Brent Cornell

    
The cerebrum is organised into two hemispheres that are responsible for higher order functions and complex skills

• These functions include memory, speech, cognitive thought, problem solving, attention and emotions

Not all complex tasks are equally represented by both cerebral hemispheres – some activities are localised to a single side

• Speech production is coordinated by Broca’s area, which is situated in the left frontal lobe of the brain

Information can be passed between the two hemispheres by a bundle of myelinated nerve fibres embedded within the brain

• These fibres form the corpus callosum to facilitate interhemispheric communication

Lateralization of Brain Function

    
The left cerebral hemisphere is responsible for processing sensory information from the right side of the body (and vice versa)

• Tactile sensation from the left side of the body is processed by the right side of the brain (at the somatosensory cortex)
• Objects on the left side of the visual field in both eyes are processed on the right side of the visual cortex

The processing of information on the opposite side of the body is called contralateral processing (same side = ipsilateral)

• Tactile information from the left side of the body is transferred to the right side in the spinal cord or brainstem
• Visual information from the left visual field is transferred to the right cerebral hemisphere at the optic chiasma

    
The left cerebral hemisphere is also responsible for processing motor information for the right side of the body (and vice versa)

• Muscular contractions are coordinated by the motor cortex (premotor cortex = preparation ; primary motor cortex = execution)

A consequence of this contralateral processing is that damage to one side of the brain affects the other side of the body

• For instance, a stroke in the left hemisphere may cause paralysis to the right side of the body

Contralateral Processing