Papers by David Peterzell
On the nonrelation between spatial frequancyand cerebral hemispheric competence
Brain and Cognition, 1991
Developmental Psychobiology, May 1, 1993
How many and what kinds of processes mediate infant visual attention? Are they influenced by stim... more How many and what kinds of processes mediate infant visual attention? Are they influenced by stimulus "complexity?" Analyses were performed on visual fixation data from ninety 4-month-old infants; the time each infant spent looking at a black and white checkerboard pattern containing either 4 x 4, 12 x 12, or 20 x 20 checks per picture was measured for eight 10-s trials, with 10-s interstimulus intervals (Kaplan & Werner, 1986). Correlational and factor analyses revealed one significant source of individual variability (or factor) in the 4 x 4 data, and two significant sources in the 12 x 12 and 20 x 20 data. One factor gained strength over progressive trials and accounted for decreases in looking time. A second factor gained strength over the first few trials, then lost strength over the remaining trials, and accounted for initial increments in looking time. The two factors are consistent with a dualprocess model of infant response dynamics; the first may represent habituation;a decremental process, and the second may represent sensitization, an incremental process that is activated by "complex" stimuli.
Vision Research, Oct 1, 1996
The number and nature of spatial channels tuned to low spatial frequencies in photopic vision was... more The number and nature of spatial channels tuned to low spatial frequencies in photopic vision was examined by measuring individual differences in the contrast sensitivity functions (CSFS)of seven Visua]lynormal adults. Stationary, 51 cd/m2, low spatial frequency sinusoidal gratings between and 2.16 c/deg were used as stimuli. Correlational and factor analyses revealed that the set of CSFS contained only one statistical source of individual variability at spatial frequencies below 1 c/deg (tuned to a peak of about 0.8 c/deg), and a second source above 1 c/deg (tuned to about 1.4 c/deg). The sources ("factor-channels") mapped well onto the two coarsest spatial frequency channels from some existing computational models. The analysis was applied also to earlier data from 4-,6and 8-month-old infants, in which two sources of variability have been found below 1 c/deg IPeterzell, D. H., Werner, J. S. & Kaplan, P. S. (1995). Vision Research, 35, 961-980]. The combined results are consistent with the hypothesis that in photopic vision of the neonate, there are two channels witb peak sensitivities below 1 c/deg, and that these channels shift their tuning from lower to higher spatial frequencies by about a factor of four during development.
Three new visual methods for generating phantom sensations: case studies in the relief of upper and lower phantom limb pain, and benign essential tremors
Journal of Vision, Mar 23, 2010
... 1 VA San Diego Health Care System, University of California, San Diego, and Alliant Internati... more ... 1 VA San Diego Health Care System, University of California, San Diego, and Alliant International University; 2 VA San Diego Health Care System, and Alliant International University; 3 VA SanDiego Health Care System, and Alliant International University; ...
Fundamentally different representations of color and motion revealed by individual differences in perceptual scaling
Proceedings of the National Academy of Sciences of the United States of America, Jan 20, 2023
The coordinate frames for color and motion are often defined by three dimensions (e.g., responses... more The coordinate frames for color and motion are often defined by three dimensions (e.g., responses from the three types of human cone photoreceptors for color and the three dimensions of space for motion). Does this common dimensionality lead to similar perceptual representations? Here we show that the organizational principles for the representation of hue and motion direction are instead profoundly different. We compared observers’ judgments of hue and motion direction using functionally equivalent stimulus metrics, behavioral tasks, and computational analyses, and used the pattern of individual differences to decode the underlying representational structure for these features. Hue judgments were assessed using a standard “hue-scaling” task (i.e., judging the proportion of red/green and blue/yellow in each hue). Motion judgments were measured using a “motion-scaling” task (i.e., judging the proportion of left/right and up/down motion in moving dots). Analyses of the interobserver variability in hue scaling revealed multiple independent factors limited to different local regions of color space. This is inconsistent with the influences across a broad range of hues predicted by conventional color-opponent models. In contrast, variations in motion scaling were characterized by more global factors plausibly related to variation in the relative weightings of the cardinal spatial axes. These results suggest that although the coordinate frames for specifying color and motion share a common dimensional structure, the perceptual coding principles for hue and motion direction are distinct. These differences might reflect a distinction between the computational strategies required for the visual analysis of spatial vs. nonspatial attributes of the world.
Vision Research, Sep 1, 1997
A suprathreshold sinewave grating can change the amplitude of the steady-state visual evoked pote... more A suprathreshold sinewave grating can change the amplitude of the steady-state visual evoked potential (VEP) in response to a test grating if the two are close in spatial frequency (SF). The change in amplitude provides clues to underlying pattern analyzers. Masking was measured in 12 observers using the steady-state VEP. As a test grating reversed at 7 Hz, a masker of similar temporal frequency (9 Hz) but of variable SF was superimposed on it. Test gratings were 1, 3 and 8 c/deg (20% contrast). Within a 10 sec trial, the mask (20 or 40% contrast) was fixed at one of nine SFs or was swept across 19 SFs (5 octaves). The amplitude of the test response (at 14 Hz) was measured as a function of the SF of the masker. Group masking functions were broad (2-3 octaves) and revealed multiple minima. Functions for 1 and 3 c/deg tests each revealed minima near 1 and 3 c/deg. Functions for 8 c/deg tests revealed minima at 3 and 8 c/deg. Doubling the contrast of the mask from 20 to 40% increased masking but in a nonlinear fashion that enlarged the off-peak minima. Swept masks caused slightly more masking than fixed masks, and caused masked amplitudes to exceed unmasked amplitudes (i.e., enhancement) in one condition (3 c/deg test, 20% contrast mask). The data suggest that each VEP masking function reflects the outputs of multiple spatial analyzers, that a discrete set of analyzers may underlie the data, and that the efficient sweep-VEP can measure SF tuning.
Vision Research, Dec 1, 2017
A longstanding and unresolved question is how observers construct a discrete set of color categor... more A longstanding and unresolved question is how observers construct a discrete set of color categories to partition and label the continuous variations in light spectra, and how these categories might reflect the neural representation of color. We explored the properties of color naming and its relationship to color appearance by analyzing individual differences in color-naming and huescaling patterns, using factor analysis of individual differences to identify separate and shared processes underlying hue naming (labeling) and hue scaling (color appearance). Observers labeled the hues of 36 stimuli spanning different angles in cone-opponent space, using a set of eight terms corresponding to primary (red, green, blue, yellow) or binary (orange, purple, blue-green, yellowgreen) hues. The boundaries defining different terms varied mostly independently, reflecting the influence of at least seven to eight factors. This finding is inconsistent with conventional coloropponent models in which all colors derive from the relative responses of underlying red-green and blue-yellow dimensions. Instead, color categories may reflect qualitatively distinct attributes that are free to vary with the specific spectral stimuli they label. Inter-observer differences in color-naming were large and systematic, and we examined whether these differences were associated with differences in color appearance by comparing the hue-naming to color percepts assessed by hue scaling measured in the same observers (from Emery et al., submitted). Variability in both tasks again depended on multiple (7 or 8) factors, with some Varimax-rotated factors specific to hue naming or hue scaling, but others common to corresponding stimuli for both judgments. The latter suggests that at least some of the differences in how individuals name or categorize color are related to differences in how the stimuli are perceived.
Spatial Frequency Channels Revealed by Individual Differences in Contrast Sensitivity Functions: Visual Evoked Potentials from Adults and Infants
A Tripartite (Triple-Reflection) Mirror as a rehabilitative technology for the relief of upper phantom limb pain: case studies and phenomena in non-amputees
The Journal of Pain, Apr 1, 2011
Psychophysical investigations into Ramachandran’s mirror visual feedback for phantom limb pain: video-based variants for unilateral and bilateral amputees, and temporal dynamics of paresthesias
IS&T International Symposium on Electronic Imaging Science and Technology, Feb 14, 2016
Factors underlying individual differences in hue scaling
Journal of Vision, Sep 1, 2016
Vision Research, Apr 1, 1995
Contrast sensitivity functions (CSFs) of 25 infants were measured longitudinally at 4, 6 and 8 mo... more Contrast sensitivity functions (CSFs) of 25 infants were measured longitudinally at 4, 6 and 8 months of age using a preferentiaMooking method and the method of constant stimuli. Sine-wave gratings varied from 0.27 to 4.32 c/deg, contained eight unattenuated cycles (with edges tapered to uniform gray), and rose to the desired contrast in 2 sec. (1) The average CSF was described on log-log coordinates by a band-pass function. With development it increased in overall sensitivity to contrast, shifted its peak toward slightly Ifigher spatial frequencies, and increased its high frequency cutoff. (2) Log sensitivity at the CSF peak was slightly higher for female than male infants at 6 months, consistent with the hypothesis that vernier acuity (which also may differ between the sexes at this age) is partly mediated by analyzers tuned to low frequencies. (3) Within age groups the individual differences were such that log sensitivities for neighboring spatial frequencies generally correlated more highly than distant frequencies. With development the correlations among distant frequencies below 1.0 c/deg increased. Monte Carlo simulations of a model that shifts spatial analyzers to higher frequencies with age reproduced them,' results but simulations of adultlike, unshifting analyzers did not. (4) Measures taken 2 months apart tended to correlate more highly than those taken 4 months apart, though some individual differences in the CSF peak remained stable over 4 months. Contrast sensitivity Factor analysis Individual differences Infant vision Spatial frequency Visual development A set of contrast sensitivity functions (CSFs) containing log sensitivities for n spatial frequencies, each recorded for s individuals, provides two independent types of information about visual detection. Vision scientists most often derive one type, representative functions, for individual or group data by graphing contrast sensitivity or mean contrast sensitivity as a function of spatial frequency. The representative CSF is often shaped like a band-pass filter. Vision :scientists usually do not use the second type of information, which describes how individual differences obtained for one variable relate to individual differences obtained for other variables. They could, for example, examine the n x n correlation matrix to examine whether the s log contrast sensitivity values at one spatial frequency correlate significantly with the s values at any of the other spatial frequencies. The correlations represent individual differences
Perception, Jun 1, 1998
Cerebral asymmetries in sensory and perceptual processing edited by S Christman; Elsevier, Amster... more Cerebral asymmetries in sensory and perceptual processing edited by S Christman; Elsevier, Amsterdam, 1997, 580 pages, dfl 260.00 (US $149.50) ISBN 0 444 82510 X "... the same weight seems heavier to most subjects when it is placed on the left and lighter when it is placed on the right; and different weights often appear equal if the heavier is placed on the right and lighter on the left, whereas they appear unequal if the heavier is placed on the left... Since we lack any other explanation, it is likely that the difference lies in the structure of the sensory nerves. Just as the muscles on the right side are thicker than those on the left and thus more powerful, so it is not impossible that the sensory nerves on the left should be more sensitive than those on the right." _ ^ TT. . u ", u /101/1. A , n 1fV70X b Ernst Heinnch Weber (1834, in Mollon 1978) "The two cerebral hemispheres, while beginning with the same moods, predispositions, knowledge, and memories, indeed the same consciousness generally, will [when divided through the middle] thereafter develop differently according to the external relations into which each will enter."
Development of Spatial Frequency Tuned ???Covariance??? Channels: Individual Differences in the Electrophysiological (VEP) Contrast Sensitivity Function
Optometry and Vision Science, Oct 1, 1997
We investigated the spatial frequency tuned channels underlying the contrast sensitivity function... more We investigated the spatial frequency tuned channels underlying the contrast sensitivity functions (CSFs) of adults and infants. CSFs were measured in adults and in 8-, 14-, 20-, and 32-week-old infants, using the swept-contrast visual evoked potential (sweep-VEP). At each age, 8 to 21 subjects provided complete data. Subjects viewed achromatic sine wave gratings (0.3 to 8 c/deg) on a 20 degrees field presented on a CRT. Gratings were counterphased at 12 reversals/s (6 Hz). The second harmonic response was used to interpolate thresholds. We computed statistical "sources" of individual variability (or factors) underlying CSFs, then calculated the number, nature (discrete vs. continuous) and frequency tuning of "covariance" channels. CSFs from adults each contained three spatial frequency tuned covariance channels, consistent with psychophysical results spanning a similar spatial frequency range. Covariance channels in infants shifted upward in spatial frequency with age, with rapid shifts occurring between 8 and 14 weeks. The change in scale coincided with, and was probably determined by, developmental cone migration into the fovea and growth in eye size.
In search of early cortical mechanisms for color: individual variability in steady-state VEP amplitudes for hues sweeping around the isoluminant LM and S cone-opponent plane
Journal of Vision, Sep 27, 2021
Vision Research, Dec 1, 2017
Individual differences as a window into the structure and function of the visual system This spec... more Individual differences as a window into the structure and function of the visual system This special issue of Vision Research highlights the power of analyzing individual differences as a tool for understanding visual function. Investigations of visual processes often average measurements across observers to assess differences between conditions, thus treating the interobserver differences as noise. However, as the articles in this issue illustrate, the differences between observers are often systematic and can reflect important differences in the mechanisms underlying perception and performance. Characterizing these differences thus provides a unique window into these mechanisms. The studies in this issue illustrate the many ways that individual differences are being exploited to probe vision. We begin with an essay that summarizes the approach, and also points to methodological issues that should be considered in designing future experiments or interpreting past ones (Mollon, Bosten, Peterzell & Webster, 2017). We hope this will stimulate further consideration of best practices in the field. The remaining articles provide examples of applying individual differences research to vision. A quick glance reveals that these articles cover a broad swath of vision, from optics to awareness. This is not surprising because meaningful inter-observer variations are likely to arise at most if not all levels of visual coding. At each level it is fruitful to ask what patterns these differences take, and what underlying principles or processes they point to. In most cases the interesting question is not simply how people varybut why. The individual differences are a means to address the question and not an end in themselves. Finally, it will be apparent that in most cases the answers provided by individual differences rely on correlational analyses to evaluate when individual differences across tasks covary (implying a common mechanism) and when they are unrelated (implying distinct processes). The first set of articles investigates large individual differences in basic elements of vision. Alcon et al. characterize differences in optical properties of the eye and find that these variations largely fail to predict the substantial differences between observers in the subjective amplitude of accommodation, suggesting more central factors are at play (Lopez-Alcon, Marin-Franch, Fernandez-Sanchez & Lopez-Gil, 2017). Swanson et al. use perimetry to map large and very stable differences in visual fields (Swanson, Dul, Horner & Malinovsky, 2016). Their results illustrate the importance of including normal individual variation in clinical assessments. Vilidaite and Baker take advantage of individual differences to assess neural noise and the paradigms that can best evaluate it (Vilidaite & Baker, 2017), while Dieter et al. use differences in eye dominance to understand the dynamics of binocular rivalry (Dieter, Sy & Blake, 2017). Several papers focus on the perception of specific visual attributes such as color or motion. In color, Emery et al. show that differences in hue scaling and color naming are inconsistent with canonical red-green and blue-yellow channels, and instead suggest that the percepts and categorizations depend on multiple mechanisms narrowly tuned to different hue ranges (Emery, Volbrecht, Peterzell & Webster, 2017a, Emery, Volbrecht, Peterzell & Webster, 2017b). Witzel et al. analyze responses to #thedressan image that has done much to drive public interest in individual differences in color perception (Witzel, O'Regan & Hansmann-Roth, 2017). They conclude that differences in the appearance of the dress reflect differences in how individuals interpret the illuminant cues in the image, but do not arise from general differences in color constancy mechanisms. Schloss and Palmer explore color preferences, which differ not only between people but in the same person over time, and show how both can be understood within a common framework of Ecological Valence Theory, in which color preferences are assumed to be shaped by the objects we associate with colors (Schloss & Palmer, 2017). In the case of motion, McGovern et al. use the correlations between the strength of motion aftereffects and motion repulsion to identify a mechanism that is distinct from the processes controlling other contextual effects (e.g. for spatial contrast) (McGovern, Walsh, Bell & Newell, 2017). Sparrow et al. examine differences in the percepts of motion-induced blindness (in which stationary targets can disappear from view in the presence of a moving background) and how these relate to the depth ordering and motion coherence of the background (Sparrow, LaBarre & Merrill, 2017). Peterzell et al. also explore depth perception, measuring sensitivity to sinusoidal depth corrugations, and then using factor analysis to reveal separate processes at low and high frequencies (Peterzell et al., 2017). Van Boxtal et al. provide an example of measuring group rather than individual comparisons (van Boxtel, Peng, Su & Lu, 2017). Their study suggests that sensitivity to social interaction defined by global biological motion is compromised in individuals with autistic traits (van Boxtel, Peng, Su & Lu, 2017). Braddick et al. also explore global motion perception and why it varies both within and between normal and atypical neurodevelopment (Braddick, Atkinson, Akshoomoff, Newman, Curley, Gonzalez, Brown, Dale & Jernigan, 2017). Their analysis suggests that the capacity for global motion processing is tied to the integrity of structural links between parietal and frontal brain areas involved in interpreting the stimulus motion. Other papers explore individual differences in eye movements. Bargary et al. collected several measures of eye movements among a large sample of observers and show that individuals tend to have a unique "oculomotor signature" (Bargary,
Identification of Letters in the Predesignated Target Paradigm: A Word Superiority Effect for the Common Word the
American Journal of Psychology, 1990
The size of the perceptual unit used in reading was addressed using the predesignated target para... more The size of the perceptual unit used in reading was addressed using the predesignated target paradigm. Sixteen subjects viewed the following stimuli in random order: the words tee, the, tie, and toe; the nonwords eet, eht, eit, and eot; and the letters e, h, i, and o. Subjects fixated on the location of the center letter and identified the letter as e, h, i, or o, alternatives which were known to them at the onset. A word superiority effect was obtained for the common word the but not for the less common words tee, tie, and toe. The word superiority effect was attributable to bias rather than discriminability: Subjects exhibited a bias to perceive the words in this experiment as the (i.e., there was a bias to perceive h in the t e stimulus presentations). These results suggest that the common word the is processed in reading units that are larger than the letter, and that the system is biased to perceive common rather than uncommon words in data-limited conditions.
Temporal Tuning of Flicker-Sensitive Channels Derived from Individual Differences in De Lange Functions
Vision Science and its Applications
The human visual system's sensitivity to flicker, and the processes underlying this sensitivi... more The human visual system's sensitivity to flicker, and the processes underlying this sensitivity, are generally understood. The system's sensitivity to flicker is described by a bandbass function that varies with flicker rate (de Lange, 1958a, b). The processes underlying the de Lange function include narrowly tuned bandpass channels that combine to determine sensitivity.
Vision research, Dec 1, 2017
Threshold functions for sinusoidal depth corrugations typically reach their minimum (highest sens... more Threshold functions for sinusoidal depth corrugations typically reach their minimum (highest sensitivity) at spatial frequencies of 0.2-0.4 cycles/degree (cpd), with lower thresholds for horizontal than vertical corrugations at low spatial frequencies. To elucidate spatial frequency and orientation tuning of stereoscopic mechanisms, we measured the disparity sensitivity functions, and used factor analytic techniques to estimate the existence of independent underlying stereo channels. The data set (N = 30 individuals) was for horizontal and vertical corrugations of spatial frequencies ranging from 0.1 to 1.6 cpd. A principal component analysis of disparity sensitivities (log-arcsec) revealed that two significant factors accounted for 70% of the variability. Following Varimax rotation to approximate "simple structure", one factor clearly loaded onto low spatial frequencies (≤0.4 cpd), and a second was tuned to higher spatial frequencies (≥0.8 cpd). Each factor had nearly ide...
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Papers by David Peterzell