Recovery of N100 component of auditory event-related potentials and EEG after cardiac arrest during propofol sedation.

We report on the EEG monitoring of a patient who suffered an episode of postoperative ventricular fibrillation (VF) following coronary artery bypass grafting (CABG). VF initially caused a considerable suppression and slowing of the EEG. The recovery of cerebral function was evaluated by recording both EEG and auditory event related potentials (ERPs). Six hours after the episode of VF, when the patient was asleep but arousable to voice command, the N100 component of the auditory ERPs had recovered to the level measured before the operation, whereas the EEG was still very slow for that level of sedation. This may have been due to VF having less effect on the N100 component than on the background EEG. Our findings suggest that measuring evoked potentials may improve the evaluation of brain function after cardiac arrest.

Sevoflurane anaesthesia in children after induction of anaesthesia with midazolam and thiopental does not cause epileptiform EEG.

BACKGROUND: Sevoflurane is a methyl ether anaesthetic commonly used for induction and maintenance of general anaesthesia in children. Sevoflurane is a non-irritant and acts quickly so induction is usually calm. However, inhalation induction with high concentrations of sevoflurane can cause convulsion-like movements and seizure-like changes in the electroencephalogram (EEG). Little is known about the EEG during maintenance of anaesthesia with sevoflurane, so we planned a prospective trial of sevoflurane maintenance after i.v. induction with benzodiazepine and barbiturate, which is another common induction technique in children. METHODS: EEG recordings were made before premedication with midazolam (0.1 mg kg(-1) i.v.), during induction of anaesthesia with thiopental (5 mg kg(-1)), and during maintenance with sevoflurane (2% end-tidal concentration in air/oxygen without nitrous oxide) in 30 generally healthy, 3- to 8-year-old children having adenoids removed. Noise-free EEG data of good quality were successfully recorded from all 30 children. RESULTS: Two independent neurophysiologists did not detect epileptiform discharges in any of the recordings. CONCLUSION: Premedication with midazolam, i.v. induction with thiopental and maintenance of anaesthesia with 2% sevoflurane in air does not cause epileptiform EEG patterns in children.

Effects of maternity on auditory event-related potentials to human sound.

Auditory event-related brain potentials (ERPs) were recorded in response to an emotional (a baby's cry) and a neutral (a word) stimulus in a group of mothers 2-5 days after childbirth (n = 20) and in control women (n = 18) who were not in the state of early motherhood. For each mother, her own infant's cry was recorded and used as the cry stimulus, whereas a strange baby's cry was used for control women. The word stimulus was identical for both groups. Stimuli were presented in intermittent trains in order to study the arousal responses to the first stimuli of the trains, and refractoriness of ERPs during stimulus repetition. The N100 responses were significantly larger in amplitude in mothers than in control women, not only to the emotional cry stimuli but also to the neutral word stimuli. The finding suggests a general increase in alertness and arousal in mothers, which may be necessary in enabling the mother to be continuously alert to her infant's needs. This allows good care of the infant and may be essential in building an emotional tie between the mother and her child.

Dynamic behavior of the auditory N100 elicited by a baby's cry.

We compared auditory N100 responses in female adults to two non-attended human sound stimuli. An infant's cry represented an unfamiliar, emotionally colored sound and the Finnish word "hei" (meaning "hi") a familiar and emotionally neutral sound. Both sounds elicited clear N100 responses over auditory areas in both hemispheres. However, the dynamic behavior of the N100 response following the first few repetitions of the sounds was significantly different. We observed faster habituation and longer response latencies, particularly over the ipsilateral hemisphere, during the first and second repetitions of the cry stimulus. This pattern may reflect an altered arousal level and slower, bilateral processing during the unfamiliar emotionally loaded cry as compared to the emotionally neutral word "hei" .

Persistent frontal P300 brain potential suggests abnormal processing of auditory information in distractible children.

The P300 event-related potential (ERP) was studied at the beginning, in the middle, and at the end of an auditory stimulus discrimination task in 70 normal 9-year-old children. Easily distractible children showed frontally a short-latency P300 response to target stimuli throughout the task, whereas in the non-distractible children the corresponding response was distinctly smaller and also showed a tendency to decrease in size towards the end of the task. The short-latency frontal P300 response reflects activation of the brain's orienting networks, and it normally decreases in size when stimuli lose their 'novelty value' with stimulus repetition. Persistent frontal P300 suggest that distractible children continued to show enhanced orienting to stimuli that should have already been well encoded and/or categorized.

Distractible children show abnormal orienting to non-attended auditory stimuli.

Event-related potentials were recorded in response to intermittently presented, non-attended trains of identical auditory stimuli in healthy 9-year-old children. In abnormally distractible children (n =24), the first tone in each train elicited a significantly larger N1 vertex response than in the non-distractible children (n 24), suggesting that increased distractibility may be associated with an abnormally strong cerebral orienting towards non-attended stimuli. A later negativity at around 300 ms, which increases in amplitude with stimulus repetition and may thus reflect the building up of a functional neuronal representation of the stimulus properties, was significantly smaller in the distractible than in the non-distractible children. These findings demonstrate that event-related potential measures may be useful in helping to understand the information processing found in distractible children.