Biological Studies Flashcards
Sperry (1968)
Theme
Regions of the brain- Hemispheric disconnection
Casey (2011)
Theme
Regions of the brain- behavioural and neural correlates of delayed gratification
Blakemore and Cooper (1970)
Theme
Brain plasticity-impact of early visual experience
Maguire (2000)
Theme
Brain plasticity- spatial memory and navigation
Sperry (1968)
Patients
Surgery
Aims
- epilepsy tends to have seizure in both hemispheres of the brain
- cutting the corpus callosum between the two hemispheres, contains the seizures to one side, causing less damage
- To study psychological effects of hemispheric disconnection in patients with epilepsy
- Demonstrate how each hemisphere has independent streams of conscious awareness and their own set of memories.
Casey et al (2011)
Original research
Regions of the brain
Aims
- Marshmallow test- ability to delay gratification on 4/6 year olds. 2/3 struggled to delay gratification.
- inferior frontal gyrus in the prefrontal cortex- go and mo-go tasks (inhibition)
- ventral striatum- immediate choice and reward
- If the ability to delay gratification is a consistent personality trait into later life.
- Investigate activity in the brain between high and low delayers associated with self-control and delay.
Blakemore and Cooper (1970)
Background
Visual Cortex
Plasticity
Visual cortex- Hubel and Weisel stimulated individual neurons and found there are column of cells that respond to particular orientations of a line.
Plasticity- Hilsch and Spinelli- visual cortex effected by experience. Animals are born with orientation columns but if not used, the ability to respond disappears. The exposed one eye to horizontal stripes and the other to vertical stripes.
Cells are now monocularly driven instead of binocularly driven.
Maguire (2000)
Brain part
Aims
The hippocampus- located deep inside the temporal lobes on the side of the brain. Central to spatial memory.
Aims:
• Is the brain capable of changing in response to environmental stimulation?
• Identify role of the hippocampus
• Demonstrate structural changed in response to behaviour requiring spatial memory.
Sperry (1968)
Method and Design
- Quasi experiment
- Case study
- no IV only looked at one group (Independent measures)
- DV: performance of visual, tactile and other tests.
Casey (2011)
Design
Method
DV for both experiments
- Longitudinal quasi experiment
- Independent measures
- IV: high vs low delayers from previous results
- DV: 1) reaction time and accuracy on certain no/no-go tasks. 2)activity using fMRI.
Blakemore and Cooper (1970)
Method
Design
IV and DV
- Lab experiment
- Independent measures
- IV: reared in the horizontal or vertical environment
- DV: behavioural and neurophysiological effects
Maguire (2000)
Method
Design
IV and DV
- Quasi experiment
- Matched pairs
- IV: taxi driver or not
- DV: volume of the hippocampus in 6 areas by VBM (volume, shape and size) and pixel (slices) counting by an MRI scanner.
Sperry (1968)
Sample details
- 11 patients with epilepsy who had been referred to the White Memorial Centre in LA.
- Opportunity sample.
Casey (2011)
Sample details
- Opportunity sample
- from a pool of 117 originally from Stanford university nursery.
- 59 agreed
- 40-year-olds
- even split between high and low delayers from previous results
- 27 agreed to take part in ex 2.
Blakemore and Cooper (1970)
Sample details
Ages when measured
- 2 cats -each reared in the different environments.
- New-born at the beginning.
- 5 months when behavioural responses were collected
- 7.5 months at neurophysiological test
Maguire (2000)
Sample details
Controls
- 16 male right-handed taxi drivers who had passed the ‘Knowledge’ test.
- mean age 44 years old
- Mean training time was 2 years.
- All were healthy.
- Control group were 50 men held in an MRI data based and were matched on age, gender health and were all right handed.
Sperry (1968)
Apparatus
Tachistoscope- displayed an image for a particular amount of time.
Blakemore and Cooper (1970)
Materials
- cylinder with black and white stripes in each orientation
- it had no corners or edges
- kittens for a black collar to restrict width and prevented from seeing their own body.
Sperry (1968)
Visual test
- Stimulus presented to one or both visual fields for 1/10 of a second or less using the tachistscope. Participants had to say what they saw.
- Composite word (keycase) on screen and participants asked to report the word key was on LVF and case was on RVF.
- Image was shown to either of the visual fields and asked to name the image.
Sperry (1968)
Tactile test
Dual Processing task
also image one
- Object placed in right hand or left hand then have to find it again form a grab bag.
- Different objects put in both hands, one hand touched or put into position.
- Dual processing task: two objects placed in hands simultaneously and then hidden in a pile of objects. Each hand is required to recognise the objects.
- Image was also shown to either visual field and participants had to identify the same object with one of their hands.
Casey (2011)
EX1
- press a button every time that they saw a specific sex, making the opposite sex on the screen a no go
- The faces appeared for 500 milliseconds followed by a 1-second interval.
- A total of 160 trials per run in a pseudorandomised (computerised) order.
- Each run consisted out of 120 go trials and 40 no-go trials.
- This was a 2x2 factorial design: male and female faces and the go a no-go task.
- Hot and cold stimuli were used (hot was happy or fearful faces)
Casey (2011)
EX2
- scanned on an fMRI
- on the hot tasks only
- Stimuli and instructions were identical to ex 1
- but had jittered inter-trial interval lasting an average of 5.2 seconds instead
- There were 48 trials per run in a pseudorandomised order: 35 go and 13 no-goes.
- two trials: one was of happy faces and the second of fearful faces.
- Total of 70 go and 26 no-goes.
- 2x2x2 mixed effects model. The trial type was either go or no-go (repeated measures), the emotion involved was happy or fearful and the groups were either high or low delayers (independent measures).
Blakemore and Cooper (1970)
Early experience
- Spent the first two weeks in complete darkness but allowed binocular vision.
- Placed in the cylinder for around 5 hours a day. The rest of the time they spent in darkness.
Blakemore and Cooper (1970)
Exposure to normal environment
- 5 months was beyond the critical period and so changed would have been made to the visual cortex by now.
- Put in a well-lit room which had chairs and tables for several hours and the reactions were observed.
Blakemore and Cooper (1970)
Behavioural assessment
•Things done were startle reactions, following a rod with their head and hovering above a table to see if they reached out for it. This took several weeks.
Blakemore and Cooper (1970)
Neurophysiological assessment
- At 7.5 months the kittens were anaesthetised
- Activity of the primary visual cortex (single neurons) was recorded using micropipettes filled with sodium chloride.
- Thin bright lights were shon on a screen in front of the cat.
- The electrode was inserted so that it covered many visual columns.
Maguire (2000)
Method 1 using MRI
VBN
- Template- compared the taxi drivers to identify overall difference in brain component size. The template was generalised from all 50 of the control group’s brains. The matched pairs were then compared to the generated template.
- Grey matter- differences in grey matter.
Maguire (2000)
Method 2 using MRI
Pixel counting
- Analysed by one person who was experienced in counting and were ‘blind’ to the IV and the VBM results.
- Calculating volume- only 24 slices used in the final analysis. multiplied pixels by distance.
Sperry (1968)
Results
Visual x3
- Image into RVF could be named but could not in LVF.
- Nude image to left visual field- grinned but didn’t know why!
- Image flashed on both- draw what was seen on the LVF and name what was seen on the RVF.
Sperry (1968)
Results
Tactile x2
- If presented to the right hand could name it, draw it with same hand and find again with the same hand but couldn’t recognise with the other hand.
- If different objects were put in each hand: only able to name the on in the right, in the grab bag the right hand would ignore what was in the left and were only able to re-find objects with the same hand.
Casey (2011)
Results EX1 ‘false alarms’
Hot and cold
Delayer difference
-The mean false alarm for cool was less than for the hot tasks and so emotional faces provoked a less accurate response. -Particularly low delayers performed poorly on the hot tasks.
Casey (2011)
Results EX2
Regions
- Right inferior frontal gyrus- reduced activity in low delayers on no-go trials compared to high.
- Ventral striatum- more activity in low delayers than high on no-go trials when shown a happy face.
Blakemore and Cooper (1970)
Results
Behavioural
- Some reflexes normal (pupil contraction)
- Temporary deficit- visual placing (reaching legs to a surface) but this was recovered within 10 hours.
- Only acknowledge waving rod if it was waved the same orientation that the cat was reared in, the other ignored.
Blakemore and Cooper (1970)
Results
Neurophysiological
- For both cats, 75% of 125 neurons fired binocularly and acted ‘normal’
- The horizontal cat did not respond to lines within 20 degrees of the vertical orientation and 12 out of 52 responded within 45 degrees of the vertical. This was similar for the vertical cat.
Maguire (2000)
Results
- Anterior LH + RH was significantly greater in volume in controls than the taxi.
- Posterior LH + RH had significantly greater volume in taxi than the controls.
- Correlations- time spent as taxi driver: Positively correlated to volume of posterior RH. Negatively correlated to the volume of anterior LH + RH.
Sperry (1968)
Conclusions
Visual and Tactile
- The two hemispheres operate independently.
- The left handles language and provide names of objects.
- The right on the other hand cannot express language but can experience emotions such as laughing when the nude image was flashed.
- No language centre in right hemisphere so unable to say object in the left hand.
- Each hemisphere only has memory of object given to the opposite hand.
Casey (2011)
Conclusions
- those who were low delayers at 4 continued to be low delayers at this age
- Reduced activity in frontal gyrus of low delayers means they have little thought processing of the action of delaying and are more motivated by the increased activity of the ventral striatum.
Blakemore and Cooper (1970)
Conclusions
- Visual experience of cats in their early years has modified their brains.
- Behavioural responses came back within 10 hours or so meaning that the effects were not permanent.
- Nature is modified by nurture- the brain had plasticity and is manipulated by the environment which is inputted.
Maguire (2000)
Conclusions
- Relationship between navigational skills and the relative grey matter in the hippocampus.
- The changes in the brain are acquired= nurture.
- Only demonstrates plasticity of the hippocampus and not other areas.
