α-Band activity tracks a two-dimensional spotlight of attention during spatial working memory maintenance

A substantial body of work has shown that patterns of EEG α-band activity track the angular coordinates of attended and remembered stimuli around fixation, but whether these patterns track the two-dimensional coordinates of stimuli presented within a visual hemifield remains an open question. Here, we demonstrate that α-band activity tracks the two-dimensional coordinates of remembered stimuli within a hemifield, showing that α-band activity reflects a spotlight of attention focused on locations maintained in working memory.

Region-Specific Effects of 10-Hz Transcranial Alternate Current Stimulation Over the Left Posterior Parietal Cortex and Primary Somatosensory Area on Tactile Two-Point Discrimination Threshold

Changes in α-band cortical oscillatory activity (8–13 Hz) affect perception; however, how these changes in the left posterior parietal cortex (PPC) and primary somatosensory cortex (S1), which play different roles in determining the two-point discrimination (TPD) threshold, affect TPD threshold remains unelucidated. Therefore, to determine TPD threshold, we aimed to investigate the function of the left PPC and S1 by applying α-band transcranial alternating current stimulation (α-tACS; 10 Hz). TPD threshold was examined at the pad of the right index finger, contralateral to the stimulation site, in 17 healthy adults using a custom-made, computer-controlled, two-point tactile stimulation device, with random application of either active or sham α-tACS over the left PPC (Experiment 1) and left S1 (Experiment 2). Then, 50% TPD threshold was obtained in the active and sham conditions via logistic regression analysis. Afterward, we compared the difference between the active and sham conditions at 50% TPD threshold in each region and found that α-tACS reduced TPD threshold when applied over the left PPC (P = 0.010); however, its effect was insignificant when applied over the left S1 (P = 0.74). Moreover, a comparison of the change in 50% TPD threshold among the regions revealed that α-tACS applied over the left PPC significantly reduced TPD threshold compared with that applied over the left S1 (P = 0.003). Although we did not reveal the actual changes in cortical activity induced by α-tACS, this is the first empirical evidence that α-tACS applied over the left PPC and left S1 exerts region-specific effects on determining TPD threshold assessed in the contralateral index finger pad by stimulation.

Breath hold task induces temporal heterogeneity in electroencephalographic regional field power in healthy subjects

While the brainstem is in charge of the automatic control of ventilation, the cortex is involved in the voluntary control of breathing but also receives inputs from the brainstem, which influence the perception of breathing and the arousal state and sleep architecture in conditions of hypoxia/hypercapnia. We evaluated in eleven healthy subjects the effects of breath hold (BH: 30 seconds of apneas and 30 seconds of normal breathing) and BH-related CO2/O2 changes on electroencephalogram (EEG) global field power (GFP) and regional field power (RFP) in 9 different areas (3 rostrocaudal sections -anterior, central, posterior- and 3 sagittal sections -left, middle, right) in the δ and α bands, by cross correlation analysis. No significant differences were observed in GFP and RFP when comparing free breathing (FB) with the BH task. Within the BH task, the shift from apnea to normal ventilation was accompanied by an increase in the δ power and a decrease in the α power. The end-tidal pressure of CO2 (PETCO2) was positively correlated with the δ-band and negatively with the α- band with a positive time shift, while an opposite behaviour was found for the end-tidal pressure of O2 (PETO2). Notably, the time shift between PETCO2/PETO2 signals and cortical activity at RFP was heterogenous and seems to follow a hierarchical activation with the δ-band responding earlier than the α band. Overall, these findings suggest that the effect of BH on the cortex may follow specific ascending pathways from the brainstem and be related to chemoreflex stimulation.

Acute spontaneous intracerebral hemorrhage lethal outcome prediction on the ground of bioelectrical brain activity spectral analysis

Aim of the study — to detect electroencephalographic criteria of unfavorable vital outcome of spontaneous supratentorial intracerebral hemorrhage (SSICH). Prospective cohort study of 156 patients (mean age 66,7 ± 0.8 years) in acute period of SSICH on the ground of conservative treatment. Diagnosis was made based on clinical neurological and visualization data. Bioelectrical brain activity was done during first 2 days of the onset. Logistic regressive analysis was used for elaboration of prognostic criteria. It was detected, that risk of lethal SSICH outcome is independently associated with the next spectral EEG‑pattern parameters: relative spectral rhythm of δ-band of intact hemisphere (odds ratio (OR) (95 % confidence interval (CI) is equal to 1.12 (1.08—1.17), p < 0.0001), frontal occipital rhythm gradient of α-band of intact hemisphere (ОR (95 % CI) = 5,96 (1.08—33.04), p = 0.0410) and interhemispheric asymmetry of absolute spectral rhythm power of β2-band (OR (95 % CI) = 0.03 (0.001—0.88), p = 0.0419). These predictors were integrated into the mathematic model for individual prognosis of SSICH lethal outcome (AUC (95 % CI) = 0.95 (0.90—0.98), p < 0.0001, predictive accuracy is equal to 89.7 %). Bilateral predominance of electroencephalographic pattern of δ-band rhythm, inversion of negative frontal occipital rhythm gradients of α-band in both hemispheres, formation of negative interhemispheric asymmetry of absolute spectral rhythm power of δ-band, α2-band in frontal region and θ-, β-bands in parietal occipital regions in first 2 days from the SSICH onset are the EEG criteria for unfavorable vital outcome of SSICH.

Left hemispheric α band cerebral oscillatory changes correlate with verbal memory

Event-related synchronisation (ERS) and event-related desynchronisation (ERD) have been observed via magnetoencephalography (MEG) in the language-dominant hemisphere. However, the relationship between ERS/ERD and clinical language indices is unclear. Therefore, the present study evaluated brain activity utilising MEG during a verb generation task in 36 subjects and determined ERS/ERD power values in θ, α, β, low γ and high γ frequency bands. To measure clinical language indices, we adopted Wechsler Memory Scale-revised. We observed ERD in the α band from the bilateral occipital to the left central brain region, in the β band from the bilateral occipital to the left frontal region and in the low γ band a high-power signal in the left frontal region. We also observed ERS in the θ band in bilateral frontal region and in the high γ band in bilateral occipital region. Furthermore, we found a significant negative correlation between α-band ERD power at the left postcentral gyrus and medial superior frontal gyrus and verbal memory score (correlation coefficients = − 0.574 and − 0.597, respectively). These results suggest that individuals with lower linguistic memory have less desynchronised α-band ERD power and α-band ERD power in the left hemisphere may be a neurophysiological biomarker for verbal memory.

Formation and material supply of an active-region filament associated with newly emerging flux

ABSTRACT With the observations of Solar Dynamics Observatory(SDO)/Atmospheric Imaging Assembly (AIA) 304 $\rm \mathring{\rm A}$ and New Vacuum Solar Telescope (NVST) H α bands, we present the formation of an active-region filament in active region NOAA 11903 during the period from 02:00 to 10:00 ut on 2013 November 25. A series of jets occurring in the vicinity of the south-western footpoint of the filament directly ejected cool and hot plasmas to filament height and supplied material for the filament. Some newly emerging flux is found in the vicinity of the south-western footpoint of the filament during these jets. In this paper, we mainly focus on the material supply for the formation of the filament. The plasma mass uploaded by the jets and the mass of the filament are estimated, which manifest the fact that the mass carried by the jets can supply sufficient material for the formation of the filament. We found two types of jets; one is H α jet, and the other is EUV jet. The significant finding is that some cool jets seen in the H α band but not in the SDO/AIA bands could also eject the cool material for the filament. These results suggest that cool plasma in the low atmosphere can be directly injected into the upper atmosphere and become the filament material by two types of jets. Moreover, the newly emerging flux with the non-potential field plays an important role in the appearance of the jets and the magnetic structure of the filament.