Time-shifted averaging for laser evoked potentials

Purves, A.M.; Boyd, Stewart

doi:10.1016/0168-5597(93)90062-t

Cited by 21 publications

(9 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because of the inadequacy of standard averaging for the analysis of non‐stationary evoked potentials (Purves & Boyd, 1993; Iannetti et al 2005) and the availability of a robust algorithm to extract N2 and P2 peak single‐trial information from LEPs (Mayhew et al 2006), all the results described later in this paper were obtained from single‐trial N2 and P2 latency and amplitude values. The grand average waveforms and their corresponding latency and amplitude values described in the present paragraph and shown in Figs 2 and 3 are reported to facilitate comparison with previous reports using similar stimulation techniques.…”

mentioning

confidence: 99%

Similar nociceptive afferents mediate psychophysical and electrophysiological responses to heat stimulation of glabrous and hairy skin in humans

Iannetti

Zambreanu

Tracey

2006

The Journal of Physiology

152

133

View full text Add to dashboard Cite

The ability to perceive and withdraw rapidly from noxious environmental stimuli is crucial for survival. When heat stimuli are applied to primate hairy skin, first pain sensation is mediated by type-II A-fibre nociceptors (II-AMHs). In contrast, the reported absence of first pain and II-AMH microneurographical responses when heat stimuli are applied to the hand palm has led to the notion that II-AMHs are lacking in this primate glabrous skin. The aim of this study was to assess the effect of hairy and glabrous skin stimulation on neural transmission of nociceptive inputs elicited by different kinds of thermal heating. We recorded psychophysical and EEG brain responses to radiant (laser-evoked potentials, LEPs) and contact heat stimuli (contact heat-evoked potentials, CHEPs) delivered to the dorsum and the palm of the hand in normal volunteers. Brain responses were analysed at a single-trial level, using an automated approach based on multiple linear regression. Laser stimulation of hairy and glabrous skin at the same energy elicited remarkably similar psychophysical ratings and LEPs. This finding provides strong evidence that first pain to heat does exist in glabrous skin, and suggests that similar nociceptive afferents, with the physiological properties of II-AMHs, mediate first pain to heat stimulation of glabrous and hairy skin in humans. In contrast, when contact heat stimuli were employed, a significantly higher nominal temperature had to be applied to glabrous skin in order to achieve psychophysical ratings similar to those obtained following hairy skin stimulation, and CHEPs following glabrous skin stimulation had significantly longer latencies (N2 wave, +25%; P2 wave, +24%) and smaller amplitudes (N2 wave, −40%; P2 wave, −44%) than CHEPs following hairy skin stimulation. Irrespective of the stimulated territory, CHEPs always had significantly longer latencies (hairy skin N2 wave, +75%; P2 wave, +56%) and smaller amplitudes (hairy skin N2 wave, −42%; P2 wave, −19%) than LEPs. These findings are consistent with the thickness-dependent delay and attenuation of the temperature waveform at nociceptor depth when conductive heating is applied, and suggest that the previously reported lack of first pain and microneurographical II-AMH responses following glabrous skin stimulation could have been the result of a search bias consequent to the use of long-wavelength radiant heating (i.e. CO 2 laser) as stimulation procedure.

show abstract

mentioning

confidence: 99%

Similar nociceptive afferents mediate psychophysical and electrophysiological responses to heat stimulation of glabrous and hairy skin in humans

Iannetti

Zambreanu

Tracey

2006

The Journal of Physiology

152

133

View full text Add to dashboard Cite

show abstract

“…Considerable variability in latency and amplitude is one of the characteristics of single EPs (Zerlin & Davis, 1967;Ciganek, 1969;Rosenstein et al, 1992;Purves & Boyd, 1993). This variability could be seen within and between sessions of VEP recordings from the same subject, as well as between the subjects.…”

Section: Discussionmentioning

confidence: 95%

“…In some cases where the signal-to-noise (S/N) ratio is high enough, the single EP wave forms can be observed directly in the human scalp recordings (raw data) and single EP parameters can be reliably measured (e.g., Zerlin & Davis, 1967;Shibasaki, Yamashita, Neshige, Tobimatsu & Fukui, 1985;Micheloyannis, Samara & Liakakos, 1989;Rosenstein et al, 1992;Purves & Boyd, 1993).…”

Section: G Z Rosenstein Etalmentioning

confidence: 99%

Single P100 Visual evoked potential analyses in man

Rosenstein¹,

Fufwan²,

Sohmer³

et al. 1994

International Journal of Neuroscience

View full text Add to dashboard Cite

Standards evoked potential averaging leads to a loss of information inherent in the moment to moment variability of the amplitude and latency of single evoked potentials. In order to extract this information, attempts were made to develop procedures which would allow recording of single visual evoked potentials in at least a selected group of subjects. In 11 out of 25 non-selected subjects, 43% to 86% of all stimuli (reversal checkerboard pattern elicited single visual evoked potentials (VEP) which were recognized as such by a group of independent observers. The mean amplitude and latency obtained by directly measuring the peak to peak amplitudes and peak latencies of these single VEPs (arithmetic averaging) were compared to those obtained following conventional time-locked averaging of the same data. During long-term continuous stimulation, the arithmetic averaged VEPs increased in amplitude to a steady state while the time-locked averages of the same sets of responses decreased in amplitude. This reduction was found to be closely related to the latency jitter. It may provide a better understanding of the phenomenon of habituation. This finding was confirmed in model single VEPs obtained by summing on-going pre-stimulus EEG activity with a time-locked average VEP stationary wave form. The variability of the true single VEPs was found to be less than the variability of the model single VEPs. The latency and amplitude parameters of the true single VEPs were strongly correlated with each other while those of the model single VEPs were not. These findings show that single VEPs have an inherent variability which may reflect brain processing.

show abstract

“…2,3,[6][7][8] In contrast, the ZMAD protocol used in our study is a median-based statistic. There is increasing evidence that for many applications, because of less influence by skewness, median-based techniques may be superior to mean-based techniques.…”

Section: Discussionmentioning

confidence: 99%

A Fully Implantable Subcutaneous Glucose Sensor Array: Enhanced Accuracy from Multiple Sensing Units and a Median-Based Algorithm

Ward

Casey

Quinn

et al. 2003

Diabetes Technology & Therapeutics

View full text Add to dashboard Cite

Although continuous electrochemical glucose monitoring holds promise in the management of diabetes, its utility is limited in part because of error of unclear origin. The use of redundant glucose sensors in an array might reduce such error. We hypothesized that in a subcutaneously implanted array, a median-based continuous computation that excludes outlying data would lead to more accurate glucose measurement than averaging of all signals. Each rat was implanted with an array of four sensing units, and each unit transmitted data independently to an external monitoring device. Animals underwent perturbation of glucose by insulin infusions in diabetic animals and glucose infusions in nondiabetic animals, and in both, capillary glucose monitoring was performed frequently. Repeat glucose perturbation studies were performed every 1-2 weeks. We observed that a median-based technique, the Z-score with Median Absolute Deviation (ZMAD), consistently led to greater sensing accuracy as compared with signal averaging. The ZMAD technique yielded a correlation coefficient of 0.93, and 96% of values fell in the A and B regions of the Clarke error grid, demonstrating a high degree of accuracy of the unified signal. When tested in an implanted array of glucose sensors, a median-based technique (ZMAD) yields an accurate unified signal, and its accuracy is superior to signal averaging.

show abstract

Time-shifted averaging for laser evoked potentials

Cited by 21 publications

References 16 publications

Similar nociceptive afferents mediate psychophysical and electrophysiological responses to heat stimulation of glabrous and hairy skin in humans

Similar nociceptive afferents mediate psychophysical and electrophysiological responses to heat stimulation of glabrous and hairy skin in humans

Single P100 Visual evoked potential analyses in man

A Fully Implantable Subcutaneous Glucose Sensor Array: Enhanced Accuracy from Multiple Sensing Units and a Median-Based Algorithm

Contact Info

Product

Resources

About