Experimental hand pain delays recognition of the contralateral hand: Evidence that acute and chronic pain have opposite effects on information processing?

Recognising the laterality of a pictured hand involves making an initial decision and confirming that choice by mentally moving one's own hand to match the picture. This depends on an intact body schema. Because patients with complex regional pain syndrome type 1 (CRPS1) take longer to recognise a hand's laterality when it corresponds to their affected hand, it has been proposed that nociceptive input disrupts the body schema. However, chronic pain is associated with physiological and psychosocial complexities that may also explain the results. In three studies, we investigated whether the effect is simply due to nociceptive input. Study one evaluated the temporal and perceptual characteristics of acute hand pain elicited by intramuscular injection of hypertonic saline into the thenar eminence. In studies two and three, subjects performed a hand laterality recognition task before, during, and after acute experimental hand pain, and experimental elbow pain, respectively. During hand pain and during elbow pain, when the laterality of the pictured hand corresponded to the painful side, there was no effect on response time (RT). That suggests that nociceptive input alone is not sufficient to disrupt the working body schema. Conversely to patients with CRPS1, when the laterality of the pictured hand corresponded to the non-painful hand, RT increased similar to 380 ms (95% confidence interval 190 ms-590 ms). The results highlight the differences between acute and chronic pain and may reflect a bias in information processing in acute pain toward the affected part.

The development of self-recognition in mirrors and live videos

By 24-months of age most children show mirror self-recognition. When surreptitiously marked on their forehead and then presented with a mirror, they explore their own head for the unexpected mark. Here we demonstrate that self-recognition in mirrors does not generalize to other visual feedback. We tested 80 children on mirror and live video versions of the task. Whereas 90% of 24-month olds passed the mirror version, only 35% passed the video version. Seventy percent of 30-month olds showed video selfrecognition and only by age 36-months did the pass rate on the video version reach 90%. It remains to be y 24-months of age most children show mirror self-recognition. When surreptitiously marked on their forehead and then presented with a mirror, they explore their own head for the unexpected mark. Here we demonstrate that self-recognition in mirrors does not generalize to other visual feedback. We tested 80 children on mirror and live video versions of the task. Whereas 90% of 24-month olds passed the mirror version, only 35% passed the video version. Seventy percent of 30-month olds showed video selfrecognition and only by age 36-months did the pass rate on the video version reach 90%. It remains to be