Biopsychology L9 - 13 Flashcards
Plasticity:
Ability of brain to change and adapt synapses, pathways and structures in light either various experiences or damage caused by trauma
Relative to an adult, how many neurons and synapses does a newborn baby have and why?
- More than an adult
- Needed as developing brain is exposed to vast range of experiences
Study showing plasticity in early infanthood:
Villablanca and Hovda (2000):
- If a baby is born w/ a severely damaged hemisphere and the whole thing is removed soon after birth, the adult will show few or no behavioural/cognitive impairments
What happens to cognitive functioning with age and what study was conducted investigating brain plasticity in the elderly?
- Naturally declines
- Boyke et al (2008) found evidence of brain plasticity in 60 year olds taught juggling as new skill. There was an increase in grey matter in visual cortex, which was reversed when practice stopped.
What research was conducted on meditation and what did they find?
- Davidson et al (2004) compared 8 practitioners of Tibetian meditation w/ 10 student volunteers
- Both grps fitted w/ electrical sensors and asked to meditate for short periods
- Much greater activation of gamma waves (which coordinates neuron activity) in monks
- Only slight increase in gamma wave activity when meditating
What conclusion did Davidson et al (2004) make?
Meditation changes workings of the brain in short-term and long-term
Strengths and weaknesses of plasticity (+2, -3):
+ Research support from both animal and human studies –> Kempermann et al (1998), Blakemore and Mitchell (1973), Maguire et al
+ No age limit to brain plasticity
- Negative behavioural consequences
- Generalisation issues in animals
- Ethical issues in animals eg Blakemore and Mitchell where rats were denied a normal environment
Kempermann et al (1998) study:
Compared to rats housed in ordinary cages, those in complex environments had an increased number of new neurons in hippocampus (part of brain associated w/ new memories)
Blakemore and Mitchell (1973) procedure + evaluation:
Kittens reared in an environment w/ black vertical stripes didn’t respond to black horizontal stripes
Evaluation:
- Study carried out on cats –> cannot generalise
Blakemore and Mitchell (1973) conclusion
Showed visual characteristics of visual neurons could permanently be changed by exposure to specific environments after birth
Maguire et al (2000) study:
- Studied London taxi drivers to discover whether changes in brain could be detected as a result of environment of spatial navigation
- Using MRI scanner, researchers calculated amount of grey matter in taxi driver brains and compared this to set of control pps
- Found front part of hippocampus was larger + positively correlated to how long they had spent driving taxis
Give one study showing plasticity can occur in old people:
- Bezzola et al (2012) showed how 40 hrs of golf training produced changes in neural representation of movement in pps aged 40 to 60
- Using fMRI scans, they found reduced motor activity beforehand which increased after training
What study showed plasticity may have negative behavioural consequences and how?
- Medina et al (2007)
- Brain’s adaptation to prolonged drug use leads to poorer cognitive functioning in later life
Functional recovery after trauma:
Transfer of functions from a damaged area of the brain after trauma to other undamagedareas
Common types of brain trauma:
1) Physical trauma
2) Cerebral hemorrhage –> blood vessel in brain bursts
3) Cerebral ischaemia –> when blood vessel is blocked by thrombosis (blood clot) or arteriosclerosis (thickening of blood vessel walls
4) Viral/Bacterial infections that destroy brain tissue
Why are behavioural effects of trauma likely to be one sided?
Blood supply to brain are often lateralised
What did researchers discover when studying stroke victims and when?
In 1960s, when brain cells are damaged during stroke, brain re-wires itself w/ other parts of brain taking over functions
What did Doidge (2007) find?
Secondary neural pathways that wouldn’t usually be used for some functions are activated
Different types of structural changes:
- Axonal sprouting = Growth of new nerve endings
- Denervation supersensitivity –> axons w/ similar functions are aroused to compensate for loss
- Recruitment of homologous areas on opposite side of brain
- Neuronal unmasking –> Wall (1977)
Disadvantage of denervation supersensitivity:
Oversensitivity to messages like pain
What did Wall (1977) discover about neuronal unmasking?
- Identified dormant synapses (synapses that exist but have blocked functions)
- If rate of input is increased, which usually happens after trauma, these synapses can be unmasked
Danelli et al (2013) case study:
- Italian boy EB who had large benign tumour removed from left hemisphere at 2.5 yrs
- Lost all linguistic abilities after operation
- This improved at age 5 after intensive rehab
- Continued until 8, where they were no longer language difficulties
- Tested at 17 to discover right hemisphere had compensated for LH
Strengths and weaknesses of functional recovery (+3, -1):
+ Practical application
+ No age limits
+ Link between educational attainment and functional recovery
- Gender differences
How does functional recovery have practical application?
- Contributed to neuro-rehabilitation field (doctors provide therapy and electrical stimulation to counter deficits as a result of trauma)
- Must be done because spontaneous recovery tends to slow down after few weeks
Give 2 researchers who studied age differences in functional recovery:
- Huttenlocher (2002)
- Elbert et al (2001)
What does Huttenlocher (2002) say about age differences?
- Functional recovery reduces w/ age
- Only option after trauma beyond childhood is developing compensatory behavioural strats
What did Elbert et al (2001) say about age differences?
Capacity for neural reorganisation is much greater in children than adults
One evaluation for stated age differences in functional recovery:
Studies have suggested even abilities thought to be fixed in childhood can be modified in adults through intense retraining
Which researcher discovered a link between educational attainment and functional recovery and what did he find?
- Schneider et al (2014)
- Patients w/ equivalent to college education are 7 times more likely to recover and be disability free a yr after moderate to severe trauma compared to those w/ just high skl education
- Cognitive reserve could be a factor in neural adaptation
Which researcher showed gender differences in functional recovery and what did he find (w/evaluation)?
- Ratcliffe et al (2007)
- Examined 325 patients for level of response for cognitive skills for rehab
- 16 to 45 yrs old at time of injury
- Received rehab then followed up a yr after
- Women performed slightly better than men on attention/ working memory tests
- Men performed better in visual analytical skills
Evaluation: - Results did not control for performance pre-injury
Different methods of studying brain (6):
- CT
- MRI
- PET
Spec: - fMRI –> uses for lie detection asw
- EEG –> detect brain disorders, identify state of brain
- ERP
- Autopsy
How do fMRIs work?
- Indirectly measures blood flow through oxygen concentration in blood stream
- Signal used is BOLD ( Blood Oxygen Level Dependent) contrast
How does measuring oxygen concentration tell us what the most active areas of brain are?
Most active areas will have neurons w/ most energy, which requires glucose and oxygen to be carried in bloodstream
Strengths and weaknesses of fMRI:
+ Risk free –> no radiation and non-invasive
+ Good spatial resolution of 1-2mm –> significantly higher than others
- Assumes causation
- Poor temporal resolution of 1-4 secs
- Cannot hone in on activity of individual neurones
Spatial recognition:
Smallest feature that a scanner can detect
What issues are there in assuming change in blood flow is because of neural activity?
- Psychologists unable to conclude 1 function is localised to a region of brain
- Some say it shows localisation of function but does not show communication between diff areas in brain
Temporal resolution:
Accuracy of scanner in relation to time
How do EEGs work, who developed this and when?
- 24 or 32 small recording electrodes distributed over skull
- Pick up electrical activity of millions of neurons
- Developed by Hans Berger in 1929
2 basic properties of EEGs:
1) Amplitude –> intensity of electrical activity
2) Frequency –> speed of electrical activity
2 distinctive states of EEG:
1) Synchronised pattern –> Recognisable waveform can be identified
2) Desynchronised pattern –> No recognisable waveform
Different waves in EEG:
1) Alpha
2) Beta
3) Delta
4) Theta
Strengths and weaknesses of EEG (+2, -2):
+ Good temporal resolution
+ Invaluable diagnosis of conditions like epilepsy and stages of sleep
- Cannot reveal what is happening in deeper regions, as it is just superficial
- Poor spatial recognition