An EEG correlate of the Archimedes spiral after-effect and its relationship with personality

Previous work has demonstrated a relationship between the Archimedes spiral after-effect (SAE) and dysthymia-hysteria. The aim of the present study was to discover whether there was any EEG correlate of this relationship. As subjects 20 dysthymics, 17 hysterico-psychopaths, and 9 normals were used, comparisons being made between the SAE and various EEG parameters. These included the alpha index and latency of alpha return on eye-closure, following fixation of a rotating spiral. Using various criteria of the latter measure a consistently significant positive correlation was found between the SAE and the extent to which the return of alpha was delayed by visual stimulation. Significant correlations were also found between alpha index and SAE, and alpha index and alpha latency. In addition, previous group differences in sedation threshold and SAE were confirmed, although there were low correlations between the EEG measures and sedation threshold.

It was concluded that subjects having more activated EEG records tend to report longer subjective SAE's and to show a greater delay in the return of alpha alter visual stimulation. In terms of personality type obsessionals and psychopaths seem to show the greatest differences in this respect. These results are thought to throw some light on the physiological basis of Eysenck's excitation-inhibition theory of personality.