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How does the brain determine the intensity of a stimulus?
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Senses
Vespid wasps (Vespidae), similar to other insects, have compound eyes that consist of thousands of tiny optical units known as ommatidia, which contain light-sensitive photoreceptor cells.
The brain determines the intensity of a stimulus through two primary mechanisms involving the activity of sensory receptors and afferent nerve fibers:
- Frequency of discharge: As the strength of a stimulus increases, the rate of change in the electrical potential of the receptor rises, which in turn increases the frequency of nerve impulse discharge from the neuron.1
- Recruitment of fibers: The brain also gauges intensity based on the total number of afferent nerves reporting the stimulation.1
Essentially, as a stimulus becomes more intense, the nervous system receives a higher volume of signals both in terms of how often individual neurons fire and how many distinct nerve fibers are activated simultaneously. These signals are transmitted to the central nervous system as action potentials, allowing the brain to interpret the magnitude of the input from the external or internal environment.12