Campylobacter enteritis.
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Campylobacter Infections↗
Biomedical subjects
S G Boyd
Publications and source records attributed to S G Boyd.
Sensory and cognitive components of the CO2 laser evoked cerebral potential.
We recorded CO2 laser evoked cerebral potentials in 6 healthy subjects using both a standard technique and an oddball paradigm. In the standard technique stimuli were aimed at the dorsum of the left hand with the subject passive; in the oddball paradigm, target infrequent stimuli (P = 0.15) were directed to one side of the dorsum of the left hand and the subject was instructed to count their occurrence, the frequent stimulus being delivered to the other side of the hand. In both standard and oddball frequent recordings, CO2 laser evoked potentials were a well-formed negative-positive complex with a peak latency and amplitude around 305 msec (to positivity) and 32 microV respectively. However, in the oddball target task a later potential was also recorded, with a mean latency and amplitude of 621 msec and 24 microV respectively which we believe to be a laser oddball potential. These results demonstrate that the CO2 potential is not altered by manipulations of attention to any significant extent and suggests that it is therefore closely related to the primary sensory input. They also provide further evidence of the non-specificity of the oddball potential across sensory modalities.
Adult↗
Time-shifted averaging for laser evoked potentials.
Cerebral potentials evoked by CO2 laser stimulation were recorded in 22 normal volunteers. Substantial variability in latency, morphology and amplitude of the responses in individual trials was noted, and in some trials no response appeared to be present. Averaging after latency correction and removal of traces without clear responses was compared with conventional time-locked averaging. We found a greater amplitude and more consistent wave form in the former case, and better preservation of amplitude with increasing age and under conditions of impaired attention. Cross-correlation techniques and Minimum Mean Square Error (MMSE) filtering did not assist identification of responses. We conclude that with laser-evoked cerebral potentials visual identification of components is a simple and reliable way of obtaining an improved estimate of the average evoked potential.
Adult↗