Alzheimer's disease (AD) is a progressive neurodegenerative disorder that accounts for 60-80% of dementia cases. It is characterized by the accumulation of amyloid-beta plaques between neurons and neurofibrillary tangles of tau protein within neurons, beginning in the medial temporal lobe (especially the entorhinal cortex and hippocampus) and spreading progressively to other cortical regions. These pathological changes cause synaptic dysfunction and neuronal death, producing the characteristic pattern of cognitive decline.
Cognitive Profile
The earliest cognitive symptom is typically episodic memory impairment — difficulty forming new memories of personal experiences — reflecting hippocampal involvement. As the disease progresses, it affects semantic memory (word-finding difficulties), visuospatial function (getting lost in familiar places), executive function (poor judgment, difficulty planning), and eventually language, praxis, and basic self-care. The pattern of cognitive decline reflects the anatomical progression of pathology from medial temporal structures to association cortex.
Cognitive psychology research has developed sensitive measures for early detection. Tests of delayed recall (story recall, word list learning) are the most sensitive behavioral indicators. Subtle deficits in spatial navigation, olfactory identification, and metamemory (awareness of one's own memory failures) may precede clinical diagnosis by years. Biomarker research (amyloid PET, CSF markers, blood tests) aims to identify disease before significant cognitive decline, opening a window for early intervention.
Cognitive Reserve
Cognitive reserve theory explains why individuals with more education, occupational complexity, and cognitive engagement show later onset and slower progression of symptoms despite similar levels of brain pathology. Reserve may reflect more efficient neural networks, greater capacity for compensatory processing, or more robust synaptic connections that buffer against pathological damage, highlighting the importance of lifelong cognitive engagement.
Disorder Of
Episodic Memory
Alzheimer's Disease can affect episodic memory, the ability to encode, store, and retrieve personally experienced events along with their contextual details. Individuals may struggle to form new autobiographical memories or to recall the specific circumstances of past experiences.
Language Comprehension
Alzheimer's Disease can affect language comprehension, the ability to understand spoken and written language. This can manifest as difficulty following conversations, understanding complex sentences, or grasping the meaning of verbal and written communication.
Visuospatial Sketchpad
Alzheimer's Disease can affect visuospatial processing, the ability to perceive, analyze, and mentally manipulate spatial relationships and visual information. Individuals may have difficulty with spatial navigation, constructing or copying designs, and processing the spatial arrangement of objects.
Executive Function Development
Alzheimer's Disease can impair executive function, the set of higher-order cognitive processes including planning, inhibition, cognitive flexibility, and self-monitoring. These deficits can affect goal-directed behavior, self-regulation, and the ability to adapt to changing demands.
g Factor (General Intelligence)
Alzheimer's Disease can affect general cognitive ability, the broad capacity for reasoning, learning, and problem-solving across domains. This pervasive impairment can influence performance across multiple cognitive domains rather than being limited to a single function.