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Impairments in social cognition contribute significantly to disability in schizophrenia patients (SzP). Perception of facial expressions is critical for social cognition. Intact perception requires an individual to visually scan a complex dynamic social scene for transiently moving facial expressions that may be relevant for understanding the scene. The relationship of visual scanning for these facial expressions and social cognition remains unknown.
Methods
In 39 SzP and 27 healthy controls (HC), we used eye-tracking to examine the relationship between performance on The Awareness of Social Inference Test (TASIT), which tests social cognition using naturalistic video clips of social situations, and visual scanning, measuring each individual's relative to the mean of HC. We then examined the relationship of visual scanning to the specific visual features (motion, contrast, luminance, faces) within the video clips.
Results
TASIT performance was significantly impaired in SzP for trials involving sarcasm (p < 10−5). Visual scanning was significantly more variable in SzP than HC (p < 10−6), and predicted TASIT performance in HC (p = 0.02) but not SzP (p = 0.91), differing significantly between groups (p = 0.04). During the visual scanning, SzP were less likely to be viewing faces (p = 0.0001) and less likely to saccade to facial motion in peripheral vision (p = 0.008).
Conclusions
SzP show highly significant deficits in the use of visual scanning of naturalistic social scenes to inform social cognition. Alterations in visual scanning patterns may originate from impaired processing of facial motion within peripheral vision. Overall, these results highlight the utility of naturalistic stimuli in the study of social cognition deficits in schizophrenia.
The initial management of a trauma patient often involves imaging in the form of x-rays, computed tomography (CT) and other radiographic studies, which expose the patient to ionizing radiation, an entity known to cause tissue injury and malignancy at high doses. The purpose of this study was to use a calculation-based method to determine the radiation exposure of trauma patients undergoing trauma team activation in a Canadian tertiary-care trauma centre.
Methods
A retrospective chart review was conducted using the Nova Scotia Provincial Trauma Registry. All patients age 16 years old and over who underwent trauma team activation between March 1, 2008 and March 1, 2009 were included. Patients who died prior to imaging tests were excluded. Dose reports for each CT were used to calculate a whole-body radiation dose for each patient.
Results
There were 230 trauma team activations during the study period, of which 206 had CT imaging. Data were available for 162 patients. The mean whole-body radiation exposure for all patients was 24.4±10.3 mSv, which may correlate to one additional cancer death for every 100 trauma patients scanned.
Conclusions
Trauma patients are exposed to significant amounts of radiation during their initial trauma work-up, which may increase the risk of fatal cancer. Clinicians who care for these patients must be aware of the radiation exposure, and take measures to limit radiation exposure of trauma patients.