Description

Corticobasal syndrome (CBS) is a form of atypical Parkinsonian disorder that shares several features with Parkinson's disease (e.g., rigidity, tremor, and difficulties in balance and coordination). However, CBS additionally includes other motor and highly cortical features such as dyspraxia, dystonia, myoclonus, aphasia, sensory loss, and alien limb. Other features including abnormal eye movements, difficulties in objects recognition, and speech changes can also be revealed. The symptoms of CBS often appear in an asymmetric pattern that only shows on one side of the body. Imaging research has found that CBS is associated with brain atrophy in dorsal neocortical regions and basal ganglia. In particular, widespread frontoparietal cortex atrophy is exhibited in CBS. The frontoparietal network is known to orchestrate accurate, rapid, and goal-directed motor behaviors which are crucial performances in the daily life of humans.

Transcranial direct current stimulation (tDCS) is non-invasive neuromodulation that uses direct electrical currents to stimulate specific brain regions. This painless stimulation has been largely developed as a promising tool for depression, stroke, Parkinson's disease as well as other neuropsychological disorders. Specifically, tDCS over the frontoparietal area has enhanced processing speed and consolidation as well as upper extremity performances.

While tDCS has been applied to modulate a variety of cognitive and motor abilities, studies using tDCS in CBS patients are limited. To the best of the investigators' knowledge, two studies have been investigated on how tDCS modulation over the parietal cortex enhances the performance of an ideomotor apraxia test as well as action observation and representation in CBS. These studies provided potentials of using tDCS as a promising tool for linguistic and sensorimotor deficits in patients with CBS. Intriguingly, previous studies have suggested that tDCS combined with rehabilitative training can enhance motor outcomes. Furthermore, there is a need to better understand the mechanisms and effects of tDCS in real time in order to cater treatment protocols in a patient-specific manner. For this purpose, electroencephalography (EEG) has been proposed. EEG which measures brainwaves in milliseconds will be able to measure neurophysiological responses during tDCS modulation as well as rehabilitation intervention, such as music therapy.

Music has been extensively developed as a therapeutic medium to enhance and/or maintain functional skills based on scientific evidence in neurorehabilitation settings. In particular, the use of musical cueing to facilitate motor and cognitive performance has been widely studied. Patterned Sensory Enhancement (PSE) is one of the Neurologic Music Therapy (NMT) interventions to facilitate functional movement patterns and sequences by using tempo, meter, and rhythmic patterns. PSE translates movement patterns into musical patterns to provide spatial, temporal, and force cues. PSE has been employed to improve the functional motor abilities of individuals with stroke, cerebral palsy and Parkinson's disease.

Despite the importance of developing non-invasive but cost-effective interventions for CBS, neuro-rehabilitative effects associated with tDCS/EEG and PSE in this population have been less investigated. Therefore, the present study will investigate the effectiveness of PSE and PSE +tDCS on upper extremity performances in individuals with CBS, and EEG will be used to measure neurophysiological responses during sessions. Non-invasive and patient-oriented interventions may have a broad impact on CBS by improving the quality of functional upper extremity performance.