Hemispheric Lateralisation

• Hemispheric lateralisation - idea that the 2 halves of the brain are functionally different and that each hemisphere has functional specialisations
• Speech and language are lateralised to the left hemisphere
• Broca - neurosurgeon who had a patient that couldn't say anything other than the word ' tan ' but could still comprehend speech with no issues; he performed post-mortems on patients with speech deficits after death
• Broca's area - in the posterior (back) of the left frontal lobe; helps coordinate speech production; may lead to Broca's aphasia if damaged
• Wernicke's area - in the posterior (back) of the left temporal lobe; helps in the comprehension of speech; damage to the area may lead to Wernicke's aphasia
• Broca's aphasia - able to comprehend speech but have difficulty with speech production
• Wernicke's aphasia - able to speak but unable to understand language
• Global aphasia - both Broca's and Wernicke's areas damaged meaning the patient can't understand or produce speech
• Split brain research - The corpus collosum between the 2 hemispheres of the brain is cut in response to severe epileptic seizures
• Roger Sperry (1967) - Test verbal responses to language : Words projected to the left visual field and received by the right hemisphere; words did not seem to be registered and participants say they didn't see anything; left hemisphere is responsible for language
• Roger Sperry (1967) - Test physical responses to language : objects placed in the left hand and received by the right hemisphere; patient couldn't describe what they felt
• Roger Sperry (1967) - Test matching abilities in response to pictures : picture presented to the right visual field so processed by the left the hemisphere; the right hand would attempt to draw a picture but not as clear as the left hand
• Karen Byrne - case study of alien hand syndrome; one hemisphere refuses to be dominated and overrun by the other