Investigation into Indices of Aging and Schizophrenia Using the Photic Driving Response

In the current study, we quantitatively evaluated aging and schizophrenia using statistical indices reflecting enhancement and suppression at arbitrary frequencies using photic stimulation (PS). This index corresponds to the Z-score, which reflects the distance between two amplitude distributions at an arbitrary frequency at rest and during PS. We measured EEGs from three groups: 50 healthy subjects aged between 20-30, 30 healthy subjects aged 60 and over, and 31 schizophrenia patients aged 60 and over. We obtained frequency characteristics of Z-scores in each group. Prominent characteristics of fundamental and harmonic components that were sensitive to schizophrenia disease and aging were observed at 6, 7 and 10 Hz PS. We then defined two indices to evaluate schizophrenia symptoms and aging: the average of Z-scores at fundamental and all harmonic frequencies except the harmonics in alpha band and gamma band over 30 Hz (Index A), and the subtraction value of the minimum Z-score in alpha band from the average of the Z-scores in gamma band (Index B). The results revealed a significant difference between the older healthy group and the schizophrenia group in Index A, and between the younger and older groups in Index B.