Interstimulus Interval Duration Research Articles

Gradual decay and sudden death of short-term memory for pitch.

The ability to discriminate frequency differences between pure tones declines as the duration of the interstimulus interval (ISI) increases. The conventional explanation for this finding is that pitch representations gradually decay from auditory short-term memory. Gradual decay means that internal noise increases with increasing ISI duration. Another possibility is that pitch representations experience "sudden death," disappearing without a trace from memory. Sudden death means that listeners guess (respond at random) more often when the ISIs are longer. Since internal noise and guessing probabilities influence the shape of psychometric functions in different ways, they can be estimated simultaneously. Eleven amateur musicians performed a two-interval, two-alternative forced-choice frequency-discrimination task. The frequencies of the first tones were roved, and frequency differences and ISI durations were manipulated across trials. Data were analyzed using Bayesian models that simultaneously estimated internal noise and guessing probabilities. On average across listeners, internal noise increased monotonically as a function of increasing ISI duration, suggesting that gradual decay occurred. The guessing rate decreased with an increasing ISI duration between 0.5 and 2 s but then increased with further increases in ISI duration, suggesting that sudden death occurred but perhaps only at longer ISIs. Results are problematic for decay-only models of discrimination and contrast with those from a study on visual short-term memory, which found that over similar durations, visual representations experienced little gradual decay yet substantial sudden death.

Effects of silent interstimulus interval duration between precursor and target stimuli on spectral context effects in vowel and consonant categorization

Effects of silent interstimulus interval duration between precursor and target stimuli on spectral context effects in vowel and consonant categorization

No Effect of Interstimulus Interval on Acoustic Reflex Thresholds.

The acoustic reflex (AR), a longstanding component of the audiological test battery, has received renewed attention in the context of noise-induced cochlear synaptopathy—the destruction of synapses between inner hair cells and auditory nerve fibers. Noninvasive proxy measures of synaptopathy are widely sought, and AR thresholds (ARTs) correlate closely with synaptic survival in rodents. However, measurement in humans at high stimulus frequencies—likely important when testing for noise-induced pathology—can be challenging; reflexes at 4 kHz are frequently absent or occur only at high stimulus levels, even in young people with clinically normal audiograms. This phenomenon may partly reflect differences across stimulus frequency in the temporal characteristics of the response; later onset of the response, earlier onset of adaptation, and higher rate of adaptation have been observed at 4 kHz than at 1 kHz. One temporal aspect of the response that has received little attention is the interstimulus interval (ISI); inadequate duration of ISI might lead to incomplete recovery of the response between successive presentations and consequent response fatigue. This research aimed to test for effects of ISI on ARTs in normally hearing young humans, measured at 1 and 4 kHz. Contrary to our hypotheses, increasing ISIs from 2.5 to 8.5 s did not reduce ART level, nor raise ART reliability. Results confirm that clinically measured ARTs—including those at 4 kHz—can exhibit excellent reliability and that relatively short (2.5 s) ISIs are adequate for the measurement of sensitive and reliable ARTs.

Temporal expectations modulate face image repetition suppression of early stimulus evoked event-related potentials

Repeated exposure to a stimulus leads to reduced responses of stimulus-selective sensory neurons, an effect known as repetition suppression or stimulus-specific adaptation. Several influential models have been proposed to explain repetition suppression within hierarchically-organised sensory systems, with each specifying different mechanisms underlying repetition effects. We manipulated temporal expectations within a face repetition experiment to test a critical prediction of the predictive coding model of repetition suppression: that repetition effects will be larger following stimuli that appear at expected times compared to stimuli that appear at unexpected times. We recorded event-related potentials from 18 participants and mapped the spatiotemporal progression of repetition effects using mass univariate analyses. We then assessed whether the magnitudes of observed face image repetition effects were influenced by temporal expectations. In each trial participants saw an adapter face, followed by a 500 ms or 1000 ms interstimulus interval (ISI), and then a test face, which was the same or a different face identity to the adapter. Participants’ expectations for whether the test face would appear after a 500 ms ISI were cued by the sex of the adapter face. Our analyses revealed multiple repetition effects with distinct scalp topographies, extending until at least 800 ms from stimulus onset. An early (158–203 ms) repetition effect was larger for stimuli following surprising, rather than expected, 500 ms ISI durations, contrary to the model predictions of the predictive coding model of repetition suppression. During this time window temporal expectation effects were larger for alternating, compared to repeated, test stimuli. Statistically significant temporal expectation by stimulus repetition interactions were not found for later (230–609 ms) time windows. Our results provide further evidence that repetition suppression can reduce neural effects of expectation and surprise, indicating that there are multiple interactive mechanisms supporting sensory predictions within the visual hierarchy.

Synchronization and fractal scaling as foundations for cognitive control

This article investigates the degree to which the intrinsic propensity for entrainment in oscillatory systems serves as a plausible foundation for understanding the assembly and flexibility of cognitive systems. Three experiments tested for the strength of performance entrainment to oscillations inserted into event timing and stimulus properties of cognitive tasks. In the first temporal estimation experiment, attractor strength analyses revealed participants spontaneously entrained to sinusoidal changes in the duration of inter-trial intervals. A second simple reaction time task introduced oscillatory changes to the inter-stimulus interval durations across trials, and attractor strength analyses revealed weaker but reliable entrainment to the input signals. A third dyadic temporal estimation task revealed oscillatory entrainment that was distributed across pairs of participants. The experimental results were evaluated in terms of coupled oscillator dynamics and short-term perceptual lags. The entrainment hypothesis was most successful in explaining the empirical patterns, suggesting that cognitive performance relies on coordinative activity. Together, the three studies demonstrated coordinative activity over a range of temporal scales and distributed across individuals comprising the dyads. The simple reaction time study illustrated within-trial coordinative dynamics; individual temporal estimation illustrated across-trial coordination, and dyadic temporal estimation illustrated person-to-person coordinative dynamics. The findings underscore the role environmental constraints impose on cognitive activity and demonstrate how seemingly disparate features of distinct cognitive tasks can be assimilated in terms of synchronization principles.

Dissociable effects of inter-stimulus interval and presentation duration on rapid face categorization

Fast periodic visual stimulation combined with electroencephalography (FPVS-EEG) has unique sensitivity and objectivity in measuring rapid visual categorization processes. It constrains image processing time by presenting stimuli rapidly through brief stimulus presentation durations and short inter-stimulus intervals. However, the selective impact of these temporal parameters on visual categorization is largely unknown. Here, we presented natural images of objects at a rate of 10 or 20 per second (10 or 20 Hz), with faces appearing once per second (1 Hz), leading to two distinct frequency-tagged EEG responses. Twelve observers were tested with three squarewave image presentation conditions: 1) with an ISI, a traditional 50% duty cycle at 10 Hz (50-ms stimulus duration separated by a 50-ms ISI); 2) removing the ISI and matching the rate, a 100% duty cycle at 10 Hz (100-ms duration with 0-ms ISI); 3) removing the ISI and matching the stimulus presentation duration, a 100% duty cycle at 20 Hz (50-ms duration with 0-ms ISI). The face categorization response was significantly decreased in the 20 Hz 100% condition. The conditions at 10 Hz showed similar face-categorization responses, peaking maximally over the right occipito-temporal (ROT) cortex. However, the onset of the 10 Hz 100% response was delayed by about 20 ms over the ROT region relative to the 10 Hz 50% condition, likely due to immediate forward-masking by preceding images. Taken together, these results help to interpret how the FPVS-EEG paradigm sets temporal constraints on visual image categorization.

Computational study of depth completion consistent with human bi-stable perception for ambiguous figures

We propose a computational model that is consistent with human perception of depth in “ambiguous regions,” in which no binocular disparity exists. Results obtained from our model reveal a new characteristic of depth perception. Random dot stereograms (RDS) are often used as examples because RDS provides sufficient disparity for depth calculation. A simple question confronts us: “How can we estimate the depth of a no-texture image region, such as one on white paper?” In such ambiguous regions, mathematical solutions related to binocular disparities are not unique or indefinite. We examine a mathematical description of depth completion that is consistent with human perception of depth for ambiguous regions. Using computer simulation, we demonstrate that resultant depth-maps qualitatively reproduce human depth perception of two kinds. The resultant depth maps produced using our model depend on the initial depth in the ambiguous region. Considering this dependence from psychological viewpoints, we conjecture that humans perceive completed surfaces that are affected by prior-stimuli corresponding to the initial condition of depth. We conducted psychological experiments to verify the model prediction. An ambiguous stimulus was presented after a prior stimulus removed ambiguity. The inter-stimulus interval (ISI) was inserted between the prior stimulus and post-stimulus. Results show that correlation of perception between the prior stimulus and post-stimulus depends on the ISI duration. Correlation is positive, negative, and nearly zero in the respective cases of short (0–200 ms), medium (200–400 ms), and long ISI (>400 ms). Furthermore, based on our model, we propose a computational model that can explain the dependence.

Intraoperative direct cortical stimulation motor evoked potentials: Stimulus parameter recommendations based on rheobase and chronaxie

ObjectiveTo determine optimal interstimulus interval (ISI) and pulse duration (D) for direct cortical stimulation (DCS) motor evoked potentials (MEPs) based on rheobase and chronaxie derived with two techniques. MethodsIn 20 patients under propofol/remifentanil anesthesia, 5-pulse DCS thenar MEP rheobase and chronaxie with 2, 3, 4 and 5ms ISI were measured by linear regression of five charge thresholds at 0.05, 0.1, 0.2, 0.5 and 1msD, and estimated from two charge thresholds at 0.1 and 1msD using simple arithmetic. Optimal parameters were defined by minimum threshold energy: the ISI with lowest rheobase2×chronaxie, and D at its chronaxie. Near-optimal was defined as threshold energy <25% above minimum. ResultsThe optimal ISI was 3 or 4 (n=7 each), 2 (n=4), or 5ms (n=2), but only 4ms was always either optimal or near-optimal. The optimal D was ∼0.2 (n=12), ∼0.1 (n=7) or ∼0.3ms (n=1). Two-point estimates closely approximated five-point measurements. ConclusionsOptimal ISI/D varies, with 4ms/0.2ms being most consistently optimal or near-optimal. Two-point estimation is sufficiently accurate. SignificanceThe results endorse 4ms ISI and 0.2msD for general use. Two-point estimation could enable quick individual optimization.

Speech transformed into song heightens temporal sensitivity but weakens absolute pitch sensitivity

The speech-to-song illusion (STS) is a phenomenon in which some spoken utterances perceptually transform to song via repetition. The existence of utterances that do and do not transform makes it possible to investigate similarities and differences between the musical and linguistic modes of listening, with the former elicited by transforming utterances and the latter by non-transforming utterances. In Experiment 1, inter-stimulus interval durations within STS trials were either steady, slightly variable, or highly variable. Participants reported how temporally regular the utterance entrances were. In Experiment 2, participants were first exposed to STS trials and then asked to choose the transposition of the utterances they heard during the exposure phase. Results indicate that listeners exhibit heightened awareness of temporal manipulations to transforming utterances compared to non-transforming utterances, but not to absolute pitch manipulations. This suggests that compared to the linguistic mode of perception, the musical mode entails an increased sensitivity to temporal regularity, but not to absolute pitch. The methodology used here establishes a framework for implicitly differentiating musical from linguistic perception, as well as for behaviorally investigating the different cognitive apparatus that people use when activating the musical or linguistic mode of perception.

Neural adaptation of visual ERP components: Effects of adaptor stimulus duration and interstimulus interval

Event Abstract Back to Event Neural adaptation of visual ERP components: Effects of adaptor stimulus duration and interstimulus interval Daniel Feuerriegel1*, Owen Churches2, Mark Kohler1 and Hannah Keage1 1 University of South Australia, Cognitive Neuroscience Laboratory, Australia 2 Flinders University, Brain and Cognition Laboratory, Australia Neural adaptation paradigms inform us of how our perceptual system dynamically changes in response to our environment. Systematically testing experimental variables that affect adaptation can further develop neural models of visual processing over time. The degree of neural response to a stimulus (S2) is affected by the presentation duration of the previous/adaptor stimulus (S1) and the interstimulus interval (ISI) duration, however there appears to be no systematic examination of the effects and interaction of these factors in ERP research. We systematically varied both S1 duration and ISI and assessed effects on the P1, N170 and P2 ERP components in face and object perception. Greyscale images of faces and chairs were presented at S1 and S2 level while EEG was recorded. In each trial an S1 stimulus was presented, followed by an ISI and an S2 stimulus. S1 stimuli were presented for 200ms, 500ms or 1000ms. The ISI was set at 200ms or 500ms. Peak amplitude measures were derived from ERPs to S2 stimuli in each condition. ISI affected all ERP component amplitudes, and S1 duration affected the N170 and P2 only. P1 and P2 components were smaller in the 200ms than 500ms ISI conditions, whereas the N170 was larger after 200ms ISIs. No effects of S1 duration were observed for the P1, however N170 and P2 amplitudes were smaller for longer S1 durations, particularly after shorter (200ms) ISIs. Effects of S1 duration on the N170 were specific to repetitions of the same stimuli category. The overall results demonstrate that effects of S1 duration and ISI are not consistent across ERP components, suggesting differential modulation of low and high-level vision over time. These results do not support a singular mechanism of adaptation across visual areas, but rather a complex pattern of neural activity modulations with continued processing of a visual stimulus. Keywords: face perception, Event-related potentials, P1, N170, P2, Neural adaptation Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Sensation and Perception Citation: Feuerriegel D, Churches O, Kohler M and Keage H (2015). Neural adaptation of visual ERP components: Effects of adaptor stimulus duration and interstimulus interval. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00150 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Mr. Daniel Feuerriegel, University of South Australia, Cognitive Neuroscience Laboratory, Adelaide, Australia, Daniel.feuerriegel@unisa.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Daniel Feuerriegel Owen Churches Mark Kohler Hannah Keage Google Daniel Feuerriegel Owen Churches Mark Kohler Hannah Keage Google Scholar Daniel Feuerriegel Owen Churches Mark Kohler Hannah Keage PubMed Daniel Feuerriegel Owen Churches Mark Kohler Hannah Keage Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Effects of inter-stimulus interval (ISI) duration on the N1 and P2 components of the auditory event-related potential

The N1 and P2 components of the event-related potential are relevant markers in the processing of auditory information, indicating the presence of several acoustic phenomena, such as pure tones or speech sounds. In addition, the expression of these components seems to be sensitive to diverse experimental variations. The main purpose of the present investigation was to explore the role of inter-stimulus interval (ISI) on the N1 and P2 responses, considering two widely used experimental paradigms: a single tone task (1000Hz sound repeated in a fixed rhythm) and an auditory oddball (80% of the stimuli were equal to the sound used in the single tone and the remaining were a 1500Hz tone). Both tasks had four different conditions, and each one tested a fixed value of ISI (600, 1000, 3000, or 6000ms). A sample of 22 participants performed these tasks, while an EEG was recorded, in order to examine the maximum amplitude of the N1 and P2 components. Analysis of the stimuli in the single tone task and the frequent tones in the oddball task revealed a similar outcome for both tasks and for both components: N1 and P2 amplitudes were enhanced in conditions with longer ISIs regardless of task. This response pattern emphasizes the dependence of both the N1 and P2 components on the ISI, especially in a scenario of repetitive and regular stimulation. The absence of task effects suggests that the ISI effect reported may depend on refractory mechanisms rather than being due to habituation effects.

Spike-coding mechanisms of cerebellar temporal processing in classical conditioning and voluntary movements.

Time is a fundamental and critical factor in daily life. Millisecond timing, which is the underlying temporal processing for speaking, dancing, and other activities, is reported to rely on the cerebellum. In this review, we discuss the cerebellar spike-coding mechanisms for temporal processing. Although the contribution of the cerebellum to both classical conditioning and voluntary movements is well known, the difference of the mechanisms for temporal processing between classical conditioning and voluntary movements is not clear. Therefore, we review the evidence of cerebellar temporal processing in studies of classical conditioning and voluntary movements and report the similarities and differences between them. From some studies, which used tasks that can change some of the temporal properties (e.g., the duration of interstimulus intervals) with keeping identical movements, we concluded that classical conditioning and voluntary movements may share a common spike-coding mechanism because simple spikes in Purkinje cells decrease at predicted times for responses regardless of the intervals between responses or stimulation.

Hear it playing low and slow: How pitch level differentially influences time perception

Variations in both pitch and time are important in conveying meaning through speech and music, however, research is scant on perceptual interactions between these two domains. Using an ordinal comparison procedure, we explored how different pitch levels of flanker tones influenced the perceived duration of empty interstimulus intervals (ISIs). Participants heard monotonic, isochronous tone sequences (ISIs of 300, 600, or 1200ms) composed of either one or five standard ISIs flanked by 500Hz tones, followed by a final interval (FI) flanked by tones of either the same (500Hz), higher (625Hz), or lower (400Hz) pitch. The FI varied in duration around the standard ISI duration. Participants were asked to determine if the FI was longer or shorter in duration than the preceding intervals. We found that an increase in FI flanker tone pitch level led to the underestimation of FI durations while a decrease in FI flanker tone pitch led to the overestimation of FI durations. The magnitude of these pitch-level effects decreased as the duration of the standard interval was increased, suggesting that the effect was driven by differences in mode-switch latencies to start/stop timing. Temporal context (One vs. Five Standard ISIs) did not have a consistent effect on performance. We propose that the interaction between pitch and time may have important consequences in understanding the ways in which meaning and emotion are communicated.

Effects of physiological aging on mismatch negativity: A meta-analysis

Mismatch negativity (MMN) is a promising window on how the functional integrity of auditory sensory memory and change discrimination is modulated by age and relevant clinical conditions. However, the effects of aging on MMN have remained somewhat elusive, particularly at short interstimulus intervals (ISIs). We performed a meta-analysis of peer-reviewed MMN studies that had targeted both young and elderly adults to estimate the mean effect size. Nine studies, consisting of 29 individual investigations, were included and the final total study population consisted of 182 young and 165 elderly subjects. The effects of different deviant types and duration of ISIs on the effect size were assessed. The overall mean effect size was 0.63 (95% CI at 0.43–0.82). The effect sizes for long ISI (>2s, effect size 0.68, 95% CI at 0.31–1.06) and short ISI (<2s, effect size 0.61, 95% CI at 0.39–0.84) were both considered moderate. A further analysis showed a prominent aging-related decrease in MMN responses to duration and frequency changes at short ISIs. It was also interesting to note that the effect size was about 25% larger for duration deviant condition compared to the frequency deviant condition. In conclusion, a reduced MMN response to duration and frequency deviants is a robust feature among the aged adults, which suggests that there has been a decline in the functional integrity of central auditory processing in this population.

Auditory Temporal-Organization Abilities in School-Age Children With Peripheral Hearing Loss

The objective was to assess auditory sequential organization (ASO) ability in children with and without hearing loss. Forty children 9 to 12 years old participated in the study: 12 with sensory hearing loss (HL), 12 with central auditory processing disorder (CAPD), and 16 with normal hearing. They performed an ASO task in which they were asked to recall 2, 3, and 5 verbal and nonverbal stimuli with an interstimulus interval (ISI) of 425 ms as well as sequences of 2 elements with an ISI of 20 or 1,000 ms. No significant difference was found between the group of children with HL and the 2 other groups on nonverbal stimuli in all testing conditions. Regardless of ISI duration or number of elements in the sequence, children with HL had significantly fewer correct responses than children with normal hearing and children with CAPD for the verbal stimuli /ba/-/da/. Children with HL had significantly better performance than children with CAPD for the verbal a/-/da/ when the number of elements in the sequence varied. Children with sensory HL showed impaired ASO ability when recalling verbal /ba/-/da/. Results suggest that hearing loss can induce a specific signature when processing these verbal stimuli.

Presentation-order effects for aesthetic stimulus preference

For preference comparisons of paired successive musical excerpts, Koh (American Journal of Psychology, 80, 171-185, 1967) found time-order effects (TOEs) that correlated negatively with stimulus valence-the first (vs. the second) of two unpleasant (vs. two pleasant) excerpts tended to be preferred. We present three experiments designed to investigate whether valence-level-dependent order effects for aesthetic preference (a) can be accounted for using Hellström's (e.g., Journal of Experimental Psychology: Human Perception and Performance, 5, 460-477, 1979) sensation-weighting (SW) model, (b) can be generalized to successive and to simultaneous visual stimuli, and (c) vary, in accordance with the stimulus weighting, with interstimulus interval (ISI; for successive stimuli) or stimulus duration (for simultaneous stimuli). Participants compared paired successive jingles (Exp. 1), successive color patterns (Exp. 2), and simultaneous color patterns (Exp. 3), selecting the preferred stimulus. The results were well described by the SW model, which provided a better fit than did two extended versions of the Bradley-Terry-Luce model. Experiments 1 and 2 revealed higher weights for the second stimulus than for the first, and negatively valence-level-dependent TOEs. In Experiment 3, there was no laterality effect on the stimulus weighting and no valence-level-dependent space-order effects (SOEs). In terms of the SW model, the valence-level-dependent TOEs can be explained as a consequence of differential stimulus weighting in combination with stimulus valence varying from low to high, and the absence of valence-level-dependent SOEs as a consequence of the absence of differential weighting. For successive stimuli, there were no important effects of ISI on weightings and TOEs, and, for simultaneous stimuli, duration had only a small effect on the weighting.

The right hemisphere advantage in visual change detection depends on temporal factors

What accounts for the Right Hemisphere (RH) functional superiority in visual change detection? An original task which combines one-shot and divided visual field paradigms allowed us to direct change information initially to the RH or the Left Hemisphere (LH) by deleting, respectively, an object included in the left or right half of a scene presented centrally. We manipulated the perceptual salience and semantic relevance of the change as well as the duration of the Inter-Stimulus Interval (ISI) between the scenes in order to clarify the role of the RH in memory and attention processes, and to explore whether lengthening the ISI would enhance the contribution of the LH. When analyzing data collapsed over the two levels (high vs. low) of salience and of relevance, changes were better detected in the left visual field (lvf) than in the right visual field (rvf) in the case of a short ISI, while no difference emerged in the case of a long ISI. Moreover, lengthening the ISI resulted in a performance decrement in the lvf, both for accuracy and response speed. The fact that the RH superiority was limited to short intervals indicates that stimulus-driven orienting contributes more than perceptual processing to this hemispheric asymmetry. When considering perceptual and semantic properties of the change, the effect of the ISI duration seemed to specifically emerge in the case of low relevance, with an enhancement of accuracy in the rvf when comparing the long with the short ISI. This suggests that the ISI influence on hemispheric performance operates on different levels.

Does a sensory processing deficit explain counting accuracy on rapid visual sequencing tasks in adults with and without dyslexia?

The experiments conducted aimed to investigate whether reduced accuracy when counting stimuli presented in rapid temporal sequence in adults with dyslexia could be explained by a sensory processing deficit, a general slowing in processing speed or difficulties shifting attention between stimuli. To achieve these aims, the influence of the inter-stimulus interval (ISI), stimulus duration, and sequence length were evaluated in two experiments. In the first that used skilled readers only, significantly more errors were found with presentation of long sequences when the ISI or stimulus durations were short. Experiment 2 used a wider range of ISIs and stimulus durations. Compared to skilled readers, a group with dyslexia had reduced accuracy on two-stimulus sequences when the ISI was short, but not when the ISI was long. Although reduced accuracy was found on all short and long sequences by the group with dyslexia, when performance on two-stimulus sequences was used as an index of sensory processing efficiency and controlled, group differences were found with presentation of stimuli of short duration only. We concluded that continuous, repetitive stimulation to the same visual area can produce a capacity limitation on rapid counting tasks in all readers when the ISIs or stimulus durations are short. While reduced accuracy on rapid sequential counting tasks can be explained by a sensory processing deficit when the stimulus duration is long, slower processing speed in the group with dyslexia explains the greater inaccuracy found as sequence length is increased when the stimulus duration is short.

Nicotine enhances automatic temporal processing as measured by the mismatch negativity waveform

Cholinergic agonists and, more specifically, nicotine, have been found to enhance a number of cognitive processes. The effect of nicotine on temporal processing is not known. The use of behavioral measures of temporal processing to measure its effect could be confounded by the general effects of nicotine on attention. Mismatch negativity (MMN) has been used as a physiological measure of automatic temporal processing to avoid this potential confound. A total of 20 subjects (11 nonsmokers and 9 smokers following 2 hr of abstinence) participated in a two-visit single-blind, placebo-controlled crossover study of the effect of nicotine on MMN indices in response to an interstimulus interval deviant. Nicotine-enhanced MMN amplitudes from baseline recording to postdrug recording greater than did the placebo condition. This enhancement was seen in both nonsmokers and smokers. Nicotine had no significant effect on MMN latency or N100 amplitude or latency. This is the first study to demonstrate a nicotine-related enhancement of MMN amplitude to an interstimulus interval duration deviant and confirms our hypothesis that nicotine enhances preattentive temporal processing. Nicotinic agonists may represent a potential therapeutic option for individuals with abnormalities in early sensory or temporal processing related to cholinergic system abnormalities. Methodologically, our paradigm of nicotine administration in abstinent smokers is important because it resulted in both minimal withdrawal symptoms and meaningful data that are not attributable solely to relief of withdrawal.

Psychophysical properties of two-stroke apparent motion

In two-stroke apparent movement, repeated presentation of a two-frame pattern displacement followed by a brief inter-stimulus interval (ISI) can create an impression of continuous forward motion (G. Mather, 2006). Does the ISI in two-stroke motion just break the connection between adjacent frames, switching off the motion signal they normally generate, or does it actually generate a reversed motion signal? Reversed apparent motion in two-frame stimuli separated by a brief ISI has been reported in several previous papers (ISI reversal), which found that the effect is optimal at short, mean-luminance ISIs, and is abolished at scotopic luminances. A series of five experiments compared two-stroke apparent motion with ISI reversal using the same stimulus display. The two effects show the same dependence on ISI duration and luminance and are both abolished at low mean luminance. Results therefore support the conclusion that the ISI in two-stroke apparent motion does contribute a reversed motion signal and constrain theoretical explanations of two-stroke apparent motion.