Search PubMed⌕ Search

Biomedical subjects

D T Stuss

Publications and source records attributed to D T Stuss.

At least 37 records · Page 2Linked to original sources
PubMed1999

Humour appreciation: a role of the right frontal lobe.

Humour occupies a special place in human social interactions. The brain regions and the potential psychological processes underlying humour appreciation were investigated by testing patients who had focal damage in various areas of the brain. A specific brain region, the right frontal lobe, most disrupted the ability to appreciate humour. The individuals with damage in this brain region also reacted less, with diminished physical or emotional responses (laughter, smiling). Performance on the humour appreciation tests used were correlated in a distinct pattern with tests assessing cognitive processes. The ability to hold information in mind (working memory) was related to both verbal (jokes) and non-verbal (cartoon) tests of humour appreciation. In addition, the demands of the specific type of humour test were related in a logical manner to cognitive processes, verbal humour being associated with verbal abstraction ability and mental shifting and cartoon humour being related to the abilities to focus attention to details and to visually search the environment. The ability of the right frontal lobe may be unique in integrating cognitive and affective information, an integration relevant for other complex human abilities, such as episodic memory and self-awareness.

Adolescent↗
PubMed1999

The acute period of recovery from traumatic brain injury: posttraumatic amnesia or posttraumatic confusional state?

OBJECT: The goal of this study was to characterize more fully the cognitive changes that occur during the period of acute recovery after traumatic brain injury (TBI). METHODS: The pattern of performance recovery on attention and memory tests was compared with the results of the Galveston Orientation and Amnesia Test (GOAT). Tests of memory and attention were administered serially to a hospitalized group of patients with TBI of varying severity. The tests differed in their level of complexity and/or requirement for more effortful or strategic processing. The authors found a regular pattern to recovery. As expected, ability to perform on simpler tests was recovered before performance on more effortful ones. The ability to recall three words freely after a 24-hour delay (the operational definition in this study of return to continuous memory) was recovered last, later than normal performance on the GOAT. Ability to perform simple attentional tasks was recovered before the less demanding memory task (recognition); ability to perform more complex attentional tasks was recovered before the free recall of three words after a 24-hour delay. This recovery of attention before memory was most notable and distinct in the group with mild TBI. CONCLUSIONS: The period of recovery after TBI, which is currently termed posttraumatic amnesia, appears to be primarily a confusional state and should be labeled as such. The authors propose a new definition for this acute recovery period and argue that the term posttraumatic confusional state should be used, because it more appropriately and completely characterizes the early period of recovery after TBI.

Adolescent↗
PubMed1998

The course of post-traumatic amnesia: three little words.

OBJECTIVE: To provide a simple means of "real time" recognition of emergence from post-traumatic amnesia (PTA). METHODS: Ninety-one patients with traumatic brain injury (PBI); 53 minor (GCS 13-15), 19 moderate (GCS 9-12), 18 severe (GCS 3-8). Twenty-seven control subjects treated at two regional trauma units for their acute phase and followed in a hospital-based research institute were studied prospectively. Subjects were examined repeatedly following injury with the Galveston Orientation and Amnesia Test (GOAT) and tests of their ability to learn and retain new information. Word triplets balanced for concreteness and frequency were presented. Immediate and 24-hour recall were tested. If 24-hour recall was imperfect, recognition was tested by presenting the 3 target words and 6 distracters. The target words were then re-presented and recall was tested the next day. The time intervals to first perfect recognition and first free perfect recall were compared with the patients' first GOAT score of 75 or greater on 2 successive days. Simple line drawings of common objects were also presented to the subjects using an identical paradigm. The outcome measures were GOAT, 3-word recognition and recall, 3 picture recognition and recall. RESULTS: For all categories of head injury severity, the median interval to perfect free recall of words followed the achievement GOAT criterion by a significant interval. The mean GOAT scores for perfect 3-word recall and recognition corresponding to minor, moderate and severe injuries were 97, 90 and 88, and 97, 76 and 68 respectively. The recognition and recall of pictures preceded the recognition and recall of words by approximately 1 day. CONCLUSIONS: The orientation measures of the GOAT that contain material that the patient knew prior to injury obscure the determination of recovery of continuous memory and should be tested separately. Three-word recall which is simpler to administer than the GOAT is a more reliable measure of emergence from PTA. For patients who are dysphasic or who do not share a common language with the examiner, 3-picture recognition and recall may substitute for word recognition and recall.

Adolescent↗
PubMed1998

Episodic memory and the self in a case of isolated retrograde amnesia.

Isolated retrograde amnesia is defined as impaired recollection of experiences pre-dating brain injury with relatively preserved anterograde learning and memory. We present findings from a patient (M.L.) with isolated retrograde amnesia following severe traumatic brain injury (TBI) that address hypotheses of the interrelationships of focal neuropathology, episodic memory and the self. M.L. is densely amnesic for experiences predating his injury, but shows normal anterograde memory performance on a variety of standard tests of recall and recognition. The cognitive processes underlying this performance were examined with the remember/know technique, which permits separation of episodic from non-episodic contributions to memory tests by quantifying subjects' reports of re-experiencing aspects of the encoding episode. The results demonstrated that M.L. does not episodically re-experience post-injury events to the same extent as control subjects, although he can use familiarity or other non-episodic processes to distinguish events he has experienced from those he has not experienced. M.L.'s MRI showed damage to the right ventral frontal cortex and underlying white matter, including the uncinate fasciculus, a frontotemporal band of fibres previously hypothesized to mediate retrieval of specific events from one's personal past. Recent functional neuroimaging evidence of an association between right frontal lobe functioning and episodic retrieval demands suggest that M.L.'s memory deficits are related to this focal injury. This hypothesis was supported by right frontal polar hypoactivation in M.L. in response to episodic retrieval demands when he was examined with a cognitive activation H2(15)O PET paradigm that reliably activated this frontal region in both healthy controls and patients with TBI carefully matched to M.L. (but without isolated retrograde amnesia). He also showed increased left inferomedial temporal activation relative to control subjects, suggesting that his spared anterograde memory is mediated through increased reliance on medial temporal lobe structures. Re-experiencing events as part of one's past is based on autonoetic awareness, i.e. awareness of oneself as a continuous entity across time. This form of awareness also supports the formulation of future goals and the implementation of a behavioural guidance system to achieve them. The findings from this study converge to suggest that M.L. has impaired autonoetic awareness attributable to right ventral frontal lobe injury, including right frontal-temporal disconnection. Reorganized brain systems mediate certain preserved cognitive operations in M.L., but without the normal complement of information concerning the self with respect to both past and future events.

Adult↗
PubMed1998

The effects of focal and diffuse brain damage on strategy application: evidence from focal lesions, traumatic brain injury and normal aging.

A new test of strategy application was designed to be relatively free of the constraints that limit the standard neuropsychological assessment of supervisory abilities. The validity of the test was assessed in 3 samples of participants with varying degrees of supervisory deficits and frontal systems dysfunction: focal frontal lesions, traumatic brain injury (TBI), and normal aging. Inefficient strategy application varied systematically across the 3 groups and was not due to extraneous factors such as forgetting the test instructions. Previous case studies have emphasized strategy application deficits in the face of normal neuropsychological test performance. In this study, it was shown that strategically impaired participants from a consecutive series can include those both with and without deficient neuropsychological test performance. When neuropsychological impairment was present, it was greatest on executive functioning tasks. Among participants with nonstrategic performance, there was evidence for a dissociation of knowledge from action. This finding was not specific to focal frontal lesions. A number of supervisory processes contributing to strategy application were identified. Exploratory analyses indicated differential effects of lesion location on these processes, especially inferior medial frontal and right hemisphere lesions. Overall, the results supported the use of unstructured tasks in the assessment of supervisory abilities.

Adolescent↗
PubMed1998

The effects of focal anterior and posterior brain lesions on verbal fluency.

Seventy-four patients with focal brain lesions were compared to a neurologically normal control group on tasks of letter-based and category-based list generation. When patients were divided only by right frontal, left frontal, or nonfrontal lesion sites, the pattern of fluency impairments confirmed prior claims. When more precise lesion sites within the frontal lobes were compared between groups classified based on their fluency performance, much more specific brain-behavior relations were uncovered. Damage to the right dorsolateral cortical or connecting striatal regions, the right posterior area, or the medial inferior frontal lobe of either hemisphere did not significantly affect letter-based fluency performance. Superior medial frontal damage, right or left, resulted in moderate impairment. Patients with left dorsolateral and/or striatal lesions were most impaired. Left parietal damage led to performance relatively equivalent to the superior medial and left dorsolateral groups. The same lesion sites produced impairments in category based fluency, but so did lesions of right dorsolateral and inferior medial regions. Task analysis and correlations with other measures revealed that different cognitive processes related to different brain regions underlie performance on verbal fluency tests.

Adult↗
PubMed1997

Effects of aging on conditional associative learning: process analyses and comparison with focal frontal lesions.

Conditional associative learning (CAL), a measure validated in studies of frontal lesions, was used to evaluate the hypothesis that age-related cognitive decline is related to frontal dysfunction. Older adults and focal frontal participants showed impaired CAL performance, but the deficit was greater in the latter group, where it was specific to participants with dorsolateral prefrontal cortical (DLPFC) lesions. The deficits were attributable to strategic rather than basic associative processes. Error scores described ways in which past information failed to guide behavior, and they were related to lesion location. Congruence between older adults and DLPFC participants on a measure of defective inhibition suggests that age-related decline in inhibitory processes is due to DLPFC dysfunction.

Adolescent↗
PubMed1997

Toward a theory of episodic memory: the frontal lobes and autonoetic consciousness.

Adult humans are capable of remembering prior events by mentally traveling back in time to re-experience those events. In this review, the authors discuss this and other related capabilities, considering evidence from such diverse sources as brain imaging, neuropsychological experiments, clinical observations, and developmental psychology. The evidence supports a preliminary theory of episodic remembering, which holds that the prefrontal cortex plays a critical, supervisory role in empowering healthy adults with autonoetic consciousness-the capacity to mentally represent and become aware of subjective experiences in the past, present, and future. When a rememberer mentally travels back in subjective time to re-experience his or her personal past, the result is an act of retrieval from episodic memory.

Adult↗
PubMed1997

Chronic obstructive pulmonary disease: effects of hypoxia on neurological and neuropsychological measures.

Eighteen patients with chronic obstructive pulmonary disease (COPD) were administered a series of pulmonary, neurological, and neuropsychological measures to test if there was an effect of COPD on neurological and cognitive functioning. Overall, there was no evidence of general dementia in this sample. Measures of immediate and delayed memory, complex attention, and speed of information processing correlated highly with arterial carbon dioxide partial pressure and, to a lesser extent, with oxygen partial pressure. Measures of language abilities, perceptual-motor functioning, and simple attention generally were not related to arterial gas pressures. A similar pattern of findings was obtained when group differences were examined between participants classified as severely hypoxic or mildly hypoxic, although group differences were mitigated by premorbid IQ differences. Hypoxia in COPD results in a relatively focused pattern of impairment in measures of memory function and tasks requiring attention allocation. The memory dysfunction may be related to involvement of limbic memory regions necessary for explicit memory. The attentional deficits were attributed to diffuse brain involvement resulting in reduced resource allocation. Early diagnosis and treatment of the hypoxia is essential.

Aged↗
PubMed1996

Do long tests yield a more accurate diagnosis of dementia than short tests? A comparison of 5 neuropsychological tests.

OBJECTIVE: To provide comparative evidence for a valid and practical measure of mental-status functioning that could be used in dementia clinics. DESIGN: Five mental-status neuropsychological tools for dementia screening were administered to patients in a memory disorder clinic. These included the Mini-Mental State Examination, the Dementia Rating Scale, the 6-item derivative of the Orientation-Memory-Concentration Test, a short Mental Status Questionnaire, and a composite tool we labeled the Ottawa Mental Status Examination, which assessed orientation, memory, attention, language, and visual-constructive functioning. The tools were compared using various criteria, including the statistical factors of sensitivity and reliability; effects of gender, native language, and language of testing; the utility of these tests for the differential diagnosis of Alzheimer-type and vascular dementia; and sensitivity to cognitive decline in the entire sample and among patients with severe dementia. RESULTS: All of the tests were highly intercorrelated, suggesting that they are interchangeable. CONCLUSION: The comparisons along the various criteria indicate that if the objective is to have a general index of dementia of the Alzheimer type, short tests are at least as good and sometimes better than the longer tests.

Aging↗
PubMed1996

Diagnosis of dementia. Methods for interpretation of scores of 5 neuropsychological tests.

OBJECTIVE: To provide methods to interpret and compare different neurobehavioral screening tests for the diagnosis of dementia. DESIGN: Five mental-status neuropsychological tools for dementia screening were administered to patients in a memory disorder clinic. These included the Mini-Mental State Examination, the Dementia Rating Scale, the 6-item derivative of the Orientation-memory-Concentration Test, a short Mental Status Questionnaire, and a composite tool we labeled the Ottawa Mental Status Examination, which assessed orientation, memory, attention, language, and visual-constructive functioning. RESULTS: To obtain z and percentile scores, norms are for the different tests, computed separately for patients with dementia of the Alzheimer type, vascular dementia, or no dementia. Another set of norms is reported in which a test score is translated directly into the posttest probability of dementia. Translation formulas are given to allow the estimation of the score on one test from the result on another test. CONCLUSION: The interpretation of tests used to diagnose dementia must be based on an understanding of the meaning of an individual score, which is based on the question asked and the population to which the patient is referenced.

Alzheimer Disease↗
PubMed1996

The dementias: nosological and clinical factors related to diagnosis.

There is no integrated nosological system for the classification of dementia. Four classification criteria in common use are site of pathology, histopathological changes, clinical features, and etiology. The use of these criteria, and the influence of other factors on diagnosis, are reviewed. Without a common comprehensive system, confusion has resulted when published studies have been compared. Since no single criterion is currently adequate, practical approaches for researchers and clinicians are suggested.

Age Factors↗
PubMed1996

Comparison of older people and patients with frontal lesions: evidence from world list learning.

We examined the hypothesis that changes in memory performance of older normal participants are due to frontal lobe dysfunction by comparing three groups of normal individuals (young, middle-aged, and older) with three groups of patients who had documented lesions in specific frontal regions: unilateral right, unilateral left, and bilateral. All participants were given 4 successive learning trials on each of 3 lists of words: unrelated, related but presented in a pseudo-random order, and related and presented in a blocked format. We found significant correspondences in performance between the older normal participants and the (younger) frontal damaged groups. The qualitative nature of recall performance, particularly as measured by indices of organizational control processes, was similar between older normals and patients with frontal damage, particularly those with right frontal damage, but different from that normally exhibited by patients with focal limbic/memory dysfunction. These results add to the evidence that at least some of the decline in older people in tasks which measure executive or supervisory abilities is due to frontal system dysfunction.

Adult↗
PubMed1996

Reaction time and variability 5 and 10 years after traumatic brain injury.

Improvement in performance can occur up to 10 years after traumatic brain injury (TBI). Few previous studies have examined the long-term effects of TBI on information processing. This study used reaction time (RT) tasks of increasing complexity with 10-year post-injury, 5-year post-injury, and control groups to assess any such effects. There were no significant group differences in mean RT; however, in the groups of persons with head injury only, response latency was related to age and to task demands. Older members of the groups of persons with head injury were slower than controls. The variability in performance was significantly higher in the 5-year post-injury group than in both the 10-year group and the control group. There were no significant differences among the groups in their ability to inhibit the processing of redundant information. There were no correlations between any dependent measure and severity of injury. Speed of processing is more sensitive to task complexity in individuals with head injury, but only when age at injury is considered. Most importantly, for rehabilitation purposes, recovery of consistency in performance can be expected more than 5 years after a TBI.

Adolescent↗
PubMed1995

Dissociation of processes underlying spatial s-r compatibility: evidence for the independent influence of what and where.

The process-dissociation procedure was used to estimate the influence of spatial and form-based processing in the Simon task. Subjects made manual (left/right) responses to the direction of arrows (> or <) presented to the left or right of fixation. Manipulating the proportion of incongruent trials (e.g., a right-pointing arrow presented to the left of fixation) affected both the size and direction of the Simon effect. To account for this pattern of data, we compared process estimates based on three possible relationships between spatial and form-based processing: independence, redundancy, and exclusivity. The independence model provided the best account of the data. Most telling was that independent form-based estimates were superior at predicting observed performance on arrows presented at fixation and did so consistently across conditions (r's > .80). The results provide evidence that the form ("what") and spatial location ("where") of a single stimulus can have functionally independent effects on performance. They also indicate the existence of two kinds of automaticity--an associative ("implicit learning") component that reflects prior S-R mappings and a nonassociative component that reflects the correspondence between stimulus and response codes.

Cognition↗
PubMed1995

Frontal lobe damage produces episodic memory impairment.

This article reports the outcome of a meta-analysis of the relation between the frontal lobes and memory as measured by tests of recognition, cued recall, and free recall. We reviewed experiments in which patients with documented, circumscribed frontal pathology were compared with normal control subjects on these three types of tests. Contrary to conventional wisdom, there is strong evidence that frontal damage disrupts performance on all three types of tests, with the greatest impairment in free recall, and the smallest in recognition.

Amnesia↗