Effectiveness of action observation treatment based on pathological model in hemiplegic children: a randomized-controlled trial.

BACKGROUND: Action observation treatment (AOT) is an innovative therapeutic approach consisting in the observation of actions followed by their subsequent repetition. The standard version of AOT consists in the observation/imitation of a typically developed individual, which is proposed as model (TDM-AOT). AIM: This study aims to compare the effectiveness of AOT based on a pathological ameliorative model (PAM-AOT) versus TDM-AOT in improving upper limb ability in children with unilateral cerebral palsy (UCP). DESIGN: The study consists in a prospective randomized controlled, evaluator-blinded trial (RCT), with two active arms, designed to evaluate the effectiveness of AOT based on pathological model (PAM-AOT) as compared to a standard AOT based on TDM (TDM-AOT). SETTING: The 3-week AOT program was administered in a clinical setting. For some patients, the treatment was delivered at participant's home with the remote support of the physiotherapist (tele-rehabilitation). POPULATION: Twenty-six children with UCP (mean age 10.5±3.09 years; 14 females) participated in the study, with the experimental group observing a pathological model and the control group observing a typically developed model. METHODS: Motor assessments included unimanual and bimanual ability measures conducted at T0 (baseline, before the treatment), T1 (3 weeks after T0), T2 (8-12 weeks after treatment) and T3 (24-28 weeks after treatment); a subset of 16 patients also underwent fMRI motor assessment. Generalized Estimating Equations models were used for statistical analysis. RESULTS: Both groups showed significant improvement in bimanual function (GEE, Wald 106.16; P<0.001) at T1 (P<0.001), T2 (P<0.001), and T3 (P<0.001). Noteworthy, the experimental group showed greater improvement than the control group immediately after treatment (P<0.013). Both groups exhibited similar improvement in unimanual ability (GEE, Wald 25.49; P<0.001). The fMRI assessments revealed increased activation of ventral premotor cortex after treatment in the experimental compared with control group (GEE, Wald 6.26; P<0.012). CONCLUSIONS: Overall, this study highlights the effectiveness of PAM-AOT in achieving short-term improvement of upper limb ability in children with UCP. CLINICAL REHABILITATION IMPACT: These findings have significant implications for rehabilitative interventions based on AOT in hemiplegic children, by proposing a non-traditional approach focused on the most functional improvement achievable by imitating a pathological model.

Decoding point-light displays and fully visible hand grasping actions within the action observation network.

Action observation typically recruits visual areas and dorsal and ventral sectors of the parietal and premotor cortex. This network has been collectively termed as extended action observation network (eAON). Within this network, the elaboration of kinematic aspects of biological motion is crucial. Previous studies investigated these aspects by presenting subjects with point-light displays (PLDs) videos of whole-body movements, showing the recruitment of some of the eAON areas. However, studies focused on cortical activation during observation of PLDs grasping actions are lacking. In the present functional magnetic resonance imaging (fMRI) study, we assessed the activation of eAON in healthy participants during the observation of both PLDs and fully visible hand grasping actions, excluding confounding effects due to low-level visual features, motion, and context. Results showed that the observation of PLDs grasping stimuli elicited a bilateral activation of the eAON. Region of interest analyses performed on visual and sensorimotor areas showed no significant differences in signal intensity between PLDs and fully visible experimental conditions, indicating that both conditions evoked a similar motor resonance mechanism. Multivoxel pattern analysis (MVPA) revealed significant decoding of PLDs and fully visible grasping observation conditions in occipital, parietal, and premotor areas belonging to eAON. Data show that kinematic features conveyed by PLDs stimuli are sufficient to elicit a complete action representation, suggesting that these features can be disentangled within the eAON from the features usually characterizing fully visible actions. PLDs stimuli could be useful in assessing which areas are recruited, when only kinematic cues are available, for action recognition, imitation, and motor learning.

Structural connectivity associated with the sense of body ownership: a diffusion tensor imaging and disconnection study in patients with bodily awareness disorder.

The brain mechanisms underlying the emergence of a normal sense of body ownership can be investigated starting from pathological conditions in which body awareness is selectively impaired. Here, we focused on pathological embodiment, a body ownership disturbance observed in brain-damaged patients who misidentify other people's limbs as their own. We investigated whether such body ownership disturbance can be classified as a disconnection syndrome, using three different approaches based on diffusion tensor imaging: (i) reconstruction of disconnectome maps in a large sample (N = 70) of stroke patients with and without pathological embodiment; (ii) probabilistic tractography, performed on the age-matched healthy controls (N = 16), to trace cortical connections potentially interrupted in patients with pathological embodiment and spared in patients without this pathological condition; (iii) probabilistic 'in vivo' tractography on two patients without and one patient with pathological embodiment. The converging results revealed the arcuate fasciculus and the third branch of the superior longitudinal fasciculus as mainly involved fibre tracts in patients showing pathological embodiment, suggesting that this condition could be related to the disconnection between frontal, parietal and temporal areas. This evidence raises the possibility of a ventral self-body recognition route including regions where visual (computed in occipito-temporal areas) and sensorimotor (stored in premotor and parietal areas) body representations are integrated, giving rise to a normal sense of body ownership.

Effectiveness of action observation therapy based on virtual reality technology in the motor rehabilitation of paretic stroke patients: a randomized clinical trial.

BACKGROUND: The rehabilitation of paretic stroke patients uses a wide range of intervention programs to improve the function of impaired upper limb. A new rehabilitative approach, called action observation therapy (AOT) is based on the discovery of mirror neurons and has been used to improve the motor functions of adult stroke patients and children with cerebral palsy. Recently, virtual reality (VR) has provided the potential to increase the frequency and effectiveness of rehabilitation treatment by offering challenging and motivating tasks.  METHODS: The purpose of the present project is to design a randomized controlled six-month follow-up trial (RCT) to evaluate whether action observation (AO) added to standard VR (AO + VR) is effective in improving upper limb function in patients with stroke, compared with a control treatment consisting of observation of naturalistic scenes (CO) without any action content, followed by VR training (CO + VR). DISCUSSION: AO + VR treatment may provide an addition to the rehabilitative interventions currently available for recovery after stroke and could be utilized within standard sensorimotor training or in individualized tele-rehabilitation. TRIAL REGISTRATION: The trial has been prospectively registered on ClinicalTrials.gov. NCT05163210 . 17 December 2021.

Decoding grip type and action goal during the observation of reaching-grasping actions: A multivariate fMRI study.

During execution and observation of reaching-grasping actions, the brain must encode, at the same time, the final action goal and the type of grip necessary to achieve it. Recently, it has been proposed that the Mirror Neuron System (MNS) is involved not only in coding the final goal of the observed action, but also the type of grip used to grasp the object. However, the specific contribution of the different areas of the MNS, at both cortical and subcortical level, in disentangling action goal and grip type is still unclear. Here, twenty human volunteers participated in an fMRI study in which they performed two tasks: (a) observation of four different types of actions, consisting in reaching-to-grasp a box handle with two possible grips (precision, hook) and two possible goals (open, close); (b) action execution, in which participants performed grasping actions similar to those presented during the observation task. A conjunction analysis revealed the presence of shared activated voxels for both action observation and execution within several cortical areas including dorsal and ventral premotor cortex, inferior and superior parietal cortex, intraparietal sulcus, primary somatosensory cortex, and cerebellar lobules VI and VIII. ROI analyses showed a main effect for grip type in several premotor and parietal areas and cerebellar lobule VI, with higher BOLD activation during observation of precision vs hook actions. A grip x goal interaction was also present in the left inferior parietal cortex, with higher BOLD activity during precision-to-close actions. A multivariate pattern analysis (MVPA) revealed a significant accuracy for the grip model in all ROIs, while for the action goal model, significant accuracy was observed only for left inferior parietal cortex ROI. These findings indicate that a large network involving cortical and cerebellar areas is involved in the processing of type of grip, while final action goal appears to be mainly processed within the inferior parietal region, suggesting a differential contribution of the areas activated in this study.

Grasping and Manipulation: Neural Bases and Anatomical Circuitry in Humans.

Neurophysiological and neuroimaging evidence suggests a significant contribution of several brain areas, including subdivisions of the parietal and the premotor cortex, during the processing of different components of hand and arm movements. Many investigations improved our knowledge about the neural processes underlying the execution of reaching and grasping actions, while few studies have directly investigated object manipulation. Most studies on the latter topic concern the use of tools to achieve specific goals. Yet, there are very few studies on pure manipulation performed in order to explore and recognize objects, as well as on manipulation performed with a high level of manual dexterity. Another dimension that is quite neglected by the available studies on grasping and manipulation is, on the one hand, the contribution of the subcortical nodes, first of all the basal ganglia and cerebellum, to these functions, and, on the other hand, recurrent connections of these structures with cortical areas. In the first part, we have reviewed the parieto-premotor and subcortical circuits underlying reaching and grasping in humans, with a focus on functional neuroimaging data. Then, we have described the main structures recruited during object manipulation. We have also reported the contribution of recent structural connectivity techniques whereby the cortico-cortical and cortico-subcortical connections of grasping-related and manipulation-related areas in the human brain can be determined. Based on our review, we have concluded that studies on cortical and subcortical circuits involved in grasping and manipulation might be promising to provide new insights about motor learning and brain plasticity in patients with motor disorders.