Cerebral Cortex

What are pyramidal cells?

• Output cells for cerebral cortex

• Axons travel through white matter as projection, commissural, or association fibers

What are nonpyramidal cells?

• Small interneurons that remain within cortex

• Most common = granule / satellate cells

What are projection fibers?

• Fibers convey signals from subcortical structures → cortex

• Convey signals from cortex → SC, basal nuclei, & thalamus

What are commissural fibers?

• Fibers connect cerebral hemispheres

• Homologous areas

• Ex: corpus callosum, anterior commissure, posterior commissure

What are association fibers?

• Fibers connect cortical regions within 1 hemisphere

• Ex: short association, superior longitudinal fasciculus, inferior longitudinal fasciculus

What are the Brodmann’s Areas?

• Cortex divided into 52 areas based on cytoarchitecture

• Ex: neuron shape, size, density, staining

What are the 4 main functional areas of the cortex?

1. Motor

2. Sensory

3. Association

4. Limbic

What does topographical organization of the cortex mean?

• Bodies’ surface, range of audible frequencies, or outside world is mapped onto cortical surface

• Cortical zones most directly related to outside world

• AKA homunculus

What are the association ares of the cortex responsible for?

• Complex processing b/w input & generation of behavior

• Cognition → learning the world

What does cognition allow us to do?

• Attend to external stimuli or internal motivation

• Identify significance of stimuli

• Plan meaningful responses

What is the difference between unimodal and heteromodal association areas?

• Unimodal → process info from 1 sense modality

• Heteromodal → process info from multiple sense modalities (MOST COMMON)

How do functional areas progress?

Primary area → Unimodal association area → Multimodal association area

Describe primary motor cortex.

• Thickest cortex in brain

• Discrete movements in 1 muscle or small group of muscles

• Very exact

• Voluntary controlled movements

• Lesions → paresis (weakness), loss of fine motor control

Describe premotor motor cortex.

• Slower movements

• Mainly larger muscle groups

• Plans voluntary contractions

• Control of trunk & girdle, anticipatory postural adjustments

• Lesions → apraxia (difficulty with motor planning)

Describe supplementary motor cortex.

• Assumptions of postures

• Involves muscles on both sides

• Initiation of movement, orientation & planning

• Lesions → Apraxia (difficulty with motor planning)

Describe Broca’s area.

• Motor programming of speech

• ONLY in left hemisphere

• Lesion → Broca’s aphasia

Describe primary somatosensory area.

• Somatosensory info travels in from DCML & STT

• Relays info to VPM & VPL of thalamus

• Travels through posterior limb of internal capsule

• Projects to S1

Describe somatosensory association areas.

• Receives info from S1 & helps process sensory info delivered to S1

• Some input from VPL & VPM

What is the function of the left hemisphere?

• Language production & comprehension

• Assembling sensory info to plan movements accurately

• Math center

• Problem-solving in sequential, logical fashion

What is the function of the right hemisphere?

• Spatial attention

• Musical skills

• Recognition of faces

• Tasks requiring comprehension of spatial relationships

Describe language.

• Lateralized in human brain to left hemisphere

• Language deficits more likely from damage to left hemisphere

What is the difference between Broca’s area and Wernicke’s area?

• Broca’s → generation of language (motor)

• Wernicke’s → comprehension of language

What are the 3 types of aphasia syndromes?

1. Broca’s aphasia → comprehension intact but difficulty finding the right words

2. Wernicke’s aphasia → fluency intact but reduced comprehension

3. Global aphasia → lose both fluency & comprehension

Describe spatial attention.

• Lateralized to right hemisphere

• Mediated by right parietal association cortex

• Damage to right parietal lobe → contralateral neglect (left)

Describe the corpus callosum.

• Commissural fibers connecting the cerebral hemisphere

• Largest fiber bundle in human brain

• Most connect mirror-image sites

Describe anterior commissure.

Commissural fibers connecting left & right temporal lobes

What is a corpus callostomy?

• Surgical severing of the corpus callosum

• Treats intractable epilepsy

• Leads to split-brain presentation

What are common causes of brain injury?

• CVA (stroke)

• TBI

• Brain tumor

What are possible clinical presentations of brain injury?

• Paresis, paralysis

• Spasticity

• Agnosia

• Apraxia