Bursts of transcranial electrical stimulation increase arousal in a continuous performance test (original) (raw)
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Arousal levels explain inter-subject variability of neuromodulation effects
2020
Over the past two decades, the postulated modulatory effects of transcranial direct current stimulation (tDCS) on the human brain have been extensively investigated, with attractive real-world applications. However, recent concerns on reliability of tDCS effects have been raised, principally due to reduced replicability and to the great interindividual variability in response to tDCS. These inconsistencies are likely due to the interplay between the level of induced cortical excitability and unaccounted individual state-dependent factors. On these grounds, we aimed to verify whether the behavioural effects induced by a common prefrontal tDCS montage were dependent on the participants’ arousal levels. Pupillary dynamics were recorded during an auditory oddball task while applying either a sham or real tDCS. The tDCS effects on reaction times and pupil dilation were evaluated as a function of subjective and physiological arousal predictors. Both predictors significantly explained perf...
Journal of Cognitive Neuroscience, 2008
& Cortical excitability is assumed to depend on cortical arousal level in an inverted U-shaped fashion: Largest (optimal) excitability is usually associated with medium levels of arousal. It has been proposed that under conditions of low arousal, compensatory effort is exerted if attentional demands persist. People tend to avoid this resource-consuming top-down compensation by creating or selecting environmental conditions that provide sufficient bottom-up stimulation. These assumptions were tested in an attention-demanding dual-task situation: We combined a simulated driving task to induce three different arousal levels by varying stimulation (high vs. low vs. self-chosen) with a visual two-stimulus paradigm to assess cortical excitability by the initial contingent negative variation (iCNV) component of the event-related potential. Additionally, we analyzed the oscillatory power of the beta2 band of the electroencephalogram at anterior frontal sites, which is assumed to reflect low-arousal compensatory activity. The iCNV amplitude differed in all three arousal conditions as expected: It was highest in the condition of self-chosen stimulation and lowest in the low-and high-arousal conditions. Additionally, in the low-arousal condition, anterior frontal beta2 power was found to be significantly higher than in the other two conditions and correlated positively with subjective strain. This pattern of results suggests that subjects select medium levels of stimulation which optimize cortical excitability under attentional demand conditions. The elevated fronto-central beta2 power in the low-stimulation condition may indicate the involvement of the anterior cingulate cortex in compensating for reduced arousal by top-down stimulation of the noradrenergic arousal system. &
World Applied Sciences Journal, 2012
The researches have been done so far in order to analyze the effects of arousal and activation on performance, focused merely on unstimulated and normal level, with disparate and contradictory results. The study of manipulation of arousal effect on the performance, results in more in-depth understanding. The purpose of current work is to analyze the impacts of stimulated arousal and activation on simple and discriminative reaction time (RT) performance. 30 non-athlete female university scholars (mean age: 21.3) volunteered to execute simple and discriminative RT tasks in unstimulated (Pre-test) and stimulated (Post-test) arousal states. Their Skin Conductance Level (SCL) was recorded constantly during performance. Multiple linear regression indicated that SCL has no effect on simple and discriminative RT performance in unstimulated and stimulated arousal level; whereas activation, reduces simple RT in stimulated arousal level (p<0.002). In addition, activation reduced discriminative RT in both unstimulated (p<0.022) and stimulated arousal levels (p<0.001). The results confirm the impact of activation on performance as well as emphasizing on the importance of the results obtained from real-life studies.
Psychophysiology, 2008
Electrophysiological studies of human visual perception typically involve averaging across trials distributed over time during an experimental session. Using an oscillatory presentation, in which affective or neutral pictures were presented for 6 s, flickering on and off at a rate of 10 Hz, the present study examined single trials of steady-state visual evoked potentials. Moving window averaging and subsequent Fourier analysis at the stimulation frequency yielded spectral amplitude measures of electrocortical activity. Cronbach's alpha reached values 4.79, across electrodes. Singletrial electrocortical activation was significantly related to the size of the skin conductance response recorded during affective picture viewing. These results suggest that individual trials of steady-state potentials may yield reliable indices of electrocortical activity in visual cortex and that amplitude modulation of these indices varies with emotional engagement.
A cortical locus for modulation of arousal states
bioRxiv (Cold Spring Harbor Laboratory), 2024
Fluctuations in global arousal are key determinants of spontaneous cortical activity and function. Several subcortical structures, including neuromodulatory nuclei like the locus coeruleus (LC), are involved in the regulation of arousal. However, much less is known about the role of cortical circuits that provide top-down inputs to arousal-related subcortical structures. Here, we investigated the role of a major subdivision of the prefrontal cortex, the anterior cingulate cortex (ACC), in arousal modulation. Pupil size, facial movements, heart rate, and locomotion were used as non-invasive measures of arousal and behavioral state. We designed a closed loop optogenetic system based on machine vision and found that real time inhibition of ACC activity during pupil dilations suppresses ongoing arousal events. In contrast, inhibiting activity in a control cortical region had no effect on arousal. Fiber photometry recordings showed that ACC activity scales with the magnitude of spontaneously occurring pupil dilations/face movements independently of locomotion. Moreover, optogenetic ACC activation increases arousal independently of locomotion. In addition to modulating global arousal, ACC responses to salient sensory stimuli scaled with the size of evoked pupil dilations. Consistent with a role in sustaining saliency-linked arousal events, pupil responses to sensory stimuli were suppressed with ACC inactivation. Finally, our results comparing arousal-related ACC and norepinephrinergic LC neuron activity support a role for the LC in initiation of arousal events which are modulated in real time by the ACC. Collectively, our experiments identify the ACC as a key cortical site for sustaining momentary increases in arousal and provide the foundation for understanding corticalsubcortical dynamics underlying the modulation of arousal states. .
Evidence for differentiation of arousal and activation in normal adults
Acta Neurobiologiae Experimentalis, 2007
Arousal at a particular time has been defined as the energetic state at that moment, reflected in electrodermal activity and measured by skin conductance level. In contrast, task related activation has been defined as the change in arousal from a resting baseline to the task situation. The present study, replicating some aspects of a previous investigation of these ideas in children, aimed to further explore whether the separation of arousal and activation was useful in describing state effects on the phasic Orienting Response (OR) and behavioral performance. A continuous performance task (CPT) was used with normal adults. It was found that the magnitude of the mean phasic OR to targets was dependent on arousal, but not on task-related activation. A performance measure (reaction time) improved with increasing activation, but not with arousal. These findings support our previous suggestions concerning the value of conceptualizing arousal and activation as separable aspects of the energetics of physiological and behavioral function.
Personality and Individual Differences, 1989
The frequently observed behavioral effects of the sensation-seeking dimension may be based in a biological substrate involving the reticulocortical activation system and the catecholamine system. Under this theory, high sensation seekers should exhibit elevated levels of psychophysiological arousal as compared with low sensation seekers. Subjects in the present study were exposed to a series of auditory sexual and violent stimuli at three levels of intensity and later required to perform recall and recognition memory tasks involving these stimuli. A vigilance task was also employed. Results showed that phasic electrodermal response amplitude was significantly higher in high than low sensation seekers on a variety of measures, including initial response amplitude and intertrial amplitude. Moreover, the size of these personality group differences increased as a function of increasing stimulus intensity. Findings were interpreted as supporting the theory that high sensation seekers should be more responsive to stimulation as a result of their hypothetically more excitable central nervous systems.
Frontiers in Human Neuroscience, 2015
Perceiving human motion, recognizing actions, and interpreting emotional body language are tasks we perform daily and which are supported by a network of brain areas including the human posterior superior temporal sulcus (pSTS). Here, we applied transcranial direct current stimulation (tDCS) with anodal (excitatory) or cathodal (inhibitory) electrodes mounted over right pSTS (target) and orbito-frontal cortex (reference) while healthy participants performed a bodily emotion recognition task using biological motion pointlight displays (PLDs). Performance (accuracy and reaction times) was also assessed on a control task which was matched to the emotion recognition task in terms of cognitive and motor demands. Each subject participated in two experimental sessions, receiving either anodal or cathodal stimulation, which were separated by one week to avoid residual effects of previous stimulations. Overall, tDCS brain stimulation did not affect the recognition of emotional states from PLDs. However, when emotions with a negative or positive-neutral emotional valence were analyzed separately, effects of stimulation were shown for recognizing emotions with a negative emotional valence (sadness and anger), indicating increased recognition performance when receiving anodal (excitatory) stimulation compared to cathodal (inhibitory) stimulation over pSTS. No stimulation effects were shown for the recognition of emotions with positive-neutral emotional valences. These findings extend previous studies showing structure-function relationships between STS and biological motion processing from PLDs and provide indications that stimulation effects may be modulated by the emotional valence of the stimuli.