Methodology
Issues and assumptions on the road from raw signals to metrics of frontal EEG asymmetry in emotion

https://doi.org/10.1016/j.biopsycho.2004.03.007Get rights and content

Abstract

There exists a substantial literature examining frontal electroencephalographic asymmetries in emotion, motivation, and psychopathology. Research in this area uses a specialized set of approaches for reducing raw EEG signals to metrics that provide the basis for making inferences about the role of frontal brain activity in emotion. The present review details some of the common data processing routines used in this field of research, with a focus on statistical and methodological issues that have captured, and should capture, the attention of researchers in this field.

Section snippets

From raw signals to handy metrics

Investigators who examine frontal EEG asymmetry use a set of relatively specialized signal processing routines, which will be reviewed anon. This review is not intended so serve as a primer for basic signal processing, but rather is designed to highlight the data reduction trail typically followed in this specific research domain. For a basic primer, many sources are available, including easily accessible chapters by Gratton (2000) and by Reilly (1987), and a more in depth treatment by Glaser

Comparing left and right activity

Because asymmetrical activity is of interest, investigators often use a difference score (ln(Right)−ln(Left) alpha power) to conveniently summarize the relative activity at homologous right and left leads.

How much raw data should be acquired?

Sufficient data are required to ensure that reliable estimates of EEG activity are derived. Although the power spectrum derived from any single epoch via the FFT will reflect both frequencies that are common across epochs as well as those idiosyncratic to any given epoch, averaging together multiple spectra can allow those frequencies to emerge that are present in a reasonably large proportion of epochs (see Fig. 1, Panel E), while mitigating the influence of infrequent or irregular signals (

Alpha and activity

A guiding assumption underlying the interpretation of findings involving frontal EEG alpha asymmetry is that greater alpha power is indicative of less cortical activity in broad underlying regions (cf. Davidson, 1988). Although there is good evidence to support this assumption, one might question whether this relationship is ubiquitous.

It has been well documented that sensory input shows modality-specific blocking of alpha activity at cortical regions involved in processing such input. With

Synopsis

Research on frontal EEG asymmetry and emotion now represents a substantial body of literature. There are numerous methodological issues to which the field may have paid insufficient attention, while at the same time paying potentially too much attention to other factors. The field may have been too concerned with recording at least 8 min of data to obtain reliable estimates of asymmetry, overly concerned about the impact of blink artifacts, and overly concerned with closely matching impedances

Acknowledgements

This research was supported, in part, by a grant from the National Alliance for Research on Schizophrenia and Depression (NARSAD) and an Exploratory/Development Grant from the National Institutes of Health (1 R21 RR09492) to J.J.B.A., and by a Graduate Research Fellowship from the National Science Foundation to J.A.C.

References (87)

  • W. Klimesch et al.

    Brain oscillations and human memory: EEG correlates in the upper alpha and theta band

    Neuroscience Letters

    (1997)
  • J.P. Kline et al.

    Sex, lie scales, and electrode caps: an interpersonal context for defensiveness and anterior electroencephalographic asymmetry

    Personality & Individual Differences

    (2002)
  • P. Leissner et al.

    Alpha amplitude dependence on skull thickness as measured by ultrasound technique

    Electroencephalography & Clinical Neurophysiology

    (1970)
  • A.F. Leuchter et al.

    Cordance: a new method for assessment of cerebral perfusion and metabolism using quantitative electroencephalography

    Neuroimage

    (1994)
  • A.F. Leuchter et al.

    Relationship between brain electrical activity and cortical perfusion in normal subjects

    Psychiatry Research

    (1999)
  • A. Pfefferbaum

    Model estimates of CSF and skull influences on scalp-recorded ERPs

    Alcohol

    (1990)
  • Y. Shoda et al.

    Toward a unified, intra-individual dynamic conception of personality

    Journal of Research in Personality Special Issue: The Future of Personality

    (1996)
  • Aiken, S.L., West, S.G., 1991. Multiple Regression: Testing and Interpreting Interactions. Sage Publications, Thousand...
  • J.J.B. Allen et al.

    Manipulation of frontal EEG asymmetry through biofeedback alters self-reported emotional responses and facial EMG

    Psychophysiology

    (2001)
  • Allen, J.J.B., Urry, H.L., Hitt, S.K., Coan, J.A., 2004. The stability of resting frontal electroencephalographic...
  • P. Andersen et al.

    Nature of thalamo-cortical relations during spontaneous barbiturate spindle activity

    Journal of Physiology

    (1967)
  • P. Andersen et al.

    Some factors involved in the thalamic control of spontaneous barbiturate spindles

    Journal of Physiology

    (1967)
  • D.J. Bem et al.

    On predicting some of the people some of the time: the search for cross-situational consistencies in behavior

    Psychological Review

    (1974)
  • H. Berger

    Uber das elektrenkephalogramm des Menschen II

    Journal fur Psychologie und Neurologi

    (1930)
  • H. Berger

    Uber das elektrenkephalogramm des Menschen III

    Archiv fur Psychiatrie und Nervenkrankheiten

    (1931)
  • H. Berger

    Uber das elektrenkephalogramm des Menschen IV

    Archiv fur Psychiatrie und Nervenkrankheiten

    (1932)
  • J.C. Borod et al.

    Neuropsychological aspects of facial asymmetry during emotional expression: a review of the normal adult literature

    Neuropsychology Review

    (1997)
  • Cacioppo, J.T., Tassinary, L.G., Fridlund, A.J., 1990. The skeletomotor system. In: Cacioppo, J.T., Tassinary, L.G....
  • D.T. Campbell et al.

    Convergent and discriminant validation by the multitrait–multimethod matrix

    Psychological Bulletin

    (1959)
  • J.A. Coan et al.

    Frontal EEG asymmetry and the behavioral activation and inhibition systems

    Psychophysiology

    (2003)
  • Coan, J.A., Allen, J.J.B., 2003b. The state and trait nature of frontal EEG asymmetry in emotion. In: Hugdahl, K.,...
  • Coan, J.A., Allen, J.J.B., 2004. Frontal EEG asymmetry as a moderator and mediator of emotion. Biological Psychology...
  • J.A. Coan et al.

    Voluntary facial expression and hemispheric asymmetry over the frontal cortex

    Psychophysiology

    (2001)
  • Cronbach, L.J., Gleser, G.C., Nanda, H., Rajaratnam, N., 1972. The Dependability of Behavioral Measurements: Theory of...
  • R.M. Cruickshank

    Human occipital brain potentials as affected by intensity-duration variables of visual stimulation

    Journal of Experimental Psychology

    (1937)
  • R.J. Davidson

    EEG measures of cerebral asymmetry: conceptual and methodological issues

    International Journal of Neuroscience

    (1988)
  • R.J. Davidson

    Affective style and affective disorders: perspectives from affective neuroscience

    Cognition & Emotion

    (1998)
  • Davidson, R.J., 22 and 24 September 2002. Personal...
  • R.J. Davidson et al.

    Asymmetrical brain electrical activity discriminates between psychometrically-matched verbal and spatial cognitive tasks

    Psychophysiology

    (1990)
  • Davidson, R.J., Jackson, D.C., Larson, C.L., 2000a. Human electroencephalography. In: Cacioppo, J.T., Tassinary, L.G.,...
  • F. Di Nocera et al.

    G theory and the reliability of psychophysiological measures: a tutorial

    Psychophysiology

    (2001)
  • Durup, G., Fessard, A., 1936a. L’electrencephalogramme de l’homme. Donnees quantitatives sure l’arret provoque par des...
  • G. Durup et al.

    L’electrencephalogramme de l’homme observations psychophysiologiques relative a l’action des stimuli visuels et auditifs

    Annee Psychologie

    (1936)
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