ACTION OBSERVATION PLUS MOTOR IMAGERY AND SOMATOSENSORY DISCRIMINATION TRAINING ARE EFFECTIVE NON-MOTOR STRATEGIES TO IMPROVE MANUAL DEXTERITY

M. Agnelli¹, B. Libeccio¹, M.C. Frisoni¹, F. Temporiti^1,2, R. Gatti^1,2

¹IRCCS Humanitas Clinical and Research Center, Physiotherapy Unit, Milano, Italy, ²Humanitas University, Department of Biomedical Sciences, Milano, Italy

Background: Adequate sensory inputs processing and successful sensorimotor integration represent essential requirements to ensure appropriate manual dexterity. Action Observation, Motor Imagery and Somatosensory Discrimination Training represent sensory input-based approaches to train the motor system without necessarily asking subjects to perform active movements. The mechanisms of action of these non-motor strategies rely on different sensory channels and neurophysiological process, but their effects in terms of motor learning have never been compared.

Purpose: To investigate the effects of Action Observation plus Motor Imagery versus Somatosensory Discrimination Training on manual dexterity in healthy subjects.

Methods: In this three-armed randomized controlled study, 60 healthy right-handed participants were randomized into AOMI, SSDT or CTRL groups. AOMI group observed video-clips showing right-hand dexterity tasks and concurrently performed motor imagery of the observed actions. Participants allocated to SSDT group performed surfaces recognition and two-point distance discrimination tasks with the right hand, whereas CTRL group performed no intervention. A blinded physiotherapist assessed participants for manual dexterity using the Purdue Pegboard Test (Right hand - R, Left hand - L, Both hands - B, R+L+B and Assembly tasks) at baseline (T0) and after the training end (T1). The statistical analysis included a 2 x 3 mixed-design ANOVA with Time as within-subject factor and Group as between-subject factor to investigate between-group differences over time. the effect size from T0 to T1 was also calculated for each group using the Cohen’s d and interpreted as small (between 0.2 and 0.5), medium (between 0.5 and 0.8), large (between 0.8 and 1.3) and very large (greater than 1.3).

Results: No between-group differences were found at baseline. A Time by Group interaction and Time effect were found for R task score, which increased from T0 to T1 in all groups with very large effect size in AOMI (d=1.8, CI₉₅ 2.6-1.1) and SSDT (d=1.1, CI₉₅ 1.6-0.5) groups, and medium effect size in CTRL group (d=0.6, CI₉₅ 1.0-0.1). Time effects were also found in L, B, R+L+B and Assembly tasks score (p<0.001) without between-group differences. No statistically significant differences between AOMI and SSDT were found for any Purdue Pegboard Test task score.

Conclusions: Action Observation plus Motor Imagery and Somatosensory Discrimination Training resulted in effective non-motor approaches to improve manual dexterity in healthy subjects.

Implications: These non-motor approaches may represent viable strategies in rehabilitation to enhance manual dexterity in subjects with inability to perform voluntary movements or to minimize the decay in motor performance after hand immobilization due to traumas or surgery.

Funding acknowledgements: The authors did not receive any funding.

Keywords:
Action observation
Manual dexterity
Somatosensory discrimination

Topics:
Neurology
Disability & rehabilitation

Did this work require ethics approval? Yes

Institution: IRCCS Humanitas Clinical and Research Center

Committee: Internal Committee of Humanitas Clinical and Research Center

Ethics number: CLF22/10