Cerebral cortex Flashcards
What are the two parts of the cerebrum?
- Diencephalon: Thalamus, Hypothalamus, Epithalamus, and Subthalamic nucleus
- Telencephalon: Subcortical structures [White matter, Basal Ganglia], Cerebral Cortex
fibers that connect regions of the same side of the brain; connect different areas of the brain
association fibers
Fibers that connect similar regions of the left and right side of the brain
Commissural fibers
fibers that carry info into the cortex or out from the cortex
projection fibers
How many layers does the neocortex have?
6 layers
- cortex of higher order thinking
Receives input from thalamic regions; Only one type of sensation (Somatosensory, Auditory, Visual, or Vestibular); Representation of sensation is topographically organized
Primary Sensory Cortex
What broadman’s area is the somatosensory cortical area?
3, 1, and 2 (pre central gyrus)
Cortex Function: Location of stimuli, Discriminate among shapes, sizes and textures
Primary somatosensory cortex
- parietal lobe
What S and S will you see with damage do the primary somatosensory cortex?
- Loss of discrimination – location and strength
- Crude awareness intact
- Localization of pain intact
What is the pathway for hearing?
Cochlea –> Cochlear nucleus –> inferior colliculus/medial geniculate body –> CTX
What S and S will you see with damage to the primary auditory cortex?
loss of localization of sound
- you can still hear, just not where its coming from
Cortex Function: Conscious awareness of sound – bilateral, Not extremely well lateralized
Primary auditory cortex
- temporal lobe
Cortex Function: Information about head movement and position, Information also travels through thalamus
Primary vestibular cortex
What S and S will you see with damage to the primary vestiular cortex?
Loss of conscious awareness of head position and movement
Cortex Function is to distinguish: Light/dark, Various shapes, Location of objects, Movement of objects
Primary visual cortex
- occipital lobe
- brodmann’s area 17
What S and S will you see with damage to the primary visual cortex?
contralateral homonymous hemianopsia
- macular vision spared
Contribute to the analysis on one type of sensation – unimodal; Usually located adjacent to primary sensory cortex for that modality; Input from both primary sensory cortical area and the thalamus
Sensory association areas
- stereognosis (ability to identify an object)
What S and S will you see with damage to the sensory association areas?
Agnosia – inability to identify something using one sensation (can describe, can’t identify)
Where do the projections of the sensory association areas go to?
Primarily to primary motor cortex and also to Association areas
- Important in formulating motor plans for complex movements
What Broadman area is the somatosensory association cortex?
5, 7
Cortex Function: Integrate tactile and proprioceptive information, Stereognosis, Memory of tactile and spatial environment
Somatosensory association cortex
What S and S will you see with damage to the somatosensory association cortex?
- Astereognosis
2. May avoid affected hand
Cortex Function: Compares sounds with memories of other sounds, Categorizes sounds as music, language or noise
Auditory association cortex
- Brodmann’s area 22, 42
What S and S will you see with damage to the auditory association cortex?
Auditory agnosia:
- Left – unable to understand speech (the word part of language)
- Right – loss in interpretation of noises (the tone used while talking, injury = monotone, flat affect)
What are the primary motor and motor planning areas?
- Primary motor cortex
- Supplementary motor cortex
- Premotor area
- Broca’s area
- Area corresponding to Broca’s area on the language non-dominant side of the brain
- last 4 are motor planning areas
What S and S will you see with damage to the visual association cortex?
Visual agnosia is contralateral visual field
Cortex Function: Analyzes colors and motion, Directs visual fixation
Visual association cortex
- Brodmann’s area 18-21
Location – precentral gyrus, anterior part of paracentral lobule;
Function: Source of many corticospinal neurons; Contralateral voluntary movements for lower face and extremities; Bilateral voluntary movements for upper face and back muscles
Primary motor cortex
- Brodmann’s area 4
What S and S will you see with damage to the primary motor cortex?
- Contralateral paresis – mostly in lower face and distal extremities
- Loss – fractionation
- Speech problems – spastic dysarthria (UMN disorder; Harsh, awkward speech)
Functions: Motor speech, Planning movements of mouth, Grammar (All the little word that help a sentence make sense)
Broca’s area
- unilateral, usually on the L side
- areas 44 and part of 45
Functions: Similar to Broca’s area but for non-verbal communication; Plans nonverbal communication; Adjusts tone of voice
Area contralateral to Broca;s
- unilateral, usually on R side
Inability to perform voluntary movements; Can perform involuntarily
What area is damaged?
Apraxia;
Damage to PMA or SMC
Uncontrollable repetition of a movement
What area is damaged?
Motor preservation;
Damage to SMC
Difficulty producing verbal communication
What area is damaged?
Broca’s aphasia
- damage to Broca’s area
Difficulty producing nonverbal communication
What area is damaged?
damage to area homologous to broca’s area
What is in the subcortical white matter?
- Thalamus
- Lenticular nucleus
- Internal capsule
What part of the internal capsule contains corticobulbar fibers? corticospinal fibers?
Corticobulbar = genu
cortico spinal = anterior (ant limb) and posterior (post limb) parts of the internal capsule are for limbs
- all sensation and motor info travels thru internal capsule
Has motor and cognitive functions; injury to this area results in motor deficits and behavioral deficits (Loss of initiative, Spontaneous thought, Emotional responses)
Basal ganglia
- 2 disorders = schizophrenia and addiction
Area function: Voluntarily controlled movements
Primary motor cortex
Area function: Control of trunk and girdle muscles, anticipatory postural adjustments; Medial activating systems
Premotor area
- lateral part of area 6
Area function: Initiation of movement, orientation planning of head and eyes, bimanual and sequential movement
Supplementary motor area
- medial and superior area 6
Area function: planning nonverbal communication (emotional gestures, tone of voice)
Areal contralateral to Broca’s area
What are the inputs to the primary motor cortex?
- Sensory input from thalamus and primary somatosensory cortex
- Motor input from motor planning regions
- Motor input from basal ganglia and cerebellum via the thalamus
What are the inputs to the motor planning regions?
- Sensory information from sensory association areas
2. From BG and Cb – relayed by the thalamus
Multimodal association cortical areas - Integration of sensory information for multiple modalities; Most of neocortex in humans; NO direct motor or sensory areas (Do not receive direct sensory input; Do not project to LMN)
Heteromodal association cortex
- receives info from sensory areas in cortex
- output to motor areas in cortex
What are the higher intellectual functions in the association cortex?
- Abstract reasoning
- Complex planning
- Personality
- Processing of memory
- Generation of emotions
What area of the association cortex is injured when there is a loss of executive function and divergent thinking?
Dorsolateral prefrontal association cortex
What area of the association cortex is injured when there is inability to handle new information effectively; concrete thinking, inability to distinguish relevant from irrelevant information, difficulty generalixing information, become upset with even minor changes in routine
Pariototemporal association
Definition: Some functions located on one side of the cerebral cortex;May speed up processsing if it is all done on one side
Hemispheric specialization
- i.e., non-verbal communication = right side, verbal communication = left side
When doing simple movements, which hemisphere tends to control?
contralateral to dominant hemisphere
When carrying out skilled, complex tasks, which hemisphere controls this?
Dominant hemisphere
- most people are left cerebral hemisphere dominant (right handed)
- Lesions of left hemisphere more often associated with apraxia – difficulties formulating skilled movements
What hemisphere is usually dominant for language?
if you are right handed = 95% of the time left hemisphere
Left handed = 60-70% of the time left hemisphere
- Language function may be more bilateral
- Tend to recover language faster
For language, what is the non-dominant side responsible for?
- Non-verbal communication
- Emotional aspects of events and language
- Musical perception
What hemisphere is involved in attention?
Both:
- R side pays attention to both sides of the world
- L side pays attention to ONLY the R side of the world
- R side stroke produces inattention to left
What is the dominant side’s functions (in summary)?
- usually L
1. Language
2. Skilled motor formulation (praxis)
3. Arithmetic: sequential and analytical calculating skill
4. Musical ability: sequential and analytical skills in trained persons
5. Direction: Following a set of written directions in sequence
What is the non-dominant side’s functions (in summary)?
- Prosody - emotion conveyed by tone of voice
- Visual-spatial analysis and spatial attention
- Arithmetic: ability to correctly line up columns of numbers on a page
- Music ability - in untrained persons. complex musical pieces in trained musicians
- Direction: finding one’s way by overall sense of spatial orientation
What are the higher order cerebral functions?
- Language
- Attention and spatial processing
- Frontal lobes
- Visual processing
- Attention and Awareness
What brain regions are involved in language?
- Primary auditory cortex
- Wernicke’s area (part of auditory association cortex) – assigning meaning to words
- Primary motor cortex for the face
- Broca’s area (association cortex)
What connects Broca’s and Wernicke’s area?
Arcuate fasciculus
Primarily involved in language comprehension; Maps sounds to meaning in order to produce meaningful language (lexicon); Comprehension; Production
Wernike’s area
Higher level aspects of speech formulation and planning ; Correct syntax of language comprehension and production
Broca’s area
Deficit in language processing; Injury to language dominant hemisphere; Affects both spoken and written language
Aphasia
Decreased fluency of spontaneous speech: Phrase length of fewer than 5 words; More content words (nouns) than function words (prepositions, articles, etc.); Can be tested by word generation tasks; difficulty getting words out (naming difficulties); No “ifs, ands or buts” (impaired repetition)
Broca’s Aphasia
- mostly nouns, some verbs
- writing and reading aloud = slow, agrammatical and effortful
- frustration and depression common with pts
- writing = Effortful, agrammatical and sparse
Where would a stroke occur if it effects Broca’s area?
MCA - superior division
Where would a stroke occur if it effects Wernicke’s area
MCA - inferior division
Impaired comprehension; Do not respond appropriately to questions or commands; May respond to some commands about axial muscles; Normal fluency, prosody and grammatical structure; Sentences do not have meaning (Paraphasic errors- Replace word with one of a similar meaning, Replace part of a word with a similar sound; Neologisms – make up new word); Impaired naming
Wernicke’s aphasia
- writing: Fluent, paraphasic and largely incomprehensible
What would happen if Wernicke’s area was disconnected from Broca’sarea?
Impaired repetition
- reading and writing have similar deficits
What are the associated [areas] dysfunctions
- Contralateral visual field cut
- Apraxia may be present – difficult to assess due to aphasia
- Often appear unaware of disorder
- May exhibit angry or paranoid behavior
Reading and writing impairments; Deficits in central language processing; Deficits in patients with aphasia tend to mirror the aphasia
Alexia (reading) and Agraphia (writing)
- Patients with aphasia have agraphia
inability to carry out an action in response to a verbal command, in the absense of any comprehension deficit, motor weakness or incoordination
Apraxia
Ask patient to carry out an imaginary action:
- Awkward looking attempts
- Perform tasks ineffectually
- 1/3rd of patients with aphasia have some apraxia
- can just be specific regions
Small lesion in Broca’s area that results in:
- Motor speech deficits
- Writing is intact
Aphemia (in adults)
- developmental disorder in children = verbal apraxia
Lesion to bilateral auditory cortex
Cortical deafness
Can identify non-verbal sounds; Cannot understand spoken words; Can read and write normally; Lesion to auditory cortex of dominant hemisphere which extends deep to the subcortical white matter
Pure Word deafness
AKA verbal auditory agnosia
Where are the functions of global attention (Vigilance, Concentration, Generalized Behavioral Arousal) and selective or directed attention (Focusing attention on a specific domain)
Non-dominant hemisphere
attention/spatial processing
What association cortex injury results in disturbances of personality and emotions?
Ventral and medial dorsal prefrontal association
What does the heteromodal association cortex have bidirectional connections with?
- Motor and sensory association areas
2. Limbic cortex
