Electrophysiological signatures of resting state networks predict cognitive deficits in stroke.

Localized damage to different brain regions can cause specific cognitive deficits. However, stroke lesions can also induce modifications in the functional connectivity of intrinsic brain networks, which could be responsible for the behavioral impairment. Though resting state networks (RSNs) are typically mapped using fMRI, it has been recently shown that they can also be detected from high-density EEG. We build on a state-of-the-art approach to extract RSNs from 64-channels EEG activity in a group of right stroke patients and to identify neural predictors of their cognitive performance. Fourteen RSNs previously found in fMRI and high-density EEG studies on healthy participants were successfully reconstructed from our patients' EEG recordings. We then correlated EEG-RSNs functional connectivity with neuropsychological scores, first considering a wide frequency band (1-80 Hz) and then specific frequency ranges in order to examine the association between each EEG rhythm and the behavioral impairment. We found that visuo-spatial and motor impairments were primarily associated with the dorsal attention network, with contribution dependent on the specific EEG band. These findings are in line with the hypothesis that there is a core system of brain networks involved in specific cognitive domains. Moreover, our results pave the way for low-cost EEG-based monitoring of intrinsic brain networks' functioning in neurological patients to complement clinical-behavioral measures.

Ipsilesional Impairments of Visual Awareness After Right-Hemispheric Stroke.

Unilateral brain damage following stroke frequently hampers the processing of contralesional space. Whether and how it also affects the processing of stimuli appearing on the same side of the lesion is still poorly understood. Three main alternative hypotheses have been proposed, namely that ipsilesional processing is functionally (i) hyperefficient, (ii) impaired, or (iii) spared. Here, we investigated ipsilesional space awareness through a computerized paradigm that exploits a manipulation of concurrent information processing demands (i.e., multitasking). Twelve chronic right-hemisphere stroke patients with a total lack of awareness for the contralesional side of space were administered a task that required the spatial monitoring of two locations within the ipsilesional hemispace. Targets were presented immediately to the right of a central fixation point (3° eccentricity), or farther to the right toward the screen edge (17° eccentricity), or on both locations. Response to target position occurred either in isolation or while performing a concurrent visual or auditory task. Results showed that most errors occurred when two targets were simultaneously presented and patients were faced with additional task demands (in the visual or auditory modalities). In the context of concurrent visual load, ipsilesional targets presented at the rightmost location were omitted more frequently than those presented closer to fixation. This pattern qualifies ipsilesional processing in right-hemisphere stroke patients as functionally impaired, arguing against the notion of ipsilesional hyperperformance, especially when under visual load.

Conventional and functional assessment of spatial neglect: Clinical practice suggestions.

OBJECTIVE: Spatial neglect (SN) constitutes a substantial barrier to functional recovery after acquired brain injury. However, because of its multimodal nature, no single test can capture all the signs of SN. To provide a clinically feasible solution, we used conventional neuropsychological tests as well as the Catherine Bergego Scale (CBS) via the Kessler Foundation Neglect Assessment Process (KF-NAP). The goal was to add evidence that a global approach should detect better even subtle signs of SN. METHOD: Fourteen individuals with lesions located in the right cerebral hemisphere participated in the study. Participants were assessed with a comprehensive battery of neuropsychological tests, comprising a set of visuospatial tests to evaluate several spatial domains. In addition, patients underwent functional assessment with the Barthel Index, the Functional Independence Measure (FIM), and the CBS via KF-NAP. RESULTS: The CBS via KF-NAP was associated with the visuospatial paper-based tests (p = .004) as well as the Motor FIM (p = .003), and was more sensitive than the Behavioral Inattention Test-Conventional in detecting SN (p = .014). CONCLUSIONS: We showed that the CBS via KF-NAP was able: (a) to detect functional impairment, especially motor, related to SN; (b) to selectively measures spatial rather than nonspatial dysfunctions; and (c) to be highly sensitive in detecting SN signs especially in those patients with mild severity, covering several aspects of SN manifestations. The patient's SN diagnosis based on the CBS via KF-NAP is clinically important and directly relevant to care planning and goal setting. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Zero in the brain: A voxel-based lesion-symptom mapping study in right hemisphere damaged patients.

Transcoding numerals containing zero is more problematic than transcoding numbers formed by non-zero digits. However, it is currently unknown whether this is due to zeros requiring brain areas other than those traditionally associated with number representation. Here we hypothesize that transcoding zeros entails visuo-spatial and integrative processes typically associated with the right hemisphere. The investigation involved 22 right-brain-damaged patients and 20 healthy controls who completed tests of reading and writing Arabic numbers. As expected, the most significant deficit among patients involved a failure to cope with zeros. Moreover, a voxel-based lesion-symptom mapping (VLSM) analysis showed that the most common zero-errors were maximally associated to the right insula which was previously related to sensorimotor integration, attention, and response selection, yet for the first time linked to transcoding processes. Error categories involving other digits corresponded to the so-called Neglect errors, which however, constituted only about 10% of the total reading and 3% of the writing mistakes made by the patients. We argue that damage to the right hemisphere impairs the mechanism of parsing, and the ability to set-up empty-slot structures required for processing zeros in complex numbers; moreover, we suggest that the brain areas located in proximity to the right insula play a role in the integration of the information resulting from the temporary application of transcoding procedures.

Right-hemisphere (spatial?) acalculia and the influence of neglect.

The present study aimed at exploring basic number and calculation abilities in right-hemisphere damaged patients (RHD), focusing primarily on one-digit orally presented tasks, which do not require explicit visuo-spatial abilities. Twenty-four non mentally-deteriorated RHD patients [12 with clinical neglect (RHDN+), 12 without clinical neglect (RHDN-)], and 12 healthy controls were included in the study. Participants were administered an ad hoc numerical battery assessing abilities such as counting, number magnitude comparison, writing and reading Arabic numerals and mental calculation, among others. Significant differences emerged among healthy controls and both the RHDN+ group and the RHDN- group, suggesting that the mathematical impairment of RHD patients does not necessarily correspond to the presence of left-neglect. A detailed analysis of the sub-tests of the battery evidenced expected differences among RHDN+ patients, RHDN- patients, and controls in writing and reading Arabic numerals. Crucially, differences between RHDN+ patients and controls were also found in tasks such as mental subtraction and mental multiplication, which do not require written visuo-spatial abilities. The present findings thus suggest that unilateral right hemisphere lesions may produce specific representational deficits that affect simple mental calculation, and not only the spatial arrangement of multi-digit written numbers as previously thought.

Is two better than one? Limb activation treatment combined with contralesional arm vibration to ameliorate signs of left neglect.

In the present study, we evaluated the effects of the Limb Activation Treatment (LAT) alone and in combination with the Contralateral Arm Vibration (CAV) on left neglect (LN) rehabilitation. We conceived them as techniques that both prompt the activation of the lesioned right hemisphere because of the activation (with the LAT as an active technique) and the stimulation (with the CAV as a passive technique) of the left hemibody. To test the effect of the simultaneous use of these two techniques (i.e., LAT and CAV) on visuo-spatial aspects of LN, we described the case of an LN patient (GR), who showed high intra-individual variability (IIV) in performance. Given the high IIV of GR, we used an ABAB repeated-measures design to better define the effectiveness of the combined application of LAT and CAV, as a function of time. The results showed an improvement of GR's performance on the Bells test following the combined application of LAT and CAV, with respect to the application of LAT alone. We did not find, however, significant effects of treatment on two other LN tests (i.e., Line bisection and Picture scanning). We propose that the combined application of LAT and CAV can be beneficial for some aspects of LN.

Visual Scanning Training, Limb Activation Treatment, and Prism Adaptation for Rehabilitating Left Neglect: Who is the Winner?

WE COMPARED, FOR THE FIRST TIME, THE OVERALL AND DIFFERENTIAL EFFECTS OF THREE OF THE MOST WIDELY USED LEFT NEGLECT (LN) TREATMENTS: visual scanning training (VST), limb activation treatment (LAT), and prism adaptation (PA). Thirty-three LN patients were assigned in quasi-random order to the three groups (VST, LAT, or PA). Each patient received only one type of treatment. LN patients' performance on everyday life tasks was assessed four times (over a period of 6 weeks): A1 and A2 (i.e., the two pre-treatment assessments); A3 and A4 (i.e., the two post-treatment assessments). LN patients in each of the three treatment conditions were treated for the same number of sessions (i.e., 20). The results showed that improvements were present in the majority of the tests assessing the peripersonal space in everyday life activities. Our findings were independent of unspecific factors and lasted for at least 2 weeks following the end of the treatments. There were no interactions, however, between LN treatments and assessments. We suggest that all three treatments can be considered as valid rehabilitation interventions for LN and could be employed for ameliorating LN signs.

Is "hit and run" a single word? The processing of irreversible binomials in neglect dyslexia.

The present study is the first neuropsychological investigation into the problem of the mental representation and processing of irreversible binomials (IBs), i.e., word pairs linked by a conjunction (e.g., "hit and run," "dead or alive"). In order to test their lexical status, the phenomenon of neglect dyslexia is explored. People with left-sided neglect dyslexia show a clear lexical effect: they can read IBs better (i.e., by dropping the leftmost words less frequently) when their components are presented in their correct order. This may be taken as an indication that they treat these constructions as lexical, not decomposable, elements. This finding therefore constitutes strong evidence that IBs tend to be stored in the mental lexicon as a whole and that this whole form is preferably addressed in the retrieval process.

Reading compounds in neglect dyslexia: the headedness effect.

Reading compound words was studied in neglect dyslexia in order to assess the influence of 'headedness'. The 'head' of a compound is the component that determines the grammatical category, the syntactic (e.g., the gender) and the semantic properties of the compound as a whole. For example, in the word 'blackberry'berry is the compound's head. The question was addressed of whether or not the privileged status of the head constituent influences processing and determines behavioural patterns in the breakdown of spatial attention in neglect. Italian right-headed (e.g. capobanda, band leader) and left-headed compounds (e.g. astronave, spaceship) were administered to 18 participants affected by neglect dyslexia. Left-headed compounds were read better than right-headed compounds. This result was not due to factors such as frequency, familiarity, age of acquisition or imageability, since these effects were controlled. It is suggested that attention is captured by the head component after implicit reading of the whole word. The head would require a relatively lighter processing load than the modifier and benefit from top-down facilitation.