Neuroscience
-
Neurotransmitter and headache target localization in the trigeminal ganglia (TG) might increase the understanding of sites of action, and mechanisms related to headache therapy. The overall aim of the study was to investigate the presence of migraine targets in the TG with particular emphasis on pituitary adenylate cyclase-activating peptide (PACAP) and calcitonin gene-related peptide (CGRP), known to be involved in cranial pain processing, and selected headache targets. Rat- and human TG were processed for immunohistochemistry. ⋯ Occasionally, PACAP-38-positive cells also expressed VPAC1, SNAP25 and SV2-A. VPAC1 was generally detected in SGCs enveloping PACAP-38-positive and -negative neuronal somas. Our study revealed potential sites of actions for anti-headache drugs such as PACAP receptor antagonists, Lasmiditan (5-HT1F agonist) and Botox (blocks exocytosis through SV2-A/SNAP25) in rat and human TG and considerable overlap between species in expression to specific cell types, except for VPAC1 and SNAP25.
-
The vestibular system enables humans to estimate self-motion, stabilize gaze and maintain posture, but these behaviors are impacted by neural noise at all levels of processing (e.g., sensory, central, motor). Despite its essential importance, the behavioral impact of noise in human vestibular pathways is not completely understood. Here, we characterize the vestibular imprecision that results from neural noise by measuring trial-to-trial vestibulo-ocular reflex (VOR) variability and perceptual just-noticeable differences (JNDs) in the same human subjects as a function of stimulus intensity. ⋯ VOR and perceptual imprecision both increased with stimulus intensity and were broadly similar over a range of stimulus velocities, consistent with a common noise source that affects motor and perceptual pathways. This contrasts with differing perceptual and motor stimulus-dependent imprecision in visual studies. Either stimulus-dependent noise or non-linear signal processing could explain our results, but we argue that afferent non-linearities alone are unlikely to be the source of the observed behavioral stimulus-dependent imprecision.
-
Object recognition requires differentiation across different objects and generalization across views of the same object. We previously demonstrated that discrimination of object images at several views without any possibility of association was enough to achieve object recognition within a certain range of viewing angles and confirmed the response tolerance of monkey inferotemporal cells within a similar range of viewing angles. However, neither behavioral object recognition nor electrophysiological response tolerance was complete across views. ⋯ When monkeys were trained to discriminate objects at several views, we found that they could discriminate the trained objects regardless of the eventual change in viewing angle, and confirmed a response tolerance at the population level over a large viewing angle range covering all the viewpoints experienced. At the cell population level, such overtraining leads to significantly higher neural response similarity for views of the same objects than for views of different objects regardless of the extent of viewing angle separation. These results suggest a possible method of view-invariant object recognition development.
-
Motor function can be modulated by transcranial alternating current stimulation (tACS) in alpha, beta, and high-gamma frequencies. However, few studies have investigated tACS-induced behavioral changes in combination with endogenous oscillatory neural activity in detail. Herein, we investigated the effect of tACS on motor learning capacity and endogenous oscillatory neural activity. ⋯ Oscillation analysis revealed a significant increase in beta-band power after 70-Hz tACS but not in the other stimulation groups. Our finding that capacity for motor learning and endogenous oscillatory beta activity were modulated in parallel after 70-Hz tACS suggests that 70-Hz tACS may increase the motor learning capacity by cross-modulating beta oscillatory activity. Because high gamma and beta oscillatory activity have been shown to reflect the activity of excitatory and inhibitory interneuron, our results may derive from the modulation of excitatory and inhibitory interneurons in M1 by 70-Hz tACS.
-
This study aims to investigate the value of diffusion kurtosis imaging (DKI) in assessing microstructural changes associated with cognitive impairment in chronic traumatic brain injury (TBI). At 7 months, six TBI rats and six control rats underwent Morris water maze (MWM) tests, followed by DKI examinations. DKI parameters were measured in bilateral cortex, hippocampus, and callosum. ⋯ Further correlational study showed a positive relationship between MK and NeuN, MD and MBP in ipsilateral cortex, and a negative relationship between MK and Iba-1, MBP in ipsilateral cortex and hippocampus (P < 0.05). The MK in ipsilateral cortex and hippocampus were also correlated with MWM test results (P < 0.05). Our study suggests that DKI could be used to assess the microstructural changes associated with cognitive impairment in chronic TBI.