The pattern of deficit in different memory components in normal aging and dementia of Alzheimer's type

Modern scores for traditional tests - Review of the diagnostic potential of scores derived from word list learning tests in mild cognitive impairment and early Alzheimer's Disease

Episodic memory impairment is one of the early hallmarks in Alzheimer's Disease. In the clinical diagnosis and research, episodic memory impairment is typically assessed using word lists that are repeatedly presented to and recalled by the participant across several trials. Until recently, total learning scores, which consist of the total number of words that are recalled by participants, were almost exclusively used for diagnostic purposes. The present review aims at summarizing evidence on additional scores derived from the learning trials which have recently been investigated more frequently regarding their diagnostic potential. These scores reflect item acquisition, error frequencies, strategy use, intertrial fluctuations, and recall consistency. Evidence was summarized regarding the effects of clinical status on these scores. Preclinical, mild cognitive impairment and mild Alzheimer's Disease stages were associated with a pattern of reduced item acquisition, more errors, less strategy use, and reduced access of items, indicating slowed and erroneous encoding. Practical implications and limitations of the present research will be discussed.

Age- and gender-adjusted normative data for the German version of Rey's Auditory Verbal Learning Test from healthy subjects aged between 50 and 70 years

Rey's Auditory Verbal Learning Test (AVLT) is widely used to evaluate dysfunctional episodic memory. The current study aimed to provide extended age- and gender-specific norms for the German AVLT for individuals older than 50 years. In 690 subjects, a comprehensive medical examination including a structural 3.0-tesla magnetic resonance imaging scan was administered, as well as extensive neuropsychological tests. After controlling for exclusion criteria, 407 subjects were included in the analysis. AVLT performance decreased with age, and women outperformed men. We present age- and gender-specific normative data for the German AVLT from subjects aged between 50 and 70 years.

Affecting cognition and quality of life via aerobic exercise in Alzheimer's disease

Aerobic exercise is a promising behavioral therapy for Alzheimer's disease (AD), yet few studies have investigated the effect of aerobic exercise on cognition in AD. The purpose of this pilot study was to examine the effect of 6-month aerobic exercise on the change in executive function, global cognition, quality of life (QOL), and depression in community-dwelling older adults with mild to moderate AD. A single group, repeated measures design with outcomes measured at baseline, 3 months, and 6 months was used. Results show that there were no significant changes in any measures except for depression (p = .026). There was a trend toward improvement in executive function and QOL with moderate effect sizes (ESs) and a trend toward deterioration in global cognition with moderate to large ESs. Randomized controlled trials are needed to evaluate the therapeutic effect of aerobic exercise in older adults with AD.

Development of an efficient therapeutic agent for Alzheimer's disease: design and synthesis of dual inhibitors of acetylcholinesterase and serotonin transporter

To date, acetylcholinesterase (AChE) inhibitors have been clinically effective drugs for the palliative treatment of Alzheimer's disease, but their clinical efficacy is limited, mainly due to their adverse effects on peripheral organs. Since patients of Alzheimer's disease often exhibit depression as well as memory impairment, dual inhibitors of AChE and serotonin transporter (SERT) would be a better therapeutic method. Anti-depressive effects based on SERT inhibition would reduce the dose-related side effects of AChE inhibitors. Such dual inhibitors were designed by the hybridization of rivastigmine and fluoxetine based on a hypothetical model of the AChE active site. Various derivatives were synthesized and evaluated for their in vitro inhibition, and then (S)-5j (RS-1259), which possessed balanced inhibitory activities of AChE (IC(50)=101 nM) and SERT (IC(50)=42 nM), was successfully obtained. An ex vivo experiment in mice indicated that (S)-5j (RS-1259) simultaneously inhibited AChE and SERT in the brain following an oral administration. The simultaneous elevation of extracellular levels of acetylcholine and serotonin in the rat hippocampus was actually confirmed by microdialysis.

Cognitive phenotypes, brain morphometry and the detection of cognitive decline in preclinical AD

Identifying a preclinical phase of Alzheimer’s Disease (PCAD) that is distinct from cognitive changes in healthy aging continues to be a major research focus. Combining neuropsychological and neuroimaging methodologies should improve our ability to differentiate healthy from pathological aging, although studies that utilize both methods often result in equivocal findings, possibly due to variability in cognitive test performance that may be capturing distinct phenotypes. One method of capturing this cognitive variability is to utilize contrasting neuropsychological tests to identify subgroups representative of distinct cognitive phenotypes, and determine whether differences in brain morphometry support these classifications. We review several approaches to defining cognitive subgroups, and we consider the possibility that cognitive asymmetry might provide one means of identifying both functional and structural changes associated with aging and dementia.

Charakterisierung kognitiver Einbußen von Patienten mit “Mild Cognitive Impairment” (MCI) in der CERAD- Screeningbatterie

Zusammenfassung: Die frühzeitige Diagnose kognitiver Abbauprozesse ist vor dem Hintergrund der “alternden Gesellschaft” von enormer Bedeutung. In der vorliegenden Arbeit wurde das Potenzial der CERAD-kognitiven Screeningbatterie als Untersuchungsprotokoll zur Diagnostik leichter kognitiver Beeinträchtigungen (MCI, Petersen et al., 1995 ) sowie als Verlaufsinstrument überprüft. Die Leistungen von 51 MCI-Patienten wurden mit 81 gesunden Kontrollpersonen verglichen. Die Leistungen der MCI-Gruppe unterschied sich in nahezu allen Subtests der CERAD-Batterie signifikant von denen der Kontrollgruppe. In der Verlaufsuntersuchung an einer Teilstichprobe (n = 18) fanden sich hingegen in der CERAD-Batterie keine signifikanten Veränderungen. Zusammenfassend lässt sich feststellen, dass die CERAD-Batterie bei leichten kognitiven Beeinträchtigungen ein ausreichend valides Screeninginstrument darstellt; für Verlaufsuntersuchungen scheint sie hingegen weniger gut geeignet zu sein.

Differences between recognition memory and remote memory for olfactory and visual stimuli in nondemented elderly individuals genetically at risk for Alzheimer's disease

Recognition and remote memory for olfactory and visual stimuli were assessed in nondemented elderly individuals positive for the apolipoprotein E 4 allele and in 4 negative controls to examine whether the 4 allele differentially affects recognition and/or remote memory depending on the modality of stimulus to be remembered. Compared to controls, 4 positive individuals committed more false positive recognition memory errors for olfactory but not visual stimuli suggesting that 4 positive individuals may show false positive errors for olfactory stimuli before deficits for other stimuli are detectable. There were no significant differences in familiarity ratings (a proposed measure of remote memory) suggesting that brain areas involved in remote memory are not affected in nondemented 4 positive individuals. The results suggest that neuropathological changes in nondemented individuals genetically at risk for Alzheimer's disease may differentially affect memory processes.

Pharmacological characterization of RS-1259, an orally active dual inhibitor of acetylcholinesterase and serotonin transporter, in rodents: possible treatment of Alzheimer's disease

A dual inhibitor of acetylcholinesterase (AChE) and serotonin transporter (SERT), RS-1259 (4-[1S)-methylamino-3-(4-nitrophenoxy)]propylphenyl N,N-dimethylcarbamate (fumaric acid)(1/2)salt), was newly synthesized. RS-1259 simultaneously inhibited AChE and SERT in the brain following an oral administration in mice and rats. Actual simultaneous elevation of extracellular levels of 5-HT and ACh in the rat hippocampus was confirmed by microdialysis. The compound was as effective as SERT inhibitors such as fluoxetine and fluvoxamine in a 5-hydroxytryptophan-enhancing test in mice. Spatial memory deficits in the two-platform task of a water maze in aged rats were ameliorated by RS-1259 as well as donepezil. Both RS-1259 and donepezil increased the awake episodes in the daytime electroencephalogram of rats. Although RS-1259 was weaker than donepezil in enhancing central cholinergic transmission, as observed by ACh elevation in the hippocampus and memory enhancement in aged rats, the efficacy of RS-1259 on the consciousness level, which reflects the whole activity in the brain, was almost the same as that of donepezil. These results suggest that both cholinergic and serotonergic systems are involved in maintaining brain arousal and that a dual inhibitor of AChE and SERT may be useful for the treatment of cognitive disorders associated with reduced brain activity such as in Alzheimer's disease.

Excitotoxic median raphe lesions aggravate working memory storage performance deficits caused by scopolamine infusion into the dentate gyrus of the hippocampus in the inhibitory avoidance task in rats

The interactions between the median raphe nucleus (MRN) serotonergic system and the septohippocampal muscarinic cholinergic system in the modulation of immediate working memory storage performance were investigated. Rats with sham or ibotenic acid lesions of the MRN were bilaterally implanted with cannulae in the dentate gyrus of the hippocampus and tested in a light/dark step-through inhibitory avoidance task in which response latency to enter the dark compartment immediately after the shock served as a measure of immediate working memory storage. MRN lesion per se did not alter response latency. Post-training intrahippocampal scopolamine infusion (2 and 4 microg/side) produced a more marked reduction in response latencies in the lesioned animals compared to the sham-lesioned rats. Results suggest that the immediate working memory storage performance is modulated by synergistic interactions between serotonergic projections of the MRN and the muscarinic cholinergic system of the hippocampus.

Effects of excitotoxic median raphe lesion on working memory deficits produced by the dorsal hippocampal muscarinic receptor blockade in the inhibitory avoidance in rats

The experiments investigated the interactions between median raphe nucleus (MRN) serotonergic and septo-hippocampal muscarinic cholinergic systems in the modulation of forming and storing performances of working memory. Rats with ibotenic acid-induced MRN-lesion bilaterally received scopolamine (2-4 microg/each side) infusion into the dentate gyrus of the dorsal hippocampus and were tested in a single trial step-through inhibitory avoidance. Initial preference to the dark compartment (escape latency) was taken as the measure of non-mnemonic behaviours and response latency to enter the dark compartment immediately after the foot-shock was used to measure working memory. The high-dose scopolamine infusion 10 min before the training decreased escape latencies in the sham-lesioned rats, whereas had no effect in the MRN-lesioned rats. Although MRN lesion per se did not alter response latency, it alleviated pre-training scopolamine-induced decrease, but aggravated post-training scopolamine-induced reduction in this parameter. These results suggest that the antagonistic interactive processes between MRN-serotonergic and hippocampal cholinergic systems modulate non-mnemonic component of working memory formation, whereas the storing performance of working memory is modulated by the synergistic interactions between these systems in the hippocampus, mainly in the dentate gyrus.

Participation of hippocampal metabotropic glutamate receptors, protein kinase A and mitogen-activated protein kinases in memory retrieval

The ability to recall past events is a major determinant of survival strategies in all species and is of paramount importance in determining our uniqueness as individuals. In contrast to memory formation, the information about the molecular mechanisms of memory retrieval is surprisingly scarce and fragmentary. Here we show that pretest inhibition of the specific upstream activator of mitogen-activated protein kinase kinase, or of protein kinase A in the hippocampus, blocked retrieval of long-term memory for an inhibitory avoidance task, a hippocampal-dependent learning task. An activator of protein kinase A enhanced retrieval. Mitogen-activated protein kinase activation increased in the hippocampus during retrieval, while protein kinase A activity remained unchanged. Pretest intrahippocampal blockade of metabotropic glutamate receptors or alpha-amino-3-hydroxy-5-methyl-4-isoxazolone propionic acid/kainate receptors, but not N-methyl-D-aspartate receptors or calcium/calmodulin dependent-protein kinase II, impaired retrieval. Thus, recall of inhibitory avoidance activates mitogen-activated protein kinase, which is necessary, along with metabotropic glutamate receptors, alpha-amino-3-hydroxy-5-methyl-4-isoxazolone propionic acid/kainate receptors, and protein kinase A, for long-term memory expression. Our results indicate that memory formation and retrieval may share some molecular mechanisms in the hippocampus.

Verbal and figural recognition memory: task development and age associations

The goal of the present study was to develop and validate parallel tests of verbal and figural delayed-recognition memory with similar task demands and difficulty levels. Such tasks would allow examination of age differences and longitudinal age changes in visual recognition memory for two types of stimuli, activate divergent neural systems, and allow us to use the same procedures within the confines of functional neuroimaging as those we use in standard neuropsychological administration. The tasks introduced here include a delay between target presentation and test phase, are matched in difficulty, and yield moderate levels of performance. Individual and group differences in task performance were examined in 80 cognitively normal men and women in two older age groups: 60 to 69 and 70 to 85. Accuracy averaged 74% in both tasks, with lower performance in the oldest age group. Although accuracy was equivalent between tasks, subjects had a more liberal response bias in the figural than verbal task. Performance on the new recognition-memory tests was significantly related to Benton Visual Retention Test (BVRT; Benton [1963]. New York: The Psychological Corporation) and California Verbal Learning Test (CVLT; Delis, Kramer, Kaplan, & Ober [1987]. New York: The Psychological Corporation) performance measures. The absence of floor or ceiling effects, wide range of individual variability, and demonstrated concurrent validity of the present tasks suggest their potential utility in functional neuroimaging studies and in the early detection of cognitive decline.