Reconstructing neural representations of tactile space

Psychophysical experiments have demonstrated large and highly systematic perceptual distortions of tactile space. Such a space can be referred to our experience of the spatial organisation of objects, at representational level, through touch, in analogy with the familiar concept of visual space. We investigated the neural basis of tactile space by analysing activity patterns induced by tactile stimulation of nine points on a 3 × 3 square grid on the hand dorsum using functional magnetic resonance imaging. We used a searchlight approach within pre-defined regions of interests to compute the pairwise Euclidean distances between the activity patterns elicited by tactile stimulation. Then, we used multidimensional scaling to reconstruct tactile space at the neural level and compare it with skin space at the perceptual level. Our reconstructions of the shape of skin space in contralateral primary somatosensory and motor cortices reveal that it is distorted in a way that matches the perceptual shape of skin space. This suggests that early sensorimotor areas critically contribute to the distorted internal representation of tactile space on the hand dorsum

Embodying an invisible face shrinks the cone of gaze

The possibility of being invisible has long fascinating people. Recent research showed that multisensory illusions can induce experiences of bodily invisibility, allowing the psychological consequences of invisibility to be explored. Here, we demonstrate an illusion of embodying an invisible face. Participants received touches on their face and simultaneously saw a paintbrush moving synchronously in empty space and defining the shape of an invisible face. We show that such invisible enfacement induces a sense of ownership using both explicit questionnaire measures (Experiment 1) and implicit physiological measures (Experiment 2). We further demonstrated that embodying an invisible face shrinks the width of the cone of gaze, i.e. the range of eye deviations people judge as directed towards themselves (Experiment 3 and 4). These results suggest that the experience of invisibility affects the way in which we process the attention of others toward the self, starting from the perception of gaze direction

Characterizing the population receptive fields of the hand dorsum and palm

Introduction: In an fMRI study, we explored the population receptive eld (pRF; Dumoulin & Wandell, 2008) properties of the voxels in the dorsum and palm area of the primary somatosensory region (area 3b). Behavioural studies adopting tactile discrimination tasks suggested that these two skin surfaces are represented differently, with the dorsum representation being more distorted than the palm representation (Longo & Haggard, 2011). Longo and Haggard (2011) explained these results by suggesting that the receptive elds of the dorsum surface are more elongated along the proximodistal hand axis than the ones of the palm – the pixel model. The authors based this idea mostly on animal studies (e.g. Alloway et al, 1989; Brooks et al, 1961; Brown et al, 1975). However, it is not clear if this is also the case for humans as, to the best of our knowledge, no study so far has investigated the pixel hypothesis systematically. Methods: The same participant was tested in two fMRI experiments (12 runs for experiment 1; 6 runs for experiment 2). In separate runs, the experimenter manually stimulated either the participant's dorsum or palm with an object (a circle covering 4 grid cells when centred at one intersection in experiment 1, a square covering one cell in experiment 2). A 4x4 grid (7 cm per side) was drawn on the participant's palm and dorsum (Figure 1). In experiment 1, the intersections of the grid lines were numbered from 1 to 25, whereas in experiment 2 each cell of the grid was numbered from 1 to 16. An acoustic cue instructed the experimenter on which skin region to stimulate and for how long. In experiment 1, we employed a random sequence in which each grid intersection was stimulated once per run interleaved with 7 randomly presented null trials. Each trial was 4 seconds and included the delivery of the touch on the instructed location plus small rotatory movements in anti-clockwise and clockwise directions. In experiment 2, we used an ordered sequence from 1 to 16 and back which was repeated 4 times in each run (2 null trials were presented every 4 trials). A tactile stimulation lasted for 2 seconds and consisted of 4 tactile events (~ 2Hz) in which the object gently touched the target skin location. We estimated the shape of the pRFs in anatomically and functionally predened regions of interests (see Figure 2A). To t the data, we used an oriented elliptical Gaussian with four parameters: the stimulated skin location (x and y); the long and short axes of the ellipse (σ1 and σ2), and the orientation (ϑ). We dened the anisotropy as the absolute value of the logarithm of the ratio between the horizontal and vertical axis. Orientations were transformed such that ellipses with the long axis running along the proximodistal orientation had an angle of 90 degrees. Results: Figure 2B shows the results for the voxel with the highest goodness of t for each of the skin surfaces stimulated in experiment 2. The green dot indicates the centre of the elliptical shape. The estimated pRF on the dorsum has a higher anisotropy than the one on the palm. Figure 2C shows the locations of all the estimated pRFs. In Figure 2D, we plotted each semi-major axis angle as an oriented line with the length proportional to the level of anisotropy. Ellipses oriented along the proximodistal axis of the hand appear vertical in the plot. The thick line indicates the resultant vector which gives an indication of the general orientation and anisotropy within the area. In both experiments, the dorsum showed higher anisotropy and both skin surfaces showed a slight deviation from the vertical orientation. Conclusions: In this study, we were able to estimate the pRF locations and shapes of the hand dorsum and palm. Our results suggest that many pRFs of the dorsum are oval-shaped and oriented along the proximodistal axis of the hand; the pRFs on the palm also show a similar characteristic, but less than dorsum. This provides some support for the pixel model (Longo & Haggard, 2011)

Neural correlates of distorted body representations underlying tactile distance perception

Tactile distance perception is believed to require that immediate afferent signals be referenced to a stored representation of body size and shape (the body model). For this ability, recent studies have reported that the stored body representations involved are highly distorted, at least in the case of the hand, with the hand dorsum represented as wider and squatter than it actually is. Here, we aim to define the neural basis of this phenomenon. In a behavioural experiment participants estimated the distance between touches on two points by adjusting the length of a visually-presented line on the screen. The technique of multidensional scaling (MDS) was used to reconstruct a perceptual map of tactile space. Analysis of spatial distortion using Procrustes alignment showed that maps were stretched in the mediolateral hand axis. In order to determine the neural correlates of these body distortions, we performed an fMRI study. For each participant, we used a searchlight pattern classifier with Euclidean distance on pre-defined regions of interests (ROIs). In order to relate the representations between the different points and to computational models, we compare response-pattern dissimilarity matrices in these ROIs. Similar to the behavioural experiment, we used MDS to reconstruct maps of the neural representation of tactile space using the values from the dissimilarities matrices. We were able to reconstruct the perceptual map of tactile space in the contralateral primary somatosensory and motor cortices. This suggests that these areas are critical to generate the tactile representations of the dorsum of the hand

Reconstruction of the neural representations of the tactile space

We examined the neural basis of tactile distance perception by analyzing activity patterns induced by tactile stimulation of nine points on a 3 x 3 square grid on the hand dorsum using functional magnetic resonance (fMRI). We used a searchlight approach within pre-defined regions of interests (ROIs) to compute the pairwise Euclidean distances between the activity patterns elicited by tactile stimulation. Then, we used multidimensional scaling (MDS) to reconstruct skin space at the neural level and compare it with skin space at the perceptual level. Our reconstructions of the shape of skin space in contralateral primary somatosensory (SI) and motor (M1) cortices reveal that it is distorted in a way that matches the perceptual shape of skin space. This suggests that early sensorimotor areas are critical to processing tactile distance perception

Does ipsilateral remapping following hand loss impact motor control of the intact hand?

What happens once a cortical territory becomes functionally redundant? We studied how the brain and behaviour change for the remaining hand in humans (male and female) with either a missing hand from birth (one-handers) or due to amputation. Previous studies reported that in amputees, but not in one-handers, there is increased ipsilateral activity in the somatosensory territory of the missing hand (i.e., remapping). We used a complex finger task to explore whether this observed remapping in amputees involves recruiting more neural resources to support the intact hand to meet greater motor control demand. Using basic fMRI analysis, we found that only amputees had more ipsilateral activity when motor demand increased, however this did not match any noticeable improvement in their task performance. More advanced multivariate fMRI analysis showed that amputees had stronger and more typical representation – relative to controls’ contralateral hand representation – compared to one-handers. This suggests that in amputees, both hand areas work together more collaboratively, potentially reflecting the intact hand's efference copy. One-handers struggled to learn difficult finger configurations, but this did not translate to differences in univariate or multivariate activity relative to controls. Additional white matter analysis provided conclusive evidence that the structural connectivity between the two hand areas did not vary across groups. Together, our results suggest that enhanced activity in the missing hand territory may not reflect intact hand function. Instead, we suggest that plasticity is more restricted than generally assumed and may depend on the availability of homologous pathways acquired early in life

Predicting attitudinal and behavioral responses to COVID-19 pandemic using machine learning

At the beginning of 2020, COVID-19 became a global problem. Despite all the efforts to emphasize the relevance of preventive measures, not everyone adhered to them. Thus, learning more about the characteristics determining attitudinal and behavioral responses to the pandemic is crucial to improving future interventions. In this study, we applied machine learning on the multi-national data collected by the International Collaboration on the Social and Moral Psychology of COVID-19 (N = 51,404) to test the predictive efficacy of constructs from social, moral, cognitive, and personality psychology, as well as socio-demographic factors, in the attitudinal and behavioral responses to the pandemic. The results point to several valuable insights. Internalized moral identity provided the most consistent predictive contribution—individuals perceiving moral traits as central to their self-concept reported higher adherence to preventive measures. Similar was found for morality as cooperation, symbolized moral identity, self-control, open-mindedness, collective narcissism, while the inverse relationship was evident for the endorsement of conspiracy theories. However, we also found a non-negligible variability in the explained variance and predictive contributions with respect to macro-level factors such as the pandemic stage or cultural region. Overall, the results underscore the importance of morality-related and contextual factors in understanding adherence to public health recommendations during the pandemic

Social and moral psychology of COVID-19 across 69 countries

The COVID-19 pandemic has affected all domains of human life, including the economic and social fabric of societies. One of the central strategies for managing public health throughout the pandemic has been through persuasive messaging and collective behaviour change. To help scholars better understand the social and moral psychology behind public health behaviour, we present a dataset comprising of 51,404 individuals from 69 countries. This dataset was collected for the International Collaboration on Social & Moral Psychology of COVID-19 project (ICSMP COVID-19). This social science survey invited participants around the world to complete a series of moral and psychological measures and public health attitudes about COVID-19 during an early phase of the COVID-19 pandemic (between April and June 2020). The survey included seven broad categories of questions: COVID-19 beliefs and compliance behaviours; identity and social attitudes; ideology; health and well-being; moral beliefs and motivation; personality traits; and demographic variables. We report both raw and cleaned data, along with all survey materials, data visualisations, and psychometric evaluations of key variables

Author Correction: National identity predicts public health support during a global pandemic

Correction to: Nature Communications https://doi.org/10.1038/s41467-021-27668-9, published online 26 January 2022