Connecting the P300 to the diagnosis and prognosis of unconscious patients

The residual consciousness of unconscious patients can be detected by studying the P300, a wave among event-related potentials. Previous studies have applied tones, the subject＇s name and other names as stimuli. However, the results were not satisfactory. In this study, we changed the constituent order of subjects＇ two-character names to create derived names. The subject＇s derived names, together with tones and their own names, were used as auditory stimuli in event-related potential experiments. Healthy controls and unconscious patients were included in this study and made to listen to these auditory stimuli. In the two paradigms, a sine tone followed by the subject＇s own name and the subject＇s derived name followed by the subject＇s own name were used as standard and deviant stimuli, respectively. The results showed that all healthy controls had the P300 using both paradigms, and that the P300 in the second paradigm had a longer latency and two peaks. All minimally conscious state patients had the P300 in the first paradigm and the majority of them had the P300 in the second paradigm. Most vegetative state patients had no P300. Patients who showed the P300 in the two paradigms had more residual consciousness, and patients with the two-peak P300 had a higher probability of awakening within a short time. Our experimental findings suggest that the P300 event-related potential could reflect the conscious state of unconscious patients.

Visual-spatial neglect after right-hemisphere stroke:behavioral and electrophysiological evidence

Background:Visual-spatial neglect (VSN) is a neuropsychological syndrome,and right-hemisphere stroke is the most common cause.The pathogenetic mechanism of VSN remains unclear.This study aimed to investigate the behavioral and event-related potential (ERP) changes in patients with or without VSN after right-hemisphere stroke.Methods:Eleven patients with VSN with right-hemisphere stroke (VSN group) and 11 patients with non-VSN with righthemisphere stroke (non-VSN group) were recruited along with one control group of 11 age- and gender-matched healthy participants.The visual-spatial function was evaluated using behavioral tests,and ERP examinations were performed.Results:The response times in the VSN and non-VSN groups were both prolonged compared with those of normal controls (P<0.001).In response to either valid or invalid cues in the left side,the accuracy in the VSN group was lower than that in the non-VSN group (P<0.001),and the accuracy in the non-VSN group was lower than that in controls (P<0.05).The P1 latency in the VSN group was significantly longer than that in the control group (F[2,30]= 5.494,P = 0.009),and the N1 amplitude in the VSN group was significantly lower than that in the control group (F[2,30]= 4.343,P = 0.022).When responding to right targets,the lefthemisphere P300 amplitude in the VSN group was significantly lower than that in the control group (F[2,30]= 4.255,P = 0.025).With either left or right stimuli,the bilateral-hemisphere P300 latencies in the VSN and non-VSN groups were both significantly prolonged (all P<0.05),while the P300 latency did not differ significantly between the VSN and non-VSN groups (all P > 0.05).Conclusions:Visual-spatial attention function is impaired after right-hemisphere stroke,and clinicians should be aware of the subclinical VSN.Our findings provide neuroelectrophysiological evidence for the lateralization of VSN.