The role of sleep and sleep deprivation in consolidating fear memories.

Sleep, in particular REM sleep, has been shown to improve the consolidation of emotional memories. Here, we investigated the role of sleep and sleep deprivation on the consolidation of fear memories and underlying neuronal mechanisms. We employed a Pavlovian fear conditioning paradigm either followed by a night of polysomnographically monitored sleep, or wakefulness in forty healthy participants. Recall of learned fear was better after sleep, as indicated by stronger explicitly perceived anxiety and autonomous nervous responses. These effects were positively correlated with the preceding time spent in REM sleep and paralleled by activation of the basolateral amygdala. These findings suggest REM sleep-associated consolidation of fear memory in the human amygdala. In view of the critical participation of fear learning mechanisms in the etiology of anxiety and post-traumatic stress disorder, deprivation of REM sleep after exposure to distressing events is an interesting target for further investigation.

Boys do it the right way: sex-dependent amygdala lateralization during face processing in adolescents.

Previous studies have observed a sex-dependent lateralization of amygdala activation related to emotional memory. Specifically, it was shown that the activity of the right amygdala correlates significantly stronger with memory for images judged as arousing in men than in women, and that there is a significantly stronger relationship in women than in men between activity of the left amygdala and memory for arousing images. Using a large sample of 235 male adolescents and 235 females matched for age and handedness, we investigated the sex-specific lateralization of amygdala activation during an emotional face perception fMRI task. Performing a formal sex by hemisphere analysis, we observed in males a significantly stronger right amygdala activation as compared to females. Our results indicate that adolescents display a sex-dependent lateralization of amygdala activation that is also present in basic processes of emotional perception. This finding suggests a sex-dependent development of human emotion processing and may further implicate possible etiological pathways for mental disorders most frequent in adolescent males (i.e., conduct disorder).

Parietal modules for reaching.

Optic ataxia (OA) is classically defined as a deficit of visually guided movements that follows lesions of the posterior part of the posterior parietal cortex (PPC). Since the formalisation of the double stream of visual information processing [Milner, A. D., & Goodale, M. A. (1995). The visual brain in action. Oxford: Oxford University Press] and the use of OA as an argument in favour of the involvement of the posterior parietal cortex (dorsal stream) in visually guided movements, many studies have looked at the visuomotor deficits of these patients. In parallel, the development of neuroimaging methods have led to increasing information about the role of the posterior parietal cortex in visually guided actions. In this article, we discuss the similarities and differences in the results that emerged from these two complementary viewpoints by combining a meta-analysis of neuroimaging data on reaching with lesion studies from OA patients and results of our own fMRI study on reaching in the ipsi- and contra-lateral visual field. We identified four bilateral parietal foci from the meta-analysis and found that the more posterior foci showed greater lateralisation for contralateral visual stimulation than more anterior ones Additionally, the more anterior foci showed greater lateralisation for the use of the contralateral hand than the more posterior ones. Therefore, we can demonstrate that they are organised along a postero-anterior gradient of visual-to-somatic information integration. Furthermore, from the combination of imaging and lesion data it can be inferred that a lesion of the three most posterior foci responsible for the target-hand integration could explain the hand and field effect revealed in OA reaching behaviour.