Science
Fact-checked

At AllTheScience, we're committed to delivering accurate, trustworthy information. Our expert-authored content is rigorously fact-checked and sourced from credible authorities. Discover how we uphold the highest standards in providing you with reliable knowledge.

Learn more...

In Neuroscience, What Is an Absolute Threshold?

In neuroscience, an absolute threshold is the smallest intensity of a stimulus that one can detect half the time. It's a critical concept, marking the boundary between imperceptible and noticeable. Understanding this threshold helps unravel the mysteries of human perception. How does this threshold vary among individuals, and what factors influence it? Join us as we uncover the intricacies of sensory experience.
Michael Smathers
Michael Smathers

The nervous systems of humans process sensory information by interpreting external and internal stimuli and transferring the information to the brain for processing. Neurons in the brain receive electrochemical impulses. Like any type of sensory instrument, the various afferent, or receptor, neurons have a minimum stimulus that they can actually detect. This stimulus, called the absolute threshold, varies between people and can be affected by external conditions. When individuals are tested, they may or may not experience the stimulus; therefore, the absolute threshold is defined as the lowest detectable level of a stimulus 50% of the time.

Vision relies on two types of cells, rods and cones, which have different functions. Cones detect color; rods detect shapes and are best suited for seeing in darkness. The absolute threshold for vision, or the minimum number of photons that the eye can detect, is generally accepted as 90 photons, only nine of which reach the retina and fovea, the most sensitive part of the eye. This measurement assumes optimal conditions; i.e., eyes completely adjusted to darkness and a wavelength to which the rod cells are most sensitive.

The body's threshold can be trained, such as when wine tasters learn to distinguish between nearly identical flavors of wine.
The body's threshold can be trained, such as when wine tasters learn to distinguish between nearly identical flavors of wine.

Hearing works by transmitting electrochemical impulses through the auditory nerve when air vibrations transfer from the eardrum to the cilia in the inner ear. The minimum atmospheric pressure to induce audible sound when the source is adjacent to the ear is 20 micropascals, assuming no hearing damage. The ear is intended to hear sounds within the range of 20 to 20,000 hertz, but is most sensitive when exposed to frequencies between 1,000 and 5,000 hertz.

Damage to the auditory nerve may lead to increased sensitivity to sounds in some people.
Damage to the auditory nerve may lead to increased sensitivity to sounds in some people.

Several factors can influence a person's reported absolute threshold: expectation or anticipation of the stimulus, repeated exposure, damage to the sensory organs, and mental or emotional state. If a person is expecting to receive a particular stimulus, he or she will be naturally more attuned to it. Repeated exposure, on the other hand, will cause the sensory nervous system to filter out that type of input. Sensory organ damage increases the absolute threshold, and high stress levels will cause the body to secrete adrenaline, which makes the sensory organs more attuned to incoming stimuli and likely to respond.

Neurons have a minimum amount of stimulus that receptors can actually detect, called the absolute threshold.
Neurons have a minimum amount of stimulus that receptors can actually detect, called the absolute threshold.

Absolute threshold is distinguished from difference threshold. This measurement refers to the minimum difference between two or more stimuli required for the brain to detect any difference. The body's difference threshold can be trained; for example, wine tasters learn to distinguish between nearly identical flavors of wine.

You might also Like

Discuss this Article

Post your comments
Login:
Forgot password?
Register:
    • The body's threshold can be trained, such as when wine tasters learn to distinguish between nearly identical flavors of wine.
      By: Wrangler
      The body's threshold can be trained, such as when wine tasters learn to distinguish between nearly identical flavors of wine.
    • Damage to the auditory nerve may lead to increased sensitivity to sounds in some people.
      By: Tatyana Gladskih
      Damage to the auditory nerve may lead to increased sensitivity to sounds in some people.
    • Neurons have a minimum amount of stimulus that receptors can actually detect, called the absolute threshold.
      By: designua
      Neurons have a minimum amount of stimulus that receptors can actually detect, called the absolute threshold.
    • Damage to nerves, sensory neurons or the brain may make it more difficult for people to perceive extreme temperatures, which may lead to injury.
      By: DURIS Guillaume
      Damage to nerves, sensory neurons or the brain may make it more difficult for people to perceive extreme temperatures, which may lead to injury.