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Abstract: Macro- and micro-somatognosia refer to rare disorders of the cerebral representation of the body whereby patients perceive body parts as disproportionately large or small. Here we report the experimental study of a patient who, following a left lateral medullary stroke (Wallenberg''s syndrome, including vestibular deficits) complained of a persistent somatosensory illusory sensation of swelling, confined to the left side of his face (i.e., left macrosomatognosia). This hemifacial somatosensory distortion was associated with a left facial anesthesia, and a neuropathic pain affecting the three branches of the left trigeminal nerve. In this study, we first document quantitatively the patient''s somatosensory illusion by using a somatosensory-to-visual matching task in which the patient modified the picture of his own face to fit his left-sided somatosensory misperception. The patient''s performance revealed that macrosomatognosia was confined to the second branch of the left trigeminal nerve. Perception of the size of visual objects was comparatively preserved. Second, we investigated the effects of two peripheral stimulations, which may affect the spatial component of somatosensory deficits (caloric vestibular stimulation, CVS; transcutaneous electrical nervous stimulation, TENS) and pain (TENS). Left CVS abolished the facial somatosensory illusion, for about 30min, but had no effect on the left facial pain. Conversely, left TENS substantially reduced the neuropathic pain during stimulation, but had no effect on macrosomatognosia, indicating a double dissociation between the two disorders. These results reveal that facial macrosomatognosia may be regarded as a high-order deficit of somatosensory perception of the shape and volume of the face, which fits the definition of ‘hyperschematia’ (i.e., when the body takes up too much room) originally proposed by . Our data also indicate that CVS may favor the restoration of the conscious representation of the shape and size of the face. Overall, these findings lend support to the view that afferent inputs from the vestibular system can affect in a specific fashion the activity of cerebral structures involved in the building up and updating of the topological description of body parts. [Copyright &y& Elsevier]

Abstract: Vocabulary acquisition is such a major aspect of language learning in children, but also in adults when learning a foreign language, that a dedicated vocabulary learning device may exist within the language organ. To identify the relevant brain systems, we performed regional cerebral blood flow measurements in normal subjects while they were learning a list of neologisms or a list of word–nonword pairs. Structures implicated in phonological short-term memory (Broca''s area, left temporo-parietal junction) were steadily activated during nonwords learning, while the left temporal lobe neocortical and paralimbic structures (parahippocampal region), associated with long-term memory, contributed to learning in a time-dependent manner, with maximal activation at the beginning of the process. The neural system specifically activated when learning new vocabulary was strongly lateralized to the left hemisphere. This evidence refines current models of memory function and supports theories which emphasise the importance of phonological competence in hemispheric dominance for language. [Copyright &y& Elsevier]

One possible pathological mechanism underlying the rightward bisection error of right- brain-damaged patients with left spatial neglect is a leftward relaxation of the spatial representational medium. This view was originally based on the finding that patients with left neglect, required to extend horizontal segments, in order to double their original length, may exhibit a relative left overextension of the drawn lines (Bisiach et al., 1994). We investigated this putative distortion of representational space using a 16cm line segmentation' task (Experiment I). Were the representation of space relaxed contralesionally, a progressive increase from right to left of the size of the drawn segments would be expected. Right-brain-damaged patients with left unilateral neglect (N = 12) performed the segmentation task with no left versus right differences, as right-brain-damaged patients without neglect (N = 8), and neurologically unimpaired control subjects (N = 10), did. Experiments 2 and 3 explored the effects of sample length (1, 2, 4, and 8cm), by which the 16cm lines had to be segmented. Neglect patients produced longer left-sided segments only for the 8cm sample (i.e. half of the length of the segment). This set of experiments suggests an impairment in the segmentation task only with the larger (8cm) sample, when a more global level of processing may be involved. Experiment 4 assessed this hypothesis by a part/whole' bisection task, using 8cm lines, presented either embedded in a longer 16cm line or in isolation. Neglect patients made a larger rightward bisection error when the segment was not embedded. The suggestion is made that the lateral distortion of the representation of space in neglect patients (i.e. a leftward relaxation of the spatial medium) concerns tasks where a more 'global' representation of the visual stimulus has to be set up. The different demands of the segmentation and bisection tasks are discussed. [ABSTRACT FROM AUTHOR]

Background and purpose: Neuromodulation is a promising approach to increasing motor recovery in stroke; however, to date, there is a scarcity of evidence documenting the clinical potential of transcranial direct current stimulation (tDCS) administered in the acute phase of stroke. The present study aims to examine the clinical effects of a treatment involving the application of tDCS in the acute stage post‐stroke. Methods: This was a randomized, double‐blind, sham‐controlled trial. A cohort of 32 stroke patients with severe motor impairment underwent 5 days of treatment with real or sham bi‐hemispheric tDCS over the motor cortex. During the treatment, tDCS was applied twice per day (two daily applications each of 15 min), starting 48 to 72 h after stroke onset. Results: We found statistically significant improvements after both real and sham tDCS treatments in primary (hand grip strength, Motricity Index) and secondary (National Institutes of Health Stroke Scale score, Barthel Index) outcomes. Patients receiving real tDCS showed a larger improvement of upper‐limb muscle strength at the end of treatment phase; this advantage was no longer present after 6 months. Conclusions: Transcranial direct current stimulation may be used to accelerate the rate of upper‐limb motor recovery during the spontaneous recovery period. [ABSTRACT FROM AUTHOR]

Introduction Motor execution, planning, and learning are altered by transcranial Direct Current Stimulation (tDCS). The potential of this technique for modulating action monitoring and awareness has not been explored so far. Optimal motor control relies on internal representations of the intended, predicted, and actual action. The brain is equipped with a “comparator” system, which monitors and detects the congruence between planned and performed movements; based on this comparison motor awareness is constructed. Objectives The study aimed at disrupting motor monitoring and awareness through the neuromodulation of the activity of the Premotor (PMC) and Posterior Parietal (PPC) cortices of the right hemisphere. Methods Real or sham cathodal tDCS (1.5 mA, 6 min) were applied over the right PMC or PPC in 22 healthy participants (8 right-handed men, mean age = 25.5 years). Before and after tDCS, participants performed a 2-digit sequence motor task and rated how well they had executed it on a 5-item questionnaire (Motor Performance Awareness Questionnaire – MPAQ). During the task performed after tDCS, online single-pulse Transcranial Magnetic Stimulation (sTMS) was applied to the right primary motor cortex (M1), contralateral to the executing left hand, with the aim of evoking involuntary muscles twitches, interfering with motor execution. Results Cathodal tDCS to PMC (but not sham tDCS or PPC tDCS) impaired motor monitoring, making participants unconfident about their explicit judgments on their motor performance (MPAQ, tDCS by Time interaction, F = 3.74, pr = .59, p = .004) and PPC ( r = .69, p = .001) tDCS, but not after PMC tDCS ( r = .22, p = .32). Conclusion Cathodal tDCS to the right PMC disrupts the participants’ ability to evaluate their motor performance reliably, disrupting self-confidence about own motor performance and also the ability to detect the discrepancy between their planned and performed movements . [ABSTRACT FROM AUTHOR]

A quantitative assessment of a distortion involving the left side of space, both in two-dimensional (drawing), and three-dimensional (modeling), visuo-constructional tasks is reported in a patient with a right temporoparieto-occipital lesion, and left hemianopia, without visuospatial neglect. In drawing and clay modeling of objects the patient exhibited a disproportionate enlargement of the left-hand side of objects. Matching perceptually two rectangles, the patient underestimated the left side of the stimulus. In a visuomotor task requiring the reproduction of horizontal extent, the patient exhibited a leftward overextension. Observations in two right-brain-damaged patients by Rode, Michel, Rossetti, Boisson, and Vallar (2006, Neurology, 67, 1801) are confirmed and extended. The patient's impairment may involve a disordered representation of extrapersonal space, with a leftward disproportionate expansion of the spatial medium ('hyperschematia'). Accordingly, symmetrical productions are compensatorily expanded leftwards, and the left sides of objects are perceived as smaller in horizontal extent. The disorder is largely independent of left spatial neglect. [ABSTRACT FROM AUTHOR]

In everyday life, the successful monitoring of behavior requirescontinuous updating of the effectiveness of motor acts; one crucial stepis becoming aware of the movements one is performing. We studied theanatomical distribution of lesions in right-brain-damaged hemiplegicpatients, who obstinately denied their motor impairment, claiming thatthey could move their paralyzed limbs. Denial was associated withlesions in areas related to the programming of motor acts, particularlyBrodmann's premotor areas 6 and 44, motor area 4, and the somatosensorycortex. This association suggests that monitoring systems may beimplemented within the same cortical network that is responsible for theprimary function that has to be monitored. [ABSTRACT FROM AUTHOR]

Prism adaptation improves visual and haptic manifestations of left neglect, and can induce a small but reliable simulation of left visual neglect in normal individuals. Here, we present two experiments in which the effects of prism adaptation on the representation of space were explored. In Experiment 1, normal subjects were required to locate the centre of a haptically explored circle, before and after adaptation to leftward displacing prisms. In Experiment 2, a visual circle centring task was used. In both tasks, prism adaptation induced a significant rightward shift of performance. In addition, in both experiments, three classical measures of visuo-manual adaptation were taken: the visual shift, the proprioceptive shift and the total shift. The effects found on the haptic and visual tasks did not correlate with any of these measures. This suggests that the effects of prism adaptation on the circle centring tasks did not depend directly on the sensorimotor consequences of the adaptation. These results imply that prism adaptation can affect noetic levels of space representation in normal subjects, supporting the hypothesis that this low-level sensorimotor intervention can exert a bottom-up structuring influence on higher levels of cognitive integration. [Copyright &y& Elsevier]

Introduction In the last decade, transcranial direct current stimulation (tDCS) has been increasingly used in experimental and clinical settings. Nevertheless, its neurophysiological underpinnings still remain unclear. Moreover, under debate is how and to what extent these effect spread through brain pathways. Objectives In this study, we explored local and global cortical excitability and time–frequency modulation after active and sham tDCS by means of an integrated Transcranial Magnetic Stimulation and Electroencephalography (TMS-EEG) system. Materials and methods Fourteen healthy subjects took part in the experiment. Single pulse TMS was delivered over the left posterior parietal cortex (PPC), before, and after 15 min of anodal tDCS over the right PPC. 180 trials was delivered in each session, while EEG was concurrently recorded from 60 channels. Six subjects performed an additional session receiving sham tDCS. For each session, indexes of global and local cerebral excitability were obtained, computed as global and local mean field power (GMFP and LMFP) on mean TMS-evoked potentials (TEPs). LMFP were computed in six clusters of electrodes placed over the left and right frontal, parietal and temporal regions. Additionally, source analysis was performed computing Significant Current Density both globally and locally on Brodmann areas 6, 7 and 21. Moreover, we computed and index for Current Spread, to estimate where the current peak occurred in the pre and post stimulation conditions. Finally, time–frequency analyses were run to investigate how the natural frequencies of the stimulated area were affected by tDCS. Results Concerning results recorded at the sensor level, GMFP increased, compared to baseline, after active tDCS, while no difference was found between pre and post sham tDCS. LMFP increased after the end of stimulation in parietal and frontal clusters bilaterally, while no difference was found in the temporal clusters. Source modeling confirmed GMFP and LMFP results. Frontal and parietal regions (namely BA 6 and 7) increased in cortical current density after real tDCS. Conclusion Anodal tDCS induces a widespread increase of cortical excitability, both during and after the end of the stimulation, modulating a fronto-parietal network, likely following structural connections. [ABSTRACT FROM AUTHOR]