sensory processing

Meaning: Sensory processing is the sequence by which the nervous system detects a stimulus and converts it into a neural signal the brain can use. Receptors respond to a stimulus, transduction turns that energy into electrical signals, and sensory neurons carry them to the brain. For most senses the signal passes through the thalamus on the way to a primary sensory cortex; smell is the classic exception. Higher areas then combine the input with memory and expectation to produce perception.

On the MCAT: Passages contrast bottom-up processing, driven by stimulus features and building from receptors to recognition, with top-down processing, driven by knowledge, context and expectation, as when you read a misspelled word correctly. Expect a short scenario and a question asking which type applies. Related ideas include sensory adaptation, thresholds, signal detection theory and feature detection.

Common confusion: Sensation is not perception. Sensation is receptor detection and transduction of stimulus energy; perception is the brain's interpretation of it. Top-down processing still uses sensory input, but expectation shapes how that input is read.