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08 juni 2023, Contains fulltext : 296367.pdf (Publisher’s version ) (Closed access), Objective: To evaluate whether cognitive and motor therapy (CMT) is more effective than no therapy, motor therapy, or cognitive therapy on motor and/or cognitive outcomes after stroke. Additionally, this study evaluates whether effects are lasting and which CMT approach is most effective. Data Sources AMED, EMBASE, MEDLINE/PubMed, and PsycINFO databases were searched in October 2022. Study Selection: Twenty-six studies fulfilled the inclusion criteria: randomized controlled trials published in peer-reviewed journals since 2010 that investigated adults with stroke, delivered CMT, and included at least 1 motor, cognitive, or cognitive-motor outcome. Two CMT approaches exist: CMT dual-task ("classical" dual-task where the secondary cognitive task has a distinct goal) and CMT integrated (where cognitive components of the task are integrated into the motor task). Data Extraction: Data on study design, participant characteristics, interventions, outcome measures (cognitive/motor/cognitive-motor), results and statistical analysis were extracted. Multilevel random effects meta-analysis was conducted. Data Synthesis: CMT demonstrated positive effects compared with no therapy on motor outcomes (g=0.49; 95% confidence interval [CI], 0.10, 0.88) and cognitive-motor outcomes (g=0.29; 95% CI, 0.03, 0.54). CMT showed no significant effects compared with motor therapy on motor, cognitive, and cognitive-motor outcomes. A small positive effect of CMT compared with cognitive therapy on cognitive outcomes (g=0.18; 95% CI, 0.01, 0.36) was found. CMT demonstrated no follow-up effect compared with motor therapy (g=0.07; 95% CI, -0.04, 0.18). Comparison of CMT dual-task and integrated revealed no significant difference for motor (F1,141=0.80; P=.371) or cognitive outcomes (F1,72=0.61, P=.439). Conclusions: CMT was not superior to monotherapies in improved outcomes after stroke. CMT approaches were equally effective, suggesting that training that enlists a cognitive load per se may benefit

Item does not contain fulltext, We investigated the role of contextual knowledge in defensive responses to visual stimuli (spiders and butterflies) looming toward the hand. Human participants responded to tactile stimuli delivered to the same hand at 6 possible locations during an insect's approach. Tactile reaction times were faster when looming stimuli were closer to the hand, especially for spiders, and faster when insects loomed on a collision path than on a near-miss path. This latter finding suggests that human reactions to looming stimuli are not merely automatic reflexes but that contextual knowledge about the trajectory of looming objects is included in predicting their impact.

Item does not contain fulltext, Our daily living includes bodily contacts with objects and people. While this physical contact occurs naturally, it could also pose a risk of bodily harm - for example, when objects are sharp, or people have bad intentions. It is therefore imperative to have a mechanism that predicts the consequences of bodily contact before it occurs, to guide our interactions appropriately. Evidence from a range of studies suggests a neurofunctional coupling between external visual or auditory stimuli near the body and tactile stimuli on the body. While these multisensory peripersonal representations have been linked to spatial attention, motor control, and social behaviour, a discussion on whether these functions involve a similar mechanism has been missing. Here we suggest that prediction is central to this multimodal coding: visual or auditory stimuli near the body predict tactile consequences of bodily contact. This predictive mechanism is based on learned visuo-tactile associations and modulated by higher-order visual contextual information.

thesis Individualized functional mapping before epilepsy surgery is important, as the localization of function is variable among patients and may be influenced by epilepsy. The “golden standard” in testing language lateralization is the Wada test. During this procedure a major part of a hemisphere is temporarily inactivated. We can therefore expect contralateral hemiparesis and often (incomplete) hemianopia. Patients may not recall this hemiparesis when asked a few minutes after the test. The denial or inability to recognize the presence of such a major physical impairment can be seen as a form of anosognosia. The underlying mechanism for such anosognosia, lasting up to a few minutes after hemispheric anesthesia during the Wada test, has not been studied. The current study will investigate how often a patient, a few minutes after the Wada injection, is not aware of an inability during the test and if this anosognosia can be profiled. We expect that anosognosia will occur when the non-language-dominant hemisphere is anesthetized and the patient has a pre-existing deficit in executive functioning. In addition to testing this hypothesis, explorative research will also be conducted to see if there are multiple remarkable observations to form new hypotheses in the future. Video recordings of the Wada tests were reviewed. Symptoms of anosognosia was present in 70% of the cases. We could not find an association between a range of presumed predictive variables and the occurrence of anosognosia. Only a trend for male sex is found.

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Item does not contain fulltext, The somatosensory system is important for many functions, such as tactile recognition, the perception of our body, and motor actions. We present a comprehensive review of the human and animal literature on somatosensory processing over the past 10 years and evaluate how well existing models can accommodate the new observations. Based on these observations and a survey of the brain structures involved in somatosensation, we suggest that a new model is needed that describes multiple networks involved in separate subfunctions. These networks are highly interconnected and often multimodal in nature. The model includes basic somatosensory processing and five higher-order networks involved in haptic object recognition and memory, body perception, body ownership, affective processing, and action.

Item does not contain fulltext, In 'split-brain' patients, the corpus callosum has been surgically severed to alleviate medically intractable, severe epilepsy. The classic claim is that after removal of the corpus callosum an object presented in the right visual field will be identified correctly verbally and with the right hand but not with the left hand. When the object is presented in the left visual field the patient verbally states that he saw nothing but nevertheless identifies it accurately with the left hand. This interaction suggests that perception, recognition and responding are separated in the two isolated hemispheres. However, there is now accumulating evidence that this interaction is not absolute. Recently, we (Pinto et al., 2017) showed that accurate detection and location of stimuli anywhere in the visual field could be performed with both hands. In this study, we explored detection and localisation of tactile stimulation on the body. In line with our previous results, we observed that split-brain patients can signal detection and localisation with either hand anywhere on the body (be it the arm or the leg) but they remain unable to match positions touched on both arms or legs simultaneously. These results add to the evidence suggesting that the effects of removal of the corpus callosum may be less severe than sometimes claimed.

Contains fulltext : 208235.pdf (publisher's version ) (Open Access), This study uses electrocorticography in humans to assess how alpha- and beta-band rhythms modulate excitability of the sensorimotor cortex during psychophysically-controlled movement imagery. Both rhythms displayed effector-specific modulations, tracked spectral markers of action potentials in the local neuronal population, and showed spatially systematic phase relationships (traveling waves). Yet, alpha- and beta-band rhythms differed in their anatomical and functional properties, were weakly correlated, and traveled along opposite directions across the sensorimotor cortex. Increased alpha-band power in the somatosensory cortex ipsilateral to the selected arm was associated with spatially-unspecific inhibition. Decreased beta-band power over contralateral motor cortex was associated with a focal shift from relative inhibition to excitation. These observations indicate the relevance of both inhibition and disinhibition mechanisms for precise spatiotemporal coordination of movement-related neuronal populations, and illustrate how those mechanisms are implemented through the substantially different neurophysiological properties of sensorimotor alpha- and beta-band rhythms.

As key element of executive function, cognitive flexibility incorporates multiple component processes, enabling adaptation in response to a constantly changing environment. Preserving cognitive flexibility during surgical resection of a low-grade glioma is of great importance to maintain quality of life and recover optimally from this life event. Dysconnectivity within the fronto-parieto-temporal network of the right parietal lobe has previously been linked to cognitive flexibility deficits, suggesting white matter involvement. To further explore the involvement of white matter in cognitive flexibility, a multicentred international collaboration was established. Nineteen patients, who underwent surgical resection for a low-grade glioma in the right parietal lobe, were assessed pre- and post-surgery, using the Trail Making Test and Stroop-Color-Word-Test to administer cognitive flexibility. Volume measurements and lesion-symptom mapping analyses were performed on postoperative MRI scans. Results showed that the Superior Longitudinal Fasciculus III (SLF III), Arcuate Fasciculus (AF) and Inferior Fronto-Occipital Fasciculus (IFOF) were damaged in both cognitively declined patients (n=4) and cognitively non-declined patients (n=15). Tractographic resection simulations presented similar patterns of dysconnectivity in the right parietal lobe in both groups. In addition, a greater extent of resection was not linked to a decline in cognitive flexibility after surgery. Our findings neither confirm nor deny the proposed involvement of the SLF III, AF and IFOF in cognitive flexibility. Yet, it is clear that cognitive inflexibility is not related to the extent of resection. The integration of DTI and intraoperative monitoring in standard clinical practice is needed for localization and comprehension of cognitive outcomes after neurosurgery.

Contains fulltext : 198719.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 175191.pdf (Publisher’s version ) (Open Access)

RU Radboud Universiteit, 10 juni 2016, Promotores : Toni, I., Dijkerman, H.C. Co-promotores : Lange, F.P. de, Stolk, A., Contains fulltext : 157004.pdf (publisher's version ) (Open Access)

Our cognition interacts continuously with the environment, which is for example shown by effects of prism adaptation. Recently, two studies found out that pointing to one side of the visual field produces similar alterations as prism adaptation in pointing straight ahead and a local/global processing task, an attentional process which is strongly lateralized in the brain. Current study examined the effects of this so called lateralized pointing (LP) on spatial relation processing, which also has a strong lateralization pattern. Categorical relations are mainly processed in the left hemisphere and the right hemisphere is primarily involved with coordinate processing. Therefore, it was hypothesized that right LP improves performance on a categorical task and left LP improves performance on a coordinate task. Students from Utrecht University performed a cross-dot task both before and after LP. In order to control for possible effects of tiredness or practice, some participants performed the cross-dot task twice, but without intermediate pointing. Results showed that regardless of pointing direction, performance on the categorical task improved as a result of LP, while coordinate processing did not differ as a result of LP. Given these results, it is likely that the left hemisphere is activated as a result of a sensorimotor process which consequently activated left superior parietal lobe, rather than an attentional bias to one side of the visual field.

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Contains fulltext : 143349.pdf (publisher's version ) (Closed access), Objectives: Prior research suggests that dampening neural activity of the intact, presumably overactive hemisphere, combined with increasing neural activity in the damaged hemisphere, might restore cortical interhemispheric balance and reduce neglect. In the present study we repeatedly applied a relatively new technique, transcranial direct current stimulation (tDCS), to the posterior parietal cortex to modulate spontaneous neural activity levels in a polarity dependent fashion to find evidence for improvements in severe hemispatial neglect in chronic patients. Methods: Eighty-nine patients were initially identified from our databases as having neglect, after thoroughly screening databases, consulting medical practitioners and baseline testing, only five met our inclusion criteria and agreed to participate. Sixty-five patients were excluded as they did not meet safety criteria for tDCS (epilepsy, metal implants), suffered from other medical conditions (i.e., heart disease, epilepsy, current psychiatric disorder) or displayed only mild neglect at baseline testing. Five patients with severe chronic hemispatial neglect were enrolled in a double-blind, placebo-controlled treatment program. TDCS or placebo was applied for 20 minutes over the left (cathodal) and right (anodal) posterior parietal cortex at an intensity of 2 mA on five consecutive days. Treatment conditions were separated by a four week wash-out period. Baseline corrected change in performance on the conventional subtests of the Behavioral Inattention Test (BIT) was our primary endpoint. Results: No treatment-related effects were observed for the BIT change scores and performance on individual subtests. Moreover, patients' performance somewhat improved only during the stimulation period (day one vs day five, irrespective of whether it was placebo or tDCS), but not thirty days later, indicating a practice effect. Discussion: The present study does not provide evidence that tDCS to the posterior parietal cort

Contains fulltext : 135378.pdf (publisher's version ) (Open Access), Rhythmic neural activity within the alpha (8-12 Hz) and beta (15-25 Hz) frequency bands is modulated during actual and imagined movements. Changes in these rhythms provide a mechanism to select relevant neuronal populations, although the relative contributions of these rhythms remain unclear. Here we use MEG to investigate changes in oscillatory power while healthy human participants imagined grasping a cylinder oriented at different angles. This paradigm allowed us to study the neural signals involved in the simulation of a movement in the absence of signals related to motor execution and sensory reafference. Movement selection demands were manipulated by exploiting the fact that some object orientations evoke consistent grasping movements, whereas others are compatible with both overhand and underhand grasping. By modulating task demands, we show a functional dissociation of the alpha- and beta-band rhythms. As movement selection demands increased, alpha-band oscillatory power increased in the sensorimotor cortex ipsilateral to the arm used for imagery, whereas beta-band power concurrently decreased in the contralateral sensorimotor cortex. The same pattern emerged when motor imagery trials were compared with a control condition, providing converging evidence for the functional dissociation of the two rhythms. These observations call for a re-evaluation of the role of sensorimotor rhythms. We propose that neural oscillations in the alpha-band mediate the allocation of computational resources by disengaging task-irrelevant cortical regions. In contrast, the reduction of neural oscillations in the beta-band is directly related to the disinhibition of neuronal populations involved in the computations of movement parameters.

(Laymen) Abstract: Echolocation is the ability to locate the objects and creatures around you by means of interpreting the reflected echoes, of sounds that bounce off of them. Human echolocation is a technique useable by any human, but most notably by the blind and visually impaired. The technique is similar to echolocation used by bats and dolphins, which use it to navigate in total darkness and under water. There are two different forms of echolocation: active and passive. Actively producing sounds in order to receive localization information from the reflected echoes, is known as active echolocation. Passive echolocation is the interpretation of reflected echoes from sounds produced by your surroundings. Most blind and visually impaired already use some of the aspects of passive echolocation unconsciously. Active echolocation however, needs to be taught, just like the use of a cane. A trained echolocator can use echolocation to navigate his surroundings far beyond the reach of his cane and identify objects and people as if sighted. The use of this technique requires sensitivity and rapid analysis of the properties of both self- generated sounds and its echoes, as well as the sounds and echoes produced by the surroundings. The possibilities and impossibilities, together with the known teaching methods of human echolocation are described and reviewed in detail, to better understand the influence recent research might have on teaching the technique. FMRI analysis shows that trained echolocators, when presented with pre-recorded self-generated sounds and their echoes, have increased activation in brain areas associated with visual processing, most notably in the primary visual cortex (or calcarine cortex), as if they create a mental image. The accuracy, detection limits and abilities to identify objects with human echolocation have also been investigated and studies on these subjects will be reviewed here as well. Research in echolocating animals is also of considera