Marcello Costantini

Just a heartbeat away from one's body: interoceptive sensitivity predicts malleability of body-representations

Body-awareness relies on the representation of both interoceptive and exteroceptive percepts coming from ones body. However, the exact relationship and possible interaction of interoceptive and exteroceptive systems for body-awareness remain unknown. We sought to understand for the first time, to our knowledge, the interaction between interoceptive and exteroceptive awareness of the body. First, we measured interoceptive awareness with an established heartbeat monitoring task. We, then, used a multi-sensory-induced manipulation of body-ownership (e.g. Rubber Hand Illusion (RHI)) and we quantified the extent to which participants experienced ownership over a foreign body-part using behavioural, physiological and introspective measures. The results suggest that interoceptive sensitivity predicts the malleability of body representations, that is, people with low interoceptive sensitivity experienced a stronger illusion of ownership in the RHI. Importantly, this effect was not simply owing to a poor proprioceptive representation or differences in autonomic states of ones body prior to the multi-sensory stimulation, suggesting that interoceptive awareness modulates the online integration of multi-sensory body-percepts.

The role of the right temporo-parietal junction in maintaining a coherent sense of one's body

We constantly feel, see and move our body, and have no doubt that it is our own. The brain possesses a distinction between the body and the objects in the outside world. This distinction may be based on a process that monitors whether sensations, events and objects should be attributed to ones body or not. We controlled whether an external object was represented as part of the body or not, by experimentally inducing a bodily illusion using correlated visual and tactile stimulation. We then studied the role of right temporo-parietal junction (rTPJ) in the processing of multisensory events that may or may not be attributed to ones body. Disruption of rTPJ using transcranial magnetic stimulation (TMS) made the distinction between what may or may not be part of ones body on the basis of multisensory evidence more ambiguous, suggesting that the rTPJ is actively involved in maintaining a coherent sense of ones body, distinct from external, non-corporeal, objects.

Where does an object trigger an action? An investigation about affordances in space

A series of experiments provide evidence that affordances rely not only on the mutual appropriateness of the features of an object and the abilities of an individual, but also on the fact that those features fall within her own reachable space, thus being really ready-to-her-own-hand. We used a spatial alignment effect paradigm and systematically examined this effect when the visually presented object was located either within or outside the peripersonal space of the participants, both from a metric (Experiment 1) and from a functional point of view (Experiment 2). We found that objectual features evoke actions only when the object is presented within the portion of the peripersonal space that is effectively reachable by the participants. Experiments 3 and 4 ruled out that our results could be merely accounted for by differences in the visual salience of the presented objects. Our data suggest that the power of an object to automatically trigger an action is strictly linked to the effective possibility that an individual has to interact with it.

When objects are close to me: Affordances in the peripersonal space

In the present study, we investigated, using language, which motor information is automatically activated by observing 3-D objects (i.e., manipulation vs. function) and whether this information is modulated by the objects’ location in space. Participants were shown 3-D pictures of objects located in peripersonal versus extrapersonal space. Immediately after, they were presented with function, manipulation, or observation verbs (e.g., “to drink,” “to grasp,” “to look at”) and were required to judge whether the verb was compatible with the presented object. We found that participants were slower with observation verbs than with manipulation and function verbs. With both function and manipulation verbs, participants were faster when objects were presented in reachable space. Interestingly, the fastest response times were recorded when participants read function verbs while objects were presented in the accessible space. Results suggest that artifacts are first conceived in terms of affordances linked to manipulation and use, and that affordances are differently activated, depending on context.

Bodily ownership and self-location: Components of bodily self-consciousness

Recent research on bodily self-consciousness has assumed that it consists of three distinct components: the experience of owning a body (body ownership); the experience of being a body with a given location within the environment (self-location); and the experience of taking a first-person, body-centered, perspective on that environment (perspective). Here we review recent neuroimaging studies suggesting that at least two of these components-body ownership and self-location-are implemented in rather distinct neural substrates, located, respectively, in the premotor cortex and in the temporo-parietal junction. We examine these results and consider them in relation to clinical evidence from patients with altered body perception and work on a variety of multisensory, body-related illusions, such as the rubber hand illusion, the full body illusion, the body swap illusion and the enfacement illusion. We conclude by providing a preliminary synthesis of the data on bodily self-consciousness and its neural correlates.

The space of affordances: a TMS study.

Previous studies have shown a motor recruitment during the observation of graspable objects. This recruitment has been considered crucial in encoding the observed objects in terms of one or more potential motor acts. However, an agent can actually act upon an object only when the latter is close enough to be reached. Thus, the question we deal with in this paper is whether the motor system is always activated whenever a graspable object comes into view or whether it requires the object to be located within the reachable space of the perceiver. The left primary motor cortex was magnetically stimulated and motor evoked potentials (MEPs) were recorded while participants observed graspable and non graspable objects located within or outside their own reachable space. We found higher MEPs during the observation of graspable objects falling within the reachable space compared to the observation of either a non graspable object or a graspable object falling outside the reachable space. Our results shed new light on the functional role of the motor system in encoding visually presented objects. Indeed, they clearly indicate that its recruitment is spatially constrained, as it depends on whether the object falls within the actual reaching space of the onlooker.

Viewing one's own face being touched modulates tactile perception: An fmri study

The perception of tactile stimuli on the face is modulated if subjects concurrently observe a face being touched; this effect, termed visual remapping of touch (VRT), is maximum for observing ones own face. In the present fMRI study, we investigated the neural basis of the VRT effect. Participants in the scanner received tactile stimuli, near the perceptual threshold, on their right, left, or both cheeks. Concurrently, they watched movies depicting their own face, another persons face, or a ball that could be touched or only approached by human fingers. Participants were requested to distinguish between unilateral and bilateral tactile stimulation. Behaviorally, perception of tactile stimuli was modulated by viewing a tactile stimulation, with a stronger effect when viewing ones own face being touched. In terms of brain activity, viewing touch was related with an enhanced activity in the ventral intraparietal area. The specific effect of viewing touch on oneself was instead related with a reduced activity in both the ventral premotor cortex and the somatosensory cortex. The present findings suggest that VRT is supported by a network of fronto-parietal areas. The ventral intraparietal area might remap visual information about touch onto tactile processing. Ventral premotor cortex might specifically modulate multisensory interaction when sensory information is related to ones own body. Then this activity might back project to the somatosensory cortices, thus affecting tactile perception.

Looking Ahead: Anticipatory Gaze and Motor Ability in Infancy

The present study asks when infants are able to selectively anticipate the goals of observed actions, and how this ability relates to infants’ own abilities to produce those specific actions. Using eye-tracking technology to measure on-line anticipation, 6-, 8- and 10-month-old infants and a control group of adults were tested while observing an adult reach with a whole hand grasp, a precision grasp or a closed fist towards one of two different sized objects. The same infants were also given a comparable action production task. All infants showed proactive gaze to the whole hand grasps, with increased degrees of proactivity in the older groups. Gaze proactivity to the precision grasps, however, was present from 8 months of age. Moreover, the infants’ ability in performing precision grasping strongly predicted their ability in using the actor’s hand shape cues to differentially anticipate the goal of the observed action, even when age was partialled out. The results are discussed in terms of the specificity of action anticipation, and the fine-grained relationship between action production and action perception.

Ready both to your and to my hands: mapping the action space of others.

To date, mutual interaction between action and perception has been investigated mainly by focusing on single individuals. However, we perceive affording objects and acts upon them in a surrounding world inhabited by other perceiving and acting bodies. Thus, the issue arises as to whether our action-oriented object perception might be modulated by the presence of another potential actor. To tackle this issue we used the spatial alignment effect paradigm and systematically examined this effect when a visually presented handled object was located close either to the perceiver or to another individual (a virtual avatar). We found that the spatial alignment effect occurred whenever the object was presented within the reaching space of a potential actor, regardless of whether it was the participants own or the others reaching space. These findings show that objects may afford a suitable motor act when they are ready not only to our own hand but also, and most importantly, to the others hand. Our proposal is that this effect is likely to be due to a mapping of our own and the others reaching space and we posit that such mapping could play a critical role in joining our own and the others action.

A sensorimotor network for the bodily self

Neuroscientists and philosophers, among others, have long questioned the contribution of bodily experience to the constitution of self-consciousness. Contemporary research answers this question by focusing on the notions of sense of agency and/or sense of ownership. Recently, however, it has been proposed that the bodily self might also be rooted in bodily motor experience, that is, in the experience of oneself as instantiating a bodily structure that enables a specific range of actions. In the current fMRI study, we tested this hypothesis by making participants undergo a hand laterality judgment task, which is known to be solved by simulating a motor rotation of ones own hand. The stimulus to be judged was either the participants own hand or the hand of a stranger. We used this task to investigate whether mental rotation of pictures depicting ones own hands leads to a different activation of the sensorimotor areas as compared with the mental rotation of pictures depicting anothers hand. We revealed a neural network for the general representation of the bodily self encompassing the SMA and pre-SMA, the anterior insula, and the occipital cortex, bilaterally. Crucially, the representation of ones own dominant hand turned out to be primarily confined to the left premotor cortex. Our data seem to support the existence of a sense of bodily self encased within the sensorimotor system. We propose that such a sensorimotor representation of the bodily self might help us to differentiate our own body from that of others.