Resting State Brain Activity During Long-Term Dry Immersion.

BACKGROUND: The purpose of this work was to investigate the brain's rhythmic activity during a simulated microgravity condition (namely dry immersion). METHODS: During dry immersion, which lasted for 5 d, nine subjects (healthy men, 20 to 29 yr of age) were individually placed in a tub (2.2 × 1.1 × 0.85 m) filled with water (temperature was kept constant at about 33°C). Subject floated in the tub without bodily support in the supine horizontal position, but isolated from the water by waterproof material. Resting state EEGs were registered at the fourth or fifth day of dry immersion. Under the control conditions, resting state EEGs were registered while subjects laid in a supine position on a couch. RESULTS: Compared to the control condition, EEG power in the alpha range (8-13 Hz) was greater in dry immersion; this effect was distributed across the whole scalp. No effects of dry immersion were found for the beta, delta, or theta frequency bands. CONCLUSION: The results of the study, similar to those obtained in a real spaceflight, indicate that support withdrawal is an important contributor to brain activity alterations in weightlessness.Lazarev IE, Tomilovskaya ES, Kozlovskaya IB. Resting state brain activity during long-term dry immersion. Aerosp Med Hum Perform. 2018; 89(7):642-647.

Feature binding in auditory modality requires attention as indexed by mismatch negativity and N2b in an active discrimination task.

Currently, there are two opposing views on feature binding in the auditory modality: according to behavioral studies, this process requires focused attention, whereas electrophysiological studies suggest that feature binding may be fully automatic and independent of attention. Here, we examined whether feature binding depends on higher-level attentional processes by manipulating the attentional focus. We used four auditory stimuli that differed in two features: pitch and location. Two rare deviants could be detected within a sequence of two frequent standards exclusively by feature conjunctions rather than by any single feature alone. Event-related potentials to auditory stimuli were analyzed for four conditions: selective attention to target auditory deviants, selective ignoring of nontarget auditory deviants, nonselective distributed attention to all stimuli within auditory modality, and selective attention diverted from auditory to visual modality. The negative difference (Nd) between event-related potentials to deviants and standards was measured within two time intervals, corresponding to mismatch negativity (100-200 ms) and N2b (200-300 ms). Only under the condition of selective attention to specific feature conjunctions, prominent Nd was observed in mismatch negativity as well in N2b time ranges, whereas no significant Nd was observed in other conditions. As Nd is considered a marker of deviance processing, our results support the view that deviance was not detected unless attention was focused on the stimuli, thus supporting the view that feature binding requires attention.

Distributed feature binding in the auditory modality: experimental evidence toward reconciliation of opposing views on the basis of mismatch negativity and behavioral measures.

Current understanding of feature binding remains controversial. Studies involving mismatch negativity (MMN) measurement show a low level of binding, whereas behavioral experiments suggest a higher level. We examined the possibility that the two levels of feature binding coexist and may be shown within one experiment. The electroencephalogram was recorded while participants were engaged in an auditory two-alternative choice task, which was a combination of the oddball and the condensation tasks. Two types of deviant target stimuli were used - complex stimuli, which required feature conjunction to be identified, and simple stimuli, which differed from standard stimuli in a single feature. Two behavioral outcomes - correct responses and errors - were analyzed separately. Responses to complex stimuli were slower and less accurate than responses to simple stimuli. MMN was prominent and its amplitude was similar for both simple and complex stimuli, whereas the respective stimuli differed from standards in a single feature or two features respectively. Errors in response only to complex stimuli were associated with decreased MMN amplitude. P300 amplitude was greater for complex stimuli than for simple stimuli. Our data are compatible with the explanation that feature binding in auditory modality depends on two concurrent levels of processing. We speculate that the earlier level related to MMN generation is an essential and critical stage. Yet, a later analysis is also carried out, affecting P300 amplitude and response time. The current findings provide resolution to conflicting views on the nature of feature binding and show that feature binding is a distributed multilevel process.

Temperament: an event-related potential study using the oddball paradigm

The present study examined the structure of interrelations between brain event-related potentials and behavioral measures and temperament dimensions during an attention task. Three temperament questionnaires were used: Eysenck Personality Inventory, Strelau Temperament Inventory, and Rusalov Structure of Temperament Questionnaire. Event-related potentials were recorded using the active auditory oddball paradigm. The stimuli (85 dB; 1050 and 1000 Hz sinusoidal tones as targets and non-targets, respectively) were easily discriminated by all of the participants. A complex framework of interrelations between temperament and personality dimensions, behavioral measures, and event-related potentials was found. P3 amplitude was negatively correlated with the number of response omissions. Emotionality was positively correlated with P2 and N1-P2 complex amplitudes. Extraversion and Mobility of Nervous Processes were negatively correlated with the amplitude of the N1-P2 complex, and Social Ergonicity was negatively correlated with N2 latency. The results indicate that Extraversion tends to be associated with both the intensity and temporal aspects of temperament and suggest the importance of using a multidimensional approach in temperament studies...

Temperament: an event-related potential study using the oddball paradigm

The present study examined the structure of interrelations between brain event-related potentials and behavioral measures and temperament dimensions during an attention task. Three temperament questionnaires were used: Eysenck Personality Inventory, Strelau Temperament Inventory, and Rusalov Structure of Temperament Questionnaire. Event-related potentials were recorded using the active auditory oddball paradigm. The stimuli (85 dB; 1050 and 1000 Hz sinusoidal tones as targets and non-targets, respectively) were easily discriminated by all of the participants. A complex framework of interrelations between temperament and personality dimensions, behavioral measures, and event-related potentials was found. P3 amplitude was negatively correlated with the number of response omissions. Emotionality was positively correlated with P2 and N1-P2 complex amplitudes. Extraversion and Mobility of Nervous Processes were negatively correlated with the amplitude of the N1-P2 complex, and Social Ergonicity was negatively correlated with N2 latency. The results indicate that Extraversion tends to be associated with both the intensity and temporal aspects of temperament and suggest the importance of using a multidimensional approach in temperament studies.(AU)