Mapping the human praxis network: an investigation of white matter disconnection in limb apraxia of gesture production

Abstract

Left hemispheric cerebral stroke can cause apraxia, a motor-cognitive disorder characterised by deficits of higher-order motor skills such as the failure to accurately produce meaningful gestures. This disorder provides unique insights into the anatomical and cognitive architecture of the human praxis system. The present study aimed to map the structural brain network that is damaged in apraxia. We assessed the ability to perform meaningful gestures with the hand in 101 patients with chronic left hemisphere stroke. Structural white matter fibre damage was directly assessed by diffusion tensor imaging and fractional anisotropy mapping. We used multivariate topographical inference on tract-based fractional anisotropy topographies to identify white matter disconnection associated with apraxia. We found relevant pathological white matter alterations in a densely connected fronto-temporo-parietal network of short and long association fibres. Hence, the findings suggest that heterogeneous topographical results in previous lesion mapping studies might not only result from differences in study design, but also from the general methodological limitations of univariate topographical mapping in uncovering the structural praxis network. A striking role of middle and superior temporal lobe disconnection, including temporo-temporal short association fibres, was found, suggesting strong involvement of the temporal lobe in the praxis network. Further, the results stressed the importance of subcortical disconnections for the emergence of apractic symptoms. Our study provides a fine-grain view into the structural connectivity of the human praxis network and suggests a potential value of disconnection measures in the clinical prediction of behavioural post-stroke outcome.

Thalamocortical networks involved in Pusher Syndrome

“…Most disorders originating from brain damage are (more) frequently observed and/or are predominantly lateralized, so previous structural disconnection studies focused on one hemisphere. [57][58][59][60] But due to the more heterogeneous anatomy of pusher syndrome and the different prerequisites concerning the investigation of functional and structural disconnection, our sample had to be treated differently to obtain meaningful results (i.e., separation according to thalamic versus cortical lesion or separation according to left versus right hemisphere, respectively). While this is necessary for the interpretability of the individual analyses, it impedes a direct comparison of the results derived from the two different methods.…”

Limb Apraxias: The Influence of Higher Order Perceptual and Semantic Deficits in Motor Recovery After Stroke

“…10,89–93 Additionally, new multivariate lesion-symptom mapping analysis techniques have increased the precision of their findings. 94,95…”

“…9,10,89,90 They have included ventral premotor cortex, involved in deficits identifying action goals 29,37,90 and inferior parietal cortex, involved in deficits of hand posture and kinematics. 37,81,93,94 There is a difference in lesion symptom mapping results for gesture recognition, according to whether the patients involved were in the subacute or chronic poststroke stages, suggesting different pathways for recovery of this deficit. 92 In left hemisphere stroke patients, there is involvement of the superior parietal lobe if they are at the subacute poststroke stage, versus lesions in ventro-dorsal and ventral streams—including superior temporal and inferior temporal areas, if they are at the chronic poststroke stage.…”

“…103 Several areas have been identified to be involved both in object-use as well as imitation tasks have been associated with lesions affecting the left middle/inferior temporal region. 10,46,93,94 A dissociation between inferior parietal and middle temporal lesions has been revealed with more fine-grained analyses. These show that postural components of object-related actions are linked to temporal lesions, whereas kinematics deficits are linked to parietal damage.…”

Single-Case Disconnectome Lesion-symptom Mapping: Identifying Two Subtypes of Limb Apraxia

“…Though this method has demonstrated sensitivity to corticospinal tract damage in relation to weakened contralateral hand grip strength (Greene et al, 2019), this metric provides a marker of cortical-to-cortical disconnection, and is therefore agnostic to the specific white matter tracts that are damaged. Thus, it will be important for future studies to identify the appropriate structural connectivity method (i.e., inferred or computed from diffusion imaging data) in addition to the fiber tracking algorithms used to quantify structural disconnection (e.g., probabilistic, deterministic, shortest path tractography) when investigating structure-function relations in participants with brain damage due to stroke or other neurological diseases (e.g., see Bi et al, 2015; Forkel et al, 2021; Gleichgerrcht et al, 2017; Griffis et al, 2019; Kuceyeski et al, 2016; Rosenzopf et al, 2022; Salvalaggio et al, 2020; Yeh et al, 2013).…”