l4- intro to human neuropsychology- what does the prefrontal cortex do? Flashcards
phrenology
- claimed mental triats could be determined by the shape n bumps of the skull
- popular in mid 19th centruy
- attempt to link specific skull regions to mental functions
cortex
human cerebral cortex
- outer layer of brain responsible for higher-order functions like thought, perception n planning
- culture link: art, maths etc
- diff parts do diff things
- frontal cortex= prefrontal + motor
cortex
prefrontal cortex
- complex, many distinct parts
- lateral PFC (side)= complex thoughts
- medial PFC (middle)= thinking about self/internal world
- not directly involved in sensory processing
cortex
eveolution of PFC
- larger in humans then chimps=allow for complex thought (1.2X^)
- one of last regions to mature
KEYY
PFC processes
Synaptogenesis:
forming new neural connections
KEY
PFC processes:
dendritic arborization
- more tree like structures in dendrites
- branching of dendrites for enhanced communication
PFC processes
myelination
- formation of protective sheaths around neurons for faster signalling
phienas gage case study (1848)
- tamping iron accident, iron bar thru frontal cortex
- survived phsyically but had personality changes
- led to early evidence linking frontal lobes to personality n planning
- ‘gage was no longer gage’
pros of single case studies
- proof of principle
- ethical: no intentional harm
cons of single case studies
- casuality: could be trauma not lesion
- non focal: not j 1 part of frontal lobe/large lesion
converging evidence of neuroscience
- use multiple methods to validate findings
- eg:
- on guilt: forensic evidence, eye witness testimony, lie detector (polygraph), character witness, cctv, hearsay
- on neural substrates of planning: patient self report, patient (case)/control studies , functional MRI, animal work (NO COMMENT), non invasive brain stimulation
Converging Evidence on the neural substrates of planning
non human models/animal work
- fruit fly models, rodents, non-human primates
- pros: experimental control, direct measurement
- cons: ethics, not directly transferable to human behaviour
Converging Evidence on the neural substrates of planning
patient self report (qualitative)
- qualitive data from pts w brain injuries
- pros: first hand insight, inexpensive n practical
- cons: subjective/lack of control (natural lesions), not always reliable- eg anosognosia (unawareness)
Converging Evidence on the neural substrates of planning
case-control studies
- compare pts w brain damage to healthy controls
- tasks: tower of london, tower of hanoi, stockings of cambridge
- pros: mutiple pts, quantifiable data
- cons: indivual variability, uncontrolled lesion locations
case-control studies variables
eg tower of london etc
IV: patient group, bumber of required moves
DV: accuracy, reaction time
Converging Evidence on the neural substrates of planning
case control studies
Owen et al 1990
- examined how ppts w frontal lobe damage performed on TOL
- 23 ppts- 15 right lesions, 8 left lesions
- vs 26 healthy controls
- fidnings: FL pts= impairment planning, had more moves to solve problems
Converging Evidence on the neural substrates of planning
case control studies
Nitschke et al 2017
- meta analysis
- consistent results
- no strong L/R hemisphere difference
Converging Evidence on the neural substrates of planning
control for lesion location
owen et al 1995
- compared frontal vs temporal lobe lesions
- Planning impairments are specific to frontal lesions, not just any brain lesion.
Converging Evidence on the neural substrates of planning
fMRI
- measures brain activity by detecting changes in oxygentaed blood (BOLD signal)
- active brain=more O=stronger signal
- use block designs: do task→ rest/control → compare.
- AND cognitive subtraction to isolate task-specific brain activity
fmri
Blood oxygenation-level dependent (BOLD) signal =
Changes in the ratio of oxygenated and deoxygenated haemoglobin
fmri- KEY
cognitive subtraction
- compare task vs control task to isolate whats specific to the task
- eg tower of london (planning) vs control (same visuals no planning)
- subtract control brain acitivy from task - shows planning areas
- inference: whats left= brain regions involved in planning only
good control task
- same perceptual exp (visual images)
- same motor demands
- same emotional states
fmri +planning evidence
fallon et al 2013
- tower of london task in scanner= activates lateral PFC (esp dorsolateral)
- fallon= n=42- reliable activation in PFC
- also see activity in other regions (eg parietal) but PFC key
- nitschke et al 2017- confirms across mutiple studies
- Mainly lateral prefrontal cortex
fmri pros n cons
- pros: reveals networks involved in planning, high spatial precision
- cons: not casual (cant prove necessity), expensive (~£800/scan)- scanner enviroment weird, not all brains fit in 1 pattern
