Biological Approach Flashcards
Define localisation
Specific functions have specific locations in the brain
Broca’s Area (localisation)
Left frontal hemisphere responsible for language production discovered through patients with production aphasia
Method for Broca’s Area (localisation)
A case study of a Frenchman who could only say the word “Tan” but could understand speech and follow instructions
- Studied symptoms and did autopsy to find damage in left frontal
- Studied further with 25 cases
Results for Broca’s Area (localisation)
All had damage to the same area with same condition
Conclusion for Broca’s Area (localisation)
Supports localisation since that area was responsible for speech production
Evaluation for Broca’s Area (localisation)
Small sample size limits generalisation (one case study)
Maguire study (Aim)
Investigating the brains of London taxi drivers to investigate size of posterior hippocampus
- Taxi drivers undergo intensive training programme to navigate city known as ‘The Knowledge’
Method (Maguire)
- 16 right-handed male licensed taxi drivers (2 year training, 14 years experience)
- MRI scans of control Ps compared with MRI scans of Ps
Results (Maguire)
Taxi drivers had significantly more volume in posterior hippocampus than control (28% larger)
- posterior hippocampus: used in spatial and navigational skills
Conclusion (Maguire for localisation)
supports localisation since a larger volume of that area displays that section constantly being used (has a specific function)
Greater neural density as localised plasticity processes have developed neural pathways there showing that there is greater demand for function in that area
Evaluation (Maguire for localisation)
- All right-handed so limited generalisation towards left-handed (all male too)
- Reductionist as it looks at one specific area of the brain only
Critical thinking of localisation
- Neuroplasticity argues against localisation that brain can change and adapt over time (not a fixed entity)
- Evidence of interdependence instead of dependence, brain regions must interact with each other to work with research finding damaged connections between the visual cortex and Wernicke’s area lead to losing the ability to read suggesting complex behaviours built on connections between areas
Neuroplasticity
- Define
The ability of the brain to change and adapt its structures and processes as a result of development or experiences of new learning
- neural connections can be made and changed
- each neuron is connected to many others and these new connections create neural networks
Experience dependent plasticity
The brain’s adaptation to change in response to environmental experience across the lifespan
Dendritic branching
A response to environmental demands where connections between existing neurons will become stronger due to intense demand.
- Result is much greater synaptic density (more connections)
Synaptic pruning
Neural networks where are rarely used as ‘pruned away’ allowing connections which are in more regular use to be strengthened and work more efficiently
Maguire - conclusion for neuroplasticity
Supports experience dependent plasticity and dendritic branching since learning and constant application of ‘The Knowledge’ altered structure of taxi driver’s brain (intense demand)
- increased brain matter in posterior BUT control Ps had more matter in anterior suggesting distribution of grey matter
Evaluation (Maguire for neuroplasticity)
- Quasi experiment so cause-effect cannot be assumed (could be people with larger posterior hippocampus are predisposed to that profession)
BUT positive correlation of +0.6 where longer experience = larger volume increase
Critical Thinking of neuroplasticity
- Neuroplasticity can make the brain more efficient due to stronger connections in regularly used areas and is an ongoing dynamic process
- Challenges concept of localisation and is more applicable in recovery of patients from physical and cognitive deficits
Draganski Neural pruning and neural networks (Aim)
To see whether learning a new skill (juggling) would have an effect on the brains of Ps
Method (Draganski)
neural pruning
- Ps were 24 volunteers between ages 20-24 (21 female and 3 male) – non-jugglers
- Each P had a MRI scan at the start of the study as a base rate for grey matter and brain structure
- Condition 1 (Jugglers): Ps taught a 3-ball cascade juggling routine and asked to practice and notify when mastered; then had a second MRI and told not to juggle anymore; third MRI 3 months later
- Condition 2: Control group
Results (Draganski)
neural pruning
- Researchers used voxel-based morphometry (VBM) to determine if there were significant differences in neural density (grey matter) between Ps and control
- Second MRI: jugglers had significantly larger amount of grey matter in mid-temporal area (visual memory are) ; neural networks strengthened
- Third MRI: amount of grey matter in these parts had decreased so evidence of neural pruning
Conclusion (Draganski)
neural pruning
supports neural pruning since when pathways required for juggling were no longer being used they were pruned
- Neurological pathways were also stimulated to create stronger pathways (neural networks strengthened)
Neurotransmitters and their effects on behaviour
- Describe neurotransmission
- Electrical signal (action potential) travels down axon of presynaptic neuron
- Action potential arrives at terminal button of neuron (end of axon and contains vesicles filled with neurotransmitters) and causes versicles to rupture, releasing neurotransmitters into synapse (electrical signal converted to chemical one)
- Neurotransmitters move across synapse and bind to receptors on the dendrites of post-synaptic neuron (specialised to recognise chemical)
- Chemical message converted to electrical AP and transmission begins again in same neuron
- Unused neurotransmitters are absorbed back (aka reuptake)
Excitatory neurotransmitters
More likely that the neuron will fire, excitatory synapse
e.g Adrenaline
Inhibitory neurotransmitters
Less likely that neuron will fire, inhibitory synapse
e.g Serotonin
Agonist
A substance which binds to receptors in the brain to increase activity (activates receptor)
- Endogenous: in body
- Exogenous: outside body, mimicking action of endogenous agonist
Antagonist
A substance which blocks receptors in the brain and reduces the effects of neurotransmitters
Martinez and Kesner (Excitatory, Agonist, Antagonist)
- Aim
- Role of Acetylcholine
To investigate the role of the neurotransmitter acetylcholine (ACh) on memory
- ACh is an excitatory neurotransmitter which causes neurons to fire and allow the transfer of information from short-term memory to long-term memory in mice (many ACh receptors found in hippocampus, area responsible for memory)
Method (Martinez and Kesner)
excitatory, agonist, antagonist
- Mice were placed in a maze that had food hidden in one end. Having completed the maze, they were given one of 3 treatments and placed back in the maze and timed to see when they would find the food.
- Condition 1: Injected with scopolamine (Antagonist) which blocks ACh and decreases its availability
- Condition 2: Injected with physostigmine (Agonist) which inhibits enzyme that destroys ACh in the synapse, increasing ACh availability
- Condition 3: control (placebo)
Results (Martinez and Kesner)
excitatory, agonist, antagonist
Condition 1: slowest times for completion of maze
Condition 2: fastest time
Order: 1 > control > 2
Conclusion (Martinez and Kesner)
excitatory, agonist, antagonist
Supports the idea that he more acetylcholine is available, the more productive memory formation is. This can be concluded because condition 3 rats were in-between the other two conditions in terms of maze-completion time.
Evaluation (Martinez and Kesner)
excitatory, agonist, antagonist
- Very high levels of control (lab experiment)
- Application to humans as the same chemicals are present in humans with low levels of ACh found in Alzheimer patients
- Ethics to do with animal testing with not full applicability to humans
Crockett (Serotonin as an inhibitory neurotransmitter)
- Aim
- Role of serotonin
Aim: Effect of serotonin on pro-social behaviour
- Serotonin: chemical to promote ‘happy’ moods
Method (Crockett)
inhibitory
- Condition 1: Ps given a SSRI (boosts serotonin concentration and prolongs its effects)
- Condition 2: Ps given a placebo
Ps were then given a series of moral dilemmas such as the trolley problem where they had to choose between saving 5 people by pushing a man off the bridge to block the train from hitting the 5 people further down the track .
Results (Crockett)
inhibitory
After receiving SSRI, Ps were less likely to push a man off a bridge to save 5 lives than Ps in a placebo condition.
Conclusion (Crockett)
inhibitory
Opposition to pushing a man becomes even stronger when serotonin levels are increased showing serotonin modulates reaction to certain stimuli inhibiting the acceptability of inflicting harm which promotes social behaviour.
Evaluation (Crockett)
inhibitory
- Hypothetical situation so may not truly reflect their actions in real world
- Social desirability bias: changing decision to seem more favourable
- Low ecological validity: may not happen in the real world (artificial)
Critical Thinking of neurotransmitters and their effects on behaviour
- Theory is reductionist to assume ‘single substance’ neurochemical explanation as recent research suggests a number of specific factors (availability of serotonin, receptor sensitivity, genes) might produce specific behaviours
- Single substance allows creation of medication targeted at specific imbalances to help reduce symptoms in patients (may not give causal explanations but offers relief from symptoms)
- Neurotransmitter levels are difficult to measure, found in cerebrospinal fluid (painful process) so most studies use indirect ways of measuring neurotransmitter levels
Hormone and behaviour
- Function of hormones
- Hormones travel with blood, regulate long-term ongoing processes (growth, metabolism) and allow for lesser voluntary control
(nervous and endocrine system are independent) - Hormone are released by endocrine glands, generally in response to situations or experiences by physiological and behavioural altercations
- Hormones only influence cells with receptors for particular hormones (target cells) so when a hormone binds to the receptor it launches a sequence of changes (gene activation or suppression)
- Hormones do not influence behaviour directly but change the probability of a certain behaviour in response to a stimulus
Oxytocin (role and where its produced)
- Produced in the hypothalamus and released into the blood by the pituitary gland to the amygdala (responsible for emotion)
- Known as the “love hormone” and responsible for forming and maintaining social bonds
Baumgartner (aim)
hormones
Role of oxytocin on trust
Method (Baumgartner)
hormones
- fMRI study on brain activity during game (49 Ps)
- trust game of two individual groups one with oxytocin via a nasal spray and other received placebo
- Game procedure:
- 1st P (investor) given a sum of money and had the choice of keeping it or sharing with trustee and have it tripled
- Dilemma of trusting since trustee can choose to repay trust or violate it
Results (Baumgartner)
hormones
- Placebo: when they had their trust betrayed, became less trusting in the following rounds
- Oxytocin: continued to trust despite being betrayed once
- fMRI results displayed brain activity in amygdala and caudate nucleus with placebo but minimal brain activity for those with oxytocin