Midterm 2 Flashcards
Brodmann’s Areas
Definition: Areas defined and numbered based on cytoarchitectural organization of neurons using the Nissl method of cell staining.
- Defined solely based on neuronal organization
- Correlate closely with diverse cortical functions
Univocal (modality-specific) association vortices
1) Primary sensory cortex
2) Primary motor cortex
3) Primary auditory cortex
4) Primary visual cortex
Heteromodal (higher-order) association cortices
1) Unimodal association cortex
2) Heteromodal association cortex
3) Prefrontal cortex
Primary Motor Cortex
Brodmann Area: 4 aka M1
Function: Works in association with premotor cortex, supplementary motor area, sensory and posterior parietal cortex and several subcortical brain regions to plan and execute movements.
- Precentral gyrus
- Contains somatotopic maps of contralateral body movements
- Target for cerebellum and motor thalamus projections
Lesion: Varied degrees of focal paralysis in the CONTRALATERAL side of the body or face.
Primary Sensory Cortex
Brodmann Area: 1, 2, 3
Function: Interlocked with primary motor cortex to send projections to the superior and inferior parietal lobules.
- Somatotopic map of contralateral body sensations
Lesion (General): Varied degrees of focal impairment in sensation on the CONTRALATERAL side.
Primary Sensory Cortex: Lesions
Acute (immediate stage): Loss of all sensory modalities on the contralateral side of body and/or face.
Chronic (later stage):
- Recovery of sensation of pain and temperature and crude touch sensation
- Thalamic level- sensation of pain and temp
- Sensory cortex- source, quality and intensity of pain
- Continued loss of fine aspects of tactile information on the contralateral body (arm and face)
- Loss of two-point discrimination
- Agraphesthesia
- Astereognosis
- Loss of vibration and light touch
- Continued loss of pro prince potion in contralateral body (arm and face)
- When leg is involved get positive Romberg sign (ataxia when eyes are closed)
Lesions to insulate and SII (maybe anterior cingulate)
Asymbolia for pain- Lack of motivation to avoid pain.
Agraphestesia
Inability to recognize a latter outlined on the skin.
Astereognosis
Inability to recognize form.
Organization and Pathways of the Somatosensory System
1) Dorsal root ganglion neurons respond to find touch adn pressure, pain and temp
2) Ventral spinothalamic tract receives input from pain and temp neurons and joins medial lemniscal tract
3) Dorsal column nuclei relay fine touch and pressure sensations.
4) Medial lemniscus contains axons that carry sensory information to the ventrolateral thalamus
5) Ventrolateral thalamus relays sensory information to the somatosensory cortex.
6) Primary somatosensory cortex receives somatosensory information.
- Homunculus
- Topographic map
- Disproportionate cortical representation of body parts
Temporal Lobe: Primary Auditory Cortex
Brodmann areas: 41, 42
- Transverse Gyri
- Represent acoustic frequencies and intensities of unhitched sounds to permit recognition and spatial localization
- Each receives input from both ears–> Unilateral damage does not cause deafness
- Surrounded by association auditory cortex
Lesion: Bilateral- auditory agnosia
Unilateral in dominant hemisphere- Pure word deafness
Unilateral in non-dominant hemisphere- Amusia (inability to produce or recognize musical sounds)
Temporal Lobe: Medial Temporal Lobe
- Cortical and subcortical structures of the limbic system
- Entorhinal cortex
- Hippocampal formation
- Amygdala
Lesion:
-Entorhinal and hippocampal formation = memory –> Anterograde memory impairment - Amygdala- Kluver-Bucy Syndrome
Kluver-Boucy Syndrome
Syndrome associated with lesions to the amygdala in which there is a marked decrease in the ability to express emotions.
Primary Visual Cortex
Lesions:
- Upper calcarine - lower field defect
- Macular sparing: Many blood vessels at the tip of the cortex for the center of vision so the center of vision is spared
- Blood from PCA and MCA
Prefrontal Cortex
- Contains areas that mediate higher mental functions
- Broca’s Area
Broca’s Area
Brodmann Area: 44, 45
- Lateral Sylvian fissure
- Pars triangularis and opercularis
- Connected to Wernicke’s area via accurate fasiculus
- Mostly in the left hemisphere because language lateralized to left (left-handed is three way split between left, right and both) - Language distinct from speech- speech supported by the entire motor system for vocalization
Arcuate fasiculus
Structure that connects Wernicke’s and Broca’s areas
Association Sensory Cortex
- Superior and inferior parietal lobules
- Connects Wernicke’s and Broca’s areas
Lesion: - Dominant hemisphere
- Inferior parietal lobule
- Angular gyrus: Alexia and agraphia (inability to read written language and inability to write language)
- Supramarginal gyrus: Conduction aphasia
- Superior parietal lobule- Optic ataxia in contralateral hand
- Can’t use the visual system to guide motor movements so reaching for anything is like reaching into the dark - Non-dominant hemisphere
- Inferior parietal lobule- Anosagnosia (unaware of their condition)
- Left visual field neglect (can’t follow previously known and automated route, not hit obstacles on left side, can’t learn new route) - Superior parietal lobule- Optic ataxia
- Inferior parietal lobule- Anosagnosia (unaware of their condition)
Object Agnosia
- Bilateral inferolateral parts of occipital lobes
- Patient fails to name or indicate the use of a seen object
- Vision is intact because patient can see an object but can’t tell what it is
- If object is touched or smelled or makes a sound then it can be recognized
Achromatopsia
Failure to recognize color.
- Inferior occipital cortices
- Sparing calcarine cortex
- Contralateral
Prosopagnosia
Inability to recognize faces but able to see the face.
- Bilateral occipitotemporal
Anton’s Syndrome
Denial of blindness
- Bilateral occipital cortices from calcarine and extending superiorly to parietal cortex.
Anatomical and Functional Asymmetry
- Slope of lateral (sylvian) fissure differs
- Wernicke’s area mostly left hemisphere
- More auditory cortex in the left
- Left more verbal and right is more non-verbal
- Left temporal lobectomy: Low verbal recall
- Right temporal lobectomy: Low non-verbal recall (performance IQ too, but may be unrelated)
Commissurotomy
Split brain
- Put object in left hand, patient cannot name object but if you put the same object in the right hand patient can name it