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Biomedical subjects

Donald T Stuss

Publications and source records attributed to Donald T Stuss.

At least 19 recordsLinked to original sources
PubMed2007

Cognitive rehabilitation in the elderly: a randomized trial to evaluate a new protocol.

This study provides an introduction to, and overview of, several papers that resulted from a randomized control trial that evaluated a new cognitive rehabilitation protocol. The program was designed to improve general strategic abilities in ways that would be expressed in a broad range of functional domains. The trial, which was conducted on a sample of older adults who had experienced normal age-related cognitive decline, assessed performance in the following domains: memory, goal management, and psychosocial status. The general rationale for the trial, the overall experimental design, and the approach to statistical analyses that are relevant to each paper are described here. The results for each functional domain are reported in separate papers in this series.

Aged↗
PubMed2007

Cognitive rehabilitation in the elderly: effects on memory.

This study reports the effects of a 12-week multimodular cognitive rehabilitation training program on memory performance in two groups of older adults. In the Memory Training module, participants were instructed on the nature of memory and how to improve memory performance; internal and external strategies were described and practiced over the training sessions. Memory performance was assessed by four tests: Alpha Span, Brown-Peterson, Hopkins Verbal Learning Test - Revised (HVLT-R), and Logical Stories. One group received training on entry into the study (Early Training Group, ETG), the other after a 3-month delay (Late Training Group, LTG). The results showed no training-related improvement in working memory (Alpha Span), primary memory (Brown-Peterson, HVLT-R), or recognition memory (HVLT-R). While the most direct analyses of a training effect (analyses of covariance) rarely demonstrated significant effects, exploratory analyses provided some evidence for a training benefit in several measures of secondary memory (Logical Stories; HVLT-R) and strategic processing (Brown-Peterson; Logical Stories; HVLT-R). Positive results were largely restricted to the ETG, possibly because the LTG lost motivation as a consequence of their delayed training. The results need to be treated with caution, but are promising for the rehabilitation of memory functioning in older adults.

Aged↗
PubMed2007

Cognitive rehabilitation in the elderly: effects on strategic behavior in relation to goal management.

Executive functions are highly sensitive to the effects of aging and other conditions affecting frontal lobe function. Yet there are few validated interventions specifically designed to address executive functions, and, to our knowledge, none validated in a healthy aging sample. As part of a large-scale cognitive rehabilitation randomized trial in 49 healthy older adults, a modified Goal Management Training program was included to address the real-life deficits caused by executive dysfunction. This program emphasized periodic suspension of ongoing activity to establish goal hierarchies and monitor behavioral output. Tabletop simulated real-life tasks (SRLTs) were developed to measure the processes targeted by this intervention. Participants were randomized to two groups, one of which received the intervention immediately and the other of which was wait-listed prior to rehabilitation. Results indicated improvements in SRLT performance and self-rated executive deficits coinciding with the training in both groups. These gains were maintained at long-term follow-up. Future research will assess the specificity of these effects in patient groups.

Aged↗
PubMed2007

Cognitive rehabilitation in the elderly: an evaluation of psychosocial factors.

In this study, we report changes in psychosocial function in two groups of older adults that participated in the experimental trial of our cognitive rehabilitation program. The results, based on tests that measured a range of psychosocial attributes, showed that, following training, participants improved in terms of overall well-being, as well as in specific areas that included perceived happiness, coping strategies, and quality of life. An important finding was that improvements were also observed in long-term follow-up testing. Both groups benefited from training, but the effect was greater in the group that received training before undergoing a control procedure. The results, which show that the benefits of our rehabilitation program extend into the psychosocial domain, underscore the potentially important relationship between psychosocial factors and cognitive performance in older adults.

Adaptation, Psychological↗
PubMed2007

Cognitive rehabilitation in the elderly: overview and future directions.

This study provides an overview of the papers emanating from the experimental trial that evaluated a new cognitive rehabilitation program in older adults who were experiencing normal cognitive decline. The main features of the design are summarized, along with evidence that the training produced long-lasting improvement in memory performance, goal management, and psychosocial status. The benefits were attributed to several factors, including the program's emphasis on techniques that promoted efficient strategic processing. Limitations of the program and directions for future research are discussed.

Aged↗
PubMed2007

Executive function and coping at one-year post traumatic brain injury.

The purpose of this study was to examine the relationship between executive function and coping at one-year-post traumatic brain injury (TBI). TBI and matched control groups completed a coping questionnaire and a neuropsychological test series. In the TBI group, better executive performance was related to the use of problem focused coping (considered more adaptive). Conversely, lower executive performance was related to the use of emotion focused coping (considered more maladaptive). Planned hierarchical regression showed that executive function contributed significantly to the use of problem focused coping above and beyond pre-morbid intelligence and injury severity. Implications for cognitive rehabilitation are discussed.

Adaptation, Psychological↗
PubMed2007

Word-list-learning performance in younger and older adults: intra-individual performance variability and false memory.

We investigated the word-list-learning performance of younger and older adults over 4 consecutive days at different times of day to study age-related differences in consistency of performance over time and the influence of circadian variation on performance. Eighteen younger (M age, 23.4 years) and 18 older (M age, 73.3 years) men and women participated. The start time of testing alternated between morning and early evening across the 4 days of testing. On each test day, participants learned a different list of 15 unrelated words over four learning trials. As expected, younger adults performed better than older adults on immediate recall, delayed recall, and recognition. Contrary to our expectations, time of day did not significantly influence recall or recognition performance in either the older or younger adults. Older adults did show a greater incidence of false memory (i.e., previously learned list intrusions in free recall and false alarms in recognition) than younger adults. Older adults also exhibited greater intra-individual performance variability on the measures of false memory across test days. This variability was not related to circadian variation. False memory and variability of performance have both been linked to frontal systems dysfunction. The findings presented here are consistent with the notion that changes in cognition with aging in part reflect age-related decline in frontal lobe function.

Adult↗
PubMed2006

Effects of focal frontal lesions on response inhibition.

This study examined the performance of 38 normal subjects and 43 patients with focal lesions of the frontal lobes on a simple go-nogo task where the probability of the nogo stimulus was either 75% or 25%. Patients with lesions to the superior medial parts of the frontal lobes, in particular to the left superior portion of Brodmann area 6 (which includes the supplementary motor areas and the premotor areas for the right hand) had an increased number of false alarms (incorrect responses to the nogo stimulus). These results indicate that area 6 is specifically involved in the inhibition of response. Patients with lesions to the right anterior cingulate (areas 24 and 32) were slower and more variable in their reaction time. These findings could be explained by an inability to sustain stimulus-response contingencies. Lesions to the right ventrolateral prefrontal cortex (Brodmann areas 44, 45, 47) also increased the variability of response, perhaps by disrupting monitoring performance.

Brain Damage, Chronic↗
PubMed2006

Clustered functional MRI of overt speech production.

To investigate the neural network of overt speech production, event-related fMRI was performed in 9 young healthy adult volunteers. A clustered image acquisition technique was chosen to minimize speech-related movement artifacts. Functional images were acquired during the production of oral movements and of speech of increasing complexity (isolated vowel as well as monosyllabic and trisyllabic utterances). This imaging technique and behavioral task enabled depiction of the articulo-phonologic network of speech production from the supplementary motor area at the cranial end to the red nucleus at the caudal end. Speaking a single vowel and performing simple oral movements involved very similar activation of the cortical and subcortical motor systems. More complex, polysyllabic utterances were associated with additional activation in the bilateral cerebellum, reflecting increased demand on speech motor control, and additional activation in the bilateral temporal cortex, reflecting the stronger involvement of phonologic processing.

Acoustic Stimulation↗
PubMed2006

Mechanisms of spontaneous confabulations: a strategic retrieval account.

The 'temporality' hypothesis of confabulation posits that confabulations are true memories displaced in time, while the 'strategic retrieval' hypothesis suggests a general retrieval failure of which temporal confusion is a common symptom. Four confabulating patients with rupture of an anterior communicating artery (ACoA) aneurysm, eight non-confabulating ACoA controls and 16 normal controls participated in three experiments designed to test the two hypotheses. In Experiment 1, participants were tested on two continuous recognition tasks, one requiring temporal context distinctions, previously shown to be sensitive to confabulation and another that only requires content distinctions. Both manipulations were sensitive to confabulation, but not specific to it. Temporal context and content confusions (TCCs and CCs) can be explained as failures to make fine-grained distinctions within memory. In Experiment 2, free recall of semantic narratives that require strategic retrieval but are independent of temporal context was used to induce confabulations associated with remote memory, acquired before the onset of amnesia. Confabulators produced significantly more errors. Thus, when retrieval demands are equated, confabulations can be induced in the absence of temporal confusions. Only confabulators conflated semantic content from different remote semantic narratives and introduced idiosyncratic content, suggesting that qualitatively different mechanisms are responsible for distortions due to normal memory failure and for confabulation. Lesion analyses revealed that damage to ventromedial prefrontal cortex is sufficient for temporal context errors to occur, but additional orbitofrontal damage is crucial for spontaneous confabulation. In Experiment 3, we tested whether failure in memory monitoring is crucial for confabulation. Recognition of details from semantic and autobiographical narratives was used to minimize the initiation and search components of strategic retrieval. Only confabulators made more false alarms on both tasks, endorsed even highly implausible lures related to autobiographical events and were indiscriminately confident about their choices. These findings support a strategic retrieval account of confabulation of which monitoring is a critical component. Post-retrieval monitoring has at least two components: one is early, rapid and pre-conscious and the other is conscious and elaborate. Failure of at least the former is necessary and sufficient for confabulation. Other deficits, including TCC and CC, may be required for spontaneous confabulations to arise. The confluence of different sub-components of strategic retrieval would determine the content of confabulation and exacerbate its occurrence.

Aged↗
PubMed2006

Frontal lobes and attention: processes and networks, fractionation and integration.

The frontal lobes (FL), are they a general adaptive global capacity processor, or a series of fractionated processes? Our lesion studies focusing on attention have demonstrated impairments in distinct processes due to pathology in different frontal regions, implying fractionation of the "supervisory system." However, when task demands are manipulated, it becomes evident that the frontal lobes are not just a series of independent processes. Increased complexity of task demands elicits greater involvement of frontal regions along a fixed network related to a general activation process. For some task demands, one or more anatomically distinct frontal processes may be recruited. In other conditions, there is a bottom-up nonfrontal/frontal network, with impairment noted maximally for the lesser task demands in the nonfrontal automatic processing regions, and then as task demands change, increased involvement of different frontal (more "strategic") regions, until it appears all frontal regions are involved. With other measures, the network is top-down, with impairment in the measure first noted in the frontal region and then, with changing task demands, involving a posterior region. Adaptability is not just a property of FL, it is the fluid recruitment of different processes anywhere in the brain as required by the current task.

Attention↗
PubMed2006

Inhibitory control is slowed in patients with right superior medial frontal damage.

Inhibitory control is an essential part of behavior. Comprehensive knowledge of the neural underpinnings will shed light on complex behavior, its breakdown in neurological and psychological disorders, and current and future techniques for the pharmacological or structural remediation of disinhibition. This study investigated the neural mechanisms involved in rapid response inhibition. The stop signal task was used to estimate inhibitory speed in a group of neurologically normal control subjects and patients with discrete frontal lobe lesions. Task procedures were controlled to rule out probable confounds related to strategic changes in task effort. The findings indicate that the frontal lobes are necessary for inhibitory control and, furthermore, that the integrity of the right superior medial frontal region is key for rapid inhibitory control under conditions controlling for strategically slow responses, forcing reliance more on a rapid, "kill-switch" inhibitory system. These results are interpreted within an anatomical framework of corticospinal motor control.

Adult↗
PubMed2005

Genetics of vascular cognitive impairment: the opportunity and the challenges.

BACKGROUND AND PURPOSE: This review considers the current state of knowledge of genetic factors underlying vascular cognitive impairment (VCI). SUMMARY OF REVIEW: We argue here that genes conferring susceptibility to VCI must be of 2 nonmutually exclusive classes: (1) genes that confer susceptibility to cerebrovascular disease, and (2) genes that determine brain tissue responses to cerebrovascular disease (ie, render parenchymal tissue more or less susceptible to injury or able to repair itself after injury). Although some progress has been made in identifying genes of the first class, little has been done to explore genes of the second class. Evidence for the existence of such genes is presented. We discuss the advantages and disadvantages of different forms of cerebrovascular disease for studying these genes, and different study designs that might be used. CONCLUSIONS: The most critical challenge for genetic studies of VCI is to identify quantifiable phenotypes that can be reliably and effectively determined in large samples of subjects.

Brain↗
PubMed2005

Keeping time: effects of focal frontal lesions.

This study examined the performance of 32 normal subjects and 39 patients with focal lesions of the frontal lobes on two simple timing tasks-responding in time with a tone that regularly repeated at a rate of once every 1.5s, and then maintaining the same regular response rhythm without any external stimulus. The hypothesis was that lesions to the right prefrontal cortex would disrupt timing performance. The two main findings were (1) an abnormally high variability in the timing performance (both self-timed and tone-timed) of patients with lesions to the right lateral frontal lobe, particularly involving Brodmann area 45 and subjacent regions of the basal ganglia; (2) an increase in the variability of timing performance as the task continued in patients with lesions to the superior medial regions of the frontal lobe. These findings indicate that the right lateral frontal lobe is crucially involved in the ongoing control of timed behavior, either because of its role in generating time intervals or in monitoring the passage of these intervals. In contrast, the superior medial regions of the frontal lobe are necessary to maintain consistent timing performance over prolonged periods of time.

Acoustic Stimulation↗
PubMed2005

Multiple frontal systems controlling response speed.

This study evaluated a model of attention that postulates several distinct component processes, each mediated by specific neural systems in the human frontal lobes. A series of reaction time (RT) tests (simple, choice, and prepare) examined the hypothesis that different attentional processes are related to distinct regions within the frontal lobes. These tests were given to 38 patients with frontal lesions and 38 age-matched control subjects. Lesions were localized both by general regions (superior medial, inferior medial, left and right lateral) and by individual architectonic areas. Lesions in the superior medial (SM) frontal lobes, particularly involving areas 24 and 32 on the right, were associated with slow RT in all tests and with failure to decrease RT after a warning signal. Lesions in the right lateral (RL) frontal lobe, centred in area 9/46v, prevented the decrease in RT with increasing foreperiod that was seen in normal subjects and in patients with lesions elsewhere in the frontal lobes. The ability to energize a response for rapid RT, either generally or specifically following a warning stimulus, is sensitive to lesions of the right SM. Monitoring of stimulus occurrence and response behaviour in order to enhance the speed of response to upcoming stimuli is sensitive to RL lesions.

Adult↗