biopsychology case studies

ralph (1990) + decoursey (2000)

- bred normal hamsters in mutant hamsters with a 20 hour sleep wake cycle

- swapped their scns with the scns of tau hamsters who have 20 hour sleep wake cycles

- destroyed suprachiasmatic nucleus connections in chipmunks and sent them back to the wild, most died after being sent back to natural habitat because they were awake when should've been asleep and died to predators etc

suprachiasmatic nucleus

• part of the hypothalamus

• sends light to the pineal gland when light is detected, therefore stopping melatonin production

campbell and murphy (1998)

- woke up participants at various times and shone a light pad on the back of their knee

- managed to produce sleep wake deviation by up to three hours

- supports light as an exogenous zeitgeber through skin receptors

campbell and murphy eval

- light does not impact everyone the same, eg people in the arctic circle who experience very little light still have stable sleep wake cycles

- man who was blind from birth had a 24.9 hour cycle, exogenous zeitgebers like regular meal times could not fix it

stern and mcclintock (1998)

- some women had a cotton pad in their armpit for 8 hours to pick up pheromones

- the pads were frozen then other women rubbed them on their upper lip

- pad from menstrual cycle day one was rubbed on day one and so on

- 68% of women's cycles changed to matched the odour donor

stern and mcclintock eval

- could be related to historical natural selection, may have been safer for women to menstruate on the same cycle and have babies at the same time

- has not really been replicated and attempts have failed

- lots of confounding variables impact menstrual cycles like diet and stress

siffre

- sws changed to about 25 hours because he was in a cave for ~ 6 months with no natural light or sound

- came out in september and thought it was august

- he did have artificial lights and he could have been training his sleep cycle with the lights being on or off

- small sample size of only one

- our natural sleep wake cycle may not be 24 hours but entrained to that length by exogenous zeitgebers

maguire (2000)

- investigated hippocampus in london taxi drivers who have to memorise the roads and routes

- pronounced structural differences in the brain compared to control

sperry split brains

- could not describe object shown to lvf because the rh relays messages to language centres in lh, not possible in split brain

- could select matching object with left hand that was out of sight

- emotional response like a giggle could be elicited from rvf but participants would report seeing nothing or a flash of light

sperry eval

- split brain ops were traumatic and all different and sperry couldn't control how much brain was removed

- small sample size

- nobody in control had epilepsy but the brain differences may have actually been due to epilepsy in the split brain participants

lashley (1950)

- after removing 10% - 50% part of rat's brains they were still able to remember parts of a maze

- no area proved to be more important than the other for memory = supports holistic brain distribution

fmri

• detects blood flow in brain through brain activity, as more active areas have higher blood flow

• high spatial resolution of 1mm

• can get ppt to complete activities while theyre in machine while you watch how their brain activity changes

• poor temporal validity as images are only taken every few seconds

• very expensive to build and use fmri machines

• non invasive

eeg

• electrodes on a cap which is put on your scalp

• detects brain waves which show brain wave intensity (size of waves) and speed of activation (distance between waves)

• non invasive and good for researching sleep and conditions like epilepsy

• cheaper and more portable than fmri

• high temporal validity because measures in milliseconds

• poor spacial validity because it doesnt show where in the brain the waves are coming from

event related potentials

• electrodes attached to scalp like eeg

• a stimulus is presented to ppt hundreds of times and brain waves in response are measured

• data is combined through statistical averaging to make a waveform with smooth peaks and dips

• this waveform shows what cognitive processes occur after stimulus presentation

• can isolate the impact of an individual stimulus on the brain

• high temporal resolution because works in milliseconds

• poor spacial resolution

post mortem

• brain cut after death, usually those with unusual brains like people who went through trauma

• example: examining tans brain found damage in his broca’s area

• strength: highest spatial resolution because you can physically cut open brain and look inside yourself

• weakness: poor temporal validity and we can’t be sure that unusual behaviour and brain damage are anything other than correlational

ultradian vs circadian vs infradian rhythms

• ultradian = occurs more frequently than every 24 hours

• circadian = occurs every 24 hours

• infradian = occurs less frequently than every 24 hours

four stages of sleep

• nrem 1, 2 and 3, with 3 being the deepest sleep

• stage 4 is rem (rapid eye movement, when most dreams occur)

• one cycle is ~ 90 mins and repeats 4 -5 times during a night of sleep

• babies spend 80% of sleep in rem compared to 20% in adults

dermot and kleitman (1957)

• eeg recordings of 33 ppts over one night of sleep, brain waves followed the 1 2 3 4 stages of deep slow wave sleep and rem

• second study where 9 ppts were woken at different stages of the cycle, those woken in rem more frequently reported dreams

haider (1970)

those recovering from drug overdose had increased rem sleep, suggesting rem is for recovery

functional recovery

functions performed by damaged areas of the brain are moved to be performed by undamaged areas

children, women, those with a higher iq and those who do rehabilitative therapy are far more likely to recover

atonal sprouting / neuronal regeneration

• existing neurons grow new axons to connect to adjacent neurons

• new neuronal cells grow

denervation supersensitivity

to compensate for axon loss in a pathway, remaining axons become more sensitive and more likely to fire

synaptic pruning

unused synaptic connections are lost to make brain communication more efficient

eb hemispherectomy

• at age of two his entire left hemisphere was removed bc of tumor which also removed the lh language centre

• immediately after surgery eb lost all ability to talk

• two years after recovery he began to recover language ability

• brain scans when he was a teenager showed his rh was functioning like the lh for language

• he developed normally and could speak well with some dyslexia like symptoms

pituitary, pineal, adrenal and thyroid gland

• pituitary gland = master gland, releases arch

• pineal gland = releases melatonin for sleep

• adrenal gland = releases adrenaline for fight or flight

• thyroid gland = releases thyroxine for metabolism

structure of neurone

• receptor at end of sensory neurone, effector at end of motor neurone

• axons covered in myelin sheath which increases transmission speed

• axon terminal between sensory and relay neurone creates action potential that gets passed to motor neurone