01:830:301 Lecture Notes - Lecture 3: Lesion, Neuropsychology, Action Potential

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7 Feb 2017
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The method of limits:
- Fixed set of stimuli
- Up sequences - start with weak (undetectable) stimulus, gradually increase intensity,
mark “crossover point”
- Down sequences
Some concerns:
- No “right answer” as to whether an individual saw or did not see the color
- Different people have differences in individual criterion/motivation level
To address such concerns, forced-choice methods are used
- Forced-choice methods - Subjects have to pick a given answer, set up task so there’s
always a right answer on every trial
- Exp: Dim light flashes either on left or right of screen, Question: Which side contained
the flash?
- 2 Alternatives Forced Choice Task - “2AFC” Task
- If invisible, observer has to guess, on average, ~50% correct
- If clearly visible: accuracy ~ 100%
Biological Approaches:
- Relationship between perception and brain events
- Doctrine of specific nerve energies (Johannes Muller)
- What matters is which nerves are stimulated not how they’re stimulated
1. Lesion studies (Neuropsychology)
- Natural or artificial
- Location (locus) of lesion <> loss in performance, you can find out which part of the brain
is responsible for what
- Difficulty in interpretation: correlation does not imply causation
- Ex. 1: Economy of San Francisco/Golden Gate bridge, Ex. 2: Radio transistor: “screech
suppressor”?
2. Single-cell recording
- Measure electrical activity from a single neuron, using a microelectrode
Neurons are specialized cells that integrate and transmit signals
1. Dendrites:
- Collect chemical signals
- Convert into electrical activity
2. Cell body:
- Integrates electrical activity
- Generates nerve impulses
3. Axon:
- Transmits nerve impulses
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