Limb apraxia and the left parietal lobe

Abstract

Limb apraxia is a heterogeneous disorder of skilled action and tool use that has long perplexed clinicians and researchers. It occurs after damage to various loci in a densely interconnected network of regions in the left temporal, parietal, and frontal lobes. Historically, a highly classificatory approach to the study of apraxia documented numerous patterns of performance related to two major apraxia subtypes: ideational and ideomotor apraxia. More recently, there have been advances in our understanding of the functional neuroanatomy and connectivity of the left-hemisphere "tool use network," and the patterns of performance that emerge from lesions to different loci within this network. This chapter focuses on the left inferior parietal lobe, and its role in tool and body representation, action prediction, and action selection, and how these functions relate to the deficits seen in patients with apraxia subsequent to parietal lesions. Finally, suggestions are offered for several future directions that will benefit the study of apraxia, including increased attention to research on rehabilitation of this disabling disorder.

Keywords: action; action selection; body representations; gestures; imitation; limb apraxia; parietal; praxis; prediction; tool use.

Fig. 17.1.

A simplified cognitive praxis model, adapted from Rothi et al. (1997), including extensions suggested by Cubelli et al. (2000), Bartolo et al. (2003), and Randerath (2009). Extensions are indicated by gray boxes and dashed lines and explained in the text.

Fig. 17.2.

(A) Voxel-based lesion symptom-mapping analysis for overall tool use pantomime accuracy; false discovery rate, q = 0.05. (B) Voxels in the supramarginal gyrus and inferior frontral gyrus associated with deficient hand action score for “conflict” tools that are associated with more than one action, controlling for scores with “nonconflict” tools associated with one primary action, q = 0.05. (Reproduced from Watson CE, Buxbaum LJ (2015) A distributed network critical for selecting among tool-directed actions. Cortex 65C: 65–82, with permission.)

Fig. 17.3.

Voxel-based lesion symptom-mapping analysis of data from 131 patients showing voxels predicting tool action production controlling for recognition (pink/yellow) and vice versa (blue/green). False discovery rate, q = 0.05. (Reproduced from Tarhan LY, Watson CE, Buxbaum LJ (2015) Shared and distinct neuroanatomic regions critical for tool-related action production and recognition: evidence from 131 left-hemisphere stroke patients. J Cogn Neurosci 1–21,with permission from MIT Press.)