The present study demonstrates that event-related potentials (ERPs) may be used to reveal increased distractibility as a physiologically measurable condition after chronic closed head injury (CHI). ERPs were recorded from 17 chronic CHI subjects and from 17 healthy age-matched controls. Auditory stimuli consisted of variants of vowel /o/ (standards) occasionally replaced by an /e/ vowel (deviant). Subjects were instructed to ignore auditory stimuli while watching a silent movie. In the constant-standard condition, the vowel /o/ served as the standard and vowel /e/ as the deviant. In the roving-standard condition, four variants of the vowel /o/ were randomly used as standards in the same stimulus block. None of the stimuli were prototypes in the subjects’ mother tongues. Deviant stimuli elicited significant MMNs in both groups in both conditions, which were significantly smaller in the roving-standard than in the constant-standard condition. CHI victims showed significantly larger P3a amplitudes than controls in both conditions, apparently reflecting their enhanced involuntary sifting of attention and thus their increased distractibility.
Cognitive Brain Research Unit, Department of Psychology, PO Box 13, FIN-00014 University of Helsinki;
1 Helsinki University Central Hospital, Department of Neurosurgery, Topeliuksenkatu 5, 00260 Helsinki;
2 Helsinki University of Technology, Acoustics Laboratory, PO Box 3000, FIN-02015 TKK, Finland
CA Corresponding Author
Received I February 2000; accepted 26 February 2000
Acknowledgments: This research was supported by The Academy of Finland and the Centre of International Mobility (CIMO, Helsinki, Finland). The authors wish to thank Dr Istvan Winkler for his constructive comments during the preparation of this report and Mr Jorma Arkkila for data collection.