Structural white-matter connections mediating distinct behavioral components of spatial neglect in right brain-damaged patients

Abstract

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.

Disruption of large-scale electrophysiological networks in stroke patients with visuospatial neglect

“…Remarkably, changes in alpha-band connections significantly correlated with the severity of visuospatial biases and implicated symmetrical regions over the extra-striate visual cortex (pericalcarine and lingual), where hypoconnectivity with the left-hemisphere predicted more left visual-field omissions, while the converse (hypoconnectivity with the right-hemisphere) was observed for right visual-field omissions. This topographically-specific dysconnection pattern is compatible with the role of alpha rhythms in contralateral visuospatial attention (Ikkai, Dandekar, and Curtis 2016;Lobier, Palva, and Palva 2017;van Schouwenburg, Zanto, and Gazzaley 2017), as well as previous studies on hemineglect utilizing functional Sasaki et al 2013) and structural (Karnath et al 2011;Vaessen et al 2016) neuroimaging to delineate the functional neuro-anatomy of visuospatial deficits. Moreover, it is interesting to note that while the alpha band was implicated in the dysconnectivity pattern of right TPJ with sensory visual areas, the beta band was distinctively involved in dysconnectivity with left prefrontal areas which presumably subserve more executive processes of attention (Antzoulatos and Miller 2016).…”

“…Spatial neglect was assessed using a standard clinical battery similar to other research in our group (Saj et al 2013;Vaessen et al 2016), and diagnosed when patients demonstrated abnormal performance in the following tests: line bisection (cut-off: rightward deviation > 11%) (Schenkenberg, Bradford, and Ajax 1980a) and target cancellation test (cut-off: left -right omissions ≥ 4 out of 15 omissions) (Gauthier, Dehaut, and Joanette 1989). All stroke patients (n=15) selected for our sample demonstrated some signs of hemineglect according to at least one of these tests (86% of patients had cancellation deficits, 79% had line bisection deficits), as commonly observed after right hemisphere damage (Halligan et al 1991;) but neglect severity varied substantially between patients.…”

Using machine learning-based lesion behavior mapping to identify anatomical networks of cognitive dysfunction: spatial neglect and attention

“…Summarizing our anatomical results, multivariate lesion behavior mapping was able to depict the network by only one single analysis and by using only the CoC score as behavioral proxy for spatial neglect and attention, whereas previous studies needed to employ either a metaanalytical (Checlacz et al, 2012;Molenberghs et al, 2012 ), multi-imaging/multi-method (Corbetta et al, 2015;Ramsey et al, 2016), or ROI approaches (Smith et al, 2013) to increase power or to disentangle the behavioral sub-functions and map them separately (Verdon et al, 2010;Vaessen et al, 2016;Toba et al, 2018) to come to comparable conclusions. This indicates that the behavioral proxy we measured here is indeed a core symptom of spatial neglect as it might evolve regardless where within this network a lesion produces focal dysfunction or remote deficits through disconnection.…”

“…These might have contributed to the heterogeneous results of previous lesion-symptom mapping investigations in spatial neglect using mass-univariate VLBM (Karnath et al, 2004Committeri et al, 2007;Sarri et al, 2009;Chechlacz et al, 2010;Saj et al, 2012;Thiebaut De Schotten et al, 2014;Rousseaux et al, 2015) and DTI/white matter fiber analyses (Thiebaut De Schotten et al, 2005;Urbanski et al, 2008Urbanski et al, , 2011Karnath et al, 2009;Shinoura et al, 2009;Ciaraffa et al, 2013;Thiebaut De Schotten et al, 2014;Umarova et al, 2014;Lunven et al, 2015;Vaessen et al, 2016;Carter et al, 2017). While using meta-analytic approaches combining various VLBM results, one might be able to find all critical parts of the presumed network.…”

Increased Alpha-Rhythm Dynamic Range Promotes Recovery from Visuospatial Neglect: A Neurofeedback Study

“…We excluded patients with bilateral lesions, previous neurological or psychiatric disorders, impairment in primary visual perception (except partial visual field defect), psychiatric disorders, motor difficulties in the right upper limb, pusher syndrome (i.e., contralateral trunk deviation with active resistance to any attempt of external correction), or current psychotropic treatment. Spatial neglect was assessed using a standard clinical battery similar to other research in our group [15, 35] and diagnosed when patients demonstrated abnormal performance in the following tests: line bisection (cutoff: rightward deviation >11%) [36] and target cancellation test (cutoff: left–right omissions ≥4 out of 15 omissions) [37]. …”