Dement & Kleitman I
Aims - To look at the association between REM sleep and dreaming; To look at the relationship between the length of REM time and the duration of dreams; To look at the relationship between the direction of eye movement and dream content.
Participants - 2 women and 7 men, 5 of whom were studied intensively while the other 4 were used to back up the other 5. All were asked to abstain from alcohol and caffeinated drinks on the day of the study but to do everything else normally.
Design - PPs were asked to report to the sleep labs at their normal bed times where they had EEG electrodes attached to their scalps and two EOG electrodes attached near their eyes. They slept in darkened rooms by themselves and were wakened throughout the night by a doorbell, either 5 minutes into REM, 15 minutes into REM or in NREM sleep. They were asked to speak into a recording machine when they woke about the content and duration of any dream they may have had. Their rapid eye movements (vertical, horizontal, both or neither) were also measured and the relationship between eye movements and dream content was found.
Dement & Kleitman II
Findings - All participants had a sleep cycle that lasted around 90 minutes with REM sleep lasting for an average of 20 minutes every night. 152 dream recollections were described from REM sleep while only 11 could be recalled in NREM sleep, and there was a positive correlation between the length of the dream and how much detail they could describe the dream in. PPs were accurate in their estimations of the dream durations 83% of the time. It was found that vertical eye movement suggested dreams such as looking up at a cliff face, horizontal meant throwing tomatoes and the like, both suggested talking to friends while no eye movement suggested staring at an object.
Conclusions - There is a link between REM activity and dreams, and rapid eye movement can be a measure of dreaming. However, we can't say that dreaming doesn't occur outside of REM sleep for sure yet.
Aims - To study the effects and any behavioural differences in split-brain patients; To map lateralisation of functions in the brain.
Participants - 11 American adults who had all had a commisurotomy (split-brain surgery) to help alleviate the sympttoms of epilepsy.
Design - PPs sat in front of a screen that had a gap underneath for their hands. They were asked to look at a fixation point in the centre of the screen as images were projected to the right and/or left of the fixation point for 1/10th of a second (the short time meant that pps couldn't move their eyes or head so the images would only be seen in their right and/or left visual fields). The pps then had to complete different tasks. Visual test 1: PPs looked at the fixation point with one eye covered and were asked to say, point to or draw what they saw in one visual field. Visual test 2: The object would flash up on both sides of their visual fields for the pp to say what they saw or draw it with their left hand. Tactile Investigations w/ 1 and 2 hands: An object was placed in one hand and they had to find it with that same hand and then identify it or two images were shown to the left and the right of the fixation point for the pp to pick an item from a pile based on what they saw and to identify what they were holding. Right hemisphere functioning: An image was shown in the LVF for the pp to find a similar object with their left hand; Simple maths problems shown to the left eye;
Design Continued - PPs were asked to sort objects into size and texture orders using their left hands; Nude images were shown to the pps and they were asked what they saw.
Findings - An image shown to one visual field can only be recognised by that same visual field. If the object was shown to the right eye/left hemisphere, the pps could name and point to the objects but objects shown to the left eye/right hemispheres could not be named and pps may say they saw nothing or only a flash of light but they could be pointed to or drawn with the left hand. In visual test 2, the pp would say that they saw the object in the RVF but would draw the item on the left; there was no communication between the pps' hemispheres. In the tactile tests, pps could name objects in their right hands but not their left and may not even be aware that there was something in their left hand. In terms of right hemisphere functioning, they could pick out similar objects to the ones shown in their LVF, they could complete the maths problems, could successfully order objects and would blush or giggle when they saw the nude picture but would be unsure as to why.
Conclusions - There are lateralisations of functions in the brain (e.g. the language centre is in the left hemisphere, but the right hemisphere does have some intelligence as it can order and sort objects, show emotional responses, etc.). The pps' brains acted as two seperate brains so the corpus callosum acts as a bridge and is vital in aiding communication between hemispheres.
Aim - To look at the changes in the form or shape (morphological change) in the human brain, specifically the hippocampi, associated with spacial memory
Participants - 16 right-handed, male, London taxi drivers who had been licensed drivers for more than 1.5yrs and had undergone two years of training to learn 'The Knowledge', plus a control group of 16 right-handed, male, non-taxi drivers.
Design - MRI scans were taken of the pps' brains and were analysed using voxel-based morphometry (VBM), which measured the size and shape of the brain regions by comparing the brains to templates generated from 50 healthy male brains and identifies the differences in the density of grey matter, and pixel counting, which is where the brain scans were split into 26 slices so that an independent expert counted the pixels in to calculate the hippocampal volume (single blind design).
Findings - The taxi drivers had increased grey matter in their left and right hippocampi compared to the control group but the rest of their brains were very similar. In addition, the taxi drivers had more grey matter in their posterior hippocampus whereas the controls had more in their anterior. There were no significant differences in the intercranial volumes and total hippocampal volumes between the different groups.
Findings Continued - The control group had a larger right anterior and body hippocampus than the left anterior and body hippocampus. The posterior hippocampi were larger in the taxi drivers when compared to the control group. Meanwhile, the amount of time spent as a taxi driver positively correlated with the size of the right posterior hippocampus but negatively correlated with the size of the right and left anterior hippocampi.
Conclusions - There was a relationship found between navigational skills and the size of the hippocampi, and the correlations between time spent as a taxi driver and the size of the hippocampi shows that the changes in the brain were due to spending time navigating, which favours the nurture debate. It also suggests that the brain has "local plasticity" to help us adapt and function effectively. The posterior hippocampi was found to have more to do with previously learned spatial memory while the anterior is more related to encoding new information, suggesting that there is functional/morphological differentiation within the hippocampus itself.