Quiz 2 Flashcards
What is a functional MRI?
A functional neuroimaging technique
measures blood oxygenation in an area with blood-oxygen-level-dependent (BOLD)
How does a functional MRI work?
-When neurons fire there is an increase in metabolism
-results in dilation of blood vessels in that area
-end up with increased blood oxygenation in the area
-oxygenated and deoxygenated blood have different magnetic properties
Pros and cons/caveats of fMRI
Pros: -predict changes in regional activation/recruitment
Cons: -slow time course
- just a correlate of activity
- motion causes increased noise, false negative or positives
- time course of BOLD response influenced by cerebrovascular differences (biased timing and amplitude in older adults)
- BOLD signal decline as a result of cerebrovascular differences
fMRI interpretation
Predict neural activity in an area
What is an event-related potential?
Provides an estimate of the timing of a cognitive process and the strength of activity; estimate approximate location of activity
Pros and cons of ERPs
Pros: excellent temporal resolution
Cons: poor spatial resolution, poor estimation of subcortical areas, motion is still a problem
How do ERPs work?
Electrons on the brain measure voltage and create a summation of negative or positive polarity
ERP interpretation
Timing of potential, amplitude of potential, topography of potential
ERP component
Summed electrical signal associated with a cognitive process
Pros and cons of functional neuroimaging
Pros: can ask questions directly about the brain, relatively non-invasive
Cons: Correlational rather than causation, expensive, additional restrictions to sample
PASA
Posterior-Anterior Shift in Aging
HAROLD
Hemisphere Asymmetry Reduction in OLDer adults
CRUNCH
Compensation-Related Utilization of Neural Circuits Hypothesis
- deficits compared to YA cause OA to recruit additional brain regions - can only do this to a point
-as demand increases, a resource ceiling is reached, leading to age related decrements for harder tasks
-reserve can increase capacity for compensation
STAC/STAC-r
Scaffolding Theory of Aging and Cognition
Compensation
Cognition-enhancing recruitment of neural resources in response to relatively high cognitive demand
Occurs when ability is not meeting demand & see an improvement in performance with increased recruitment
Evidence for and against compensation
For: age-related hyperdifferentiation in anterior temporal lobe
Against: no evidence of increased information in PFC for older vs younger adults
Dedifferentiation
Greater similarity of neural responses across tasks/conditions
Driven by:
1) Attenuation - decreased recruitment in preferred region
2) Broadening -increased recruitment in non-preferred region
3) Both
Evidence for and against dedifferentiation
For: no evidence of increased information in PFC for older vs younger adults
Against: age-related hyperdifferentiation in anterior temporal lobe
Relation between neural structure and function
Greater structural change has been associated with greater functional recruitment (reduced gray matter, white matter decline, decreased dopamine binding, amyloid burden, iron accumulation)
Multi-voxel pixel analysis
Examines the difference in the pattern of activity across a set of voxels
Can we distinguish categories based on patterns?
Representational similarity analysis
Examine the similarity of patterns of activity across voxels
“How similar are patterns for different categories?”
Hyperdifferentiation
Increased differentiation in OA compared to YA
Mediation
Mediating variables explain why two things are related
Variability/individual differences in aging
age changes in variability are greater for
- more complex tasks
-response time compared to accuracy
Maintenance
Ongoing repair and replenishment of brain after damage due to wear and tear
Maintenance - effect on demand
Does not have an effect on demand
Maintenance - effect on neural resources
correction of neural resources after they dip
Maintenance - time course
Occurs throughout the lifespan but becomes more critical with old age
Reserve
A cumulative improvement of neural resources that mitigates the effects of neural decline caused by age
Reserve - effect on demand
Does not have an effect on demand
Reserve - effect on neural resources
increases neural resources before effects of aging take effect so ability stays above cognitive demands
Reserve - time course
Takes place before aging but can continue to be built up through old age
Compensation
Cognition-enhancing recruitment of neural resources in response to relatively high cognitive demand
Compensation - effect on demand
Occurs to meet rising demand
Compensation - effect on neural resources
Increase in neural resources
Compensation - time course
Occurs over second or minutes, not limited to older adults
Compensation requirements - role of non-invasive stimulation
- must be directly or indirectly related to a gap between available neural resources and task demands
- Must be linked to improved cognitive performance
–causality ban be determined using non-invasive stimulation
Compensation three types
Upregulation, selection, reorganization
Compensation - Upregulation
Older adults recruit the same process and same region as younger adults, but to a greater extent
Compensation - selection
Older adults recruit an easier process that is available to young adults but not as efficient
Compensation - Reorganization
Older adults recruit new processes (unavailable to YA) in place of processes affected by impairments
Simpson’s paradox
Data compared across groups looks different than when compared within groups
Moderation analyses - moderating variables
Influence the relationship between the independent and dependent variables
Moderation analyses - interpretation
Strength of the moderating variable tested using interactions
Testing the brain reserve hypothesis - what measures are needed
Operationalize:
- Reserve
- brain damage
- change in cognitive capacity
Demonstration that reserve is responsible for regulating the relationship between neural burden and decline
Alzheimer’s - description, causes, symptoms
Cognitive decline in memory
Pathology: plaques, tangles, atrophy
Symptoms: impairment of episodic memory, executive functioning, spatial memory, verbal fluency
Vascular - - description, causes, symptoms
-Caused by damage to the vessels that supply blood to the brain
-symptoms: problems with problem solving, slowed thinking, and loss of focus/organization
Lewy body - description, causes, symptoms
Umbrella term for conditions (AD, Parkinson’s) associated with build up of Lewy bodies
-symptoms: acting out dreams in sleep and visual hallucinations; also uncoordinated or slow movement, tremors, or stiffness
Frontotemporal - description, causes, symptoms
Breakdown of nerve cells and their connections in the frontal and temporal lobes
Symptoms: changes in behavior, personality, thinking, judgement, language, movement
Semantic Dementia
Temporal variant of fronto-temporal dementia
Symptoms: word finding issues, word fluency deficits, impaired associative semantic knowledge, starts to interfere with everyday activities, normal episodic memory
Gammaneuromodulation
Cognition is support by synchronous oscillations in the brain, particularly gamma waves
Gamma modulation has been shown to decrease AD symptoms and reduce pathology
Gammaneuromodulation - rhythmic sensory stimulation
auditory and visual stimulation
Gammaneuromodulation - Transcranial alternative neural stimulation
Low intensity electrical currents
Gammaneuromodulation - transcranial direct current stimulation
Low intensity electrical currents
Gammaneuromodulation - transcranial magnetic stimulation
Magnetic stimulation
Gammaneuromodulation - neurofeedback
Participants view their own waveforms and learn how to regulate neural activity
Options to address variability in aging affects
1) Minimize variability
2) Maximize variability by encouraging diversity and study the differences as moderators
Pros and cons of minimizing variability
—pros: faster, easier, easy to interpret, will be consistent with prior research
—cons: minimizes generalizability and representation, misses potential treatments and pockets of preservation
Pros and cons of maximizing variability
—pros: increases generalizability and representation, identify differences in treatments, better care/treatments for a greater cross-section of the population, help to identify the mechanisms of change
—cons: difficult to find representative samples, analyses more complex, requires overall larger samples
History of diversity in research
- misuse of cognitive psychology in early years (1800s-early 1900s)
-1920s-1940s: behavioral psych, individual differences ignored - cognitive revolution: 1950s on, all humans are born with the same innate abilities, individual differences ignored
- NIH revitalization act 1993: women and minorities must be included in research
- 2001 amendment: guidelines for reporting on sex, gender, race, ethnicity
- 2016 FDA year of diversity in clinical trials
WEIRD psychology
Western
Educated
Industrialized countries
Rich countries
Democratic countries
Obstacles to diversity
- selectivity bias in participants (difficulties getting to lab, mistrust of science, awareness of research, biased screening)
- lack of research enthusiasm (slows down research, increases variability/noise)
- lack of diversity in those conducting research
How to increase diversity in research
- methodological changes
- improve recruitment
- support diversity among those conducting research
Methodological changes to increase diversity
- beware of selection bias (differences in overall health and survival in some minority groups)
- utilize non-biased measures
- be cautious with causal claims
- used models designed to capture interactions across multiple levels of variables to consider the social context of risk factors
- report all potentially relevant demographic information
Recruitment to increase diversity
- Develop partnerships with community organizations
- Build 1:1 relationships - be honest about costs and benefits
- Establish reciprocity: telling them how they are supporting their community
Supporting researcher diversity
Faculty and new students
Looking forward to increase diversity
- participation remains low for racial and ethnic minorities, underrepresented groups like women, OA, low SES
- AD research focused on diversity
Sensory threshold (absolute and differential)
Absolute - point at which 50% of the time you detect a stimulus
Differential - amount of difference to distinguish between two stimuli 50% of the time; just noticeable difference
Conversion of sound waves to neural signals
sound waves enter pinna and travel down ear canal -> waves vibrate the eardrum -> eardrum vibrates the ossicles -> vibrations cause fluids in the cochlea to ripple -> hair cells along the cochlea allow vibrations to be turned into nerve signals -> signals carried to the brain by the auditory nerve
Presbycusis
Age-related hearing loss
-particularly with high frequency sounds and background noise
Causes of age-related hearing loss
-impacted ear wax
-thickened ear drum
-occasional damage to ossicles
-damage to sensory hair cells
conversion of light to neural signals
light passes through cornea -> light passes through pupil, iris controls pupil to let more or less light pass through -> lens focuses light onto retina ->retina converts light energy into a nerve signal -> optic nerve carries signal to brain
Presbyopia
Age related loss of visual acuity (sharpness)
- problems with glare, brightness, and darkness, visual field gets smaller
Causes of age-related vision loss
- cornea is less transparent, less sensitive
- lens hardens, becomes yellow and cloudy
- pupil becomes smaller, reacts slower
- muscles become less able to rotate the eye
Sensory ARHL (causes and audiogram pattern)
- deterioration of hair cells within the cochlea
- normal hearing at lower frequencies and steep increase in thresholds at higher frequencies
Metabolic ARHL (causes and audiogram pattern)
- atrophy of the outer cochlear wall, impairs cochlear amplifier
- some lower frequency loss and gradual increase in loss for higher frequency sounds
Neural ARHL (causes and audiogram pattern)
- atrophy of the spiral ganglion cells (sensory neurons)
- audiogram not affected until significant levels of atrophy, dramatic decrease in speech differentiation
Anatomical changes to auditory cortex
- decreased GABA in auditory cortex
- decreased volume and cortical thinning
Functional changes to auditory cortex
- Increased activation in OA compared to YA
- Reduced connectivity between auditory cortex and visual regions, attention network, and default mode network
Nonauditory cortical reorganization
- greater atrophy in attention related regions (ACC)
- Increased functional connectivity and increased recruitment of visual, motor, and attention networks
-related to general cognitive impairment
Common cause hypothesis
Biological aging affects global functioning, including both cognitive and sensory function
Information degradation hypothesis
ARHL leads to increased cognitive demand, which can contribute to impaired cognitive function
Sensory deprivation hypothesis
ARHL leads to cortical reorganization to support auditory perception, which can contribute to impaired cognitive function
