Age- and frequency-dependent changes in dynamic contrast perception in visual snow syndrome

Objective Patients with visual snow syndrome (VSS) suffer from a debilitating continuous (“TV noise-like”) visual disturbance. They report problems with vision at night and palinopsia despite normal visual acuity. The underlying pathophysiology of VSS is largely unknown. Currently, it is a clinical diagnosis based on the patient’s history, an objective test is not available. Here, we tested the hypothesis that patients with VSS have an increased threshold for detecting visual contrasts at particular temporal frequencies by measuring dynamic contrast detection-thresholds. Methods Twenty patients with VSS were compared to age-, gender-, migraine- and aura-matched controls in this case-control study. Subjects were shown bars randomly tilted to the left or right, flickering at six different frequencies (15 Hz, 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz). The contrast threshold (CT) for detection of left or right tilt was measured in a two-alternative adaptive forced-choice procedure (QUEST). The threshold was defined as the Michelson contrast necessary to achieve the correct response in 75% of the cases. Results The CT increased for higher flicker frequencies (ANOVA: main effect frequency: F (5,180) = 942; p < 0.001), with an additional significant frequency*diagnosis interaction (ANOVA: F (5,180) = 5.00; p < 0.001). This interaction effect was due to an increased CT at a flicker frequency of 15 Hz in the VSS cohort (VSS: MC = 1.17%; controls: MC = 0.77%). At the other frequencies, group comparisons revealed no differences. Furthermore, in the VSS cohort we observed an increase of CT with higher age (r = 0.69; p < 0.001), which was not seen in controls (r = 0.30; p = 0.20). Conclusions This study demonstrates a lower visual contrast sensitivity exclusively at 15 Hz in VSS patients and demonstrates frequency-dependent differences in dynamic contrast vision. The peak sensitivities of both parvo- and magnocellular visual pathways are close to a frequency of about 10 Hz. Therefore, this frequency seems to be of crucial importance in everyday life. Thus, it seems plausible that the impairment of contrast sensitivity at 15 Hz might be an important pathophysiological correlate of VSS. Furthermore, the overall age-related decrease in contrast sensitivity only in VSS patients underscores the vulnerability of dynamic contrast detection in VSS patients. Dynamic CT detection seems to be a promising neurophysiological test that may contribute to the diagnosis of VSS.

The effect of blue light filtering lenses on speed perception

Blue-light filtering lenses (BFLs) are marketed to protect the eyes from blue light that may be hazardous to the visual system. Because BFLs attenuate light, they reduce object contrast, which may impact visual behaviours such as the perception of object speed which reduces with contrast. In the present study, we investigated whether speed perception is affected by BFLs. Using a two-interval forced-choice procedure in conjunction with Method of Constant Stimuli, participants (n = 20) judged whether the perceived speed of a moving test stimulus (1.5–4.5°/s) viewed through a BFL was faster than a reference stimulus (2.75°/s) viewed through a clear lens. This procedure was repeated for 3 different BFL brands and chromatic and achromatic stimuli. Psychometric function fits provided an estimate of the speed at which both test and reference stimuli were matched. We find that the perceived speed of both chromatic and achromatic test stimuli was reduced by 6 to 20% when viewed through BFLs, and lenses that attenuated the most blue-light produced the largest reductions in perceived speed. Our findings indicate that BFLs whilst may reduce exposure to hazardous blue light, have unintended consequences to important visual behaviours such as motion perception.

Towards a common code for difficulty: Navigating a narrow gap is like memorizing an extra digit

What makes a task hard or easy? The question seems easy, but answering it has been hard. The only consensus has been that, all else being equal, easy tasks can be performed by more individuals than hard tasks, and easy tasks are usually preferred over hard tasks. Feghhi and Rosenbaum (Journal of Experimental Psychology: Human Perception and Performance, 45, 983–994, 2019) asked whether task difficulty might reflect a single amodal quantity. Based on their subjects’ two-alternative forced-choice data from tasks involving choices of tasks with graded physical and mental challenges, the authors showed that the difficulty of passing through a narrow gap rather than a wide gap was psychologically equivalent to memorizing an extra .55 digits. In the present study, we extended this approach by adding new arguments for the hypothesis that task difficulty might reflect a single amodal quantity (inspired by considerations of physics, economics, and the common code hypothesis for the study of perception and action), and we tested narrower gaps than before to see whether we would find a larger equivalent memory-digit. Consistent with our prediction, we obtained a value of .95. We suggest that our multi-modal two-alternative forced-choice procedure can pave the way toward a better understanding of task difficulty.

The Fallacy of an Airtight Alibi: Understanding Human Memory for “Where” Using Experience Sampling

A primary challenge for alibi-generation research is establishing the ground truth of real-world events of interest. In the current study, we used a smartphone app to record data on adult participants ( N = 51) for a month prior to a memory test. The app captured accelerometry data, GPS locations, and audio environments every 10 min. After a week-long retention interval, we asked participants to identify where they were at a given time from among four alternatives. Participants were incorrect 36% of the time. Furthermore, our forced-choice procedure allowed us to conduct a conditional logit analysis to assess the different aspects of the events that the participants experienced and their relative importance to the decision process. We found strong evidence that participants confuse days across weeks. In addition, people often confused weeks in general and also hours across days. Similarity of location induced more errors than similarity of audio environments or movement types.

High Ripple-Density Resolution for Discriminating Between Rippled and Nonrippled Signals: Effect of Temporal Processing or Combination Products?

The goal of the study was to investigate the role of combination products in the higher ripple-density resolution estimates obtained by discrimination between a spectrally rippled and a nonrippled noise signal than that obtained by discrimination between two rippled signals. To attain this goal, a noise band was used to mask the frequency band of expected low-frequency combination products. A three-alternative forced-choice procedure with adaptive ripple-density variation was used. The mean background (unmasked) ripple-density resolution was 9.8 ripples/oct for rippled reference signals and 21.8 ripples/oct for nonrippled reference signals. Low-frequency maskers reduced the ripple-density resolution. For masker levels from −10 to 10 dB re. signal, the ripple-density resolution for nonrippled reference signals was approximately twice as high as that for rippled reference signals. At a masker level as high as 20 dB re. signal, the ripple-density resolution decreased in both discrimination tasks. This result leads to the conclusion that low-frequency combination products are not responsible for the task-dependent difference in ripple-density resolution estimates.

‘The last channel’: vision at the temporal margin of the field

The human visual field, on the temporal side, extends to at least 90° from the line of sight. Using a two-alternative forced-choice procedure in which observers are asked to report the direction of motion of a Gabor patch, and taking precautions to exclude unconscious eye movements in the direction of the stimulus, we show that the limiting eccentricity of image-forming vision can be established with precision. There are large, but reliable, individual differences in the limiting eccentricity. The limiting eccentricity exhibits a dependence on log contrast; but it is not reduced when the modulation visible to the rods is attenuated, a result compatible with the histological evidence that the outermost part of the retina exhibits a high density of cones. Our working hypothesis is that only one type of neural channel is present in the far periphery of the retina, a channel that responds to temporally modulated stimuli of low spatial frequency and that is directionally selective.

The Fallacy of an Airtight Alibi: Understanding Human Memory for Where Using Experience Sampling

A primary challenge for alibi generation research is establishing the ground truth of the real world events of interest. We used a smartphone app to record data on adult participants for a month prior to a memory test. The app captured their accelerometry continuously and their GPS location and sound environment every ten minutes. After a week retention interval, we asked participants to identify where they were at a given time from among four alternatives. Participants were incorrect 36% of the time. Furthermore, our forced choice procedure allowed us to conduct a conditional logit analysis to assess the relative importance of different aspects of the events to the decision process. We found strong evidence that participants confuse days across weeks. In addition, people often confused weeks in general and also hours across days. Similarity of location induced more errors than similarity of sound environments or movement types.

A Forced-Choice Procedure to Assess the Acute Relative Reinforcing Effects of Nicotine Dose per se in Humans

Introduction A method to assess acute reinforcement due to nicotine may aid identification of doses needed to maintain dependence. After describing development of a forced-choice procedure, results are presented from two studies using it to determine the relative reinforcing effects of nicotine dose per se. Aims and Methods Choice between a higher versus a very low or no nicotine option, via smoking (Study 1, n = 59) and via nasal spray (Study 2, n = 42), was assessed in nontreatment-seeking dependent smokers abstinent overnight. Using a within-subject design, different nicotine levels for each product were administered under blind conditions, initially to assess their discriminability (Study 1: 1.3–17 mg/g each vs. 0.4 mg/g nicotine Spectrum cigarettes; Study 2: 2.5 µg/kg vs. 0 µg/kg nicotine per spray). At the end of sessions for each study, participants engaged in forced-choice trials to assess preference, requiring a fixed number of puffs/sprays for one and/or the other. Results Confirming the procedure’s validity, the choice of the higher nicotine option was significantly greater than that for the very low or no nicotine option in both studies. In Study 1, choice relative to 0.4 mg/g was greater for cigarettes 5.3 mg/g or more but not 2.3 mg/g or less (p = .003 for the interaction of higher content vs. 0.4 mg/g comparison). In Study 2, choice was greater for the nicotine versus placebo spray (p &lt; .005), as nicotine was preferred nearly twice as much as the placebo. Conclusion This forced-choice procedure may efficiently determine the relative reinforcing value of a nicotine dose per se. Implications The forced-choice procedure described here may identify nicotine doses that are acutely reinforcing in dependent smokers. A priori research of choice comparisons between small versus zero nicotine doses could inform clinical research in larger and more diverse samples to determine nicotine contents in cigarettes, and perhaps in other commercial products, that are not reinforcing and, thus, likely to reduce the risk of their addictiveness. This procedure may also be applicable to assessing changes in acute nicotine reinforcement due to different product formulations, novel drugs, or other manipulations, perhaps helping inform development of new interventions for cessation or harm reduction.

Comparing Rapid and Traditional Forward-Masked Spatial Tuning Curves in Cochlear-Implant Users

A rapid forward-masked spatial tuning curve measurement procedure, based on Bekesy tracking, was adapted and evaluated for use with cochlear implants. Twelve postlingually-deafened adult cochlear-implant users participated. Spatial tuning curves using the new procedure and using a traditional forced-choice adaptive procedure resulted in similar estimates of parameters. The Bekesy-tracking method was almost 3 times faster than the forced-choice procedure, but its test–retest reliability was significantly poorer. Although too time-consuming for general clinical use, the new method may have some benefits in individual cases, where identifying electrodes with poor spatial selectivity as candidates for deactivation is deemed necessary.

Pure-Tone Frequency Discrimination in Preschoolers, Young School-Age Children, and Adults

Purpose Published data indicate nearly adultlike frequency discrimination in infants but large child–adult differences for school-age children. This study evaluated the role that differences in measurement procedures and stimuli may have played in the apparent nonmonotonicity. Frequency discrimination was assessed in preschoolers, young school-age children, and adults using stimuli and procedures that have previously been used to test infants. Method Listeners were preschoolers (3–4 years), young school-age children (5–6 years), and adults (19–38 years). Performance was assessed using a single-interval, observer-based method and a continuous train of stimuli, similar to that previously used to evaluate infants. Testing was completed using 500- and 5000-Hz standard tones, fixed within a set of trials. Thresholds for frequency discrimination were obtained using an adaptive, two-down one-up procedure. Adults and most school-age children responded by raising their hands. An observer-based, conditioned-play response was used to test preschoolers and those school-age children for whom the hand-raise procedure was not effective for conditioning. Results Results suggest an effect of age and frequency on thresholds but no interaction between these 2 factors. A lower proportion of preschoolers completed training compared with young school-age children. For those children who completed training, however, thresholds did not improve significantly with age; both groups of children performed more poorly than adults. Performance was better for the 500-Hz standard frequency compared with the 5000-Hz standard frequency. Conclusions Thresholds for school-age children were broadly similar to those previously observed using a forced-choice procedure. Although there was a trend for improved performance with increasing age, no significant age effect was observed between preschoolers and school-age children. The practice of excluding participants based on failure to meet conditioning criteria in an observer-based task could contribute to the relatively good performance observed for preschoolers in this study and the adultlike performance previously observed in infants.