Electroencephalography and clinical neurophysiology
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Electroencephalogr Clin Neurophysiol · Mar 1989
Pain-related somatosensory evoked potentials following CO2 laser stimulation in man.
Pain-related somatosensory evoked potentials (SEPs) following CO2 laser stimulation were analyzed in normal volunteers. Low power and long wavelength CO2 laser stimuli to the hand induced a sharp pain which was associated with a large positive component, P320, recorded over the scalp. Amplitude decreased and latency increased with reduction in stimulus intensity and subjective pain feeling. ⋯ No potential corresponding to P320 could be recorded following electrical or mechanical tactile stimulation. We consider P320 to be generated by impulses arising from pain stimuli and ascending through A delta fibers. We propose the thalamus as a generator source from considering its scalp topography, but pain-specific cognition or perception may also be involved in generating this potential.
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Electroencephalogr Clin Neurophysiol · Nov 1988
Late somatosensory evoked cerebral potentials in response to cutaneous heat stimuli.
Late components of cerebral potentials evoked by brief heat pulses applied to various skin sites were used to monitor the afferent pathways of pain and temperature sensitivity. Radiation at 10.6 micron wave length generated by a CO2 laser stimulator predominantly activates superficial cutaneous A delta and C nociceptors and elicits late and ultralate cerebral potentials. This paper deals with the investigation of the component structure and topography of the A delta fibre mediated late potentials, which were compared with the corresponding late potentials in response to standard electrical nerve stimuli. ⋯ After stimulation of the lower limb all latencies were delayed by 20-30 msec. As a rule, the heat-evoked potentials appeared about 100 msec later than the corresponding potentials after electrical nerve stimulation. Similarities in interpeak latencies and scalp topography indicated similar cerebral processing.
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Electroencephalogr Clin Neurophysiol · May 1988
The cyclic alternating pattern sequences in the dynamic organization of sleep.
The cyclic alternating pattern (CAP) is a physiological component of normal NREM sleep, functionally correlated with long-lasting arousal oscillations. This EEG periodic activity, organized in sequences of two or more decasecond cycles, is detectable also in coma and in other neurologic disorders, appearing as a general modality of arousal organization. Within NREM sleep, the fluctuations of CAP alternate with sustained homogeneous EEG patterns, characterized by a greater stability of arousal and called non-CAP (NCAP). ⋯ Moreover, almost 50% of all NREM stage changes were accompanied by CAP sequences. The EEG and dynamic features of CAP sequences show morphological and behavioural analogies with some phasic phenomena (i.e., phase d'activation transitoire or micro-arousals) and EEG patterns reported in the literature (e.g., tracé alternant; phase transitionnelles; tracé intermittent). Our data suggest a functional correlation between the control mechanisms of CAP and the organization of sleep.
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Electroencephalogr Clin Neurophysiol · Oct 1987
Effect of low concentration stable xenon on the EEG power spectrum.
The effect on the central nervous system of inhaled stable xenon, at concentrations of 25%, 30% and 35%, was assessed by evaluating changes in power spectra computed on the electroencephalogram. Ten normal adult subjects were studied in a protocol designed as a repeated measures experiment. ⋯ These changes were equivalent for symmetrical electrode pairs, but the time history of the changes differed depending on the cortical region being measure. This suggests regional effects of stable xenon inhalation on the mechanisms producing the EEG.
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Electroencephalogr Clin Neurophysiol · May 1987
Changes in the VEP in preterm neonates with arousal states, as assessed by EEG monitoring.
The effect of sleep state on the visual evoked potentials (VEPs) in neonates was investigated in 7 preterm infants. Polygraphic monitoring including EEG, EOG, ECG, respirogram and submental EMG for the purpose of sleep staging was carried out on all infants simultaneously with VEP testing. Awake-sleep stages were classified into 4 states: awake, transitional or atypical, quiet sleep and active sleep. ⋯ The P200, present in the older infants, disappeared in both active and quiet sleep states; the P400 was typically variable but reliably present in the awake or atypical states. When a distinction is made between quiet sleep and other arousal states, consistent and significant differences emerge. Our results emphasize the need to test infants in the same arousal states in studies of VEPs in order to make valid comparisons of latency or amplitude changes, particularly with longitudinal or follow-up studies.