Lectures3 4-Chapter_2-

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Unformatted text preview: o very slowly - continue to signal as long as the stimulus is present. 59 General principles of sensory coding - 4 Coding of sensory modality: We perceive different kinds of sensations because the different types of receptors (listed below) maintain a specific set of connections that ultimately stimulate brain regions that are primarily dedicated to each modality (the labeled-line principle). Sensory receptors are specialized for transforming different kinds of external stimuli into a biological signal and represent the starting point for modality coding in the nervous system. 60 Techniques for Studying Brain Function: Electrophysiology Involves recording the electrical activity generated by neurons Two main techniques: Single-unit recordings: Probe the activity of one of a few neurons Electroencephalography: Make recordings on the summated activity of large clusters of neurons 61 62 Single-unit recordings Thin electrode examines electrical changes caused by activity in surrounding neurons; first developed by Adrian in 1926. Signal is amplified before being displayed. Shows changes in membrane potential / currents across the membrane While most work pre-1980s used anesthetized animals, it is now more common to use awake ones (anesthesia effects, desire to study neural correlates of particular behaviors) Edgar Adrian (1889-1977) 63 Electroencephalography Uses surface-based electrodes that sample electrical activity over a larger area. Electroencephalogram (EEG) recordings detect electrical potentials on the skin surface that are due to the spatially-averaged activity of large ensembles of neurons beneath the skull. Event-related potentials (ERP) tie the electrical response to the presentation of a specific stimulus. Advantages: Good resolution for rapid time changes, noninvasive, and relatively quick and easy to perform Disadvantages: Because the brain is in a liquid medium (that conducts electricity well), very poor ability to resolve where in space the brain signals are coming from; may not be able to detect signals from parts of brain you are interested in studying (may be “drowned out” by other brain activity) Techniques for Studying Brain Function: Functional Brain Imaging Guided by the fact that there is an increase in energy demand and supply, and blood flow to brain areas that are active Measures changes in blood flow, uptake of labeled molecules associated with energy metabolism, or changes in neurotransmitter binding to different areas...
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This document was uploaded on 02/16/2014.

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