1. Neurofeedback of beta frequencies:
Effects on alertness and motor inhibition
Miguel Pimenta, Jan de Fockert, John Gruzelier
Department of Psychology, Goldsmiths, University of London
Abstract
Background: Neurofeedback (NFB) of beta frequencies has been associated with improvements in alertness and motor inhibition in both healthy and attention-deficit hyperactivity disorder (ADHD) individuals. The aim of the current work was to further investigate the effects of successful NFB training of the sensorimotor rhythm (SMR) and beta1 amplitude on electrophysiological and behavioural measures of alertness and motor inhibition.
Method: We compared healthy adults in three NFB groups (SMR, beta1 and active NFB control) during an auditory oddball task and a Go/Nogo task and obtained event-related potentials and reaction times measures.
Results: SMR learning was associated with increased Nogo P3 amplitude, while increments in beta1 amplitude across sessions were positively correlated with higher oddball P3b amplitude changes.
Discussion: These data support the hypothesis that SMR and beta1 NFB are associated with different patterns of cognitive functional improvement.
Initial mixed ANOVAs (Time x Electrode x Group) revealed no post-training differences between NFB groups on both tasks. Subsequent analysis focused on learning coefficients within the target frequencies (SMR or beta1) and comparison of learners with non-learners, irrespective of the assigned NFB group.
Results
Learning coefficient was entered as an outcome variable in a step-wise linear multiple regression.
P3b amplitude changes on 9 electrodes (3 frontal, 3 central and 3 parietal) we included as predictor variables.
For beta1 frequency a significant regression model was obtained (F(9,28) = 2.56, p <.05; R2 = .55).
In healthy adults that received both SMR (12-15Hz) and beta1 (15-18 Hz) NFB training, increased amplitude on both frequencies was associated with increased amplitude of the event-related potential (ERP) P3b in an oddball task which was interpreted as an alertness enhancement effect1.
In a subsequent between-subjects design study NFB in the beta1 frequency range was associated with increased amplitude of the oddball P3b event-related potential (ERP) and decreased reaction times, while no such effects were not observed for the SMR training group. This was interpreted as a dissociation of the effects of NFB training on alertness enhancement2.
ADHD children that learned to elevate both SMR and beta1 amplitudes have shown increased Nogo P3 amplitude compared to non-learners favouring the interpretation of improved motor inhibition3.
It was hypothesized that NFB on the SMR frequency would lead to improved motor inhibition while NFB on the beta1 frequency would be associated with increased alertness at post-training as indexed by specific ERP components amplitude.
Background
Fig.1. Changes in Beta1 learning coefficient vs. P3b amplitude change from pre to post-training at Pz.
Omnibus ANOVA indicated a marginally significant three-way interaction of ‘Time x Electrode x SMR learning’ (F (2,58) = 3.25, p = .06).
Nogo P3
Fig. 2. P3 Nogo mean amplitude at pre-training (T1) and post-training (T2) for SMR learners recorded at Fz.
ANOVA for SMR learners revealed a significant main effect of ‘Time’ (F(1,14) = 8.48, p < .05) on Nogo mean amplitude at Fz for the SMR learners group. No main or interaction effects were significant for SMR non-learners (p > .14).
Method
Discussion
A distinct pattern of electrophysiological changes was found to be associated with SMR learning and increased beta1 amplitude across training sessions. While successful SMR learning was associated with increases in Nogo P3 amplitude, increments on beta1 amplitude across sessions were positively correlated with a higher P3b amplitude after training.
These data support the hypothesis that the conditions that contribute to SMR and beta1 enhancement might involve different underlying psychophysiological processes with distinct impact on motor inhibition and alertness.
Future research will focus on elucidating the complex relationship between NFB training, learning in the target and adjacent frequency bands (within and outside the beta frequency band) and outcomes in both electrophysiological and behavioral measures of cognitive functioning.
Participants: Thirty-one participants (19 females; age range, 18-35; mean age, 23) screened for neuropsychiatric disorders were randomly allocated to three NFT conditions: (1) a control condition (consisting of a non-frequency specific NFT), (2) a SMR condition, and (3) a beta1 condition.
NFB: Each participant took part in 6 NFB sessions. Each session was composed of two non-feedback trials (before and after training) and eight NFB trials of 180 seconds. Participants received visual and auditory feedback contigent on the moment-to-moment amplitude of the target frequency and were asked to attempt to keep it above the thresold defined according to the initial non-feeedback trial (baseline).
ERP: EEG was recorded at pre and post-training from 64 channels during an active auditory 3-stimuli oddball task (target/standard/non-target = 1:8:1) and Go/Nogo task (2:1). Reaction time measures were collected for the Go responses in both paradigms.
References
1 Egner & Gruzelier (2001). Learned self-regulation of EEG frequency components affects attention and event-related brain potentials in humans. Neuroreport, 12(18), 4155–9.
2 Egner & Gruzelier (2004). EEG Biofeedback of low beta band components: frequency-specific effects on variables of attention and event-related brain potentials. Clinical Neurophysiology, 115,
3 Kropotov,et al.(2005). Event-related potentials correlates of electroencephalographic relative beta training in ADHD children. International Journal of Psychophysiology, 55,
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