Biology subjects

Al, E.

Publications and source records attributed to Al, E..

2 recordsLinked to original sources

bioRxiv2019

BOLD and EEG Signal Variability at Rest Differently Relate to Aging in the Human Brain

Variability of neural activity is regarded as a crucial feature of healthy brain function, and several neuroimaging approaches have been employed to assess it noninvasively. Studies on the variability of both evoked brain response and spontaneous brain signals have shown remarkable changes with aging but it is unclear if the different measures of brain signal variability - identified with either hemodynamic or electrophysiological methods - reflect the same underlying physiology. In this study, we aimed to explore age differences of spontaneous brain signal variability with two different imaging modalities (EEG, fMRI) in healthy younger (25{+/-}3 years, N=135) and older (67{+/-}4 years, N=54) adults. Consistent with the previous studies, we found lower blood oxygenation level dependent (BOLD) variability in the older subjects as well as less signal variability in the amplitude of low-frequency oscillations (1-12 Hz), measured in source space. These age-related reductions were mostly observed in the areas that overlap with the default mode network. Moreover, age-related increases of variability in the amplitude of beta-band frequency EEG oscillations (15-25 Hz) were seen predominantly in temporal brain regions. There were significant sex differences in EEG signal variability in various brain regions while no significant sex differences were observed in BOLD signal variability. Bivariate and multivariate correlation analyses revealed no significant associations between EEG- and fMRI-based variability measures. In summary, we show that both BOLD and EEG signal variability reflect aging-related processes but are likely to be dominated by different physiological origins, which relate differentially to age and sex.

neuroscience↗

bioRxiv2019

Interactions between cardiac activity and conscious somatosensory perception

Fluctuations in the hearts activity can modulate the access of external stimuli to consciousness. The link between perceptual awareness and cardiac signals has been investigated mainly in the visual and auditory domain. We here investigated whether the phase of the cardiac cycle and the pre-stimulus heart rate influence conscious somatosensory perception. We also tested how conscious detection of somatosensory stimuli affects the heart rate. Electrocardiograms (ECG) of 33 healthy volunteers were recorded while applying near-threshold electrical pulses at a fixed intensity to the left index finger. Conscious detection was not uniformly distributed across the cardiac cycle but significantly higher in diastole than in systole. We found no evidence that the heart rate before a stimulus influenced its detection but hits (correctly detected somatosensory stimuli) led to a more pronounced cardiac deceleration than misses. Our findings demonstrate interactions between cardiac activity and conscious somatosensory perception, which highlights the importance of internal bodily states for sensory processing beyond the auditory and visual domain. Impact StatementIt is highly debated to what extent cardiac activity modulates the access of external stimuli to consciousness. The evidence is inconsistent across sensory modalities and previous research focused at specific intervals within the cardiac cycle. Here, we examined the perception of near-threshold electrical pulses across the entire cardiac cycle. Our results show that conscious somatosensory perception is enhanced during the late phase of the cardiac cycle (at diastole) and associated with a more pronounced cardiac deceleration (as compared to non-detected stimuli). This strengthens the evidence that the physiological state of the body influences how we perceive the world.

neuroscience↗