Hemispheric Lateralisation

Hemispheric lateralisation in psychology refers to the functional differences between the two brain hemispheres. This concept is a key topic in AQA A-level Psychology, particularly in the study of biopsychology.

Definition: Hemispheric lateralisation is the idea that the two brain hemispheres are functionally different, with certain processes and behaviors mainly controlled by one hemisphere.

The document outlines the key features of hemispheric lateralisation:

1. Left hemisphere dominance:

   • Language and speech
   • Words, letters, and language sounds
   • Verbal memory
   • Grammar rules
   • Reading and writing
   • Arithmetic

2. Right hemisphere dominance:

   • Visual-motor tasks
   • Geometric patterns and faces
   • Emotional expression
   • Non-language sounds and music
   • Non-verbal memory
   • Emotional tone of speech
   • Spatial abilities (geometry, sense of direction, distance, mental rotation of shapes)

Highlight: Information received in one hemisphere is sent to the other through bundles of nerve fibers, such as the corpus callosum.

The concept of hemispheric lateralisation was derived from studies on split-brain patients, typically those with epilepsy. In these patients, surgeons cut the corpus callosum to prevent violent activity from crossing between hemispheres.

The document presents several critical evaluations (AO3 points) regarding hemispheric lateralisation:

1. Lateralisation increases neural processing activity:

   Example: Rogers et al. found that in domestic chickens, lateralisation enhanced the ability to perform two tasks simultaneously: finding food and being vigilant for predators.

2. Lateralisation changes with age:

   Quote: "Szaflarki et al found language was more lateralised with increasing age in children but after 25 it decreased with each decade of life."

These points provide valuable insights for students preparing to discuss localisation of function in the brain (16 marks) or answer questions about hemispheric lateralisation in A-level Psychology.

Localisation of Function in the Brain

Localisation of function in psychology refers to the principle that certain functions in the brain have specific locations. This concept is crucial for understanding brain organization and function in AQA A-level Psychology.

Definition: Localisation of function is the principle that certain functions in the brain have specific locations.

Before the advent of brain imaging techniques, much of our knowledge about brain function came from case studies. One famous example is the case of Phineas Gage, a railroad worker in 1848 who survived a severe brain injury.

Example: Phineas Gage's case demonstrated the role of the frontal lobe in personality and behavior. After an accident caused damage to his frontal lobe, his temperament changed significantly.

The document outlines several key areas of the brain and their functions:

1. Visual Centers:

   • Located in both hemispheres, primarily in the occipital lobe
   • Area V1 is responsible for visual perception
   • Damage to V1 results in complete loss of vision

2. Motor Cortex:

   • Generates voluntary motor movements
   • Located in the frontal lobe, specifically the precentral gyrus
   • Present in both hemispheres with logically arranged regions

3. Somatosensory Cortex:

   • Detects sensory events from the body
   • Located in the parietal lobe, specifically the postcentral gyrus
   • Uses mechanoreceptors in the skin to produce localized sensations

4. Auditory Centers:

   • Present in both hemispheres
   • Receives information via two pathways for sound and location
   • Damage to the primary auditory cortex doesn't lead to total deafness

5. Language Areas:

   • Primarily restricted to the left hemisphere in most people
   • Broca's Area (left frontal lobe): responsible for speech production
   • Wernicke's Area (left temporal lobe): involved in language comprehension

Highlight: Damage to Broca's area leads to Broca's aphasia, while damage to Wernicke's area results in Wernicke's aphasia.

The document also presents several critical evaluations (AO3 points) regarding localisation of function in the brain:

1. Support from aphasia studies
2. Individual differences in language areas between genders
3. The concept of equipotentiality, proposed by Lashley, suggesting the brain's capacity to transfer functions from damaged to undamaged areas

Vocabulary: Equipotentiality refers to the brain's ability to transfer functional memory from damaged areas to undamaged areas.