Different event-related patterns of gamma-band power in brain waves of fast- and slow-reacting subjects.

Abstract

Fast-and dow-reacting subjects exhibit dif- By contrast, averages of time-varying event-related spectral (ERS) power reveal event-related modulations of ongoing or stimulus-induced oscillatory EEG activity, which are roughly time-locked but not specifically phase-locked to such events (4). The ways in which ERPs change when subjects actively respond to auditory stimuli instead of passively listening to them are well known (5). But while it is known that mean EEG spectral power in several frequency bands covaries with changes over time in performance of simple tasks (6, 7), less is known about rapid event-related changes in non-phase-locked EEG activity during task performance (8).This is particularly true for v-band EEG frequencies (25-90 Hz or higher) that are most commonly supposed to be associated with awareness or conscious perception (9-14). In human subjects, --band activity is enhanced during intense vigilance and performance ofcognitive tasks (6,9,10,(15)(16)(17), suppressed during central anesthesia and slow wave sleep (11, 12), and has been proposed to play essential roles in olfactory recognition, temporal integration, visual feature binding and segregation, and sensorimotor integration (18-24). Human ERPs evoked by auditory and other stimuli contain some v-band oscillations (25-27), but in animal cortex, vband activity induced by olfactory and visual stimuli usually appear as irregular bursts roughly time-locked but not phase-locked to stimulus onsets (20, 28-31).The present study answers three questions: (i) How does the EEG frequency spectrum after presentation of brief auditory stimuli differ when subjects react quickly to the stimuli instead of passively listening to them? (ii) Do v-band components ofthe stimulus-locked ERP also differ in the two conditions? (iii) Do fast-and slow-reacting subjects have qualitatively similar or different dynamic patterns of vband EEG activity during the response task? Our analysis of time-varying power in the v-frequency band demonstrates that two different modes of auditory-response processing underlie between-subject reaction time differences, supporting claims that vband activity has functional significance in sensorimotor processing. METHODSTwenty-three right-handed adults (ages 20-53) were tested in two conditions. (i) One hundred and ten clicks (2-ms-wide square pulses, 75 decibels sound pressure level) were presented binaurally through head phones at random interstimulus intervals of 3-7 s. (ii) Subjects were asked to react as quickly as possible to a second set of 275 identical clicks by pressing a response button with the right index finger. EEG epochs of 640 ms, beginning 128 ms before each click, were recorded with a sampling rate of 2000 Hz using a 12 bit analog/digital converter with an analog high-pass-filter cutoff

Early Neural Correlates of Conscious Somatosensory Perception

“…1 B, bottom) and in line with the proposition that distinct processing routes to response initiation might be exploited by the fast-and slow-reacting subjects (cf. Jokeit and Makeig, 1994;Makeig et al, 1999). The presence of very fast responses (ϳ200 ms) in our data in some subjects raises a question about whether the initiation of motor reaction could occur also before or in parallel with the conscious sensory perception (cf.…”

“…The presence of very fast responses (ϳ200 ms) in our data in some subjects raises a question about whether the initiation of motor reaction could occur also before or in parallel with the conscious sensory perception (cf. Jokeit and Makeig, 1994;Makeig et al, 1999), which suggests that also within individual subjects, distinct processing strategies might take place on different trials. Depending on the subject, 4 -17% of RTs exceeded 1 s (Fig.…”

Functional correlates of brain aging: beta and gamma components of event-related band responses

“…Thus, the enhancement of left frontal γ1 responses to high-frequency tone stimulation and right occipitoparietal responses to low-frequency tone stimulation (100-800 ms after stimulus onset) in the elderly group may be associated with a compensatory function of these brain areas for increased attentional level to memorize stimuli. Correlations between gamma1 activity and performance have been seen only after high tone stimulation (Jokeit and Makeig 1994, Kaiser et al 2009a, 2009b. Fast-and slow left-hand reacting subjects exhibit different patterns of gamma1 band activity when responding as quickly as possible to high-frequency auditory stimuli.…”

Visually induced gamma-band responses in human electroencephalographic activity ? a link to animal studies

“…In addition, the duration of synchronous firing is brief (100-200 ms in cats; Gray et al 1989). Indications of induced gamma-band responses in humans had been previously reported for visual (Lutzenberger et al 1995), auditory (Jokeit and Makeig 1994), and sensorimotor (Kristeva-Feige et al 1993) stimulation and during word processing (Pulvermtiller et al 1994a, b). In these studies power spectra were calculated by using fast fourier transformations (FFT) with short and overlapping data windows.…”