ABSTRACT
Clinical diagnosis of Alzheimer's disease (AD) is based on symptoms; however, the challenge is to diagnose AD at the preclinical stage with the application of biomarkers and initiate early treatment (still not widely available). Currently, cerebrospinal fluid (CSF) amyloid-ß 42 (Aß42) and tau are used in the clinical diagnosis of AD; nevertheless, blood biomarkers (Aß42 and tau) are less predictive. Amyloid-positron emission tomography (PET) imaging is an advancement in technology that uses approved radioactive diagnostic agents (florbetapir, flutemetamol, or florbetaben) to estimate Aß neuritic plaque density in adults with cognitive impairment evaluated for AD and other causes of cognitive decline. There is no cure for AD to date-the disease progression cannot be stopped or reversed; approved pharmacological agents (donepezil, galantamine, and rivastigmine; memantine) provide symptomatic treatment. However, the disease-modifying therapies are promising; aducanumab and CAD106 are in phase III trials for the early stages of AD. In conclusion, core CSF biomarkers reflect pathophysiology of AD in the early and late stages; the application of approved radiotracers have potential in amyloid-PET brain imaging to detect early AD.
ABSTRACT
Alzheimer's disease is characterized by the progressive deterioration of cognitive abilities particularly working memory while mild cognitive impairment (MCI) represents its prodrome. It is generally believed that neural compensation is intact in MCI but absent in Alzheimer's disease. This study investigated the effects of increasing task load as a means to induce neural compensation through a novel visual working memory (VSWM) task using functional near-infrared spectroscopy (fNIRS). The bilateral prefrontal cortex (PFC) was explored due to its relevance in VSWM and neural compensation. A total of 31 healthy controls (HC), 12 patients with MCI and 18 patients with mild Alzheimer's disease (mAD) were recruited. Although all groups showed sensitivity in terms of behavioral performance (i.e. score) towards increasing task load (level 1 to 3), only in MCI load effect on cortical response (as measured by fNIRS) was significant. At lower task load, bilateral PFC activation did not differ between MCI and HC. Neural compensation in the form of hyperactivation was only noticeable in MCI with a moderate task load. Lack of hyperactivation in mAD, coupled with significantly poorer task performance across task loads, suggested the inability to compensate due to a greater degree of neurodegeneration. Our findings provided an insight into the interaction of cognitive load theory and neural compensatory mechanisms. The experiment results demonstrated the feasibility of inducing neural compensation with the proposed VSWM task at the right amount of cognitive load. This may provide a promising avenue to develop an effective cognitive training and rehabilitation for dementia population.
Subject(s)
Dementia/diagnostic imaging , Dementia/psychology , Memory, Short-Term , Neuroimaging/methods , Space Perception , Visual Perception , Aged , Aged, 80 and over , Algorithms , Alzheimer Disease/diagnostic imaging , Alzheimer Disease/psychology , Brain Mapping , Cognitive Dysfunction/diagnostic imaging , Cost of Illness , Educational Status , Feasibility Studies , Female , Humans , Male , Mental Status and Dementia Tests , Middle Aged , Prefrontal Cortex/diagnostic imaging , Psychomotor Performance , Spectroscopy, Near-InfraredABSTRACT
INTRODUCTION: This study was to assess differences in the symptom profile of depressive illness across various countries/territories in Asia. The study was a part of the Research on Asia Psychotropic Prescription project. The participating countries/territories include China, Hong Kong, India, Indonesia, Japan, Korea, Malaysia, Singapore, Taiwan, and Thailand. METHODS: The pattern of depressive symptoms in 1,400 subjects with depressive disorder from 42 psychiatric centers in 10 Asian countries/territories was assessed. We collected information on socio-demographic and clinical characteristics with a standardized protocol and data collection procedure. RESULTS: The most common presentations of depressive symptoms were persistent sadness, loss of interest, and insomnia. Similar findings were found regardless of the region, country, or its income level. Patients with depressive disorder from high-income countries presented significantly more with vegetative symptom cluster (P < 0.05), while those from the upper middle-income countries had significantly more with both mood (P < 0.001) and cognitive symptom clusters (P < 0.01). In lower middle-income countries, patients with depressive symptoms had significantly less mood symptom cluster (P < 0.001) but significantly more cognitive symptom cluster (P < 0.05). DISCUSSION: This study demonstrates that in Asia, despite variations in the initial symptom reported by the patients, across different countries/territories, core depressive symptoms remain the same. Variations have been found in presentation of depressive symptoms with regards to the level of income of countries. Physical or vegetative symptoms were reported more by centers in higher income countries, while depressive cognition and suicidal thoughts/acts were more frequently reported from lower income countries.
