Grey and white matter substrates of action naming

Abstract

Despite a persistent interest in verb processing, data on the neural underpinnings of verb retrieval are fragmentary. The present study is the first to analyze the contributions of both grey and white matter damage affecting verb retrieval through action naming in stroke. We used voxel-based lesion-symptom mapping (VLSM) with an action naming task in 40 left-hemisphere stroke patients. Within the grey matter, we revealed the critical involvement of the left precentral and inferior frontal gyri, insula, and parts of basal ganglia. An overlay of white matter tract probability masks on the VLSM lesion map revealed involvement of left-hemisphere long and short association tracts with terminations in the frontal areas; and several projection tracts. The involvement of these structures is interpreted in the light of existing picture naming models, semantic control processes, and the embodiment cognition framework. Our results stress the importance of both cortico-cortical and cortico-subcortical networks of language processing.

Keywords: Aphasia; Picture naming; VLSM; Verbs; White-matter tracts.

Fig. 1.

Lesion overlay map of the voxels entered into the analysis (equal or more than four patients per voxel)

Fig. 2.

VLSM-map for action naming. Higher T-values appear in lighter shades of red. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3.

Left hemisphere long association white matter tracts affected by the lesion (probability of disconnection by the VLSM map > 80%). The significant VLSM cluster is shown in red. For the sake of visualization, the probabilistic masks of the tracts are thresholded at minimum 0.7. a – frontal aslant tract, b – inferior fronto-occipital fasciculus, c – superior longitudinal fasciculus III, d – uncinate fasciculus, e − superior longitudinal fasciculus II, f – long segment of the arcuate fasciculus. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4.

Left hemisphere short intralobar association white matter tracts affected by the lesion (probability of disconnection by the VLSM map > 80%). The significant VLSM cluster is shown in red. For the sake of visualization, the probabilistic masks of the tracts are thresholded at minimum 0.7. a – frontal orbito-polar tract, b – frontal inferior longitudinal tract, c – fronto-insular tract4. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 5.

Left hemisphere projection white matter tracts affected by the lesion (probability of disconnection by the VLSM map = 100%). The significant VLSM cluster is shown in red. For the sake of visualization, the probabilistic masks of the tracts are thresholded at minimum 0.7. a – anterior thalamic projections, b – cortico-spinal tract, c – fronto-striatal projection, d – fronto-pontine projections. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)