Neuroreport
-
Afferent fibers innervating the gastrointestinal tract have major roles in consciously evoked sensations including pain. We reported previously that the activation of ERK1/2, a member of the mitogen-activated protein kinase (MAPK) family, in primary sensory neurons was involved in acute visceral pain. Moreover, we also revealed that this activation of ERK1/2 occurred through transient receptor potential (TRP) A1, a member of the TRP family of ion channels. ⋯ Intrathecal administration of the p38 inhibitor, SB203580, attenuated the electromyographic response to noxious GD. Furthermore, intrathecal administration of TRPA1 antisense oligodeoxynucleotide decreased the p38 activation in DRG neurons. The activation of p38 pathways in DRG neurons by noxious GD may be correlated with the activation state of the primary afferent neurons through TRPA1, and further, involved in the development of visceral pain.
-
It is known that transcranial direct current stimulation (tDCS) can induce polarity-specific shifts in brain excitability of the primary motor cortex (M1) with anodal tDCS enhancing and cathodal tDCS reducing cortical excitability. However, less is known about its impact on specific intracortical inhibitory mechanisms, such as γ-aminobutyric acid B (GABAB)-mediated inhibition. Consequently, the aim of the present study was to assess the impact of anodal and cathodal tDCS on M1 intracortical inhibition in healthy individuals. ⋯ This study provides evidence that anodal tDCS, presumably by synaptic plasticity mechanisms, has a direct effect on GABAB-meditated inhibition assessed by the CSP, but not by LICI. Our results further suggest that CSP and LICI probe distinct intracortical inhibitory mechanisms as they are differentially modulated by anodal tDCS. Finally, these data may have clinical value in patients in whom a pathological increase in CSP duration is present, such as schizophrenia.
-
It is well known that emotion can modify the experience of pain. However, it is unclear how an emotional state and its concomitant neural activity affects activity in brain regions responsive to pain, thus altering the experience of pain itself. In this study, we examined the effect of sad mood on perception of painful stimuli and used functional MRI (fMRI) to identify neural activity changes in 15 participants who, in separate trials, (a) received painful electric shocks; (b) experienced a sad mood; and (c) received electric shocks as they were experiencing a sad mood. ⋯ The 'pain-processing' areas included the secondary somatosensory cortex and the adjacent posterior insula (pIn/SII) as well as periaqueductal gray. The 'emotional-processing' regions included the subgenual cingulate cortex and the amygdala. On the basis of these results, we suggest that increased activation in the pIn/SII is part of a top-down system of pain facilitation that includes the anterior cingulate cortex, amygdala, and periaqueductal gray.
-
Sleep deprivation affects cerebral metabolism and reduces the functional connectivity among various regions of the brain, potentially explaining some of the associated mood and emotional changes often observed. Prior neuroimaging studies have only examined the effects of sleep deprivation or partial sleep restriction on functional connectivity, but none have studied how such connectivity is associated with normal variations in self-reported sleep duration the night before the scan. We examined the relationship between sleep duration and resting state functional connectivity among healthy volunteers who slept at home according to their own schedules. ⋯ Seed regions were placed in the medial prefrontal cortex and posterior cingulate cortex nodes of the default mode network, regions previously implicated in sleep deprivation. Longer self-reported sleep duration was associated with significantly enhanced functional connectivity between the medial prefrontal cortex and posterior cingulate, as well as greater anticorrelations with parietal, occipital, and lateral prefrontal regions. Findings suggest that even normal variations in sleep duration measured by self-report are related to the strength of functional connectivity within select nodes of the default mode network and its anticorrelated network.
-
Randomized Controlled Trial
Age-related multisensory integration elicited by peripherally presented audiovisual stimuli.
Although age-related multisensory integration has been investigated previously, the effects of aging on multisensory integration elicited by peripherally presented audiovisual (AV) stimuli remain unclear. In this study, visual, auditory, and AV stimuli were randomly presented to the left or the right of the central fixation point; during this time, participants (young and old adults) were asked to respond promptly to target stimuli. ⋯ We found that the time window of AV behavioral facilitation in elderly participants was longer but more delayed than that in the young participants when the AV stimuli were presented peripherally. This finding also further confirmed that peripheral resolution decreased with age.