The rubber hand illusion in microgravity and water immersion.

Our body has evolved in terrestrial gravity and altered gravitational conditions may affect the sense of body ownership (SBO). By means of the rubber hand illusion (RHI), we investigated the SBO during water immersion and parabolic flights, where unconventional gravity is experienced. Our results show that unconventional gravity conditions remodulate the relative weights of visual, proprioceptive, and vestibular inputs favoring vision, thus inducing an increased RHI susceptibility.

"Stopping for knowledge": The sense of beauty in the perception-action cycle.

According to a millennial-old philosophical debate, aesthetic emotions have been connected to knowledge acquisition. Recent scientific evidence, collected across different disciplinary domains, confirms this link, but also reveals that motor inhibition plays a crucial role in the process. In this review, we discuss multidisciplinary results and propose an original account of aesthetic appreciation (the stopping for knowledge hypothesis) framed within the predictive coding theory. We discuss evidence showing that aesthetic emotions emerge in correspondence with an inhibition of motor behavior (i.e., minimizing action), promoting a simultaneous perceptual processing enhancement, at the level of sensory cortices (i.e., optimizing learning). Accordingly, we suggest that aesthetic appreciation may represent a hedonic feedback over learning progresses, motivating the individual to inhibit motor routines to seek further knowledge acquisition. Furthermore, the neuroimaging and neuropsychological studies we review reveal the presence of a strong association between aesthetic appreciation and the activation of the dopaminergic reward-related circuits. Finally, we propose a number of possible applications of the stopping for knowledge hypothesis in the clinical and education domains.

Agent-dependent modulation of corticospinal excitability during painful transcutaneous electrical stimulation.

Pain has an inhibitory effect on the corticospinal excitability that has been interpreted as an evolutionary mechanism, directed to down-regulate cortical activity in order to facilitate rapid protective spinal reflexes. Here, we focused on the link between defensive mechanisms and motor system and we asked whether voluntary actions can modulate the corticospinal excitability during painful stimulations. To this aim, we manipulated the volition-related aspects of our paradigm by comparing conditions in which either the participant (self-generated action) or the experimenter (other-generated action) pressed the button to deliver painful high-intensity transcutaneous electric shocks to the right digit V. MEPs to TMS were recorded from the FDI and APB muscles of the stimulated hand. A compelling agent-dependent modulation of the corticospinal excitability was found, showing, in self-generated compared to other-generated actions, a significantly lower inhibitory effect, as measured by greater MEP amplitude. This finding suggests a top-down modulation of volitional actions on defensive mechanisms, promoting the view that predictive information from the motor system attenuates the responses to the foreseeable adverse events generated by one's own actions as compared to unpredictable events generated by someone else's actions.

Beauty in mind: Aesthetic appreciation correlates with perceptual facilitation and attentional amplification.

Neuroaesthetic research suggests that aesthetic appreciation results from the interaction between the object perceptual features and the perceiver's sensory processing dynamics. In the present study, we investigated the relationship between aesthetic appreciation and attentional modulation at a behavioural and psychophysiological level. In a first experiment, fifty-eight healthy participants performed a visual search task with abstract stimuli containing more or less natural spatial frequencies and subsequently were asked to give an aesthetic evaluation of the images. The results evidenced that response times were faster for more appreciated stimuli. In a second experiment, we recorded visual evoked potentials (VEPs) during exposure to the same stimuli. The results showed, only for more appreciated images, an enhancement in C1 and N1, P3 and N4 VEP components. Moreover, we found increased attention-related occipital alpha desynchronization for more appreciated images. We interpret these data as indicative of the existence of a correlation between aesthetic appreciation and perceptual processing enhancement, both at a behavioural and at a neurophysiological level.

Aesthetic appreciation of musical intervals enhances behavioural and neurophysiological indexes of attentional engagement and motor inhibition.

From Kant to current perspectives in neuroaesthetics, the experience of beauty has been described as disinterested, i.e. focusing on the stimulus perceptual features while neglecting self-referred concerns. At a neurophysiological level, some indirect evidence suggests that disinterested aesthetic appreciation might be associated with attentional enhancement and inhibition of motor behaviour. To test this hypothesis, we performed three auditory-evoked potential experiments, employing consonant and dissonant two-note musical intervals. Twenty-two volunteers judged the beauty of intervals (Aesthetic Judgement task) or responded to them as fast as possible (Detection task). In a third Go-NoGo task, a different group of twenty-two participants had to refrain from responding when hearing intervals. Individual aesthetic judgements positively correlated with response times in the Detection task, with slower motor responses for more appreciated intervals. Electrophysiological indexes of attentional engagement (N1/P2) and motor inhibition (N2/P3) were enhanced for more appreciated intervals. These findings represent the first experimental evidence confirming the disinterested interest hypothesis and may have important applications in research areas studying the effects of stimulus features on learning and motor behaviour.

Oculomotor prismatic training is effective in ameliorating spatial neglect: a pilot study.

Visuomotor prismatic training has been demonstrated to be among the most effective rehabilitative techniques of spatial neglect, a neurological syndrome manifested by a number of right brain-damaged patients characterized by unawareness of the egocentric left half of the world. In the present study, we demonstrate that a novel oculomotor prismatic training procedure only consisting in a sequence of gaze shifts to visual targets, can reduce spatial neglect symptoms. Following oculomotor prismatic training, patients show a significant decrease in neglect severity in straight ahead and paper and pencil tasks. We propose that during oculomotor prismatic training, the inconsistency between the prisms-biased visual/oculomotor input and the unbiased head-on-trunk proprioceptive information relative to the straight-ahead position determines the observed aftereffects and the amelioration of spatial neglect symptoms.

Leftward oculomotor prismatic training induces a rightward bias in normal subjects.

Wedge prisms shifting the visual field laterally create a mismatch between the straight ahead position signalled by vision and that encoded by extraretinal and head-on-trunk proprioceptive information. Short-term adaptation to left-deviating prisms in normal subjects results in a visuomotor attentional bias towards the right-hand side (aftereffect). Prismatic adaptation (PA) is usually induced through a training consisting in repeated ballistic movements of the dominant arm towards visual targets, while participants are wearing prismatic goggles. The present study demonstrates that an original oculomotor PA procedure with leftward deviating prisms-without pointing movements and only consisting in repeated gaze shifts towards visual targets-can induce a rightward bias in normal subjects as assessed by visual straight ahead and line bisection tasks (Experiments 1 and 2). We show that oculomotor PA induces a bias in line bisection similar to that reported after visuomotor PA (Experiment 2). We suggest that a conflict between retinal, extraretinal and proprioceptive information about the straight ahead location causes the observed effects. In follow-up experiments 3, 4, and 5, we demonstrate that neither eye deviation without prisms nor shift of the visual field without eye deviation induces PA biases. We propose that an optimal integration model of visual and proprioceptive inputs can best account for the observed results.

Novelty is not enough: laser-evoked potentials are determined by stimulus saliency, not absolute novelty.

Event-related potentials (ERPs) elicited by transient nociceptive stimuli in humans are largely sensitive to bottom-up novelty induced, for example, by changes in stimulus attributes (e.g., modality or spatial location) within a stream of repeated stimuli. Here we aimed 1) to test the contribution of a selective change of the intensity of a repeated stimulus in determining the magnitude of nociceptive ERPs, and 2) to dissect the effect of this change of intensity in terms of "novelty" and "saliency" (an increase of stimulus intensity is more salient than a decrease of stimulus intensity). Nociceptive ERPs were elicited by trains of three consecutive laser stimuli (S1-S2-S3) delivered to the hand dorsum at a constant 1-s interstimulus interval. Three, equally spaced intensities were used: low (L), medium (M), and high (H). While the intensities of S1 and S2 were always identical (L, M, or H), the intensity of S3 was either identical (e.g., HHH) or different (e.g., MMH) from the intensity of S1 and S2. Introducing a selective change in stimulus intensity elicited significantly larger N1 and N2 waves of the S3-ERP but only when the change consisted in an increase in stimulus intensity. This observation indicates that nociceptive ERPs do not simply reflect processes involved in the detection of novelty but, instead, are mainly determined by stimulus saliency.

Cognitive aspects of nociception and pain: bridging neurophysiology with cognitive psychology.

The event-related brain potentials (ERPs) elicited by nociceptive stimuli are largely influenced by vigilance, emotion, alertness, and attention. Studies that specifically investigated the effects of cognition on nociceptive ERPs support the idea that most of these ERP components can be regarded as the neurophysiological indexes of the processes underlying detection and orientation of attention toward the eliciting stimulus. Such detection is determined both by the salience of the stimulus that makes it pop out from the environmental context (bottom-up capture of attention) and by its relevance according to the subject's goals and motivation (top-down attentional control). The fact that nociceptive ERPs are largely influenced by information from other sensory modalities such as vision and proprioception, as well as from motor preparation, suggests that these ERPs reflect a cortical system involved in the detection of potentially meaningful stimuli for the body, with the purpose to respond adequately to potential threats. In such a theoretical framework, pain is seen as an epiphenomenon of warning processes, encoded in multimodal and multiframe representations of the body, well suited to guide defensive actions. The findings here reviewed highlight that the ERPs elicited by selective activation of nociceptors may reflect an attentional gain apt to bridge a coherent perception of salient sensory events with action selection processes.