Losing dexterity: patterns of impaired coordination of finger movements in musician’s dystonia

Abstract

Extensive training can bring about highly-skilled action, but may also impair motor dexterity by producing involuntary movements and muscular cramping, as seen in focal dystonia (FD) and tremor. To elucidate the underlying neuroplastic mechanisms of FD, the present study addressed the organization of finger movements during piano performance in pianists suffering from the condition. Principal component (PC) analysis identified three patterns of fundamental joint coordination constituting finger movements in both patients and controls. The first two coordination patterns described less individuated movements between the “dystonic” finger and key-striking fingers for patients compared to controls. The third coordination pattern, representing the individuation of movements between the middle and ring fingers, was evident during a sequence of strikes with these fingers in controls, which was absent in the patients. Consequently, rhythmic variability of keystrokes was more pronounced during this sequence of strikes for the patients. A stepwise multiple-regression analysis further identified greater variability of keystrokes for individuals displaying less individuated movements between the affected and striking fingers. The findings suggest that FD alters dexterous joint coordination so as to lower independent control of finger movements, and thereby degrades fine motor control.

Aberrant cortical excitability reflects the loss of hand dexterity in musician's dystonia

“…) and/or loss of independent movement control between fingers (Furuya et al . ). Here, the novel behavioural findings are the prolonged IKI, IRI and finger‐key contact durations in the MD patients when playing at the fastest tempo (Fig.…”

“…In a previous kinematic study of piano keystrokes, MD patients with pronounced timing variability displayed reduced independent control of movements between the affected finger and a finger striking a key (Furuya et al . ). Together, the reduced SICI is a candidate biomarker of an FTSD symptom, impairment of individuated finger movements, which possibly underlies the temporally variable keystrokes of pianists with MD.…”

“…the loudness), and these parameters served as measures of finger dexterity (Furuya & Altenmüller, ; Furuya et al . ).…”

“…Second, methods have been established to evaluate motor dexterity during keyboard playing in musicians (Furuya & Altenmüller, ; Furuya et al . ), although no previous attempts have been made to connect behavioural and physiological measures in pianists with FTSD. All pianists underwent a thorough neurological examination.…”

Focal task specific dystonia: a review and update

“…Specifically, one suggested mechanism, found in several studies of FTSD patients, is the development of impaired surround inhibition, a neural inhibitory mechanism responsible for the selective recruitment and activation of muscles necessary for a particular task with inactivation of the neighboring muscles that are unnecessary [27, 29, 30]. Consistent with the hypothesis of decreased SICI and impaired surround inhibition, multiple studies have shown a loss of dexterity and impaired independent movement of fingers of patients with either writer’s cramp or musician’s dystonia [31–33]. …”