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PubMed2005

Visual memory decay is deterministic.

After observers see an object or pattern, their visual memory of what they have seen decays slowly over time. Nearly all current theories of vision assume that decay of short-term memory occurs because visual representations are progressively and randomly corrupted as time passes. We tested this assumption using psychophysical noise-masking methods, and we found that visual memory decays in a completely deterministic fashion. This surprising finding challenges current ideas about visual memory and sets a goal for future memory research: to characterize the deterministic "forgetting function" that describes how memories decay over time.

Choice Behavior↗
PubMed2004

Phonological memory as a predictor of language comprehension in Down syndrome: a five-year follow-up study.

BACKGROUND: This study reports the language and memory progress over five years of 30 adolescents and young adults with Down syndrome, and investigates the relationship of earlier phonological memory abilities to later language development. METHODS: Tests of nonverbal ability, receptive vocabulary, grammar comprehension, digit span and nonword repetition were administered at two points in time. RESULTS: For the sample as a whole, there were significant gains in nonverbal ability, receptive vocabulary and grammar comprehension, but no increases in phonological memory measured by nonword repetition or digit span. However, there were considerable individual differences in progress which, in part, were related to chronological age. Phonological memory improved in many younger participants but there were signs of decline in some older ones. Partial correlations between earlier nonword repetition scores and later language scores, controlling for nonverbal ability and earlier language scores, indicated a significant role for phonological memory in the acquisition of vocabulary knowledge. There was similar evidence of a role for phonological memory in grammar comprehension, but only for younger participants. Earlier receptive vocabulary also predicted later nonword repetition scores, particularly for participants with higher levels of vocabulary knowledge. CONCLUSION: Relationships among the processes involved in language and memory development in Down syndrome may be similar to those established for typical development.

Adolescent↗
PubMed2005

Serial order reconstruction in Down syndrome: evidence for a selective deficit in verbal short-term memory.

BACKGROUND: Individuals with Down syndrome consistently perform less well than appropriately matched comparison groups on tests of verbal short-term memory, despite performing relatively well on non-verbal short-term memory tasks. However, it is not clear whether these findings constitute evidence for a selective deficit in verbal short-term memory, or whether they instead reflect the influence of non-central factors such as speech difficulties or poor number knowledge. METHODS: Twenty-six individuals with Down syndrome and 32 typically developing children were tested on a digit reconstruction task in which participants were presented with auditory digit sequences and responded by pressing the corresponding digits on a touch-screen in the correct serial order. Background measures were performance on a closely matched visuo-spatial reconstruction task, reaction time on a simple digit identification task, receptive vocabulary age and non-verbal ability (Raven's matrices). Participants were also tested on a conventional digit recall task. RESULTS: All four background measures accounted for significant individual variation in digit reconstruction performance, but there remained a significant effect of group that reflected relatively poor performance of individuals with Down syndrome. Hierarchical regression showed that group membership accounted for unique variation in both digit reconstruction and recall performance, even after all group differences on background measures had been accounted for. CONCLUSIONS: The results provide strong evidence that Down syndrome is associated with a selective deficit in verbal short-term memory, and a deficit in verbal serial order memory in particular. Implications for the language difficulties associated with Down syndrome are discussed.

Adolescent↗
PubMed1980

Prolonged ethanol consumption produces persistent alterations of cholinergic function in rat brain.

Prolonged ethanol consumption produces neuropathology and neurologic symptoms in humans and experimental animals. As a means of understanding the central nervous system (CNS) consequences of ethanol abuse, we sought whether cholinergic neurochemical functions were altered by long-term ethanol consumption by rats. Eighteen weeks of ethanol consumption in a liquid diet reduced rat striatal and mammillary body choline acetylase (ChAT) by 53% and 58%, respectively. In these same regions, the density of muscarinic cholinergic receptors was elevated 117% and 12%. No such alterations were observed in cortex or in hippocampus. No alterations followed short-term ethanol consumption (2 wk), but they persisted after ethanol withdrawal (4 wk). After 13 mo of ethanol consumption, the number of neuroleptic binding sites in striatum was diminished by 29%. These results demonstrate a persistent, possibly permanent, alteration in brain cholinergic function as a consequence of long-term ethanol ingestion. Since brain acetylcholine is involved in numerous neurologic functions, including memory processes, these findings may be relevant to the lasting memory disorder and other permanent effects associated with chronic alcoholism.

Alcoholism↗
PubMed1975

Auditory and visual memory losses in aging populations.

Seventy-four men and women (age range, 44-77 years) were tested for short-term auditory and visual memory as part of a larger series of memory and cognitive function tests. All test scores for visual memory, including facial photograph recognition when a sequence requirement was adhered to, showed a significant decline (p smaller than .05) in a comparison of subjects aged 44-54 and subjects aged 55-64. This decline was not observed with the two tests of auditory memory. Thus the data indicate that short-term visual memory may be more susceptible to aging than is auditory memory.

Adult↗
PubMed1992

Development of scoring criteria for the clock drawing task in Alzheimer's disease.

OBJECTIVE: To investigate the reliability and validity of free-hand clock drawings, a frequently used measure of constructional apraxia, in patients with Alzheimer's disease. DESIGN: Survey for the purpose of testing reliability and validity of a new scale. SETTING: Memory Disorder Clinic at a university-affiliated hospital in the Upper Midwest. PATIENTS: Forty-six patients were diagnosed with clinically probable dementia of the Alzheimer type after a dementia evaluation, and 26 normal elderly controls were research volunteers without a history of cognitive dysfunction. MEASUREMENTS: Neuropsychological tests, dementia-related scales, and clock drawings rated by a new 20-item Clock Drawing Interpretation Scale. Reliability measures, correlations, and clustering of items in the CDIS. RESULTS: The CDIS had inter-rater reliability (r = .94), internal consistence (rtt = .95), and reproducibility over a 6-month interval. CDIS scores were significantly correlated with two dementia-related scales and all neuropsychological tests and had the highest correlations with other measures of constructional apraxia. All but four Alzheimer patients (91%) and none of the controls had CDIS scores of 18 or less. CONCLUSION: Clinicians may reliably screen patients with Alzheimer's disease with the clock-drawing task, a measure sensitive to deficits in constructional apraxia.

Activities of Daily Living↗
PubMed1997

Questionable dementia: clinical course and predictors of outcome.

OBJECTIVE: To evaluate the clinical course and predictors of outcome in outpatients with cognitive impairment who do not meet criteria for dementia at initial evaluation. DESIGN: Naturalistic longitudinal study. METHODS: Cognitively impaired patients in a memory disorders clinic who fell between the "normal" and "dementia" categories were defined broadly as "questionable dementia" (QD). Of 127 consecutive QD patients, 75 were followed for a minimum of 1 year (mean 2.5 years, SD 1.7). Baseline neuropsychological testing was conducted in 62 of these 75 QD patients. RESULTS: At the final follow-up time-point, 41.3% met diagnostic criteria for dementia (27 of 31 patients with dementia had possible or probable Alzheimer's Disease, AD), 44% were rated as not demented, and 14.7% remained as "uncertain" dementia. Increased age was associated with the final diagnosis of dementia, but duration of follow-up, Clinical Dementia Rating, and modified Mini Mental State (mMMS) scores were not predictive. Low scores on the mMMS delayed recall subtest, consistent long-term retrieval on the Selective Reminding Test, category naming for animals, and the WAIS-R digit symbol, picture arrangement, and block design subtests were predictive of the final diagnosis of dementia (all P < or = .01). mMMS delayed recall showed 66.7% sensitivity and 71.4% specificity, the other five neuropsychological subtests together showed 66.7% sensitivity and 66.7% specificity, and the six tests together showed 81% sensitivity and 76.9% specificity. Similar predictive accuracy was obtained for the final diagnosis of AD. CONCLUSIONS: In QD patients, poor performance on the mMMS delayed recall item may be a useful predictor of the diagnosis of dementia (and AD) on follow-up. Combining a screening instrument like the mMMS with specific neuropsychological tests may provide good predictive accuracy. In QD patients, the observed heterogeneity in diagnostic outcome, with most patients in the "dementia" and "no dementia" categories at follow-up, enhances the feasibility of evaluating early markers with predictive accuracy for dementia and AD.

Age Distribution↗
PubMed1998

Assessing the impact of neuropsychiatric symptoms in Alzheimer's disease: the Neuropsychiatric Inventory Caregiver Distress Scale.

OBJECTIVES: To develop an adjunct scale to the Neuropsychiatric Inventory (NPI) for assessing the impact of neuropsychiatric symptoms in Alzheimer's disease (AD) patients on caregiver distress. DESIGN: Cross-sectional descriptive and correlational study. SETTING: University out-patient memory disorders clinics. PARTICIPANTS: Eighty-five AD subjects and their caregivers (54 spouses, 31 children). MEASUREMENTS: The NPI and NPI Caregiver Distress Scale (NPI-D) were used to assess neuropsychiatric symptoms in AD patients and related caregiver distress, respectively. Criterion validity of the NPI-D was examined (N = 69) by comparison with an abridged version of the Relatives' Stress Scale (RSS'), a general measure of caregiver stress, using item clusters that had previously been correlated to behavioral disturbances in demented patients. Test-retest (n = 20) and inter-rater reliability (n = 16) of the NPI-D were also assessed. RESULTS: Test-retest and interrater reliability of the NPI-D were both adequate. Overall, caregiver NPI-D distress ratings were correlated significantly with the RSS' (r = .60, P < .001). RSS' ratings correlated strongly with NPI scores (r = .64, P < .001), even after controlling for degree of cognitive impairment based on the Mini-Mental State Exam (MMSE) score (r = .61). MMSE scores showed a moderate correlation to RSS' ratings (-.30, P = .02), but this association was markedly attenuated when controlling for the degree of neuropsychiatric disturbance based on the NPI score (r = -. 14). NPI-D ratings for 9 of 10 NPI symptom domains correlated most strongly with either NPI symptom severity or total (frequency x severity) scores. Agitation, dysphoria, irritability, delusions, and apathy were the symptoms most often reported to be severely distressing to caregivers. CONCLUSIONS: The NPI-D provides a reliable and valid measure of subjective caregiver distress in relation to neuropsychiatric symptoms measured by the NPI. Neuropsychiatric alterations are more strongly associated than cognitive symptoms to caregiver distress. The NPI-D may be useful in both clinical and research settings for assessing the contribution to caregiver distress of neuropsychiatric symptoms in AD patients.

Aged↗
PubMed2004

The development of a rapid screen for caregiver burden.

OBJECTIVES: To develop a shortened screen for burden associated with caring for a patient with Alzheimer's disease (AD). DESIGN: Cross-sectional. SETTING: The Memory Disorders Clinic of an AD center. PARTICIPANTS: Two hundred fifty-one AD patient-caregiver dyads. MEASUREMENTS: Screen for Caregiver Burden (SCB), Center for Epidemiologic Studies Depression scale, Medical Outcomes Short Form, Mini-Mental State Examination, and patient and caregiver characteristics. RESULTS: At least 25% of the sample endorsed eight of the 25 items in the SCB subjective burden (SB) scale. Of these eight items with a prevalence of 25% or greater endorsement, seven items had item-total correlations of 0.55 or greater. The shortened seven-item SCB SB had an alpha of 0.86, indicating that the shortened scale has good internal consistency (Full SCB SB alpha=0.88). The seven-item SCB SB was highly associated with depression and overall mental health measures. CONCLUSION: This shortened version of the SCB allows a clinician to rapidly assess the burden associated with caregiving for a person with AD.

Adult↗
PubMedDate not supplied

Ovariectomy ameliorates dextromethorphan--induced memory impairment in young female rats.

We have previously found that dextromethorphan (DM), over-the-counter cough suppressant, impairs memory retention in water maze task, when it is repeatedly administrated to adolescent female rats at high doses. In this study we examined first if ovariectomy ameliorates the DM-induced memory impairment in female rats, and then whether or not the DM effect is revived by estrogen replacement in ovariectomized female rats. Female rat pups received bilateral ovariectomy or sham operation on postnatal day (PND) 21, and then intraperitoneal DM (40 mg/kg) daily during PND 28-37. Rats were subjected to the Morris water maze task from PND 38, approximately 24 h after the last DM injection. In probe trial, goal quadrant dwell time was significantly reduced by DM in the sham operated group, however, the reduction by DM did not occur in the ovariectomy group. When 17beta-estradiol was supplied to ovariectomized females during DM treatment, the goal quadrant dwell time was significantly decreased, compared to the vehicle control group. Furthermore, a major effect of estrogen replacement was found in the escape latency during the last 3 days of initial learning trials. These results suggest that ovariectomy may ameliorate the adverse effect of DM treatment on memory retention in young female rats, and that estrogen replacement may revive it, i.e. estrogen may take a major role in DM-induced memory impairment in female rats.

Animals↗