Chapter 1. Center Surround Fields

1.1 Introduction

Cognitive Tool Kit

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Center Surround Fields

In this experiment, you will examine a feature of the visual system. As cognitive psychology has developed, the understanding of the brain, neuroscience, has become more important. The study of the brain holds many surprises and often forces us to revise our ideas. In the 1950s it became possible to use an electrode to record the activity of a single neuron. Stephen Kuffler (1953) took advantage of this new technology to record activity in the ganglion cells in the retina, where axons make up the optic nerve that carries visual information from the eye to the brain. He anesthetized a cat and found a ganglion cell in the retina. He could find the cell because, even in the dark, neurons fire action potentials at a slow, steady pace. When the electrode penetrated the ganglion cell, clicks would sound over the speaker to which the electrode was connected. When a cell was found, Kuffler would present different stimuli on a screen in front of the cat and see what happened to the cell. Since these are the cells that carry information from the eye to the brain, what happens in the cell has important implications for how we see and experience the world.

References:

Enroth-Cugell, C. & Robson, J. (1966). The contrast sensitivity of retinal ganglion cells of the cat. Journal of Physiology, 187, 517-566.

Kuffler, S. W. (1953). Discharge patterns and functional organization of mammalian retina. Journal of Neurophysiology, 16, 37-68.

1.2 Experiment Setup

Figure 1.1

1.3 Instructions

Instructions

In this experiment, you will simulate recording the activity of a single ganglion cell in the retina. You will be asked to project different stimuli on the screen to see what happens to the firing rate of the cell. The screen will look something like this:

The black area on the left is a portion of the wall on which you can project stimuli using your mouse and controls at the bottom of the screen. On the right you will see the firing rate of the cell. As you proceed through the experiment, you will be given different stimuli, such as dots and circle, to use. Follow the instructions in each step.

1.4 Experiment

Begin Experiment

Figure 1.3

1.5 Results

Results

Figure 1.4

1.6 Quiz

Quiz

Question 1.1

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Incorrect.

Correct.

Kuffler found that these receptive fields were shaped like two circles, one inside the other, and called them center-surround receptive fields.

Question 1.2

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Correct.

Incorrect.

The dependent variable is the value the experimenter collects to indicate how you performed in the experiment. In this case, we were looking at how fast the cell fired. So the correct answer is firing rate of the cell.

Question 1.3

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Correct.

Incorrect.

To use the on-center cell as an example, as the dot got bigger, first the firing rate got faster and then after the dot started entering the inhibitory region, it slowed down again. Ultimately, the firing rate was about the same when the dot was as big as the whole cell.

Question 1.4

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Correct.

Incorrect.

The excitatory responses cause the cell to fire faster. This is like turning the cell on, so these receptive fields are called on-center receptive fields.

Question 1.5

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Correct.

Incorrect.

In this experiment you dragged an edge of light across the receptive field. What seems to change the firing rate was where the edge was on the screen. Thus, these cells seem to respond to the position of the edge of the stimulus.