Biomedical subjects

Donald T Stuss

Publications and source records attributed to Donald T Stuss.

14 recordsLinked to original sources

PubMed2004

Development of orbitofrontal function: current themes and future directions.

In recent years, an exciting thrust in the developmental research literature has been the focus on "executive" functions (EF). However, the emphasis has been on the more purely cognitive aspects of EF operative in abstract reasoning and problem solving-aspects associated mainly with dorsolateral frontal regions. Although the literature on adult neuropsychology has seen an emerging and growing interest in the study of processes more related to orbitofrontal cortex (OFC), including emotion and personality, research on the development of EF has lagged behind. This special issue of Brain and Cognition is intended to redress this imbalance by bringing together researchers who are studying the nature and development of orbitofrontal function from a wide variety of perspectives.

Affect↗

PubMed2004

The frontal lobes and theory of mind: developmental concepts from adult focal lesion research.

The primary objective in this paper is to present a framework to understand the structure of consciousness. We argue that consciousness has been difficult to define because there are different kinds of consciousness, hierarchically organized, which need to be differentiated. Our framework is based on evidence from adult focal lesion research. The different types of consciousness are associated with distinct brain regions, with the higher levels of consciousness related to self-awareness and theory of mind (both facets of consciousness), with an emphasis on the role of the frontal lobes. The secondary objective is to use this structure to suggest hypotheses about the potential effect of frontal dysfunction at various developmental stages, and including both congenital and acquired brain injury.

Adult↗

PubMed2004

Acute predictors of real-world outcomes following traumatic brain injury: a prospective study.

PRIMARY OBJECTIVE: To determine whether the recovery of acute attention and memory improves the prediction of real-world outcomes over that provided by standard demographic and injury-severity measures. RESEARCH DESIGN: Participants were recruited consecutively at the time of injury and followed prospectively at 1 (time 1, or T1) and 4 years (time 2, or T2). METHODS AND PROCEDURES: Measures of attention and memory and the Galveston Orientation and Amnesia Test (GOAT) were administered to 94 participants daily from the time of injury until the criterion was met. Sixty-three per cent returned at T1 and 53% returned at T2. Outcomes were psychosocial distress, return to work and/or school, and quality of life. MAIN OUTCOMES AND RESULTS: Recovery of attention, memory and orientation did not significantly improve prediction of outcomes at T1, but did so at T2. At T2, recovery of free recall of three words over 24 h was a more sensitive predictor of psychosocial distress and return to productivity than the GOAT. CONCLUSIONS: Free recall of three words may be a useful acute clinical test to enhance prediction of long-term outcomes.

Adolescent↗

PubMed2003

Staying on the job: the frontal lobes control individual performance variability.

The causes of variability of performance by individual subjects have rarely been investigated, although excessive variability or inconsistency may be a functionally significant factor for many real-life activities. Our objective was to determine whether patients with focal frontal brain lesions have excessive individual performance variability. Thirty-six patients with focal frontal (n=25) or non-frontal (n=11) lesions were compared with 12 control subjects on different measures of intra-individual variability: dispersion within a testing session; and consistency across testing sessions. Four reaction time tasks, varying in levels of complexity and based on a model of detection using feature integration, were administered. Following the first test session, 22 patients and 10 controls returned for two subsequent test sessions, which permitted the assessment of consistency of performance. Measures of abnormal dispersion of performance on these tests were observed in frontal patients only (except those with exclusively inferior medial damage). Disturbances in consistency of performance were observed primarily in patients with frontal lesions. Damage to the frontal lobes impairs the stability of cognitive performance. Damage to different frontal regions causes different profiles of abnormal variability. Fluctuations in performance of a task may underlie some of the reported difficulties in daily tasks reported by patients with frontal injuries.

Adult↗

PubMed2003

The effects of normal aging on humor appreciation.

The importance of humor in healthy aging is being recognized. We compared elderly and young participants on their comprehension and appreciation of, and reaction to, verbal and nonverbal humor tests. Cognitive processes-working memory, cognitive flexibility, verbal abstraction, and visual scanning-were studied in relation to humor. Results indicated a relative deficit in the elderly in the cognitive comprehension of humor-selecting punch lines to jokes and in a cartoon array test. Measures of cognitive function correlated with humor comprehension. In contrast to this deficit in comprehension, the elderly showed intact affective appreciation and emotional reactiveness. Because of the hypothesis of frontal lobe degeneration as a basis for changes with aging, we compared the elderly to patients with focal frontal lesions. In this comparison, the elderly were significantly better than the patients in their comprehension of humor. They also displayed intact appreciation of humor compared to patients with frontal lesions. This preliminary study suggests that preserved affective responsiveness may underlie the success in using humor as a coping mechanism in the elderly.

Adolescent↗

PubMed2002

MEG study of long-term cortical reorganization of sensorimotor areas with respect to using chopsticks.

The movements required to use chopsticks are overlearned and routine in Asians. Most non-Asians, on the other hand, typically have difficulty performing this unfamiliar manual activity, and have to focus their attention on the movements required to use chopsticks adequately. Using magnetoencephalography (MEG) we compared the cortical activation of highly trained Asian chopstick users to the activation of Europeans who only occasionally used chopsticks, while they performed the same tasks with chopsticks or a control task of simple tapping of the same fingers. The data were analyzed using the new method of synthetic aperture magnetometry (SAM). In Europeans there was a significantly higher ratio of spectral power in the higher gamma frequency band (60-80 Hz) over the sensorimotor area compared to the Asian subjects. From these results we conclude that the high gamma band activity in the sensorimotor area may reflect focused attention and functional reorganization of the cortical network with respect to sensorimotor experience.

Adult↗

PubMed2002

Lapses of intention and performance variability reveal age-related increases in fluctuations of executive control.

We examine the hypothesis that the efficiency of executive control processes is less stable over time in older than younger adults. An age-related decrease in the efficiency of executive control should result in an increase in performance variability in task conditions requiring the recruitment of executive control processes and not in task conditions requiring minimal involvement of executive control. Performance variability was similar for younger and older adults in task conditions requiring minimal executive control and greater for older than younger adults in task conditions requiring executive control. These and other data are consistent with the proposal that aging is associated with a decrease in the stability of executive control over time.

Adult↗

PubMed2002

Effects of divided attention on episodic memory in chronic traumatic brain injury: a function of severity and strategy.

Eleven patients with mild traumatic brain injury (MTBI) and 13 patients with moderate-to-severe TBI (STBI) were compared to 10 matched controls on episodic memory for pictorial scene-object associations (e.g. kitchen-bread) and a range of standardized neuropsychological tests of memory and frontal-lobe functions. We tested the hypothesis that deficits in episodic memory result from impaired attentional resources and/or strategic control by manipulating attentional load at encoding (focused versus divided attention) and environmental support at retrieval (free recall and recalled cued by scene versus recognition of object and scene). Patients with TBI were disproportionately affected by the divided attention manipulation, but this effect was modulated by injury severity and encoding strategy. Overall, MTBI patients were impaired only when items were encoded under divided attention, indicating memory deficits that were secondary to deficits in the executive control. STBI patients could be differentiated into two distinct functional subgroups based on whether they favored a strategy of attending to the encoding or digit-monitoring task. The subgroup favoring the digit-monitoring task demonstrated deficits in the focused attention condition, and disproportionate memory deficits in the divided attention condition. In contrast, the subgroup favoring the encoding task demonstrated intact performance across all memory measures, regardless of attentional load, and despite remarkable similarity to the other STBI subgroup on demographic, neuropsychological, and acute injury severity measures. We discuss these outcome differences in terms of the relationship between strategy and executive control and highlight the need for more sensitive anatomical and behavioral measurement at both acute and chronic stages of injury.

Adult↗

PubMed2002

Dissociations within the anterior attentional system: effects of task complexity and irrelevant information on reaction time speed and accuracy.

Patients with focal frontal or nonfrontal lesions were compared with control participants on 4 reaction time (RT) tasks varying in levels of complexity based on a feature-integration model of detection. Superior medial lesions affected simple RT speed. Increasing the demands of feature detection did not differentially affect speed of correct responses among the groups. Frontal structures appear to play little role in correct integration of features during detection. The analysis of error types within the complex task revealed a frontal lobe hemispheric distinction between sensitivity and bias: right dorsolateral-decreased sensitivity; left dorsolateral-altered response bias. The frontal lobes, particularly right dorsolateral, were required to inhibit an incorrect response. There are at least 3 functionally and anatomically separable anterior attentional processes.

Adult↗

PubMed2002

Effects of time of day on age differences in working memory.

This study investigated the hypothesis that the influence of time of day on the efficiency of working memory is greater for older than younger adults. Groups of younger and older adults performed a working memory task on 4 consecutive days, twice in the morning and twice in the evening. Objective (body temperature) and subjective (alertness ratings) measures of arousal were taken during each session. Temperature increased across the day equally for younger and older adults, whereas alertness ratings were higher in the morning for older adults and in the evening for younger adults. The efficiency of the access and deletion functions paralleled the subjective alertness rating for younger and older adults, and age-related differences in these functions were greater when individuals were tested at nonoptimal times of day. The efficiency of the response inhibition function was similar for younger and older adults and paralleled changes in body temperature.

Adult↗

PubMed2002

A comparison of independent living outcomes following traumatic brain injury and spinal cord injury.

This study compares independent living outcomes in persons with traumatic brain injury (TBI) and spinal cord injury (SCI). Both injuries represent life-altering events that are known to have a negative impact on independent living and are predominantly experienced by members of the same demographic group. However, the types of resultant impairments and disabilities experienced by the two populations differ substantially. The TBI participants were recruited consecutively from Canada's largest tertiary care trauma centre and followed prospectively for four years. The SCI participants were recruited via a mailed survey to members of a provincial branch of the Canadian Paraplegic Association. Independent living outcomes were measured using DeJong and Hughes' (1982) classification system of productivity status, the Reintegration to Normal Living Index, and questions on assistance from environmental supports in the form of wheelchair use and paid/unpaid personal assistance. The TBI group was found to be significantly more productive, have higher levels of satisfaction with their current experience of community integration, and use fewer environmental supports than their SCI counterparts (P<or=0.0001). Methodological and demographic differences between the samples are discussed in relation to the results. The results suggest that various aspects of independent living in these two defined groups (TBI and SCI) although highly related require specific attention and that clinicians and researchers working with TBI and SCI might benefit from further collaborative efforts.

Activities of Daily Living↗

PubMed2002

Adult clinical neuropsychology: lessons from studies of the frontal lobes.

Clinical neuropsychologists have adopted numerous (and sometimes conflicting) approaches to the assessment of brain-behavior relationships. We review the historical development of these approaches and we advocate an approach to clinical neuropsychology that is informed by recent findings from cognitive neuroscience. Clinical assessment of executive and emotional processes associated with the frontal lobes of the human brain has yet to incorporate the numerous experimental neuroscience findings on this topic. We review both standard and newer techniques for assessment of frontal lobe functions, including control operations involved in language, memory, attention, emotions, self-regulation, and social functioning. Clinical and experimental research has converged to indicate the fractionation of frontal subprocesses and the initial mapping of these subprocesses to discrete frontal regions. One anatomical distinction consistent in the literature is that between dorsal and ventral functions, which can be considered cognitive and affective, respectively. The frontal lobes, in particular the frontal poles, are involved in uniquely human capacities, including self-awareness and mental time travel.

Adult↗

PubMedDate not supplied

Remembering and knowing in patients with frontal lobe injuries.

Two experiments compared the performance of patients with pathology restricted to the prefrontal cortex to healthy controls on recognition tests that were followed by the remember/know procedure. Across both experiments, patients recognized roughly as many target items as control participants. Injuries centered in the frontal poles resulted in deficits that were selective to episodic remembering while apparently sparing semantic knowing. Patients with lesions restricted to dorsolateral prefrontal cortex were not impaired at either remembering or knowing. Results demonstrate a dissociation of cognitive function within the prefrontal cortex, and suggest that episodic remembering may share a family resemblance with other neurocognitive functions dependent upon polar aspects of the frontal lobes, such as self-recognition, anticipation, and planning.

Adult↗

PubMedDate not supplied

Role of the frontal lobes in implicit and explicit retrieval tasks.

While the role of the frontal lobes in explicit retrieval tasks is well supported, the findings for implicit tasks are less conclusive. We investigated the role of the frontal lobes in perceptual and conceptual implicit priming. Three memory paradigms were given under both implicit and explicit retrieval instructions, using word fragment completion, picture fragment completion and category exemplar generation. Three groups of individuals with frontal lesions were compared to normal controls: Left dorsolateral lesions (n = 5), right dorsolateral lesions (n = 4), and medial lesions (n = 9). Word fragment completion priming was impaired by left dorsolateral lesions, with other priming tests unaffected by any lesion. Explicit performance showed a different pattern, with category exemplar cued recall impaired by left dorsolateral and medial lesions. These findings support the role of the frontal lobes in both implicit and explicit retrieval mechanisms under certain conditions requiring strategy application or lexical retrieval.

Adult↗