A system for detecting an inhibitory circuit of a brain, the system comprising: a detection device that detects a brain activity; a trigger output device that outputs a first trigger that is a stimulus or a task for a living body, and a second trigger that can change a first brain activity induced by an output of the first trigger; means for acquiring first brain activity information on the first brain activity; means for acquiring second brain activity information on a second brain activity induced by the application of the first trigger which is accompanied by the application of the second trigger; means for detecting a change in the first brain activity induced by the output of the second trigger on the basis of the first brain activity information and the second brain activity information; means for selecting a type of the inhibitory circuit to be inputted to an excitatory circuit which is to be activated by the first trigger, wherein the inhibitory circuit is selected according to a timing of the application of the second trigger in advance of the application of the first trigger to evaluate the response as an indicator of an action of the inhibitory circuit; characterised in that: the detection device detects a brain activity by way of detecting electrical activity of the brain or by way of detecting a change in cerebral blood flow; and for the first trigger, the stimulus is selected from the group comprising a touch, a change of temperature, a pain, deep sensibility, a visual stimulus, a sound, a taste, and a smell, and the task comprises utilizing language, thoughts, memories, emotions, recognition, learning, motivation, or exercise. a detection device that detects a brain activity; a trigger output device that outputs a first trigger that is a stimulus or a task for a living body, and a second trigger that can change a first brain activity induced by an output of the first trigger; means for acquiring first brain activity information on the first brain activity; means for acquiring second brain activity information on a second brain activity induced by the application of the first trigger which is accompanied by the application of the second trigger; means for detecting a change in the first brain activity induced by the output of the second trigger on the basis of the first brain activity information and the second brain activity information; means for selecting a type of the inhibitory circuit to be inputted to an excitatory circuit which is to be activated by the first trigger, wherein the inhibitory circuit is selected according to a timing of the application of the second trigger in advance of the application of the first trigger to evaluate the response as an indicator of an action of the inhibitory circuit; characterised in that: the detection device detects a brain activity by way of detecting electrical activity of the brain or by way of detecting a change in cerebral blood flow; and for the first trigger, the stimulus is selected from the group comprising a touch, a change of temperature, a pain, deep sensibility, a visual stimulus, a sound, a taste, and a smell, and the task comprises utilizing language, thoughts, memories, emotions, recognition, learning, motivation, or exercise. the detection device detects a brain activity by way of detecting electrical activity of the brain or by way of detecting a change in cerebral blood flow; and for the first trigger, the stimulus is selected from the group comprising a touch, a change of temperature, a pain, deep sensibility, a visual stimulus, a sound, a taste, and a smell, and the task comprises utilizing language, thoughts, memories, emotions, recognition, learning, motivation, or exercise.