5 Electrophysiologic Evidence of Neural Injury or Adaptation in Cocaine Dependence 1. INTRODUCTION Kenneth R. Alper, Leslie s. Prichep, E. Roy John, Sharon C. Kowalik, and Mitchell s. Rosenthal The electroencephalogram (EEG) is an emergent phenomenon of neural activity, which suggests that the EEG might reflect the apparently abnormal neurobiology ob- served in cocaine dependence. The EEG is noninvasive, inexpensive, and quantitative analysis of the EEG (QEEG) is based on information processing technology that is constantly growing with respect to analytic power and accessibility. Clinically, QEEG has been shown to be sensitive to psychiatric conditions, such as depression or atten- tion deficit hyperactivity disorder (ADHD) that are often comorbid with cocaine de- pendence (1-3). Pretreatment QEEG has been shown to be predictive of subsequent psychotropic drug response in patients with a variety of psychiatric disorders evaluated prospectively (4,5). Neural injury or adaptation in cocaine dependence resulting in changes in the underlying sources ofthe EEG and reflected quantitatively in the QEEG, could be relevant to "staging" the disorder with respect to the identification of revers- ible vs irreversible components, and could potentially provide an approach to the de- velopment or selection oftreatment. This chapter focuses on data obtained from a large population of cocaine-dependent subjects in our ongoing National Institute on Drug Abuse (NIDA) funded work on cocaine dependence. The chapter first provides a brief overview of structural and metabolic imaging studies in cocaine dependence, then re- views studies of EEG power spectral findings in chronic cocaine exposure in animals and humans, and our work on persistence of QEEG abnormality and evidence of electrophysiologic heterogeneity and its clinical correlates in cocaine dependence. Lastly, we attempt an interpretation of our QEEG findings will be considered in the context of hypothetical mechanisms of neural injury or adaptation. Frorn: Handbook of Neurotoxicology, VoI. 2 Edited by: E. J. Massaro © Humana Press Ine., Totowa, NJ 131