Biomedical subjects

K R Daffner

Publications and source records attributed to K R Daffner.

28 records · Page 2Linked to original sources

PubMed1994

A potential noninvasive neurobiological test for Alzheimer's disease.

Currently Alzheimer's disease, which affects more than 20 million people worldwide, can only be definitely diagnosed by histological examination of brain tissue obtained at autopsy or biopsy. There is a great need for an early, noninvasive, sensitive, and easily administered diagnostic test of Alzheimer's disease. Here it is reported that patients diagnosed with probable Alzheimer's disease by standard clinical criteria exhibited a marked hypersensitivity in their pupil dilation response to a cholinergic antagonist, tropicamide, placed in their eyes. It was possible to distinguish 18 of 19 individuals (95%) either clinically diagnosed with Alzheimer's disease or classified as suspect Alzheimer's individuals by neuropsychological screening from 30 of 32 normal elderly controls (94%).

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PubMed1994

The impact of aging on curiosity as measured by exploratory eye movements.

OBJECTIVE: To investigate changes in novelty-seeking behavior (curiosity) associated with normal aging. BACKGROUND: Recently, we demonstrated that patients with a diagnosis of probable Alzheimer's disease display diminished novelty-seeking behavior as measured by exploratory eye movements. Nondemented, elderly individuals are often depicted in clinical descriptions as exhibiting diminished curiosity and increased disengagement from their surroundings. However, this behavior has not been systematically investigated as a function of normal aging. SETTING: University hospital center studying aging and dementia. SUBJECTS: Fourteen active, healthy elderly subjects (mean age, 72 years) and 16 middle-aged subjects (mean age, 42 years) matched for education and estimated IQ. MEASURES: Exploratory eye movements were recorded in response to visual stimuli that varied in novelty, complexity, and incongruity. RESULTS: Both older and middle-aged subjects (1) spent significantly more time exploring the more irregular or incongruous of two simultaneously presented stimuli, (2) spent increasingly less time looking at a repeating visual stimulus paired with a stimulus that changed with each trial, and (3) exhibited the same degree of overall exploration of a visual scene and devoted an approximately equal amount of attention to an unexpected element within it. As a group, older subjects spent slightly less time than middle-aged subjects examining incongruous stimuli. However, 71% (10/14) of older subjects performed within 1 SD of the mean of middle-aged subjects and 21% (3/14) performed as well as the top 50% (8/16) of middle-aged controls. CONCLUSIONS: The drive for curiosity, as measured by exploratory eye movements, can be well preserved in older individuals. Further research is needed to determine if the integrity of this drive can serve as a marker of "successful aging" and to identify which physiological and psychological factors influence its preservation through the life cycle.

Adult↗

PubMed1994

Impairment of spatially directed attention in patients with probable Alzheimer's disease as measured by eye movements.

OBJECTIVE: To investigate changes in spatially directed attention in patients with a diagnosis of probable Alzheimer's disease (AD). BACKGROUND: Impaired attention in patients with probable AD has not been the subject of extensive research. Yet recent reports suggest that attentional deficits may be an important early feature of the disease in a subset of patients. SETTING: University hospital center studying dementia and aging. SUBJECTS: Ten mild to moderately impaired patients diagnosed as having probable AD, by National Institute of Neurologic and Communicative Diseases and Stroke criteria, and 11 healthy age- and education-matched controls. MEASURES: Eye movements were recorded as subjects participated in two experiments designed to measure spatially directed attention. Subjects were instructed to (1) attend to and fixate a target appearing randomly to the right or left of a central marker and (2) direct attention to and fixate a target appearing randomly in one of four peripheral locations. RESULTS: Patients with probable AD exhibited fewer accurate trials and longer saccade latencies in both tasks. As a group, patients performed worse in the second task that placed increased demands on attention. However, the performance of patients in this second experiment varied. Four patients performed significantly worse than all other patients, while three patients performed as well as controls. Errors in the second task were reviewed to identify specific types of attentional deficits. Six empirically derived error patterns were classified into one of two major categories: perseveration and impersistence. Seven of 10 patients made greater than 50% errors of perseveration, and three of 10 made greater than 50% errors of impersistence. CONCLUSIONS: Impairment of attention may be an early feature of AD and a prominent clinical characteristic of some patients. The differences observed in error types made by patients may reflect the varied distribution of neuropathologic changes affecting structures that mediate aspects of attention. The architecture of eye movements can be used as a physiologic measure that should provide useful information for the diagnosis and clinicopathologic subtyping of patients with AD.

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PubMed1992

Diminished curiosity in patients with probable Alzheimer's disease as measured by exploratory eye movements.

Clinical accounts of Alzheimer's disease (AD) suggest that some patients exhibit markedly diminished curiosity and initiative early in the course of their illness. Such behavioral changes are extremely difficult to measure experimentally. We studied one aspect of curiosity by measuring exploratory eye movements in response to provocative visual stimuli in 12 patients with probable AD and 10 matched controls. Subjects viewed slides, each of which contained an incongruous or irregular figure paired with a congruous or regular one. Unlike controls, who spent significantly more time viewing the incongruous stimuli, AD patients distributed their viewing time equally and spent significantly less time than controls looking at the novel stimuli. Additionally, when presented with picture slides containing an unexpected element, AD patients exhibited diminished visual exploration overall and decreased attention to the incongruous part. Further analyses suggest that the results cannot be adequately explained by a general decline in cognition or by problems with ocular motility or directing visual attention. We conclude that AD patients exhibit diminished curiosity which can be measured by the study of exploratory eye movements.

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PubMed1991

Broca's aphasia following damage to Wernicke's area. For or against traditional aphasiology?

Classic aphasiology has been challenged by studies that have employed cranial computed tomography to test predicted anatomic-behavioral correlations. We treated a patient who developed a classic Broca's aphasia but whose computed tomographic scan revealed damage to Wernicke's area, thus seeming to contradict the principles of traditional aphasiology. However, subsequent information obtained by magnetic resonance imaging, intracarotid amobarbital (Amytal) testing, and electrophysiologic studies, including cortical stimulation, demonstrated that the brain-behavior correlations in this patient can be understood in terms of the formulations of traditional aphasiology.

Adult↗

PubMed1991

Frontal lobe dysfunction following infarction of the left-sided medial thalamus.

We treated a 62-year-old woman who developed a dramatic change in personality and behavior following a discrete left-sided medial thalamic infarction involving the dorsomedial nucleus. Neuropsychological testing demonstrated severe impairment of complex executive behaviors that are usually associated with frontal lobe function. Electroencephalography and single-photon emission computed tomography strongly implicated dysfunction of the ipsilateral frontal lobe. This case further supports a functional and physiologic thalamofrontal linkage as part of a broader cerebral network modulating complex human behavior.

Brain Diseases↗

PubMed1990

Dissociated neglect behavior following sequential strokes in the right hemisphere.

A 42-year-old woman suffered two focal right hemisphere strokes, sequentially damaging different components of a proposed cerebral network for the spatial distribution of attention. Her first stroke was centered in the right frontal lobe and resulted in left hemi-spatial neglect but only for tasks that emphasize exploratory-motor components of directed attention. A second stroke occurred 20 days later in the parietal lobe and led to the emergence of perceptual-sensory aspects of neglect. This case strongly supports the existence of a distributed anatomic-functional network subserving directed attention.

Adult↗

PubMed1990

The comportmental learning disabilities of early frontal lobe damage.

Two adult patients are described who suffered bilateral prefrontal damage early in life and who subsequently came to psychiatric attention because of severely aberrant behaviour. A battery of developmental psychology paradigms (not previously used to assess neurologically impaired individuals) showed that social and moral development of these 2 patients was arrested at an immature stage. In comparison with other types of brain damage which disrupt cognitive development, frontal damage acquired early in life appears to provide the neurological substrate for a special type of learning disability in the realms of insight, foresight, social judgement, empathy, and complex reasoning.

Adult↗

PubMed1990

Lyme polyradiculoneuropathy presenting as increasing abdominal girth.

We describe a patient with documented Lyme disease whose major complaint was increasing abdominal distention. Electrophysiologic studies demonstrated denervation of the lower thoracic paraspinal muscles and the rectus abdominis. Expanding abdominal girth can be an unusual manifestation of the polyradiculoneuropathy associated with Lyme disease.

Abdominal Muscles↗

PubMedDate not supplied

Selective cell loss in Edinger-Westphal in asymptomatic elders and Alzheimer's patients.

Exaggerated pupillary response to a low concentration of cholinergic antagonists has been suggested as an early marker for Alzheimer's Disease (AD). To examine the anatomic basis of this phenomenon, we determined possible neuropathological changes in the Edinger-Westphal (EW) nucleus, a midbrain neural center with a significant functional role in the control of pupil size. Stereologically determined neuronal numbers within the EW were counted in individuals with pathologically confirmed AD, control cases with no AD-type pathology, and subjects with AD pathology not meeting diagnostic criteria for AD. The EW of AD patients displayed a marked and striking neuronal loss when compared with controls. In contrast, the number of neurons in the somatic portion of the nucleus of the third cranial nerve (NCNIII) remained intact. The EW in brains from clinically normal individuals with evidence of early AD-type pathology also displayed a significant and selective loss of neurons. The magnitude of EW neuronal loss in the latter group was smaller than that observed in AD. These findings suggest that pupillary hypersensitivity in AD may be caused by abnormalities in the EW. Neuronal loss and pathology within the EW in a subpopulation of clinically silent controls with pathologic findings consistent with early-stage AD constitutes a possible explanation for the reported exaggerated pupil response in some normal elderly subjects.

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