Application of nonlinear dynamics analysis in assessing unconsciousness: a preliminary study.

OBJECTIVES: To quantify the degree of unconsciousness with EEG nonlinear analysis and investigate the change of EEG nonlinear properties under different conditions. METHODS: Twenty-one subjects in persistent vegetative state (PVS), 16 in minimally conscious state (MCS) and 30 normal conscious subjects (control group) with brain trauma or stroke were involved in the study. EEG was recorded under three conditions: eyes closed, auditory stimuli and painful stimuli. EEG nonlinear indices such as Lempel-Ziv complexity (LZC), approximate entropy (ApEn) and cross-approximate entropy (cross-ApEn) were calculated for all the subjects. RESULTS: The PVS subjects had the lowest nonlinear indices followed by the MCS subjects and the control group had the highest. The PVS and MCS group had poorer response to auditory and painful stimuli than the control group. Under painful stimuli, nonlinear indices of subjects who recovered (REC) increased more significantly than non-REC subjects. CONCLUSIONS: With EEG nonlinear analysis, the degree of suppression for PVS and MCS could be quantified. The changes of brain function for unconscious subjects could be captured by EEG nonlinear analysis. SIGNIFICANCE: EEG nonlinear analysis could characterise the changes of brain function for unconscious state and might have some value in predicting prognosis of unconscious subjects.

[Aging study of event-related potential on visual spatial attention precued by Chinese words].

OBJECTIVE: Based on the visual experimental paradigm "precue-target", the search range should be affected by different Chinese characters and the dynamic mechanisms of aging in the brain on the visual attention were investigated. METHOD: 16 young and 16 old subjects participated the experiment. Cue was comprised of three Chinese words "Large", or "Median" or "Small." The letter "T" was designed as the target stimulus. When the cue was the "large", "T" may appear within 3 circles. When the cue was the "median", "T" may appear within either the median and small circles. When the cue was small, the target "T" may appear only within the small circle. RESULT: The reaction time (RT) of the two groups of subjects became quick with the reduction of the cue size, while amplitudes of the P1 and N1 component of ERPs increased with the decrease of the cue scale. Old subjects showed longer RT than younger subjects did. The posterior P1 was enhanced significantly and the N1 was inhibited obviously in the old group. The P2 was manifested as significantly inhibitory effect not only in the amplitude but also in the abnormal and unstable waveform. CONCLUSION: The cognitive function of elderly subjects declined in the task of visual spatial attention. We demonstrated for the first time that the P2 was manifested as significantly inhibitory effect, which suggested that the age-related reduction could lead to dysfunction in the anterior scalp to visual spatial attention (voluntary attention).