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PubMed2001

Dissociation of verbal working memory system components using a delayed serial recall task.

Functional magnetic resonance imaging (fMRI) was used to investigate the neural substrates of component processes in verbal working memory. Based on behavioral research using manipulations of verbal stimulus type to dissociate storage, rehearsal, and executive components of verbal working memory, we designed a delayed serial recall task requiring subjects to encode, maintain, and overtly recall sets of verbal items for which phonological similarity, articulatory length, and lexical status were manipulated. By using a task with temporally extended trials, we were able to exploit the temporal resolution afforded by fMRI to partially isolate neural contributions to encoding, maintenance, and retrieval stages of task performance. Several regions commonly associated with maintenance, including supplementary motor, premotor, and inferior frontal areas, were found to be active across all three trial stages. Additionally, we found that left inferior frontal and supplementary motor regions showed patterns of stimulus and temporal sensitivity implicating them in distinct aspects of articulatory rehearsal, while no regions showed a pattern of sensitivity consistent with a role in phonological storage. Regional modulation by task difficulty was further investigated as a measure of executive processing. We interpret our findings as they relate to notions about the cognitive architecture underlying verbal working memory performance.

Adult↗
PubMed2004

Methodological and theoretical implications of intraindividual variability in perceptual-motor performance.

As an individual differences variable, lability (within-person variability) has often been neglected even though it has been shown to predict key outcomes such as mortality. We examine intraindividual variability in perceptual-motor performance and relate it to chronological age in a sample of adults. The magnitude of between-session variability was found to average between 25% and 50% of the between-person variability and was equivalent in magnitude to the variation that was apparent across an age range of 12 to 27 years in cross-sectional comparisons. Age is related to the magnitude of intraindividual variability, which in turn is negatively related to performance on other cognitive tasks. Various implications of the findings are discussed.

Adult↗
PubMed1982

Age-related effects of pacing on acquisition and performance of response sequences: an operant analysis.

Single-subject methods were used to study response speed in three younger men (M = 22 years) and three older men (M = 71 years). Monetary reinforcement depended on predetermined sequences of 10 responses. Training sessions consisted of alternating components; in one the sequence changed each session, but in the other the sequence never changed. During self-paced sessions stable patterns of acquisition (increasing rates of sequence completion, decreasing error rates) and of performance (uniform rates) emerged in the two components. During paced sessions responses had to occur within an interval ranging from .5 to 3 sec across conditions. Pacing had little effect on the younger men but disrupted the behavior of the older men, with increases in both omission and commission errors. Acquisition of new sequences was disrupted far more than performance of the established sequence. In both cases, however, the older men adjusted to pacing over the course of most sessions.

Adolescent↗
PubMed2001

Serial order effects in spelling errors: evidence from two dysgraphic patients.

This study reports data from two dysgraphic patients, TH and PB, whose errors in spelling most often occurred in the final part of words. The probability of making an error increased monotonically towards the end of words. Long words were affected more than short words, and performance was similar across different output modalities (writing, typing and oral spelling). This error performance was found despite the fact that both patients showed normal ability to repeat the same words orally and to access their full spelling in tasks that minimized the involvement of working memory. This pattern of performance locates their deficit to the mechanism that keeps graphemic representations active for further processing, and shows that the functioning of this mechanism is not controlled or "refreshed" by phonological (or articulatory) processes. Although the overall performance pattern is most consistent with a deficit to the graphemic buffer, the strong tendency for errors to occur at the ends of words is unlike many classic "graphemic buffer patients" whose errors predominantly occur at word-medial positions. The contrasting patterns are discussed in terms of different types of impairment to the graphemic buffer.

Aged↗
PubMed1988

Cognitive deficits and thought disorder: a retest study.

Manic (n = 26), schizophrenic (n = 26), and normal (n = 25) subjects were examined with a digit span distraction task and with a reality monitoring task. All subjects were tested twice at a 4-day interval, and a clinical assessment of thought disorder was conducted both times on the patients. We found that reality monitoring, distraction task performance, and clinical thought disorder were all quite stable at the retest interval. We further found that different patterns of correlational relationships between cognitive deficits and positive and negative thought disorders were present in the manic and schizophrenic samples. When we conducted a cross-temporal analysis of our data, we found that no cognitive deficits in mania predicted the severity of positive thought disorder over time, although the severity of thought disorder predicted distraction performance over time. In the schizophrenic subjects, distraction performance, but not reality monitoring, exerted a significant cross-temporal influence on positive thought disorder.

Adult↗
PubMed1997

Reaching movements: concurrency of continuous and discrete programming.

The present study was undertaken to investigate further how human subjects prepare default parameters of reaching movements. Two qualitatively different modes for setting default values of direction are possible (continuous and discrete mode) and there is a threshold visual target separation for continuous or discrete programming. The most prominent finding is that the continuous and discrete modes of programming can be used concurrently.

Adult↗
PubMed2004

The fan effect in fMRI: left hemisphere specialization in verbal working memory.

We studied the fan effect of verbal working memory using functional magnetic resonance imaging (fMRI). Participants were presented with a sentence-pair matching task that described semantic relationships (e.g. classroom-school). Working memory load and semantic processing were manipulated by increasing the number of sentences to be remembered and varying whether they matched expectation. Increased working memory load elicited activation in left dorsal frontal and left inferior parietal regions, and also delayed the hemodynamic responses. Convergent results from semantic matches occurred in the left parietal lobe, whereas, left ventral frontal activation from mismatches diverged from working memory results. The findings were consistent with behavioural and electrophysiological evidence, with the fan effect in fMRI providing novel insight into the spatiotemporal nature of verbal working memory in the left hemisphere.

Adult↗
PubMed1995

The temporal-distance effect in subjects with dementia of the Alzheimer type.

The efficacy of temporal-distance processing for spatial locations was evaluated in college students, elderly controls, and subjects with mild and moderate dementia of the Alzheimer type (DAT). The elderly controls showed a slightly lower level of performance than college students, but both elderly controls and college students displayed a temporal-distance effect. The mild DAT subjects performed the task accurately only at the greatest temporal distances. The moderate DAT subjects performed at chance levels for all distances. Because similar changes in the temporal-distance function have been described for humans and animals with small hippocampal or prefrontal cortex damage, there might be important hippocampal or prefrontal cortex involvement or both in early stages of Alzheimer disease.

Adult↗
PubMed1988

Evidence of echoic memory with a multichannel cochlear prosthesis.

Short-term memory was examined in a subject with a multichannel cochlear prosthesis. Serial recall for lists of digits revealed what are widely regarded as the principal hallmarks of echoic memory, namely the recency effect and the suffix effect. Thus, probability of recall increased for the last one or two digits, except when a nominally irrelevant but spoken item was appended to the to-be-remembered list. It appears, therefore, that a multichannel cochlear implant can give rise to not only the perception of, but also an echoic memory for, speech. As with normal subjects, the suffix effect did not occur with a nonspeech suffix, implying that the echoic memory from the prosthesis shows normal sensitivity to the distinction between speech and nonspeech.

Adult↗
PubMedDate not supplied

Influence of a brief aerobic training program on heart rate and subjective response to a psychologic stressor.

An experiment was conducted to determine whether a brief program of aerobic exercise would reduce the heart rate and subjective responses of high- and low-fit subjects to a psychologic stressor. Thirty-four high-fit and 34 low-fit subjects were exposed to a moderate stressor (recall of digits backwards test) while their heart rates and subjective responses were monitored. Approximately half of the high- and low-fit subjects then participated in a 13-week aerobic exercise training program, whereas the other subjects did not. After the 13-week period, the subjects were again exposed to the stressor. Results indicated that a) in the pretest the low-fit subjects showed a greater heart rate response to the stressor than the high-fit subjects, b) the training program was effective for increasing subjects' levels of aerobic fitness, and c) the training program was effective for reducing the heart rate response to the stressor of low-fit subjects. These findings provide support for the relationship between fitness and the response to psychologic stressors and they suggest that aerobic training may be an effective way of helping low-fit persons deal with psychologic stressors.

Adolescent↗
PubMed1999

The effect of repeated nicotine administration on the performance of drug-naive rats in a five-choice serial reaction time task.

Nicotine improves cognitive performance both in animals and in humans, particularly in tests involving attentional processes. The five-choice serial reaction time task (5-CSRTT) is widely used as a model of attentional performance in rats, and previous studies have demonstrated effects of nicotine in this task on measures such as improved reaction time. Using a modified version of this task (in which rats were required to respond to the disappearance of one of five stimulus lights), we evaluated the effects of repeated nicotine administration (0.3 mg/kg, intraperitoneally, on three occasions over 7 days) in drug-naive rats. After the first administration, nicotine increased accuracy and reduced inappropriate responding (anticipatory responses and responses during time-out) compared to performance following vehicle administration on the preceding day. However, with repeated administration the improvement in accuracy disappeared, and other effects became apparent. Thus, after the third administration the main effects of nicotine were to increase inappropriate responding and to reduce reaction times. A fourth administration 1-2 weeks later produced similar results to the third administration, suggesting that the effects of nicotine were now constant. Despite the general increase in inappropriate responding, there was no impairment in accuracy. In contrast to the response to repeated nicotine, the performance of the rats on the 3 vehicle days remained constant. These data demonstrate that the administration of nicotine to drug-naive subjects improves performance in the 5-CSRTT but that with repeated administration this effect disappears and is replaced by a profile in which inappropriate and impulsive responding predominate.

Animals↗
PubMed2003

A Canadian multicenter trial assessing memory and executive functions in patients with schizophrenia spectrum disorders treated with olanzapine.

Serial verbal learning task (explicit long-term memory) and verbal fluency (generation of a response) are tests that are usually severely impaired in schizophrenia. Despite the growing literature supporting the clinical efficacy of olanzapine, psychiatrists still question its cognitive consequences. This study assessed the efficacy of olanzapine on neurocognitive functioning. Patients (N = 134) meeting diagnostic criteria for schizophrenia, schizophreniform, or schizoaffective disorders began an 8-week, open-label olanzapine treatment at a dose of 5 mg/d, which was increased to 10 mg/d after 1 week. Daily dosage was subsequently adjusted between 5 and 20 mg/d based on individual clinical status. All previous antipsychotics were tapered and discontinued during the first 2 weeks of the study. Neuropsychologic assessments were carried out at baseline and at 4 and 8 weeks. Explicit long-term memory was assessed with the Rey Auditory-Verbal Learning Test: the average immediate recall score significantly improved (P < 0.001), as did the delayed recall score (P < 0.001). The average total score on category fluency improved from 34.6 words at baseline to 37.6 words at end point (P < 0.0001). Time on both Trail A and B making tasks significantly decreased (P < 0.0001). Lack of a control arm makes it impossible to exclude a practice effect as an explanation for the enhanced cognitive performance, although the Word List Recall test represents one of the better resources to avoid a practice effect. After switching to olanzapine, there was a statistically significant improvement of cognitive function in the 3 main domains tested and no significant worsening of any memory or executive function measure.

Acoustic Stimulation↗
PubMedDate not supplied

The relationship between blood pressure and cognitive performance in the Third National Health and Nutrition Examination Survey (NHANES III).

OBJECTIVE: The present study examined the relationship between blood pressure and cognitive performance in 2727 healthy men and women between the ages of 20 and 59 years who participated in the Third National Health and Nutrition Examination Survey (NHANES III). METHODS: Participants were selected from a subsample of 5662 NHANES III respondents who completed an initial home interview, a medical examination, and a series of computerized cognitive tests of visuomotor reaction time, complex psychomotor speed (ie, symbol digit substitution), and verbal learning/attention (ie, serial digit learning). RESULTS: Hierarchical regressions tested the contribution of resting blood pressure to the prediction of performance on each of the cognitive tests. Results indicated that, after controlling for demographic variables (age, sex, race/ethnicity, education) and resting blood pressure, the interaction of systolic blood pressure by age was a significant predictor of performance on the test of verbal learning/attention. Follow-up analyses revealed that higher systolic blood pressure was associated with poorer performance in those younger than 40 years. CONCLUSIONS: Expanding on findings from previous epidemiological studies, the present study reports a small but significant relationship between resting blood pressure and cognitive performance that is particularly evident in younger healthy adults.

Adult↗
PubMedDate not supplied

Word list versus story memory in Alzheimer disease and frontotemporal dementia.

Memory impairment, characterized by a pattern of rapid forgetting, is the hallmark deficit in Alzheimer's disease (AD). Memory deficits have also been reported in frontotemporal dementia (FTD), and are thought to reflect diminished organizational and attentional abilities leading to a pattern of decreased acquisition of new information. The present study compared patients with AD, the behavioral variant of FTD, and cognitively intact elderly control subjects on two types of memory tests: story memory and word list recall. The percent of information recalled immediately (encoded), after a delay, and the percent retention between these conditions was calculated for both tests. The results showed that FTD patients encoded and recalled more information from the story than AD patients. No difference was found between FTD and AD patients for encoding of the word list. However, FTD patients recalled more words after a delay than AD patients. Percent retention on both tasks was also greater for the FTD group. The results suggest that patterns of performance on different tests of memory, and, in particular, measures of retention, can be useful in differentiating memory impairment in AD from that of FTD on cognitive testing.

Aged↗
PubMed2001

Visual prior entry.

It has long been claimed that attended stimuli are perceived prior to unattended stimuli--doctrine of prior entry. Most, if not all, studies on which such claims have been based, however, are open to a nonattentional interpretation involving response bias, leading some researchers to assert that prior entry may not exist. Given this controversy, we introduce a novel methodology to minimize the effect of response bias by manipulating attention and response demands in orthogonal dimensions. Attention was oriented to the left or right (ie., spatially), but instead of reporting on the basis of location, observers reported the order (first or second) of vertical versus horizontal line segments. Although second-order response biases were demonstrated, effects of attention in accordance with the law of prior entry were clearly obtained following both exogenous and endogenous attentional cuing.

Adult↗