AD is the most dreaded and heterogeneous form of Dementia . It is widely found during mid-to-late in life, affecting cognitive ability. AD is regarded as a slow and progressive disorder. The significant symptoms of AD are lack of judgment, irregularities in memory, difficulty in speaking, and abnormalities in visuospatial perceptions and behavior . When AD progresses, individuals will experience difficulty carrying out their daily living. They will usually go mute, bedridden, and challenging to handle . AD gradually provides fatal results from prolonged medical illness. In rare cases, it will cause delusions and hallucinations . It often begins with a vague memory loss, which slowly interrupts the quality of life, destroying memory and ability to think .
AD selectively damages the neurons in specific regions in the neural systems and the brain. The damage includes the nerve cells in the hippocampus, cortex, anterior thalamus, amygdala, and basal forebrain. The damaged nerve cells are found to have an accumulation of amyloid plaques (Aβ), and neurofibrillary tangles called the Tau tangle . The amyloid plaques interrupt the communication between the neurons. They affect the cells, cause their death, and obstruct intercellular transport. The plagues and Tau tangles are formed in the hippocampus early and later spread to other brain regions , . The risk factors causing AD include lifestyle choices (exercise, diet, smoking, etc.), genetics, biology (gender and age), and accidents (head trauma) .
AD is considered one of the orphan diseases, diseases with no cure . The diagnosis is made only after the autopsy. Brain imaging, neurocognitive tests, and cerebrospinal fluid (CSF) analysis are the diagnostic approaches widely used . AD is one of the forms of Dementia. Dementia is anticipated in 50 million people worldwide, and among them, about 67% have AD . Unfortunately, there is no cure, and there seem to be only four drugs approved for slowing down the symptoms. Treatments can only slow down progress and do not eliminate the symptoms. A better understanding of the clinical pathologies, mechanism of the disease, and genetic risk factors may help treat AD effectively .
As discussed above, AD is a progressive neurological disorder that primarily affects memory and learning. AD being an orphan disease combined with a high dimensional complex data and uncertainty demands advanced approaches, such as Artificial Intelligence (AI) . AD aids in revealing patterns in vast complex gene expression data, which leads to the discovery of disease-related genes. The difficulty with AD is that more neurons have died by the time it is diagnosed, making it irreversible. The etiology of AD is uncertain, but it is estimated that 70% of the cases are associated with genetic factors . Currently, for AD, there is no reversible or prevention treatment. Also, it is challenging to build a simplified model because of complex interactions among various factors and the complexity of humans. Fortunately, the recent and rapid developments in AI offered solutions to these problems, which involve ultra-complex massive data . AI carries out an integrative approach and models the functional neurobiological components that influence neuropsychiatric disorders. This study implemented an AI-based strategy on two AD microarray datasets. We analyzed the data using a standard preprocessing routine and normalized it to make it comparable across all the platforms. Then, we performed the ensemble-based feature selection to choose the relevant genes that possibly cause AD. Once the required genes are selected, AD and non-AD classification is carried out using the Deep learning approach.
The remaining section of the paper is split into materials and methods, which discuss the background and the approaches used, Results and Discussion, discuss the results of the applied techniques and their performance evaluation, and then the conclusion of the work done.