Brain
Occipital Lobe
The brain's visual processing center
Overview
The occipital lobe, located at the back of the brain, is dedicated primarily to visual processing. The primary visual cortex (V1) receives raw signals from the retinas and begins the process of interpreting shape, color, movement, and depth. Higher visual areas (V2-V5) handle increasingly complex aspects of vision.
Function
- Receives and processes raw visual signals from the eyes
- Identifies shapes, colors, and motion
- Processes depth and spatial relationships
- Feeds into the ventral stream (object recognition) and dorsal stream (spatial action)
- Integrates visual information with other senses
Key Facts
- The primary visual cortex has a map of the visual field (retinotopy)
- Each hemisphere processes the opposite visual field
- Damage can cause cortical blindness even with healthy eyes
- Visual illusions originate largely in occipital processing differences
Key Substructures
- V1 (primary visual cortex, striate cortex): edge detection, orientation, and spatial frequency
- V2: complex pattern integration; routes signals to ventral and dorsal streams
- V4: color processing and fine shape recognition
- V5/MT (middle temporal area): motion detection and optic flow
- Dorsal stream (“where/how”): spatial navigation and action; Ventral stream (“what”): object identity
Clinical Notes
- V1 damage causes cortical blindness: no visual perception even with healthy eyes
- V4 lesion causes achromatopsia: complete inability to perceive color
- V5/MT damage causes akinetopsia: inability to perceive visual motion
- Anton syndrome: patient is cortically blind but confabulates and denies blindness