On the intercorrelation of some frequency and amplitude parameters of the human EEG and its functional significance. Communication II: neurodynamic imbalance in endogenous asthenic-like disorders.

In 67 borderline psychiatric patients suffering from schizotypal/slowly developing schizophrenic disorders and 18 patients suffering from cyclothymia, the factor structure of the period (interval-amplitude) parameters of the EEG proved to be similar to that obtained in normal subjects during mental activity and reported in part I (Lazarev, Int. J. Psychophysiol., 28 (1998) 77-98). However, 51 patients with schizotypal disorders with a predominance of asthenic-like symptomatology, characterized by mild thought disorders with difficulty in focusing attention, were distinguished from normal subjects, cyclothymic patients and other patients of schizotypy without well-defined asthenic symptoms by significantly increased values of EEG Factor II which was positively related to the index-presence in epoch, frequency and regularity of low-amplitude beta-waves, and reduced values of an EEG Factor III which was positively correlated with mean alpha-period and theta-index. According to normative data (part I; Lazarev, Int. J. Psychophysiol., 28 (1998) 77-98), this probably reflects a neurodynamic imbalance between an excess of 'cortical excitation' (Factor II) and a deficit of 'active selective inhibition' (Factor III). This imbalance appears to be opposite to the changes in values of these factors found in normal subjects during focusing attention and motor automation, when compared with relaxed wakefulness. The functional properties of Factors II and III ascribed on the basis of psychological testing suggest that such an imbalance could reflect a predominance of successively organised associative mental processes over the selective inhibition of irrelevant associations. This could cause difficulties in voluntary attention, mental automation and in the performance of simultaneous mental operations. In most cases, there was no difference in Factor I which was positively related to the index, amplitude and regularity of alpha-activity and wave amplitudes in other bands, and negatively related to the indices and mean periods of delta- and theta-waves, the factor presumed to depict 'general activation'.