Journal of neurophysiology
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Several studies provided evidence that the amplitudes of laser-evoked potentials (LEPs) are modulated by attention. However, previous reports were based on across-trial averaging of LEP responses at the expense of losing information about intertrial variability related to attentional modulation. The aim of this study was to investigate the effects of somatosensory spatial attention on single-trial parameters (i.e., amplitudes, latencies, and latency jitter) of LEP components (N2 and P2). ⋯ Conversely, the latency jitter of the P2 component was smaller for ULS compared with ALS. With the use of single-trial analysis, the study provided new insights into brain dynamics of LEPs related to spatial attention. Our results indicate that single-trial parameters of LEP components are differentially modulated by spatial attention.
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Motor cortex (MCX) motor representation reorganization occurs after injury, learning, and different long-term stimulation paradigms. The neuromodulatory approach of transspinal direct current stimulation (tsDCS) has been used to promote evoked cortical motor responses. In the present study, we used cathodal tsDCS (c-tsDCS) of the rat cervical cord to determine if spinal cord activation can modify the MCX forelimb motor map. ⋯ Cervical c-tsDCS more strongly enhanced forelimb than hindlimb motor representation and had no effect on vibrissal representation. The finite-element model indicated current density localized to caudal cervical segments, informing forelimb motor selectivity. Our results suggest that c-tsDCS augments spinal excitability in a spatially selective manner and may improve voluntary motor function through MCX representational plasticity.
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Each half of the medulla contains respiratory neurons that constitute two generators that control respiratory rhythm. One generator consists of the inspiratory neurons in the pre-Bötzinger complex (preBötC); the other, the pre-inspiratory (Pre-I) neurons in the parafacial respiratory group (pFRG), rostral to the preBötC. We investigated the contribution of the commissural fibers, connecting the respiratory rhythm generators located on the opposite side of the medulla to the generation of respiratory activity in brain stem-spinal cord preparation from 0- to 1-day-old rats. ⋯ The facial and contralateral L1 nerve activities were synchronous, whereas right and left facial (and right and left L1) nerves lost synchrony. Optical recordings demonstrated that pFRG-driven burst activity was preserved after a midline section, whereas the preBötC neurons were no longer rhythmic. We conclude that in newborn rats, crossed excitatory interactions (via commissural fibers) are necessary for the generation of inspiratory bursts but not for the generation of rhythmic Pre-I neuron activity.
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Rats use rhythmic whisker movements, called active whisking, to sense the environment, which include whisker protractions followed by retractions at various frequencies. Using a proxy of active whisking in anesthetized rats, called artificial whisking, which is induced by electrically stimulating the facial motor nerve, we characterized the neural responses evoked in the barrel cortex by whisking in air (without contact) and on a surface (with contact). Neural responses were compared between distinct network states consisting of cortical deactivation (synchronized slow oscillations) and activation (desynchronized state) produced by neuromodulation (cholinergic or noradrenergic stimulation in neocortex or thalamus). ⋯ The whisking retraction signal codes the duration of the preceding whisker protraction, is present in thalamocortical networks but not in superior colliculus, and is robust during cortical activation; a state associated with natural exploratory whisking. The expression of different whisking signals in forebrain and midbrain may define the sensory processing abilities of those sensorimotor circuits. Whisking related signals in the barrel cortex are controlled by network states that are set by neuromodulators.
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Changes in ion channel function and expression are characteristic of neuropathic pain. Voltage-gated calcium channels (VGCCs) are integral for neurotransmission and membrane excitability, but relatively little is known about changes in their expression after nerve injury. In this study, we investigate whether peripheral nerve ligation is followed by changes in the density and proportion of high-voltage-activated (HVA) VGCC current subtypes in dorsal root ganglion (DRG) neurons, the contribution of presynaptic N-type calcium channels in evoked excitatory postsynaptic currents (EPSCs) recorded from dorsal horn neurons in the spinal cord, and the changes in expression of mRNA encoding VGCC subunits in DRG neurons. ⋯ No changes were found in the contribution of presynaptic N-type calcium channels in evoked EPSCs recorded from dorsal horn neurons. The α2δ-1 subunit was upregulated by 1.7-fold and γ-3, γ-2, and β-4 subunits were all downregulated 1.7-fold in injured neurons compared with sham-operated neurons. This comprehensive characterization of HVA VGCC subtypes in mouse DRG neurons after nerve injury revealed changes in N- and P/Q-type current proportions only in medium- to large-diameter neurons.