Neural Mechanisms of Prism Adaptation in Healthy Adults and Individuals with Spatial Neglect after Unilateral Stroke: A Review of fMRI Studies

Abstract

Functional disability due to spatial neglect hinders recovery in up to 30% of stroke survivors. Prism adaptation treatment (PAT) may alleviate the disabling consequences of spatial neglect, but we do not yet know why some individuals show much better outcomes following PAT than others. The goal of this scoping review and meta-analysis was to investigate the neural mechanisms underlying prism adaptation (PA). We conducted both quantitative and qualitative analyses across fMRI studies investigating brain activity before, during, and after PA, in healthy individuals and patients with right or left brain damage (RBD or LBD) due to stroke. In healthy adults, PA was linked with activity in posterior parietal and cerebellar clusters, reduced bilateral parieto-frontal connectivity, and increased fronto-limbic and sensorimotor network connectivity. In contrast, RBD individuals with spatial neglect relied on different circuits, including an activity cluster in the intact left occipital cortex. This finding is consistent with a shift in hemispheric dominance in spatial processing to the left hemisphere. However, more studies are needed to clarify the contribution of lesion location and load on the circuits involved in PA after unilateral brain damage. Future studies are also needed to clarify the relationship of decreasing resting state functional connectivity (rsFC) to visuomotor function.

Impacts of Prism Adaptation Treatment on Spatial Neglect and Rehabilitation Outcome: Dosage Matters

“…21 Vilimovsky et al 24 also postulated that the sham-control condition could strengthen sustained attention, which in turn, activated attentional neural networks resulting in SN improvement. 43 Future studies are needed to investigate the mechanisms of PAT, 12 which is beyond the scope of the current discussion.…”

“…6,7 Decades of research has consistently demonstrated the negative impact of SN on rehabilitation outcomes. [8][9][10][11] Prism adaptation treatment (PAT; for detailed treatment procedures and mechanisms, see recent reviews) [12][13][14][15] is promising in reducing SN symptoms and improving functional outcomes. 16,17 We conducted a retrospective, matched control study (N = 312) 18 that demonstrated the effectiveness of PAT when embedded in occupational therapy practice on inpatient rehabilitation outcomes.…”

Choosing Sides: Impact of Prismatic Adaptation on the Lateralization of the Attentional System

“…Since fMRI yield better spatial resolution, they are likely to provide better insight into putative neural mechanisms. The relevant publications were recently summarized in a comprehensive review, which we recommend for further reading ( Boukrina and Chen, 2021 ).…”

“…Seminal behavior and imaging studies have addressed the issue of neural mechanisms, which underlie the effect of exposure to right- or left-deviating prisms and several models have been proposed. Putative mechanisms include change in motor behaviors ( Striemer and Danckert, 2010 ), in hemispheric lateralization of the ventral attentional network (VAN) ( Clarke and Crottaz-Herbette, 2016 ) and in interhemispheric inhibition ( Boukrina and Chen, 2021 ) as well as cerebellar contribution to adaptation ( Pisella et al, 2005 , 2006 ) and major reorganization of cortical regions involved in visuo-motor recalibration, in realignment of spatial representations and in spatially related cognition ( Panico et al, 2020 ). As pointed out in several reviews, the neural mechanisms by which low-level motor adaptation impacts high-level cognitive functions remain, however, elusive ( Rossetti et al, 2015 ; Panico et al, 2020 ).…”

Spatial Neglect in Stroke Patients

“…1). Obrázek 2: Fáze prizmatické adaptace (Boukrina et Chen, 2021) Tento post efekt je zde určující pro zlepšení uvědomování si kontralaterální části prostoru, neboť pacienti s prostorovým neglektem zřídka iniciují exploraci této části prostorového pole (Frassinetti et al, 2002). Kromě zvýšené explorace zrakového opomíjeného prostoru (Dijkerman et al, 2003) se pozitivní efekt prizmatické adaptace projevuje také v oblasti jiných senzorických modalit, včetně taktilní (Chen et al, 2018), sluchové extinkce (Jacquin-Courtois et al, 2010), somato--senzorické (Dijkerman et al, 2004) nebo haptické percepce (Girardi et al, 2004).…”