轻度认知障碍

1引言1．1背景轻度认知障碍,尤其是在患者自己报告时,向临床医生提出了实质性的挑战。医生们可能在处理某一轻度或短暂性疾病、某种药物引起的不良反应或某种抑郁症的患者时,该患者可能处于最终将导致     

Mild cognitive impairment subtypes and vascular dementia in community-dwelling elderly people: a 3-year follow-up study

OBJECTIVES: To investigate whether mild cognitive impairment (MCI) with multiple impaired cognitive domains (mcd-MCI) is a prodromal manifestation of vascular dementia (VaD). DESIGN: Prospective cohort study. SETTING: Geriatric unit of the Ospedale Maggiore Istituto di Ricovero e Cura a Carattere Scientifico, Milan, Italy. PARTICIPANTS: Four hundred community-dwelling subjects aged 65 and older who came freely to the geriatric unit as part of a comprehensive geriatric assessment program were evaluated for memory impairment or other cognitive disorders. Subjects with MCI were kept under observation for 3 years. MEASUREMENTS: Subjects with MCI were studied by applying a standardized clinical evaluation and a conducting a computed tomography brain scan. Cognitive performance was assessed using the Mini-Mental State Examination, the Clock Drawing Test, and a comprehensive battery of neuropsychological tests. Cardiovascular comorbidity was assessed on the basis of medical history and using electrocardiography, echocardiography, and carotid color Doppler ultrasound. RESULTS: MCI was found in 65 of the 400 community-dwelling subjects; 31 were classified with amnestic MCI (a-MCI) and 34 with mcd-MCI. A dysexecutive syndrome characterized people with mcd-MCI, who had significantly more vascular comorbidity and signs of vascular disease on brain imaging as well as a higher prevalence of extra pyramidal features, mood disorders, and behavioral symptoms than people with a-MCI. Twenty of the 65 subjects with MCI (31%) progressed to dementia within 3 years of follow-up: 11 subjects with Alzheimer's disease (AD) and nine with VaD. All patients who evolved to AD had been classified with a-MCI at baseline, whereas all patients who evolved to subcortical VaD had been classified with mcd-MCI at baseline. CONCLUSION: All subjects who converted to subcortical VaD had been classified with mcd-MCI, suggesting that mcd-MCI might be an early stage of subcortical VaD.     

Memory complaints in 200 subjects meeting the diagnostic criteria for age-associated memory impairment: psychoaffective and cognitive correlates

We studied 200 subjects recruited by general practioners and meeting the seminal criteria for the age-associated memory impairment construct (AAMI). These criteria did not allow to select an homogeneous population. Three groups could be distinguished. First, 18 subjects had apparent psychoaffective disturbances, mainly related to anxiety. Second, 41 subjects had lower memory performance than the other subjects and could be classified as severe AAMI or late-life forgetfulness, former constructs similar to the present construct of mild cognitive impairment (MCI). A large majority of subjects (n -/+ 141) had no apparent psychoaffective disturbances and normal memory performance. They could correspond to the proper AAMI construct. Actually, two subgroups could be distinguished in these subjects. Half of them had low cognitive complaints, assessed by the cognitive difficulties scale, compared to those formerly found in a population of 1349 subjects aged over 50, studied by GP, but not specifically recruited on the presence of memory complaints. These subjects could be considered as quite normal subjects. The other half of AAMI subjects had higher scores of memory complaints and more psychoafective disturbances than the subjects of the first group. No relationship was found between subjective complaints and memory performance in the total population as well as in any subgroup. The main correlate of memory complaints was the score on the Zung anxiety scale in the total population, the LLF and the AAMI groups. This study do not support the existence of a specific category of aged subjects intermediate between normal subjects without subjective memory decline and patients with MCI or incipient Alzheimer's disease. Memory complaints appear to be related to psychoaffective disturbances even in subjects with low memory performance.     

轻度认知功能障碍向阿尔茨海默病转化的预测研究进展

轻度认知功能障碍（MCI）是介于正常衰老与痴呆之间的认知功能缺损状态,MCI进展为阿尔茨海默病（AD）的危险性较高,故MCI阶段可能是进行AD预防性治疗的最合适阶段,因而成为研究的焦点。本文就近年来MCI向AD的转化预测研究做一综述,主要包括五个方面：神经心理学测试、生物标志物检查、神经影像学检查、脑电生理学检查及其治疗进展。     

部队老年人轻度认知损害的发生及向Alzheimer病的转化情况

目的调查部队老年人轻度认知损害（MCI）的发病率及向Alzheimer病（AD）的转化率，为进一步研究AD提供依据。方法以2001年石家庄市26个部队休干所MCI患病率调查的2674名60岁及以上的离退休干部为研究对象，对患病率调查时诊断为MCI的216例患者和2302名认知正常受试者进行为期3年的队列研究，比较MCI患者和认知正常受试者AD的平均年发病率。结果认知正常的老年人MCI的发病率为4．8％（人年），AD的平均年发病率为0．8％（人年）；MCI患者AD的平均年发病率为5．6％（人年）；男性和女性MCI患者AD的平均年发病率差别无统计学意义（P〉0．05）；随着文化程度的提高，MCI患者AD的平均年发病率有降低的趋势（P〈0．05）；而随着年龄的增长，MCI患者AD的平均年发病率有增高的趋势（P〈0．01）。MCI转化为AD的相对危险性为认知正常者的7．4倍。结论军队老年MCI患者转化为AD的危险性远远大于认知正常的老年人，应加强对老年MCI患者这一AD高危人群的监测。     

Vascular mild cognitive impairment: concept, definition, and directions for future studies

Vascular mild cognitive impairment (vascular MCI) describes an abnormal condition which is caused by vascular diseases and in which the patient presents with cognitive deficits not severe enough to fit the criteria for dementia (i.e., basic functional autonomy is not lost). As in neurodegenerative MCI, the clinical, neuroimaging, and natural history features of vascular MCI are currently under definition. It is particularly important to identify cognitive impairment of vascular origin during the early stages, as its progression may be slowed or halted by intervening with aggressive treatment of vascular risk factors and diseases. Longitudinal studies on the natural history of vascular MCI, with investigation of the factors responsible for the transition to dementia, are worthy of being planned and carried out.     

QT dispersion and heart rate variability abnormalities in Alzheimer's disease and in mild cognitive impairment

OBJECTIVES: To investigate the effect of cardiovascular changes (i.e., QT interval, QT dispersion (QTD), heart rate variability (HRV), and other cardiovascular measures) in subjects with Alzheimer's disease (AD) and mild cognitive impairment (MCI). DESIGN: Each subject underwent clinical and cognitive examination, a structural brain imaging study, echocardioDoppler, electrocardiogram (ECG), HRV analysis using 24-hour ECG monitoring, and 24-hour blood pressure monitoring. SETTING: Community population-based sample of patients admitted to an AD center for investigation of cognitive disturbances. PARTICIPANTS: Thirty-three subjects with AD, 39 subjects with MCI, and 29 cognitive healthy subjects (controls) matched for demographic characteristics, hypertensive condition, smoking habits, and laboratory parameters were enrolled consecutively. MEASUREMENTS: Clinical and cognitive examination, structural brain imaging study, echocardioDoppler, ECG, HRV analysis using 24-hour ECG monitoring, and 24-hour blood pressure monitoring. RESULTS: QTD and QT corrected dispersion mean values were significantly higher in patients with AD than in patients with MCI and controls and higher in patients with MCI than in controls. HRV time and domain parameters were lower in patients with AD than in patients with MCI and controls. No difference in other cardiovascular measures was found. QTD and HRV were found to be significantly correlated with the degree of cognitive impairment. CONCLUSION: These findings support the presence of a peculiar neuroanatomic dysfunction in patients with AD and MCI that parallels the disease progression. These noninvasive parameters might prove to be powerful predictive tools in the worsening of cognitive function and mortality risk.     

Neuropsychological and genetic differences between age-associated memory impairment and mild cognitive impairment entities

OBJECTIVE: To neuropsychologically and genetically compare age-associated memory impairment (AAMI) and mild cognitive impairment (MCI) entities and to determine what proportion of AAMI diagnosed individuals could also receive a MCI diagnosis. To compare the distribution of a previously known genetic risk factor for Alzheimer's disease (apolipoprotein E common polymorphism) associated with these two conditions with a sample of the normal aging. DESIGN: Neuropsychological and genetic assessments in AAMI and MCI individuals. Genetic assessment in AAMI, MCI, and control subjects. SETTING: General health centers and geriatric homes from northeastern Spain (Catalunya). PARTICIPANTS: One hundred and four subjects presenting subjective memory complaints were selected and the AAMI and MCI criteria were applied. One hundred and twenty-four healthy Spanish subjects age 50 and older were defined as controls. MEASUREMENTS: Memory, language, and frontal lobe functions were assessed using standard neuropsychological tests. The apolipoprotein E (apo E) polymorphism was obtained by using polymerase chain reaction (PCR) and HhaI restriction endonuclease. RESULTS: Sixty-seven percent of previously diagnosed AAMI individuals could also be identified as MCI subjects. These MCI cases differed from those only-AAMI individuals both in neuropsychological and genetic analyses, performing worse not only on memory but also on language and frontal lobe tests and presenting high and low prevalences of the apo E epsilon 3/epsilon 4 and epsilon 3/epsilon 3 genotypes, respectively. The general AAMI sample of 93 individuals also differed from controls in the apo E genotype and allele distributions but these differences were no longer present after subtracting the MCI cases (63 subjects). These findings reflect that the differences between the memory impaired sample and the control sample regarding the apo E polymorphism were mainly attributable to MCI individuals and not to those who received only a diagnosis of AAMI alone. CONCLUSIONS: Our findings suggest that among AAMI subjects, those who also fulfill the MCI criteria present a neuropsychological and genetic profile closer to that previously related to Alzheimer's disease than those individuals only eligible for a diagnosis of AAMI. However, our findings also suggest that using only the AAMI criteria still appears to select a population that differs genetically from the normal older population.     

脑白质疏松伴轻度认知功能障碍患者的弥散张量成像研究

目的研究脑白质疏松(LA)伴有轻度认知功能障碍(MCI)患者的脑白质弥散张量成像(DTI),分析LA伴MCI患者早期脑白质微观结构的变化与临床表现之间的关系。方法选取LA伴MCI患者31例(病例组),另选健康体检者27例(对照组),2组行常规头颅MRI及DTI扫描,并进行认知及心理检查,最后采用基于纤维束的空间统计方法分析2组之间部分各向异性(FA)值的差异。结果与对照组比较,病例组右侧新纹状体、内囊前肢、额叶眶皮质及深部白质,左侧中央前回、中央旁小叶及深部白质区域的FA值明显下降,差异有统计学意义(P<0.05)。结论 LA伴MCI患者的右侧新纹状体、内囊前肢、额叶眶皮质及深部白质,左侧中央前回、中央旁小叶及深部白质区域的白质纤维的完整性受到损害,且这些部位的损伤与患者的临床表现包括认知功能障碍、运动功能下降及泌尿功能障碍有关。     

Mild cognitive impairment as a diagnostic entity

The concept of cognitive impairment intervening between normal ageing and very early dementia has been in the literature for many years. Recently, the construct of mild cognitive impairment (MCI) has been proposed to designate an early, but abnormal, state of cognitive impairment. MCI has generated a great deal of research from both clinical and research perspectives. Numerous epidemiological studies have documented the accelerated rate of progression to dementia and Alzheimer's disease (AD) in MCI subjects and certain predictor variables appear valid. However, there has been controversy regarding the precise definition of the concept and its implementation in various clinical settings. Clinical subtypes of MCI have been proposed to broaden the concept and include prodromal forms of a variety of dementias. It is suggested that the diagnosis of MCI can be made in a fashion similar to the clinical diagnoses of dementia and AD. An algorithm is presented to assist the clinician in identifying subjects and subclassifying them into the various types of MCI. By refining the criteria for MCI, clinical trials can be designed with appropriate inclusion and exclusion restrictions to allow for the investigation of therapeutics tailored for specific targets and populations.     

Conversion of mild cognitive impairment to dementia in elderly subjects: a preliminary study in a memory and cognitive disorder unit

Prevalence and incidence of predementia syndromes vary as a result of different diagnostic criteria, as well as different sampling and assessment procedures. Mild cognitive impairment (MCI) is thought to be a prodromal phase of dementia and therefore highly predictive of subsequent conversion. The aim of our study was to investigate the risk of conversion to dementia for different MCI subtypes diagnosed according to standardized and recently revised criteria (amnestic; impairment of memory plus other cognitive domains; nonamnestic). Participants were recruited among the 2,866 patients referring to the Memory and Cognitive Disorders Unit of the Local Health Unit of Bologna, Maggiore Hospital, between October 2000 and February 2006. In this preliminary study we analyzed data from 52 elderly outpatients with a diagnosis of MCI and a mean follow-up of 1.21+/-0.61 years (range 0.23-3.10 years). Mean age was 72.8+/-6.6 years, males were 61.5%. Mean baseline mini mental state examination (MMSE) score was 27.1+/-1.5. There were 15 incident cases of dementia (28.8%), with Alzheimer's disease (AD) accounting for 53.3% of all cases, AD with cerebrovascular disease for 33.4% and fronto-temporal dementia for 13.3%. Overall rate of conversion was 23.8 per 100 person-years. During the same follow-up period, 53.8% of participants remained stable and 17.3% reverted to normal. Rates of conversion for the specific MCI subtypes were 38 per 100 person-years for amnestic MCI, 20 per 100 person- years for non-amnestic MCI, and 16 per 100 person-years for memory plus other cognitive domains MCI. With respect to non-converters, converters were generally older (76.1+/-4.2 vs. 71.5+/-7.0 years, p=0.021), had a lower MMSE score (26.4+/-1.66 vs. 27.4+/-1.4, p=0.035) and a higher prevalence of atrophy at neuroimaging (73.7% vs. 42.4%, p=0.047). Moreover, with respect to non-converters, converters tended to have higher serum high density lipoprotein (HDL) levels, and lower serum folate levels. No difference was observed for the other study variables, included MCI subtype. Our findings suggest that the current definitions for MCI subtypes, particularly those referring to individuals with multiple or non-amnestic cognitive impairment, include a substantial number of individuals who may not progress to dementia. The possible role of cortical atrophy and low folate in the conversion from MCI to dementia could have important implications, because both conditions are easily identifiable. Moreover, low folate status is potentially amenable to therapeutic options. Although discouraging with respect to the clinical usefulness of currently available MCI criteria, our results raise the possibility that defining a protocol of multiple clinical risk factors may be useful in identifying MCI individuals at increased risk of conversion.     

Possible therapeutic value of melatonin in mild cognitive impairment: a retrospective study

Mild cognitive impairment (MCI) is an etiologically heterogeneous syndrome characterized by cognitive impairment preceding dementia. Approximately 12% of MCI patients convert to Alzheimer's disease (AD) or other dementia disorders every year. In the present report we retrospectively examined the initial and final neuropsychological assessment of 50 MCI outpatients, 25 of whom had received daily 3-9 mg of a fast-release melatonin preparation p.o. at bedtime for 9-18 months. Melatonin was given in addition to the standard medication prescribed by the attending psychiatrist. Patients treated with melatonin showed significantly better performance in Mini Mental State Examination and the cognitive subscale of the Alzheimer's Disease Assessment Scale. After application of a battery of neuropsychological tests including Mattis' test, Digit-symbol test, Trail A and B tasks and the Rey's verbal test, better performance was found in melatonin-treated patients, except for the Digit-symbol test score which remained unchanged. Abnormally high Beck Depression Inventory scores decreased in melatonin-treated patients, concomitantly with an improvement in wakefulness and sleep quality. The results suggest that melatonin can be a useful add-on drug for treating MCI in a clinical setting.     

Mild cognitive impairment: what's in a name?

BACKGROUND: Nowadays the term mild cognitive impairment (MCI) is used to fill the gap between cognitive changes associated with normal ageing and those associated with dementia. Despite some agreement in general definitions, MCI is still a heterogeneous clinical syndrome for which no DSM-IV criteria have yet been established. Criteria by Petersen et al. are presently the most applied in clinical practice. Moreover, little attention has been paid to the specific relation between MCI and depression. OBJECTIVE: This review highlights some concerns about the concept of MCI and provides guidelines within the field of neuropsychology to solve them. In a second part, the paper focuses on the specific relationship between depression in the elderly and MCI. RESULTS: We hypothesize that certain test instruments can be used to operationalize the criteria proposed by Petersen et al. Moreover, we suggest that cued recall might be of help to differentiate between progressive and non-progressive MCI. Concerning the specific relation between depression and MCI, we assume that elderly depression with concomitant cognitive problems can be seen as an MCI. CONCLUSION: The proposed adjustments and additions (neuropsychological instruments and the incorporation of depressive symptoms) in the diagnostic flowchart of Petersen may serve as useful tools for clinicians when making a diagnosis of MCI.     

Subjective memory complaints, neuropsychological performance and psychiatric variables in memory clinic attendees: A 3-year follow-up study

The aims were to evaluate the cognitive performance and clinical diagnosis in patients (<75 years) seeking help for subjective memory complaints, to determine the prevalence of certain psychiatric symptoms and to conduct follow-up examinations. At baseline 41% showed normal cognitive performance (subjective memory impairment; SMI), 37% fulfilled criteria for mild cognitive impairment (MCI) and 22% were classified as dementia. There were significant associations between the three groups and experiences of psychosocial stress and feelings of anxiety. The proportion of psychosocial stress was significantly higher in SMI vs. MCI and SMI vs. dementia. Feelings of anxiety were significantly higher in SMI vs. MCI. At the 3-year follow-up, 88% of the SMI patients remained stable SMI and 60% of the MCI patients remained stable. There was a significant reduction of psychosocial stress and moderate reduction of feelings of anxiety among the SMI patients. The findings indicate that the risk of patients with SMI developing dementia is small within a 3-year span. We propose that subjective memory complaints might be influenced by the presence of psychosocial stress and feelings of anxiety disturbing the memory processes and interfering with the patients’ evaluation of their memory function.     

Encephalopathy and neuropathy in end-stage liver disease before and after liver transplantation.

The nervous system involvement of 8 patients with end-stage liver disease was evaluated by means of clinical neurological, neuropsychological, neurophysiological and neuroradiological investigation before and 6-12 months after a successful liver transplantation. Preoperatively, all subjects (7 women, 1 man; mean age 40 years, range 30-54 years) exhibited decreased muscle strength and 2 patients manifested clinical signs of polyneuropathy. In neuropsychological tests, slight visuoconstructive apraxia, and disturbances of verbal memory and cognitive function were observed. Magnetic resonance imaging (MRI) revealed cerebral lesions in two patients. After transplantation, muscle strength reverted to normal in all patients, polyneuropathy improved and in all but 2 patients recovery of neuropsychological functioning was observed. Clinical signs of encephalopathy had disappeared. All patients were emotionally better adjusted after transplantation. Four subjects showed new, albeit mild changes in neurophysiological and neuropsychological tests postoperatively. We conclude that the majority of neurological impairment disappeared after liver transplantation. We want to stress that evaluation of neurological sequelae of liver transplantation needs to be based on assessments both before and after liver transplantation.     

Mild Cognitive Impairment: Incidence and Risk Factors: Results of the Leipzig Longitudinal Study of the Aged

OBECTIVES: To provide information on age‐ and sex‐specific incidence rates of mild cognitive impairment (MCI) and risk factors for incident MCI. DESIGN: Prospective longitudinal cohort. SETTING: Leipzig Longitudinal Study of the Aged, a population‐based German study of the epidemiology of dementia and mild cognitive impairment. PARTICIPANTS: At baseline, 1,692 subjects aged 75 and older were included in the sample. MEASUREMENTS: Trained psychologists and physicians conducted structured clinical interviews including neuropsychological assessment and questions about sociodemographics, familial history of dementia, activities of daily living, subjective memory impairment, and lifestyle (alcohol consumption, smoking) at participants' homes. Structured third‐party interviews were conducted with proxies. Incidence was calculated according to the person‐years‐at‐risk method. Cox proportional hazards models were used to examine the association between risk factors and incident MCI. RESULTS: During an 8‐year follow‐up period, 26.4% (n=137) of the 519 study participants (population at risk) were identified as incident MCI cases (person‐years=1,791.1). The overall incidence rate of MCI was 76.5 (95% confidence interval=64.7–90.4) per 1,000 person‐years. Older age, subjective memory impairment, impairment in instrumental activities of daily living, and antecedent lower cognitive performance were found to be significantly associated with the development of future MCI. CONCLUSION: MCI is highly incident in the elderly population. For the purpose of early detection of dementia, subjective memory impairment should be taken seriously as a possible prestage of MCI.     

Normal pressure hydrocephalus: Neurophysiological and neuropsychological aspects: a narrative review

Idiopathic normal pressure hydrocephalus (NPH) is a syndrome that affects elderly people and is characterized by excessive accumulation of cerebrospinal fluid in the brain ventricles. Diagnosis is based on the evaluation of clinical symptoms, which consists of a classic triad (Hakim triad), gait disturbances, cognitive impairment, and urinary incontinence. However, this complete triad is not always seen; therefore, it is difficult to make the diagnosis. NPH can be divided into primary or idiopathic NPH and secondary NPH. Diagnostic criteria for NPH remain a topic of discussion; however, the development of diagnostic techniques has brought new opportunities for diagnosis. The aim of this review is to present an overview of neurophysiological and neuropsychological approaches to support the clinical evaluation of patients with NPH and contribute to the differential diagnosis of NPH and dementia, as the clinical symptoms of NPH may resemble other neurodegenerative disorders.     

The Montreal Cognitive Assessment, MoCA: a brief screening tool for mild cognitive impairment

OBJECTIVES: To develop a 10-minute cognitive screening tool (Montreal Cognitive Assessment, MoCA) to assist first-line physicians in detection of mild cognitive impairment (MCI), a clinical state that often progresses to dementia. DESIGN: Validation study. SETTING: A community clinic and an academic center. PARTICIPANTS: Ninety-four patients meeting MCI clinical criteria supported by psychometric measures, 93 patients with mild Alzheimer's disease (AD) (Mini-Mental State Examination (MMSE) score > or =17), and 90 healthy elderly controls (NC). MEASUREMENTS: The MoCA and MMSE were administered to all participants, and sensitivity and specificity of both measures were assessed for detection of MCI and mild AD. RESULTS: Using a cutoff score 26, the MMSE had a sensitivity of 18% to detect MCI, whereas the MoCA detected 90% of MCI subjects. In the mild AD group, the MMSE had a sensitivity of 78%, whereas the MoCA detected 100%. Specificity was excellent for both MMSE and MoCA (100% and 87%, respectively). CONCLUSION: MCI as an entity is evolving and somewhat controversial. The MoCA is a brief cognitive screening tool with high sensitivity and specificity for detecting MCI as currently conceptualized in patients performing in the normal range on the MMSE.     

Methods to improve the detection of mild cognitive impairment

We examined whether the performance of the National Institute of Aging's Consortium to Establish a Registry for Alzheimer's Disease's 10-word list (CWL), part of the consortium's neuropsychological battery, can be improved for detecting Alzheimer's disease and related disorders early. We focused on mild cognitive impairment (MCI) and mild dementia because these stages often go undetected, and their detection is important for treatment. Using standardized diagnostic criteria combined with history, physical examination, and cognitive, laboratory, and neuroimaging studies, we staged 471 community-dwelling subjects for dementia severity by using the Clinical Dementia Rating Scale. We then used correspondence analysis (CA) to derive a weighted score for each subject from their item responses over the three immediate- and one delayed-recall trials of the CWL. These CA-weighted scores were used with logistic regression to predict each subject's probability of impairment, and receiver operating characteristic analysis was used to measure accuracy. For MCI vs. normal, accuracy was 97% [confidence interval (C.I.) 97-98%], sensitivity was 94% (C.I. 93-95%), and specificity was 89% (C.I. 88-91%). For MCI/mild dementia vs. normal, accuracy was 98% (C.I. 98-99%), sensitivity was 96% (C.I. 95-97%), and specificity was 91% (C.I. 89-93%). MCI sensitivity was 12% higher (without lowering specificity) than that obtained with the delayed-recall total score (the standard method for CWL interpretation). Optimal positive and negative predictive values were 100% and at least 96.6%. These results show that CA-weighted scores can significantly improve early detection of Alzheimer's disease and related disorders.     

Visuospatial representation in patients with mild cognitive impairment: Implication for rehabilitation

Behavioral and neurophysiological experiments have demonstrated that distinct and common cognitive processes and associated neural substrates maintain allocentric and egocentric spatial representations. This review aimed to provide evidence from previous behavioral and neurophysiological studies on collating cognitive processes and associated neural substrates and linking them to the state of visuospatial representations in patients with mild cognitive impairment (MCI). Even though MCI patients showed impaired visuospatial attentional processing and working memory, previous neuropsychological experiments in MCI largely emphasized memory impairment and lacked substantiating evidence of whether memory impairment could be associated with how patients with MCI encode objects in space. The present review suggests that impaired memory capacity is linked to impaired allocentric representation in MCI patients. This review indicates that further research is needed to examine how the decline in visuospatial attentional resources during allocentric coding of space could be linked to working memory impairment.