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MLA 8
David H. Hubel and Torsten Nils Wiesel won the 1981 Nobel prize in Physiology and Medicine for their discovery of feature detecting neurons in the brain. They were the first people to discover the visual features that neurons respond to.
For this assignment, you will watch two *original* videos of their work and write a reaction post on the Discussion Board.
Background on Hubel and Wiesel
In order to understand the videos, you must have a good idea of the experimental set-up. Hubel and Wiesel inserted an electrode into the occipital lobe of a cat’s brain. The electrode measures when a single neuron “fires” – in other words, when the neuron’s voltage changes because an action potential has occurred. A basic diagram of the set-up appears below. After the cat was anesthetized and an electrode was inserted into the brain, the cat was placed in front of a screen. Hubel and Wiesel used handheld flashlights and slides in a projector to produce spots or lines of light or dark on a screen. They could change the size of the spots, the length and orientation

of the lines, and they could move the flashlight around so that the stimulus could appear anywhere on the screen. Eventually, a stimulus would excite the neuron they were recording from, causing the neuron to fire.
Hubel and Weisel had two ways to detect when a neuron fired. The first way was to connect the output of the electrode to a device called an oscilloscope. The oscilloscope plots voltage changes over time on a screen. The picture below shows the screen of an oscilloscope and one action potential. Remember, an action potential is a rapid change in voltage, from – 70 millivolts to around +30 millivolts. The vertical “spike” in the picture above is exactly that change in voltage. There are many figures in your book that also show these spikes.
The second way that Hubel and Weisel could detect when a neuron fired was to connect the output of the electrode to a speaker. When an action potential occurs, this causes a short “pop” sound in the speaker. The more the speaker “pops”, the more a neuron is firing.
Watch the following videos:
First video: