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Perceptual Systems - First Year Interest Group Seminar - Assignment 3 | N 1, Assignments of Health sciences

Material Type: Assignment; Class: FIRST-YEAR INTEREST GROUP SMNR; Subject: Nursing; University: University of Texas - Austin; Term: Spring 2009;

Typology: Assignments

Pre 2010

Uploaded on 08/30/2009

koofers-user-8d5
koofers-user-8d5 🇺🇸

10 documents

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Perceptual Systems

Assignment 3 Due Thursday, April 2, 2009

  1. (4 pts) The diameter of a foveal cone photoreceptor is approximately 2.5 microns. A peripheral cone is approximately 10 microns. What is a micron? What is the visual angle covered by an individual foveal cone? What is the visual angle covered by an individual peripheral cone.
  2. (6 pts) Consider a series of adjacent gray strips of paper with the following reflectance values: 0.1, 0.3, 0.4, 0.5, 0.8, 0.5, 0.4, 0.3, and 0.

(a) Suppose that the strips are uniformly illuminated with a light that this 150 photons/sec on each strip. What would be the intensity in photons/sec coming off the strips?

(b) Sketch the intensity distribution of the light reflected from the strips:

c) Sketch the approximate response distribution from the ganglion cells produced by this intensity distribution:

Spatial position

Response (spikes/sec)

Spatial position

Intensity (photons/sec)

  1. (5 pts) Using Excel, plot the one-dimensional intensity distribution of the a sine-wave grating with

a) contrast = 0.1, mean luminance = 10 b) contrast = 0.5, mean luminance = 100 c) contrast = 1.0, mean luminance = 10 d) contrast = 1.0, mean luminance = 100 e) contrast = 0.05, mean luminance = 100

  1. (5 pts) The function

( ) max

50

n n n

r c r c c c

has been used to described the shape of the contrast response function of cortical neurons. Using Excel, plot this function (sometimes known as the Naka-Rushton function or the Michaelis-Menton function) for the following values of the parameters:

a. r max = 10, c 50 (^) = 20 , n = 1 b. r max = 10, c 50 (^) = 20 , n = 2 c. r max = 10, c 50 (^) = 50 , n = 2 d. r max = 5, c 50 (^) = 20 , n = 2