Experimental Brain Research最新文献

Transspinal stimulation with direct current or at intensities and frequencies that produces intermittent depolarization of motoneurons can be an adjunct treatment strategy for spasticity and recovery of movement in persons with spinal cord injury (SCI). The main objective of this study was to assess changes in neurophysiological biomarkers after multiple sessions of transspinal direct current stimulation (tsDCS) in people with and without SCI. Nine SCI and 10 healthy control subjects received daily cathodal tsDCS over the Thoracic 10 vertebra while supine with an average stimulation intensity of 2.28 ± 0.02 mA. SCI and healthy control subjects received an average of 15 and 10 stimulation sessions, respectively. Before and 1-2 days post intervention, we assessed changes in soleus H-reflex recruitment input-output curves, homosynaptic depression and postactivation depression. tsDCS did not alter the strength of homosynaptic depression in any subject group but reversed postactivation depression to facilitation in AIS D subjects. tsDCS resulted in depression of reflex excitability in both subject groups. No significant changes in clinically assessed hyperreflexia were observed in SCI subjects. The results suggest decreased reflex hyperexcitability without recovery of spinal inhibitory control in the injured human spinal cord after multiple sessions of tsDCS. More systematic investigations on reorganization of spinal and cortical interneuronal networks are needed to delineate the tsDCS-induced neuroplasticity in people with SCI to develop effective treatments.

Evidence has shown the role of brain-derived neurotrophic factor (BDNF) and glycogen synthase kinase-3 beta (GSK-3β) in the pathophysiology of posttraumatic stress disorder (PTSD). The present research explored the role of BDNF and GSK-3β activity in behavioral alterations in adolescent rats exposed to fear conditioning, extinction, and reinstatement. Three footshocks (0.8 mA for 3 s paired with sound 75 dB, 3 s) were delivered to rats. Extinction was done 1 min, or 1 h, or 1 day, or 5 days after conditioning (sound broadcasted for 20 times with no footshocks, 75 dB, 3 s). Reinstatement (one footshock, 0.8 mA, 3 s, with no sound) was done 1 h after extinction. The results showed extinction + reinstatement only in females decreased PTSD-like behaviors (darting was observed only in females). Fear conditioning decreased locomotion and rearing in both sexes, while extinction + reinstatement increased locomotion more effectively in females and rearing only in females. Fear conditioning decreased BDNF and increased GSK-3β more effectively in females, while extinction + reinstatement increased BDNF and decreased GSK-3β more effectively in females. In conclusion, we showed that BDNF and GSK-3β activity in the hippocampus may be involved in behavioral changes induced by fear conditioning and extinction + reinstatement sessions in females. However, it seems that behavioral changes in males may not be directly related to the function of BDNF and GSK-3β, although due to the absence of protein assessment, this conclusion is made with great caution. Additionally, reinstatement may induce a more powerful effect in males, counteracting the potential therapeutic effects of extinction session.

Recent research on binaural beat stimulation has raised the question whether it can improve sustained attention. Neurotypicals and subjects with attention deficits of single gender performed a visual attention task under auditory noise, monoaural and binaural beat stimulation, while recording electroencephalographic activity. We found that subjects with attention deficits perform with longer reaction times than neurotypical subjects. To explore EEG activity, two periods of interest were distinguished: before a correct detection and before a miss, supposed to reflect respectively moments of engagement versus disengagement of attention. Under noise stimulation, neurotypicals have larger frontal ERP-components P300 and α-spectral power and lower parietal [Formula: see text] spectral power ratio in correct trials than in missed trials, whereas subjects with attention deficits show the inverse relation. Moreover, neurotypicals exhibit a negative relation of frontal δ-power and [Formula: see text] ratio in a time window of 6s before targets, whereas subjects with attention deficits show positively related δ- and α-power in this time window. Binaural beats diversify these results. Neurotypical subjects respond with a longer reaction time compared to noise stimulation, while attention-deficit subjects respond equally. Moreover, frontal P300 and α-power and parietal [Formula: see text] ratio resemble corresponding results under noise stimulation, whereas brain activity in subjects with attention deficits is rather heterogeneous. In addition, in attention-deficit subjects frontal and parietal δ- and α-power are positively related in a 6s time window before targets. In sum, under noise stimulation we found behavioral and electrophysiological biomarkers, which were inverse in neurotypicals and subjects with attention deficits. Binaural beats break up these relations in both subject groups and they have not been found to be beneficial, neither in behavior nor in electrophysiological biomarkers.

Previous findings revealed that social ostracism reduces people's sense of agency and body ownership, and vicarious ostracism reduces agency. Given theoretical claims that other's and own behavior may be cognitively represented similarly, we compared the impact of first-hand and vicarious social ostracism on agency and ownership, using both explicit and implicit measures. Participants were separated into target group and observer group, to experience first-hand or vicarious ostracism or inclusion. We used a virtual Cyberball game to induce social ostracism or inclusion; and virtual hand illusion, where participants could freely control a virtual hand by moving their real hands, for agency and ownership measurements. Findings show that, both first-hand and vicarious ostracism reduced agency and ownership in both explicit and implicit measures. While the implicit measures were affected by first-hand and vicarious experience equally, the explicit measures showed a stronger reduction of agency and ownership for first-hand than for vicarious experience.

Visual perception is not homogeneous throughout the visual field. Performance is generally better along the horizontal meridian compared to the vertical meridian, and in the lower compared to the upper visual field. These asymmetries in visual performance are reflected in structural asymmetries in early visual cortex. When exploring a visual scene, eye movements occur continuously, with visual perception resulting from a tight interplay between the visual as well as the oculomotor systems. Literature on visual performance across visual fields during saccades is limited, but existing studies show that perceptual performance during saccades is indistinguishable between the upper and the lower visual fields, or altogether better in the upper visual field compared to lower. In the current exploratory study, we asked participants to detect the direction of target displacement across visual fields, while performing a saccade as well as at fixation. During fixation and saccade viewing conditions, performance on the task was better along the horizontal compared to the vertical meridian. However, we did not observe a robust difference in performance between the lower and upper visual field, neither at fixation nor when participants were requested to perform saccades. We interpret our results based on known behavioural and neural anisotropies, as well as considering evolutionary approaches to the perception-action cycle.

This study explores how differences in colors presented separately to each eye (binocular color differences) can be identified through EEG signals, a method of recording electrical activity from the brain. Four distinct levels of green-red color differences, defined in the CIELAB color space with constant luminance and chroma, are investigated in this study. Analysis of Event-Related Potentials (ERPs) revealed a significant decrease in the amplitude of the P300 component as binocular color differences increased, suggesting a measurable brain response to these differences. Four classification models-Support Vector Machines (SVM), EEGNet, Temporal Convolutional Neural Network (T-CNN), and a hybrid CNN-LSTM model were employed to decode EEG data. The highest accuracy reached was 81.93% for binary classification tasks (the largest color differences) and 54.47% for a more nuanced four-class categorization, significantly exceeding random chance. This research offers the first evidence that binocular color differences can be objectively decoded through EEG signals, providing insights into the neural mechanisms of visual perception and forming a basis for developing color-based brain-computer interfaces (BCIs).

Postdiction is a perceptual phenomenon where the perception of an earlier stimulus is influenced by a later one. This effect is commonly studied using the 'rabbit illusion', in which temporally regular, but spatially irregular, stimuli are perceived as equidistant. While previous research has focused on short inter-stimulus intervals (100-200 ms), the role of longer intervals, which may engage late attentional processes, remains unexplored. This study investigates whether postdiction is purely perceptual or also involves attentional mechanisms by using visual stimuli separated by extended intervals. 33 participants (17 females) were assigned to two experimental groups with two different temporal inter-flash intervals (IFI) between stimuli (250 ms: 250-IFI group; 500 ms: 500-IFI). Two stimulation protocols of active transcranial electrical stimulation (tES) and one control condition were tested on the left precuneus/inferior parietal gyrus: (i) transcranial alternating current stimulation (tACS) at the individual alpha frequency (IAF) (IAF-tACS); (ii) transcranial random noise stimulation across the whole alpha band (i.e., 8-12 Hz, Alpha-tRNS) and (iii) a placebo (Sham) stimulation. The postdiction phenomenon was observable in both experimental groups. The participants in the 500-IFI group demonstrated enhanced performance in detecting the illusion during the rabbit illusion task when IAF-tACS was applied. The behavioral results suggest that attentional functions, beyond perceptual ones, play a key role in the postdiction phenomenon.