Plos One
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A stimulus approaching the body requires fast processing and appropriate motor reactions. In monkeys, fronto-parietal networks are involved both in integrating multisensory information within a limited space surrounding the body (i.e. peripersonal space, PPS) and in action planning and execution, suggesting an overlap between sensory representations of space and motor representations of action. In the present study we investigate whether these overlapping representations also exist in the human brain. ⋯ This pattern of corticospinal modulation highlights the relation between space and time in the pps representation: an early facilitation for near stimuli may reflect immediate motor preparation, whereas, at later time intervals, motor preparation relates to distant stimuli potentially approaching the body.
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Morbidity associated with primary headache disorders is a major public health problem with an overall prevalence of 46%. Tension-type headache and migraine are the two most prevalent causes. However, headache has not been sufficiently studied as a cause of morbidity in the developing world. Literature on prevalence and classification of these disorders in South Asia is scarce. The aim of this study is to describe the classification and clinical features of headache patients who seek medical advice in Pakistan. ⋯ Patients who seek medical advice for headache in Pakistan are usually in their most productive ages. Migraine and tension-type headache are the most common clinical presentations of headache. Onset of migraine is earlier in patients with first-degree family history. Menstrually related migraine affects women with headache episodes of longer duration than other patients and it warrants special therapeutic consideration. Follow-up studies to describe epidemiology and burden of headache in Pakistan are needed.
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The spontaneous component of neuropathic pain (NP) has not been explored sufficiently with neuroimaging techniques, given the difficulty to coax out the brain components that sustain background ongoing pain. Here, we address for the first time the correlates of this component in an fMRI study of a group of eight patients suffering from diabetic neuropathic pain and eight healthy control subjects. Specifically, we studied the functional connectivity that is associated with spontaneous neuropathic pain with spatial independent component analysis (sICA). ⋯ In conclusion, we have characterized here for the first time a functional network of brain areas that mark the spontaneous component of NP. Pain is the result of aberrant default mode functional connectivity.
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Nitric oxide (NO) can induce acute pain in humans and plays an important role in pain sensitization caused by inflammation and injury in animal models. There is evidence that NO acts both in the central nervous system via a cyclic GMP pathway and in the periphery on sensory neurons through unknown mechanisms. It has recently been suggested that TRPV1 and TRPA1, two polymodal ion channels that sense noxious stimuli impinging on peripheral nociceptors, are activated by NO in heterologous systems. ⋯ We show that BH4-induced calcium influx is ablated in DRG neurons from TRPA1/TRPV1 double knockout mice, suggesting that production of endogenous levels of NO can activate these ion channels. In behavioral assays, peripheral NO-induced nociception is compromised when TRPV1 and TRPA1 are both ablated. These results provide genetic evidence that the peripheral nociceptive action of NO is mediated by both TRPV1 and TRPA1.
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The hippocampus plays a central role in memory formation in the mammalian brain. Its ability to encode information is thought to depend on the plasticity of synaptic connections between neurons. In the pyramidal neurons constituting the primary hippocampal output to the cortex, located in area CA1, firing of presynaptic CA3 pyramidal neurons produces monosynaptic excitatory postsynaptic potentials (EPSPs) followed rapidly by feedforward (disynaptic) inhibitory postsynaptic potentials (IPSPs). ⋯ Using whole-cell recording in hippocampal slices from adult rats, we find that the efficacy of synaptic transmission from CA3 to CA1 can be enhanced without the induction of classic LTP at the glutamatergic inputs. Taking care not to directly stimulate inhibitory fibers, we show that the induction of GABAergic plasticity at feedforward inhibitory inputs results in the reduced shunting of excitatory currents, producing a long-term increase in the amplitude of Schaffer collateral-mediated postsynaptic potentials. Like classic LTP, disinhibition-mediated LTP requires NMDAR activation, suggesting a role in types of learning and memory attributed primarily to the former and raising the possibility of a previously unrecognized target for therapeutic intervention in disorders linked to memory deficits, as well as a potentially overlooked site of LTP expression in other areas of the brain.