Comparing temporal order judgments and choice reaction time tasks as indices of exogenous spatial cuing

Modulation of perceived contrast in the brightness comparison of asynchronous stimuli

Comparative judgment is a crucial task in ecological settings, as well as in many experimental studies about basic aspects of perceptual processes. It has long been known that sequential comparison is prone to order effects. This phenomenon has received little attention and has often been discounted as a type of response bias. In the present study, we investigated brightness discrimination of two brief (100 ms) spatially disjoint luminance stimuli. In the first and second experiments, stimuli were presented against a dark background with a stimulus onset asynchrony (SOA) from 0 to 200 ms, in a paradigm controlling for response bias. In the third experiment, stimuli were presented against a bright background. We demonstrate that the time interval between stimuli modulates and even inverts their perceived brightness difference, enhancing the second stimulus relative to the first. When the background is brighter than the target stimuli, the sign of the effect is inverted, suggesting that the underlying mechanism operates on contrast rather than brightness. The magnitude of this effect is shown to depend on SOA and average luminance level of the target stimuli. Hypotheses in terms of neural and attentional dynamics are proposed.

Effect of limb movements on orienting of attention in right-hemisphere stroke

A deficit disengaging attention from the ipsilesional space in order to re-orient toward the contralesional space has been reported after right-hemisphere stroke (disengage deficit) and has been related to the severity of visuospatial neglect. Neglect rehabilitation studies have shown that left limb movements improve leftward orienting; the effect, however, is variable, and the mechanism of improvement is uncertain. Thus, this study examined whether limb movements specifically reduce the underlying disengage deficit of attention after right-hemisphere stroke. The effects of active and passive limb movements (vs. no limb movement) on orienting were examined using a covert exogenously cued orienting task in groups of right-hemisphere stroke patients with and without a significant disengage deficit (DD+, DD-) and healthy older adults. As previously seen, disengage deficit scores of stroke patients were positively correlated with the severity of neglect. The leftward disengage deficit was not affected by either active or passive limb movements, however, although movements did have both alerting and distracting effects on other aspects of orienting. Thus, our results suggest that the benefits of limb movements may not be related to changes in the underlying disengage deficit, but may impact other processes that underlie left-sided orienting (e.g., arousal and voluntary strategies).

Evidence for multisensory integration in the elicitation of prior entry by bimodal cues

This study reports an experiment investigating the relative effects of intramodal, crossmodal and bimodal cues on visual and auditory temporal order judgements. Pairs of visual or auditory targets, separated by varying stimulus onset asynchronies, were presented to either side of a central fixation (±45°), and participants were asked to identify the target that had occurred first. In some of the trials, one of the targets was preceded by a short, non-predictive visual, auditory or audiovisual cue stimulus. The cue and target stimuli were presented at the exact same locations in space. The point of subjective simultaneity revealed a consistent spatiotemporal bias towards targets at the cued location. For the visual targets, the intramodal cue elicited the largest, and the crossmodal cue the smallest, bias. The bias elicited by the bimodal cue fell between the intramodal and crossmodal cue biases, with significant differences between all cue types. The pattern for the auditory targets was similar apart from a scaling factor and greater variance, so the differences between the cue conditions did not reach significance. These results provide evidence for multisensory integration in exogenous attentional cueing. The magnitude of the bimodal cueing effect was equivalent to the average of the facilitation elicited by the intramodal and crossmodal cues. Under the assumption that the visual and auditory cues were equally informative, this is consistent with the notion that exogenous attention, like perception, integrates multimodal information in an optimal way.

Reproducibility of tactile assessments for children with unilateral cerebral palsy

A systematic review identified tactile assessments used in children with cerebral palsy (CP), but their reproducibility is unknown. Sixteen children with unilateral CP and 31 typically developing children (TDC) were assessed 2-4 weeks apart. Test-retest percent agreements within one point for children with unilateral CP (and TDC) were Semmes-Weinstein monofilaments: 75% (90%); single-point localization: 69% (97%); static two-point discrimination: 93% (97%); and moving two-point discrimination: 87% (97%). Test-retest reliability for registration and unilateral spatial tactile perception tests was high in children with CP (intraclass correlation coefficient [ICC] = 0.79-0.96). Two tests demonstrated a learning effect for children with CP, double simultaneous and tactile texture perception. Stereognosis had a ceiling effect for TDC (ICC = 0) and variability for children with CP (% exact agreement = 47%-50%). The Semmes-Weinstein monofilaments, single-point localization, and both static and moving two-point discrimination are recommended for use in practice and research. Although recommended to provide a comprehensive assessment, the measures of double simultaneous, stereognosis, and tactile texture perception may not be responsive to change over time in children with unilateral CP.

Tactile assessment in children with cerebral palsy: a clinimetric review

This review evaluates the clinimetric properties of tactile assessments for children with cerebral palsy. Assessment of registration was reported using Semmes Weinstein Monofilaments (SWMs) or exteroception. Assessment of two-point discrimination was reported using the Disk-Criminator® or paperclip methods; Single point localization and double simultaneous were reported from the Neurosensory Motor Developmental Assessment (NSMDA); graphaesthesia was reported from the Sensory Integration and Praxis Test (SIPT); and stereognosis was assessed using Manual Form Perception from the SIPT and the Klingels method (Klingels, K. et al. (2010). Upper limb motor and sensory impairments in children with hemiplegic cerebral palsy. Can they be measured reliably? Disability and Rehabilitation, 32(5), 409-416) and the Cooper method (Cooper, J., Majnemer, A., Rosenblatt, B., & Birnbaum, R. (1995). The determination of sensory deficits in children with hemiplegic cerebral palsy. Journal of Child Neurology, 10, 300-309). The SIPT and NSMDA demonstrated stronger content validity. Inter-rater reliability was excellent for SIPT (ICC = 0.99) and exteroception (k = 0.88). Test-retest reliability was excellent for exteroception (k = 0.89) and stereognosis (ICC = 0.86; 100%), moderate for SIPT (r = 0.69-0.74) and poor for SWM (k = 0.22). Together these assessments measure tactile registration and spatial perception. Temporal and textural tests are to be developed for comprehensive tactile examination.

How well can people judge when something happened?

One way to estimate the temporal precision of vision is with judgments of synchrony or temporal order of visual events. We show that irrelevant motion disrupts the high temporal precision that can be found in such tasks when the two events occur close together, suggesting that the high precision is based on detecting illusory motion rather than on detecting time differences. We also show that temporal precision is not necessarily better when one can accurately anticipate the moments of the events. Finally, we illustrate that a limited resolution of determining the duration of an event imposes a fundamental problem in determining when the event happened. Our experimental estimates of how well people can explicitly judge when something happened are far too poor to account for human performance in various tasks that require temporal precision, such as interception, judging motion or aligning moving targets spatially.