Improving ideomotor limb apraxia by electrical stimulation of the left posterior parietal cortex

Abstract

Limb apraxia, a deficit of planning voluntary gestures, is most frequently caused by damage to the left hemisphere, where, according to an influential neurofunctional model, gestures are planned, before being executed through the motor cortex of the hemisphere contralateral to the acting hand. We used anodal transcranial direct current stimulation delivered to the left posterior parietal cortex (PPC), the right motor cortex (M1), and a sham stimulation condition, to modulate the ability of six left-brain-damaged patients with ideomotor apraxia, and six healthy control subjects, to imitate hand gestures, and to perform skilled hand movements using the left hand. Transcranial direct current stimulation delivered to the left PPC reduced the time required to perform skilled movements, and planning, but not execution, times in imitating gestures, in both patients and controls. In patients, the amount of decrease of planning times brought about by left PPC transcranial direct current stimulation was influenced by the size of the parietal lobe damage, with a larger parietal damage being associated with a smaller improvement. Of interest from a clinical perspective, left PPC stimulation also ameliorated accuracy in imitating hand gestures in patients. Instead, transcranial direct current stimulation to the right M1 diminished execution, but not planning, times in both patients and healthy controls. In conclusion, by using a transcranial stimulation approach, we temporarily improved ideomotor apraxia in the left hand of left-brain-damaged patients, showing a role of the left PPC in planning gestures. This evidence opens up novel perspectives for the use of transcranial direct current stimulation in the rehabilitation of limb apraxia.

Brain Activation Patterns Characterizing Different Phases of Motor Action: Execution, Choice and Ideation

“…These findings are in line with clinical studies, showing that cerebral lesions in middle frontal and parietal circuits can cause ideational apraxia (Hécaen, 1972;Bolognini et al, 2015;De Renzi and Lucchelli, 1988). Further investigations will be necessary to explore whether patients with movement disorders, such as patients with Parkinson's disease, would engage the same neural circuits during motor ideation.…”

“…In conclusion, ideational apraxia might not constitute a higherorder programming deficit of movement per se, but a combination of executive, language, and memory deficits or a diffuse reduction of cognitive resources (Gross and Grossman, 2008). Different lesion sites have been indicated as responsible for ideational apraxia, showing an involvement of mainly left temporo-parieto-occipital regions (Hécaen, 1972;Bolognini et al, 2015) even if patients with ideational apraxia have also been reported following frontal lesions, or basal ganglia damage (De Renzi e Lucchelli, 1988;Manuel et al, 2013;Huey et al, 2009). Patients with ideational apraxia can retain mental imagery abilities (Tomasino et al, 2003).…”

Immediate and Sustained Effects of 5-Day Transcranial Direct Current Stimulation of the Motor Cortex in Phantom Limb Pain

“…Before the experiment, each patient underwent a detailed interview about phantom sensations in order to assess: 1) the features of phantom limb sensations; 2) the features of PLP; 3) presence of voluntary or involuntary phantom movements, or immobilized phantom postures; 4) any other subjective descriptions of the qualities of the deafferentation pain. Patients were encouraged to describe exhaustively the quality of any subjective sensation they perceived in their phantom limb.…”

“…The choice of the stimulation parameters was based on previous positive effects obtained in PLP [3,4], but also considering the blinding issue of using a higher intensity (e.g., 2 mA) in a cross-over design [39]. Sham tDCS was applied with the same parameters and electrode montage of active tDCS, but the current lasted only for 30 sec [18].…”

Hand-independent representation of tool-use pantomimes in the left anterior intraparietal cortex

“…A right visual field advantage for the visual processing of tools (Garcea et al 2012) and a tool-selective response in the left IPL independent of visual field were reported , which is consistent with left hemisphere 10 dominance for tool-selective processing. Recent studies using anodal transcranial direct current stimulation (tDCS) showed that electrical stimulation of the left PPC improves the processing of gesture or imitation in healthy participants (Weiss et al 2013) and also in IMA patients (Bianchi et al 2015;Bolognini et al 2015), which further suggest the importance of left PPC for gesture processing. 15 Among the dorsal visual stream within the PPC, the dorso-dorsal pathway comprising the superior parietal lobule (SPL) and ventro-dorsal pathway, including the IPL, are distinct pathways (Rizzolatti and Matelli 2003;Binkofski and Buxbaum 2013).…”