4.2.2 - Biopsychology

• The Nervous System - AO1

  CNS: 

  • Spinal cord-carries messages to and from the brain and connects nerves to the PNS.

  Responsible for reflex actions e.g. burn reflex∙

  • Brain - 2 hemispheres, conscious awareness and decision making. Cerebral cortex (3mm thick) is highly developed in humans and is what distinguishes our higher mental functions from those of animals 
• The Nervous System - AO1

  PNS: Receives and sends messages to the CNS via neurons

  • Autonomic nervous system- vital automatic functions e.g. breathing, heart rate, digestion sexual arousal and stress responses 
  • Sympathetic nervous system.  (fight or flight)
  • Parasympathetic nervous system (rest and digest)
  • Somatic nervous system- voluntary movement. Reflex responses. Takes in info from sensory organs e.g. eyes 
• The Nervous System - AO1


  diagram

  
• The Endocrine System - AO1

  -Based on hormones, works slower than the NS.

  Glands

  • organs that produce hormones. Pituitary gland located in the brain is the ‘master gland’ and controls the release if hormones from all other endocrine glands in the body. 

  Hormones

  • secreted into the bloodstream and affects any cell that has a receptor for thatparticular hormone.
• Fight or flight mechanism - part 1

  1. Stressor detected by the hypothalamus in the brain which activates the pituitary 
  2. Hypothalamus triggers the sympathetic branch of the ANS
  3. ANS changes from its resting state (parasympathetic state) to a state of physiological arousal (the sympathetic state)
  4. This triggers the adrenal glands to release adrenaline  (from the adrenal medulla) into the bloodstream which stimulates physiological changes
• Fight or flight mechanism - Part 2

  1. Adrenaline affects the cardiovascular system e.g. increasing heart-rate and breathing (and other bodily changes). These help us to confront the threat (‘fight’) or give us the energy to run away (‘flight’)homeostasis.
  2. Once the threat has passed the parasympathetic nervous system returns the body to its resting state (‘rest and digest’) through.
• Neurons

  A nerve cell in our body that communicates with other nerve cells using electrical and chemical processes.
• Relay neuron: 


  Connects sensory neurons to motor neurons. They also connect to other relay neurons and have short dendrites and short axons. Mostly found in the CNS, but also in the visual system
• Motor neuron:


   Carries messages from the CNS to effectors in our body, such as muscles and glands. Short dendrites and long axon- found in the PNS.
• Sensory neuron: 


  carry messages from receptors in the body (PNS) to the brain or the spinal cord (CNS). Found in the PNS- tend to have long dendrites and short axons
• Synaptic transmition - AO1

  Electrical impulse (action potential) passes down the axon of the presynaptic neuron and reaches the pre-synaptic terminal.

  This activates the release of the neurotransmitter from the vesicles. This diffuses across the synapse (as a chemical) and binds to the receptors of the postsynaptic neuron. 

  Neurotransmitters left in the synapse are broken down by enzymes and reabsorbed by the pre-synaptic neuron.

  The chemical message is converted back into an electrical signal and the process of electrical transmission begins
• Synaptic transmition - AO1 - Excitation and Inhibition:

  • Excitation:

   neurons that increases the then the post synaptic neuron’s positive and make it is more likely to fire an impulse e.g. adrenaline.

  •  Inhibition: 

  neurons that increase the post synaptic neuron’s negative charge and make it is less likely to fire an impulse. e.g. serotonin
• Synaptic transmition - Summation:

  excitatory and inhibitory influences are ‘summed’ and must reach a certain threshold to fire. Net effect on the post synaptic neuron is inhibitory =less likely to 'fire’. If excitatory=more likely to fire
• Localisation of function - AO1

  -Early 19th century, holistic theory suggested that all parts of the brain are involved in processing thought and action. Localisation suggests that specific areas of the brain (locations) are responsible for particular behavioural and cognitive processes (functions).

  
• Localisation of function - AO1

  The brain works contralaterally, generally the left side of the body is controlled by the right hemisphere and the right side of the body is controlled by the left hemisphere

  • Broca’s aphasia= problems producing speech (e.g. difficulty forming and remembering words, speaking slowly, lacking fluency).
  • Wernicke’s aphasia= problems understanding speech (e.g. using nonsense words and fluent, but meaningless speech
• Localisation of function - AO3

  + Case study Phineas Gage tamping iron through left PFC, change in personality. 
• Localisation of function - AO3


  + Support from Aphasia studies

  • Tan had Broca’s Aphasia, had a lesion on his left frontal lobe. Now known as the Broca’s area
• Localisation of function - AO3

  + Brain scanning studies.

  • Tulving semantic and episodic memories localised in different areas of the PFC. Peterson- activity in Wernicke’s area for a listening task and Broca’s area for a reading task
• Localisation of function - AO3

  -- Reductionist, 

  • Dronkers found 2 Broca’s patients (including Tan) had damage to other areas. Network of brain regions involved not one. Link to holistic theory, equipotentiality theory & plasticity.
• Localisation of function - AO3

  -- Use of cases studies

  • of unique cases with brain damage, difficult to generalise.
• Localisation of function - AO3

  -- Gender differences,

  • women tend to have larger Broca’s and Wernicke’s areas which would explain their greater ease of language use- beta bias. Differences in activation and size not considered
• Hemispheric Lateralisation and Split Brain Research - AO1

  Hemispheric lateralisation: 

  certain functions are principally governed by one side of the brain e.g. left is dominant for language, and the right excels at visual motor tasks. ‘Split-brain’= 2 hemispheres separated by surgically cutting the corpus callosum. Treats severe epilepsy, reduce ‘electrical storm’ across hemispheres and seziures and blackouts cease 
• Hemispheric Lateralisation and Split Brain Research - AO1 - Sperry

  M: 11 split-brain patients. Tachistocope was used to present images/words. Stare at fixed point, pps had one eye covered to avoid transfer of info to the other VF. All stimuli presented for 0.1secs

  R: Visual task. Objects shown to RVF (processed by the LH), pps could described what they had seen (due to language areas in the LH). 

  If shown to the LVF they could not name the object or often reported nothing was present (no language centres in the RH). 
• Hemispheric Lateralisation and Split Brain Research - AO1 - Sperry

  • Composite words: 

  2 words presented, one to each VF. E.g. Key- Ring.

  Could select a key with their left hand (RH) and could say ring (LH)

  • Tactile: 

  object place in right hand, they could describe it and select a similar object. Object placed in left hand, cannot describe, just wild guesses but could select a matching or similar object. 

  C:certain functions are lateralised. LH language

  (and RH visual motor/spatial)
• Hemispheric Lateralisation and Split Brain Research - AO3

  + High controlled and scientific.

  • Eye patch, image flashed for 0.1 secs no opportunity for info to be shared across VFs, standardised- high internal validity. 
• Hemispheric Lateralisation and Split Brain Research - AO3

  -- Small sample,

  • patients were atypical, epilepsy could have affected their brain functioning in the task/results. Cannot generalise to neurotypical sample. 
• Hemispheric Lateralisation and Split Brain Research - AO3

  -- Lack of control,

  • individual differences, disconnection between the hemispheres varied, some experienced drug therapy for longer than others. Control group were neurotypical, results may be due to epilepsy not just the split-brain  Confounding variable. 
• Hemispheric Lateralisation and Split Brain Research - AO3


  -- Lack of mundane realism,

  • unlike how they would process info in everyday life. Can use both eyes, so both hemispheres have access to the info. Plasticity also allows for compensation across hemispheres. Lack of external validity 
• Plasticity - AO1


  • Brain plasticity: 

  the brain’s ability to change and adapt as a result ofexperience. Neural connections can change and form at any time due to learning and experience.
• Plasticity - AO1


  • Synaptic pruning: 

  when neurons and synaptic connections are eliminated in order to increase the efficiency of neuronal transmissions. This happens as we age, frequently used connections are strengthened 
• Plasticity- AO1


  • Maguire‘s taxi driver study: 

  MRI scan found Taxi drivers (who all had taken ‘The Knowledge’) had a larger posterior (rear)hippocampal volume than matched controls (age, gender, all right-handed). This area is involved in spatial memory and navigational skill. Hippocampal volume positively correlated with the amount of time spent as a taxi driver
• Plasticity - AO1


  • Draganski:

   MRI of medical students at 3 different time points. 3 months before medical exam, 1st or 2nd day of exam and 3 months after . Learning-induced changes were seen in the posterior hippocampus and parietal cortex. Grey matter increased (presumably as a result of learning for the exam.)
• Plasticity - AO3


  + Applications to neurohabilitation,

  • e.g. movement therapy such as Constraint Induced Movement Therapy (CIMT), where restraint of unaffected arm is restrained and repetitive tasks with weaker arm encourages rewiring of the brain; this is applied to constraint-induced aphasia therapy requiring speech acts they have difficulty with.
• Plasticity - AO3


  + Some control over EV, 

  • All pps had healthy general medical, neurological, and psychiatric profiles. So unlikely to have impact brain structure. Matched on age and handedness. Images analysed by blind researcher (did not know if it was a taxi driver or control) Increased validity 
• Plasticity - AO3


  -- Limited sample size and all males,

  • gender differences hippocampal structure and functionality. May not generalise. 
• Plasticity - AO3


  -- Correlational, cannot establish cause and effect. MRI scans only after the knowledge. Those with larger hippocampi may chose to become taxi drivers 
• Plasticity - AO3


  + Draganski longitudinal,

  • can observe incremental structural changes in the brain before and in response to learning. Possibility of cause and effect conclusions more likely than in Maguire.
  • CA: - Draganski age bias, used students in their 20s 
• Functional recovery of the brain after trauma - AO1

  • Functional recovery is an important example of neural plasticity.    It refers to when unaffected areas of the brain take over the functions of damaged, destroyed or missing areas -equipotentiality
  • Neuroscientists suggest this occurs quickly after trauma (spontaneous recovery) and then slows down- then a person may require neurohabilitation
• Functional recovery of the brain after trauma - AO1 - Structural changes:


  • Neuronal unmasking: 

  secondary neural pathways which are normally unused (dormant) due to the neural input into them being too low, are activated (unmasked) to enable functioning to continue. 
• Functional recovery of the brain after trauma - AO1 - Structural changes:

  • Axonal sprouting: 

  undamaged axons grow new nerve endings which connect to other undamaged nerves to form new pathways or damaged ones to repair the connection