pysch 9/22

Sensation

• Definition: The process by which our sensory organs detect stimuli from the environment.
• Psychological Disorders: Many psychological disorders are linked to issues with sensation, attention, and perception.

Absolute Threshold

• Definition: The minimum intensity of a stimulus that a person can detect $50\%$ of the time. It is the point at which a stimulus goes from being undetectable to detectable.
• Example: Turning up the volume slowly from $0$ to $1$. The second it becomes audible, it has crossed your absolute threshold. This applies to seeing something, feeling something, or any other sensory detection.

Difference Threshold (Just Noticeable Difference - JND)

• Definition: The smallest detectable difference between two stimuli, or the minimum change in a stimulus that can be detected.
• Example: If the volume is at setting $20$ and you can tell the difference when it is turned down, that change has crossed your difference threshold.
• Weber's Law (Implicit): It is easier to detect a difference between stimuli when their initial intensity is low (e.g., between $5$ and $10$). It becomes harder to detect a difference when the overall stimulus intensity is high (e.g., between a very loud sound or a very bright light), indicating that the just noticeable difference is a constant proportion of the original stimulus's intensity.

Gate Control Theory of Pain

• Core Principle: The transmission of pain signals from the periphery to the brain can be modulated (either increased or decreased) at the spinal cord level by both non-painful inputs and descending signals from the brain.
• Pain Receptors (Nociceptors):
  • Specialized nerve endings of first-order neurons in the pain pathway.
  • Axons: Form small-diameter nerve fibers of two types:
    • Fast A-delta fibers: Responsible for the initial, sharp, localized pain perceived immediately at the time of injury.
    • Slow C fibers: Responsible for a dull, longer-lasting, aching, or throbbing pain.
• Pain Pathway (Simplified):
  1. First-order neurons: Transmit signals from nociceptors via spinal nerves to the spinal cord.
  2. Synapse: In the spinal cord (specifically, the dorsal horn), first-order neurons synapse with second-order neurons.
  3. Third-order neurons: Along with second-order neurons, carry pain signals further up to the brain for processing and perception.
• The Nerve Gate: According to the theory, pain perception is not solely due to nociceptor stimulation. A