Psychological and physiological evidence for an initial 'Rough Sketch' calculation of personal space.

Personal space has been defined as "the area individuals maintain around themselves into which others cannot intrude without arousing discomfort". However, the precise relationship between discomfort (or arousal) responses as a function of distance from an observer remains incompletely understood. Also the mechanisms involved in recognizing conspecifics and distinguishing them from other objects within personal space have not been identified. Accordingly, here we measured personal space preferences in response to real humans and human-like avatars (in virtual reality), using well-validated "stop distance" procedures. Based on threshold measurements of personal space, we examined within-subject variations in discomfort-related responses across multiple distances (spanning inside and outside each individual's personal space boundary), as reflected by psychological (ratings) and physiological (skin conductance) responses to both humans and avatars. We found that the discomfort-by-distance functions for both humans and avatars were closely fit by a power law. These results suggest that the brain computation of visually-defined personal space begins with a 'rough sketch' stage, which generates responses to a broad range of human-like stimuli, in addition to humans. Analogous processing mechanisms may underlie other brain functions which respond similarly to both real and simulated human body parts.

Impact of sleep on complicated grief severity and outcomes.

BACKGROUND: Complicated grief (CG) is characterized by persistent, impairing grief after losing a loved one. Little is known about sleep disturbance in CG. Baseline prevalence of subjective sleep disturbance, impact of treatment on sleep, and impact of mid-treatment sleep on CG and quality of life outcomes were examined in adults with CG in secondary analyses of a clinical trial. METHODS: Patients with CG (n = 395, mean age =53.0; 78% female) were randomized to CGT+placebo, CGT+citalopram (CIT), CIT, or placebo. Subjective sleep disturbance was assessed by a grief-anchored sleep item (Pittsburgh Sleep Quality Index: PSQI-1) and a four-item sleep subscale of the Quick Inventory of Depressive Symptomatology (QIDS-4). Sleep disturbance was quantified as at least one QIDS-4 item with severity ≥2 or grief-related sleep disturbance ≥3 days a week for PSQI-1. Outcomes included the Inventory of Complicated Grief (ICG), Work and Social Adjustment Scale (WSAS), and Clinical Global Impressions Scale. RESULTS: Baseline sleep disturbance prevalence was 91% on the QIDS-4 and 46% for the grief-anchored PSQI-1. Baseline CG severity was significantly associated with sleep disturbance (QIDS-4: p = .015; PSQI-1: p = .001) after controlling for comorbid depression and PTSD. Sleep improved with treatment; those receiving CGT+CIT versus CIT evidenced better endpoint sleep (p = .027). Mid-treatment QIDS-4 significantly predicted improvement on outcome measures (all p < .01), though only WSAS remained significant after adjustment for mid-treatment ICG (p = .02). CONCLUSIONS: Greater CG severity is associated with poorer sleep beyond PTSD and depression comorbidity. Additional research including objective sleep measurement is needed to optimally elucidate and address sleep impairment associated with CG.