ENHANCED DIMENSIONAL COMPLEXITY OF THE EEG DURING MEMORY FOR PERSONALPAIN IN CHRONIC PAIN PATIENTS

Associative connections between cortical cell assemblies representing pain-related memories should be stronger and more extensive in subject s with chronic pain. To test this hypothesis, the dimensional complexi ty of the electroencephalograph (EEG) was examined during the actual e xperience as well as during memory for pain. Nine chronic pain patient s and nine matched healthy controls participated in the study. During acute pain induction, acute pain recall, personal stress and pain reca ll, the EEG was recorded from 15 scalp sites. Non-linear analysis, bas ed on the theory of deterministic chaos, revealed higher and more wide spread EEG complexity in the patients compared to the healthy controls only during the recall of the personal pain scene. The personal stres s scene was rated equally aversive but did not induce more EEG complex ity. These more extensive and more readily accessible pain memories ma y be instrumental for the persistence of chronic pain. (C) 1997 Elsevi er Science Ireland Ltd.