Hemispheric Lateralisation and Language Centres
Hemispheric lateralisation refers to the specialization of brain functions in different hemispheres. This concept is crucial in understanding stroke cases like Robert's, where specific deficits can indicate the location of brain damage.
Definition: Hemispheric lateralisation is the distribution of cognitive functions between the left and right brain hemispheres.
Robert's case exemplifies how left hemisphere language functions are affected by stroke:
- Speech production impairment Broca′saphasia suggests damage to Broca's area in the left hemisphere.
- Preserved language comprehension indicates an intact Wernicke's area.
- Right-side paralysis further confirms left hemisphere damage.
Highlight: The ability to assess hemisphere-specific functions helps in localizing brain damage and planning effective treatments for stroke patients.
Split-brain research by Sperry provides strong evidence for hemispheric lateralisation:
- Patients with severed corpus callosum showed hemisphere-specific responses to visual stimuli.
- Left hemisphere dominance for speech production was demonstrated.
Example: If Robert were a split-brain patient, he might be unable to verbalize images presented to his right visual field due to left hemisphere damage.
However, Sperry's research has limitations:
- Generalizability issues due to the use of epilepsy patients only.
- Potential medication effects on performance.
Vocabulary: Internal validity refers to the extent to which a study accurately measures what it intends to measure.
Despite these limitations, the study's high internal validity strengthens its findings on hemispheric lateralisation.