Exam 3 Study Guide
Psych 253
PSYCH 253: Introduction to the Psychology of Perception
Fall ‘21
Josh Wede
Study Guide for Exam 4
Exam Date: during class on Wednesday, Nov 17th
Lectures 15-16; Chapter 8 in book – Motion Perception
1. What is motion?
- Motion is relative change in position over time
- Start with two receptors
•Registers change in position
Incorporate a delay
•Accounts for change in time
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2. Understand how a Reichardt motion detector works.
•Cell "D" temporarily delays the
message from A to X.
•Only if X receives input from B and D simultaneously, will it send a motion message to M.
3.
-A simple motion detection circuit is based on a delay and compare principle. The unit
will only fire if signals from both detectors arrive at the comparator at the same time.
-detectors are tuned to particular speeds. If moving object is too slow or too fast, then
signals will arrive at the comparators at different times.
-detectors are also tuned to specific directions of motion. If an object moves in the
wrong direction, then signals will arrive at the comparators at different times.
Problem: Reichardt detector may respond to stationary patterns or flicker.
-Two Reichardt detectors tuned to opposite directions of motion. Outputs are subtracted
from one another.
-Reichardt detectors
-1. Neural circuits that enable the determination of direction and speed of motion
by delaying input from one receptive field, to determine speed, to match the
input of another receptive field, to determine direction
2. Neurons are sensitive to movement across the retina
3. Work well when the eyes are stationary
4. Only care about their preferred direction and speed
5. M pathway
a. V1
6. Hypothetical neural circuit describing how the brain might compute motion.
7. Responds to cortical cells
8. Detector fires when two photoreceptors fire in succession
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