Brain Electrical

• What should students be able to describe regarding electrophysiological recording techniques?

  How they provide a means of understanding activity in single neurons in the brain
• What should students be able to describe about electroencephalography (EEG)?

  How it provides a means of understanding activity in populations of neurons in the brain
• What is single cell electrophysiology and its characteristics?

  • Also known as single cell neurophysiology or single unit recording
  • Measures the response of a single neuron
  • Invasive technique
  • Types of recording: intracellular (inside axon) and extracellular (outside cell membrane)
  • Metric: spikes per second
• What is the difference between in vivo recordings from anaesthetized and awake behaving animals in single cell electrophysiology?

  Anaesthetized animals are heavily sedated during surgery, while awake behaving animals are trained to perform tasks after fixed with recording apparatus
• Why are monkeys often used in single cell electrophysiology experiments?

  Because they have similar brains to humans and can be trained to perform behavioral tasks
• What did Hubel and Wiesel discover about cells in the primary visual cortex of cats?

  • Cells are selective for:
  • Orientation
  • Size
  • Motion direction
  • Speed
• What is the main purpose of single cell electrophysiology?

  To measure the electrical activity of a neuron in response to environmental stimuli
• What does electroencephalography (EEG) measure?

  • Measures dendritic currents in neuronal populations
  • Records electrical signals generated by the brain
  • Uses electrodes placed at different points on the scalp
  • Non-invasive technique
• How are electrodes characterized in EEG recordings?

  • According to their location:
  • F = frontal
  • P = parietal
  • O = occipital
  • T = temporal
  • C = central
  • Odd numbers for left of midline, even numbers for right, midline is 'z'
• How is the time-course of the EEG signal quantified?

  • Using an Event-Related Potential (ERP)
  • Waveform plotted as electrode potential (microvolts) over time (milliseconds)
  • Positive peaks labeled as P and negative peaks as N
  • Peaks numbered as P1, P2, P3, etc., and timed as P300, P400, etc.
• What is required to gain an EEG measure?

  • Comparison between two or more different brain sites
  • Common reference point: mastoid bone behind the ears
  • Need to isolate the 'signal' from noise
  • Increase signal-to-noise ratio by averaging EEG over multiple presentations of a stimulus
• What does EEG measure in terms of electrical impulses?

  It measures the amplitude and timing of electrical impulses produced by groups or populations of neurons in the brain
• What are the temporal and spatial resolutions of EEG?

  EEG has good temporal resolution but not great spatial resolution