Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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Comparative Study
One hour of tongue-task training is associated with plasticity in corticomotor control of the human tongue musculature.
Corticomotor control of the human tongue has been reported to undergo neuroplastic changes following several days of training in a tongue-protrusion task. The aims of the present study were to determine if a 1 h tongue-task training is sufficient to induce signs of neuroplastic changes in the corticomotor pathways, and to obtain preliminary information on the time course of such changes. Corticomotor excitability was assessed by changes in electromyographic activity evoked by transcortical magnetic stimulation (TMS) in 11 healthy subjects. ⋯ Corticomotor topographic maps revealed increases (ANOVA: P<0.001) in area at the 1 day follow-up. The success rate was significantly correlated to the net increases in tongue MEPs at 1 day follow-up (Spearman: 0.615; P=0.0039). The present findings confirm that tongue task training is associated with plasticity of corticomotor excitability specifically related to the tongue musculature and further document that plasticity is evident within 30 min post-training and may last up to at least 7 days.
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Haemodynamic factors play an important role in the etiology of cerebral lesions in preterm infants. Respiratory distress syndrome (RDS), a common problem in preterms, is strongly related with low and fluctuating arterial blood pressure. This study investigated the relation between mean arterial blood pressure (MABP), fractional cerebral oxygen saturation (ScO2) and fractional (cerebral) tissue oxygen extraction (FTOE), a measure of oxygen utilisation of the brain, during the first 72 h of life. ⋯ ScO2 and FTOE were not different between groups over time, but in RDS infants ScO2 and FTOE had substantial larger variance (P<0.05 at all time points except at 36-48 h for ScO2 and P<0.05 at 12-18, 18-24, 36-48 and 48-60 h for FTOE). During the first 72 h of life, RDS infants showed more periods of positive correlation between MABP and ScO2 (P<0.05 at 18-24, 24-36 36-48 48-60 h) and negative correlation between MABP and FTOE (P<0.05 at 18-24, 36-48 h). Although we found that the patterns of cerebral oxygenation and extraction in RDS infants were not different as compared to infants without RDS, we suggest that the frequent periods with possible lack of cerebral autoregulation in RDS infants may make these infants more vulnerable to cerebral damage.
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Clinical studies have demonstrated that growth hormone (GH) promotes learning and memory processes in GH-deficient (GHD) patients. In animal studies, GH also influences the N-methyl-D-aspartate (NMDA) receptor system in the hippocampus, an essential component of long-term potentiation (LTP), which is highly involved in memory acquisition. This study was designed to examine the beneficial effects of recombinant human GH (rhGH) on cognitive function in male rats with multiple hormone deficiencies resulting from hypophysectomy (Hx). ⋯ Hippocampal mRNA expression of the NMDA subunits NR1, NR2A and NR2B, insulin-like growth factor type 1 receptor (IGF-1R), and postsynaptic density protein-95 (PSD-95) was then measured in the animals by Northern blot analysis. The results suggest that there may be a relationship between the NMDA receptor subunit mRNA expression levels and learning ability, and that learning is improved by rhGH in Hx rats. Furthermore, a link between MWM performance and PSD-95 was also suggested by this study.
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Peripheral sensory-motor neuropathy is one of the most frequent side effects of vincristine (VCR) administration, which often limits its usefulness in the treatment of a wide range of neoplastic diseases. The purpose of this work is to study VCR neurotoxicity in experimental animals from clinical, electrophysiological, and histological points of view. Sixty-five rats were used as a control group and 31 rats were divided into two groups and given VCR in two different regimens: the fixed-dose group (0.2 mg/kg) and the increasing-dose group (0.1 mg/kg, by an increment of 0.05 mg/kg/week). ⋯ The discontinuation of VCR permitted the improvement of the electrophysiological and histological changes. The rat can be used as an animal model for studying VCR neurotoxicity. However, further studies on larger number of animals are required to evaluate the type of nerve fiber involvement and the site of damage.
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Comparative Study Clinical Trial
Blink reflexes in patients with atypical odontalgia and matched healthy controls.
Atypical odontalgia (AO) is an orofacial pain condition which has been suggested to involve neuropathic pain mechanisms. The aim of this study was to use a brain stem reflex to investigate craniofacial nociceptive mechanisms in AO. In 38 AO patients and 27 matched healthy controls, the R2 component of the blink reflex (BR) was elicited using a "nociceptive-specific" electrode and recorded with surface electromyography electrodes on both orbicularis oculi muscles. ⋯ In patients, R2i onset latencies were significantly prolonged compared with controls (P=0.031). The present data show disturbances in the central processing of craniofacial information and that endogenous pain inhibitory systems in AO patients and healthy controls were activated to a similar degree by an acute intraoral nociceptive input. Additional clinical research with AO patients will be needed to determine to what extent neuropathic pain mechanisms are involved in this pain condition.