Question 5 (40 points total) As we discussed in class, the origin of the choice probability effect observed in area MT by Britten et al.

Question 5 (40 points total) 

As we discussed in class, the origin of the choice probability effect observed in area MT by Britten et al. (1996) remains unclear, and there are multiple possible ways to explain this observation. Consider the following questions regarding the possible origins of choice probability: 

a) In a sentence or two, provide a concise but clear description of what it means for a neuron to show a significant choice probability. What can you infer about the functional contribution of MT neurons to behavior based on choice probabilities? (5 points) 

b) Briefly describe the "bottom-up" and "top-down" explanations for choice probabilities. For each possible explanation, describe how choice probabilities are thought to arise. (10 points) 

c) To help understand the origins of choice probability, you decide to perform experiments in a simpler species. The motion perception system in this species has the following distinctive and convenient features: i) all of the direction-selective neurons in the brain are located in one well-defined area of sensory cortex; ii) these sensory neurons project to a single area of the brain in which decisions about motion are made; iii) feed-forward connections from the sensory area to the decision area and feed-back connections from the decision area to the sensory area are segregated into separate bundles of axons. You are able to train this species to perform the direction discrimination task of Britten et al (1996), and you observe that single neurons in the sensory area exhibit significant choice probabilities. Design an experiment that can determine whether choice probabilities in this species arise through a bottom-up or top-down mechanism. Explain how and why your proposed manipulation can dissociate the two possible explanations. (25 points)