Neural Underpinnings of Gesture Discrimination in Patients with Limb Apraxia

Abstract

Limb apraxia (LA), is a neuropsychological syndrome characterized by difficulty in performing gestures and may therefore be an ideal model for investigating whether action execution deficits are causatively linked to deficits in action understanding. We tested 33 left brain-damaged patients and 8 right brain-damaged patients for the presence of the LA. Importantly, we also tested all the patients in an ad hoc developed gesture recognition task wherein an actor performs, either correctly or incorrectly, transitive (using objects) or intransitive (without objects) meaningful conventional limb gestures. Patients were instructed to judge whether the observed gesture was correct or incorrect. Lesion analysis enabled us to evaluate the relationship between specific brain regions and behavioral performance in gesture execution and gesture comprehension. We found that LA was present in 21 left brain-damaged patients and it was linked to frontal and parietal lesions. Moreover, we found that recognition of correct execution of familiar gestures performed by others was more impaired in patients with LA than in nonapraxic patients. Crucially, the gesture comprehension deficit correlated with damage to the opercular and triangularis portions of the inferior frontal gyrus, two regions that are involved in complex aspects of action-related processing. In contrast, no such relationship was observed with lesions centered on the inferior parietal cortex. The present findings suggest that lesions to left frontal regions that are involved in planning and performing actions are causatively associated with deficits in the recognition of the correct execution of meaningful gestures.

Gesture Discrimination in Primary Progressive Aphasia: The Intersection between Gesture and Language Processing Pathways

“…This led to the classic model of "visuokinesthetic motor engrams," which guide the sequencing and timing of motor movements, that are localized to these inferior parietal regions (Heilman et al, 1982;Heilman and GonzalezRothi, 1993). A more recent voxel-based lesion-symptom mapping study in apraxic patients without aphasia suggested that the left inferior frontal gyrus rather than inferior parietal cortex is associated with deficits in gesture discrimination (Pazzaglia et al, 2008). Two lesion subtraction studies implicated a relatively extensive region containing inferior frontal as well inferior parietal cortex in gesture recognition (Tranel et al, 2003;Buxbaum et al, 2005).…”

Object words modulate the activity of the mirror neuron system during action imitation

“…Another fMRI study investigating brain activity during the observation of actions embedded or not embedded in contexts also confirmed the intention understanding function of the inferior frontal gyrus (Iacoboni et al., 2005b). Damage to the IFG has been shown to be associated with action understanding (e.g., gesture discrimination) deficits (Pazzaglia, Smania, Corato, & Aglioti, 2008). The role of the IFG in understanding action intention was confirmed by another study, which found that the activation in the IFG increased when the action intention is unusual (De Lange, Spronk, Willems, Toni, & Bekkering, 2008).…”

A Step Forward for Mirror Neurons? Investigating the Functional Link between Action Execution and Action Observation in Limb Apraxia

“…The data presented by Pazzaglia et al (2008) provide exciting evidence for a functional link between action observation and action execution in the human brain, the implications of which are widespread for both speech and limb apraxia. Furthermore, this provides a neurobiological rationale for established rehabilitation techniques and a framework for further development.…”

“…In a recent study published in The Journal of Neuroscience, Pazzaglia et al (2008) demonstrate that patients with limb apraxia, a specific deficit in executing skilled limb movements or gestures, also display a deficit in recognizing observed gestures. This study expands on previous studies (Rothi et al, 1985;Cubelli et al, 2006) by including a more detailed lesion analysis.…”

“…An additional confusion in the study by Pazzaglia et al (2008) is that of language abilities: right-brain-damaged patients scored better on language comprehension than left-brain-damaged (LBD) patients, and of the LBD patients, those without apraxia performed better than those with it. The authors address this by including training sessions and by demonstrating that gesture-recognition scores did not correlate with languagecomprehension scores.…”