The impact of stimulus configuration on visual short-term memory decline in normal aging and mild cognitive impairment.

INTRODUCTION: When we memorize simultaneous items, we not only store information about specific items and/or their locations but also how items are related to each other. Such relational information can be parsed into spatial (spatial configuration) and identity (object configuration) components. Both these configurations are found to support performance during a visual short-term memory (VSTM) task in young adults. How the VSTM performance of older adults is influenced by object/spatial configuration is less understood, which this study investigated. METHODS: Twenty-nine young adults, 29 normally aging older adults, and 20 older adults with mild cognitive impairment (MCI) completed two yes-no memory-recognition experiments for four simultaneously presented items (2.5 s). Test display items were presented either at the same locations as the memory items (Experiment 1) or were globally shifted (Experiment 2). One of the test display items (target) was highlighted with a square box; participants indicated whether this item was shown in the preceding memory display. Both experiments comprised four conditions where nontarget items changed as follows: (i) nontarget items remained the same; (ii) nontarget items were replaced by new items; (iii) nontarget items switched locations; (iv) nontarget items were replaced by square boxes. RESULTS: Performance (% correct) in both older groups was significantly reduced than young adults in both experiments and each condition. For the MCI adults, significantly reduced performance (vs. normal older adults) was found only for Experiment 1. CONCLUSION: VSTM for simultaneous items declines significantly in normal aging; the decline is not influenced differently by spatial/object configuration change. The ability of VSTM to differentiate MCI from normal cognitive aging is apparent only where the spatial configuration of stimuli is retained at original locations. Findings are discussed in terms of the reduced ability to inhibit irrelevant items and location priming (by repetition) deficits.

The validity of abbreviated forms of the National Adult Reading Test and Spot-the-Word 2 for estimating full-scale IQ.

ABSTRACTIn this study, we validate an earlier proposal for an abridged 17-item National Adult Reading Test (NART) by comparing its performance in estimating full-scale IQ against both the full test and the Spot-the-Word 2 (STW-2) test in a new cohort. We also compare the performance of the 17-item NART to two previous attempts to shorten this test, the Mini-NART and the Short NART. Findings include that NART 17 is numerically stronger and statistically equivalent to the other short variants, the full 50-word NART, and STW-2. Unlike the Short NART, the 17-item NART is usable for participants of all ability levels rather than only those with low reading ability, while offering equally precise premorbid estimates. We also compute that two-thirds of STW-2 is ostensibly redundant for full-scale IQ estimation and we, therefore, propose that, subject to additional verification in an independent sample, an abridged version of this test may also benefit clinical practice.

Perspectives of a new sport-specific Para Shooting classification system for athletes with vision impairment.

The International Paralympic Committee (IPC) and individual sports federations have established the need to develop evidence-based systems of classification for athletes with vision impairment (VI) that may differ depending on the visual demands of each sport. As a consequence, research has been conducted that led to a new classification system for athletes competing in VI shooting. The purpose of this study was to canvas the experiences of key stakeholders (athletes, coaches and classifiers) when the new system of classification was implemented. Twenty-eight participants (17 athletes, 7 coaches and 4 classifiers) completed a questionnaire to rate their experiences of the previous and new classification systems and were interviewed to gain richer insights into their opinions. It was apparent that the changes to the classification system were not adequately communicated to the athletes in particular, and that the classifiers may require a better understanding of the principles of evidence-based classification. The new system was perceived to be significantly more specific for VI shooting and intentional misrepresentation was observed to be significantly less likely than when using the old system. This research provides valuable insights into both the positive and negative experiences of key stakeholders experiencing change in a classification system.

Preference for Lighting Chromaticity in Migraine With Aura.

OBJECTIVE: We studied the color of lighting chosen as comfortable for reading by individuals with migraine and controls. We explored the effects of the chosen color on visual performance. BACKGROUND: It has been reported that individuals who experience migraine with aura (MWA) choose, as comfortable for reading, light that is more strongly saturated in color than that chosen by individuals without migraine. METHODS: A convenience sample of 18 individuals who experienced MWA, 18 without aura, and 18 controls without migraine participated in a cross-sectional laboratory study at Anglia Ruskin University. We used an Intuitive Colorimeter that illuminated text with colored light and permitted the separate control of hue (color) and saturation (strength of color) without a change in luminance. We selected individuals with migraine and healthy controls from the general population. They were headache-free in the 48 hours prior to testing. We used a routine that permitted the selection of the most comfortable hue from 12 alternatives and then alternately optimized the saturation and hue using small changes, thereby allowing for color adaptation. Visual performance at a word search task was measured under white light and under light of a color chosen as comfortable, using colored lenses. RESULTS: Healthy individuals chose light with chromaticity close to the Planckian locus, which approximates the chromaticities of daylight and most electric lighting. The distance from the locus averaged 0.029 (SD 0.021). Individuals who experienced MWA chose strongly saturated colors well away from the Planckian locus (average distance 0.056, SD 0.022). Individuals who experienced migraine without aura chose intermediate chromaticities (average distance 0.034, SD 0.022). Overall there was a large statistically significant difference between participant groups that explained 24% variance. Visual search time of individuals with migraine aura decreased from 22.5 to 16.8 s when light of the chosen color was provided using tinted lenses (the average increase in search speed was 45.7%). The lenses had no statistically significant effect on the performance of individuals without migraine aura. CONCLUSIONS: Individuals who experienced MWA selected as comfortable colors that deviated from the lighting typically experienced in everyday life. Possibly, individuals who experience MWA may be more susceptible to photophobia under typical lighting. Visual performance was improved using lenses that provided light of the chosen comfortable color. The spectral power of that choice showed no evident relationship to melanopic energy (energy captured by the intrinsically photosensitive retinal ganglion cells).

How does aging influence object-location and name-location binding during a visual short-term memory task?

Objective: Age-related impairments in human visual short-term memory (VSTM) may reflect a reduced ability to retain bound object representations, viz., object form, name, spatial, and temporal location (so called 'memory sources'). Our objective is to examine how healthy aging affects VSTM in a battery of memory recognition tasks in which sequentially presented objects, locations, and names (as auditory stimuli) were learned, with one component cued at test.Methods: Thirty-six young healthy adults (18-30 years) and 36 normally aging older adults (>60 years with no underlying health and vision issues) completed five VSTM tasks: 1. Object recognition for two or four objects; 2. Spatial location recognition for two or four objects; 3. Bound object-location recognition for two or four objects; 4. Object recognition with location priming for two or four objects; 5. Bound name (auditory)-location (cross-modal) recognition for four objects.Results: Significantly lower performance for older adults was found in spatial location recognition [task 2, p = 0.03], bound object-location recognition [task 3, p = 0.001], object recognition with location priming [task 4, p = 0.02], and bound name-location recognition [task 5, p = 0.001, independent samples t-test] tasks. A significant age group-task interaction was found (p = 0.02).Conclusion: Performance for all tests except test 1 was impaired in older adults. Lower performance for older adults was most significant in VSTM tasks requiring object-location (visual only) or name-location (auditory and visual) binding. The findings are compatible with the 'memory source' model, demonstrating that age-related binding performance is influenced by spatial coding and location priming deficits.

Comparison of methods for estimating premorbid intelligence.

To evaluate impact of neurological injury on cognitive performance it is typically necessary to derive a baseline (or "premorbid") estimate of a patient's general cognitive ability prior to the onset of impairment. In this paper, we consider a range of common methods for producing this estimate, including those based on current best performance, embedded "hold/no-hold" tests, demographic information, and word reading ability. Ninety-two neurologically healthy adult participants were assessed on the full Wechsler Adult Intelligence Scale - Fourth Edition (WAIS-IV; Wechsler, D. (2008). Wechsler Adult Intelligence Scale (4th ed.). San Antonio, TX: Pearson Assessment.) and on two widely used word reading tests: National Adult Reading Test (NART; Nelson, H. E. (1982). National Adult Reading Test (NART): For the assessment of premorbid intelligence in patients with dementia: Test manual. Windsor: NFER-Nelson.; Nelson, H. E., & Willison, J. (1991). National Adult Reading Test (NART). Windsor: NFER-Nelson.) and Wechsler Test of Adult Reading (WTAR; Wechsler, D. (2001). Wechsler Test of Adult Reading: WTAR. San Antonio, TX: Psychological Corporation.). Our findings indicate that reading tests provide the most reliable and precise estimates of WAIS-IV full-scale IQ, although the addition of demographic data provides modest improvement. Nevertheless, we observed considerable variability in correlations between NART/WTAR scores and individual WAIS-IV indices, which indicated particular usefulness in estimating more crystallised premorbid abilities (as represented by the verbal comprehension and general ability indices) relative to fluid abilities (working memory and perceptual reasoning indices). We discuss and encourage the development of new methods for improving premorbid estimates of cognitive abilities in neurological patients.

A genetic algorithm to find optimal reading test word subsets for estimating full-scale IQ.

In clinical neuropsychology the cognitive abilities of neurological patients are commonly estimated using well-established paper-based tests. Typically, scores on some tests remain relatively well preserved, whilst others exhibit a significant and disproportionate decline. Scores on those tests that measure preserved cognitive functions (so-called 'hold' tests) may be used to estimate premorbid abilities, including scores in non-hold tests that would have been expected prior to the onset of cognitive impairment. Many hold tests entail word reading, with each word being graded as correctly or incorrectly pronounced. Inevitably, such tests are likely to contain words that provide little or no diagnostic power (i.e., can be eliminated without negatively affecting prediction accuracy). In this paper, a genetic algorithm is developed and demonstrated, using n = 92 neurologically healthy participants, to identify optimal word subsets from the National Adult Reading Test that minimize the mean error in predicting the most widely used clinical measure of IQ and cognitive ability, the Wechsler Adult Intelligence Scale Fourth Edition IQ. In addition to requiring only 17-20 of the original 50 words (suggesting that this test could be revised to be up to 66% shorter) and minimizing mean prediction error, the algorithm increases the proportion of the variance in the predicted variable explained in comparison to using all words (from r2 = 0.46 to r2 = 0.61). In a clinical setting this would improve estimates of premorbid cognitive function and, if an abbreviated revision to this test were to be adopted, reduce the arduousness of the test for patients. The proposed method is evaluated with jackknifing and leave one out cross validation. The general approach may be used to optimize the relationship between any two psychological tests by finding the question subset in one test that minimizes the prediction error in a second test by training the genetic algorithm using data collected from participants upon whom both tests have been administered. This approach may also be used to develop new predictive tests, since it provides a method to identify an optimal subset of a set of candidate questions (for which empirical data have been collected) that maximizes prediction accuracy and the proportion of variance in the predicted variable that can be explained.

The National Adult Reading Test: restandardisation against the Wechsler Adult Intelligence Scale-Fourth edition.

Since publication in 1982, the 50-item National Adult Reading Test (NART; Nelson, 1982; NART-R; Nelson & Willison, 1991) has remained a widely adopted method for estimating premorbid intelligence both for clinical and research purposes. However, the NART has not been standardised against the most recent revisions of the Wechsler Adult Intelligence Scale (WAIS-III; Wechsler, 1997, and WAIS-IV; Wechsler, 2008). Our objective, therefore, was to produce reliable standardised estimates of WAIS-IV IQ from the NART. Ninety-two neurologically healthy British adults were assessed and regression equations calculated to produce population estimates of WAIS-IV full-scale IQ (FSIQ) and constituent index scores. Results showed strong NART/WAIS-IV FSIQ correlations with more moderate correlations observed between NART error and constituent index scores. FSIQ estimates were closely similar to the published WAIS and WAIS-R estimates at the high end of the distribution, but at the lower end were approximately equidistant from the highly discrepant WAIS (low) and WAIS-R (high) values. We conclude that the NART is likely to remain an important tool for estimating the impact of neurological damage on general cognitive ability. We advise caution in the use of older published WAIS and/or WAIS-R estimates for estimating premorbid WAIS-IV FSIQ, particularly for those with low NART scores.

Patients with Mild Cognitive Impairment Show Lower Visual Short-Term Memory Performance in Feature Binding Tasks.

BACKGROUND: Early cognitive changes in people at risk of developing dementia may be detected using behavioral tests that examine the performance of typically affected brain areas, such as the hippocampi. An important cognitive function supported by the hippocampi is memory binding, in which object features are associated to create a unified percept. AIM: To compare visual short-term memory (VSTM) binding performance for object names, locations, and identities between a participant group known to be at higher risk of developing dementia (mild cognitive impairment [MCI]) and healthily aging controls. METHODS: Ten MCI and 10 control participants completed five VSTM tests that differed in their requirement of remembering bound or unbound object names, locations, and identities, along with a standard neuropsychological test (Addenbrooke's Cognitive Examination [ACE]-III). RESULTS: The performance of the MCI participants was selectively and significantly lower than that of the healthily aging controls for memory tasks that required object-location or name-location binding. CONCLUSION: Tasks that measure unimodal (object-location) and crossmodal (name-location) binding performance appear to be particularly effective for the detection of early cognitive changes in those at higher risk of developing dementia due to Alzheimer's disease.

Spatiotemporal proximity effects in visual short-term memory examined by target-nontarget analysis.

Visual short-term memory (VSTM) is a limited-capacity system that holds a small number of objects online simultaneously, implying that competition for limited storage resources occurs (Phillips, 1974). How the spatial and temporal proximity of stimuli affects this competition is unclear. In this 2-experiment study, we examined the effect of the spatial and temporal separation of real-world memory targets and erroneously selected nontarget items examined during location-recognition and object-recall tasks. In Experiment 1 (the location-recognition task), our test display comprised either the picture or name of 1 previously examined memory stimulus (rendered above as the stimulus-display area), together with numbered square boxes at each of the memory-stimulus locations used in that trial. Participants were asked to report the number inside the square box corresponding to the location at which the cued object was originally presented. In Experiment 2 (the object-recall task), the test display comprised a single empty square box presented at 1 memory-stimulus location. Participants were asked to report the name of the object presented at that location. In both experiments, nontarget objects that were spatially and temporally proximal to the memory target were confused more often than nontarget objects that were spatially and temporally distant (i.e., a spatiotemporal proximity effect); this effect generalized across memory tasks, and the object feature (picture or name) that cued the test-display memory target. Our findings are discussed in terms of spatial and temporal confusion "fields" in VSTM, wherein objects occupy diffuse loci in a spatiotemporal coordinate system, wherein neighboring locations are more susceptible to confusion. (PsycINFO Database Record

Myopes experience greater contrast adaptation during reading.

In this study, we investigated whether reading influences contrast adaptation differently in young adult emmetropic and myopic participants at the spatial frequencies created by text rows and character strokes. Pre-adaptation contrast sensitivity was measured for test gratings with spatial frequencies of 1cdeg(-1) and 4cdeg(-1), presented horizontally and vertically. Participants then adapted to reading text corresponding to the horizontal "row frequency" of text (1cdeg(-1)), and vertical "stroke frequency" of the characters (4cdeg(-1)) for 180s. Following this, post-adaptation contrast sensitivity was measured. Twenty young adults (10 myopes, 10 emmetropes) optimally corrected for the viewing distance participated. There was a significant reduction in logCS post-text adaptation (relative to pre-adaptation logCS) at the row frequency (1cdeg(-1) horizontal) but not at the stroke frequency (4cdeg(-1) vertical). logCS changes due to adaptation at 1cdeg(-1) horizontal were significant in both emmetropes and myopes. Comparing the two refractive groups, myopic participants showed significantly greater adaptation compared to emmetropic participants. Reading text on a screen induces contrast adaptation in young adult observers. Myopic participants were found to exhibit greater contrast adaptation than emmetropes at the spatial frequency corresponding to the text row frequency. No contrast adaptation was observed at the text stroke frequency in either participant group. The greater contrast adaptation experienced by myopes after reading warrants further investigation to better understand the relationship between near work and myopia development.

Change Detection in Visual Short-Term Memory: The Relative Impact of Pairwise Switches and Identity Substitutions.

Numerous kinds of visual event challenge our ability to keep track of the objects that populate our visual environment from moment to moment. These include blinks, occlusion, shifting visual attention, and changes to object's visual and spatial properties over time. These visual events may lead to objects falling out of our visual awareness, but can also lead to unnoticed changes, such as undetected object replacements and positional exchanges. Current visual memory models do not predict which visual changes are likely to be the most difficult to detect. We examine the accuracy with which switches (where two objects exchange locations) and substitutions (where one or two objects are replaced) are detected. Inferior performance for one-object substitutions versus two-objects switches, along with superior performance for two-object substitutions versus two-object switches was found. Our results are interpreted in terms of object file theory, trade-offs between diffused and localized attention, and net visual change.

How does aging affect the types of error made in a visual short-term memory 'object-recall' task?

This study examines how normal aging affects the occurrence of different types of incorrect responses in a visual short-term memory (VSTM) object-recall task. Seventeen young (Mean = 23.3 years, SD = 3.76), and 17 normally aging older (Mean = 66.5 years, SD = 6.30) adults participated. Memory stimuli comprised two or four real world objects (the memory load) presented sequentially, each for 650 ms, at random locations on a computer screen. After a 1000 ms retention interval, a test display was presented, comprising an empty box at one of the previously presented two or four memory stimulus locations. Participants were asked to report the name of the object presented at the cued location. Errors rates wherein participants reported the names of objects that had been presented in the memory display but not at the cued location (non-target errors) vs. objects that had not been presented at all in the memory display (non-memory errors) were compared. Significant effects of aging, memory load and target recency on error type and absolute error rates were found. Non-target error rate was higher than non-memory error rate in both age groups, indicating that VSTM may have been more often than not populated with partial traces of previously presented items. At high memory load, non-memory error rate was higher in young participants (compared to older participants) when the memory target had been presented at the earliest temporal position. However, non-target error rates exhibited a reversed trend, i.e., greater error rates were found in older participants when the memory target had been presented at the two most recent temporal positions. Data are interpreted in terms of proactive interference (earlier examined non-target items interfering with more recent items), false memories (non-memory items which have a categorical relationship to presented items, interfering with memory targets), slot and flexible resource models, and spatial coding deficits.

Manual tapping enhances visual short-term memory performance where visual and motor coordinates correspond.

Visuo-manual interaction in visual short-term memory (VSTM) has been investigated little, despite its importance in everyday tasks requiring the coordination of visual perception and manual action. This study examines the influence of a manual action performed during stimulus learning on a subsequent VSTM test for object appearance. The memory display comprised a sequence of briefly presented 1/f noise discs (i.e., possessing spectral properties akin to natural images), wherein each new stimulus was presented at a unique screen location. Participants either did (or did not) perform a concurrent manual action (spatial tapping) task requiring that a hand-held stylus be moved to a position on a touch tablet that corresponded (or did not correspond) to the screen position of each new stimulus as it appeared. At test, a single stimulus was presented, either at one of the original screen positions, or at a new position. Two factors were examined: the execution (or otherwise) of spatial tapping at a corresponding or non-corresponding position, and the presentation of test stimuli either at their original spatial positions, or at new positions. We find that spatial tapping at corresponding positions elevates VSTM performance by more than 15%, but this occurs only when stimulus positions are matched from memory to test display. Our findings suggest that multimodal attentional focus during stimulus encoding (incorporating visual, spatial, and manual components) leads to stronger, more robust memory representations. We posit several possible explanations for this effect.

Influence of affective image content on subjective quality assessment.

Image quality assessment (IQA) enables distortions introduced into an image (e.g., through lossy compression or broadcast) to be measured and evaluated for severity. It is unclear to what degree affective image content may influence this process. In this study, participants (n=25) were found to be unable to disentangle affective image content from objective image quality in a standard IQA procedure (single stimulus numerical categorical scale). We propose that this issue is worthy of consideration, particularly in single stimulus IQA techniques, in which a small number of handpicked images, not necessarily representative of the gamut of affect seen in true broadcasting, and unrated for affective content, serve as stimuli.

Object-position binding in visual short-term memory for sequentially presented unfamiliar stimuli.

The effect of spatial position on visual short-term memory (VSTM) for sequentially presented objects has been investigated relatively little, despite the fact that vision in natural environments is characterised by frequent changes in object position and gaze location. We investigated the effect of reusing previously examined spatial positions on VSTM for object appearance. Observers performed a yes-no recognition task following a memory display comprising briefly presented 1/f noise discs (ie possessing spectral properties akin to natural images) shown sequentially at random coordinates. At test, single stimuli were presented either at original spatial positions, new positions, or at a fixed central position. Results, interpreted in terms of appearance and position preview effects, indicate that, where original spatial positions were reused at test, memory performance was elevated by more than 25%, despite that spatial position was task-irrelevant (in the sense that it could not be used to facilitate a correct response per se). This study generalises object-spatial-position binding theory to a sequential display scenario in which the influences of extrafoveal processing, spatial context cues, and long-term memory support were minimised, thereby eliminating the hypothesis that object priming is the principal cause of the 'same-position advantage' in VSTM.

A combinatorial study of pose effects in unfamiliar face recognition.

The face inversion effect, evidence that humans possess a specialized system for face processing, and the (3/4) view advantage, evidence that a canonical viewpoint exists from which faces may be optimally recognized, are two commonly cited findings in the face processing literature. In this paper, the interaction of these effects is examined in a sequential matching paradigm in which unfamiliar faces are combinatorially randomized in pose across two dimensions (roll and yaw). Using large numbers of poses, trials and face stimuli, two experiments were conducted in which pose was either jointly or independently randomized between intervals. Results include that performance was modulated in a continuous fashion as each dimension was manipulated, that an offset-specific (3/4) advantage exists, that both specific study and test pose affect recognition, and that, for like offset, yaw rotation is more deleterious to performance than roll rotation. Response bias effects included that matched or reflective yaw led observers to employ a more liberal criterion.

Visual memory for fixated regions of natural images dissociates attraction and recognition.

Recognition memory for fixated regions from briefly viewed full-screen natural images is examined. Low-level image statistics reveal that observers fixated, on average (pooled across images and observers), image regions that possessed greater visual saliency than non-fixated regions, a finding that is robust across multiple fixation indices. Recognition-memory performance indicates that, of the fixation loci tested, observers were adept at recognising those with a particular profile of image statistics; visual saliency was found to be attenuated for unrecognised loci, despite that all regions were freely fixated. Furthermore, although elevated luminance was the local image statistic found to discriminate least between human and random image locations, it was the greatest predictor of recognition-memory performance, demonstrating a dissociation between image features that draw fixations and those that support visual memory. An analysis of corresponding eye movements indicates that image regions fixated via short-distance saccades enjoyed better recognition-memory performance, alluding to a focal rather than ambient mode of processing. Recognised image regions were more likely to have originated from areas evaluated (a posteriori) to have higher fixation density, a numerical metric of local interest. Surprisingly, memory for image regions fixated later in the viewing period exhibited no recency advantage, despite (typically) also being longer in duration, a finding for which a number of explanations are posited.

DOVES: a database of visual eye movements.

DOVES, a database of visual eye movements, is a set of eye movements collected from 29 human observers as they viewed 101 natural calibrated images. Recorded using a high-precision dual-Purkinje eye tracker, the database consists of around 30 000 fixation points, and is believed to be the first large-scale database of eye movements to be made available to the vision research community. The database, along with MATLAB functions for its use, may be downloaded freely from http://live.ece.utexas.edu/research/doves, and used without restriction for educational and research purposes, providing that this paper is cited in any published work. This paper documents the acquisition procedure, summarises common eye movement statistics, and highlights numerous research topics for which DOVES may be used.

Orientation anisotropies in visual search revealed by noise.

The human visual system is remarkably adept at finding objects of interest in cluttered visual environments, a task termed visual search. Because the human eye is highly foveated, it accomplishes this by making many discrete fixations linked by rapid eye movements called saccades. In such naturalistic tasks, we know very little about how the brain selects saccadic targets (the fixation loci). In this paper, we use a novel technique akin to psychophysical reverse correlation and stimuli that emulate the natural visual environment to measure observers' ability to locate a low-contrast target of unknown orientation. We present three main discoveries. First, we provide strong evidence for saccadic selectivity for spatial frequencies close to the target's central frequency. Second, we demonstrate that observers have distinct, idiosyncratic biases to certain orientations in saccadic programming, although there were no priors imposed on the target's orientation. These orientation biases cover a subset of the near-cardinal (horizontal/vertical) and near-oblique orientations, with orientations near vertical being the most common across observers. Further, these idiosyncratic biases were stable across time. Third, within observers, very similar biases exist for foveal target detection accuracy. These results suggest that saccadic targeting is tuned for known stimulus dimensions (here, spatial frequency) and also has some preference or default tuning for uncertain stimulus dimensions (here, orientation).