Retention of time information in forced-choice duration discrimination

We explore the effect on performance in a forced-choice duration-discrimination task of varying the interstimulus interval (ISI) from 0 to 2 sec. The durations were brief empty intervals (115–285 msec) bounded by very brief auditory pulses. Performance improved as the ISI increased from 0 to 1/2 sec, but a further increase in ISI up to 2 sec resulted in little further change in performance. The “time information” derived from a brief interval bounded by auditory pulses does not appear to be susceptible to the very short-term perceptual memory loss inferred in other auditory discriminations.     

Response preparation with anticues in children and adults

We examined the ability of children (mean age: 10.4 years) and adults (mean age: 20.7 years) to prepare finger keypress responses in an anticue paradigm by presenting left and right spatial cues, which specified right and left hand finger responses, respectively. Four time intervals separated cue onset from target onset: 200 ms, 600 ms, 1000 ms, and 2000 ms. Results showed that, overall, children responded slower and less accurately than did adults; nevertheless they were equally effective in using anticue information to reduce reaction time with preparation intervals of 600 ms and longer. This outcome is discussed in terms of a slow, voluntary, top-down executive process that redirects motor preparation from the ipsi- to the contralateral hand. The absence of an age effect suggests an early maturation of the underlying neural mechanisms.     

Consciousness is slower than you think

In easy serial choice reaction time tasks (CRT tasks) young adults can very rapidly "correct" nearly all their errors by making the responses that they should have made (error-correcting responses). They are much less accurate at signalling their errors by making the same, deliberate, response to each (error-signalling responses), and they poorly remember errors that they have not signalled or corrected. When instructed to ignore errors they nevertheless involuntarily register them because the response immediately following them (responses following unacknowledged errors) are unusually slow, and they sometimes make involuntary error correction responses. Errors that are neither signalled nor remembered are registered at some level because responses following unacknowledged errors are slowed. Old age does not impair the accuracy of error correction or reduce the proportion of errors that are acknowledged because they are followed by unusually slow responses, but it does reduce the accuracy of error signalling and of recall of errors. Groups of 40 young adults (mean age 20.1 years, SD 1.1) and 40 older adults (mean 71.2 years, SD 5.1) signalled and recalled their errors increasingly accurately as intervals between each response and the next signal were increased from 150 ms to 1000 ms. Error signalling and recall improved as response-signal interval (RSI) durations increased, reaching asymptote at RSIs of 800 ms for the young and 1000 ms for the older adults. Thus processes necessary for conscious and deliberate choice or error-signalling responses and for subsequent recall of errors require more than 150 ms to complete, are slowed by old age, and may be interrupted by onset of new signals occurring earlier than 800 to 1000 ms after completion of an incorrect response.     

认知老化中有意控制对自动抑制的调节作用

结合比例控制范式与基于空间位置的返回抑制范式, 探讨了认知老化过程中自上而下的有意认知控制对自动抑制的调节作用。结果表明, 当线索有效率由50%提升至80%时, 两组被试的返回抑制量均下降, 老年组表现为返回抑制消失, 但年轻组出现返回抑制的反转, 表明有意认知控制对自动抑制的调节作用受认知老化的影响而发生衰减。同时文章还就认知老化机制的新兴理论—— 执行衰退假说进行了讨论。     

Echoic memory in the rat: effects of inspection time, retention interval, and the spectral composition of masking noise.

Memory for tones (1100 vs. 2330 Hz) was studied in 4 rats (Rattus norvegicus), as affected by the durations of both target tones (30 to 620 ms) and noise-filled retention intervals (0 to 480 ms). With a 0-ms delay, performance was near asymptotic with the 30-ms tone, but the memory of this brief tone suffered a massive decrement at retention intervals as brief as 60 ms; in contrast, memory for the 340-ms tone was stable for at least 240 ms. If the retention interval was filled by band-stop noise (with targets presented in the spectral gap), then the rat's memory for brief tones was superior to that obtained with the standard broad-band noise filler, and band-stop noise was better than a band-pass noise that had the tones embedded in the region of its spectral energy. These findings are consistent with the hypotheses that auditory memory in the rat consists of a transient sensorylike echoic store and a short-term store more resistant to the effects of retroactive interference.     

The effects of type of interval,sensory modality,base duration,and psychophysical task on the discrimination of brief time intervals

The present study was designed to investigate the influences of type of psychophysical task (two-alternative forced-choice [2AFC] and reminder tasks), type of interval (filled vs. empty), sensory modality (auditory vs. visual), and base duration (ranging from 100 through 1,000 ms) on performance on duration discrimination. All of these factors were systematically varied in an experiment comprising 192 participants. This approach allowed for obtaining information not only on the general (main) effect of each factor alone, but also on the functional interplay and mutual interactions of some or all of these factors combined. Temporal sensitivity was markedly higher for auditory than for visual intervals, as well as for the reminder relative to the 2AFC task. With regard to base duration, discrimination performance deteriorated with decreasing base durations for intervals below 400 ms, whereas longer intervals were not affected. No indication emerged that overall performance on duration discrimination was influenced by the type of interval, and only two significant interactions were apparent: Base Duration × Type of Interval and Base Duration × Sensory Modality. With filled intervals, the deteriorating effect of base duration was limited to very brief base durations, not exceeding 100 ms, whereas with empty intervals, temporal discriminability was also affected for the 200-ms base duration. Similarly, the performance decrement observed with visual relative to auditory intervals increased with decreasing base durations. These findings suggest that type of task, sensory modality, and base duration represent largely independent sources of variance for performance on duration discrimination that can be accounted for by distinct nontemporal mechanisms.     

How well do elderly people cope with uncertainty in a learning task?

The relation between age, task complexity and learning performance in a Multiple Cue Probability Learning task was studied by systematically varying the level of uncertainty present in the task, keeping constant the direction of relationships. Four age groups were constituted: young adults (mean age = 21), middle-aged adults (45), elderly people (69) and very elderly people (81). Five uncertainty levels were considered: predictability = 0.96, 0.80, 0.64, 0.48, and 0.32. All relationships involved were direct ones. A strong effect of uncertainty on 'control', a measure of the subject's consistency with respect to a linear model, was found. This effect was essentially a linear one. To each decrement in predictability of the task corresponded an equal decrement in participants' level of control. This level of decrement was the same, regardless of the age of the participant. It can be concluded that elderly people cope with uncertainty in probability learning tasks as well as young adults.     

Age-Related Changes in Temporal Allocation of Visual Attention: Evidence From the Rapid Serial Visual Presentation (RSVP) Paradigm

The present study explored the temporal allocation of attention in groups of 8-year-old children, 10-year-old children, and adults performing a rapid serial visual presentation task. In a dual-condition task, participants had to detect a briefly presented target (T2) after identifying an initial target (T1) embedded in a random series of distractors. A single-condition control task required participants to detect T2 without first identifying T1. The attentional blink (AB) reflects impairments in T2 detection due to the previous identification of T1. Although the amplitude of the AB (difference in T2 detection performance between the single task and the dual task) was found to be similar across age groups, its temporal expression (as a function of the T1–T2 lag) differed across age groups. Our results revealed age-related changes a) in the duration of the first lag(s) sparing effect (longer in the younger age groups), b) in the peak position of the AB (temporal displacement toward later lags in the younger age groups), and c) in the width of the AB (T2 impairments occurring for T1–T2 intervals of 400 ms and 500 ms in 8-year-old children, 300 ms in 10-year-old children, and 200 ms and 300 ms in adults). We discuss these differences in terms of changes in the efficiency of perceptual selection and inhibitory processes (attentional gating mechanisms) during development.     

Age-related differences in lexical access, spreading activation, and simple pronunciation

An experiment was conducted to address age-related differences in lexical access, spreading activation, and pronunciation. Both young and older adults participated in a delayed pronunciation task to trace the time course of lexical access and a semantic priming task to trace the time course of spreading activation. In the delayed pronunciation task, subjects were presented a word and then, after varying delays, were presented a cue to pronounce the word aloud. Older adults benefited considerably more from the preexposure to the word than did the younger adults, suggesting an age-related difference in lexical access time. In the semantic priming pronunciation task, semantic relatedness (related vs. neutral), strength of the relationship (high vs. low), and prime-target stimulus onset asynchrony (200 ms, 350 ms, 500 ms, 650 ms, and 800 ms) were factorially crossed with age to investigate age-related differences in the buildup of semantic activation across time. The results from this task indicated that the activation pattern of the older adults closely mimicked that of the younger adults. Finally, the results of both tasks indicated that older adults were slower at both their onset to pronounce and their actual production durations (i.e., from onset to offset) in the pronunciation task. The results were interpreted as suggesting that input and output processes are slowed with age, but that the basic retrieval mechanism of spreading activation is spared by age.     

Children and adults' distance estimations in a large-scale environment: effects of time and clutter

In two experiments adults (mean age = 19-5), sixth graders (mean age = 11-8), fourth graders (mean age = 9-8), and second graders (mean age = 7-8) walked a straight line distance through a large-scale environment. Subjects were then asked to estimate the time taken to traverse each half of the walk and to estimate the distance between objects seen along the walk. In Experiment 1 each half of the walk was traversed in the same amount of time but contained a different number of objects (clutter). Time and distance estimates were related, but were not affected by the number of intervening objects encountered between locations. In Experiment 2 subjects again encountered a different number of objects along each half of the walk but each half was traversed in varying amounts of time. Again, time and distance estimates were related, and there was no clutter effect. There were no consistent developmental differences across the two experiments. It was concluded that (1) Thorndyke's clutter effect does not occur across all types of spatial cognition tasks, and (2) children and adults tend to relate time and distance across a variety of distance estimation tasks.     

Sensory effects on judgments of short time-intervals

Two experiments were conducted to test the effect of nontemporal factors on duration discrimination. In Exp. 1, a forced-choice adaptive procedure with a standard duration of 400 or 800 ms was employed. It was shown that, for both auditory and visual modes, the discrimination is better with empty intervals (a silent period between two brief signals) than with filled intervals (a continuous signal), but only with shorter durations. In a second experiment, where intervals of the same duration range were employed but were presented with a single-stimulus method, discrimination was better with empty than with filled intervals, and this effect applied to both ranges of duration and both sensory modes. In both experiments, discrimination was better in the auditory than in the visual mode. These data are discussed in the context of current models of timing mechanisms. Received: 16 October 1997 / Accepted: 30 April 1998     

Effects of temporal shapes of sound markers on the perception of interonset time intervals

This study investigated how the temporal characteristics, particularly durations, of sounds affect the perceived duration of very short interonset time intervals (120-360?ms), which is important for rhythm perception in speech and music. In four experiments, the subjective duration of single time intervals marked by two sounds was measured utilizing the method of adjustment, while the markers' durations, amplitude difference (which accompanied the duration change), and sound energy distribution in time were varied. Lengthening the duration of the second marker in the range of 20-100?ms increased the subjective duration of the time interval in a stable manner. Lengthening the first marker tended to increase the subjective duration, but unstably; an opposite effect sometimes appeared for the shortest time interval of 120?ms. The effects of varying the amplitude and the sound energy distribution in time of either marker were very small in the present experimental conditions, thus proving the effects of marker durations per se.     

Age differences in executive functioning across the lifespan: the role of verbalization in task preparation

Age-related changes in executive functioning across the lifespan were assessed in children (mean age=9.4 years), younger adults (mean age=21.5 years), and older adults (mean age=65.3 years). Executive functioning was investigated with a task-switching paradigm that permits the separation of two control components: to select and to switch between task sets. The specific aims of this study were (a) to determine developmental functions in both control components across the lifespan; and (b) to examine whether age-related changes in these components are influenced by verbal prompts during task preparation. The results revealed an inverted u-shaped developmental function for the ability to select between task sets but not for the ability to switch between task sets. In contrast to younger adults and children, older adults generally benefited from verbalizations during task preparation. Children, but not older adults, showed a facilitation of task execution when verbal prompts were task-compatible. Conversely, older adults, but not children, showed stronger interference when verbal prompts are task-incompatible. Our findings suggest that inner speech in an important modulator of developmental changes in executive functioning across the lifespan.     

Effect of preparation on dual-task performance in postural control

The authors applied an overlapping-task design to study the interaction between postural control and cognitive task processes in young (n = 10) and older (n = 10) adults. A rapid destabilizing floor translation was followed at specific time intervals by a simple auditory reaction time (RT) task. The translations were preceded by either an informational cue or no cue. Interference between postural task demands and the RT task was found only in the first 50 ms. Cueing also had an effect on both the onset of the postural recovery response and RT performance. The results suggest (a) only a brief interference between postural and cognitive processing demands in relatively easy tasks, (b) competition for a common central mechanism, possibly a response-selection mechanism, and (c) no differential impact of aging on that interaction.     

The development of attentional orienting during the school‐age years

This study was designed to assess the development of spatial attentional orienting during the school‐age years. To that end, we used a cost‐benefit attentional cueing task with short (100 ms) and long (800 ms) cue‐to‐target intervals to examine attentional processing independent of motor skills and perceptual processing in 200 7–17‐year‐olds and 40 adults. We found that orienting attention, disengaging attention and visual processing in an unattended location, were all progressively more accurate and faster with increasing age. Our data thus suggest that the efficiency of attentional orienting improves in an age‐related manner throughout the school‐age years.     

Ageing and switching of the focus of attention in working memory: results from a modified N-back task.

We conducted two experiments using a modified version of the N-Back task. For younger adults, there was an abrupt increase in reaction time of about 250 ms in passing from N = 1 to N > 1, indicating a cost associated with switching of the focus of attention within working memory. Response time costs remained constant over the range N = 2 to N = 5. Accuracy declined steadily over the full range of N (Experiment 1). Focus switch costs did not interact with either working memory updating (Experiment 1), or global task switching (Experiment 2). There were no age differences in RT costs once general slowing was taken into account, but there was a larger focus-switch-related accuracy cost in older adults than in younger adults. No age sensitivity was found for either updating or global task switching. The results suggest (a) that focus switching is a cognitive primitive, distinct from task switching and updating, and (b) that focus switching shows a specific age-related deficit in the accuracy domain.     

QT & RR variability spots the earliest autonomic deregulation in diabetes. Fading of vagal sino-atrial drive but not of sympathetic ventricular responsiveness to life challenges.

27 consecutive insulin-dependent diabetic patients (pts), under 50 years, with blood glucose controlled within normal limits and no significant or multiple cardiovascular/neurological complications in the lights of clinical tests, went through a protocol as follows: laiddown at relaxed rest for 10 min, then stood-up quietly for 7 min, and finally experienced a stress-interview for 10 min while supine. A thoracic ECG lead was digitized at I ms (Codas, Dataq Instr.), RR and QT intervals were software-detected, resampled at 500 ms, and Fourier-transformed over 3 min epochs to get auto-or cross-spectra. RR-by-QT mean square coherence detached the RR-independent fraction of QT low fequency (LF) spectral power, called idioventricular QT-LF. We detected autonomic impairment of three types (discriminant score = 92.31%), presumably differentiated upon the locus of lesion, using RR's basal variance and mean RR shortening when standing as follows: (I) RR shortening > 200 ms in 10 pts; (II) normal RR shortening but no RR variance in 4 pts; (III) stiff RR around 600 ms and no RR variance in 2 pts. The above pts have been excluded from further analysis. The remaining 11 pts with no such impairments (5M and 6F, 36.4 y +/- 4.4 SD, history of 6.0 y +/- 5.2) have been compared with 11 normal subjects in an age and gender-paired control group in two steps. Step 1: Preliminary MANOVA/ANOVA showed significant effects on the ensemble of spectral variables of every single factor (status: normal or patient group; intervention; gender) with no significant factor interactions. Significant effects of intervention or status on main RR spectral variables and on a few QT spectral variables were also documented. Step 2: Non-parametric tests showed that diabetics had (mildly to moderately) shorter mean RR, while their RR-LF was always significantly lower than those found in normals--a difference propagated to QT-LF but not to idioventricular QT-LF. In the intra-group there were similar responses to interventions except stress with respect to mean RR. Consistent reduction in RR-LF under moderate or no change in mean RR suggests vagal down- regulation that, judging by idioventricular QT-LF showing, goes perhaps before a similar process with sympathetic control of ventricles. This phase delay may introduce an early arrhythmic risk worth dealing with in secondary prevention.     

Actively Controlling Anticipation of Irregular Events

There have been no investigations as to how people respond to sequences of events which occur at brief, unpredictable intervals as in everyday life. Eleven young adults were practised at a two-choice, continuous, serial choice-response task in which intervals between each response and the onset of the next signal (RSIs) varied randomly from trial to trial. On half the trials in each of four conditions the RSI was 20 ms, and on the other trials 200, 400, 800 and 1600 ms respectively. Reaction times fell as RSIs increased from 20-200 ms but thereafter appeared to be unaffected by RSI duration. In the 20/200 and 20/400 ms RSI conditions RT was not affected by transitions between different RSIs but in the 20/800 and 20/1600 ms conditions RTs were faster when the longer RSI recurred on immediately successive trials than if the long RSI followed the short (20 ms) RSI. These results are discussed in terms of a control system model for the way in which subjects actively trade off between their internal performance limitations to optimally meet task demands.     

Variable foreperiods and temporal discrimination

Temporal judgements are often accounted for by a single-clock hypothesis. The output of such a clock is reported to depend on the allocation of attention. In the present series of experiments, the influence of attention on temporal information processing is investigated by systematic variations of the period preceding brief empty intervals to be judged. Two indicators of timing performance, temporal sensitivity, reflecting discrimination performance, and perceived duration served as dependent variables. Foreperiods ranged from 0.3 to 0.6 s in Experiments 1 to 4. When the foreperiod varied randomly from trial to trial, perceived duration was longer with increasing length of foreperiod (Experiments 1 and 3 with brief auditory markers and Experiment 4 with brief visual markers), an effect that disappeared with no trial-to-trial variations (Experiment 2). Longer foreperiods also enhanced performance on temporal discrimination of auditory empty intervals with a base duration of 100 ms (Experiments 1 and 5), whereas discrimination performance was unaffected for auditory intervals with a base duration of 500 ms (Experiment 3). The variable-foreperiod effect on perceived duration also held when foreperiods ranged from 0.6 to 1.5 s (Experiments 5-7). Findings suggest that foreperiods appear to effectively modulate attention mechanisms necessary for temporal information processing. However, alternative explanations such as assimilation or compatibility effects cannot be totally discarded.     

The structure of sensory events and the accuracy of time judgments

We investigated how does the structure of empty time intervals influence temporal processing. In experiment 1, the intervals to be discriminated were the silent durations marked by two sensory signals, both lasting 10 or 500 ms; these signals were two identical flashes (intramodal: VV), or one visual flash (V) followed by an auditory tone (A) (intermodal: VA). For the range of duration under investigation (standards = 0.2, 0.6, 1, or 1.4 s), the results indicated that both the marker length and sensory mode influenced discrimination, but no interaction between these variables or between one of these variables and standard duration was significant. In experiment 2, we compared, for each of four marker-type conditions (VV, AA, VA, AV; and standard = 1 s), intervals marked by two 10 ms signals with intervals marked by unequal signal length (markers 1 and 2 lasting 10 and 500 ms, or 500 and 10 ms). As in experiment 1, the results revealed significant marker-mode and marker-length effects, but no significant interaction between these variables. Experiment 3 showed that, for the same conditions as in experiment 2, perceived duration is not influenced by marker length and that the variability of interval reproductions does not depend on the perceived duration of intervals. The results are discussed in the light of a single-clock hypothesis: marker-length and marker-mode effects are presented as being non-temporal sources of variability associated mainly with sensory and memory processes.