Biopsychology Paper 2

• The nervous system

  • primary internal communication system
• Divisions of the nervous system

  • Central nervous system - passes messages to and from the brain and connects nerves to the peripheral nervous system:

  1. Brain
  2. Spinal cord

  • Peripheral nervous system - transmits information to and from the CNS and splits into:

  1. Somatic nervous system - controls skeletal muscles and receives information from sensory receptors
  2. Autonomic nervous system - regulates glands and organs and governs vital functions. Further divides into:
  3. Parasympathetic NS - rest and recovery
  4. Sympathetic NS - prepares body for action
• Differences between SNS and ANS

  • SNS = sensory and motor pathways, ANS = only motor
  • SNS = controls muscles and movement, ANS = controls organs and glands
• Neurons

  • there are 100 billion nerve cells in the nervous system
  • transmit signals electrically and chemically to allow communication
  • The cell body includes a nucleus and dendrites protrude from the cell body, which carry nerve impulses to the cell body
  • axon carries the impulses away and is covered in a myelin sheath that speeds up electrical transmission
  • The myelin sheath has nodes of Ranvier speed up the transmission of the impulses
  • At the end of the axon are terminal buttons that communicate with the next neuron
• Motor neurons

  • connect the CNS to muscles and glands
  • they carry messages away from the brain.
  • They have short dendrites and long axons.
  • they are primarily concerned with generating movement
• Sensory neurons

  • carry messages such as sight, sound and sensations from the PNS to the CNS
  • They have long dendrites and short axons.
• Relay neurons

  • connect sensory neurons to motor neurons, or to other relay neurons
  • only found in CNS
  • They have short dendrites and short axons.
• Simple reflex response

  1. The sensory neuron detects the stimulus
  2. It sends a signal to a relay neuron in the CNS
  3. This sends a signal to the motor neuron to produce a response 
• Synaptic transmission

  • an electrical impulse travels down the axon towards the end of the presynaptic neurone 
  • chemical messengers called neurotransmitters are released from the synaptic vesicles
  • The neurotransmitters diffuse across the synapse and  bind with receptor sites on the postsynaptic neurone
  • The excitatory and inhibitory neurotransmitters are summed, and if the net effect is inhibitory, the neutron is less likely to generate an action potential, and if the net effect is excitatory, the neuron will be more likely to fire
• Types of neurotransmitters

  • inhibitory - decrease the chance of the postsynaptic neuron from firing, e.g. GABA
  • excitatory - increase the chance of the postsynaptic neuron from firing, e.g. glutamate
• What is the endocrine system?

  •  network of glands that secrete hormones into the blood stream to regulate many bodily functions
  • e.g. testosterone - produced by the testes - causes the development of male characteristics and sperm production.
  • e.g. thyroxine - thyroid gland - regulates metabolism
  • acts more slowly than the nervous system but has very widespread effects
• Fight or Flight response

  • the fight or flight response has evolved as a survival mechanism and is activated in stressful situations
  • The amygdala senses fear and sends distress signals to the hypothalamus.
  • This activates the sympathetic NS which sends a signal to the adrenal medulla which secretes adrenaline
  • The role of adrenaline is to prepare the body
  • Adrenaline has a range of effects on the body: increased heart rate, increases respiration and perspiration. 
  • Once the threat has passed, the parasympathetic NS returns the body to its resting state
• Evaluation of the fight or flight response

  • The fight of flight response is likely to have evolved as a response to threats posed for our ancestors, which is an inappropriate response to modern stress and creates panic and anxiety
  • Taylor argued that studies into the fight or flight response were based on males animals and do not reflect responses to stress shown by females - they are more likely to ‘tend and befriend’
  • Von Dawans et al challenge the view that men respond with fight and flight, and women tend and befriend, finding stress can lead to co-operation and friendly behaviour
• What is localisation of function?

  the theory that specific areas of the brain are associated with particular functions
• What is hemispheric lateralisation?

  • the dominance of one hemisphere of the brain over the other for particular functions
• Motor cortex

  • located at the back of the frontal lobe.
  • responsible for voluntary motor movements. 
  • the right hemisphere is responsible for the left side of the body’s movement and the left hemisphere is responsible for the right. 
• Somatosensory cortex

  • located in the parietal lobe, behind the motor area. 
  • produces sensations of touch, pressure, pain and temperature, which it localises to specific body regions. 
  • Both hemispheres have a somatosensory cortex, with each hemisphere receiving sensory information from the opposite side of the body. 
• Visual centre

  • primary visual centre is the visual cortex in the occipital lobe. 
  • information is sent from the retinas to the brain via the optic nerve.
  • Most information then travels to the thalamus, which passes this information to the visual cortex. 
  • each hemisphere receives information from the visual field of the opposite side. 
• Auditory centre

  • Located in the temporal lobe. 
  • The auditory pathway begins in the cochlea where soundwaves are converted to nerve impulses which travel via the auditory nerve to the auditory cortex.
• Language areas - Broca's and Wernicke's areas

  •  Broca's area - located in the frontal lobe of the left hemisphere. essential for speech production after post-mortems revealed patients with lesions in this area could understand language, but could not express spoken language
  • Wernicke’s area - located in the temporal lobe of the left hemisphere. responsible for language comprehension after post-mortems revealed patients with lesions in this area could speak, but not understand language. 
• Evaluation against localisation

  • Lashley studied rats ability to learn a maze & found basic functions were localised, but higher functions (navigation) weren't 
  • Research suggests communication between areas is more important e.g. couldn't read after damage to the connection between the visual cortex & Wernicke’s area.  
  • plasticity questions localisation
  • Dougherty - OCD patients had neurosurgery, and found 1/3 had a successful response to surgery & 14% had a partial response, suggesting that symptoms of serious mental disorders are localised but over 50% didn't improvement
• Hemispheric lateralisation

  • the left and the right sides of the brain are very similar
  • One difference is the language areas are mainly found on the left hand side, meaning the neural mechanisms for language are located in the left half of the brain in most people. 
  • Research has found that the right hemisphere excels at visual attention tasks and face recognition, indicating that these functions are hemispherically lateralised.
  • The two hemispheres are connected which allows information received by one hemisphere to be sent to the other hemisphere through the corpus callosum. 
• Sperry’s Split Brain Research

  • image was projected to a patient’s right visual field (left hemisphere) and another was projected on the left visual field (right hemisphere)
  • normally, the corpus callosum would share the information between both hemispheres, but in split-brain patients, the information could not be conveyed
  • When a picture of an object was shown to a patient’s right visual field, patients could describe it; but when shown to the left visual field, the patient could not describe what was seen
  • This indicates that the language centres are in the left hemisphere
• Evaluation of Sperry

  • high control, with standardization, meaning findings would have been internally valid. 
  • has contributed a greater understanding of brain processes and lateralisation i.e. that the left hemisphere is more geared towards verbal tasks and the right more visual. 
  • Issues with generalising as split brain patients constitute such an unusual sample of people.  
  • all 11 participants had a history of epileptic seizures which may have caused unique changes in the brain that may have influenced the findings.  
  • some participants had experienced more disconnection of the hemisphere
• Evaluation of hemispheric lateralisation

  • Lateralisation changes with age - lateralised patterns found in younger individuals tend to switch to bilateral patterns in healthy adults. 
  • Differences in function may be overstated with psychological literature that overemphasises and oversimplifies the functional distinction between left and right hemispheres.
  • Individual differences -although 95% of right-handed people have left-hemisphere dominance for language, nearly 20% of left-handed people have right-hemisphere dominance for language function, and 19% have bilateral language functions
• Brain plasticity

  • the brain’s ability to change and adapt as a result of experience. 
  • During infancy, the brain experiences a rapid growth in the number of synaptic connections it has, peaking to about 15,000 before synaptic pruning occurs as we age
  • Although the brains of young children exhibit more plasticity than older adults, research suggests that at any time in life, existing neural connections can change as a result of learning and experience
• Functional recovery following trauma  

  • Following injury or trauma, unaffected areas of the brain are often able to adapt and compensate for areas that are damaged.
  • This functional recovery is an example of plasticity
  • this process can occur quickly after trauma (spontaneous recovery) and then slow down
  • The brain is able to reorganise itself by forming new synaptic connections close to the area of the damage
  • Secondary neural pathways that would not typically be used to carry out certain functions are activated to enable functioning to continue
• Ways of functional recovery:

  1. Axonal sprouting - growth of new nerves connecting with undamaged nerve cells to form new neuronal pathways.

  2. Neuronal unmasking - dormant synapses in the brain whose function is blocked is ‘unmasked’ when a surrounding brain area becomes damaged due to increasing the rate of input to these synapses, allowing the development of new structures.

  3. Recruitment of homologous areas - if an area is damaged on the left side of the brain, the right-sided equivalent would carry out its functions, after a period of time, functionality may shift back
• Evidence for plasticity 

  • Kemperman found an increased number of new neurons in rat brains who were in complex environments compared to caged rats.
  • Maguire et al studied brains of London taxi drivers and found more grey matter in the hippocampus than the control group, suggesting the result of the ‘The Knowledge‘ is to alter their brain structure
  • Hyde et al studied the effects of music training in children, finding significant increases in brain tissue in motor and auditory areas
  • Zattore found the effects of music training were greater among children, suggesting plasticity declines
• Evidence for recovery from trauma 

  • studies have suggested that abilities commonly thought to be fixed in childhood can still be modified in adults with intense retraining.
  • Ballantyne et al found there is more plasticity for recovery after a stroke in childhood than in adulthood. 
  • Schneider found that patients with college education are 7 times more likely than those who didn’t finish high school to be disability-free one year after a moderate - severe traumatic brain injury, just 10% of those with less than 12 years of education achieved DFR after one year
• Functional Magnetic Resonance Imaging (fMRI) 

  • measures changes in blood flow in particular areas of the brain which indicates increased neural activity in those areas.
  • If an area becomes more active, there is an increased demand for glucose and oxygen, which results in increased blood flow, which is detected by the fMRI. 
• Evaluation of fMRI

  • It is non-invasive and does not expose the individual to harmful radiation unlike CT scans and PET scans
  • it is not a direct measure of neuronal activity in areas of the brain, so it is difficult to tell what kind of activity is occurring in these areas. 
  • fMRI overlooks the networked nature of brain activity, as it focuses on localisation.
  • Compared to PET scans, it has better temporal resolution and spatial resolution, depicting detail by the mm
• Electroencephalogram (EEG) 

  • measures electrical activity in the brain via electrodes that are fixed to an individual’s scalp
  • The recording represents the brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity
  • EEG is often used by clinicians as a diagnostic tool because unusual patterns of activity may indicate neurological abnormalities such as epilepsy
• Evaluation of EEG

  • EEG has high temporal resolution, meaning researchers can accurately match a task with the brain activity recorded. 
  • The EEG signal is not useful for pinpointing the exact source of neural activity, and it does not allow researchers to distinguish between activities originating in adjacent locations. 
  • EEG’s cannot tell us about activity in deeper parts of the brain
• Event-related potential (ERP)

  • ERPs are small voltage changes in the brain that are triggered by specific events or stimuli
  • To find a specific response to a target stimulus requires many presentations of the same stimulus. These responses are then averaged together.
  • Any extraneous activity that is not related to the specific stimulus will not occur consistently
• Evaluation of ERPs

  • These can measure neural processes more accurately than using raw EEG data
  • In order to establish pure data in ERP studies, background noise and extraneous material must be completely eliminated, meaning a large number of trials are needed. 
  • Important electrical activities occurring deep in the brain are not recorded,
  • They have excellent temporal resolution which has led to their widespread use in the measurement of cognitive deficits. 
• Post-mortem Examinations (PME’s) 

  • the analysis of a person’s brain following their death.  
  • it is often used in those who have a rare disorder or particular difficulties in mental processes or behaviour during their lifetime.
  • Areas of damage within the brain are examined after death as a means of establishing the likely cause of the affliction the person suffered
• Evaluation of PME’s

  • allow for a more detailed examination of the brain than would be possible with the sole use of non-invasive techniques
  • it enables researchers to examine deeper areas
  • Observed damage to the brain may not be linked to particular behaviours
  • it is retrospective as the person is already dead, so the researcher is unable to follow up on anything that arises from the PME concerning a possible relationship between brain abnormalities and cognitive functioning. 
• Circadian rhythms

  • changes in biological activity over 24hrs.
  • These include metabolic changes and the sleep-waking cycle. 
• Infradian rhythms

  • changes in biological activity over a time period greater than 24 hours, e.g.  menstrual cycle.