2 Neuroscience2.7 Neural circuits
2.7.1.11 Perception
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Written by Resident Doctor Committee · Published
Sensation and perception
Sensation converts physical signals into neural activity, and perception interprets them.
Signals pass from primary cortex to association cortex, and feedback lets expectation shape early sensory responses.
Visual streams
Stream | Handles | Damage |
|---|---|---|
Ventral, the "what" pathway (occipital to inferior temporal) | Object and face recognition | Recognition fails; reaching may survive |
Dorsal, the "where and how" pathway (occipital to posterior parietal) | Space, motion, visually guided action | Reaching fails; naming may survive |
Interoception
Interoception is perception of the body's internal physiological state, such as heartbeat, breathing, gut sensation and visceral arousal.
Proprioception and kinaesthesia are different senses, because they concern body position and movement.
The posterior insula processes bodily signals, and anterior regions integrate salience and expectation.
Disorders of perception
Disorder | Definition | Note |
|---|---|---|
Illusion | Misinterpretation of a stimulus that is present | Common in healthy people, especially with fatigue, anxiety or delirium |
Hallucination | Perceptual experience with no matching stimulus | Also occurs with sensory loss, sleep transitions and substances |
Agnosia | Recognition failure despite adequate basic sensation | Prosopagnosia affects faces |
Visual hallucinations are best explained by dysfunction across a distributed network of visual and attentional regions, not by any single localised structure.
Sensory loss, cortical processing and arousal can each contribute, as in eye disease, Lewy body disease and delirium.
Proposed mechanisms in psychosis include overweighted expectation, unreliable sensory evidence, source monitoring errors and aberrant salience.