Single-unit Recording and Action (3) Flashcards
1
Q
What phenomenon did Georgopoulos et al. (1989) hypothesize?
A
- the use of imagery to make a mental rotation of an imagined movement vector
2
Q
What is mental imagery?
A
- experiencing a sensory impression in the absence of sensory input
3
Q
What is Kosslyn’s theory of imagery?
A
- imagery is spatial like perception
- similar to actually looking at a cat under the table
4
Q
What is Pylyshyn’s theory of imagery?
A
- spatial representation is epiphenomenon: meaning that the extent of feeling and perceiving is not what is going on and it is much more symbolic and abstract
- imagery is propositional: it can be represented by abstract symbols
- ex “The cat is under the table”
5
Q
What experiment did Shephard and Meltzer carry out?
A
- participants mentally compared two objects to see if they were the same or different
- mental chronometry
- IVs: object similarity and rotation angle
- DV: reaction time
6
Q
What is mental chronometry?
A
- used response time to infer the content, duration and sequencing of cognitive processes
7
Q
How did Shephard and Meltzer graph their data?
A
- x-axis: rotation angle
- y-axis: mean reaction time
- for the same shape reaction time was fastest at 0 degrees and slowest at 120 degrees
- for different shapes reaction time was constant and long for all angles
8
Q
What results can be made about Shephard and Meltzer’s data?
A
- larger angle had a longer reaction time for same trials because it takes longer to mentally rotate
- a large constant reaction time occurred for different trials because you have to rotate it the maximum amount
9
Q
From graph, how do we determine how long it takes to mentally rotate for a certain amount of degrees?
A
- subtract reaction time of x degrees from the reaction time of 0 degrees
10
Q
What question did Georgopoulos et al (1989) examine?
A
- what happens in the brain during the mental rotation of an action?
11
Q
What recordings did Georgopoulos use?
A
- extracellular single-unit recording in the motor cortex of awake behaving rhesus monkeys
- neuronal population vector calculated as the sum of vectors for individual neurons based on preferred direction and firing rate
- 102 cells
12
Q
What is graphed in the Georopoulos graphs?
A
- S: stimulus presented
- M: animal initiates movements
- x-axis: time, y-axis: population vectors
- population vectors calculated every 10 ms
- population vectors drawn from same origin
- direction vs time graph
13
Q
What do the rotation trials look like?
A
- lack of representation at beginning as processing of stimuli travels to motor cortex
- vectors start out pointing in direction of stimulus then slowly point to correct direction of movement
14
Q
How else was the data analyzed?
A
- rotation trials: summarizing data like an animation that shows rotation of population vector every 10 ms
- graph of speed of rotation (slope)
15
Q
What interesting conclusion was made?
A
- the population vector rotated consistently in the counter-clockwise direction
- suggests that the spatial-motor transformation is completed by a rotation through the shortest angular distance
