Neuroscience
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Since Ebbinghaus' classical work on oblivion and saving effects, we know that declarative memories may become at first spontaneously irretrievable and only subsequently completely extinguished. Recently, this time-dependent path toward memory-trace loss has been shown to correlate with different patterns of brain activation. Environmental enrichment (EE) enhances learning and memory and affects system memory consolidation. ⋯ At day 21 SC mice do not show preferential exploration of novel object, irrespective of the retraining, while EE mice are still capable to benefit from retraining, even if they were not able to spontaneously recover the trace. Analysis of c-fos expression 20days after learning shows a different pattern of active brain areas in response to the retraining session in EE and SC mice, with SC mice recruiting the same brain network as naïve SC or EE mice following de novo learning. This suggests that EE promotes formation of longer lasting object recognition memory, allowing a longer time window during which saving is present.
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Phonological facilitation (PF) refers to a reduction of naming latencies when a phonologically related word is presented concurrently with the target picture, as compared to the presentation of phonologically unrelated words. According to spread of activation models of word production, this effect arises after lexical selection, during phonetic encoding, and is due to the co-activation of the phonemes shared by the target word and the distracter. Conversely, semantic interference (SI) is characterized by longer naming latencies when semantically related distracters are concurrently presented with the target picture. ⋯ In two experiments, we applied anodal transcranial direct current stimulation (tDCS) over the left superior temporal gyrus (LSTG) and left inferior frontal gyrus (LIFG) before a picture-word interference task in which auditory distracters, which could be phonologically related or unrelated, were presented at a SOA of 150ms or 300ms. While stimulating the LSTG significantly reduced the PF by decreasing RTs in phonologically unrelated trials, anodal tDCS over the LIFG did not affect PF. In line with previous results, our findings support the "activation by competition" model, pointing to inhibition between target and distracters nodes as the mechanism involved in the occurrence of PF and SI.
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The Sonic hedgehog (Shh) signaling pathway is recapitulated in response to ischemic injury. Here, we investigated the clinical implications of Shh protein in the ischemic stroke and explored the underlying mechanism. Intracerebroventricular injection of Shh, Cyclopamine, or anti-vascular endothelial growth factor (VEGF) was performed immediately after permanent middle cerebral artery occlusion (pMCAO) surgery and lasted for 7days (d). ⋯ To observe in vitro angiogenesis, rat brain microvascular endothelial cells (RBMECs) were incubated under oxygen glucose deprivation (OGD) for 6h (h) and treated with Shh/anti-VEGF. We found that (1) Shh improved neurological scores and reduced infarct volume, which was blocked by Cyclopamine, (2) Shh improved the microvascular density and promoted angiogenesis and neuron survival in the ischemic boundary zone, (3) Shh enhanced VEGF expression and VEGF antibody could reverse angiogenic and protective effect of Shh in vivo and in vitro. These data demonstrate that the administration of Shh protein could protect brain from ischemic injury, in part by promoting angiogenic repair.
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The visual system classifies objects into categories, and distinct populations of neurons within the temporal lobe respond preferentially to objects of a given perceptual category. We can also classify the objects we recognize with the sense of touch, but less is known about the neuronal correlates underlying this cognitive function. To address this question, we performed a multivariate pattern analysis (MVPA) of functional magnetic resonance imagining (fMRI) activity to identify the cortical areas that can be used to decode the category of objects explored with the hand. ⋯ Importantly, we found that categories can also be decoded from the lateral occipital complex (LOC), which is a multimodal region known to be related to the representation of object shape. Furthermore, a hyperalignment analysis showed that activity patterns are similar across subjects. Our results thus indicate that tactile object recognition generates category-specific patterns of activity in a multisensory area known to encode objects, and that these patterns have a similar functional organization across individuals.
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Anxiety is differentially expressed across a continuum of stressful/fearful intensity, influenced by endocannabinoid systems and receptors. The hippocampus plays important roles in the regulation of affective behavior, emotion, and anxiety, as well as memory. Location of Cb1/Cb2 receptor action could be important in determining emotional valence, because while the dorsal hippocampus is involved in spatial memory and cognition, the ventral hippocampus has projections to the PFC, BNST, amygdala, and HPA axis, and is important for emotional responses to stress. ⋯ Escape behavior is associated with reduced Cb2 expression in the dorsal CA1 region, with freezing and escape latency correlated with mRNA levels. Escaping and submitting animals with access to running wheels had increased Cb2 mRNA in dorsal DG/CA1. These results suggest that the Cb2 receptor system is rapidly induced during anxiogenic social interactions plus fear conditioning or exercise; with responses potentially adaptive for coping mechanisms.