Dissociating visuo-spatial and verbal working memory: It's all in the features.

Echoing many of the themes of the seminal work of Atkinson and Shiffrin (The Psychology of Learning and Motivation, 2; 89-195, 1968), this paper uses the feature model (Nairne, Memory & Cognition, 16, 343-352, 1988; Nairne, Memory & Cognition, 18; 251-269, 1990; Neath & Nairne, Psychonomic Bulletin & Review, 2; 429-441, 1995) to account for performance in working-memory tasks. The Brooks verbal and visuo-spatial matrix tasks were performed alone, with articulatory suppression, or with a spatial suppression task; the results produced the expected dissociation. We used approximate Bayesian computation techniques to fit the feature model to the data and showed that the similarity-based interference process implemented in the model accounted for the data patterns well. We then fit the model to data from Guérard and Tremblay (2008, Journal of Experimental Psychology: Learning, Memory, and Cognition, 34, 556-569); the latter study produced a double dissociation while calling upon more typical order reconstruction tasks. Again, the model performed well. The findings show that a double dissociation can be modelled without appealing to separate systems for verbal and visuo-spatial processing. The latter findings are significant as the feature model had not been used to model this type of dissociation before; importantly, this is also the first time the model is quantitatively fit to data. For the demonstration provided here, modularity was unnecessary if two assumptions were made: (1) the main difference between spatial and verbal working-memory tasks is the features that are encoded; (2) secondary tasks selectively interfere with primary tasks to the extent that both tasks involve similar features. It is argued that a feature-based view is more parsimonious (see Morey, 2018, Psychological Bulletin, 144, 849-883) and offers flexibility in accounting for multiple benchmark effects in the field.

Bivalent task switching and memory load: Similar costs on reaction times, different costs on concurrent timing.

Some studies suggest that time estimation involves executive control resources. This proposition was challenged recently, however, by results showing simultaneous performance of executive and timing tasks with no cost. The present study examined whether bivalent switching, in which targets may be relevant in more than one task, would interfere with timing. In Experiment 1, the effect of switching between memory search and a classification task was compared with the effect of varying load in memory search. Effects of task switching and of increasing load were similar on reaction times (RTs) in an RT control condition, but drastically different on concurrent timing: Time productions were affected by memory search only. In Experiment 2, the effect of task switching preparation, which involves advance reconfiguration in the switching paradigm, was examined. Preparation to a switch and timing could be performed simultaneously with no cost. These results reveal a fundamental difference between memory search and task switching in terms of dual-task costs, and show that timing and some executive control tasks do not share cognitive resources.

Parallel effects of memory set activation and search on timing and working memory capacity.

Accurately estimating a time interval is required in everyday activities such as driving or cooking. Estimating time is relatively easy, provided a person attends to it. But a brief shift of attention to another task usually interferes with timing. Most processes carried out concurrently with timing interfere with it. Curiously, some do not. Literature on a few processes suggests a general proposition, the Timing and Complex-Span Hypothesis: A process interferes with concurrent timing if and only if process performance is related to complex span. Complex-span is the number of items correctly recalled in order, when each item presented for study is followed by a brief activity. Literature on task switching, visual search, memory search, word generation and mental time travel supports the hypothesis. Previous work found that another process, activation of a memory set in long term memory, is not related to complex-span. If the Timing and Complex-Span Hypothesis is true, activation should not interfere with concurrent timing in dual-task conditions. We tested such activation in single-task memory search task conditions and in dual-task conditions where memory search was executed with concurrent timing. In Experiment 1, activating a memory set increased reaction time, with no significant effect on time production. In Experiment 2, set size and memory set activation were manipulated. Activation and set size had a puzzling interaction for time productions, perhaps due to difficult conditions, leading us to use a related but easier task in Experiment 3. In Experiment 3 increasing set size lengthened time production, but memory activation had no significant effect. Results here and in previous literature on the whole support the Timing and Complex-Span Hypotheses. Results also support a sequential organization of activation and search of memory. This organization predicts activation and set size have additive effects on reaction time and multiplicative effects on percent correct, which was found.

Estimating averages from distributions of tone durations.

We examined whether estimating average duration was influenced by the distribution peak location. We presented participants with samples of various tone durations and then presented comparison tone durations. Participants judged whether each comparison duration was longer than the average sample duration. Estimates of the averages were inferred from the psychophysical functions. The durations were sampled from three distributions: one positively skewed, one symmetric, and one negatively skewed. In Experiment 1, every participant was presented with every distribution. Estimates of the averages were unbiased for the symmetric distribution but were biased toward the long tail of each skewed distribution. This would occur if participants combined the sample to be judged with the previous, irrelevant samples, or with the comparison durations. In Experiment 2, each participant was presented with samples from only one of the distributions. Estimates of the averages were still biased toward the long tails of the skewed distributions. This would occur if participants combined the sample to be judged with the comparison durations, which were the same for the three distributions. In Experiment 3, each participant was presented with only one distribution, and each distribution was tested with its own comparison durations, selected as percentiles from the distribution. The estimates were accurate for the smallest population mean (positively skewed distribution) but underestimated the larger means. These results could be explained by subjective shortening of the durations in memory, with a simple equation from scalar timing theory. This equation correctly predicted two results: The estimated averages were a linear function of the stimulus means, and the variances were a linear function of the squared stimulus means. Neither prediction was dependent on the skewness of the stimulus durations.

To count or not to count: the effect of instructions on expecting a break in timing.

When a break is expected during a time interval production, longer intervals are produced as the break occurs later during the interval. This effect of break location was interpreted as a result of distraction related to break expectancy in previous studies. In the present study, the influence of target duration and of instructions about chronometric counting strategies on the break location effect was examined. Using a strategy such as chronometric counting enhances the reliability of temporal processing, typically in terms of reduced variability, and could influence how timing is affected by break expectancy, especially when relatively long target durations are used. In two experiments, results show that time productions lengthened with increasing value of break location at various target durations and that variability was greater in the no-counting than in the counting instruction condition. More important, the break location effect was stronger in the no-counting than in the counting instruction condition. We conclude that chronometric counting orients attention toward timing processes, making them less likely to be disrupted by concurrent nontemporal processes.

[Category-specific deficits in semantic dementia: links between perception and semantic knowledge]. / L'altération des connaissances sémantiques est-elle liée à une altération du traitement perceptif ? Étude des atteintes catégories-spécifiques dans la démence sémantique.

The nature of knowledge and its relationship with the perceptual processes are among the most central issues in the study of human cognition. Should knowledge be abstract, then semantic memory and perception should be relatively independent. On the contrary, if knowledge is sensory-dependent, then memory and perception should be very close. The first view is supported by the multiple system approach of memory, whereas the second view is supported by the single-store memory theories. One way to study these links is through the category-specific impairment and the sensory-functional theory (SFT). Category-specific impairment is generally observed for living items compared to artefacts. The SFT explains this deficit by defining living items as essentially based on perception. In the abstract view of knowledge, a living deficit should be related to a deficit in processing sensory knowledge. On the opposite, the sensory-dependent view states that this deficit results from perception impairment. This article focuses on the relations between knowledge and perception in semantic dementia (SD). SD is characterized by a progressive loss of semantic knowledge, making it particularly interesting to study. This article first focuses on the SFT, to explain the category-specific impairment. The issue of perceptual processing in SD is then reviewed from the lowest level (senses) to the highest level of perception (multimodal integration). The data demonstrated normal perception for these patients. However, visual integration appeared to be impaired for existing knowledge. This result is discussed in relation with a possible involvement of the anterior temporal lobes. These regions are known to be the most vulnerable in SD. Recently these regions have also been shown to be involved in the multimodal integration. Taken together, these data suggest that perception and knowledge could be linked and partially explained by the SFT. Finally, the data support the sensory-dependent approaches of memory.

Modulating the interference effect in timing with varying stimulus onset asynchrony.

The interference effect on time judgments, when subjects are also required to perform a concurrent nontemporal task, is one of the most reliable findings in the time perception literature. In the present study, the interference between a time discrimination task (short or long tone) and a digit classification task (even or odd digit) was analysed using the overlapping tasks paradigm. Reaction times in the digit task were shorter at longer values of stimulus onset asynchrony (SOA) in Experiment 1, showing a clear modulation of interference with varying the relative position of the tasks. Using longer tone durations in Experiment 2, reaction times in the digit task were affected not only by the overlap between the tasks but also by the temporal proximity of responses in the timing and digit tasks. In Experiment 3, the effect of varying the SOA on performance on the digit task was abolished when the auditory tone was irrelevant, thus eliminating an interpretation in terms of distraction from the tone offset. We conclude that the interference effect in concurrent time discrimination and digit classification may be modulated by the degree of overlap between the tasks as well as by the overlap between late processing stages related to decision and response components in the 2 tasks.

Concurrency benefits in the attentional blink: attentional flexibility and shifts of decision criteria.

Fundamental limitations in performing multiple tasks concurrently are well illustrated by the attentional blink (AB) deficit, which refers to the difficulty in reporting a second target (T2) when it is presented shortly after a first target (T1). Surprisingly, recent studies have shown that the AB, which is often thought of as a manifestation of capacity limitations in central processing, can be reduced when the AB task is performed simultaneously with concurrent distracting activities. In the present study, we sought to investigate whether such concurrency benefits would also be observed when the AB task was performed concurrently with a central demanding timing task. The AB was reduced under concurrent-task conditions, as compared with single-AB-task conditions, even though T1 performance was unaffected by the concurrent task. Moreover, shifts in decision criteria were found to be associated with the concurrency benefit effect.

Timing is affected by demands in memory search but not by task switching.

Recent studies suggest that timing and tasks involving executive control processes might require the same attentional resources. This should lead to interference when timing and executive tasks are executed concurrently. This study examined the interference between timing and task switching, an executive function. In 4 experiments, memory search and digit classification were performed successively in 4 conditions: search-search (search followed by search), search-digit, digit-search, and digit-digit. In a control reaction time (RT) condition, participants provided RT responses in each of the 2 tasks. In a time production condition, an RT response was provided to the first stimulus, but the response to the second stimulus, S2, was given only when participants judged that a previously presented target duration had elapsed. When responding to S2 required a switch, RTs to S2 were longer, but produced intervals were unaffected. These results show that memory search affects concurrent timing, but not task switching. Task switching seems therefore to be 1 executive function that does not interfer with timing.

Contrasting effects of interference and of breaks in interval timing.

When a break is introduced during an interval to be timed, the interval is perceived shorter as break location is delayed. This is interpreted as a result of attention sharing between timing and monitoring the source of the break signal. Similar effects and interpretations are found in another context involving interfering tasks. Such tasks are assumed to induce transient interruptions in timing, comparable to those obtained with breaks. Break and interference conditions were contrasted in a temporal reproduction procedure with identical stimuli. Both conditions induced temporal underestimation and similar location effects. Similar trends occurred in a control condition where no processing of the interfering signal was required. The data suggest that expectancy, intentional processing, and automatic attraction of attention shorten temporal estimates.

Expectancy in humans in multisecond peak-interval timing with gaps.

In two experiments, the peak-interval procedure was used with humans to test effects related to gaps in multisecond timing. In Experiment 1, peak times of response distributions were shorter when the gap occurred later during the encoding of the criterion time to be reproduced, suggesting that gap expectancy shortened perceived durations. Peak times were also positively related to objective target durations. Spreads of response distributions were generally related to estimated durations. In Experiment 2, peak times were shortest when gaps were expected but did not occur, confirming that the shortening effect of gap expectancy is independent of the gap occurrence. High positive start-stop correlations and moderate positive peak-time-spread correlations showed strong memory variability, whereas low and negative start-spread correlations suggest small response-threshold variability. Correlations seemed not to be influenced by expectancy. Overall, the peak-interval procedure with gaps provided relevant information on similarities and differences in timing in humans and other animals.

Effects of aerobic exercise training and irbesartan on blood pressure and heart rate variability in patients with chronic obstructive pulmonary disease.

BACKGROUND AND OBJECTIVES: The present pilot study was undertaken to evaluate the efficacy of an aerobic exercise training (AET) program alone or combined with an antihypertensive agent (irbesartan) to reduce blood pressure (BP) and enhance heart rate variability (HRV) in chronic obstructive pulmonary disease patients. METHODS: Twenty-one patients were randomly assigned to a double-blind treatment with exercise and placebo (n=11) or exercise and irbesartan (n=10). Subjects underwent 24 h BP monitoring and 24 h electrocardiographic recording before and after the 12-week AET. HRV was investigated using three indexes from the power spectral analysis and three indexes calculated from the time domain. The AET program consisted of exercising on a calibrated ergocycle for 30 min three times per week. Five patients in the placebo group were excluded during follow-up because they were not compliant. RESULTS: There was no change in 24 h systolic and diastolic BP before (130+/-14 mmHg and 70+/-3 mmHg, respectively) and after (128+/-8 mmHg and 70+/-8 mmHg, respectively) exercise training in the placebo group, whereas in the irbesartan group systolic and diastolic BP decreased from 135+/-9 mmHg and 76+/-9 mmHg to 126+/-12 mmHg and 72+/-8 mmHg, respectively (P<0.02). There were no changes in HRV parameters in either group. CONCLUSIONS: The present study suggests that a 12-week AET program is not associated with a significant reduction in BP or enhancement in HRV, whereas an AET program combined with irbesartan is associated with a reduction in 24 h BP.

Attention sharing during timing: modulation by processing demands of an expected stimulus.

Varying the location of a nontemporal task during a time estimation task affects temporal estimates. Previous studies have also shown that manipulating the location of a stimulus to ignore may disturb timing similarly, suggesting that the effect might be independent of the processing requirements in the nontemporal task. In Experiment 1, the location of a tone varied during a 2-sec interval production; participants were asked either to ignore the tone or to discriminate its frequency. Productions were longer when the tone was presented later, but only when it was processed. In Experiment 2, short and long tones corresponding to more or less difficult discrimination tasks were used. The location effect was stronger and remained stronger throughout the experiment when participants were tested with the short tone in the first experimental session than when they were tested with the long tone first. These results suggest that timing is influenced by relatively stable attention-sharing strategies.

Comparability of the clinical diagnostic criteria for vascular dementia: a critical review. Part I.

This review is the first of a two-part series focusing on the comparability of eight clinical criteria used for the diagnosis of vascular dementia: the Hachinski Ischemic Scale; the Ischemic Scale of Rosen; the criteria proposed by the Diagnostic and Statistical Manual of Mental Disorder-Third Edition (DSM-III), DSM-III-R, DSM-IV; International Classification of Diseases, 10th Revision (ICD-10); State of California Alzheimer's Disease Diagnostic and Treatment Centers (ADDTC); and the National Institute of Neurological Disorders and Stroke-Association Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN). The authors discuss the critical issues related to the definition of the cognitive syndromes as well as the vascular causes and associated heterogeneity of symptomatology across these criteria.

Validity of the clinical diagnostic criteria for vascular dementia: a critical review. Part II.

This review is the second of a two-part series focusing on the validity of eight clinical criteria for vascular dementia. Sixteen studies were selected according to their purposes and quality of experimental design. The analysis revealed that criteria for vascular dementia are not interchangeable; the eight criteria sets yielded different sensitivity and specificity results, as well as marked variability in incidence, prevalence, and frequency rates. Although the State of California Alzheimer's Disease Diagnostic and Treatment Centers (ADDTC) were the most sensitive and useful criteria in clinical settings and the National Institute of Neurological Disorders and Stroke-Association Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN) were the most specific and useful criteria in research, all criteria shared similar flaws. A definition of the cognitive syndrome, associated vascular causes or lesions, and methods of assessment should be clearly specified in the future. Suggestions for improvement are made.

Age-related differences in timing with breaks.

Two groups of participants differing in age were compared on a time production task during which timing was temporarily interrupted. Produced intervals lengthened with increasing delay before the break occurrence, and the effect was more pronounced in older than in younger adults. A reaction time response to the signal beginning the break period was required also. Older participants responded more slowly to this signal, but they benefited to a greater extent from a lengthening of the time preceding its presentation. These results suggest that performance of older participants is affected by attention sharing and preparation involved in timing with breaks.

Temporal order in memory and interval timing: an interference analysis.

The effect of varying load in memory tasks performed during a time interval production was examined. In a first experiment, increasing load in memory search for temporal order affected concurrent time production more strongly than varying load in a spatial memory task of equivalent difficulty. This result suggests that timing uses some specific resources also required in processing temporal order in memory, resources that would not be used in the spatial memory task. A second experiment showed that the interference between time production and memory search involving temporal order was stronger when, during the timing task, a decision was made on the temporal position of a memory item, than when information on temporal order was retained throughout the interval to be produced. These results underscore the importance of considering the specific resources and processes involved when the interference between timing and concurrent non-temporal tasks is analyzed.

Interrupting timing in interval production and discrimination: similarities and differences.

Interruptions in human timing have been studied in the last few years using temporal production and discrimination tasks. Expecting a break shortened perceived duration in both paradigms but manipulating break duration affected time production only, suggesting that preparatory processes might not take place in time discrimination. In time production, using cues revealed that providing information about the break may modulate the effect of break expectancy. For example, time was perceived as shorter when a break was expected in trials with no breaks, but forewarning participants of the break absence with a cue almost abolished the effect. In the present experiment, a tone was classified as "short" or "long" in a discrimination task. Location and duration of breaks were varied and cues were provided in some trials with no breaks. Results showed an effect of break expectancy: perceived duration shortened with increasing pre-break duration. Reducing expectancy with cues in uninterrupted tones decreased the proportion of "short" responses in long-tone trials, but not in short-tone trials. As in previous discrimination experiments, perceived duration was unaffected by varying break duration. Similarities and differences in results as well as in their interpretation when breaks are used in time production and time discrimination tasks are discussed.

Word frequency and the mixed-list paradox in immediate and delayed serial recall.

In free recall tasks, when low- and high-frequency items are mixed within the to-be-remembered lists, the usual recall advantage found for high-frequency words is eliminated or reversed. Recently, this mixed-list paradox has also been demonstrated for short-term serial recall (Hulme, Stuart, Brown, and Morin, 2003). Although a number of theoretical interpretations of this mixed-list paradox have been proposed, researchers have also suggested that it could simply be a result of participant-controlled strategies (M. J. Watkins, LeCompte, and Kim, 2000). The present study was designed to assess whether this explanation could be applied to immediate and delayed serial recall. The results showed that high-frequency words were recalled better than low-frequency words in pure lists, but that this effect was eliminated in mixed lists, whether they were given under intentional or incidental learning conditions. This pattern suggests that the mixed-list paradox cannot be explained by participant-controlled strategies.