Disconnections in personal neglect

Abstract

Personal neglect is a disorder in the perception and representation of the body that causes the patients to behave as if the contralesional side of their body does not exist. This clinical condition has not been adequately investigated in the past as it has been considered a symptom of unilateral spatial neglect, which has mainly been studied with reference to extrapersonal space. Only a few studies with small samples have investigated the neuroanatomical correlates of personal neglect, and these have mainly focused on discrete cortical lesions and modular accounts, as well as being based on the hypothesis that this disorder is associated with somatosensory and spatial deficits. In the present study, we tested the novel hypothesis that personal neglect may be associated not only with discrete cortical and subcortical lesions, but also with disconnections of white matter tracts. We performed an advanced lesion analyses in a large sample of 104 right hemisphere damaged patients, 72 of whom were suffering from personal neglect. Results from the analyses of the grey and white matter were controlled for co-occurrent clinical variables such as extrapersonal neglect, anosognosia for hemiplegia and motor deficits, along with other lesion-related variables such as lesion size and the interval from the lesion onset to neuroimaging recordings. Our results reveal that personal neglect is associated with lesions in a medial network which involves the temporal cortex (Heschl’s gyrus), the ventro-lateral nuclei of the thalamus and the fornix. This suggests that personal neglect involves a convergence between sensorimotor processes, spatial representation and the processing of self-referred information (episodic memory).

The flubbed body: Pathological body size representation in personal neglect

“…This may be due to an erroneous stored body image, which cannot be updated by experience (Riva, 2012), giving ED patients the impression to live with a 'wrong body' (Osman et al, 2004;Riva and Dakanalis, 2018;Riva et al, 2015). Given that PN has been considered as a disconnection syndrome that compromises a network of cortical and subcortical structures involved in body representation (Bertagnoli et al, 2022), it is possible that the visuospatial transformation and comparison between one's own body and the presented image required in this task (Peltz et al, 2011) may be impaired in PN, due to inability to access one's own body representation (Mohr et al, 2010;Spitoni et al, 2013). Hence, PN patients become locked to a distorted body representation (Di Vita, Palermo, Piccardi and Guariglia, 2015).…”

“…As shown in Table 1, both PN+ and PN-groups show lesions encompassing the basal ganglia. Recent studies have postulated that PN should be considered as a disconnection syndrome in which white matter tracks that underly body representation are damaged, rather than discrete modular lesions (Bertagnoli et al, 2022;Committeri et al, 2007; see also Committeri et al, 2018 for a revision). It is also possible that basal ganglia, known to change their role depending on the pathway involved in a specific function (Zeugin and Ionta, 2021), work differently in patients with PN who present with an impaired body representation network.…”

“…It is usually caused by injury of the right hemisphere to inferior parietal areas (Bisiach et al, 1986;Heilman et al, 2000); temporo-parietal junction (Baas et al, 2011); the postcentral and supramarginal gyri in the parietal lobe (Committeri et al, 2007;Rousseaux et al, 2015), and white matter connections to fronto-parietal areas, causing a "within-parietal disconnection" (Committeri et al, 2018(Committeri et al, , p. 274, 2007. When recurrent associated clinical variables have been taken into account (e.g., motor impairment and extrapersonal neglect), lesions associated to PN suggest a convergence of various factors involving a medial network (Bertagnoli et al, 2022) and a multi-factorial syndrome.…”

“…We presented pictures of their hands and face distorted for them to identify the one that most closely matched the correct size of the body. The visuospatial transformation between one's own body and the presented image will require the activation of the parietal cortex (Peltz et al, 2011), an area that is part of a network damaged in PN (Bertagnoli et al, 2022;Committeri et al, 2018). Thus, it was hypothesized that patients with PN (PN+) will show a more distorted representation of the body in comparison with a control group of healthy participants and patients without PN (PN-), as PN patients may be unable to retrieve the mental representation of their own body (Mohr et al, 2010;Spitoni et al, 2013).…”

Evaluation of upper limb perception after stroke: a prevalence and longitudinal study with the new Affected Limb Perception Questionnaire (ALPQ)

“…More recently, new approaches studying the networks or their disconnections have been used (e.g. [24][25][26]), suggesting that network's disconnection may better explain alterations in BPs than damage of discrete cerebral areas [1]. However, each of these studies focused only on a speci c neuropsychological alteration (e.g.…”