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Sir,We would like to make a few comments on the interesting paper recently published in Brain by Karnath et al. (2011). We were impressed by the careful assessment of spatial neglect during acute and chronic phase, which was combined with a solid voxel-wise lesion symptom mapping technique in a series of 54 patients with right-hemisphere stroke. Anatomical data indicated that lesions in the superior and middle temporal gyri, the basal ganglia, as well as the inferior occipitofrontal fasciculus are responsible for spatial neglect in both acute and chronic phases.We also had the opportunity to evaluate 69 patients with right brain lesions longitudinally. Our patients were admitted after a first right-hemisphere stroke (mean delay: 7.5 AE 14.6 days), at a mean age of 64.95 AE 14.6 years. Mean delay between the acute and chronic phase was 350.21 AE 184.7 days. These demographic data are comparable with the patients of Karnath et al. (2011). Neglect was considered as present when patients failed at least two out of eight tests (Table 1)-unlike diagnoses based on two out three tests in Karnath et al. (2011). In the acute phase, 31 patients had neglect (45%). In the chronic phase, 17 of these 31 neglect patients still showed a significant impairment (55%). Using the same voxel-wise lesion mapping as Karnath et al. (2011), we found partly different results, particularly in the acute phase (detailed below). However, we believe that major differences in the findings may depend on the clinical measures used to define neglect, since this syndrome may include heterogeneous symptoms.

Recent findings indicate that synchronous neural activity at rest influences human performance in subsequent tasks. Synchronization can occur in form of phase coupling or amplitude correlation. It is unknown whether these coupling types have differing behavioral significance at rest. To address this, we performed resting-state electroencephalography (EEG) and source connectivity analysis in several populations of healthy subjects and patients with brain lesions. We systematically compared different types and frequencies of neural synchronization and investigated their association with behavioral performance in verbal and spatial attention tasks. Behavioral performance could be consistently predicted by two distinct resting-state coupling patterns: (1) amplitude envelope correlation of beta activity between homologous areas of both hemispheres, (2) lagged phase synchronization in EEG alpha activity between a brain area and the entire cortex. A disruption of these coupling patterns was also associated with neurological deficits in patients with stroke lesions. This suggests the existence of two distinct network systems responsible for resting-state integration. Lagged phase synchronization in the alpha band is associated with global interaction across networks while amplitude envelope correlation seems to be behaviorally relevant for interactions within networks and between hemispheres. These two coupling types may therefore provide complementary insights on brain physiology and pathology.

Previous research suggests that people construct mental time lines to represent and reason about time. However, is the ability to represent space truly necessary for representing events along a mental time line? Our results are the first to demonstrate that deficits in spatial representation (as a function of left hemispatial neglect) also result in deficits in representing events along the mental time line. Specifically, we show that patients with left hemispatial neglect have difficulty representing events that are associated with the past and, thus, fall to the left on the mental time line. These results demonstrate that representations of space and time share neural underpinnings and that representations of time have specific spatial properties (e.g., a left and a right side). Furthermore, it appears that intact spatial representations are necessary for at least some types of temporal representation.

Background and Purpose-To evaluate the effect of prism adaptation (PA) on spatial neglect signs. Methods-Ten patients (hemianopia in 6) and 8 control subjects were included. Tasks were reading single words, nonwords, and a text, bell cancellation, line bisection, and scene drawing, before and after adaptation, with either deviating or neutral prisms. Results-Errors were more frequent in patients but without any specific effect of PA. We found partial improvement at the late sessions, independent of prisms. Conclusions-We did not confirm the efficacy of PA on spatial neglect. (Stroke. 2006;37:542-543.)

We propose a comprehensive statistical approach describing the penetration depth of light in random media. The presented theory exploits the concept of probability density function f(z|ρ, t) for the maximum depth reached by the photons that are eventually re-emitted from the surface of the medium at distance ρ and time t. Analytical formulas for f, for the mean maximum depth 〈z max 〉 and for the mean average depth z reached by the detected photons at the surface of a diffusive slab are derived within the framework of the diffusion approximation to the radiative transfer equation, both in the time domain and the continuous wave domain. Validation of the theory by means of comparisons with Monte Carlo simulations is also presented. The results are of interest for many research fields such as biomedical optics, advanced microscopy and disordered photonics.

We tested whether human amygdala lesions impair vocal processing in intact cortical networks. In two functional MRI experiments, patients with unilateral amygdala resection either listened to voices and nonvocal sounds or heard binaural vocalizations with attention directed toward or away from emotional information on one side. In experiment 1, all patients showed reduced activation to voices in the ipsilesional auditory cortex. In experiment 2, emotional voices evoked increased activity in both the auditory cortex and the intact amygdala for right-damaged patients, whereas no such effects were found for left-damaged amygdala patients. Furthermore, the left inferior frontal cortex was functionally connected with the intact amygdala in right-damaged patients, but only with homologous right frontal areas and not with the amygdala in left-damaged patients. Thus, unilateral amygdala damage leads to globally reduced ipsilesional cortical voice processing, but only left amygdala lesions are sufficient to suppress the enhanced auditory cortical processing of vocal emotions.

This study evidenced a cortical dissociation for body-centered and gravitational representations biases, which may reflect the differential involvement of these brain regions in spatial information processing. The lesions involved in representation biases (especially of the SV) and postural difficulties overlapped to some extent in the temporoparietal, superior temporal, and posterior insular regions of the cortex.