Calibration of a color monitor for visual psychophysics

It has become common for stimuli used in visual psychophysical experiments to be presented on high-resolution color cathode-ray tubes (CRTs) such as the Barco CDCT 6551. These enable a flexibility of color, spatial-frequency content, temporal-frequency content, duration, size, and position that is not provided by most other media. CRTs are, however, not perfect; they suffer from the effects of temporal instability, spatial variability, lack of phosphor constancy, gun interdependence, and gun nonlinearity. This paper describes methods of assessing these aspects of monitor performance with respect to how significant each may be in psychometric terms. Although every application of CRT use in visual psychophysics is different, some general rules can be formulated to help ensure that unwanted effects are kept to a minimum. For the CRT used in this study (Barco CDCT 6551), a warm-up time of 30-45 min is necessary before chromatic and luminous stability ensues. Restriction of individual gun outputs to within 10%-90% of the possible range ensures that the effects of gun interdependence and lack of phosphor constancy are negligible. Calibration methods dealing with the linearization of gun output are also discussed.     

The role of vision in the temporal and spatial control of handwriting.

The general observation that handwriting is not noticeably impaired by the withdrawal of vision can be explained in two ways. One might argue that vision is not needed during the act of writing. Micro-analyses should then reveal that spatial as well as temporal writing features are identical in conditions of vision and no vision. Alternatively, it is possible that vision is needed during the act of writing, but that without vision possible errors and inaccuracies have to be prevented. Assuming that the latter would place an extra demand on movement control, this should be revealed by an increase in processing time. We have found evidence for the latter view in the present study in which 12 subjects wrote a nonsense letter sequence with and without vision. Close examination showed that writing shapes remained equally invariant under both vision conditions, suggesting that spatial control was unaffected by withdrawing vision. The prediction that invariance of shapes is preserved in the absence of vision at the expense of processing time increments was confirmed. The increase of reaction time observed when visual guidance was withdrawn suggests that more processing time was needed prior to the movement start. Moreover, the RT increment was larger when a short writing duration was instructed. The present findings will be discussed in light of the remarkable flexibility of writing as a motor skill in which writers appear to be able to employ specific strategies to preserve shape in the absence of visual guidance.     

Organization of visuo-spatial serial memory: interaction of temporal order with spatial and temporal grouping

This study investigates whether memory for sequences of spatial locations can be represented hierarchically, that is, as successive groups containing the order of constituent locations. Two grouping manipulations are used: Temporal grouping, based on the verbal serial memory literature, and spatial grouping, based on recent empirical work on visuo-spatial serial memory. In Experiment 1, we examine the relationship between spatial grouping and temporal order and showed that recall performance increases when both temporal and spatial organization correlate, but decreases when they clash. Experiments 2 and 3 show that the latter result is confounded by differences in path length (length of spatial path defined by the locations) between conditions, and that no effect of the spatial organization is observed when path length is controlled for. In Experiment 4, an alternative method to spatial grouping, temporal grouping, is used to induce hierarchical organization. A recall advantage is found in the temporal grouping condition. The results suggest that hierarchical representations can be imposed on order information for visuo-spatial sequences, either when participants have pre-existing knowledge about the form of the path formed by the sequence or when temporal boundaries delimit chunks; that increased path length is the cause of the performance decrement observed when dots from separate spatial groups are presented successively; and that path length and more generally sequence characteristics should be taken into account in designing future research on visuo-spatial serial memory.     

Attentional resolution

Attention can enhance selectively the visual information processing of particular locations or objects. Recent studies have shown that this enhancement has limited spatial resolution, the smallest regions that can be isolated by attention are much coarser than the smallest details that can be resolved by vision. Multiple similar objects spaced more finely than the limit of attentional resolution cannot be individuated for further processing and can only be perceived as a grouped texture. As a result, at any given time, only part of the spatial and temporal information registered by the early sensory systems is available to conscious perception. It is likely that attentional resolution is limited at a stage beyond V1 and that it has a finer grain in the lower visual field than in the upper field. The spatial aperture of attention is elongated along the radial axis relative to fixation. The briefest temporal window of attention is also much broader than visual temporal resolution. Many perceptual phenomena related to rapid serial visual presentation may reflect the limited temporal resolution of attention.     

Visual space-time interactions: effects of adapting to spatial frequencies on temporal sensitivity

To study how adaptation to spatial frequency patterns affects temporal sensitivity in vision, observers were selectively adapted for 4 min to either a high- or a low-spatial-frequency sinusoidal grating (12 and 2 cpd, respectively). Their sensitivities to modulation of a blurred patch at high or low temporal frequencies (12 Hz and 2 Hz, respectively) were measured, before and after the adaptation period, by using the yes/no task of signal detection theory. The data consistently indicated that spatial adaptation differentially affected the observers' sensitivities to temporal signals. Specifically, when the observers were adapted to low spatial frequencies, their sensitivity to low temporal frequencies was reduced; when they were adapted to high spatial frequencies, their sensitivity to high temporal frequencies was increased. These results have implications for the psychophysical measurements of temporal and spatial sensitivity, as well as for the issue of the separability of spatial and temporal properties of individual channels.     

时序信息和空间信息在工作记忆中的分离存储

采用相对新近性判断范式（judgments of relative recency）,通过三个实验探讨了工作记忆中时序信息和空间信息的存储方式及其关系。实验一比较了有无空间线索两种条件下时序信息的记忆绩效,结果发现,有无空间线索并不影响对时序信．E-的记忆。实验二和实验三通过控制刺激呈现的视野范围和减少呈现位置的不确定性来利化空间线索,结果表明,时序信息的记忆绩效也不受空间线索的影响。由此推论,工作记忆中的时序信息和空间信息是分离编码存储的,加入空间线索并不能提高时序信息的记忆绩效。     

空间图式加工促进方向性时间表述的理解

时间表征是否具有空间方向性？本研究通过考察66名研究生时间表述实时加工中的空间引导效应来回答这个问题。实验一表明：空间垂直方向性图式促进被试加工含有空间词汇的时间表述;实验二表明：两种空间方向性图式,即水平方向性图式和垂直方向性图式,都促进被试加工含有纯时问词汇的时间表述。实验结果证实了时间表征具有空间方向性,并为“抽象思维以感知一动觉经验为基础”这一论点提供心理学证据。     

Unconscious vision and executive control: How unconscious processing and conscious action control interact

Research on unconscious or unaware vision has demonstrated that unconscious processing can be flexibly adapted to the current goals of human agents. The present review focuses on one area of research, masked visual priming. This method uses visual stimuli presented in a temporal sequence to lower the visibility of one of these stimuli. In this way, a stimulus can be masked and even rendered invisible. Despite its invisibility, a masked stimulus if used as a prime can influence a variety of executive functions, such as response activation, semantic processing, or attention shifting. There are also limitations on the processing of masked primes. While masked priming research demonstrates the top-down dependent usage of unconscious vision during task-set execution it also highlights that the set-up of a new task-set depends on conscious vision as its input. This basic distinction captures a major qualitative difference between conscious and unconscious vision.     

Keeping it short: a comparison of methods for brief picture presentation

Abstract— Research has shown that backward masking is a powerful tool for studying unconscious mental processes. Whereas studies have traditionally presented stimuli using cathode-ray tube (CRT) monitors or mechanical shutters together with slide projectors, recent studies (mainly in functional magnetic resonance imaging, fMRI) have begun to use methods based on liquid crystal displays (LCDs) and thin-film transistor (TFT) technology. However, because of differences in technology, all methods may not be equally suited for masking. When methods were compared for their accuracy in presenting pictures at short durations, LCD and TFT presentations had poor accuracy, but shutter and CRT presentations had better accuracy. Because CRTs interfere with the imaging process in fMRI, we recommend the use of mechanical shutters. However, our results may not generally apply to all displays, so we advise researchers to validate the presentation parameters of their displays. The procedure described here may be useful for that purpose.     

Monocular and binocular vision in the control of goal-directed movement

In the present research the authors examined the time course of binocular integration in goal-directed aiming and grasping. With liquid-crystal goggles, the authors manipulated vision independently to the right and left eyes of 10 students during movement preparation and movement execution. Contrary to earlier findings reported in catching experiments (I. Olivier, D. J. Weeks, K. L. Ricker, J. Lyons, & D. Elliott, 1998), neither a temporal nor a spatial binocular advantage was obtained in 1 grasping and 2 aiming studies. That result suggests that, at least in some circumstances, monocular vision is sufficient for the precise control of limb movements. In a final aiming experiment involving 3-dimensional spatial variability and no trial-to-trial visual feedback about performance, binocular vision was associated with greater spatial accuracy. Binocular superiority appeared to be most pronounced when participants were unable to adjust their limb control strategy or procedure on the basis of terminal feedback about performance.     

Spatial and temporal limits in cognitive neuroimaging with fMRI

A large body of research in human perception and cognition has been concerned with the segregation of mental events into their presumed hierarchical processing stages, the temporal aspect of such processing being termed ‘mental chronometry’. Advances in single-event functional magnetic resonance imaging (fMRI) have allowed the extraction of relative timing information between the onset of activity in different neural substrates as well as the duration of cognitive processing during a task, offering new opportunities in the study of human perception and cognition. Single-event fMRI studies have also facilitated increased spatial resolution in fMRI, allowing studies of columnar organization in humans. Important processes such as object recognition, binocular vision and other processes are thought to be organized at the columnar level; thus, these advances in the spatial and temporal capabilities of fMRI allow a new generation of cognitive and basic neuroscience studies to be performed, investigating the temporal and spatial relationships between these cortical sub-units. Such experiments bear a closer resemblance to single-unit or evoked-potential studies than to classical static brain activation maps and might serve as a bridge between primate electrophysiology and human studies. These advances are initially demonstrated only in simple visual and motor system tasks and it is likely to be several years before the techniques we describe are robust enough for general use.     

Cluster randomized trials with treatment noncompliance

Cluster randomized trials (CRTs) have been widely used in field experiments treating a cluster of individuals as the unit of randomization. This study focused particularly on situations where CRTs are accompanied by a common complication, namely, treatment noncompliance or, more generally, intervention nonadherence. In CRTs, compliance may be related not only to individual characteristics but also to the environment of clusters individuals belong to. Therefore, analyses ignoring the connection between compliance and clustering may not provide valid results. Although randomized field experiments often suffer from both noncompliance and clustering of the data, these features have been studied as separate rather than concurrent problems. On the basis of Monte Carlo simulations, this study demonstrated how clustering and noncompliance may affect statistical inferences and how these two complications can be accounted for simultaneously. In particular, the effect of the intervention on individuals who not only were assigned to active intervention but also abided by this intervention assignment (complier average causal effect) was the focus. For estimation of intervention effects considering noncompliance and data clustering, an ML-EM estimation method was employed.     

Monocular and Binocular Vision in the Control of Goal-Directed Movement

In the present research the authors examined the time course of binocular integration in goal-directed aiming and grasping. With liquid-crystal goggles, the authors manipulated vision independently to the right and left eyes of 10 students during movement preparation and movement execution. Contrary to earlier findings reported in catching experiments (I. Olivier, D. J. Weeks, K. L. Ricker, J. Lyons, & D. Elliott, 1998), neither a temporal nor a spatial binocular advantage was obtained in 1 grasping and 2 aiming studies. That result suggests that, at least in some circumstances, monocular vision is sufficient for the precise control of limb movements. In a final aiming experiment involving 3-dimen- sional spatial variability and no trial-to-trial visual feedback about performance, binocular vision was associated with greater spatial accuracy. Binocular superiority appeared to be most pronounced when participants were unable to adjust their limb control strategy or procedure on the basis of terminal feedback about performance.     

Emotion-induced trade-offs in spatiotemporal vision

It is generally assumed that emotion facilitates human vision in order to promote adaptive responses to a potential threat in the environment. Surprisingly, we recently found that emotion in some cases impairs the perception of elementary visual features (Bocanegra & Zeelenberg, 2009b). Here, we demonstrate that emotion improves fast temporal vision at the expense of fine-grained spatial vision. We tested participants' threshold resolution with Landolt circles containing a small spatial or brief temporal discontinuity. The prior presentation of a fearful face cue, compared with a neutral face cue, impaired spatial resolution but improved temporal resolution. In addition, we show that these benefits and deficits were triggered selectively by the global configural properties of the faces, which were transmitted only through low spatial frequencies. Critically, the common locus of these opposite effects suggests a trade-off between magno- and parvocellular-type visual channels, which contradicts the common assumption that emotion invariably improves vision. We show that, rather than being a general "boost" for all visual features, affective neural circuits sacrifice the slower processing of small details for a coarser but faster visual signal.     

Efficacy of Cognitive Rehabilitation Therapies for Mild Cognitive Impairment (MCI) in Older Adults: Working Toward a Theoretical Model and Evidence-Based Interventions

To evaluate the efficacy of cognitive rehabilitation therapies (CRTs) for mild cognitive impairment (MCI). Our review revealed a need for evidence-based treatments for MCI and a lack of a theoretical rehabilitation model to guide the development and evaluation of these interventions. We have thus proposed a theoretical rehabilitation model of MCI that yields key intervention targets–cognitive compromise, functional compromise, neuropsychiatric symptoms, and modifiable risk and protective factors known to be associated with MCI and dementia. Our model additionally defines specific cognitive rehabilitation approaches that may directly or indirectly target key outcomes–restorative cognitive training, compensatory cognitive training, lifestyle interventions, and psychotherapeutic techniques. Fourteen randomized controlled trials met inclusion criteria and were reviewed. Studies markedly varied in terms of intervention approaches and selected outcome measures and were frequently hampered by design limitations. The bulk of the evidence suggested that CRTs can change targeted behaviors in individuals with MCI and that CRTs are associated with improvements in objective cognitive performance, but the pattern of effects on specific cognitive domains was inconsistent across studies. Other important outcomes (i.e., daily functioning, quality of life, neuropsychiatric symptom severity) were infrequently assessed across studies. Few studies evaluated long-term outcomes or the impact of CRTs on conversion rates from MCI to dementia or normal cognition. Overall, results from trials are promising but inconclusive. Additional well-designed and adequately powered trials are warranted and required before CRTs for MCI can be considered evidence-based.     

Uncertainty impairs grating detection performance in the cat

Using behavioral techniques, contrast thresholds for detection of grating patterns by the cat were measured under conditions of certainty and uncertainty. For certainty trials, the same combination of spatial and temporal frequencies was presented throughout a test session, whereas with uncertainty, the cat was unable to anticipate which of two spatial (or temporal) frequencies would be presented on a given trial. For most spatiotemporal combinations, uncertainty served to elevate contrast thresholds by almost .3 log units, a finding that parallels the outcome found in human vision. The uncertainty paradigm may provide a useful inferential tool for determining channel bandwidth in cat vision.     

Discrepancy and nondiscrepancy methods of assessing visual-auditory interaction

Much of our information about interaction among the sensory modalities has come from studies in which discrepancy between the modalities has been imposed experimentally. The question arises whether the conclusions generated from discrepancy research are affected by the use of the nonnatural experimental situation: Would the same conclusions be reached if discrepancy were not used? In addition to using the index of interaction derived from discrepancy, as in prior research, the present study assessed two nonexperimentally imposed indices to explore the interaction between vision and audition in a spatial localization task. The additional indices, or “tags,” were standard deviations (SDs) and confidence ratings (CRs) of localization responses. The SD tag showed a pattern of interaction between vision and audition that was identical to that found with spatial discrepancy. The CR tag produced a similar pattern but did not show the same regular variation with the independent variable. Both SD and CR tags showed identical patterns of results when an experimentally imposed discrepancy was and was not used, suggesting that the use of moderate degrees of experimental discrepancy does not produce misleading conclusions about intersensory interaction.     

Intersensory binding across space and time: A tutorial review

Spatial ventriloquism refers to the phenomenon that a visual stimulus such as a flash can attract the perceived location of a spatially discordant but temporally synchronous sound. An analogous example of mutual attraction between audition and vision has been found in the temporal domain, where temporal aspects of a visual event, such as its onset, frequency, or duration, can be biased by a slightly asynchronous sound. In this review, we examine various manifestations of spatial and temporal attraction between the senses (both direct effects and aftereffects), and we discuss important constraints on the occurrence of these effects. Factors that potentially modulate ventriloquism—such as attention, synesthetic correspondence, and other cognitive factors—are described. We trace theories and models of spatial and temporal ventriloquism, from the traditional unity assumption and modality appropriateness hypothesis to more recent Bayesian and neural network approaches. Finally, we summarize recent evidence probing the underlying neural mechanisms of spatial and temporal ventriloquism.     

Active (not passive) spatial imagery primes temporal judgements

Previous research has shown that primes that induce particular spatial perspectives can influence temporal judgements. However, most studies have used priming stimuli that involve both spatial and motor language and imagery. Here we ask whether the motor content of these stimuli plays an important role in their ability to serve as effective primes. A total of 198 adult participants made temporal judgements after exposure to spatial primes involving varying levels of imagined effort. Spatial primes involving imagined motor actions, but not those involving equivalent passive motions through space, successfully primed decisions about time. This suggests that motor content, rather than spatial content alone, contributes to the priming effects that arise when people make temporal judgements after exposure to particular spatial perspectives.     

The role of transcranial magnetic stimulation (TMS) in studies of vision, attention and cognition

Transcranial magnetic stimulation (TMS) can be conceptualized as a virtual lesion technique, capable of disrupting organized cortical activity, transiently and reversibly. The technique combines good spatial and temporal resolution and, moreover, because it represents an interference technique, can be said to have excellent functional resolution. The following is a review and discussion of the contribution which TMS has made to the study of vision, attention, development and plasticity and speech and language.