lefthemisphere

The left hemisphere is one of the two cerebral hemispheres, occupying the left side of the cerebrum. It is separated from the right hemisphere by the longitudinal fissure and is connected to it by the corpus callosum. Like the right hemisphere, it houses regions of the frontal, parietal, temporal, and occipital lobes and participates in a wide range of sensory, motor, and cognitive functions. It receives sensory information from and sends motor commands to the right side of the body.

Functional lateralization: In many people, language and related cognitive functions are strongly associated with the left hemisphere. This includes speech production (language-related areas such as Broca’s area) and language comprehension (Wernicke’s area), as well as aspects of reading and writing. Other tasks, such as analytic and sequential processing, are often linked to the left side, though these abilities rely on distributed networks across both hemispheres.

Clinical significance: Damage to the left hemisphere, such as from stroke or injury, can cause language deficits (aphasia), difficulties with writing (agraphia), and weakness or paralysis on the right side of the body. Brain function is adaptable, and other regions can compensate to some extent. In healthy individuals, many tasks engage coordinated activity across both hemispheres.

Individual variation: Lateralization patterns vary among people and across tasks. While language networks are strongly left-lateralized for the majority, some individuals exhibit bilateral or right-dominant language networks, particularly among left-handers. The left hemisphere is a key but not exclusive seat of language and logic within the brain’s broader, interconnected system.