1 Psychology and human development1.1 Sensation and perception
1.1.4 Visual pathways and perceptual binding
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Written by Resident Doctor Committee · Published
New in the 2027 syllabus
The College added this topic for exams from January 2027.
From retina to cortex
The axons of retinal ganglion cells form the optic nerves. At the optic chiasm, fibres from the nasal (inner) half of each retina cross over. So each visual hemifield (half of the visual field) is processed by the opposite cerebral hemisphere.
The geniculostriate pathway runs through the lateral geniculate nucleus and the optic radiations to the primary visual cortex in the occipital lobe.
Visual information then travels onwards through parallel cortical systems that interact. It does not follow a single serial chain.
Stream | Main course | Functions |
|---|---|---|
Ventral | Occipital to temporal cortex | Identifying objects and recognising what is seen |
Dorsal | Occipital to parietal cortex | Where things are in space and guiding action by sight |
Combining features
The binding problem asks how colour, shape, position and movement, which are processed separately, come to be experienced as properties of the same object.
Feature integration theory proposes that focused attention binds features that share a location. When attention is divided, features may be detected correctly but joined up wrongly. These are illusory combinations.
Unconscious inference, associated with Helmholtz, uses past experience to pick the most likely explanation for ambiguous sensory input. It happens without deliberate reasoning.
Illusions can expose these assumptions. An expectation about depth or lighting is usually useful, but sometimes it leads to a mistaken judgement.
Developing vision
Intrinsic factors are the developing receptors, pathways and cortical organisation. They limit what visual information can be processed.
Extrinsic factors are patterned visual input and chances to coordinate seeing with action during sensitive periods.
Interaction means that neither maturation alone nor exposure alone explains visual development. Abnormal visual input early in life can change how the developing cortex responds.