Movement of environmental threats modifies the relevance of the defensive eye-blink in a spatially-tuned manner.

Subcortical reflexive motor responses are under continuous cortical control to produce the most effective behaviour. For example, the excitability of brainstem circuitry subserving the defensive hand-blink reflex (HBR), a response elicited by intense somatosensory stimuli to the wrist, depends on a number of properties of the eliciting stimulus. These include face-hand proximity, which has allowed the description of an HBR response field around the face (commonly referred to as a defensive peripersonal space, DPPS), as well as stimulus movement and probability of stimulus occurrence. However, the effect of stimulus-independent movements of objects in the environment has not been explored. Here we used virtual reality to test whether and how the HBR-derived DPPS is affected by the presence and movement of threatening objects in the environment. In two experiments conducted on 40 healthy volunteers, we observed that threatening arrows flying towards the participant result in DPPS expansion, an effect directionally-tuned towards the source of the arrows. These results indicate that the excitability of brainstem circuitry subserving the HBR is continuously adjusted, taking into account the movement of environmental objects. Such adjustments fit in a framework where the relevance of defensive actions is continually evaluated, to maximise their survival value

Listening to a conversation with aggressive content expands the interpersonal space

The distance individuals maintain between themselves and others can be defined as ‘interpersonal space’. This distance can be modulated both by situational factors and individual characteristics. Here we investigated the influence that the interpretation of other people interaction, in which one is not directly involved, may have on a person’s interpersonal space. In the current study we measured, for the first time, whether the size of interpersonal space changes after listening to other people conversations with neutral or aggressive content. The results showed that the interpersonal space expands after listening to a conversation with aggressive content relative to a conversation with a neutral content. This finding suggests that participants tend to distance themselves from an aggressive confrontation even if they are not involved in it. These results are in line with the view of the interpersonal space as a safety zone surrounding one’s body

Altered visuo-spatial processing in the peri-personal space: a new look at the hand-proximity effects

The previous studies have shown the importance of body in the visuo-spatial representation of space and the objects in it. Perception of objects located near the body trigger activations in brain regions involved in making voluntary movements. Such activations are restricted to the peripersonal space (PPS) particularly within a certain distance of the hand and are considered the visual receptive field of this space. Behavioral findings have shown reduced response time and enhanced accuracy for targets presented in the peri-hand space, referred to as the peri-hand effect. There has been considerable debate about the nature of these effects with some researchers arguing that it is attentional and others arguing that it is perceptual. In the current review, we summarize research about the PPS with a special focus on the peri-hand space and changes to visuo-spatial processing associated with objects places in this space. We suggest that there is enough evidence in the literature pointing at independent and dissociable perceptual and attentional effects in the peri-hand space. We also highlight the differences in the spatial extent of these effects for perception and attention. We propose that future studies looking at the peri-hand effects should dissociate these effects to better understand the nature of visual processing occurring in the peri-hand space.by Tony Thomas and Meera Mary Sunn