Cerebral Asymmetry (2) Flashcards
Which behaviours did the evolution of the cerebral hemispheres allow for?
Complex behaviour and higher mental functions
What is the posterior cortex largely responsible for?
Somatosensory processing
What is the anterior cortex mostly responsible for?
Motor processing
What are the four lobes of the brain?
Occipital lobe, temporal lobe, parietal lobe, frontal lobe
The differentiation in structure and functioning of the brain between the right and left hemispheres
Cerebral asymmetry
The idea that the two hemispheres have separate functions and for some cognitive functions to be specialized to one side of the brain
Laterality
What is the left hemisphere broadly responsible for?
- Producing and understanding language
- Reading, writing, speech
- Controlling movement on the right side of the body
What is the right hemisphere largely responsible for?
- Perceiving and processing nonverbal information
- Spatial tasks
- Understanding jokes and sarcasm
- Controlling movement on the left side of the body
What are two major environmental and genetic factors that can affect laterality?
- Handedness (left or right)
- Sex assigned at birth
What are the differences in size between the left and right hemispheres?
Left has more grey matter and is smaller and lighter
Right has less grey matter and is larger and heavier
What are the differences in protrusion between the left and right hemispheres?
Left protrudes posteriorly from the parietal/occipital lobes
Right protrudes anteriorly from the frontal lobe
What are the differences between the left and right frontal lobes?
Left:
1. Smaller surface Broca’s area, larger cortex under sulci
2. Larger motor cortex area representing the face
3. Longer Wernicke’s area
4. Smaller primary auditory cortex
5. Larger thalamus
6. Larger secondary auditory processing area
Right:
1. Larger surface Broca’s area, smaller cortex under sulci
2. Smaller motor cortex area representing the face
3. Smaller Wernicke’s area
4. Larger primary auditory cortex
5. Smaller thalamus
6. Smaller secondary auditory processing area
What are the differences between the left and right temporal lobes?
Smaller on left and larger on right
What are the differences between the left and right parietal lobes?
Smaller on left and larger on right
What is the difference between the Sylvian fissure on the left and right hemispheres?
Less steep on the left, more steep on the right
Generally, what might damage to the left hemisphere produce that is unlikely to occur with damage to the right?
Issues with language comprehension, reading and writing
Generally, what might damage to the right hemisphere produce that is unlikely to occur with damage to the left?
Issues with musical ability, musical discrimination, singing
Typically begin in a focal region of one hemisphere and spreads through the fibres of the corpus callosum (the commissure) to the same location in the opposite hemisphere.
Seizure
The surgical disconnection of the two hemispheres by cutting the fibers of the corpus callosum (split-brain)
Commisurotomy
What distinction between left and right brain functioning is important to research on split-brain patients?
Left can access information, initiate speech and communicate information
Right has recognition abilities but cannot initiate speech to communicate information (ex. drawing remains possible)
Experimental technique in which two cortical areas are proven to be dissociated by two different behavioural tests
Double dissociation
Surgeon electrically stimulates the exposed cortex and records the conscious patient’s responses
Electrical Brain stimulation
Uses magnetic fields to either stimulate or inhibit neurons in the brain
Transcranial magnetic stimulation (TMS)
Injecting sodium amobarbital into the left or right carotid arteries to anesthetize the hemisphere on the ipsilateral side
Carotid Sodium Amobarbital Injection
What are the two main differences left-handed people often present in relation to their functional asymmetry?
- No asymmetry
- A reversal of asymmetry
What is the genetic theory of handedness?
A dominant gene for right-handedness and a recessive gene for left-handedness
What are the two main environmental theories of handedness?
- Utility/Evolutionary: It is adaptive for a mother to hold an infant in her left hand to be soothed by the rhythm of her heart, thus leaving her right hand to become dominant to attend to other activities.
- Reinforcement: Our world favours right-handedness in many ways that reinforce it
What is the anatomical theory of handedness?
The left hemisphere shows greater maturation/development in most individuals, supporting a better use of the right hand
What are some general differences in behaviour between sexes?
- Motor: Men are better and throwing/catching, women are better at fine motor control
- Spatial analysis: Men are better at mental rotation and spatial navigation, women are better at identifying movement and landmarks
- Mathematical aptitude: Men are better at mathematical reasoning, women are better at computation
- Perception: Men are better at drawing mechanical objects, women are more sensitive to all forms of sensory stimulation (except vision), facial expressions and body language
- Verbal ability: Women are better at verbal fluency, verbal memory and recalling details of a story
