Lateralization of Language
Language lateralization refers to the tendency for language functions to be served more by one cerebral hemisphere, typically the left, than the other.
Definition
The differential involvement of the cerebral hemispheres in language, including the predominance of one hemisphere for core linguistic functions.
Scope
This topic covers the evidence for left-hemisphere dominance from lesion, split-brain, and imaging studies, the relationship of dominance to handedness, the right hemisphere's contributions to prosody and discourse, and how lateralization varies across individuals. It describes the phenomenon and its evidence base.
Core questions
- Why and how is language predominantly served by the left hemisphere?
- How does language dominance relate to handedness?
- What does the right hemisphere contribute to language?
Key concepts
- left-hemisphere dominance
- handedness
- split-brain studies
- right-hemisphere language
- interhemispheric communication
Key theories
- Left-hemisphere dominance
- The long-standing observation, integrated by Geschwind, that core language functions are typically left-lateralized, supported by lesion and split-brain evidence.
- Graded dominance and handedness
- Knecht and colleagues' demonstration that left-hemisphere language dominance is the norm but its likelihood varies systematically with handedness across healthy individuals.
History
From nineteenth-century lesion work establishing left dominance, through Sperry and Gazzaniga's split-brain studies, to imaging studies such as Knecht and colleagues' 2000 work relating dominance to handedness, lateralization has been a central theme of the neuroscience of language.
Debates
- Degree and origins of lateralization
- How strongly language is lateralized, how this relates to handedness and individual variation, and what the right hemisphere genuinely contributes.
Key figures
- Norman Geschwind
- Michael Gazzaniga
- Stefan Knecht
Related topics
Seminal works
- geschwind1970
- knecht2000
- gazzaniga2000
Frequently asked questions
- Is language always in the left hemisphere?
- Left-hemisphere dominance for core language is typical, especially in right-handers, but a minority of people, more often left-handers, show right-hemisphere or bilateral dominance.