Procedural memory in patients with mild Alzheimer's disease

Does Cognitive Impairment Impact Motor Learning? A Scoping Review of Elderly Individuals With Alzheimer's Disease and Mild Cognitive Impairment

Individuals with cognitive impairment may have motor learning deficits due to the high engagement of cognitive mechanisms during motor skill acquisition. We conducted a scoping review to address the quality of current research on the relationship between cognitive impairments (i.e., deficits in attention, memory, planning and executive functions) and motor learning among older adults with Alzheimer's Disease or Mild Cognitive Impairment. After screening thousands of articles, we selected 15 studies describing cognitive assessment tools, experimental designs, and the severity of cognitive impairment. Although seven studies reported that cognitive impairment impaired motor learning, most studies included a high risk of bias. We identified multiple assessment tools across these studies that make comparisons among findings difficult. Future research in this area should focus on the influence of increased practice days during motor learning acquisition and incorporate both retention and transfer tests. Cognitive assessments should target the specific cognitive skills or deficits most closely related to the motor learning process.

Cognitive Decline Associated with Aging

Cognitive decline is one of the most distinct signs of aging, and age-related cognitive decline is a heterogeneous issue varying in different cognitive domains and has significant differences among older adults. Identifying characteristics of cognitive aging is the basis of cognitive disease for early-detection and healthy aging promotion. In the current chapter, age-related decline of main cognitive domains, including sensory perception, memory, attention, executive function, language, reasoning, and space navigation ability are introduced respectively. From these aspects of cognition, we focus on the age-related effects, age-related cognitive diseases, and possible mechanisms of cognitive aging.

Functional Therapeutic Strategies Used in Different Stages of Alzheimer's Disease-A Systematic Review

As Alzheimer's disease develops, the central nervous system is gradually damaged. It is manifested by progressive dementia and the appearance of neurological and extrapyramidal symptoms that impair everyday functioning. The aim of the study was to evaluate the influence of physical exercise on cognitive and motor functions in various stages of Alzheimer's disease. Methods: Four databases (PubMed, Scopus, Ovid, and Cochrane Library) were searched for relevant papers published between 2012 and May 2022. The works were assessed in terms of the adopted inclusion criteria. The measures of the results were changed in the parameters assessing motor and cognitive functions. Methodological quality was assessed using the Cochrane Collaboration. This review was recorded with the Cochrane Library: CRD42022340496. The results of the database search showed 302 articles, 12 of which were included in the review. All studies have shown a significant positive effect on improving cognitive and motor functions. This systematic review revealed a beneficial effect in improving cognitive and motor functions after the application of various kinds of activities, especially in the early and mild stages of Alzheimer's disease.

Procedural Learning in Individuals with Amnestic Mild Cognitive Impairment and Alzheimer's Dementia: a Systematic Review and Meta-analysis

The notion that procedural learning and memory is spared in Alzheimer's disease (AD) has important implications for interventions aiming to build on intact cognitive functions. However, despite these clinical implications, there are mixed findings in the literature about whether or not procedural learning remains intact. This meta-analysis examines the standard mean difference of all published studies regarding procedural learning in AD dementia or amnestic Mild Cognitive Impairment (aMCI) compared to cognitively healthy older adults. Additionally, we conducted statistical equivalence analyses. Our systematic review showed that only a limited number of studies (k = 17) have compared procedural learning between individuals with aMCI or AD dementia and healthy controls. Our meta-analysis, which synthesized these studies, demonstrated that while procedural learning performance was not statistically equivalent between individuals with aMCI or AD dementia, and healthy older adults, the difference was clinically and statistically trivial. Although larger studies are needed, the present findings suggest that procedural learning does appear to remain spared in aMCI and AD dementia.

Differential Contributions of Selective Attention and Sensory Integration to Driving Performance in Healthy Aging and Alzheimer's Disease

OBJECTIVES

Patients with Alzheimer's disease (AD) demonstrate deficits in cross-cortical feature binding distinct from age-related changes in selective attention. This may have consequences for driving performance given its demands on multisensory integration. We examined the relationship of visuospatial search and binding to driving in patients with early AD and elderly controls (EC).

METHODS

Participants (42 AD; 37 EC) completed search tasks requiring either luminance-motion (L-M) or color-motion (C-M) binding, analogs of within and across visual processing stream binding, respectively. Standardized road test (RIRT) and naturalistic driving data (CDAS) were collected alongside clinical screening measures.

RESULTS

Patients performed worse than controls on most cognitive and driving indices. Visual search and clinical measures were differentially related to driving behavior across groups. L-M search and Trail Making Test (TMT-B) were associated with RIRT performance in controls, while C-M binding, TMT-B errors, and Clock Drawing correlated with CDAS performance in patients. After controlling for demographic and clinical predictors, L-M reaction time significantly predicted RIRT performance in controls. In patients, C-M binding made significant contributions to CDAS above and beyond demographic and clinical predictors. RIRT and C-M binding measures accounted for 51% of variance in CDAS performance in patients.

CONCLUSIONS

Whereas selective attention is associated with driving behavior in EC, cross-cortical binding appears most sensitive to driving in AD. This latter relationship may emerge only in naturalistic settings, which better reflect patients' driving behavior. Visual integration may offer distinct insights into driving behavior, and thus has important implications for assessing driving competency in early AD. (JINS, 2018, 24, 486-497).

Musical dual-task training in patients with mild-to-moderate dementia: a randomized controlled trial

BACKGROUND/AIMS

Dual-task training may improve dual-task gait performance, balance, and cognition in older adults with and without cognitive impairment. Although music has been widely utilized in dementia management, there are no existing protocols for music-based dual-task training. This randomized controlled study developed a Musical Dual-Task Training (MDTT) protocol that patients with dementia can use to practice walking and making music simultaneously, to enhance attention control in patients during dual-tasking.

METHODS

Twenty-eight adults diagnosed with mild-to-moderate dementia were assigned to the MDTT (n=15) or control groups (n=13). The MDTT group received MDTT, while the control group participated in non-musical cognitive and walking activities. The effects of MDTT were evaluated through the primary outcome of attention control, and secondary outcomes of dual-task performance, balance, falls efficacy, and agitation.

RESULTS

The MDTT group showed a significant improvement in attention control, while the control group did not (P<0.001). A significant effect favored MDTT over control treatment for the secondary outcome of falls efficacy (P=0.02) and agitation (P<0.01).

CONCLUSION

MDTT, a music therapy intervention that demands a high level of cognitive processing, enhances attention control, falls efficacy, and helps alleviate agitation in patients with mild-to-moderate dementia.

Cholinergic modulation of the hippocampal region and memory function

Acetylcholine (ACh) plays an important role in memory function and has been implicated in aging-related dementia, in which the impairment of hippocampus-dependent learning strongly manifests. Cholinergic neurons densely innervate the hippocampus, mediating the formation of episodic as well as semantic memory. Here, we will review recent findings on acetylcholine's modulation of memory function, with a particular focus on hippocampus-dependent learning, and the circuits involved. In addition, we will discuss the complexity of ACh actions in memory function to better understand the physiological role of ACh in memory. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.

Within-session and one-week practice effects on a motor task in amnestic mild cognitive impairment

Practice effects on neuropsychological tests, which are improvements in test scores due to repeated exposure to testing materials, are robust in healthy elders, but muted in older adults with cognitive disorders. Conversely, few studies have investigated practice effects on motor tasks involving procedural memory, particularly across test-retest periods exceeding 24 hours. The current study examined one-week practice effects on a novel upper extremity motor task in 54 older adults with amnestic mild cognitive impairment. Results indicate that these individuals with primary memory deficits did improve on this motor task within a brief training session as well as across one week. These practice effects were unrelated to demographic characteristics or global cognition. One-week practice effects were, however, negatively related to delayed memory function, with larger practice effects being associated with poorer delayed memory and potentially better visuospatial ability. The presence of longer term practice effects on a procedural motor task not only has implications for how longitudinal assessments with similar measures involving implicit memory might be interpreted, but may also inform future rehabilitative strategies for patients with more severe declarative memory deficits.

Strategic Variations in Fitts' Task: Comparison of Healthy Older Adults and Cognitively Impaired Patients

The present study aimed at investigating how healthy older adults (HOA) and cognitively impaired patients (CIP) differ in a discrete Fitts' aiming task. Four levels of task difficulty were used, resulting from the simultaneous manipulation of the size of the target and its distance from home position. We found that movement times (MTs) followed Fitts' law in both HOA and CIP, with the latter being significantly slower and more affected by increased task difficulty. Moreover, correlation analyses suggest that lower information processing speed (IPS) and deficits in executive functions (EFs) are associated with decline of sensorimotor performance in Fitts' task. Analyses of strategic variations showed that HOA and CIP differed in strategy repertoire (which strategies they used), strategy distribution (i.e., how often they used each available strategy), and strategy execution (i.e., how quick they were with each available strategy). These findings further our understanding of how strategic variations used in a sensorimotor task are affected by cognitive impairment in older adults.

Learning in Alzheimer's disease is facilitated by social interaction

Seminal work in Gary Van Hoesen's laboratory at Iowa in the early 1980s established that the hallmark neuropathology of Alzheimer's disease (AD; neurofibrillary tangles) had its first foothold in specific parts of the hippocampal formation and entorhinal cortex, effectively isolating the hippocampus from much of its input and output and causing the distinctive impairment of new learning that is the leading early characteristic of the disease (Hyman et al., 1984). The boundaries and conditions of the anterograde memory defect in patients with AD have been a topic of intense research interest ever since (e.g., Graham and Hodges, 1977; Nestor et al., 2006). For example, it has been shown that patients with AD may acquire some new semantic information through methods such as errorless learning, but learning under these conditions is typically slow and inefficient. Drawing on a learning paradigm (a collaborative referencing task) that was previously shown to induce robust and enduring learning in patients with hippocampal amnesia, we investigated whether this task would be effective in promoting new learning in patients with AD. We studied five women with early-stage AD and 10 demographically matched healthy comparison participants, each interacting with a familiar communication partner. AD pairs displayed significant and enduring learning across trials, with increased accuracy and decreased time to complete trials, in a manner indistinguishable from healthy comparison pairs, resulting in efficient and economical communication. The observed learning here most likely draws on neural resources outside the medial temporal lobes. These interactive communication sessions provide a potent learning environment with significant implications for memory intervention.

Individualized skills training program for community-dwelling adults with mild Alzheimer's disease

The increasing incidence of Alzheimer's disease (AD) has created an enormous challenge to nurses. Nonpharmacological interventions that promote functional independence at home are vital to improving quality of life for individuals with AD and their caregivers. The purpose of this study was to explore the effectiveness of a skills training program for individuals with mild AD in the home setting. Although none of the participants achieved total independence in performing the meal task, all decreased their need for task prompting. The goal for this population may be to preserve and encourage a more functional state rather than to achieve total independence.

Impaired acquisition of a mirror-reading skill in Alzheimer's disease

Several studies using the mirror-reading paradigm have shown that procedural learning and repetition priming may be preserved in the early stages of Alzheimer's disease (AD) (e.g., Deweer et al., 1994). According to the classical interpretation, improved reading time for repeated words is sustained by a repetition priming effect, while procedural learning is demonstrated when this improvement is also observed for new words. Following Masson (1986), the hypothesis tested in the present study was that improved reading of new words could also be due to a repetition priming effect rather than to the acquisition of a mirror-reading skill. Indeed, because the same letters are presented throughout the task, a repetition priming effect for the letters could suffice to explain the improvement in performance. To test this hypothesis, we administered to 30 healthy young and elderly subjects and to 30 AD patients a new mirror-reading task in two phases: an acquisition phase comprising pseudo-words constructed with one part of the alphabet, and a test phase in which both pseudo-words constructed with the same part of the alphabet and pseudo-words constructed with another part of the alphabet were presented. If the new pseudo-words composed with repeated letters were read faster, it would reflect a repetition priming effect; if pseudo-words composed of 'new' letters were read faster, it would reflect a procedural learning effect. The results show comparable repetition priming effects in AD patients and in healthy elderly subjects, whereas only healthy subjects showed a procedural learning effect. These results suggest, contrary to previous studies, that the learning of a new perceptual skill may not always be preserved in AD.

Effects of motor practice on cognitive disorders in older adults

The demographics of our societies have changed drastically during the past few decades. The general population is aging rapidly as human life spans continue to expand and more adults are set to mature during the next quarter century. This aging process has numerous implications for the way we live and will have particularly important impacts on health and healthcare. In particular, substantial evidence suggests that cognitive–motor function deteriorates considerably as the result of inactive life style, biological aging, and cognitive impairments. The number of individuals with Alzheimer's disease (AD), an aging-related cognitive disorder, is expected to increase significantly during the next 40 years. The development of mild cognitive impairment (MCI) or AD can exaggerate the functional declines observed in cognitive or motor performance. The functional declines affect an array of social, cognitive, mental, physical, and motor activities in our daily lives. However, recent studies suggest that cognitive, physical, motor practice, or skill learning can improve motor speed, smoothness, and accuracy in both MCI and AD patients and their age-matched healthy peers. From theoretical and practical perspectives, this paper addresses several critical aspects of motor deficits and the kinematical characteristics of motor skill development in MCI and AD populations. Empirical data will be presented relative to the sensory–motor functions of MCI and AD, the motor skill acquisition, exercise rehabilitation in older adults with memory loss, as well as the implications for therapies. Finally, this review concludes with thoughts and suggestions for future research in these areas.

Alzheimer's disease and implicit memory

Specific neuropsychiatric disorders, such as Alzheimer's disease (AD) affect some forms of memory while leaving others relatively intact. In this review, we investigate particularities of the relationship between explicit and implicit memories in AD. It was found that implicit memory is preserved in AD, irrespective of the task used; in other words, there was not interference from explicit memory. In addition, it was verified that is possible through implicit memory compensatory strategies such as, activities of daily living (ADL) to compensate for the explicit memory deficits. In this sense, cognitive rehabilitation (CR) demonstrates reasonable results in the process of compensation of explicit memory deficits. Concluding, the decline in explicit memory suggests that both systems are functionally independent even if the other is compromised. We expect that when explicit memory system is not involved in competition with the implicit system, the final effect of learning is better, because all of the implicit memory capacity is engaged in learning and not in competition with the explicit system.

Alzheimer's disease and mild cognitive impairment deteriorate fine movement control

Sensory-motor dysfunctions are often associated with Alzheimer's disease (AD) or mild cognitive impairment (MCI). This study suggests that deterioration in fine motor control and coordination characterizes sensory-motor deficiencies of AD and MCI. Nine patients with a clinical diagnosis of probable AD, 9 amnestic MCI subjects and 10 cognitively normal controls performed four types of handwriting movement on a digitizer. Movement time and smoothness were analyzed between the groups and across the movement patterns. Kinematic profiles were also compared among the groups. AD and MCI patients demonstrated slower, less smooth, less coordinated, and less consistent handwriting movements than their healthy counterparts. The theoretical relevance and practical implications of fine motor tasks, such as these movements involved in handwriting, are discussed relative to the deteriorated sensory-motor system of AD and MCI patients.

Nonpharmacological cognitive interventions in aging and dementia

There have been increasing efforts to develop cognitive interventions to ameliorate cognitive problems experienced by older adults. In healthy elderly populations, cognitive training has centered on the enhancement of memory and speed of processing, with the goal of maximizing current function and reducing the risk of cognitive decline. Among elderly persons with nonprogressive neurological conditions such as traumatic brain injury (TBI) and stroke, there has been an emphasis on rehabilitation to help restore function. Most recently, there has been increased attention on the development of new cognitive techniques to treat persons with progressive neurodegenerative conditions such as Alzheimer disease. The literature is reviewed on current approaches to cognitive interventions in elderly healthy populations, and a particular emphasis is placed on the most recent strides in progressive neurocognitive conditions, particularly Alzheimer disease. Important issues such as study design, the use of ecologically and functionally valid outcome measures, the need to examine heterogeneous populations and cross-cultural variables, and the incorporation of technologically based systems are examined. It is concluded that cognitive interventions in the elderly show considerable promise and deserve further study.

Spaced Retrieval for Enhancing Memory: Implications for Nursing Practice and Research

Many older adults experience memory problems due to normal or pathological aging, which impairs daily functioning. Spaced Retrieval is a technique that can be used to augment memory function as it relates to a specific, everyday task. This technique requires individuals to recall a single piece of information over progressively longer periods until the information is consolidated into long-term memory. It works effectively in various settings and for individuals with memory problems. Given their direct contact with older adult patients, nurses are in a position to notice memory declines and guide their patients in the use of this technique.

Motor-skill learning in Alzheimer's disease: a review with an eye to the clinical practice

Since elderly people suffering from dementia want to go on living independently for as long as possible, they need to be able to maintain familiar and learn new practical skills. Although explicit or declarative learning methods are mostly used to train new skills, it is hypothesized that implicit or procedural techniques may be more effective in this population. The present review discusses 23 experimental studies on implicit motor-skill learning in patients with Alzheimer's disease (AD). All studies found intact implicit motor-learning capacities. Subsequently, it is elaborated how these intact learning abilities can be exploited in the patients' rehabilitation with respect to the variables 'practice' and 'feedback.' Recommendations for future research are provided, and it is concluded that if training programs are adjusted to specific needs and abilities, older people with AD are well able to (re)learn practical motor skills, which may enhance their autonomy.

Practice effects on motor control in healthy seniors and patients with mild cognitive impairment and Alzheimer's disease

This research was designed to test the hypothesis that motor practice can enhance the capabilities of motor control in healthy controls (NC) and patients with a diagnosis of probable Alzheimer's disease (AD) and mild cognitive impairment (MCI), and consequently results in better motor performance. Approximately half of the subjects in the NC (n = 31), AD (n = 28), and MCI (n = 29) either received or did not receive practice on a task of fast and accurate arm movement with a digitizer. Changes in movement time (MT), movement smoothness (jerk), and percentage of primary submovement (PPS) were recorded and compared among the three groups across six blocks of trials (baseline and five training sessions). For all subjects, practice improved motor functions as reflected by faster and smoother motor execution, as well as a greater proportion of programming control. Compared to unaffected matched controls, AD and MCI subjects exhibited a greater reduction in movement jerk due to practice. Movement time and PPS data revealed that motor practice appeared to reduce the use of "on-line" correction adopted by the AD or MCI patients while performing the aiming movements. Evidently, their arm movements were quicker, smoother, and temporally more consistent than their untrained peers. The findings of this study shed light on how MCI and AD may affect motor control mechanisms, and suggest possible therapeutic interventions aimed at improving motor functioning in these impaired individuals.

Progressive cognitive decline in a transgenic mouse model of Alzheimer's disease overexpressing mutant hAPPswe

The possibility of detecting progressive changes in cognitive function reflecting the spatio-temporal pattern of beta-amyloid peptide (Abeta) deposition was investigated in Tg2576 mice overexpressing the human mutant amyloid precursor protein (hAPP). Here, we show that at 7 months of age, Tg2576 mice exhibited a selective deficit in hippocampus-based operations including a defective habituation of object exploration, a lack of reactivity to spatial novelty and a disruption of allothetic orientation in a cross-shaped maze. At 14 months of age, Tg2576 mice displayed a more extended pattern of behavioral abnormalities, because they failed to react to object novelty and exclusively relied on motor-based orientation in the cross-shaped maze. However, an impaired reactivity to spatial and object novelty possibly reflecting age-related attention deficits also emerged in aged wild-type mice. These findings further underline that early cognitive markers of AD can be detected in Tg2576 mice before Abeta deposition occurs and suggest that as in humans, cognitive deterioration progressively evolves from an initial hippocampal syndrome to global dementia because of the combined effect of the neuropathology and aging.

Memory for emotional stimuli in patients with Alzheimer's disease

Although a hallmark of Alzheimer's disease (AD) is memory impairment, there is speculation that recall may be enhanced when an emotional component is associated with an event. The current study aims to assess whether patients with AD would recall emotionally laden material better than neutral stimuli. DSM-IV-diagnosed AD patients with mild to moderate dementia, as well as groups of young and elderly healthy controls, participated in this study. All subjects were administered three word lists for three trials each. The words were positive, negative, or neutral in valence and matched for concreteness, emotionality, and pleasantness. As expected, the controls performed significantly better than the AD patients. Importantly, the pattern of recall for the emotions was different, such that both control groups recalled all emotions equally, whereas the AD patients recalled significantly more negative words than positive or neutral. These findings of improved immediate memory for emotional material in AD lends support to the notion that mnemonic functions are differentially affected in the disease.

MR spectroscopy in Alzheimer's disease: gender differences in probabilistic learning capacity

Degenerative alterations of cortical and subcortical regions in Alzheimer disease (AD) can be estimated by the extent of brain metabolite changes as measured by magnetic resonance spectroscopic imaging (MRSI). A neuropsychological assessment may correlate with metabolite levels and could evaluate underlying degenerative processes. Probabilistic-related classification learning, which represents one form of procedural learning, is associated with the neostriatum. The present study was aimed at examining the correlation of spectroscopic imaging in subcortical regions with the evaluation of specific neuropsychological findings. Twenty-two patients with Alzheimer's disease were compared to 15 healthy elderly control subjects. Proton MRSI of the basal ganglia (BG) and thalamus region was performed for detection of N-acetylaspartate (NAA), trimethylamine (TMA) and creatine ((P)Cr). In addition, a probabilistic-related classification learning task (Weather Prediction Task (WT)) was applied. We observed that in patients a high TMA signal in the basal ganglia region was correlated with a poorer performance in the probabilistic learning task (Spearman rank order correlation (SROC)=-0.6, P<0.009). Although Alzheimer's patients, as a group, did not differ from controls with regard to probabilistic learning capacity (PLC), male AD patients, as compared to male controls, displayed an impairment in the task performance by 28% (P<0.03) and showed a 16% elevation in TMA signaling (P<0.04). The altered metabolite signals and ratios in combination with the cognitive performance might suggest gender-related neuronal degeneration and dysfunction within subcortical regions in AD.

An electronic memory aid to support prospective memory in patients in the early stages of Alzheimer's disease: a pilot study

The use of an electronic memory aid (EMA) for patients with mild-to-moderate probable Alzheimer disease is examined in five outpatients aged 58-79 years. The ability to remember to carry out seven tasks at a particular time was evaluated in three experimental conditions: recall without an external memory aid, recall with a written list and recall with support available from an EMA. The use of an EMA significantly improved patients' prospective memory, while the written list and free recall were not useful. Future research that examines the value of using an EMA to help with tasks that are associated with prospective memory with a larger sample of patients within their own home context is suggested.

Memory rehabilitation in Alzheimer's disease: a review of progress

BACKGROUND

Memory rehabilitation is a sadly misrepresented area of applied research in Alzheimer's disease.

OBJECTIVES

To gather and evaluate recent evidence for the clinical effectiveness or ecologically validity of memory rehabilitation for mild to moderate Alzheimer's patients.

METHODS

Computerised searches and some handsearching were conducted spanning the last five years, from 1995 to 2000, inclusively. Criteria for inclusion in this overview involved the use of a precise memory rehabilitation technique within an experimental study design applied to Alzheimer's patients with pre- and post-treatment evaluation.

FINDINGS

Three potential levels of memory rehabilitation procedures with proven clinical or pragmatic efficacy were identified. The first level bears on the facilitation of residual explicit memory with structured support both at encoding and at subsequent recall; the second level of memory rehabilitation exploits the relatively intact implicit memory system (priming and procedural memory); the last deals with finding ways of coping with the patient's limited explicit memory capacities through the use of external memory aids. A proposal of suggestions for good practice and future research in memory rehabilitation is also offered with the hope to spur further development in this rapidly expanding area of applied research.

CONCLUSION

The available evidence shows that alternative and innovative ways of memory rehabilitation for Alzheimer's patients can indeed be clinically effective or pragmatically useful with a great potential for use within the new culture of a more graded and proactive type of Alzheimer's disease care.

The canine as a model of human cognitive aging: recent developments

1. Aged dogs display many of the cognitive impairments associated with aging and dementia. 2. Aged dogs, like humans, display a wide range of individual variability in cognitive functioning (i.e., different cognitive functions decline at different rates in aged dogs). 3. Different categories of aged canines can be identified on the basis of neuropsychological test performance, and these categories can be used to model different subgroups of aged humans (i.e., dementia, mild cognitive impairment and successful aging). 4. Additional research is required to further validate the dog as a model of human cognitive aging and dementia.

Age-related working memory deficits in the allocentric place discrimination task: possible involvement in cholinergic dysfunction

It is well known that learning and memory ability declines with aging. Age-related long-term changes in learning and memory ability in rats were investigated with the place navigation task and the allocentric place discrimination task (APDT) in a water maze using the same animals for each task. In a working memory place navigation task, aged animals could learn the location of the platform as well as when they were young, although strategy shifts were observed. In contrast, accuracy in the APDT significantly declined from 90% to 65% with aging. This impairment was ameliorated by an acetylcholine esterase inhibitor physostigmine at 22-23 months old. No amelioration was, however, detected in the same animals tested when they further aged to 26-27 months old. These results suggest that the APDT performance is sensitive to age-related memory deficits and that this may be due to the cholinergic dysfunction.