Previous research and current models have proposed that the right temporoparietal junction (rTPJ) is crucially involved in the control and distinction of shared representations of action. Hitherto, this assumption has mainly been based on neuroimaging work ( (Spengler, von Cramon, & Brass, 2009); (Spengler, von Cramon, & Brass, 2010)) We tested this hypothesis, that the rTPJ is causally involved in managing shared representations by using repetitive transcranial magnetic stimulation in an offline paradigm to disrupt neural activity in this region. Using a simple imitation-inhibition task we showed that stimulation of the rTPJ led to increased reaction times when participants had to control automatic imitation of a perceived hand movement, as they had to concurrently plan and execute an opposite movement. Our study provides the first empirical evidence that the rTPJ is necessary for managing and navigating within a shared representational system. These results may also have important implications for future theorizing about the role of the TPJ region in controlling shared representations also in other domains, such as somatosensation or emotional experiences.

Des métastases cérébrales vont se développer chez 10 à 30% des patients atteints de cancer. La radiothérapie fait partie des possibilités de traitement, et ceci même si les dommages induits au cerveau par des rayonnements ionisants sont potentiellement importants. Nous proposons l’utilisation de l’Imagerie par Résonance Magnétique fonctionnelle (IRMf) sur le rat pour mieux comprendre ces effets. Ce mémoire traite de la mise en place d’un tel protocole d’IRMf. Les principaux points abordés sont la préparation de l’animal, les différentes insultes et stimulations sensorielles possibles ainsi que la méthode d’acquisition. Notre protocole d’insulte hyperoxique permet de déceler des dommages physiques d’origine vasculaire suite à une intense irradiation dans le cerveau du rat. Toutefois, la même procédure associée à une stimulation mécanique de la patte arrière de l’animal n’amène pas de changement observable à l’IRMf sur un sujet sain. Malgré tout, ce type de stimulation induit une réponse respiratoire, même sous anesthésie d’isoflurane. Une telle méthode n’est donc pas adéquate à l’étude d’animaux anesthésiés, surtout ceux dont la réponse cérébrale pourra avoir été réduite par une irradiation. Quelques améliorations et modifications du protocole seraient possiblement à même de permettre une mesure reproductible de la réponse d’IRMf à une stimulation sensorielle. Le présent mémoire décrit les tentatives de mise en place d’une stimulation sensorielle donnant lieu à une activation IRMf reproductible et localisée. De plus, un protocole de traitement d’image adapté au petit animal ainsi qu’une implémentation de la méthode keyhole ont été mis en place. L’insulte hyperoxique et ses effets sur le cerveau de rat ont été explorés plus en détail.

No description available.

<p>Deep brain stimulation (DBS) is an effective therapy for motor symptoms in Parkinson's disease (PD). DBS efficacy depends on the stimulation parameters, and the current gold standard therapy is high-frequency stimulation (>100 Hz) with constant interpulse intervals and short pulse widths (<210 &#956;s). However, the temporal pattern of stimulation is a novel parameter dimension that has not been thoroughly explored. We used non-regular temporal patterns of DBS to pursue two goals: to better understand the mechanisms of DBS, and to increase the efficacy and efficiency of DBS for PD.</p><p>First, we designed high frequency patterns of non-regular stimulation with distinct features proposed to be important for efficacy and evaluated these patterns in human subjects with PD. Unexpectedly, some non-regular patterns of stimulation improved performance of an alternating finger-tapping task-a proxy for bradykinesia-compared to high frequency regular stimulation. Performance in the motor task was correlated with suppression of beta band power in a computational model of the basal ganglia suggesting a possible mechanism for effective stimulation patterns.</p><p>Inspired by the increased clinical efficacy of non-regular patterns of stimulation with high average frequencies, we developed a non-regular pattern of stimulation that reduced motor symptoms in PD using a low average stimulation frequency. Since the number of potential combinations of interpulse intervals is exceedingly large and it is unclear how such timing should be selected, we applied computational evolution to design an optimal temporal pattern of deep brain stimulation to treat the symptoms of PD. Next, we demonstrated the efficacy of the resulting pattern of stimulation in hemi-parkinsonian rats and humans with PD. Both the optimized stimulation pattern and high frequency stimulation suppressed abnormal oscillatory activity in the basal ganglia in the rat and human, providing a shared mechanism of action for effective stimulation patterns. This innovation could allow patients to achieve battery life savings compared to traditional high frequency stimulation, which will reduce the costs and risks of frequent battery replacement procedures. Further, our approach can be used to design novel temporal patterns of stimulation in other applications of neural stimulation.</p><p>Finally, we explored evoked field potentials in the subthalamic nucleus (STN) in response to DBS. These potentials were evoked by stimulation through one of the contacts on the DBS lead and recorded from the two surrounding contacts. Subthalamic DBS local evoked potentials (DLEPs) have never before been recorded. We characterized the DLEPs, differences across DBS frequencies and time, their relationship to beta frequency oscillations and phase-amplitude coupling, and their dependence on electrode contact location.</p><p>A 3-dimensional biophysical model of DBS in the subthalamic nucleus-globus pallidus externus (GPe) subcircuit was built to explore the neural origin of the DLEPs. The computational model could reproduce the DLEP signal, and it revealed that the quasi-periodic DLEP oscillations are caused by excitatory synaptic currents in STN interrupted periodically by inhibition from GPe.</p><p>DLEP power was correlated with beta band oscillation power in the recordings without DBS, and significant phase-amplitude coupling was observed in a subset of subjects with robust DLEP responses. Together, all available evidence suggested the contact location was an important determinant for the presence and characteristics of DLEP signals. Predictions were made concerning contact location relative to the boundaries of the STN based on the DLEP recordings and insights gained using the computational model, and the predictions were in agreement with blinded post hoc imaging based contact localization for ~70% of contacts predicted to be within STN.</p><p>DLEPs are an exciting new signal with several useful applications. DLEPs could help neurosurgeons verify accurate DBS lead placement or optimal stimulation parameters, probe the pathological basal ganglia, and elucidate the mechanisms of DBS.</p> / Dissertation

Bakgrund: Stroke är en skada som sker i hjärnan i form av en blödning eller infarkt. Stroke medför oftast motoriska symtom i form av nedsatt balans, styrka, koordination och gångförmåga. Musikterapi har som syfte att använda musik och/eller annan auditorisk stimuli för att hjälpa patienten med kognitiva och motoriska nedsättningar som vid exempelvis Parkinson och MS. Syfte: Syftet med den här litteraturstudien var att kartlägga musikterapi som interventionsmetod vid stroke. Metod: Tre stycken frågeställningar låg som grund för den här litteratursammanställningen; Hur används musikterapi i interventionen? Vilken påverkan har musikterapi som intervention på gångförmågan vid strokerehabilitering? Vilken påverkan har musikterapi som intervention på funktionen av de övre extremiteterna vid strokerehabilitering Fem akademiska databaser användes för att hämta artiklarna; PubMed, PEDro, Scopus, Web of Science och CINAHL. Artiklarna kvalitetsgranskades med hjälp av Fribergs granskningsmall och en PICO-tabell användes för att klargöra syftet av studien. Resultat: 16 artiklar inkluderades i studien. Artiklarna visade att musikterapeutisk behandling gav övervägande goda resultat både på nedsatt gångförmåga och nedsatt funktion av övre extremitet. Framförallt gav Rhythmic Auditory Stimulation (RAS) och keyboard/piano spelande goda resultat. Konklusion: Det kan ses en positiv effekt av musikterapi som behandlingsmetod vid stroke. RAS visade på goda förbättringar vid nedsatt gångförmåga och keyboard/piano spelande goda resultat vid nedsatt funktion av övre extremitet. Mer forskning behövs dock gällande musikterapins effekter på övre extremitet vid strokerehabilitering.

The capability of the brain to control the body has been recognised for millennia. This thesis evaluates the ability of neurosurgery, in the form of DBS, to manipulate the motor system, in which it is already established as a therapy, and the cardiovascular and respiratory systems, in which its application as a therapy would represent a major paradigm shift in medical practice. Patients with in-dwelling deep brain stimulators were enrolled in a series of experiments. Methodological techniques included the recording and analysis of cardiovascular and lung function indices, deep brain local field potentials, tremor severity scores and diffusion tensor tractograms. The results demonstrate that DBS at specific subcortical sites can ameliorate the abnormal response to autonomic challenges in Parkinson's disease and improve lung function by up to 15% with a coincident synchronisation of local field potential frequency. Further, the results demonstrate that probabilistic tractography in humans confirms the connections of the motor thalamus seen in animal tracer studies and that motor thalamus DBS for essential tremor is efficacious based on novel trial design and analysis methods. In conclusion, the thesis provides the first Level I evidence for the efficacy of DBS in essential tremor and suggests that probabilistic tractography can aid surgical targeting of the motor thalamus. It also finds that DBS reduces the cardiovascular dysfunction seen in Parkinson's disease and improves respiratory performance in humans with a coincident electrophysiological correlate in the subcortical brain. These findings have important implications for the future application of neurosurgery in diseases of not just the motor system but also the cardiovascular and respiratory systems.

The thesis designs, constructs, and tests an electrically small dipole antenna probe for the measurement of electric field distributions induced by a transcranial magnetic stimulation (TMS) coil. Its unique features include high spatial resolution, large frequency band from 100 Hz to 300 kHz, efficient feedline isolation via a printed Dyson balun, and accurate mitigation of noise. Prior work in this area is thoroughly reviewed. The proposed probe design is realized in hardware; implementation details and design tradeoffs are described. Test data is presented for the measurement of a CW capacitor electric field, demonstrating the probe’s ability to properly measure conservative electric fields caused by a charge distribution. Test data is also presented for the measurement of a CW solenoidal electric field, demonstrating the probe’s ability to measure non-conservative solenoidal electric fields caused by Faraday’s law of induction. Those are the primary fields for the transcranial magnetic stimulation. Advantages and disadvantages of this probing system versus those of prior works are discussed. Further refinement steps necessary for the development of this probe as a valuable TMS instrument are discussed.

Perception is the result of more than just the unbiased processing of sensory stimuli. At each moment in time, sensory inputs enter a circuit already impacted by signals of arousal, attention, and memory. This thesis aims to understand the impact of such internal states on the processing of sensory stimuli. To do so, computational models meant to replicate known biological circuitry and activity were built and analyzed. Part one aims to replicate the neural activity changes observed in auditory cortex when an animal is passively versus actively listening. In part two, the impact of selective visual attention on performance is probed in two models: a large-scale abstract model of the visual system and a smaller, more biologically-realistic one. Finally in part three, a simplified model of Hebbian learning is used to explore how task context comes to impact prefrontal cortical activity. While the models used in this thesis range in scale and represent diverse brain areas, they are all designed to capture the physical processes by which internal brain states come to impact sensory processing.

Studies of cerebellum-like circuits in fish have demonstrated that synaptic plasticity shapes the motor corollary discharge responses of granule cells into highly-specific predictions of self- generated sensory input. However, the functional significance of such predictions, known as negative images, has not been directly tested. Here we provide evidence for improvements in neural coding and behavioral detection of prey-like stimuli due to negative images. In addition, we find that manipulating synaptic plasticity leads to specific changes in circuit output that disrupt neural coding and detection of prey-like stimuli. These results link synaptic plasticity, neural coding, and behavior and also provide a circuit-level account of how combining external sensory input with internally-generated predictions enhances sensory processing. In addition, the mammalian dorsal cochlear nucleus (DCN) integrates auditory nerve input with a diverse array of sensory and motor signals processed within circuity similar to the cerebellum. Yet how the DCN contributes to early auditory processing has been a longstanding puzzle. Using electrophysiological recordings in mice during licking behavior we show that DCN neurons are largely unaffected by self-generated sounds while remaining sensitive to external acoustic stimuli. Recordings in deafened mice, together with neural activity manipulations, indicate that self-generated sounds are cancelled by non-auditory signals conveyed by mossy fibers. In addition, DCN neurons exhibit gradual reductions in their responses to acoustic stimuli that are temporally correlated with licking. Together, these findings suggest that DCN may act as an adaptive filter for cancelling self-generated sounds. Adaptive filtering has been established previously for cerebellum-like sensory structures in fish suggesting a conserved function for such structures across vertebrates.

No description available.