Flashcards in Week Five - Lateralisation & Language Deck (38)
What does contralateral control mean?
The left side of the brain controls the right side of the body and vice versa.
How do the brain hemispheres communicate?
Through a large band of fibres known as the corpus callosum
Is there a dominant hemisphere?
Yes. Right handed people are left side dominant. However, not always the case.
Is there a sense that isn't contralaterally controlled?
Yes, sense of smell (olfaction)
What anatomical directions refer to the top, bottom, front and back of the brain?
Top = Dorsal
Bottom = Ventral
Front = Rostral
Back = Caudal
What do asymmetries in the brain allow insight into?
Potential differences in function
What do we see in regards to the LH and RH in asymmetries of the brain?
LH: Enlargement of Wernicke's area and parts of the Thalamus. Neurons tend to have longer dendrites that RH neurons.
RH: Enlargement of the anterior portion
What parts of the corpus callosum connect the front of the brain and the back of the brain?
Genu = front (prefrontal cortex)
Splenium = back (parietal, occipital and temporal)
What are ipsilateral connections?
Connections that stay within the same hemisphere - do not cross the corpus callosum.
What are Homotopic connections?
Connections/structures that cross over the corpus callosum to the same region in the opposite hemisphere
What are Heterotopic connections?
Connections/structures that cross over the corpus callosum to a different region of the opposite hemisphere
What is the main consensus on the study regarding synchrony across the corpus callosum?
The synchrony between neurons firing is facilitated by the connection across the corpus callosum. Those with severed CC are non synchronised.
What are the 4 other commissures (not including CC)
Anterior: Plays a role in - olfactory pathway, pain sensation and connects temporal regions.
Habenular: Plays a role in - pineal gland, epithalamus (hormonal)
Posterior: Plays a role in - pupillary light reflexes, pineal gland, and epithalamus
Hippocampal: Connects the two halves of the hippocampus through the fornix
Explain the basis of the Myers and Sperry experiment on cats?
They wanted to restrict visual information to 1 hemisphere - by cutting CC or optic chiasm and then blindfolding one eye.
Cats with only one section cut (or none) learnt the task as normal and retained the task perfectly when the blindfolded eye switched.
Cats with both sections cut also learnt the task as normal but they showed no retention when switching the blindfolded eye (basically had to learn the whole task again)
What was the conclusion of the Myers study?
The cat forebrain has the capacity to act as two separate forebrains, each capable of independent learning and of storing its own memories
Cutting the corpus callosum in humans outcomes?
Remarkably effective in controlling seizures (however, there were side effects)
What can still be transferred if we SPARE the genu of the CC?
Transfer of higher order semantic information is spared.
If we SPARE the splenium what is not disrupted (what is disrupted though)?
Visual identification is NOT disrupted but: Tactile is
What occurs if the posterior portion of the CC (including splenium) is damaged?
Disruption of transfer of visual, tactile and auditory information
Explain the process of split-brain patients
Right visual input (i.e., word) goes to left hemisphere and able to say it, could pick it with right hand (but not left)
Left visual input goes to right hemisphere and unable to say it but able to recognise if given the prop, object etc with left hand (but not right hand)
What are the face recognition disparities between the hemispheres?
LH = better at recognising self
RH = better at recognising familiar others
What is the RH specialised for?
Many aspects of visuospatial processing:
- mental rotation, spatial matching, mirror image task
- better able to draw/copy a 3D figure
- superior block design performance
How do we tests language lateralisation? Define them.
Sodium Amytal Test (Wada Test) - The anaesthetisation of the ipsilateral hemisphere to allow the abilities of the contralateral hemisphere to be assessed. When injection is on the dominant speech hemisphere (left), patient is totally mute (for a short time). Done prior to surgery so that surgeon takes care not to damage the area where speech originates from.
Dichotic Listening Task - Each ear is presented with different words/phrases/numbers. The side that performs the best is dominant.
Brain Imaging - Assessing where brain lights up during language tasks
What types of language does the RH have a role in?
Anything to do with visualisation eg. rhythm, metaphors
Which area is responsible for language production?
Which area is responsible for language comprehension?
Mostly LH lateralized areas surround what?
The Sylvian fissure
What is Anomia?
Difficulty finding words
What is Dysarthria?
Difficulty controlling muscles used in speech