Action observation with dual task for improving cognitive abilities in Parkinson’s disease. a pilot study

Action observation therapy (AOT) has been recently proposed as a new rehabilitation approach for treatment of motor deficits in Parkinson's disease. To date, this approach has never been used to deal with cognitive deficits (e.g., deficits in working memory, attention), which are impairments that are increasingly recognized in Parkinsonian patients. Typically, patients affected by these dysfunctions have difficulty filtering out irrelevant information and tend to lose track of the task goal. In this paper, we propose that AOT may also be used to improve cognitive abilities of Parkinsonian patients if it is used within a dual task framework. We articulate our hypothesis by pivoting on recent findings and on preliminary results that were obtained through a pilot study that was designed to test the efficacy of a long-term rehabilitation program that, for the first time, uses AOT within a dual task framework for treating cognitive deficits in patients with Parkinson's disease. Ten Parkinson's disease patients underwent a 45-min treatment that consisted in watching a video of an actor performing a daily-life activity and then executing it while performing distractive tasks (AOT with dual task). The treatment was repeated three times per week for a total of 4 weeks. Patients' cognitive/motor features were evaluated through standard tests four times: 1 month before treatment, the first and the last day of treatment and 1 month after treatment. The results show that this approach may provide relevant improvements in cognitive aspects related to working memory (verbal and visuospatial memory) and attention. We discuss these results by pivoting on literature on action observation and recent literature demonstrating that the dual task method can be used to stimulate cognition and concentration. In particular, we propose that using AOT together with a dual task may train the brain systems supporting executive functions through two mechanisms: (i) stimulation of goal setting within the mirror neuron system through action observation and (ii) working memory and persistent goal maintenance through dual task stimuli

Threat perception in social contexts: the defensive function of the peripersonal space

The main objective of this study is to evaluate how presence of dangerous objects and of other agents influence the perception of the peripersonal space. The peripersonal space indicates the reachable space surrounding the body, in which we can directly interact with objects. In contrast, the extrapersonal personal space designates the space beyond our reach (Holmes & Spence, 2004; Rizzolatti et al., 1997; di Pellegrino & Làdavas, 2015). Representation of the peripersonal space and our ability to act within it, are shaped by several factors, such as the presence of a tool (Canzonieri et al., 2013), the energetic cost associated with the task (Witt, 2011), and the goal of the intended action (Cole et al., 2013, Waiman et al., 2016). In psychology of social interactions, a similar concept is the personal space, which indicates the comfort distance we keep between ourselves and others, in which we feel ‘safe’ (Hall, 1966; Sommer, 2002). Although the peripersonal – as the reachable space for action - and the personal space – as social space – have been traditionally studied separately, recently, the relevance of the social dimension of the peripersonal space has been acknowledged (for a recent review see Bogdanova et al., 2021). Indeed, it has been demonstrated that the presence of both objects and other individuals affects our perception of the peripersonal space. Several studies have shown that the boundaries of the peripersonal space are enlarged by the presence of tools (Quesque et al., 2017) suggesting that a function of the peripersonal space is related to the regulation of goal-directed behaviour. However, in the presence of a dangerous object, the peripersonal space can also play a defensive function. Generally, dangerous objects are perceived as closer compared to neutral ones (Cole et al., 2013), especially when participants are asked to judge the reachability of the object (Coello et al., 2012). Additionally, dangerous objects might generate an ‘interference’ effect that slows down motor responses compared to neutral ones (Anelli et al., 2012; 2013). Recently, a neuroscientific study employing the electroencephalogram (EEG) showed that the perception of dangerous objects modulates cortical activity in a task-dependent way (Mustile et al., 2021). Dangerous objects generally elicit greater engagement of attentional resources compared to neutral ones, and this difference is reflected in event related potentials (ERPs), such as the visual P1 potential (marker of attentional processes), which is larger for dangerous objects compared to neutral objects, regardless of the task performed. However, when participants had to judge the reachability of the objects, dangerous stimuli elicited a more prominent frontal N2 potential, associated with motor inhibition, compared to neutral ones. Similarly to objects, also the presence of other agents might alter the boundaries of our peripersonal space. Indeed the mere presence of another ‘body’ in the visual scene expands the perceived extent of the near space (Fini et al., 2014; 2015). Furthermore, several studies have shown that the peripersonal space can be influenced also by the nature of the social dynamics. Teneggi et al. (2013) showed that the presence of another individual narrows the boundary of the peripersonal space, but only when participants interact cooperatively, compared to a condition in which they interact non-cooperatively. On the contrary, peripersonal space boundaries and the perceived comfort distance can increase when people experience social anxiety (Iachini et al., 2015, Lourenco et al., 2011), also suggesting a defensive nature of the peripersonal space in social contexts (Coello & Iachini, 2016; Gigliotti et al., 2019). So far, previous literature has provided relevant insights into the functions of the peripersonal space in relation to threatening objects or social contexts. However, no studies have investigated how simultaneous presence of a dangerous object and of another individual in a shared space, modulate the perception of the peripersonal space. This study’s aim is to address this topic. Stimuli. Stimuli will consist of 12 color pictures (1280 x 720 px) selected from the BOSS database (Brodeur et al., 2010) divided in two categories, neutral and dangerous artifacts (6 images each). Objects were rated by an independent group of 43 participants through an online questionnaire. Participants were required to rate each object on a five point Likert scale (Likert, 1932) according to harmfulness (danger/neutral), harmfulness to people (if used towards other people), knowledge (familiarity), dangerousness to grasp, visual complexity and belonging to the category of artifacts or natural objects (typicality). The analysis on the objects’ ratings have been already performed. Paired sample t-tests revealed significant differences for harmfulness [t(5) = 9.654, p < .001], for harmfulness to people [t(5) = 6.135, p < .001] and dangerousness to grasp [t(5) = 3.054, p < .05], but no difference for familiarity, visual complexity or typicality (p > .05). Procedure. In the experiment, participants will be asked to perform a reachability judgment task, which is assumed to involve the simulation of the reaching action with the arm, on both neutral and dangerous objects, displayed as images on an horizontal screen. Participants will be seated at the opposite side of a 49” touch screen table (Touchwindow Multi-Touch Display, 1099.4 x 634.0 x 36.8 mm) facing each other. Participants will be asked to sit at a constant distance from the edge of the table (20 cm between the torso and the edge of the table). The experiment will be programmed in Psychopy (version 2020.1.3) and it will run on a laptop connected to the touch screen. Responses will be provided through a black button fixed on the border of the touch screen (in the middle of the border, 34 cm from edges) and connected to the laptop where the experiment will run. A trial will start with a blue triangle appearing for 1500 ms in the center of the screen (at a position 0 for the x and y axes, vertical visual angle 63°). The triangle will point towards one of the two participants randomly, to indicate whose turn it is. Images of objects (displayed with a size of 3650 x 3650 px) will then appear in the center of the touch screen (position 0 for x and y axis on the screen,vertical visual angle 63°) and will start to move perpendicularly towards one of the participants with a speed of 10 cm/s on the y axis. Participants will be asked to press the button and to ‘stop’ the object when they think that the object is reachable for themselves or the other agent, depending on the direction of the movement (see Iachini et al., 2014). Responses will be provided either with le left or the right hand and response side will be counterbalanced across dyads. Experiment will include a total of 384 trials (96 per condition, agent and category) divided in 4 experimental blocks (96 trials per block). At the end of the experiment, participants will rate each object on a five point Likert scale (Likert, 1932) according to harmfulness (danger/neutral), harmfulness to people (if used towards other people), knowledge (familiarity), dangerousness to grasp, visual complexity and belonging to the category of artifacts or natural objects (typicality). Additionally, participants will also complete the risk taking scale DOSPERT (Blais & Weber, 2006). These ratings will be used for further exploratory analysis