Question

Robert Dougherty and colleagues conducted an experiment to determine the magnification factor in the human visual cortex. Describe the experiment by answering the following questions:

• What research tool was used to get their results?

• Describe the stimuli presented to the subject. What kind of stimulus was used? How were stimuli presented to the subject? Create a diagram if it helps to explain.

• What were the findings?

• What does these findings tell us about visual acuity?

Answer 1

1. Brain imaging technique was used to get their results. It is used to determine the cortical magnification factor. It is a technique that result in images that show which area of the brain are active.

2. The experiment involved stimulus light, which was presented in two areas: near the center and away from the center. When the stimulus light was stimulated near the center, a small region near the fovea was illuminated, and the peripheral retina region was illuminated when the stimulus light was triggered further away from the center.

3. This activity demonstrates the magnification factor because stimulation of the small area near the fovea activated a larger area of the cortex than stimulation of the larger area of the periphery.

4. In the experiment, visual acuity was measured by the use of a psychophysical method. Those with more cortical space also had greater acuity, according to the experiment. Good acuity is correlated not only with the precise focus of the stimuli on the retina and the limited amount of cone convergence but also with the relatively large amount of brain region devoted to the all-cone fovea.