sensations

Sensation is the process by which sensory receptors respond to external or internal stimuli and convert them into neural signals that the brain can interpret. It refers to the initial detection of a stimulus, not the interpretation or meaning assigned to it, which is the domain of perception. Common sensory modalities include vision, hearing, touch, taste, smell, as well as proprioception, vestibular sense, and thermoception.

Sensory receptors transduce energy into electrical signals. Receptor cells respond to specific forms of energy—light, sound waves, chemical molecules, or mechanical pressure. The signals travel through dedicated neural pathways: visual information via the optic nerves to the visual cortex, auditory information via the auditory nerves to the auditory cortex, somatosensory input via touch pathways to the somatosensory cortex, and so on. The thalamus serves as a relay station for many modalities before the signals reach their primary sensory cortices. Cortical processing extracts features such as intensity, depth, orientation, and texture, while adaptation reduces responsiveness to sustained stimuli.

Sensation is a topic of psychophysics, which examines thresholds and limits of detection. Absolute thresholds denote the minimum stimulus intensity detectable, while difference thresholds (just noticeable differences) indicate the smallest noticeable change in a stimulus. Perception involves higher-order interpretation, context, attention, and prior knowledge, shaping how sensations are experienced. Sensory information is often integrated across modalities, as multisensory processing combines input from different senses to form a cohesive experience. Variations include sensory impairments, attention-related modulation of sensation, and phenomena such as synesthesia, where stimulation in one sense involuntarily evokes experiences in another.