Biomedical subjects

Louis Bherer

Publications and source records attributed to Louis Bherer.

12 recordsLinked to original sources

PubMed2006

Testing the limits of cognitive plasticity in older adults: application to attentional control.

Laboratory based training studies suggest that older adults can benefit from training in tasks that tap control aspects of attention. This was further explored in the present study in which older and younger adults completed an adaptive and individualized dual-task training program. The testing-the-limits approach was used [Lindenberger, U., & Baltes, P. B. (1995). Testing-the-limits and experimental simulation: Two methods to explicate the role of learning in development. Human Development, 38, 349-360.] in order to gain insight into how attentional control can be improved in older adults. Results indicated substantial improvement in overlapping task performance in both younger and older participants suggesting the availability of cognitive plasticity in both age groups. Improvement was equivalent among age groups in response speed and performance variability but larger in response accuracy for older adults. The results suggest that time-sharing skills can be substantially improved in older adults.

Adult↗

PubMed2006

Training-induced plasticity in older adults: effects of training on hemispheric asymmetry.

The extent to which cortical plasticity is retained in old age remains an understudied question, despite large social and scientific implications of such a result. Neuroimaging research reports individual differences in age-related activation, thereby educing speculation that some degree of plasticity may remain throughout life. We conducted a randomized longitudinal dual-task training study to investigate if performance improvements (a) change the magnitude or pattern of fMRI activation, thereby suggesting some plasticity retention in old age and (b) result in a reduction in asymmetry and an increase in age differences in fMRI activation as a compensatory model of performance-related activation predicts. Performance improvements were correlated with an increase in hemispheric asymmetry and a reduction in age differences in ventral and dorsal prefrontal activation. These results provide evidence for plasticity in old age and are discussed in relation to an alternative argument for the role of reduced asymmetry in performance improvements.

Adaptation, Physiological↗

PubMed2006

Training-induced functional activation changes in dual-task processing: an FMRI study.

Although training-induced changes in brain activity have been previously examined, plasticity associated with executive functions remains understudied. In this study, we examined training-related changes in cortical activity during a dual task requiring executive control. Two functional magnetic resonance imaging (fMRI) sessions, one before training and one after training, were performed on both a control group and a training group. Using a region-of-interest analysis, we examined Time x Group and Time x Group x Condition interactions to isolate training-dependent changes in activation. We found that most regions involved in dual-task processing before training showed reductions in activation after training. Many of the decreases in activation were correlated with improved performance on the task. We also found an area in the dorsolateral prefrontal cortex that showed an increase in activation for the training group for the dual-task condition, which was also correlated with improved performance. These results are discussed in relation to the efficacy of training protocols for modulating attention and executive functions, dual-task processing, and fMRI correlates of plasticity.

Adult↗

PubMed2005

Neural correlates of dual-task performance after minimizing task-preparation.

Previous dual-task neuroimaging studies have not discriminated between brain regions involved in preparing to make more than one response from those involved in the management and execution of two tasks. To isolate the effects of dual-task processing while minimizing effects related to task-preparatory processes, we employed a blocked event-related design in which single trials and dual trials were randomly and unpredictably intermixed for one block (mixed block) and presented in isolation of one another during other blocks (pure blocks). Any differences between dual-task and single-task trials within the mixed block would be related to dual-task performance while minimizing any effects related to preparatory differences between the conditions. For this comparison, we found dual-task-related activation throughout inferior prefrontal, temporal, extrastriate, and parietal cortices and the basal ganglia. In addition, when comparing the single task within the mixed block with the single task presented in the pure block of trials, the regions involved in processes important in the mixed block yet unrelated to dual-task operations could be specified. In this comparison, we report a pattern of activation in right inferior prefrontal and superior parietal cortices. Our results argue that a variety of neural regions remain active during dual-task performance even after minimizing task-preparatory processes, but some regions implicated in dual-task performance in previous studies may have been due to task-preparation processes. Furthermore, our results suggest that dual-task operations activate the same brain areas as the single tasks, but to a greater magnitude than the single tasks. These results are discussed in relation to current conceptions of the neural correlates of dual-task performance.

Adult↗

PubMed2005

Training effects on dual-task performance: are there age-related differences in plasticity of attentional control?

A number of studies have suggested that attentional control skills required to perform 2 tasks concurrently become impaired with age (A. A. Hartley, 1992; J. M. McDowd & R. J. Shaw, 2000). A. A. Hartley (2001) recently observed that the age-related differences in dual-task performance were larger when the 2 tasks required similar motor responses. The present study examined the extent to which age-related deficits in dual-task performance or time sharing--in particular, dual-task performance of 2 discrimination tasks with similar motor requirements--can be moderated by training. The results indicate that, even when the 2 tasks required similar motor responses, both older and younger adults could learn to perform the tasks faster and more accurately. Moreover, the improvement in performance generalized to new task combinations involving new stimuli. Therefore, it appears that training can substantially improve dual-task processing skills in older adults.

Adult↗

PubMed2005

Study of verbal working memory in patients with Parkinson's disease.

The authors examined the nature of the working memory deficit in persons with Parkinson's disease (PD). Three hypotheses were tested: a limited storage capacity, an impaired executive component, and a reduction of psychomotor speed. Verbal working memory was assessed in 14 PD patients without dementia and 14 matched control participants. Participants were administered a classical verbal span test, working memory tasks that required either updating or manipulation capacities, and motor and psychomotor speed tasks. Patients' performance was comparable to that of control participants on the verbal span test. However, results on the working memory tasks indicated a deficit in manipulation with normal updating capacities. Motor and psychomotor slowing were found in the patient group, but slowing could not fully account for the impairment observed in the manipulation task. Results indicated that there is a genuine but selective working memory impairment in patients with PD.

Age Factors↗

PubMed2005

[Impact on physical fitness on cognitive aging].

Cognitive vitality is one of the determining factors of autonomy in the elderly. Aging is often accompanied by important changes in the central nervous system, which may lead to cognitive decline. Several factors seem however to modulate the effect of aging on cognition. For instance, older adults who engage in regular physical activity have better performances in tests implying decision-making process, memory and problems solving. This article draws up a portrait of normal aging while being interested in the impact of the physical fitness on cognition in the elderly. Although further researches are needed to elucidate the mechanisms by which physical fitness enhance cognition in old age, recent studies have shown that improving physical fitness leads to better performances in tasks assessing a diversity of cognitive domains. Moreover, the impact of physical fitness appears to be heterogeneous, being of greater amplitude in tasks that tap executive functions. It thus seems that physical training could serve to enhance and maintain cognitive vitality in older adults.

Aged↗

PubMed2004

Quantification judgement in high functioning autism: superior or different?

This study examined the hypothesis of superior quantification abilities of persons with high functioning autism (HFA). Fourteen HFA individuals (mean age: 15 years) individually matched with 14 typically developing (TD) participants (gender, chronological age, full-scale IQ) were asked to quantify as accurately and quickly as possible numerosities, represented by the number of squares (2-9) presented in random configurations. In addition, the visual angles of stimuli presentation were manipulated in order to induce a local (large visual angle) and a global (small visual angle) bias on participants' quantification performance (accuracy and naming time). Findings revealed no effect of local and global bias of stimuli presentation in the two groups' performance, and no superior quantification abilities in HFA participants. However, analyses of the naming time slopes for identification by HFA participants of small consecutive numerosities (2-5), suggested their use of counting processes instead of subitizing (or immediate apprehension of numerosities) as in TD participants. Possible explanations for these results are discussed with reference to models of locally-oriented information processing in autism.

Adolescent↗

PubMed2004

Environmental influences on cognitive and brain plasticity during aging.

In the current article, we provide a critical review of the extant literature that has focused on environmental influences on cognitive and brain plasticity over the adult life span. The review includes both human epidemiological, and human and nonhuman cross-sectional and longitudinal research. We review a number of factors that have been suggested to reduce age-related cognitive decline including both formal and informal education, leisure pursuits, intellectual engagement, and expertise in different skill domains. We also examine the literature on cognitive and physical fitness training. We conclude with a discussion of the gaps in the literature and suggestions for future research.

Adult↗

PubMed2004

Age-related differences in response preparation: the role of time uncertainty.

This study explored the ability of younger and older participants to use a variable preparatory interval (PI) to enhance reaction time (RT) performance. In Experiment 1, 30 seniors and 15 young adults completed simple and choice RT tasks with short and long variable PIs. RT decreased with increasing PI duration in both younger and older adults, but the PI effect was larger in elderly individuals. The results of Experiment 2 (20 seniors and 20 young adults) showed an equivalent preparatory effect in older and younger adults when the probability of the shortest PI was increased. These findings suggest that older adults do not prepare as well as younger adults for unlikely events and that time uncertainty affects age-related differences in response preparation.

Adult↗

PubMed2004

[Executive function deficits in normal aging, Alzheimer's disease, and frontotemporal dementia].

An increasing number of studies suggest that executive functions are among the first cognitive functions to bear negative effects of normal aging. Executive functions also appear to be early affected in Alzheimer's disease and frontotemporal dementia. This article reviews studies in neuropsychology and experimental cognitive psychology with a focus on normal aging, Alzheimer's disease as well as frontotemporal dementia. Study results suggest that so called executive tasks are not equally impaired by normal ageing or dementia in agreement with the recent theoretical models, which state that a set of distinct elementary mechanisms subserve the executive control of cognitive behavior. These models are therefore particularly relevant to address issues stemming from aging.

Aged↗

PubMed2003

Temporal preparation strategy may inflate RT deficit in patients with Parkinson's disease.

Twelve patients with Parkinson's disease (PD) and 12 age-matched controls completed a visual reaction time (RT) task to assess the effect of temporal parameters on response preparation. Simple and choice RT conditions were presented in separate blocks. In both conditions, preparatory intervals of various durations (1, 3 and 5 s) were introduced between an auditory warning signal and the visual target. Within a block of trials, intervals varied randomly. The results indicated that PD patients responded slower than controls in both task conditions. Also, there was evidence for preparation in both groups, as RT decreased with increasing intervals. A three-way interaction indicated that PD patients' RT was longer than that of controls at the shortest interval in simple RT. This suggests that PD patients show a different pattern of temporal response preparation and that this may contribute to their deficit on RT tasks.

Acoustic Stimulation↗