Answer:
The correct answer is - optogenetics.
Explanation:
Optogenetics is a technique that is used in examining the basis of smell, fear, and memory that involves the use of light to regulate cells in a biological tissue especially neurons, which are genetically altered to show light ion channels.
Channelrhodopsin-2 is the most commonly used ion channel for triggering the optogenetics. When a definite number of positive ions have to get through the cell membrane, it causes the neuron to fire reaching the threshold.
Thus, the correct answer is - optogenetics.