REGULATION OF HUMAN THOUGHT BY NEUROPEPTIDE ACTH-4-10 - AN ANALYSIS OF THE EEG DIMENSIONAL COMPLEXITY

The neuroactive 4-10 fragment of adrenocorticotropin (ACTH 4-10) has b een found to impair electroencephalographic (EEG) signs of selective a ttention in previous studies. It was hypothesized that this effect ref lects a more general influence of the peptide weakening the mutual inh ibition among frontocortical neuronal networks. Therefore, ACTH 4-10 w as expected to loosen attentional control not only over external input but also over internal thoughts. This study examined the effects of A CTH 4-10 on the dimensional complexity of the EEG recorded while subje cts solved tasks of convergent analytical thinking and of divergent cr eative thinking and during mental relaxation. Subjects were tested 30 min after i.v. administration of placebo or ACTH 4-10 (2 mg). ACTH 4-1 0 enhanced dimensional complexity of the EEG. The effect primarily con cerned frontocortical recordings during convergent thinking, which, fo llowing placebo, was associated with the lowest EEG dimension. ACTH 4- 10 also impaired behavioral performance on tasks of convergent thought , when presented verbally. Results suggest that ACTH 4-10 counteracts the inhibitory control among cortical neuronal networks necessary for orderly analytical thinking.