Comparison of the reliability of multifocal visual evoked cortical potentials generated by pattern reversal and pattern pulse stimulation

Abstract

This study compared the effectiveness of the multifocal visual evoked cortical potentials (mfVEP) elicited by pattern pulse stimulation with that of pattern reversal in producing reliable responses (signal-to-noise ratio >1.359). Participants were 14 healthy subjects. Visual stimulation was obtained using a 60-sector dartboard display consisting of 6 concentric rings presented in either pulse or reversal mode. Each sector, consisting of 16 checks at 99% Michelson contrast and 80 cd/m2 mean luminance, was controlled by a binary m-sequence in the time domain. The signal-to-noise ratio was generally larger in the pattern reversal than in the pattern pulse mode. The number of reliable responses was similar in the central sectors for the two stimulation modes. At the periphery, pattern reversal showed a larger number of reliable responses. Pattern pulse stimuli performed similarly to pattern reversal stimuli to generate reliable waveforms in R1 and R2. The advantage of using both protocols to study mfVEP responses is their complementarity: in some patients, reliable waveforms in specific sectors may be obtained with only one of the two methods. The joint analysis of pattern reversal and pattern pulse stimuli increased the rate of reliability for central sectors by 7.14% in R1, 5.35% in R2, 4.76% in R3, 3.57% in R4, 2.97% in R5, and 1.78% in R6. From R1 to R4 the reliability to generate mfVEPs was above 70% when using both protocols. Thus, for a very high reliability and thorough examination of visual performance, it is recommended to use both stimulation protocols.

Empirical mode decomposition processing to improve multifocal-visual-evoked-potential signal analysis in multiple sclerosis

“…In this context, various studies have attempted to improve the diagnostic capacity of the mfVEP technique either by enhancing the visual stimulus parameters [ 10 ], by altering the number of electrodes used and their localization, by adding virtual channels [ 11 ], by investigating offline signal processing methods such as principal component analysis [ 12 ], by using wavelets [ 13 ] or by applying Prony’s method as a filter [ 14 ].…”

A new method for quantifying mfVEP signal intensity in multiple sclerosis

“…Improvements in various aspects of this technique (visual stimulation [3,4], electrode number and position [5,6], signal analysis and classification [7][8][9], etc.) have enhanced its clinical utility in diagnosis of diseases such as glaucoma, optic neuritis (ON), multiple sclerosis (MS) and other pathologies that affect the visual pathway.…”

“…Another possibility is to use the signal-to-noise ratio (SNR) in each of the sectors of the visual field [4,21]. Here, the SNR values are converted into a z-score relative to a normal distribution derived from 100 control subjects [22,23].…”

“…The monocular response amplitude, defined as SNR, is used to analyse mfVEP signals in multiple sclerosis patients [24]. The type of analysis could be use to evaluate the advantages of using an mfVEP-signal prediction method on various points on the skull [25]; to compare various multifocal visual stimulation methods [4]; or to evaluate the effects of eccentricity on contrast response characteristics [21].…”