Desynchronization Responses Research Articles

Moral transgression modulates empathy for pain: Evidence from ERP and EEG data

Empathy for others’ pain plays a critical role in human social interactions; however, the influence of moral transgression remains unclear. We examined the effect of moral transgression on the behavioral and underlying neural processes of empathy for others’ pain. Participants performed a pain-empathy task separately in a moral transgression condition and a neutral behavior condition, while an electroencephalogram was recorded. Event-related potential (ERP) results showed that empathic response, as reflected in the late positive component, was smaller when participants performed the task in the moral transgression condition than in the neutral behavior condition. Time-frequency results also showed decreased empathic effect on the beta event-related desynchronization response in the moral transgression as compared to the neutral behavior condition. However, empathic response as reflected in the N2 component was comparable between the moral conditions. These findings demonstrate a moral transgression effect on both cognitive evaluations and sensorimotor processes of empathy for others’ pain. Furthermore, spontaneous alpha-oscillation power recorded prior to the onset of empathy-inducing stimuli was significantly higher in the moral transgression condition than in the neutral behavior condition. Consequently, differences in sustained attention may be the physiological foundation of the impact of moral transgression of the observed person on the cognitive and sensorimotor processes of empathy for pain.

Changes in the Power Characteristics of the α-Rhythm in Students with Different Levels of Anxiety in Normal Sleep and Partial Deprivation Solving the Go/NoGo Problem

The effect of partial sleep deprivation on cognitive control was studied in 26 students with different levels of trait anxiety. The synchronization–desynchronization reactions of the EEG α-oscillations were evaluated during the Go/NoGo test. In less anxious students, a reduction in sleep time on the night before the study led to a decrease in the desynchronization response to a positive conditioning stimulus (Go) and thus smoothed out the differences with the response to a stimulus that inhibited the behavioral response (NoGo). The smoothing of the α-rhythm responses to stimuli of different signal significance after deprivation indicated deterioration of cognitive control in this group. In students with a high level of anxiety, there were no differences in responses to Go/No Go stimuli either after a night’s sleep of normal duration or after a single sharp reduction of it. They probably had a reduced level of cognitive control, and it did not depend on partial sleep deprivation.

Functional decline of the precuneus associated with mild cognitive impairment: Magnetoencephalographic observations.

Mild Cognitive Impairment (MCI) is a border or precursor state of dementia. To optimize implemented interventions for MCI, it is essential to clarify the underlying neural mechanisms. However, knowledge regarding the brain regions responsible for MCI is still limited. Here, we implemented the Montreal Cognitive Assessment (MoCA) test, a screening tool for MCI, in 20 healthy elderly participants (mean age, 67.5 years), and then recorded magnetoencephalograms (MEG) while they performed a visual sequential memory task. In the task, each participant memorized the four possible directions of seven sequentially presented arrow images. Recall accuracy for beginning items of the memory sequence was significantly positively related with MoCA score. Meanwhile, MEG revealed stronger alpha-band (8-13 Hz) rhythm desynchronization bilaterally in the precuneus (PCu) for higher MoCA (normal) participants. Most importantly, this PCu desynchronization response weakened in correspondence with lower MoCA score during the beginning of sequential memory encoding, a time period that should rely on working memory and be affected by declined cognitive function. Our results suggest that deactivation of the PCu is associated with early MCI, and corroborate pathophysiological findings based on post-mortem tissue which have implicated hypoperfusion of the PCu in early stages of Alzheimer disease. Our results indicate the possibility that cognitive decline can be detected early and non-invasively by monitoring PCu activity with electrophysiological methods.

Modulation of thalamocortical oscillations by TRIP8b, an auxiliary subunit for HCN channels

Hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels have important functions in controlling neuronal excitability and generating rhythmic oscillatory activity. The role of tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) in regulation of hyperpolarization-activated inward current, Ih, in the thalamocortical system and its functional relevance for the physiological thalamocortical oscillations were investigated. A significant decrease in Ih current density, in both thalamocortical relay (TC) and cortical pyramidal neurons was found in TRIP8b-deficient mice (TRIP8b−/−). In addition basal cAMP levels in the brain were found to be decreased while the availability of the fast transient A-type K+ current, IA, in TC neurons was increased. These changes were associated with alterations in intrinsic properties and firing patterns of TC neurons, as well as intrathalamic and thalamocortical network oscillations, revealing a significant increase in slow oscillations in the delta frequency range (0.5–4 Hz) during episodes of active-wakefulness. In addition, absence of TRIP8b suppresses the normal desynchronization response of the EEG during the switch from slow-wave sleep to wakefulness. It is concluded that TRIP8b is necessary for the modulation of physiological thalamocortical oscillations due to its direct effect on HCN channel expression in thalamus and cortex and that mechanisms related to reduced cAMP signaling may contribute to the present findings.

Effects of light wavelength on MEG ERD/ERS during a working memory task

We investigated the effects of light wavelengths on cortical oscillatory activity associated with working memory processes. Cortical activity responses were measured using magnetoencephalography (MEG) while participants performed an auditory Sternberg memory task during exposure to light of different wavelength. Each trial of the memory task consisted of four words presented as a memory set and one word presented as a probe. All words were presented audibly. Participants were instructed to indicate whether the probe word was or was not presented within the memory set. A total of 90 trials were conducted under the light exposure. Event-related synchronization (ERS) and event-related desynchronization responses in the alpha frequency range during the task were analyzed. Results showed that, during memory encoding, ERS responses were significantly greater in the short-wavelength (blue) light condition than in the middle-wavelength (green) light condition, approximately 20–30min after the onset of light exposure. Behavioral performance was very high throughout the experiment and there was no difference between the light conditions. Although the light effects were not observed in behavior, the result of ERS suggests that 20–30min of exposure to blue light enhances cortical activity related to active memory maintenance and/or attention to auditory stimuli.

Individual typological features in the EEG of athletes after acute hypoxic treatment

In athletes with different types of physical training and various temperaments, variability of the main rhythms of the EEG (α, β, and θ) and the parameters of the desynchronization response of the α-rhythm, the individual extent of the decrease in the power of the α-rhythm during eye opening under the conditions of hypoxia growing from 20.9 to 10% of O2 were studied. Twenty-four 18- to 26-year-old athletes, including 11 swimmers and 13 skiers, were involved in the study. We found that, in contrast to normoxia conditions, hypoxia was associated with the instability of the spectrum of the EEG rhythms and phasic changes during a 25-min hypoxia. The EEG response during hypoxia depended on individual typological features estimated using Strelau’s temperament questionnaire. Negative correlation between the psychological construct “endurance” measured using the FCB-TI questionnaire (Formal Characteristics of Behavior-Temperament Inventory) and the power of the EEG α-rhythm was found. The parameters of training and the features of the respiration pattern that appeared as a consequence of training modulated the sensitivity of brain structures to hypoxia, which was reflected in the changes in the EEG α-rhythm under hypoxia conditions.

Brain oscillatory responses during the different stages of an auditory memory search task in children

We assessed brain oscillatory responses of the 4-30 Hz electroencephalographic frequency bands in children (mean age 13 years) during the different stages of an auditory memory search, namely the encoding of four words and recognition of the positive and negative probe words. In children, theta (approximately 4-6 Hz) electroencephalographic responses during recognition were of greater magnitude than those during encoding and alpha (approximately 8-12 Hz) event-related synchronization responses during encoding increased with increasing memory load. During recognition, greater magnitude alpha and beta (>12 Hz) event-related desynchronization responses were observed during the presentation of the positive probe as compared with the negative. Complex patterns of theta, alpha and beta frequency brain oscillatory responses during auditory information processing are present already in children of age approximately 13 years.

Effects of Sleep Deprivation on Awakening Thresholds and Sensory Evoked Potentials in the Rat

The EEG desynchronization response to stimuli presented during slow-wave sleep was studied in 25 chronically implanted rats after 12 hr of sleep deprivation and during control periods of normal sleep. Compared to normal sleep, sleep after deprivation was accompanied by a significant decrease in the number of EEG desynchronization responses to auditory stimuli and by an additional disproportionate decrease in the number of sustained desynchronization responses. Thalamic auditory evoked potentials were not reduced in amplitude during postdeprivation sleep, thus the decrease in number of EEG desynchronization responses to the auditory stimuli was apparently not mediated by decreased responsiveness in the peripheral auditory system. On the other hand, postdeprivation sleep was not accompanied by any significant change in total number of EEG desynchronization responses to direct trigeminal nerve stimulation nor by any change in the duration of responses to trigeminal stimulation. The results suggest that recovery from sleep loss in accompanied not by a nonspecific increase in the threshold for arousal per se but instead by a selective increase in the threshold for arousal to certain classes of peripheral stimuli.

A chronic experimental study to compare the electrocorticogram of certain brain areas in the drowsy cat

The spontaneous electrocorticogram of the first somatosensory (area 53), first auditory (area 22), visual (area 17), association (area 5), and second auditory (area 52) projection areas was studied in chronic experiments on drowsy unanesthetized cats. In the intermediate periods between waking and sleep and vice versa, maximal differences expressed as heterogeneity of the spindle component and low coefficients of cross correlation (0.21±0.04) were found in the slow-wave activity of the areas studied. During deepening of sleep the synchronization of the potentials recorded from the different areas increased and the coefficients of cross correlation rose to 0.40±0.18. The level of differences between the coefficients of correlation compared in the different phases of sleep was 0.19 and was significant by Student's criterion. It is postulated that functional changes in the thalamic pacemaker mechanisms take place during changes in the depth of sleep. In response to afferent stimulation of different modalities no differences were found in the desynchronization response in the projection areas. After extinction of the orienting reflexes and application of stimulation of adequate strength, specific differences in the development of the desynchronization response to adequate stimulation were found in the projection zones. The need for certain conditions being present before signs of specificity of the responses in the projection areas can be detected is emphasized.

Newborn responses to nonsignal auditory stimuli: I. Electroencephalographic desynchronization.

ABSTRACTThere are suggestions in the literature that the electroencephalographic (EEG) desynchronization response is in the newborn's repertoire. The present investigation was designed to examine that possibility under stringent experimental conditions. Sixteen normal neonates were presented with a 1‐Sec pure tone or white noise during one episode of quiet sleep and one episode of active sleep. Flat activity during stimulated quiet sleep was compared with spontaneous periods of low voltage activity during a nonstimulated quiet sleep episode. Comparisons were also made between responses in quiet sleep with and without prior stimulation in active sleep. Habituation and dishabituation were studied by presenting the nonfamiliar stimulus after repetition of the original stimulus. Increased EEG desynchronization to stimulation was found but the response appears to be a complex function of the type of stimulus, recording location, stimulus repetition, and the prior experience variable. The results have implications for differential maturation of the brain, the perceptual capacities of the neonate, and the controversy over orientation in the newborn.

Some characteristics of stimulus-provoked alpha activity

Two groups of subjects, pre-selected for prominent resting alpha, were studied in order to assess the habituation of EEG reactivity to repeated photic stimuli. In one group, the subjects passively received the signals; in the other they were instructed to respond manually as soon as the signal was detected, and the reaction times were measured. It was found that the EEG background of alpha activity tended to alternate with a lower voltage, more random pattern sometimes including slow waves in both groups. The EEG reactivity against the latter background was that of provocation of alpha activity, whereas against the background alpha rhythm, the reactivity was that of blocking or arrest of alpha. From the point in each record in which these patterns began to alternate, it was found that the alpha provocation response had a higher incidence than the desynchronization response, significantly so only for the group not required to respond. The blocking response was relatively habituated for both groups. The requirement of a motor response to the photic signal was associated with an increased incidence of the alpha blocking response. Reaction times tended to be higher when alpha provocation occurred. The hypothesis was advanced that stimulation-provoked alpha activity may be an electrical sign of central inhibitory processes.

Differential electroencephalographic response to conditioned auditory stimuli in arousal from sleep

Six cats with implanted electrodes, classically conditioned to paired sound and shock, demonstrated differential EEG desynchronization on a background of EEG synchrony associated with behavioral sleep. This phenomenon was used to demonstrate auditory discrimination in sleep of (1) sounds of differing quality, (2) tones of differing frequency, (3) mixtures of frequencies presented in reciprocal relationship (4) number of stimuli and (5) subtraction of external stimulation in contrast to addition. The neutral stimuli were seen to enhance EEG synchrony in simple discriminations. The conditioned EEG desynchronization response was seen to occur on many occasions in the absence of any motor manifestation of arousal. Removal of most, but not all cortex implicated in auditory function (AI, AII, and Ep) failed to alter simple discriminations, but impaired the complex ones.