Long-Distance Amplitude Correlations in the High Gamma Band Reveal Segregation and Integration within the Reading Network

Neural oscillatory synchrony could implement grouping processes, act as an attentional filter, or foster the storage of information in short-term memory. Do these findings indicate that oscillatory synchrony is an unspecific epiphenomenon occurring in any demanding task, or that oscillatory synchrony is a fundamental mechanism involved whenever neural cooperation is requested? If the latter hypothesis is true, then oscillatory synchrony should be specific, with distinct visual processes eliciting different types of oscillations. We recorded magnetoencephalogram (MEG) signals while manipulating the grouping properties of a visual display on the one hand, and the focusing of attention to memorize part of this display on the other hand. Grouping-related gamma oscillations were present in all conditions but modulated by the grouping properties of the stimulus (one or two groups) in the high gamma-band (70–120 Hz) at central occipital locations. Attention-related gamma oscillations appeared as an additional component whenever attentional focusing was requested in the low gamma-band (44–66 Hz) at parietal locations. Our results thus reveal the existence of a functional specialization in the gamma range, with grouping-related oscillations showing up at higher frequencies than attention-related oscillations. The pattern of oscillatory synchrony is thus specific of the visual process it is associated with. Our results further suggest that both grouping processes and focused attention rely on a common implementation process, namely, gamma-band oscillatory synchrony, a finding that could account for the fact that coherent percepts are more likely to catch attention than incoherent ones.

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TUO05 High-gamma band activity of primary hand cortical areas: a sensorimotor feedback efficiency index

Clinical Neurophysiology ◽

10.1016/s1388-2457(08)60054-1 ◽

2008 ◽

Vol 119 ◽

pp. S13

Author(s):

Franca Tecchio ◽

Filippo Zappasodi ◽

Camillo Porcaro ◽

Giulia Barbati ◽

Giovanni Assenza ◽

...

Keyword(s):

Efficiency Index ◽

Gamma Band ◽

Cortical Areas ◽

High Gamma ◽

Gamma Band Activity ◽

Band Activity ◽

Sensorimotor Feedback

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Distinct neurophysiological correlates of the fMRI BOLD signal in the hippocampus and neocortex

10.1101/2021.02.01.429258 ◽

2021 ◽

Author(s):

Paul F. Hill ◽

Sarah E. Seger ◽

Hye Bin Yoo ◽

Danielle R. King ◽

Bradley C. Lega ◽

...

Keyword(s):

Neural Activity ◽

Blood Oxygen Level Dependent ◽

Gamma Band ◽

Bold Signal ◽

Blood Oxygen Level ◽

Indirect Measure ◽

Neural Architecture ◽

High Gamma ◽

Gamma Band Activity ◽

Band Activity

AbstractFunctional magnetic resonance imaging (fMRI) is among the foremost methods for mapping human brain function but provides only an indirect measure of underlying neural activity. Recent findings suggest that the neurophysiological correlates of the fMRI blood-oxygen-level-dependent (BOLD) signal might be regionally specific. We examined the neurophysiological correlates of the fMRI BOLD signal in the hippocampus and neocortex, where differences in neural architecture might result in a different relationship between the respective signals. Fifteen human neurosurgical patients (10 female, 5 male) implanted with depth electrodes performed a verbal free recall task while electrophysiological activity was recorded simultaneously from hippocampal and neocortical sites. The same patients subsequently performed a similar version of the task during a later fMRI session. Subsequent memory effects (SMEs) were computed for both imaging modalities as patterns of encoding-related brain activity predictive of later free recall. Linear mixed-effects modelling revealed that the relationship between BOLD and gamma-band SMEs was moderated by the lobar location of the recording site. BOLD and high gamma (70-150 Hz) SMEs positively covaried across much of the neocortex. This relationship was reversed in the hippocampus, where a negative correlation between BOLD and high gamma SMEs was evident. We also observed a negative relationship between BOLD and low gamma (30-70 Hz) SMEs in the medial temporal lobe more broadly. These results suggest that the neurophysiological correlates of the BOLD signal in the hippocampus differ from those observed in the neocortex.Significance StatementThe blood-oxygen-level-dependent (BOLD) signal forms the basis of fMRI but provides only an indirect measure of neural activity. Task-related modulation of BOLD signals are typically equated with changes in gamma-band activity; however, relevant empirical evidence comes largely from the neocortex. We examined neurophysiological correlates of the BOLD signal in the hippocampus, where the differing neural architecture might result in a different relationship between the respective signals. We identified a positive relationship between encoding-related changes in BOLD and gamma-band activity in frontal, temporal, and parietal cortex. This effect was reversed in the hippocampus, where BOLD and gamma-band effects negatively covaried. These results suggest regional variability in the transfer function between neural activity and the BOLD signal in the hippocampus and neocortex.

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Non-invasive detection of high gamma band activity during motor imagery

Frontiers in Human Neuroscience ◽

10.3389/fnhum.2014.00817 ◽

2014 ◽

Vol 8 ◽

Cited By ~ 15

Author(s):

Melissa M. Smith ◽

Kurt E. Weaver ◽

Thomas J. Grabowski ◽

Rajesh P. N. Rao ◽

Felix Darvas

Keyword(s):

Motor Imagery ◽

Gamma Band ◽

Non Invasive ◽

High Gamma ◽

Gamma Band Activity ◽

Band Activity

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Salat And Brainwave Signal Analysis

Jurnal Teknologi ◽

10.11113/jt.v54.809 ◽

2012 ◽

Cited By ~ 1

Author(s):

W.Mohd Fatihilkamal W.Mohd Ridzwan ◽

Nasrul Humaimi Mahmood ◽

Nor Aini Zakaria ◽

Elia Ameera Ali

Keyword(s):

Signal Analysis ◽

Nervous Activity ◽

Principal Component ◽

Gamma Band ◽

Eeg Signal ◽

Autonomic Nervous System Dysfunction ◽

Autonomic Nervous ◽

High Gamma ◽

Spectrum Distribution ◽

Age Range

Solat adalah salah satu cara umat Islam untuk mengabdikan diri kepada Allah. Kajian ini bertujuan untuk mengkaji kesan selepas solat terhadap otak dengan menggunakan Electroencephalograph(EEG) dan kegiatan saraf autonomik. Sebanyak 20 sampel isyarat EEG daripada 5 responden (lelaki berumur di antara 22 hingga 23 tahun) dipilih, dan mereka bebas daripada masalah jantung, paru–paru, metabolik dan penyakit lain yang boleh menggangu kegiatan saraf autonomik. Analisa dilakukan dengan membuat perbandingan di antara sampel EEG bagi dua aktiviti berbeza iaitu aktiviti selepas solat dan aktiviti selepas mendengar muzik menggunakan kaedah analisa prinsip komponen (PCA) dan transformasi fourier (FFT). Hasil analisa ke atas isyarat mendapati amplitud tertinggi pada agihan spektrum kuasa adalah pada jalur gamma bagi EEG berbanding jalur–jalur lain (delta, theta, alpha dan beta) bagi kedua–dua aktiviti. Kajian juga menunjukkan kelima–lima subjek mempunyai jalur gamma yang tinggi selepas solat berbanding selepas mendengar muzik. Keputusan ini mencadangkan, apabila seseorang muslim melakukan solat, mereka akan melupakan seketika masalah mereka dan khusyuk mengadap Allah. Ini dapat membantu memulihkan tekanan yang dialami mereka untuk beberapa ketika, seterusnya lebih bersedia untuk menghadapi segala permasalahan dunia selepas solat. Kata kunci: Solat; electroencephalograph (EEG); isyarat gelombang otak Salat is one of the ways for the Muslims to worship ‘Allah’ (God). This study investigates the brainwave signal after salat using Electroencephalograph (EEG) signal analysis and autonomic nervous activity. Twenty samples of EEG signal from five respondents (males with age range from 22 to 23 years old) were selected, and they were all free from cardiac, pulmonary, metabolic and other disease that would cause autonomic nervous system dysfunction. The analysis of the acquired EEG signal is done by comparing the samples of EEG signal between the activities after salat and after listening to the music using Principal Component Analysis (PCA) and Fast Fourier Transform (FFT) method. The highest amplitude of the power spectrum distribution was observed in the gamma band on EEG compared to other bands (delta, theta, alpha and beta) for both activities. It shows that these five subjects have a high gamma band after salat compared to after listening to music. It is suggested that when Muslim perform salat, they tend to forget all the worldly matters and thinks they are standing in front of the ‘Allah’. This eventually help them to break their stress for a few times, hence reducing its intensity to facing the worlds’ matter after salat. Key words: Solat; electroencephalograph (EEG); brainwave signal

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