Defensive peripersonal space is modified by primary emotion and attachment dimension

The hand-blink reflex (HBR) is a subcortical response, elicited by the electrical stimulation of the median nerve. The magnitude of HBR is enhanced when the stimulated hand is close to the face and is modulated by cortical areas according to the perceived threat magnitude (1). This is linked to the representation of the near peripersonal space (PPS) whose boundaries are reshaped following both the evaluation of harm probability, and the ability of the individual to cope with it. However, the PPS is also the space where individuals interact with others (2), either driven by the need for self-protection or seeking affiliation and interpersonal contact, therefore its boundaries must be reshaped accordingly to both the circumstances and the personality tract of the subject. Since PPS and HBR are functionally closely linked, we asked if HBR physiological properties may be modulated by personality tract of the subject. In this study, we assessed distinctively emotional and relational aspects of personality, and evaluated their associations with the HBR response, or lack thereof, in healthy subjects. Seventy-one volunteers filled the Experiences in Close Relationships Scale, the Affective Neuroscience Personality Scales and the State-Trait Anxiety Inventory Form Y questionnaires and underwent HBR recording. Regression analysis was used to assess the association between physiological and psychological variables. We found that the HBR could be evoked only in 50.7% of all subjects (responders). Non-responders subjects showed higher scores in the avoidance dimension and lower scores in the care dimension, compared to responders. In responders, regression analysis showed a negative association of HBR amplitude (difference in near versus far responses) with anger dimension and a positive association with state anxiety. A positive association also emerged with HBR latency and fear dimension and with sensitivity to stimulus intensity and attachment anxiety and anger dimension. We conclude that primary emotional and relational factors may play an important role in the modulation of brainstem circuits mediating the HBR response. This result seems not surprising if we consider that many different neuropsychological factors contribute to the spatial properties of the PPS. It has been shown that PPS representation does not just respond to the presence of others, but it is shaped by the interactions with others, and by the evaluation of other's behavior during social interaction. Further, high-level cognitive processes seem to play an important role in the differentiation between responder and non-responder.