The Aging Brain Flashcards
Frontal Lobe - Primary Function
Executive functioning
Parietal Lobe - Primary Function
Goal-oriented movement
Temporal Lobe - Primary Functions
Hearing, language, and music
Occipital Lobe - Primary Function
Visual processing
White Matter - Composition and Function
Made of nerve fibers (axons) and forms tracts that send information through the brain
Gray Matter - Composition and Function
Made of cell bodies, dendrites, and axon terminals and is where processing of information occurs
General Structural & Functional Brain Changes with Age
Include decreased white and gray matter volume, alterations in functional connectivity, increases in vascular lesions, changes in protein composition, and reductions in neural activity and blood flow
White Matter Changes in Aging - Causes and Location
Reductions attributed to myelin degeneration, axonal loss, and reduced white matter integrity. Most changes often in areas involved with complex functions. Linked to widespread cognitive deficits
Functional Connectivity
- Reductions of tract are within lobe
- Reductions between lobe
- Reductions between hemisphere
Gray Matter Changes in Aging - Causes and Variability
Reductions attributed to reduced synaptic densities. Do not occur at the same rate in different areas or in everyone at the same rate. Volume loss is associated with specific cognitive deficits
Gray Matter - Slide 14 graph
- Lateral prefrontal cortex shrinks steadily with age.
- Primary visual cortex shows slight age-related declines.
- Hippocampus declines more rapidly after age 60.
**This study suggests that not all brain regions shrink at the same rate, with the hippocampus and prefrontal cortex being more vulnerable to aging than the visual cortex.
Brain volume changes
Volume:
- Ventricle volume steadily increases after 40 years of age
- Coincides with maximum loss of gray and white matter starting around 40
- Total cerebrum volume peaks just before the onset of puberty
Max growth:
Gray matter volume, white matter volume, and subcortical gray matter volume rate of growth was maximum in infancy and early childhood
Vascular lesions in the brain related to risk factors and cognition/dementia
The appearance of vascular lesions is due to vascular risk factors such as smoking, high blood pressure, and drinking alcohol. If lesions are due to these risk factors, they often appear in the frontal lobes. These changes are associated with future cognitive decline. More widespread lesions may be associated with early dementia.
Changes in Protein Composition in Aging
Many changes in proteins and enzymes influence brain health and function
Common increases in amyloid-beta and tau proteins occur with age
May have specific directionality of accumulation in the brain (starting in temporal lobe and then spreading out)
Can lead to dementia and cause severe deficits in cognitive functioning
Functional Connectivity Changes in Aging
Reductions observed within lobes, between lobes, and between hemispheres
Neural Activity Changes in Aging
Reductions in how neurons fire, resulting in changes in brain activation patterns during cognitive tasks and rest. Can be increases or decreases, influenced by individual variability, and associated with cognitive deficits or maintenance (compensation).
Blood Flow Changes in Aging
Alterations and reductions observed during cognitive tasks and rest. Can be increases (compensation) or decreases, largely influenced by arterial stiffness and vascular risk factors. Reduced activity often linked to poorer cognition
Lifespan Brain Volume Changes
Ventricle volume steadily increases after 40, coinciding with maximum loss of gray and white matter. Total cerebrum volume peaks before puberty
What commonalities exist across all brain changes?
- Changes are influenced by individual variability
- Associations with cognition are dependent on the area affected
- Compensation methods can result in increased blood flow and neural activity despite changes in GM
Which cognitive domains typically decline in cross-sectional studies of aging?
In cross-sectional data, declines are evident in all cognitive domains except verbal and numerical ability. However, these results may be influenced by cohort effects.
Which cognitive domains typically decline in longitudinal studies of aging?
In longitudinal data, declines are evident in all cognitive domains after age 55. Only processing speed shows decline before age 55
Crystallized Abilities
- Definition: Cumulative abilities built over time (e.g., knowledge, vocabulary); generally remains stable with age.
- Related Brain Regions: Primarily associated with temporal and frontal lobes.
- Functions: Language processing, semantic memory (stored meaning of words and concepts).
Fluid Abilities
- Definition: Require flexibility of cognitive processing at the time of test (e.g., processing speed, attention, task switching); declines with age.
- Related Brain Regions: Mainly associated with frontal lobes, particularly the prefrontal cortex.
- Functions: Executive functions such as planning, problem-solving, and cognitive flexibility.
Long-Term Episodic Memory
- Definition: Memory of specific events; stable until 55-60, then declines around 65.
- Related Brain Regions: Involves the hippocampus and medial temporal lobe structures.
- Functions: Encoding, storing, and retrieving personal experiences.
Long-Term Semantic Memory
- Definition: Meaning of words and concepts (not specific to events or times); increases from 35-55, then plateaus, with a slight decline after 65 (less substantial than episodic).
- Related Brain Regions: Associated with temporal and frontal lobes.
- Functions: Language comprehension, general knowledge, and semantic memory retrieval.
Working Memory
- Definition: Holding and manipulating information; declines with aging.
- Related Brain Regions: Engages the prefrontal cortex and parietal lobes.
- Functions: Temporary storage and manipulation of information necessary for complex cognitive tasks.
Short-Term Memory
- Definition: Holding information briefly; relatively preserved in normal aging.
- Related Brain Regions: Also involves the prefrontal cortex and parietal lobes.
- Functions: Immediate storage of information for brief periods of time.
Language Abilities
- Age Trajectories: Vocabulary and semantic memory remain stable or improve. Visual confrontation naming is stable until 70 then declines. Verbal fluency shows declines.
- Related Brain Regions: Distributed across temporal, frontal, and parietal lobes.
- Functions: Various aspects of language processing including comprehension, production, and naming.
Factors Maintaining High Cognitive Function - Physical Activity
Aids executive function and reduces declines in tissue density in frontal, parietal, and temporal cortex; may have global brain effects
Factors Maintaining High Cognitive Function - Intellectual Stimulation
Seems to protect against age-related declines and AD progression; increases baseline cognitive function; may promote neurogenesis
Factors Maintaining High Cognitive Function - Minimize Chronic Stressors
Increased stress linked to higher AD risk and faster cognitive decline; damages hippocampal neurons; cortisol impacts glucose metabolism in the hippocampus
Factors Maintaining High Cognitive Function - Brain-Healthy Diet
Rich in poly/mono saturated fatty acids and polyphenols/antioxidants can slow cognitive decline and potentially prevent AD
Dementia Prevention
Up to 45% of dementia can be prevented by modifying our lifestyle
Cognitive Reserve - Definition and Factors
Individual differences in how people process tasks, allowing better coping with brain pathology. Influenced by education, social engagement, occupational status. Not fixed or unchangeable.
Brain Reserve - Definition and Factors
Individual differences in the brain itself aiding coping with pathology. Measured by neurobiological capital (number of neurons, synapses). Considered a more passive, fixed construct
Brain Reserve (Passive Model)
- Definition: The brain’s structural capacity to tolerate damage before functional impairment appears.
- Key Idea: Some individuals have larger brains, more neurons, or greater synaptic density, allowing them to sustain more damage before cognitive decline is noticeable.
- Example: A person with a larger hippocampus may resist memory decline longer despite developing Alzheimer’s pathology.
Cognitive Reserve (Active Model)
- Definition: The brain’s ability to compensate for damage through flexible cognitive strategies and efficient neural processing.
- Key Idea: Individuals with higher education, complex occupations, or engaging lifestyles can adapt better to brain aging or pathology by using alternative neural pathways.
- Example: A highly educated person with Alzheimer’s might function normally for years by recruiting different brain regions to support memory.
Scaffolding Theory of Aging and Cognition - Revised (STAC-r)
The STAC-r proposes that cognitive reserve factors (like education) and brain reserve factors (like head trauma) influence brain structure and function throughout life. As everyone eventually declines, compensation methods (or scaffolding) are used to maintain functioning
Posterior to Anterior Shift in Aging (PASA)
The PASA model suggests that with aging, there is an increase in frontal activity to compensate for declines in parietal activity…. This compensatory scaffolding involves additional recruitment of frontal regions to help maintain high cognitive function, especially in areas like memory where parietal regions are affected by atrophy
Bilateral Recruitment in Aging
Increased left frontal activity seen in high-performing older adults compared to younger adults; low performers don’t show this additional recruitment, a form of compensation
