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Methods for Studying the Brain (The Insufficiency of Lesion Studies…

- - - - Believed function to be localised to specific brain areas
      - Reflected in phrenology (bumps on skull - phrenology)
    - - Reported a case of productive aphasia
      - Lesion in a specific area of the frontal lobe = Broca's Area
  - - - Challenged Gall's localist approach
      - Lesions to small specific areas in birds did NOT cause specific deficits
      - All animals recovered equally well regardless of lesion site
      - There are specific functions but mediated by the brain as a whole
    - - Function is shared by all neurones rather than being specific to one = Mass Action
      - Interested in the Cerebral Cortex in learning and memory
      - Claimed that memory is equally distributed throughout the CC and the participation of specific neurons was probabilistic not deterministic
      - Findings = Lesions to rat's neocortex in a maze learning task:
        Lesion size was related to the level of impairment
        Effect was independent of lesion location
- - - - Cellular composition of the cortex varies
      - Therefore, the way info is processed across the cortex cannot be uniform
      - Mapping the variation can distinguish cortical areas involved in different processing
    - - Flow of info across the brain is an important part of info processing
      - Understanding the architecture of these networks is important for understanding relationships between neural and cognitive processes
      - Animal studies - tracers injected into one end of a neuron are transported ---- Limitations: Tracer becomes diluted, can't trace whole circuit
      - MRI used to study the trajectories of fibre pathways in the brain = Diffusion Tensor Imaging (DTI)
  - - - Electric potentials produced by neurones is small but when several neurones are active together, the resulting signal can be measured by an electrode on the scalp
      - High temporal, low spatial resolution
    - - Measures the magnetic signal changes that results from changes in electric potential
    - - Measures changed in blood flow that are stimulated by changes in neural activity
    - - H atom's proton rotates on axis (magnet)- normally all randomly diffused
        Placed in magnetic field, the protons align in parallel
        Radiofrequency pushes the protons to their sides
    - - Haemoglobin can bind to up to 4 O2 atoms (BOLD) effect
        Deoxy changes the magnetic field