This thesis describes a series of experiments in human observers using neurophysiological and behavioural approaches to investigate the effects of varying haptic stimuli, attentional demand and age on motor control and perception during haptic sensing (i.e., using the hand to seek sensory information by touch). In Experiments I-IV, transcranial magnetic stimulation (TMS) was used to explore changes in corticomotor excitability when participants were actively engaged in haptic sensing tasks. These studies showed that corticospinal excitability, as reflected in motor evoked potential (MEP) amplitude, was greatly enhanced when participants were engaged in different forms of haptic sensing. Interestingly, this extra corticomotor facilitation was absent when participants performed finger movements without haptic sensing or when attention was diverted away from haptic input by a concurrent cognitive task (Exp I). This provided strong evidence that the observed corticomotor facilitation was likely central in origin and related to haptic attention. Neuroimaging has shown activation of the parieto-frontal network likely subserves this aspect of haptic perception. Further, this haptic-specific corticomotor facilitation was finely modulated depending on whether participants focused attention on identifying material (texture) as opposed to geometric properties of scanned surfaces (Exp II). With regards to aging effects, haptic-related corticomotor facilitation was associated with higher recognition accuracy in seniors (Exp III). In line with this, seniors exhibited similar levels of haptic-related corticomotor facilitation to young adults when task demands were adjusted for age (Exp IV). Interestingly, both young and senior adults also showed substantial corticomotor facilitation in the ‘resting’ hand when the ipsilateral hand was engaged in haptic sensing (Exp IV). Simply touching the stimulus without being required to identify its properties (no attentional task demands) produced no extra corticomotor facilitation in either hand or age group, attesting again to the specificity of the effects with regards to haptic attention. In Experiments V-VI, the ability to recognise 2-D letters by touch was investigated using kinematic and psychophysical measures. In Experiment V, we characterized how age affected contact forces deployed at the fingertip. This investigation showed that older adults exhibited lower normal force and increased letter-to-letter variability in normal force when compared to young adults. This difference in contact force likely contributed to longer contact times and lower recognition accuracy in older adults, suggesting a central contribution to age-related declines in haptic perception. Consistent with this interpretation, Experiment VI showed that haptic letter recognition in older adults was characterized not only by lower recognition accuracy but also by substantial increases in response times and specific patterns of confusion between letters. All in all, these investigations highlight the critical interaction of central factors such as attentional demand with aging effects on motor and perceptual aspects of haptic sensing. Of particular significance is the clear demonstration that corticomotor excitability is greatly enhanced when a haptic sensing component (i.e., attending to specific haptic features) is added to simple finger movements performed at minimal voluntary effort levels (typically <15 % of the maximal effort). These observations underline the therapeutic potential of active sensory training strategies based on haptic sensing tasks for the re-education of motor and perceptual deficits in hand function (e.g., subsequent to a stroke). The importance of adjusting attentional demands and stimuli is highlighted, particularly with regards to special considerations in the aging population.

Transcranial magnetic stimulation (TMS) is a 37-year-old non-invasive tool and can be used for diagnostic, therapeutics, and research purposes. In research, TMS is mostly used to stimulate the motor cortex, resulting in a neuroelectric excitatory response called a motor evoked potential (MEP). The resulting nerve signal leads to muscle movement, which can be measured by electromyography (EMG). Majority of previous research has targeted muscles of the upper limbs, due to the relative inaccessibility of the cortical leg area. Thus, the aim of this study is to investigate whether asymmetry occurs during lower limb stimulation and if there is a difference in stimulated muscles between dominant and non-dominant leg. Nine healthy adults conducted cortical stimulation over the motor cortex using double cone coil. EMG was recorded from the rectus femoris, tibialis anterior and abductor hallucis on both left and right leg. Depending on the subject's tolerance, data was collected by delivering 30 or 35 pulses. For each intensity, five MEPs were recorded, starting at 30% of the intensity and increasing in steps of 10%. Results showed no significant difference (p&gt;0,05) between the dominant and non-dominant leg in all three muscles. In conclusion, the study no stimulus response asymmetry between the dominant and non-dominant leg in the respective muscle.

Prediction of the therapeutic response in the treatment of affective disorders using repetitive transcranial magnetic stimulation MUDr. Jakub Albrecht Summary Background: Transcranial magnetic stimulation (TMS) is an effective and safe neuromodulatory treatment of several neuropsychiatric conditions. Treatment resistant depression (TRD) is becoming the leading cause of morbidity and mortality. The design was narutallistic and observational. Methods: The cohort (2016-2018) contains 39 depressed patients (STAR*D grade ≥3). The parameters of TMS were: 10 days of 10 Hz stimulation with an energy of 100 % of motor evoked potential (MEP), 1500 pulses in 15 trains over the left dorsolateral prefrontal cortex. Self-reporting scales were administered prior to and after the final stimulation: Zung's Self-Rating Depression Scale (SDS), Perceived Stress Scale (PSS), Beck's Anxiety Inventory (BAI) and Quick Inventory of Depressive Symptomatology (QIDS-SR). Co-medication was not altered. Results: The subjective effect was significant and widespread with a median decrease: in SDS of 10 points (from 75 ±8.16 to 65 ±9.56), 59 % of patients improved ≥10 % from the baseline; in PSS of 4 points (29 ±5.34 to 25 ±5.90), 62 % improved ≥10 %; in BAI of 4 points (46 ±13.72 to 42 ±11.51), 54 % improved ≥10 %; in QIDS-SR 6 points (17...

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Introduction: Among eating disorders, the binge eating is the most common disorder with prevalence to 7,8%. It is frequently connected with overweight, or obesity. Current treatment of binge eating is based on psychotherapy, pharmacotherapy and regime approach. Recently, repetitive transcranial magnetic stimulation appears as hopeful therapeutic method, for example used with success as an alternative therapy to treatment of resistant major depresion. Because of its non-invasiveness, good tolerability and minimal side effects, new options of its use are studied. It seems to be a promising therapeutic method for treatment of eating disorders. Dorsolateral prefrontal cortex is considered as main experimental target of stimulation for treatment of binge eating disorder. Methods: Study was conceived randomized double-blind placebo controlled. The active group was stimulated by high-frequency rTMS, with stimulation parameters: frequency 10Hz, 1500 pulses, 107s inter-train, 100 % minimal motor threshold and 10 sessions of stimulation. The control grooup was stimulated by sham rTMS coil. Both groups completed FCQ-S and FCQ- T questionnaire before stimulation, after 10. session and one month after 10. session. Results: We noticed statistically significant decrease of craving in FCQ-S questionnaire after 10. session...

Motion-selectivity in human visual cortex comprises a number of different cortical loci including V1, V2, V3A, V3B, hV5/MT+ and V6 (Wandell et al., 2007). This thesis sought to investigate the specific functions of V3A and sub-divisions of hV5/MT+ (TO-1 and TO-2) by using transcranial magnetic stimulation (TMS) to transiently disrupt cortical activations within these areas during psychophysical tasks of motion perception. The tasks were chosen to coincide with previous non-human primate and human neuroimaging literature; translational, radial and rotational direction discrimination tasks and identification of the position of a focus of expansion. These results assert that TO-1 and TO-2 are functionally distinct subdivisions of hV5/MT+, as we have shown that both TO-1 and TO-2 are responsible for processing translational motion direction whilst only TO-2 is responsible for processing radial motion direction. In ipsilateral space, it was found that TO-1 and TO-2 both contribute to the processing of ipsilateral translational motion. Taken in a wider context, further results also suggested that these areas may form part of a network of cortical areas contributing to perception of self-motion (heading/egomotion), as TO-2 was not found to be responsible for processing the position of the central focus of expansion (imperative for self-direction). Instead, area V3A has been implicated as functionally responsible for processing this attribute of vision. Overall it is clear that TO-1, TO-2 and V3A have specific, distinct functions that contribute towards both parallel and serial motion processing pathways within the human brain. / Life Science Research

The resection of tumors within the primary motor cortex is a constant challenge. Although tractography may help in preoperative planning, it has limited application. While it can give valuable information on subcortical fibers, it is less accurate in the cortical layer of the brain. A 38-year-old patient presented with paresis of the right hand and focal epileptic seizures due to a tumor in the left precentral gyrus. Transcranial magnetic stimulation was not applicable due to seizures, so microsurgical resection was performed with preoperative tractography and intraoperative direct electrical stimulation. A histopathological assessment revealed a diagnosis of glioblastoma. Postoperative magnetic resonance imaging (MRI) showed complete resection. The paresis dissolved completely during follow-up. Surgery within the precentral gyrus is of high risk and requires multimodal functional planning. If interpreted with vigilance and consciousness of the underlying physical premises, tractography can provide helpful information within its limitations, which is especially subcortically. However, it may also help in the identification of functional cortex columns of the brain in the presence of a tumor.

<p>Temporal order judgment (TOJ) refers to one’s ability to successively report the temporal order of two tactile stimuli delivered to independent skin sites. The brain regions involved in processing TOJ remain unclear. Research has shown that TOJ performance can be impaired with a conditioning background stimuli and this phenomenon, known as TOJ synchronization (TOJ-S), is suggested to be mediated by inhibitory neural mechanisms within the primary somatosensory cortex (SI) that create perceptual binding across the two skin sites. Continuous theta-burst stimulation (cTBS) over SI impairs tactile spatial and temporal acuity. This dissertation examines the effects of cTBS on TOJ and TOJ-S performance on the hand. In Experiment 1, TOJ and TOJ-S were measured from the right hand before and for up to 34 minutes following 50 Hz cTBS over SI. In Experiment 2, same measurements were obtained bilaterally for up to 42 minutes following 30 Hz cTBS over SI. Compared to pre-cTBS values, TOJ was impaired for up to 42 minutes on the right hand following 30 Hz cTBS. TOJ-S performance was improved for up to 18 minutes on the right hand following 50 Hz cTBS. These experiments reveal two major findings. First, cTBS act upon different inhibitory circuits that are suggested to mediate TOJ and TOJ-S. Second, cTBS parameters may dictate cTBS effects over SI excitability. The findings of this work not only emphasize the significant contributions of SI on tactile temporal perception, it provides novel insight of the underlying neural mechanisms of cTBS effects on SI cortical excitability.</p> / Master of Science in Kinesiology

Résumé : L’interaction entre la douleur et le système moteur est bien connue en clinique et en réadaptation. Il est sans surprise que la douleur est un phénomène considérablement invalidant, affectant la qualité de vie de ceux et celles qui en souffrent. Toutefois, les bases neurophysiologiques qui sous-tendent cette interaction demeurent, encore aujourd’hui, mal comprises. Le but de la présente étude était de mieux comprendre les mécanismes corticaux impliqués dans l’interaction entre la douleur et le système moteur. Pour ce faire, une douleur expérimentale a été induite à l’aide d’une crème à base de capsaïcine au niveau de l’avant-bras gauche des participants. L'effet de la douleur sur la force des projections corticospinales ainsi que sur l’activité cérébrale a été mesuré à l’aide de la stimulation magnétique transcrânienne (TMS) et de l’électroencéphalographie (EEG), respectivement. L’analyse des données EEG a permis de révéler qu'en présence de douleur aiguë, il y a une augmentation de l’activité cérébrale au niveau du cuneus central (fréquence têta), du cortex dorsolatéral préfrontal gauche (fréquence alpha) ainsi que du cuneus gauche et de l'insula droite (toutes deux fréquence bêta), lorsque comparée à la condition initiale (sans douleur). Également, les analyses démontrent une augmentation de l'activité du cortex moteur primaire droit en présence de douleur, mais seulement chez les participants qui présentaient simultanément une diminution de leur force de projections corticales (mesurée avec la TMS t=4,45, p<0,05). Ces participants ont également montré une plus grande connectivité entre M1 et le cuneus que les participants dont la douleur n’a pas affecté la force des projections corticospinales (t=3,58, p<0,05). Ces résultats suggèrent qu’une douleur expérimentale induit, chez certains individus, une altération au niveau des forces de projections corticomotrices. Les connexions entre M1 et le cuneus seraient possiblement impliquées dans la survenue de ces changements corticomoteurs. / Abstract : The interaction between pain and the motor system is well-known in clinic. For instance, it is well documented that pain significantly complicates the rehabilitation of the patients. The aim of the present study was to better understand the cortical mechanisms underlying the interaction between pain and the motor system. Nineteen healthy adults participated in the study. The effect of pain (induced with a capsaicin cream) on brain activity and on the corticomotor system was assessed with electroencephalography (EEG) and transcranial magnetic stimulation (TMS), respectively. For EEG, 15 non-overlapping, 2-seconds artifacts were randomly selected for each participant. Intracranial source current density and functional connectivity was determined using sLORETA software. When participants experienced experimentally-induced inflammatory pain, their resting state brain activity increased significantly in the central cuneus (theta frequency), left dorsolateral prefrontal cortex (alpha frequency), and both left cuneus and right insula (beta frequency; all ts >3.66; all ps<0.01). A pain-evoked increase in the right primary motor cortex (M1) activity was also observed (beta frequency), but only among participants who showed a simultaneous reduction in the strength of the corticospinal projections (quantified using the recruitment curves obtained with TMS; t=4.45, p<0.05). These participants further showed greater beta motor-cuneus connectivity than participants for whom pain did not affect M1 somatotopy (t=3.58, p<0.05). These results suggest that pain-evoked increases in M1 beta power are intimately tied to alterations in corticospinal system. Moreover, we provide evidence that beta motor-cuneus connectivity is related to the corticomotor alterations induced by pain.

The body of work hereby presented aims at better defining the specific mechanisms underlying cognitive control and flexibility, and to investigate the neural substrates that might support these dynamics. More specifically, the anterior cingulate (ACC), dorsolateral prefrontal (dlPFC) and frontopolar (FPC) cortices have been proposed to play a fundamental role in monitoring and detecting the presence of environmental contingencies that require the recruitment of cognitive control (such as competition between responses in the presence of conflicting information), implementing cognitive control, and supporting higher-order cognitive processing, respectively. This thesis investigates the effects of damage to these regions, and of interference with their activity, on these processes. It also argues for the importance of dissociating possible separate cognitive control components that might differently contribute to behavioural adjustments (such as caution and attention/task-relevant processing), and provides one of the first attempts to quantify them within the parameters of a mathematical model of choice response-time, the Linear Ballistic Accumulator (LBA). The results confirm the crucial role of the dlPFC in modulating behavioural adjustments, as both damage and interference with this region’s activity significantly affect measures of conflict-induced behavioural adaptation. It is hypothesized that dlPFC might drive behavioural adjustments by encoding recent conflict history and/or supporting the automatization of a newly advantageous behavioural strategy during the early stages after a change in conflict levels. When a task does not involve competition between a habit and instructed behaviour, lesions or interference with ACC’s activity do not appear to affect behaviour in a manner that is consistent with the classic conflict-monitoring framework. It is suggested that its role might be better described as a more general monitoring and confirmatory mechanism that evaluates both actual and potential outcomes of an action, in order to proactively guide adjustments away from contextually disadvantageous responses. Finally, lesions to the FPC do not affect abstract-rule integration, but do impair the early stages of acquisition of a new abstract rule, when a previously rewarded rule stops being rewarded, and specifically when acquisition is dependent on self-initiated exploration. This suggests a role for FPC in the evaluation of multiple concurrent options in order to aid the development of new behavioural strategies.