Split-Brain research into hemispheric lateralisation

Question 1

Hemispheric Lateralisation

Answer 1

• Hemispheric Lateralisation: The concept that each hemisphere of the brain is specialised for specific functions.
  o Left Hemisphere: Primarily involved in language, logic, and analytical tasks.
  o Right Hemisphere: More involved in visual-spatial tasks, creativity, and holistic processing.
• Key Concept: Although both hemispheres communicate via the corpus callosum, each has distinct roles.

Question 2

Split-Brain Surgery

Answer 2

• Definition: A surgical procedure, also known as corpus callosotomy, where the corpus callosum is severed to treat severe epilepsy.
• Purpose: This prevents the spread of epileptic seizures between the two hemispheres, reducing their severity.
• Key Concept: In split-brain patients, the two hemispheres cannot communicate, allowing researchers to study each hemisphere’s independent functions.

Question 3

Sperry’s Split-Brain Research

Answer 3

• Roger Sperry (1968): Pioneered split-brain research to understand the lateralisation of brain function.
  o Participants: Individuals who had undergone corpus callosotomy to treat epilepsy.
  o Method: Sperry used tasks where information was presented to either the left or right visual field, thus being processed by only one hemisphere.

Question 4

Findings from Sperry’s Research

Answer 4

1. Language and the Left Hemisphere:
   o When objects were presented to the right visual field (processed by the left hemisphere), participants could name the object, demonstrating the left hemisphere’s role in language production.
2. Visual-Spatial Tasks and the Right Hemisphere:
   o When objects were presented to the left visual field (processed by the right hemisphere), participants could not name the object, but could draw or point to it, showing the right hemisphere’s role in visual-spatial processing.
3. Dual Awareness:
   o When a different object was presented to each visual field, participants could draw with their left hand (controlled by the right hemisphere) what they saw in the left visual field but could only describe what was presented in the right visual field (controlled by the left hemisphere).

Question 5

Split-Brain Research Tasks

Answer 5

1. Tactile Tasks:
   o Objects placed in the left hand (controlled by the right hemisphere) could not be verbally identified but could be recognised by touch or selected from a group of items.
   o Objects in the right hand (controlled by the left hemisphere) could be verbally identified.
2. Visual Tasks:
   o Information shown in the right visual field (processed by the left hemisphere) could be described verbally.
   o Information shown in the left visual field (processed by the right hemisphere) could not be described verbally but could be drawn or pointed to.

Question 6

Conclusions from Split-Brain Research

Answer 6

• Lateralisation of Function:
  o Left Hemisphere: Dominant in language processing, speech production, and analytical tasks.
  o Right Hemisphere: Specialised in spatial tasks, recognising faces, and processing non-verbal information.
• Independent Functioning: The two hemispheres can operate independently in split-brain patients, each processing information without sharing it with the other side.

Question 7

Evaluation of Sperry’s Research

Answer 7

• Strengths:
  1. Empirical Support: Sperry’s findings provide strong evidence for hemispheric lateralisation and the distinct functions of each hemisphere.
  2. Controlled Methodology: Sperry’s use of well-controlled experiments allowed precise measurement of each hemisphere’s capabilities.
  3. Practical Applications: Understanding lateralisation can help develop treatments for neurological conditions such as epilepsy.
• Limitations:
  1. Generalisability: Split-brain patients represent a very specific population with severe epilepsy; therefore, findings may not be generalisable to the wider population.
  2. Artificial Tasks: The experimental tasks used in Sperry’s research are highly artificial and may not reflect everyday situations.
  3. Oversimplification: Some evidence suggests that the hemispheres are not as functionally distinct as Sperry’s research suggests. For example, both hemispheres are involved in many complex tasks like language and spatial awareness.

Question 8

Supporting Research for Lateralisation

Answer 8

• Gazzaniga (1983): Further research into split-brain patients showed that while language is mostly lateralised to the left hemisphere, both hemispheres are capable of understanding language to some degree.
• Brain Imaging Studies: Modern brain imaging techniques like fMRI show hemispheric lateralisation in real-time, supporting Sperry’s findings but also showing some overlap in functions between the hemispheres.

Question 9

Plasticity and Lateralisation

Answer 9

• Plasticity in Lateralisation: While hemispheric lateralisation suggests specialised functions, the brain is also capable of significant plasticity. For example, in some cases of brain injury, the non-dominant hemisphere can take over some language or spatial tasks, showing that lateralisation is not absolute.

Question 10

Key Exam Points for Split-Brain Research and Lateralisation

Answer 10

• Key Terms: Be able to define hemispheric lateralisation, corpus callosum, and split-brain research.
• Sperry’s Findings: Understand how Sperry’s split-brain studies provide evidence for lateralisation and the independent functioning of the hemispheres.
• Evaluation: Be ready to discuss the strengths and limitations of Sperry’s research, including generalisability and the artificiality of tasks.
• Application: Discuss how split-brain research has contributed to our understanding of brain lateralisation and has practical applications in treating conditions like epilepsy.