Identification of the optimal parameters for recording cortical evoked potentials to human oesophageal electrical stimulation

Abstract

Cortical evoked potentials in response to stimulation of the oesophagus may prove to be a powerful technique for assessing the oesophageal afferent pathway in health and disease. However, in order to maximize the potential of this technique it is essential that the optimal parameters for recording oesophageal CEP are established. The aim was to determine the optimal parameters required to record reproducible CEP. CEP were recorded from the vertex in eight subjects (age range 23-44 years). Electrical stimulation was performed 5 cm above the lower oesophageal sphincter using a bipolar ring electrode at 0.2 Hz. Protocol 1: to determine the stimulation intensity which generates the largest amplitude and shortest latency, two runs of 50 stimuli were applied at increasing intensities. Protocol 2: to determine the number of stimuli for optimal signal to noise ratio, 10 runs of 50 stimuli were recorded. Individual runs were averaged. Protocol 3: to determine the optimal inter-run interval, CEP evoked by 200 stimuli were averaged using randomly chosen inter-run intervals. Protocol 4: CEP reproducibility using parameters determined from Protocols 1-3 was assessed in three subjects on three separate occasions. The results were as follows: Protocol 1; P1 latency was shortest and P1-N1 amplitude largest at an intensity of 75% above threshold. Protocol 2; optimal signal-to-noise was achieved by averaging four runs of 50 stimuli. Protocol 3; the optimal interstudy interval was 10 min. Protocol 4; highly reproducible CEP were obtained in all individuals. Using these optimal parameters, it is possible to obtain highly reproducible oesophageal CEP to ES which can now be used for clinical study.

Neurophysiological evaluation of convergent afferents innervating the human esophagus and area of referred pain on the anterior chest wall

“…The protocols for esophageal and chest evoked potentials differed slightly because the esophageal stimulation intensity used to evoke the cortical responses was always calculated as a percentage of the subject's pain threshold on that particular day (15). As pain thresholds increased between visits, then the stimulation intensity used also increased, and this was reflected by a reduction in the latency of some evoked potential components, which is commonly seen when the stimulation intensity is increased.…”

“…EEP were recorded by averaging a total of 200 esophageal stimuli, acquired at a frequency of 0.2 Hz, during four runs of 50 stimuli, with a 10-min interrun interval. The parameters used were selected on the basis of our previous work to provide optimal EEP responses (15). After each run of 50 stimuli, the subjects were asked to score the esophageal sensation experienced using a six-point categorical rating scale: 1, Unaware; 2, Slight sensation; 3, Definite sensation; 4, Slight Discomfort; 5, Uncomfortable; and 6, Painful.…”

“…This procedure was repeated three times and average values were obtained. In addition, 75% pain threshold was calculated as the stimulation intensity to be used for esophageal evoked potentials (EEP) as previously reported (15). EEP were recorded by averaging a total of 200 esophageal stimuli, acquired at a frequency of 0.2 Hz, during four runs of 50 stimuli, with a 10-min interrun interval.…”

Accuracy of heartbeat perception is reflected in the amplitude of the heartbeat‐evoked brain potential

“…They reported significant correlations (up to .83) between the heartbeat perception score and different cardiodynamic parameters, that is, stroke volume, blood ejection velocity, momentum of the ejected blood mass, and contractility. For external stimuli (visual, auditory, somatosensory), it is a wellestablished fact that the stimulus intensity influences the amplitudes of the evoked potentials (e.g., Carrillo-de-la-Pena, Rodriguez Holguin, Corral, & Cadaveira, 1999;Cass & Polich, 1997;Covington & Polich, 1996;Nakajima & Imamura, 2000 O. Pollatos and R. Schandry studies with esophageal-evoked potentials showed that an increase of stimulus intensity was associated with an increase in the amplitude of the esophageal-evoked potential components (Fallen et al, 2001;Hobson et al, 1998Hobson et al, , 2000.…”

Translational aspects of rectal evoked potentials: a comparative study in rats and humans

“…In humans, patients suffering from irritable bowel syndrome report lower pain detection threshold to colorectal distension than healthy volunteers (29,35), indicating that the model is sensitive to underlying pathophysiology. An improved translational model includes the use of cerebral evoked potentials (CEPs) to objectively assess the brain response to colorectal distension in animals and humans (16,19,20,33,37,38). In previous studies, electrically elicited CEPs from the gut have been favored, compared with balloon distension, because this stimulus is easier to control with respect to localization, onset, and duration.…”