Cerebral Cortex: Frontal & Parietal Lobes
What is Wernicke's area?
(=Brodmann's 22) is vital for Recognizing the words from sounds.
What is Broca's area?
(=Brodmann's 44 and 45) is vital for Speech Production. Has 'programs' for Articulation.
What is Stereognosis?
(a.k.a. Discriminative Touch / Sensory Discrimination): Recognize object in hand by moving it around, without looking; Integration of Touch, Pressure and Conscious proprioception to give size, form, texture of object (Note: These are all Spinal Dorsal Column sensations)
What are problems if there is a Dominant hemisphere lesion?
1. Aphasia 2. Acalculia 3. Apraxia
Lesions to Non-dominant hemisphere
1. Neglect Syndrome 2. Construction / Dress Apraxia
What are the 3 heirarchial levels of movement?
1. Reflex action : automatic 2. Stemiautomatic, stereotyped (basal ganglia) 3. Voluntary skilled: learned (cortex & basal ganglia)
What is dysarthria?
A condition where the actual muscles used for speaking are weakened, causing someone's speech to be slurred. People may have difficulty understanding them, because the speech is so mumbled.
Recap: What is the right (non-dominant) posterior parietal lobe important for?
Attention/ to space & body
Patient presentation: Doctor: "What kind of work do you do?" Mr. Tan: (Patient speaks slowly) "Bread.....cakes...cookie....cash... chocolates....people...people" What is the problem?
Broca's aphasia - Non-fluent, slow, lacks melody, plenty of content words, no function words, listener often gets a gist of what is said, "telegraphic" speech. Could be irritable and disturbed due to insight into his problem. Differential diagnosis : depression b/c pt is AWARE of problem
What sulcus runs btwn the frontal & parietal lobes?
Central sulcus
What is construction / dress apraxia?
Construction: Pt can't draw or assemble objects. No problem mimicking or using objects to perform complex tasks. Dress: Problem with spatial mapping
How does the posterior parietal lobe on the left side communicate with the right frontal lobe?
Corpus callosum
Apraxia occurs most often with what lesions?
Dominant parietal and/or frontal hemisphere - depending on location of damage --> creates different types of apraxia.
Describe the connections from frontal eye field to the PPRF:
From Visual Cortex; To Midbrain (Superior colliculus, Pretectal nucleus, Bilateral CN 3 nuclei; To Pons (Horizontal gaze center (Paramedian pontine reticular formation; PPRF))
What are the major lobes of the cerebral cortex?
Frontal Parietal Occipital Temporal
What is the name of the syndrome when a patient presents with "Acalculia, Agraphia, Alexia, Left-Right Confusion."
Gerstmann's syndrome (again - a lesion in the angular gyrus)
Stimulation of primary gaze center causes eyes to look where?
Horizontal conjugate deviation eyes to opposite side
Damage to the prefrontal lobe of the cerebral cortex may exhibit what kind of behavior?
Impulsive, hostile & thougthless of others. Perseverative (stereotyped movements). Could not plan actions.
What is apraxia?
Inability to perform learned (practiced) movements in absence of impaired attention, aphasia, paralysis, in-coordination, sensory loss or involuntary movements.
Phineas Gage is a good example of what kind of damage to the brain?
Injury to prefrontal lobe of cerebral cortex
Describe the Association area of the Cortex:
Integrates various sensory modalities and motor plans. Involved in higher cognition. Note: Most of the cerebral cortex is involved in integration. Thus, four-fifth of the cortex is association area.
What is aphasia?
It has to do with the ability to find the right words.
Role of motor areas: What is the role of the premotor cortex?
It important for spatial exploration while acting with the objects in the environment. E.g. Reaching for a cup
Role of motor areas: What is the role of the prefrontal cortex?
It plans for various movements. It selects the action and follows through with attention / "Executive function".
If there is a stroke in my left frontal eye field my eyes will move?
LEFT
What sulcus partially separates the temporal cortex from the frontal & parietal lobes?
Lateral suclus (sylvian fissure)
Where is the lesion for a pt to present with Acalculia?
Lesion of angular gyrus "Einstein's area" The pt may present with: Acalculia, Agraphia, Alexia, Left-Right Confusion.
Role of motor areas: What is the role of the supplementary motor area (SMA)?
Major connections with basal ganglia. Performance of complex sequence pattern: E.g. In monkeys: Push-Turn and Open to procure a treat.
What kind of neurons allow us to mimic an action by observation alone?
Mirror neurons - Neurons extending from occipital, parietal and temporal cortex to premotor areas get activated when observing someone else perform an action.
Dorsolateral cortex is involved in what kind of behavior?
Motor Plan, Attention and Execution Integrates parietal polymodal cortex with: Premotor cortex Supplementary motor area Pyramidal and Extrapyramidal systems (Blue highlight)
What is hemineglect?
Neglect of one side
If there is a lesion to the right non-dominant parietal lobe, what will the patient present with?
Neglect syndrome - specifically to their left side
What happens to your sense of external space and body if you lesion the LEFT parietal lobe?
Nothing. b/c the right side is fine- which is responsible for paying attention to external space and body is not lesioned
What is hemiplegia ?
Paralysis of one side
Apraxia should not be confused with what?
Paralysis: Inability to move (Lesion: Pyramidal tract; LMN/ UMN) Akinesia: Lack of initiative to perform certain movements (Lesion: Basal ganglia; Parkinson's disease)
On a MRI what areas of the brain will light up if someone imagines spatial navigation?
Parietal, parahippocampal and premotor activation with spatial navigation imagery.
What sulcus separates the occipital lobe from the parietal lobe on the medial side of the hemisphere?
Parietooccipital sulcus
What is the frontal lobe divided into?
Pre-central gyrus (primary motor cortex/ Area 4 ), Premotor cortex, Supplementary motor area, Broca's area (Area 44), Frontal eye-field and pre-frontal cortex.
What is Graphesthesia?
Recognizing writing on skin
What is the purpose of the non-dominant hemisphere? (right parietal lobe)
Right parietal lobe (non-dominant hemisphere) is important in paying attention to body and external space NOTE: -->Right parietal lobe predominantly attends to left half of the body and space -->Right side of the body and space gets divided attention from left as well as right parietal lobes.
What is the difference between the 2 sensory cortexes?
SI : processes sensory inputs -receives input from skin, tendon, joints, muscles, etc.) SII: integrates AND processes
Role of motor areas: What is the role of the primary motor cortex?
SIMPLE movements A single neuron fires for simple movement (flexion/extension)
On an MRI, what areas of the brain will light up if someone imagines a physical movement (like playing tennis)?
SMA activation during tennis imagery
Describe the Primary area of the cortex:
Sensory-Receives sensory inputs; Motor-Sends basic commands for movement
Ventromedial, Orbitofrontal cortex and anterior cingulate are involved in what kind of behavior?
Social Behaviour Integrating: External Sensory inputs Internal Visceral inputs and Limbic system (amygdala) Impulse control. (Green highlight)
In what general areas are mirror neurons strongly implicated?
Social communication Language development Understanding a command Mental rehearsal Imitation of an action Understanding metaphors...
What do we inject during the Wada test?
Sodium amobarbital is injected into the carotid artery which will anesthetize the hemisphere where it is injected (in this case, the left hemisphere)
What are 2 association cortex integration sensations?
Stereognosis Graphesthesia
Describe the Wada test:
Tell pt to keep counting and keep hands up as long as they can - while they do that inject sodium amobarbital into Left carotid artery --> right hand goes down AND speech goes down --> shows speech is contralateral to the hand that went down. (Right hand goes down and speech stops = speech area on Left hemisphere ). If right hand goes down but speech remains, then the speech must be on the right side. Over a period of time both sides will be affected as circulation goes throughout the brain - so this is an instant test that must be assessed immediately
What is the purpose of the Wada test?
To confirm which speech area is dominant for the patient - to prevent damage to that area during surgery
How does a spoken command become an action?
Understanding the command comes from Wernicke's. WHAT to do with the command comes from the Dominant Left Posterior Parietal lobe. HOW to do the command comes from bilateral frontal lobes, BUT they must be stimulates by the posterior parietal lobe.
What test is performed prior to conducting any surgery suspecting speech areas?
Wada test
Patient presentation: Doctor: "What kind of work do you do?" Ms. Wern: (Speaks fluently) "Rain, yesterday, tico, to, white I gotta go. She-her, angry he come, I don't know why, always up and down, up and down, tira-tira, about around here." What is the problem?
Wernicke's Aphasia: Fluent, melody may be intact, plenty of function words, few content words, listener can make no sense of what is said, "word salad" neologisms (new words). No insight into the problem. Differential diagnosis: Schizophrenia.
What happens if you lesion the RIGHT posterior parietal lobe?
Will show NEGLECT of left side of the body
The dominant hemisphere of the brain (our left parietal/frontal lobes) holds what areas for language and where?
a. Wernicke's area (22) = Understanding speech b. Supramarginal gyrus* contains arcuate fasciculus that connects Wernicke's and Broca's areas c. "Einstein area" (Angular gyrus) ** Lies immediately behind supramarginal gyrus- Important for counting with fingers, spatial orientation, right-left perception
Although all movements are performed by the frontal lobe , what lobe are required for feed-back and instructions?
parietal
What is dress/ consttructional apraxia?
special type associated with hemineglect **MOST apraxias occur w/ lesions in DOMINANT hemsphere
How many somatosensory areas are there on the somatosensory cortex?
two: Primary somatosensory area / SI (3,1,2) Secondary somatosensory cortex (SII)
