Neuroscience Analysis of Occupational Performance (OCTH 455)
Neuroscience (PTRS 850)
Before you begin this outline, identify each cortical lobe according to name, Brodmann's designation, and function.
Localization of function
Localization of function: A specific function can be attributed to a specific region of the brain (or cortex). Example: prospagnosia is the inability to identify familiar faces; results from damage to the inferior temporal cortex.
Lateralization of function: The two cerebral hemispheres differ in their capabilities to support a specific function. Example: The comprehension and expression of language.
Non-dominant hemisphere (typically the right hemisphere) usually plays a role in spatial relations, emotions (lesion = tonic euphoria), intuitive thought, & prosody (intonations, gestures, affective aspects of language; singing, emotional content of language, sarcasm, interpreting metaphors).
Dominant hemisphere (typically the left hemisphere) usually plays a role in 'intellectual' functions (speech), rational thought, verbal skills, and analytical thinking.
Localization, lateralization, & neuronal plasticity are closely related. Why? What differences related to functional impairment might you expect if the same injury to one hemisphere is sustained by an infant, by a young child (5 - 7 years), or by an adult?
Discuss how stroke survivors, people with epilepsy, commissurectomy patients, and people undergoing sodium amytal testing have contributed to knowledge about hemispheric function.
Cerebral Blood supply
Identify & describe the territory and functions influenced by the:
I've prepared a table for you summarizing clinical profiles of cerebrovascular disorders:
- Middle cerebral artery
- Anterior cerebral artery
- Posterior cerebral artery
- Circle of Willis
- Version #1: as a .pdf format (a higher resolution image, suitable for printing the information for later use. You'll need to use Acrobat Reader to read this .pdf file; you can obtain the Acrobat software for free from Adobe)
- Version #2: as a .jpg format (a bit lower resolution, but your browser should be able to display this version without needing additional software).
Discuss the implications for cortical function and behavior:
There are other factors which play roles in the extent of functional loss after a vascular problem:
- watershed zone: a region of cortex served by branches of the same artery
- border zone: regions of cortex served by branches of different arteries
- end zone: a region served only by a terminal branch of one artery; important in relation to deep brain structures
- vascular anastomoses: joining together of two or more different blood vessels
- coup & contra-coup injuries: What are the essential aspects of the injury?
- tentorium: the tough membrane supporting the occipital lobes, located above the cerebellum
- the presence if anastomoses. At-risk structures may then receive blood through an alternate route
- the size of the blocked vessel. Smaller vessels produce less widespread damage when blocked.
- health of remaining vessels. If surrounding vessels are healthy, new branches from those vessels may form.
- pre-existing vascular lesions. If multiple strokes in the same small area, no new damage occurs & there will be no progressive loss. If multiple sites, diffuse & widespread damage accumulates (stoke-related dementia)
- location of lesion. Some lost functions are easier to live without than others.
- slow vs. rapid onset. Transient ischemic attacks (TIA) produce vascular insufficiency and a slow loss of neurons, while a hemorrhage or ruptured aneurysm causes rapid loss of function & may be fatal
- edema. Swelling of the brain after injury causes increased pressure, which may damage other neurons. Other metabolic factors may also play a role (glutamate release from dying cells may be toxic to nearby cells).
Name the three regions of the cerebral cortex considered as association cortex. Which of Brodmann's areas are part of each association area? Describe the general function for each association area. Describe examples of behaviors produced by a lesion in each region of assoc. cortex. Note that functional loss due to unilateral lesions typically are less severe, while bilateral lesions are often devastating. Why?
Sensory association cortex deficits & behaviors
These five "A- word" deficits often are related to impaired functioning of the sensory association cortex. Define & describe each:
- Alexia (note that alexia is acquired, while dyslexia is congenital; symptoms similar)
Prefrontal association cortex deficits & Praxis
The prefrontal association cortex is surrounded by a number of other cortical regions. Describe the functional responsibilites of any three cortical regions directly adjacent to the territory occupied by prefrontal association cortex.
Three general categories of praxis will be discussed. Give an example of each:
Commissurectomy refers to the surgical interruption of the corpus callosum. Why, in heaven's name, would this surgery be considered!? What have these patients taught us about the corpus callosum and lateralization of function? Which of the three general categories of practic activities would be most severely influenced by this surgery? Why?
- ideation/imagination/conceptualization (prefrontal; areas 10 & 11)
- planning/implementing a strategy (prefrontal & premotor; area 6)
- motor execution (motor; area 4)
Communication & cortical function
Language is a cognitive skill
Aphasia refers to a deficit in language processing
Speech is a motor funtion, as is writing
Dysarthria refers to a motor deficit in speech production, and is strictly a motor problem
Distinguish Broca's Area from Area 45 of the non-dominant hemisphere.
Four major types of aphasia will be discussed in lecture. Identify the lesion sites and describe the characteristics of each type:
Diagram & label major components of the circuit for hearing & speaking
- receptive aphasia
- conductive aphasia
- expressive aphasia
- global aphasia
Diagram & label major components of the circuit for reading out loud
Language is not dependent on sensory modality; gestural systems (sign language) also may be impaired in specific ways (such as the receptive, conduction, or expressive components of language) depending on lesion site
Define the term prosody in relation to lateralization of function, and discuss its potential importance for stroke survivors.
- dyslexia (congenital)
- alexia (acquired)
- alexia with agraphia (sensory integration impairment)
Other disorders relating to impaired cortical function
While we are on the topic of related disorders, keep in mind that pre-existing pathology is an important consideration in assessing function after an injury, and in predicting the potential for future injuries.
- Learning disabilities: possible causitive factors include structural damage (particularly to sensory association cortex, see "A-word" deficits above), physiological dysfunction, abnormal cerebral lateralization, maturational lag, and environmental deprivation.
- Epilepsy: Identify 2 stereotypic symptoms of a seizure, and any 3 factors which commonly may trigger a seizure. Discuss potential influence of seizure medications on O.T. therapy.
- Mental health: Altered neurotransmitter action; diffuse brain damage
- Infections of the CNS: Viral (including AIDS-related encephalopathy), bacterial (meningitis), fungal, parasitic.
- Dementia: Recognize that memory problems & cognitive problems are associated with normal aging. Discuss similarities & difference in approach to dementia related to Alzheimer's disease, Parkinson's and other diseases, stroke, etc. Discuss issues related to the individual & to family/support systems.
We will discuss different means by which the brain can be imaged and brain function evaluated, with attention to the relative advantages and disadvantages of each approach.
End of the Cortex lectures outline
RETURN to the OCTH 455 lecture outlines menu.
Comments? Send e-mail to Jeff Radel
Last Update: April 2002