorimotor processing. In humans, it is known that there are gender-related differences in PPI, which reflect hormonal changes that occur during the menstrual cycle. However, studies in rodents are conflicting regarding the differences in ASR and PPI between males and females, rarely mentioning the possible variations during the estrous cycle. This fact makes it difficult to interpret experimental results in females and their translation to results obtained in humans. To assess the influence of gender and estrous cycle in ASR, 10 males and 28 females adult Wistar rats were studied. Females’ estrous cycle was monitored daily and all animals were subjected to sessions of ASR and PPI evaluation. In females, estradiol and progesterone plasmatic concentrations were determinated. The brains of 3 males and 3 females in each phas... (Complete abstract click electronic access below) / Mestre

Bibliographical record: KOLÁŘ, J. The Use of Hearing Perception Elimination in Motoric Activity. Prague: Charles University, 2nd Faculty of Medicine, Department of Rehabilitation and Sports Medicine 2020. 79 p. Thesis supervisor prof. PaedDr. Pavel Kolář, Ph.D. Abstract This thesis focuses on the importance and significance of human senses - especially hearing and vision - in connection with a performance of a motor activity. The theoretical part brings a summary of knowledge about the influence of hearing and vision on human movements and the induction of changes in the body during the elimination (deprivation) of some of the senses. Furthermore, in this part we briefly inform about the mutual relationship between vision and hearing, ideomotor functions, an auditory deprivation and lastly, we try to point out the possibilities and importance of a neuro-visual complex therapy. The main goal of the practical part is to prove the influence of hearing on the motor expression of the tested probands. A secondary goal of the practical part is to determine the influence of the quality of a visual perception on a motor expression and whether there can be an immediate intensification of a visual perception during auditory deprivation. Methodology: As a part of the main goal of the practical part, we tested 77...

For adaptive goal-directed action, the brain needs to monitor action performance and detect errors. The corresponding information may be conveyed via different sensory modalities; for instance, visual and proprioceptive body position cues may inform about current manual action performance. Thereby, contextual factors such as the current task set may also determine the relative importance of each sensory modality for action guidance. Here, we analyzed human behavioral, functional magnetic resonance imaging (fMRI), and magnetoencephalography (MEG) data from two virtual reality-based hand–target phase-matching studies to identify the neuronal correlates of performance monitoring and error processing under instructed visual or proprioceptive task sets. Our main result was a general, modality-independent response of the bilateral frontal operculum (FO) to poor phase-matching accuracy, as evident from increased BOLD signal and increased source-localized gamma power. Furthermore, functional connectivity of the bilateral FO to the right posterior parietal cortex (PPC) increased under a visual versus proprioceptive task set. These findings suggest that the bilateral FO generally monitors manual action performance; and, moreover, that when visual action feedback is used to guide action, the FO may signal an increased need for control to visuomotor regions in the right PPC following errors.

L’intégrité de notre système sensorimoteur est essentielle aux interactions adéquates avec notre environnement. Dans la maladie de Parkinson (MP), l’efficacité des interactions quotidiennes entre le corps et l’environnement est fréquemment réduite et diminue la qualité de vie. La MP est une maladie neurodégénérative résultant prioritairement d’une perte neuronale dopaminergique dans les ganglions de la base (GB). Cette dégénérescence altère le fonctionnement normal de la circuiterie associant les GB au cortex cérébral. L’administration de médications dopaminergiques permet d’améliorer les principaux symptômes cliniques moteurs de la MP. Cette thèse porte sur les rôles des GB dans les processus de traitement et d’intégration des informations sensorielles visuelle et proprioceptive et dans les mécanismes d’adaptation visuomotrice. Elle s’intéresse également à l’influence de la médication dopaminergique sur ces fonctions sensorimotrices. Nous avons réalisé trois études comportementales, utilisant l’atteinte manuelle tridimensionnelle comme modèle expérimental. Dans chacune de ces études, nous avons comparé la performance de personnes âgées en santé à celle de personnes souffrant de la MP avec et sans leur médication antiparkinsonienne quotidienne. Ces trois études ont été réalisées à l’aide d’un système d’analyse de mouvement et une station de réalité virtuelle. Dans la première étude, nous avons évalué si les GB sont prioritairement impliqués dans l’intégration sensorimotrice ou le traitement des informations proprioceptives. Pour se faire, nous avons testé la capacité des patients MP à effectuer des atteintes manuelles tridimensionnelles précises dans quatre conditions variant la nature des informations sensorielles (visuelles et/ou proprioceptives) définissant la position de la main et de la cible. Les patients MP ont effectué, en moyenne, de plus grandes erreurs spatiales que les personnes en santé uniquement lorsque les informations proprioceptives étaient la seule source d’information sensorielle disponible. De plus, ces imprécisions spatiales étaient significativement plus grandes que celles des personnes en santé, seulement lorsque les patients étaient testés dans la condition médicamentée. La deuxième étude présentée dans cette thèse a permis de démontrer que les imprécisions spatiales des patients MP dans les conditions proprioceptives étaient le résultat de déficits dans l’utilisation en temps réel des informations proprioceptives pour guider les mouvements. Dans la troisième étude, nous avons évalué si les GB sont prioritairement impliqués dans les mécanismes d’adaptation visuomotrice explicite ou implicite. Pour se faire, nous avons testé les capacités adaptatives des patients MP dans deux tâches variant le décours temporel de l’application d’une perturbation visuomotrice tridimensionnelle. Dans la tâche explicite, la perturbation était introduite soudainement, produisant de grandes erreurs détectées consciemment. Dans la condition implicite, la perturbation était introduite graduellement ce qui engendrait de petites erreurs non détectables. Les résultats montrent que les patients MP dans les conditions médicamentée et non médicamentée présentent des déficits adaptatifs uniquement dans la tâche explicite. Dans l’ensemble, les résultats expérimentaux présentés dans cette thèse montrent que la médication dopaminergique n’améliore pas le traitement des afférences proprioceptives et l’adaptation visuomotrice des personnes souffrant de la MP. Ces observations suggèrent que les dysfonctions dans les circuits dopaminergiques dans les GB ne sont pas les seules responsables des déficits observés dans ces fonctions sensorimotrices. / The integrity of our sensorimotor system is essential for adequate interactions with the environment. In Parkinson’s disease (PD), the efficiency of the daily interactions between the body and the environment is often reduced and interfere with quality of life. PD is a neurodegenerative disease resulting primarily from a dopaminergic neuronal loss in the basal ganglia (BG). This progressive loss of neurons alters the normal functioning of the BG-cortical circuitry. Dopaminergic medication is well known to remediate the major clinical motor symptoms of PD. This thesis investigates the role of the BG in the processing and integration of visual and proprioceptive sensory information and in visuomotor adaptation. This thesis also explores the influence of dopaminergic medication on these sensorimotor functions. We performed three behavioral studies using three-dimensional reaching movements as an experimental model. In each study, we compared the performance of healthy controls and individuals suffering from PD, while in the non-medicated condition and when on their regular daily antiparkinsonian medication. These three studies were performed using a movement analysis system and a virtual reality station. In the first study, we evaluated whether the BG are primarily involved in sensorimotor integration or in the processing of proprioceptive sensory information. We tested the ability of PD patients to perform accurate reaching movements in four conditions in which the sensory signals defining target and hand positions (vision and/or proprioception) varied. On average, PD patients made larger spatial errors than healthy controls when proprioception was the only source of sensory information available. Furthermore, these movement inaccuracies were significantly larger than those of healthy controls only when PD patients where tested in the medicated condition. The second study presented in this thesis demonstrated that the greater movement inaccuracies of PD patients in the proprioceptive conditions resulted mainly from impaired use of proprioceptive information for on-line movement guidance. In the third study, we evaluated whether the BG are primarily involved in explicit or implicit visoumotor adaptation mechanisms. Visuomotor adaptation skills of non-medicated and medicated patients were assessed in two reaching tasks in which the size of spatial errors made during adaptation was manipulated by varying the temporal evolution of a three-dimensional visuomotor perturbation across trials. In the explicit task, the visuomotor perturbation was applied suddenly resulting in large consciously detected initial spatial errors, whereas in the implicit task, the visuomotor perturbation was gradually introduced in small undetectable steps such that subjects never experienced large movement errors. Results indicate that both non- medicated and medicated PD patients showed markedly impaired visuomotor adaptation only in the explicit task. Together, the different experimental data presented in this thesis indicate that dopaminergic medication does not improve proprioceptive processing and visuomotor adaptation skills of PD patients. These observations suggest that dysfunction of dopaminergic circuits within the BG is not solely responsible for the reported sensorimotor deficits.