| Abstract [eng] |
A great need for easily assessable brain signatures that can be used to diagnose or predict the outcome of psychiatric disorders or can be implemented in neuro-technological applications has emerged. Electroencephalography (EEG), being cheap and non-invasive technique, has been widely utilized for this purpose. The auditory steady-state response (ASSR) is one of the most widely investigated responses with respect to gamma band neural oscillations. The aim of this work was to investigate the properties of 40 Hz auditory steady-state responses induced by flutter amplitude-modulated tones (FAM), and compare them to classical click-induced (Click) 40 Hz ASSRs. We estimated subjective pleasantness of FAM and Click stimuli; compared effect of different levels of attention paid to stimulation on FAM-elicited 40 Hz ASSRs and on Click-induced 40 Hz ASSRs by measuring response strength and the local and global phase-locking. Also potential of FAM-elicited 40 Hz ASSRs and classical click induced 40 Hz ASSRs to highlight gamma-range abnormalities in patients with schizophrenia were evaluated. The results showed that FAM stimuli were perceived neutrally pleasant and neutrally arousing and were rated as less unpleasant and less arousing than Click stimuli and 40 Hz ASSRs to FAM stimulation were not modulated by attentional demands; click-elicited 40Hz ASSRs were reduced and less synchronized at the local and global level during distractive task as compared to the state of focused attention to stimulation. Also the amplitudes and the phase-locking of 40 Hz ASSRs evoked by FAM stimuli were reduced in schizophrenic patients in comparison to healthy controls, similarly to reduced parameters of click-evoked ASSRs. |
