4.2.2 - Biopsychology

• The Nervous System


  • CNS: Spinal cord, Brain
  • PNS: Receives and sends messages to the CNS via neurons, Autonomic nervous system, Somatic nervous system
• 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
• Autonomic nervous system


  Vital automatic functions e.g. breathing, heart rate, digestion sexual arousal and stress responses
• Autonomic nervous system


  • 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 Endocrine System


  • Glands, Hormones
• 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 that particular hormone
• Fight or flight


  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

  5. 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')

  6. Once the threat has passed the parasympathetic nervous system returns the body to its resting state ('rest and digest') through homeostasis
• Neurons


  • Sensory neuron, Relay neuron, Motor neuron
• 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
• 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
• Axon


  Carries the signal from the cell body down the neuron
• Synaptic transmission


  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
• 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
• 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


  • 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


  • Case study Phineas Gage tamping iron through left PFC, change in personality
  • Aphasia studies- Tan had Broca's Aphasia, had a lesion on his left frontal lobe. Now known as the Broca's area
  • 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
• Criticisms of localisation of function

  • Reductionist, Dronkers found 2 Broca's patients (including Tan) had damage to other areas. Network of brain regions involved not one
  • Use of cases studies of unique cases with brain damage, difficult to generalise
  • 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
• 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)
• 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
• Strengths of split-brain research

  • High controlled and scientific. Eye patch, image flashed for 0.1secs no opportunity for info to be shared across VFs, standardised- high internal validity
• Weaknesses of split-brain research

  • Small sample, patients were atypical, epilepsy could have affected their brain functioning in the task/results. Cannot generalise to neurotypical sample
  • 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
  • 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
• Sperry studied 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
• Findings from Sperry's split-brain research

  • 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)
  • 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
• Certain functions are lateralised. LH language (and RH visual motor/spatial)
• Brain plasticity


  The brain's ability to change and adapt as a result of experience. Neural connections can change and form at any time due to learning and experience
• 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
• Brain plasticity


  • 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
  • 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
• Strengths of Maguire's taxi driver study

  • 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)
• Weaknesses of Maguire's taxi driver study

  • Limited sample size and all males, gender differences hippocampal structure and functionality. May not generalise
  • Correlational, cannot establish cause and effect. MRI scans only after the knowledge. Those with larger hippocampi may chose to become taxi drivers
• Strengths of Draganski's study

  • 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
• Weaknesses of Draganski's study

  • Age bias, used students in their 20s
• Functional recovery


  Unaffected areas of the brain take over the functions of damaged, destroyed or missing areas - equipotentiality