Correlations between EEG and clinical outcome in chronic neuropathic pain: surgical effects and treatment resistance

Chronic neuropathic pain may require a neurosurgical treatment, but for reasons that have not been fully explored yet, a significant number of patients do not benefit from the intervention. We compared the resting EEG of 15 healthy controls to the EEG of 23 chronic neuropathic pain patients before and 12months after treatment by the central lateral thalamotomy (CLT). A patient subgroup had a high (n = 14, pain relief (PR) ≥ 50%) and another subgroup a low (n = 9, PR < 50%) postoperative PR. EEG spectral power and source localization of the high PR patients were normalized postoperatively. In contrast, low PR patients showed postoperative maintenance of insular, cingulate and prefrontal overactivities, and their frustration values were positively correlated with cingulate and prefrontal activity. These findings demonstrate a normalizing effect of CLT on cortical activity and suggest that treatment resistance is associated with a frustration-based dynamic

Cortical activation by a biological motion stimulus with limited lifetime

Ein Forschungsschwerpunkt in der menschlichen Bewegungsanalyse wurde auf die neuronalen Verarbeitungsprozesse biologischer Bewegung gelegt. In den meisten Studien wurde die Wahrnehmung von Lichtpunkt-Läufern untersucht, bei denen Lichtpunkte an festen oder variablen Körperpositionen gezeigt wurden. In den Experimenten dieser Arbeit habe ich mit Hilfe der fMRT herausgefunden, dass speziell formverarbeitende Gehirnregionen an der Verarbeitung biologischer Bewegung beteiligt sind. Dies widerspricht der allgemein angenommenen Theorie zur Wahrnehmung biologischer Bewegung. Für peripher präsentierte Lichtpunkt-Läufer wurde rechtsseitige pSTG und kontralaterale somatosensorische und fusiforme gyrus Aktivierung beobachtet. Zusammenfassend deuten meine Resultate darauf hin, dass ein Netzwerk aus visuellen und nicht-visuellen Arealen benötigt wird, um biologische Bewegung zu erkennen. Damit ist es z.B. möglich die Absichten einer beobachteten Handlung richtig zu interpretieren

Temporo-insular enhancement of EEG low and high frequencies in patients with chronic tinnitus. QEEG study of chronic tinnitus patients

<p>Abstract</p> <p>Background</p> <p>The physiopathological mechanism underlying the tinnitus phenomenon is still the subject of an ongoing debate. Since oscillatory EEG activity is increasingly recognized as a fundamental hallmark of cortical integrative functions, this study investigates deviations from the norm of different resting EEG parameters in patients suffering from chronic tinnitus.</p> <p>Results</p> <p>Spectral parameters of resting EEG of male tinnitus patients (n = 8, mean age 54 years) were compared to those of age-matched healthy males (n = 15, mean age 58.8 years). On average, the patient group exhibited higher spectral power over the frequency range of 2-100 Hz. Using LORETA source analysis, the generators of delta, theta, alpha and beta power increases were localized dominantly to left auditory (Brodmann Areas (BA) 41,42, 22), temporo-parietal, insular posterior, cingulate anterior and parahippocampal cortical areas.</p> <p>Conclusions</p> <p>Tinnitus patients show a deviation from the norm of different resting EEG parameters, characterized by an overproduction of resting state delta, theta and beta brain activities, providing further support for the microphysiological and magnetoencephalographic evidence pointing to a thalamocortical dysrhythmic process at the source of tinnitus. These results also provide further confirmation that reciprocal involvements of both auditory and associative/paralimbic areas are essential in the generation of tinnitus.</p

Cortical substrate of bladder control in SCI and the effect of peripheral pudendal stimulation

We investigate (i) the central representation of lower urinary tract (LUT) control and (ii–iii) the acute and 23 short-term central neuromodulatory effect of peripheral pudendal nerve stimulation in incomplete spinal 24 cord injured (SCI) patients using functional magnetic resonance imaging (fMRI). The urinary bladder of eight 25 SCI patients has been passively filled and emptied using a catheter, to identify the neural substrate of bladder 26 control (i), and with simultaneous peripheral pudendal nerve stimulation to investigate its acute central 27 neuromodulatory effect (ii). To identify the potential effects of pudendal nerve stimulation treatment (iii), 28 six patients underwent a 2-week training using pudendal nerve stimulation followed by another fMRI 29 session of bladder filling. The pre- and post-training fMRI results have been compared and correlated with 30 the patient's pre- and post-training urological status. Our results suggest that the central representation of 31 bladder filling sensation is preserved in the subacute stage of incomplete SCI. However, compared to earlier 32 data from healthy subjects, it shows decreased neural response in right prefrontal areas and increased in left 33 prefrontal regions, indicating diminished inhibitory micturition control as well as, compensatory or de- 34 compensatory reorganization of bladder control. We also provide evidence for a neuromodulatory effect of 35 acute pudendal nerve stimulation, which was most prominent in the right posterior insula, a brain region 36 implicated in homeostatic interoception in human. Pudendal stimulation training also induced significant 37 neuromodulation, predominantly signal increases, in the normal cortical network of bladder control. 38 Correlations with the patient's urological status indicate that this neuromodulatory effect may reflect the 39 clinical improvement following training

Neuroplastic Changes in Older Adults Performing Cooperative Hand Movements

The aim of this study was to examine whether older adults use the same task-specific brain activation patterns during two different bimanual hand movement tasks as younger adults. Functional magnetic resonance brain imaging was performed in 18 younger (mean age: 30.3 ± 3.6 years) and 11 older adults (62.6 ± 6.8 years) during the execution of cooperative (mimicking opening a bottle) or non-cooperative (bimanual pro-/supination) hand movements. We expected to see a stronger task-specific involvement of the secondary somatosensory cortex (S2) during cooperative hand movements in older compared to younger adults. However, S2 activation was present in both groups during the cooperative task and was only significantly stronger compared to the non-cooperative task in younger adults. In a whole brain-analysis, the contrast between older and younger adults revealed a hyperactivation of the bilateral dorsal premotor cortex (precentral gyrus), right thalamus, right frontal operculum, anterior cingulate cortex, and supplementary motor areas in older adults (p &lt; 0.001), with some of them being visible after correcting for age. Age was positively associated with fMRI signal changes in these regions across the whole sample. Older adults showed reduced gray matter volume but not in regions showing task-related fMRI group differences. We also found an increase in functional connectivity between SMA, M1, thalamus, and precentral gyri in older adults. In contrast, younger adults showed hyperconnectivity between S2 and S1. We conclude that older compared to younger adults show age-related functional neuroplastic changes in brain regions involved in motor control and performance

Abnormal Resting-State Network Presence in Females with Overactive Bladder

Overactive bladder (OAB) is a global problem reducing the quality of life of patients and increasing the costs of any healthcare system. The etiology of OAB is understudied but likely involves supraspinal network alterations. Here, we characterized supraspinal resting-state functional connectivity in 12 OAB patients and 12 healthy controls (HC) who were younger than 60 years. Independent component analysis showed that OAB patients had a weaker presence of the salience (Cohen's d = 0.9) and default mode network (Cohen's d = 1.1) and weaker directed connectivity between the fronto-parietal network and salience network with a longer lag time compared to HC. A region of interest analysis demonstrated weaker connectivity in OAB compared to HC (Cohen's d > 1.6 or 1.9). The degree of deviation in supraspinal connectivity in OAB patients (relative to HC) appears to be an indicator of the severity of the lower urinary tract symptoms and an indication that such symptoms are directly related to functional supraspinal alterations. Thus, future OAB therapy options should also consider supraspinal targets, while neuroimaging techniques should be given more consideration in the quest for better phenotyping of OAB

Effect of Error Augmentation on Brain Activation and Motor Learning of a Complex Locomotor Task

Up to date, the functional gains obtained after robot-aided gait rehabilitation training are limited. Error augmenting strategies have a great potential to enhance motor learning of simple motor tasks. However, little is known about the effect of these error modulating strategies on complex tasks, such as relearning to walk after a neurologic accident. Additionally, neuroimaging evaluation of brain regions involved in learning processes could provide valuable information on behavioral outcomes. We investigated the effect of robotic training strategies that augment errors—error amplification and random force disturbance—and training without perturbations on brain activation and motor learning of a complex locomotor task. Thirty-four healthy subjects performed the experiment with a robotic stepper (MARCOS) in a 1.5 T MR scanner. The task consisted in tracking a Lissajous figure presented on a display by coordinating the legs in a gait-like movement pattern. Behavioral results showed that training without perturbations enhanced motor learning in initially less skilled subjects, while error amplification benefited better-skilled subjects. Training with error amplification, however, hampered transfer of learning. Randomly disturbing forces induced learning and promoted transfer in all subjects, probably because the unexpected forces increased subjects' attention. Functional MRI revealed main effects of training strategy and skill level during training. A main effect of training strategy was seen in brain regions typically associated with motor control and learning, such as, the basal ganglia, cerebellum, intraparietal sulcus, and angular gyrus. Especially, random disturbance and no perturbation lead to stronger brain activation in similar brain regions than error amplification. Skill-level related effects were observed in the IPS, in parts of the superior parietal lobe (SPL), i.e., precuneus, and temporal cortex. These neuroimaging findings indicate that gait-like motor learning depends on interplay between subcortical, cerebellar, and fronto-parietal brain regions. An interesting observation was the low activation observed in the brain's reward system after training with error amplification compared to training without perturbations. Our results suggest that to enhance learning of a locomotor task, errors should be augmented based on subjects' skill level. The impacts of these strategies on motor learning, brain activation, and motivation in neurological patients need further investigation

Lateral Geniculate Nucleus Volume Determined on MRI Correlates With Corresponding Ganglion Cell Layer Loss in Acquired Human Postgeniculate Lesions

Purpose: To quantitatively assess lateral geniculate nucleus (LGN) volume loss in the presence of lesions in the postgeniculate pathway and its correlation with optical coherence tomography retinal parameters. Methods: This was a case control study of patients recruited at the University Hospital Zurich, Switzerland. Nine patients who were suffering from lesions in the postgeniculate pathway acquired at least 3 months earlier participated. Retinal parameters were analyzed using spectral domain optical coherence tomography and a newly developed magnetic resonance imaging protocol with improved contrast to noise ratio was applied to measure LGN volume. Results: The affected LGN volume in the patients (mean volume 73.89 ± 39.08 mm3) was significantly smaller compared with the contralateral unaffected LGN (mean volume 131.43 ± 12.75 mm3), as well as compared with healthy controls (mean volume 107 ± 24.4 mm3). Additionally, the ganglion cell layer thickness corresponding with the affected versus unaffected side within the patient group differed significantly (mean thickness 40.5 ± 4.11 µm vs 45.7 ± 4.79 µm) compared with other retinal parameters. A significant linear correlation could also be shown between relative LGN volume loss and ganglion cell layer thickness decrease. Conclusions: Corresponding LGN volume reduction could be shown in patients with postgeniculate lesions using a newly developed magnetic resonance imaging protocol. LGN volume decrease correlated with ganglion cell layer thickness reduction as a sign of trans-synaptic retrograde neuronal degeneration

Supraspinal Control of Urine Storage and Micturition in Men—An fMRI Study

Despite the crucial role of the brain in the control of the human lower urinary tract, little is known about the supraspinal mechanisms regulating micturition. To investigate the central regulatory mechanisms activated during micturition initiation and actual micturition, we used an alternating sequence of micturition imitation/imagination, micturition initiation, and actual micturition in 22 healthy males undergoing functional magnetic resonance imaging. Subjects able to micturate (voiders) showed the most prominent supraspinal activity during the final phase of micturition initiation whereas actual micturition was associated with significantly less such activity. Initiation of micturition in voiders induced significant activity in the brainstem (periaqueductal gray, pons), insula, thalamus, prefrontal cortex, parietal operculum and cingulate cortex with significant functional connectivity between the forebrain and parietal operculum. Subjects unable to micturate (nonvoiders) showed less robust activation during initiation of micturition, with activity in the forebrain and brainstem particularly lacking. Our findings suggest that micturition is controlled by a specific supraspinal network which is essential for the voluntary initiation of micturition. Once this network triggers the bulbospinal micturition reflex via brainstem centers, micturition continues automatically without further supraspinal input. Unsuccessful micturition is characterized by a failure to activate the periaqueductal gray and pons during initiatio

Occipital transcranial direct current stimulation in episodic migraine patients: effect on cerebral perfusion

Cerebral blood flow differs between migraine patients and healthy controls during attack and the interictal period. This study compares the brain perfusion of episodic migraine patients and healthy controls and investigates the influence of anodal transcranial direct current stimulation (tDCS) over the occipital cortex. We included healthy adult controls and episodic migraineurs. After a 28-day baseline period and the baseline visit, migraine patients received daily active or sham anodal tDCS over the occipital lobe for 28 days. All participants underwent a MRI scan at baseline; migraineurs were also scanned shortly after the stimulation period and about five months later. At baseline, brain perfusion of migraine patients and controls differed in several areas; among the stimulated areas, perfusion was increased in the cuneus of healthy controls. At the first visit, the active tDCS group had an increased blood flow in regions processing visual stimuli and a decreased perfusion in other areas. Perfusion did not differ at the second follow-up visit. The lower perfusion level in migraineurs in the cuneus indicates a lower preactivation level. Anodal tDCS over the occipital cortex increases perfusion of several areas shortly after the stimulation period, but not 5 months later. An increase in the cortical preactivation level could mediate the transient reduction of the migraine frequency.Trial registration: NCT03237754 (registered at clincicaltrials.gov; full date of first trial registration: 03/08/2017)