Biological Approach Flashcards
(20 cards)
Sperry
Aim?
To investigate the effects of hemisphere disconnection on brain function, perception and memory.
Sperry
Sample?
11 patients who had recently undergone a commissuratomy due to suffering with severe epilepsy which could not be treated by drug therapy.
Sperry
Method?
- Pp were told to look at a dot in the centre of the screen and cover one eye. An image was presented for 1/10th of a second to prevent the image travelling to the other hemisphere. Pp then asked what they had seen.
- two images were presented simultaneously to both visual fields. Asked to say and draw what they had seen with the left hand.
- Tactile info was presented to either L or R hand without Pp seeing. Pp then asked to point to what they had been given or say what it was.
- Tactile info presented to both hands. Asked to say or point to what it was.
Sperry
Results?
- When an image was presented to the RVF (left hemisphere) Pp could say what the image was but when the image was presented to the LVF (right hemishere) they could not explain what they had seen.
- Pp could say what they had seen in the RVF but would be unaware they had seen anything in the LVF. But when asked to draw with their left hand what they had seen in the LVF they could do it.
3+4. If the object was placed in their left hand they could point to what the object was but could not say what it was. But they could name object if placed in right hand. When Pp was asked what was in the left hand they would say ‘i cannot work with that hand’
Sperry
Conclusions?
Hemisphere disconnection causes the two hemispheres to operate independently. Each has its own perception, consciousness and memory and are unaware of the other hemisphere. Verbal responses are only possible when information is presented to the left hemisphere. Right hemisphere controls logic.
Casey
Aim?
To investigate whether delay of gratification in childhood predicts impulse self control abilities in adulthood.
Casey
Sample?
59 agreed to participate of 117 contacted who had scores above or below average in the gratification delay task which took place at age 4 in stanford nursery school.
Experiment 1- 59 (23m, 36F) Experiment 2- 27 of 59 (13M, 14f)
Casey
Method?
Experiment 1:
32 high delayers, 27 low delayers gave consent to take part in a behavioural version of a ‘hot’ ‘cool’ impulse control task . Completed in own homes via pre-programmed laptops. Pp instructed to either press the button ‘go’ or withhold the button ‘no-go’. Cool version- faces with neutral expressions
Hot version- faces with happy expressions.
One sex was go stimulus, other sex was no-go
Each face appeared for 500 miliseconds
160 trials in total.
hot and cool versions to explore the influence of alluring social cues.
Experiment 2: 15 high delayers and 11 low delayers. Researchers used fMRI to examine neural correlates of delay of gratification whilst scanning Pp completing the ‘hot’ version of the go/nogo task. 43 trial.
Casey
Results?
Exp1: high and low delayers were 99.8% accurate in the correct response to the ‘go’ trials in both conditions.
Low delayers identified at age 4 showed greater difficulty suppressing their responses to happy faces than high delayers.
Exp 2: L delayers had a 14.5% false alarm rate in the hot task in no-go trials. There was high levels of activity in the reward related region for low delayers. Most prominent during happy no-go trials. Lowered activity in the inferior frontal gyrus and increased in the ventral striatum in low delayers.
Casey
Conclusions?
- Resistance to temptation seems to be a relatively stable characteristic of an individual over time.
- Cognitive control can be strongly influenced by contextual factors (e.g. hot cues) in alluring situations.
Blakemore and Cooper
Aim?
To investigate the effect on a kittens visual development of a restricted visual environment, consisting of either vertical or horizontal stripes only in which the animal could move freely.
B+C
Sample?
Lab raised kittens that were housed in complete darkness until 2 weeks of age
B+C
Method?
Lab exp. IMD
Kittens kept in complete darkness unless they were in the visual display apparatus or being tested. From 2 weeks-5 months kittens spent 5 hours a day in a visual display apparatus consisting or horizontal or vertical lines in a vertical cylinder,
DV measured by- after 5 months they spent several hours each week in a small well-lit room with chairs and tables. Observations on cats ability to move around and respond to objects.
From 7.5 months a physiological investigation of the direction or orientation on neurones in the visual cortex conducted to investigate how they responded to lines in terms or orientation and whether they were monocular or binocular.
B+C
Results?
The kittens eyes developed normally but behaviour and brains did not. Kittens moved around by touch rather than sight. Failed to stretch our paws when brought towards a table. Showed no startle responses when object moved quickly towards them. Deficiencies overcome within 10 hours of normal visual experience in the light- suggesting symptoms were caused by a failure to associate vision and movement.
Permanent defect:
The kittens failed to respond to objects in the orientation opposite to what they had seen. Neurons in the kittens brains each lacked cells responding to the orientation they hadn’t experienced. Horizontally reared cat- neurons respond around vertical axis.
75% neurons were binocular.
B+C
Conclusions?
- As there was no evidence that areas of the cortex were silent or that areas of cortical cells were missing, this suggests that the changes are a result of degeneration.
- Neurons change their preferred orientation according to the stimulation they experience, matching the ability of the brain to respond to features in its visual output.
Maguire el al
Aim?
To investigate differences in hippocampal volume between individuals who did, or did not have extensive navigational experience.
Maguire
Sample?
16 right-handed taxi drivers (32-62).
Experience: 1.5-42years. All medically, neurologically and psychologically healthy.
Matched Control: 50 right handed males (32-62) who had been scanned for the MRI database at Wellcombe DP of cognitive neurology.
Maguire
Method?
IMD- Snapshot study
Taxi drivers chosen as their job demanded a very high level of spacial understanding of locations and routes in london. Both experimental and control scanned in same MRI scanner by an unaware experienced individual.
Voxel-based mophometry- used to calculate volume of grey matter in different regions of the brain.
Pixel- counting slices of scan- 6 slices; posterior hippocampus, 12 slices; hippocampus body, 6 slices; anterior hippocampus.
Maguire
Results?
VBM showed that only the left and right posterior hippocampus had a signif difference between taxi drivers and controls.
Control- greater anterior hippocampal volume
Both- right hip. volume was greater than left
TD- poster hip. volume was significantly greater
Positive correlation r=0.6 (VBM) and r=0.5 (pixel counting) between time spent as a taxi driver and right hippocampal volume.
Maguire
Conclusions?
The distribution of grey matter in the hipp. changes with use, as the posterior hip. stores info about spacial relations in the env, Volume increases to respond to the demand for navigational skills.
