L6 - Brain Mapping: Cognitive Neuroscience Toolbox Flashcards Preview

PSYC1020 - Introduction to Psychology - Minds, Brains and Behaviour > L6 - Brain Mapping: Cognitive Neuroscience Toolbox > Flashcards

Flashcards in L6 - Brain Mapping: Cognitive Neuroscience Toolbox Deck (7):
1

How do we measure Brain Function?

  • Lesion studies, Brain stimulation
  • Single neuron recording (animals)
  • EEG: Electroencephalography
    • ERPs: Event-Related Potentials
  • MRI: Magnetic Resonance Imaging
    • fMRI: Functional Magnetic Resonance Imaging

2

Limitations of Brain Mapping:

  • Cannot infer what people were thinking or doing or feeling based on measurement of their brain activity
  • Reverse inference: Cannot measure brain activity (dependent variable) to determine the independent variable was (i.e. task people were doing)

3

Neuropsychology– Brain Lesions:

  • Lesions: brain tissue can be damaged by injury, stroke, disease or surgery
  • Logic: “If area X does function Y, a lesion to X should impair Y”

Problems:

  • Injury is often extensive (more than just one tiny and exact area)
  • Impairment is often extensive
  • Compensatory” changes in other brain areas
  • Convenience sample – hard to control, can’t be generalised
    • Eg. There would be a lot of brain injuries during a war
  • Doesn’t take into account that the brain is a network

4

Single neuron recording:

  • Electrode in animals brain that detects AP firing of a single neuron
  • Allows measurement of what that neuron encodes (what causes it to fire); especially visual cortex
  • Pros: Most accurate measurement
  • Cons: Highly invasive, animals only

5

EEG (electroencephalography):

  • Summed activity from action potentials of neurons in the cortex cause electrical voltage changes on the scalp which can be measured with electrodes
  • Frequency of oscillations change between different states of alertness (narrow alpha waves which are compressed when concentrating) and sleepiness (wide delta waves)
  • Clinical uses: Detecting stages of sleep; monitoring for epileptic seizures

Subdural recording: cutting open the skull and putting a recording net of electrodes straight onto the brain

Scalp Recording: a cap covered in electrodes put on the head

6

ERPs (Event-Related Potentials):

  • Average of EEG +100 responses related to a specific event/stimulus
  • Peaks represent different stages of processing (e.g. face processing is related to a negative 170 (N170) peak)
  • Clinical uses: Detecting deafness in babies (auditory ERP's)
  • Pros: Provide precise time of information processing in the brain; Direct measure of electrical activity (neuron firing)
  • Cons: Difficult to accurately localise activity to specific brain areas (poor spatial resolution); hard to determine exactly where in the brain this activity comes from given the electrical potentials are being measured across the scalp

7

Functional brain imaging:

Change in blood flow associated with neural activity (↑ blood = ↑ activity)

  • PET (Positron Emission Tomography): Uses radioactive contrasts to map neurotransmitters or receptors (radioactively labelled “tracers”) in the brain
  • fMRI (Functional Magnetic Resonance Imaging): Measures changes in BOLD (blood oxygen level signal) rather than the anatomy of the brain (normal MRI)

    • ↑ Brain activity = ↑ Blood flow = Changes blood oxygen level = ↑ fMRI BOLD signal (detects iron in deoxy-Hb)

  • Pros: Good localisation of brain activity; non-invasive

  • Cons: Indirect measure; blood oxygen change is slowed and delayed (4-5 seconds after activity brain activity and lasts 10-12 seconds after cessation of activity); not very precise timing ; expensive