Neuroscience Analysis of Occupational Performance (OCTH 455)
and
Neuroscience (PTRS 850)

Cerebral Cortex

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:

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:
  1. the presence if anastomoses. At-risk structures may then receive blood through an alternate route
  2. the size of the blocked vessel. Smaller vessels produce less widespread damage when blocked.
  3. health of remaining vessels. If surrounding vessels are healthy, new branches from those vessels may form.
  4. 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)
  5. location of lesion. Some lost functions are easier to live without than others.
  6. 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
  7. 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).

Association Cortex

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:

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?

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
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.

Reading disorders:

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.

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

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Last Update: April 2002