BIpsychology Yr 2 Flashcards
Sperry and Gazzaniga (1967) Split Brain research
Hemispheric lateralisation is the idea that each hemisphere is responsible for certain behaviours,processes and activities which contrasts the holistic theory of brain function and Sperry and Gazzaniga studied patients who underwent a cerebral commisurotomy in order to control their seizures and they showed support of Hemispheric lateralisation.
HIghly controlled lab studies in which only one eye was covered and a stimuli was shown for 1/10th of a second meaning only one hemisphere processed the information.
When Seeing words with the right eye, the left brain processes it and since left brain responsible for language, the patient can say word whereas when seen with the eft eye, right brain analyses and so they must write it with left hand since right brain contains visual-spatial centres. If multiple words present on each side, eye on right would say and eye on left would make left hand write and then read.
When seeing faces, only the right hemisphere can recognise faces or associate to a given stimuli since it contains visuo-spatial centres
When given objects in right hand, wouldn’t be able to identify since left brain has no visuo spatial centres whereas left hand, to right brain would
Split Brain Research Evaluation (Demonstration of function + Discussion + lacks control in samples)
The research by Sperry and Gazzaniga demonstrated lateralisation of function since it showed that the left hemisphere is dominant for languages and is more analytical whereas the right hemisphere is more dominant in visuo spatial tasks and is seen as the creative side
It also contributed in the discussion of dualism of the mind believing that the two hemispheres represent the two sides of the brain
Finally, it lacks sample comptroller since the patients used had cerebral commisurotomies due to their epileptic seizures and therefore before that they took strong anti epileptic medicine. This medicine would have changed their neuronal composition and therefore cant be generalised to the general public. This patients also had varying lesions meaning the connection between left and right brain was varied meaning the lateralisation could be an unreliable conclusion via uncontrolled factors
Localisation (evaluation)
Localisation suggests certain areas of the brain are mapped to specific functions
Motor Cortex - arranged in a logical way and responsible for fine motor movement
Auditory area - responsible for auditory information
Broca’s area - speech production
Wernickes area - speech comprehension
Visual Cortex - processes visual information
Somatosensory area - processes senses such as heat or touch
Left hemisphere responsible for language production and comprehension meaning language is localised and lateralised
Tulving Et Al found that semantic a memories recalled from the right prefrontal cortex where a episodic memories were recalled from the left prefrontal cortex supporting the idea of different regions being responsible for different functions
Phineas Gage’s incident caused problems in his rational decision making and processing of emotion supporting the idea that the brain was responsible for different functions- however can be argued that this case study lacked control and was subject to inaccuracies and misconceptions since it was so long ago
One limitation is that the holistic view argues functions need multiple parts of brain and this was showin with a study with mice where 25% cortices in rats were removed and found no difficulty navigating a maze meaning localisation can only support simple brain functions
Plasticity
Plasticity refers to brains ability to recover and change in response to trauma, new experiences or learning. IN Synaptic Pruning, number of synapses reduces as we get older to increase efficiency of neuronal transmissions
Maguire et al - found a positive correlation between volume of grey matter in hippocampus, which was known for spatial navigation, and the greater the time being a taxi drivers compared to non taxi drivers meaning increased grey matter correlated to specific job thus supporting plasticity
Functional recovery states that higher order functions can move to undamaged parts of the brain after trauma from
-equipotentiality
-axonal sprouting
-reformation of blood vessels
Meaning that functions aren’t specific to hemispheres and thus supporting plasticity
Plasticity Evaluation (Syndrome+foster)
One strength is of the phantom limb syndrome which was studied by Ramachandran and found that occurred when the sensory area invaded the motor area meaning there was great latent plasticity
Jodie miller had o have her left hemisphere removed due to her severe epilepsy and from neuroplasticity, she could still control right side of the brain using cerebral spinal fluid which demonstrated the power of neuroplasticity
Studying the brain scientifically FMRI
FMRI - functional magnetic resonance imaging works by detecting changes of blood flow since they are used by Neurons. Deoxygenated blood has a different magnetic quality and this can be used to detect a 3D map of the brain
A disadvantage of an FMRI is that they only show a direct measure of blood flow but don’t provide a direct measure of neuronal activity meaning no causation
Temporal resolution : FMRI’s are slow and images show what was happening 1-4 seconds before real time which is a disadvantage since it is delayed
Spatial Resolution : FMRI’s have a resolution of 1-2mm and this is an advantage because his is very accurate
Studying the brain scientifically (EEG / electroencephalogram)
Electroencephalograms detect electrical activity through electrodes attached to the scalp. THis electrical activity is the actionable potential of nerve impulses and these can have different amplitudes or frequencies. A change of amplitude will explain the complexity of an activity whilst a change in frequency will explain the speed or quantity of activity. EEGs can be used to detect epilepsy or diagnose Alzheimer’s via brain activity
Waves can be identified in different types ; Alpha,beta,theta or delta waves and thesewave forms are synchronised and can be recognisable whereas desynchronised waveforms have no recognisable pattern
- Alpha aves are associated with light sleep
- Theta and Delta waves are associated with deep sleep
Temporal Resolution : EEGs/ERP show activity every Millisecond which is very quick and real time
Spatial Resolution : Detect activity on superficial and general areas of brain meaning that isn’t accurate
Another limitation is that electrical activity can be picked up by multiple regions and this means hard to pinpoint region of activity
Studying the brain ERP and Post Mortem examination
ERPs are similar to EEGs but need a stimulus and researches look for activity detected from it. The response happens in multiple stages and is graphed with averaging. The difference in time between the observation and response to stimulus is called the latency
- In first stage, there is sensory ERP
- in second stage there is cognitive ERPS
Temporal and spatial resolution is the same as EEGs
One Strength is that its non invasive nd can detect mental processes when stimuli is present
Post Mortem Examinations study the physical brain e.g. Wernickes Area and studies such as Iverson’s Study show that deceased schizophrenic patients had higher concentration of dopamine in limbic system meaning that we can study neurochemical and anatomical changes which is more detailed than other techniques
2 limitations for Post Mortem examination is that
- damages in the brain could be other factors which may not be linked
- it is invasive and carries risk compared to other methods
Infradian rhythm
Infradian rhythms are longer than 24 hrs and an example of this is the menstrual cycle. This time of this cycle is influenced by hormones such as oestrogen and progesterone and can vary depending on external factors
Seasonal affective disorder is when melatonin secretion by the pineal gland in the night means more melatonin secretion in darker days and this melatonin can lead to depressive symptoms
Rheinberg (1967) studied a woman who spent 3 months in a cave with little artificial light and found that the menstrual cycle was rescued to 25.7 days which shows that light is an exogenous zeitgerbers which demonstrates the effect external factors have on infradian rhythms
Russel et al (1980) shows that menstrual cycles of women could synchronise through pheromones when rubbed on upper lip which suggests that pheromones are exogenous zeitgebers can affect others rather than themselves which may be an evolutionary tactic- study lacks ecological validity
Ultradian Rhythms
Ultradian Rhymths are less than 24 hours and an example is the human sleep pattern where in sleep, the average human goes through REM every 90 minutes. It is separated into stages
- 1&2 which are light sleep and where brain patterns become slower Alpha - Theta waves
- Stages 3&4 which are deep sleep and associated with delta waves
- Stage 5 is dram sleep and body is paralysed with brain waves becoming desnchronised
Randy Gardener was awake for 264 hour and afterwards only slept for 15 hours and vernichtet only recovered 25% of his sleep but 70% of his stage 4 sleep and 50% of stage 5 which shows the flexibility and of this rhythm and its variable nature
Tucker et al (2007) identified that the duration of stage 3 and 4 sleep varied widely person to person and this means there could be individual difference which need to be focused on - could lack ecological validity
