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Biomedical subjects

S Corkin

Publications and source records attributed to S Corkin.

At least 55 records · Page 3Linked to original sources
PubMed1991

Visual function in Alzheimer's disease and normal aging.

We examined a wide range of visual behaviors in 59 patients with Alzheimer's disease (AD), 35 elderly control subjects, and 12 young control subjects. A subset of the patients with AD received neuro-ophthalmologic and electrophysiologic examinations in order to evaluate the integrity of the retino-calcarine pathway. Patients with AD showed significant, selective losses in visual function, including color discrimination, stereoacuity, contrast sensitivity, and backward masking, but not in critical flicker fusion. The deficits were not attributable to clinically apparent lesions of the retina or optic nerve. We therefore suggest that AD lesions in primary visual and posterior association cortices underlie the observed behavioral abnormalities.

Adolescent↗
PubMed1990

Intact priming of patterns despite impaired memory.

The priming of patterns was examined in normal control subjects (NCS) and in the amnesic patient H.M., whose anterograde amnesia followed bilateral medial temporal-lobe excision 33 years earlier. Despite H.M.'s impaired recognition of the patterns, he demonstrated a pattern priming effect equivalent in magnitude to that of the NCS. The results demonstrated that intact priming with novel, nonverbal material can occur despite severe amnesia. Pattern priming may reflect adaptive visual processes involved in learning novel perceptual organizations of known visual codes, such as letters, words, shapes, and objects.

Amnesia↗
PubMed1990

Stroop Color-Word Test performance in patients with Alzheimer's disease.

Patients with Alzheimer's disease (AD) (n = 36) and normal older adults (n = 36) were individually administered the Stroop Color-Word Test. Eight of 36 (22%) AD patients exhibited confusion between the colors blue and green, while no control subject had difficulty distinguishing among the colors. In a second experiment, a subset of the original sample (15 AD patients and 8 control subjects) was retested using the Stroop. Only 2 AD patients showed color confusion on both test occasions, while 7 AD patients exhibited color confusion on one occasion. No control subject exhibited confusion between colors the second time. These results indicate that color confusion in AD patients is inconsistent. Due to the high incidence of color confusion in AD patients, the Stroop should be used with caution in patient populations.

Aged↗
PubMed1990

Recency and frequency discrimination in the amnesic patient H.M.

Temporal contextual memory and event memory were compared across retention intervals in the patient H.M. who is amnesic following bilateral medial temporal lobectomy. Memory for temporal context was assessed using verbal and nonverbal recency discrimination tasks and a frequency task in which subjects made discriminations between words repeated 1, 3 or 5 times. The tests evaluated event memory under parallel conditions by two-choice content recognition tasks. In both recency and frequency tests, H.M. showed above-chance and often normal temporal contextual memory under conditions of impaired and even chance-level content recognition. These results show that temporal contextual memory does not require intact content recognition and is independent of medial temporal lobe structures. Furthermore, the amnesia of bilateral medial temporal lobe resection does not manifest primary loss of temporal contextual memory.

Amnesia↗
PubMed1989

Selective attention in Alzheimer's disease: characterizing cognitive subgroups of patients.

Picture recognition was studied in 20 patients with AD and in 20 control subjects, using a procedure that matched these groups for initial performance. The groups did not differ significantly in overall forgetting, although 10 patients displayed improved recognition performance 72 hr after learning. These same patients were impaired in a test of attentional focusing, as revealed by post hoc analyses. A predictive experiment involving 20 new patients with AD confirmed the initial findings: a subgroup of patients displayed improved recognition performance 72 hr after learning and impairments in attentional focusing. Neuropsychological tests thus identify a subgroup of patients with impaired selective attention, perhaps related to locus coeruleus neuropathology.

Aged↗
PubMed1989

Different cognitive profiles on standard behavioral tests in Parkinson's disease and Alzheimer's disease.

Patients with Parkinson's disease (PD) displayed a different pattern of cognitive deficit from patients with dementia resulting from Alzheimer's disease (AD). Specifically, PD patients, whether or not impaired on a mental status examination, had deficient Picture Arrangement but normal Vocabulary test scores whereas AD patients were impaired on both measures. Furthermore, PD patients with impaired mental status examination scores showed a deficit in set formation on Picture Arrangement not seen in the AD patients. Finally, when recent memory performance, as measured by the Wechsler Memory Scale, was predicted from an estimated IQ, 71% of PD patients who had normal mental status examination scores were seen to have at least a mild memory impairment.

Aged↗
PubMed1989

Penetrating head injury in young adulthood exacerbates cognitive decline in later years.

Few investigators have studied whether the behavioral effects of brain insult in adulthood are stable after the period of maximum recovery. We addressed this issue in a 30-year longitudinal study of 84 veterans of World War II, 57 with penetrating head injury (HI) and 27 with peripheral nerve injury (PNI), matched with respect to age, premorbid intelligence, and premorbid education. Each subject was examined during the 1950s and during the 1980s; each examination included the largely verbal Army General Classification Test (AGCT) (with Vocabulary, Arithmetic, and Block Counting subscales) and the Hidden Figures Test (which measures figure-ground discrimination). HI exacerbated decline in performance over time, irrespective of lesion site or cognitive test. HI and PNI subjects differed significantly (p less than 0.05) in AGCT Total and Arithmetic change scores, and means were in the same direction for all other measures. In analyses contrasting subjects in each of the eight lesion groups to PNI subjects, those with left parietal lobe injuries showed significantly greater decline from the 1950s to the 1980s on the Vocabulary and Arithmetic subscales of the AGCT, as did those with left temporal lobe injuries on the Arithmetic subscale, whereas subjects with right parietal lobe injuries showed significantly greater decline on the Hidden Figures Test. We hypothesize that the observed reduction of cognitive capacities late in life was due to some combination of HI in young adulthood, secondary effects of the injury occurring with time, effects of stress on remaining brain tissue caused by functioning for decades in a compromised state, and changes in the brain occurring with age. Although the HI subjects were not demented, follow-up studies must assess whether exacerbated decline is a harbinger of dementia.

Adult↗
PubMed1988

Selective attention in Alzheimer's disease: CSF correlates of behavioral impairments.

CSF levels of HVA, 5-HIAA, and free MHPG, the major metabolites of dopamine, serotonin, and norepinephrine respectively, were measured in 22 patients with AD. These 22 patients were also administered tests of picture-recognition and attentional focusing as part of an earlier experiment. A significant association between deficits in attentional focusing and reduced levels of free MHPG in CSF was noted. These results suggest that behavioral measures can identify patients with noradrenergic involvement.

Aged↗
PubMed1988

The impaired learning of semantic knowledge following bilateral medial temporal-lobe resection.

The integrity of several aspects of semantic memory (including knowledge of the meaning, lexical status, perception, and pronunciation of words and famous names) was examined in H.M., a patient with anterograde amnesia following bilateral medial temporal-lobe excision. Despite normal memory for such semantic knowledge acquired prior to the onset of his amnesia in 1953, H.M. showed a severe deficit in memory for semantic information encountered subsequently. In combination with the previously reported impairments in new learning shown by H.M., the deficits observed here point to an association between semantic and episodic memory, and do not lend support to a distinction between them. The acquisition of semantic and episodic information, therefore, appears to depend upon a common memory system that requires the intact functioning of medial temporal-lobe structures.

Aged↗
PubMed1988

Rate of forgetting in H.M.: 6-month recognition.

The picture-recognition performance of H.M. and six control subjects was evaluated 6 months after initial learning, using materials from an earlier study in which H.M. received additional study time in order to equate his yes-no and delayed-match-to-sample (DMS) performance 10 min after learning to that of control subjects. In the study detailed here, 6-month recognition performance was assessed with no intervening exposure to the target items. H.M. performed at chance levels when tested using the standard yes-no recognition procedure. When the yes-no procedure was modified so that distractor stimuli required positive responses, H.M.'s performance was comparable with that of control subjects. In addition, H.M.'s DMS and delayed-nonmatch-to-sample (DNMS) performance were comparable with that of control subjects 6 months after learning. Conclusions regarding H.M.'s 6-month recognition performance are thus dependent on the procedures used to assess memory.

Amnesia↗
PubMed1988

Remote memory function in Alzheimer's disease and Parkinson's disease.

Remote memory for public and personal events was evaluated in Alzheimer's disease (AD) and Parkinson's disease (PD), using a series of recall and recognition tests. Information related to content and date of past events was assessed separately. In recall of the content of personal and public events, both groups showed a gradient of deficit in which remote events were affected less than recent ones; the magnitude and temporal extent of the retrograde loss was related to severity of dementia. By contrast, gradient effects were not evident in the recall of date and were less marked in the recognition of content or date. In public and personal events tests, patients with PD showed a relative impairment in dating capacity, compared with their memory for the content of events, which was independent of dementia. These results suggest that dementia affects the recall of distant events less than recall of recent ones. Furthermore, the selective gradient effects in recall of content suggest that memory for date is served by cognitive processes independent of memory for event content. In PD, dating capacity is a sensitive measure of remote memory function that may be disrupted independently of dementia.

Alzheimer Disease↗
PubMed1988

Temporal ordering and short-term memory deficits in Parkinson's disease.

Previous studies of remote memory function have indicated a dissociability between memory for the content and date of past events and suggested selective deficits of dating capacity in Parkinson's disease (PD). The present study examined the hypothesis that poor dating in PD is linked to a specific deficit in temporal contextual memory which also affects new learning. Patients with PD and patients with Alzheimer's disease (AD) were compared in their ability to perform tasks of content recognition and recency discrimination of words presented sequentially. Compared with AD patients, PD patients were disproportionately impaired in recency discrimination relative to content recognition. When performance was analysed as a function of retention interval, AD patients showed impairment in both tasks at all intervals. PD patients, by contrast, showed deficits in content recognition at the short stimulus-test intervals only, possibly reflecting the clinical phenomenon of bradyphrenia. These results suggest that recency discrimination deficits and impaired short-term memory processing are specific cognitive deficits in PD that may be linked to subcortical deafferentation of the frontal lobes.

Alzheimer Disease↗
PubMed1987

Forgetting in H.M.: a second look.

Forgetting was assessed in the amnesic patient H.M. using forced-choice and yes-no picture recognition at four delay intervals: 10 min, 24 hr, 72 hr, and 1 week after learning. In order to make H.M.'s initial recognition performance comparable to that of control subjects who viewed each slide for 1 sec, H.M. viewed each slide for 20 sec. H.M. displayed normal forgetting in forced-choice and yes-no recognition, although he was impaired in yes-no recognition at the 24-hr delay interval. These data contradict Huppert and Piercy's hypothesis that medical temporal-lobe pathology is associated with rapid forgetting.

Epilepsy↗
PubMed1987

Age at onset and rate of progression of Alzheimer's disease.

Age at onset, duration, and severity of dementia were evaluated in 165 patients with a clinical diagnosis of Alzheimer's disease. Rate of progression of dementia was determined in 77 patients by repeated administration of the Blessed Dementia Scale (BDS). The distribution of age at onset among patients was bimodal, with a division at about age 65. Duration of dementia at the time of initial examination was shorter, and rate of progression on follow-up examination was more rapid in senile-onset (age 65 or greater) than in presenile-onset (before age 65) cases. Considerable overlap among values for the two patient groups was observed for both variables, indicating that age at onset is not a strong predictor of rate of progression of dementia in patients with Alzheimer's disease.

Age Factors↗
PubMed1987

Comparison of rates of progression in Alzheimer's disease and Parkinson's disease.

In order to compare the progression of memory impairments in Parkinson's disease (PD) and Alzheimer's disease (AD), we administered the Memory and Information section of the Blessed Dementia Scale (BDS) at least twice to 33 patients with PD and 70 with AD. The BDS scores of AD patients deteriorated over time. In contrast, the scores of PD patients were essentially stationary. A substantial difference in rate of cognitive decline persisted upon comparing only those PD and AD patients who showed memory deficits of the same magnitude. The uniform failure to observe cognitive deterioration among PD patients suggests that any PD patients who deteriorate at a rate typical of AD may indeed have AD or a related dementing disorder in addition to the characteristic nigral-striatal degeneration of PD.

Alzheimer Disease↗