2 - Cerebral Hemispheres Flashcards by John Castillo

Organization of the Cortex

Neocortex - 6-layered (90% mass)
Allocortex - 3-layered (10% mass)
- Paleocortex (Olfactory)
- Archicortex (Hippocampal)

How well did you know this?

Not at all

Perfectly

Clinical: Columnopathies & Autism

Disorder or modular arangement of Cortical Columns

Autism Spectrum Disorder - too many column and subcortical white matter

How well did you know this?

Not at all

Perfectly

False Locatization

Focal lesions cause specific defects, but there is overlap–exam may yield incorrect findings

How well did you know this?

Not at all

Perfectly

Disconnection Syndromes

Impairments in signaling fibers between regions

How well did you know this?

Not at all

Perfectly

Cortical Signs

Aphasia

Alexia

Agraphia

Acalculia

Neglext

Visual Spatial Disorientation - early alzheimers

Memory Impairment

Behavior/Personality Change

Hemianopsia

Eye Deviation (destructive: toward side of lesion)

*Apraxia - can also be subcortical

How well did you know this?

Not at all

Perfectly

Clinical: Observe infant reflex (Palmar Grasp, Glabellar, Sucking, Snout, Babinski)

Possible cause?

Prefrontal Cortex lesion

How well did you know this?

Not at all

Perfectly

Agnosia

Deficits in sensory information processing, with no damage to sensory organs or memory circuits

Normal perception + stripped meaning

Damage to ventral stream of sensory perception

How well did you know this?

Not at all

Perfectly

Visual Agnosia

Apperceptive vs Associative

Inability to recognize visual obects

Associated with Left Occipital/Temporal Lobe lesions

May be either:

Appereceptive - unilateral failure of perception

Associative - bilateral failure of recognition despire accurate perception

How well did you know this?

Not at all

Perfectly

Clinical: Audtory Agnosia

Semantic-Associative vs Discriminative

Inability to recognize sounds; associated with Auditory Cortex/Temporal Lobe lesion

- - -

May be either:

Semantic-Associative - linguisitic left hemisphere

Discriminative - environmental sounds, music, right hemisphere

How well did you know this?

Not at all

Perfectly

Clinical: Contralateral Neglect

Sign?

Non dominant hemisphere

Constriction Apraxia

“Clock w/all the numbers on 1/2 the face”

How well did you know this?

Not at all

Perfectly

Major Association Pathways

Arcuate Fasciculus (think clinical)

Cingulate Gyrus

Within hemispheres ONLY

Arcuuate Fasciculus - Part of the superior longitudinal fasciculus, connects Broca’s and Wernicks’s — DISCONNECTION SYNDROME = Conduction Aphasia, can’t repeat

Cingulate Gyrus - Cells give rise to cingulum fibers, connecting emotion centers and the default mode network w/memory structures such as hippocampus and pary of limbic system

How well did you know this?

Not at all

Perfectly

Commissural Pathways:

Anterior Commissure

Connects temporal lobes, olfactory cortices, and olfactory bulbs

How well did you know this?

Not at all

Perfectly

Commissural Pathways:

Posterior Commissure

Connects pretectal structures (rostral midbrain)

How well did you know this?

Not at all

Perfectly

Commissural Pathways:

Corpus Callosum

When would you medically alter this structure?

Connects homotypical regions on both sides of brain

Can alter this structure (bisect) as a treatment option for extreme seizures; however may result in some sort of change for the patient

How well did you know this?

Not at all

Perfectly

Projection Pathways:

Corona Radiata

Passage of axons as they bundle and pass through capsules, once expanded they become the corona radiata that transverse the whole cortex

How well did you know this?

Not at all

Perfectly

Internal Capsule

Limbs: Anterior, Genu, Posterior

“The Big One”

Nearly all ascending/descending axons pass through here

Anterior - Frontal cortex

Genu - Corticobulbar

Posterior - Corticospinal, Sensory, Temporopontine, Visual/Auditory

How well did you know this?

Not at all

Perfectly

Medial / Lateral Geniculate

Medial sends information to Auditory Cortex (Brodman 41/42)

Lateral sends information to Optical Cortext (Brodman 17)

What blood vessel supplies the Internal Capsule and what does this result in?

Middle Cerebral Artery

Vulnerable for damage during strokes

Neostriatum

Lentiform Nucleus

Corpus Striatum

Neostriatum (C+P) - embryonically linked

Lentiform Nucleus (P+GP) - physically connected

Corpus Striatum (C+P+GP) - principle component of extrapyramidal motor system

C = Caudate

P = Putamen

GP = Globus Pallidus

Lateral Ventricles

Separation of Anterior Horns?

Clinical impact?

Septum Pallucidum separates anterior horns

Lie beneat cortical/subcortical system; any deficits (hydrocephalus, lesions, etc) can have impact on cortical/subcortical systems

What does presence of third ventricle on a cornonal cross section indicate?

you’re looking at the posterior limb of the internal capsule

Thalamus

Origin?

Major Function?

Origin: Diencephalon

Function: Receives precortical input, relays to higher areas = sensory and motor integration

*Does NOT receive Olfactory input

Thalamic Nuclei and Projections

IML

Reticular Nucleus

Internal Medullary Lamina (IML) - White Matter Tracts that divides thalamus into three primary regions (medial/lateral/anterior nuclear groups)

Reticular Nucleus - Does not project to cortex; inhibitory circuits that project back to thalamus

Functional Divisions of the Thalamus:

Sensory

VPL

VPM

LGN

MGN

Functional DIvisions of the Thalamus: Motor

VA VL

Clinical: Abnormalities of Thalamus Paresthesia and Dejerin-Roussy Syndrom (Thalamic Pain Syndrome)

Paresthesia - Aberrant positive sensations; contralateral tingling or numbness; may be innocuous or painful - - - Thalamic Pain Syndrom (Dejerine) - Contrallateral lack of sensation and tingling that prigresses to severe pain; follow **Thalamic Stroke**

Clinical: Abnormalities of Thalamus Dysesthesia Allodynia Hyperalgesia Hemianesthesia Homonymous Hemianopsia

Dysesthesia - Abnormal, unpleasant sense of touch (can be painful) Allodynia - Painful stimulus induced by innocuous stimuli Hyperalgesia - Enhance pain to hamful stimuli Hemianesthesia - Contrallateral loss of sensation (damage to VPL/VPM) Homonymous Hemianopsia - Loss of same half of each visual field (damage to LGN)`

VPL - Ventral Posterolateral VPM - Ventral Posteromedial LGN - Lateral Geniculate Nucleus MGN - Medial Geniculate Nucleus

VPL - Ventral Posterolateral: **Sensory Relay - Body** VPM - Ventral Posteromedial: **Sensory Relay - Face** **BOTH: Vibration, Pain, Pressure, Proprioception, Light Tough** **- - -** LGN - Lateral Geniculate Nucleus: **Sensory Relay - Retinal Axons to Optic Radiations (VISION)** MGN - Medial Geniculate Nucleus: **Sensory Relay - Auditory Axons to Auditory Radiations (HEARING)**

Brodman: Motor Sensory Visual Auditory

Motor - 4 Sensory - 3/1/2 Visual - 17 Auditory - 41/42

MCA Stroke: Dominant Hemisphere Non-Dominant Hemisphere

Dom - Global Aphasia Non-Dom - Hemispatial Neglect

PCA Stroke?

Pure Alexia (Loss of reading ability)

Changes in hypersexuality/hyperaggression?

Damage to **Amygdala**

Two causes for homonymous hemianopia?

1. Internal capsule damage 2. Lateral Geniculate nucleus

Where vs What streams?

Where - Dorsal Stream What - Ventral Stream

Akinetopsia

Motion blindness, Lateral Occipital Lob damage

Fusiform Gyrus damage

Prosopagnosia (inability to recognize faces)

Associational Fibers Arcuate Fibers Major arcuate fiber?

Intrahemisphere connections - - - Connect adjacent gyri - - - Superior Longitudinal Fasciculus--connects Frontal to Occipital lob

Clinical: Lesion of Arcuate Fasciculus

Conduction Aphasia (Broca/ Wernicke connection)

Limbic System Functions

HOME Homeostasis Olfaction Memory Emotion