Pattern-onset stimulation boosts central multifocal VEP responses

Hoffmann, Michael B.; Straube, Sirko; Bach, Michael

doi:10.1167/3.6.4

Cited by 38 publications

(35 citation statements)

References 19 publications

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“…Thus, the strong eccentricity dependence rules out all known forms of lateral masking except crowding and surround suppression. Surround suppression is similar to crowding in many ways, but we can rule it out because it only occurs when the flankers have higher contrast than the target (Chubb, Sperling, & Solomon, 1989;Petrov & McKee, 2006;Snowden & Hammett, 1998;Xing & Heeger, 2001;Zenger-Landolt & Koch, 2001), whereas here the target and flankers have equal contrast. We show that performance on the classic flanked letter task and the Legge et al (2001) variation is determined solely by the ratio of actual to critical spacing (predicted by Bouma's law), independent of size, spacing, and eccentricity per se.…”

Section: The Visual Span Is the Uncrowded Spanmentioning

confidence: 99%

Crowding and eccentricity determine reading rate

et al. 2007

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Bouma's law of crowding predicts an uncrowded central window through which we can read and a crowded periphery through which we cannot. The old discovery that readers make several fixations per second, rather than a continuous sweep across the text, suggests that reading is limited by the number of letters that can be acquired in one fixation, without moving one's eyes. That "visual span" has been measured in various ways, but remains unexplained. Here we show (1) that the visual span is simply the number of characters that are not crowded and (2) that, at each vertical eccentricity, reading rate is proportional to the uncrowded span. We measure rapid serial visual presentation (RSVP) reading rate for text, in both original and scrambled word order, as a function of size and spacing at central and peripheral locations. As text size increases, reading rate rises abruptly from zero to maximum rate. This classic reading rate curve consists of a cliff and a plateau, characterized by two parameters, critical print size and maximum reading rate. Joining two ideas from the literature explains the whole curve. These ideas are Bouma's law of crowding and Legge's conjecture that reading rate is proportional to visual span. We show that Legge's visual span is the uncrowded span predicted by Bouma's law. This result joins Bouma and Legge to explain reading rate's dependence on letter size and spacing. Well-corrected fluent observers reading ordinary text with adequate light are limited by letter spacing (crowding), not size (acuity). More generally, it seems that this account holds true, independent of size, contrast, and luminance, provided only that text contrast is at least four times the threshold contrast for an isolated letter. For any given spacing, there is a central uncrowded span through which we read. This uncrowded span model explains the shape of the reading rate curve. We test the model in several ways. We use a "silent substitution" technique to measure the uncrowded span during reading. These substitutions spoil letter identification but are undetectable when the letters are crowded. Critical spacing is the smallest distance between letters that avoids crowding. We find that the critical spacing for letter identification predicts both the critical spacing and the span for reading. Thus, crowding predicts the parameters that characterize both the cliff and the plateau of the reading rate curve. Previous studies have found worrisome differences across observers and laboratories in the measured peripheral reading rates for ordinary text, which may reflect differences in print exposure, but we find that reading rate is much more consistent when word order is scrambled. In all conditions tested--all sizes and spacings, central and peripheral, ordered and scrambled--reading is limited by crowding. For each observer, at each vertical eccentricity, reading rate is proportional to the uncrowded span.

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Section: The Visual Span Is the Uncrowded Spanmentioning

confidence: 99%

Crowding and eccentricity determine reading rate

et al. 2007

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“…For quantitative analysis we employed the "mean noise-window signal-tonoise ratio" measure (SNR) as described by Zhang [19]. Briefly, the RMS value from a "signal window" (45-150 ms after stimulus onset) is compared to the RMS from a "noise window" (325-430 ms); in a previous study we found this to be a reliable objective measure [8]. Only traces with an SNR^0.5 were analysed further.…”

Section: Analysis and Statisticsmentioning

confidence: 99%

The influence of defocus on multifocal visual evoked potentials

Pieh¹,

Hoffmann

Bach³

2004

Graefe's Arch Clin Exp Ophthalmol

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“…Since for regularly used pattern-related VEPs there is a drop of amplitudes when stimulus is presented in periphery, e.g. the pattern-onset EPs can bring useful results only up to about 15°of eccentricity [28], we assume that the centrally masked expanding-contracting motion can produce larger responses and thus this type of motion-onset VEPs might serve as a simple objective test of peripheral vision.…”

Section: Discussionmentioning

confidence: 99%

Motion-onset VEPs to translating, radial, rotating and spiral stimuli

et al. 2004

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Motion-onset related visual evoked potentials (M-VEPs) were recorded as a result of the three basic (translating, radial and rotating) and one complex (spiral) motion stimulations in five subjects. Low contrast, retinotopically scaled patterns evoked potentials with major motion-onset specific negativity N160 with maximum in the parieto-temporal region. All multidirectional motion stimuli elicited the motion-onset response of significantly higher amplitude and shorter latency compared to the translating (unidirectional) motion. The rotation-onset evoked potentials had significantly shorter latencies than the rest of explored stimuli. The most stable responses with the largest N160 amplitude were recorded to the radial motion. After masking of the central 20 degrees of the visual field these motion-onset VEPs were acquired without statistically significant amplitude drop. The efficiency and usefulness of the radial stimulus is presented in two clinical cases.

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Pattern-onset stimulation boosts central multifocal VEP responses

Cited by 38 publications

References 19 publications

Crowding and eccentricity determine reading rate

Crowding and eccentricity determine reading rate

The influence of defocus on multifocal visual evoked potentials

Motion-onset VEPs to translating, radial, rotating and spiral stimuli

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