Functional Neuroanatomy Flashcards
What are the three main components of the brain
1) Forebrain: cerebral hemispheres and diencephalon
2) Midbrain
3) Hindbrain (brainstem): medulla, pons, and cerebellum
What does ventral/dorsal mean?
Inferior/Superior
What does rostral/caudal mean?
Anterior/Posterior
What is the horizontal Plane?
Parallel to the floor
What is the coronoal plane?
Perpendicular to the floor and cuts across the brain (wearing a crown)
What is the saggital plane?
Perpendicular to the ground from forehead to occiput (like an archer shooting arrow with a bow)
What is grey matter?
- Cell bodies of neurons
- Basic synaptic communication occurs here
What is white matter?
- Myelinated axons
- Tracts provide communication among cortical areas and between cortical and subcortical structures
- Disconnection syndromes arise from damage to WM pathways
What are the three main regions of the frontal lobe?
- Orbitofrontal/ventromedial region
- Dorsolateral region
- Dorsomedial region
What are the main functions of orbitofrontal and ventromedial regions?
- Emotion regulation, reward monitoring, and personality
- Damage to orbitofrontal= disinhibition
- Damage to ventromedial= disordered reward/punishment processing
What are the main functions of the dorsolateral region?
- Cognitive-executive functions including working mem
- Damage= dysexectuive syndromes, poor WM and inattention
What are the main functions of the dorsomedial region?
- Intentional and behavioral activation
- Damage= impairment in initiated behavior (e.g., akinetic mutism)
What are the three main areas in the temporal lobes?
- Temporal polar cortical areas
- Ventral temporal areas
- Posterior temporal region
What is the function of the temporal polar cortical areas?
Important for intersensory integration and semantic memory
What is the function of the ventral temporal areas?
Important for object recognition and discrimination. Bilateral damage produces object or face agnosia
What is the function of the posterior temporal areas?
- Middle and superior temporal sulci
- Primary auditory areas and Wernicke’s area in language dominant hemisphere
- Important for language comprehension
Name the three main components of the parietal lobe.
- Superior parietal lobe
- Tempoparietal junction
- Inferior parietal lobe
What is the function of the superior parietal lobe?
Important for sensory-motor integration, body schema, and spatial processing
What is the function of the tempoparietal junction?
- Important for phonological and sound based processing
- Language comprehension (left) and music comprehension (right)
What is the function of the inferior parietal lobe?
Important for complex spatial attention, integration of tactile sensation, and self-awareness
What are the two main pathways of the occipital lobe?
Origin of two main visual-cortical pathways: ventral and dorsal
What is the ventral visual pathway?
- Connects occipital and temporal lobe
- Object and face recognition, item-based memory, and complex visual discrimination
- Processes structural and feature based information
What is the dorsal visual pathway?
- Connects the occipital and parietal lobes via the superior temporal sulcus
- Spatial vision and visuomotor integration
- Processes spatial information
- Visuomotor interaction in the environment
How many layers does the neocrotex have?
- Has 6 layer laminar structure
- Each layer has distinct output connections
- Layer IV= inputs from the thalamus
- Layers II and III= cortico-cortico connections
Where do retinal ganglion cells project?
-Send axons into the optic nerve & projects posteriorly
Optic chiasm
- Optic nerve comes together to form the optic chiasm
- Optic tracts originate here
What is the geniculostriate pathway and it’s main function?
- Optic tract fibers –> LGN of the thalamus–>primary visual cortex (BA 17; striate cortex) in the occipital pole
- Visual discrimination and form perception
What is the tectopulvinar pathway and it’s main function?
- Optic tract fibers–>pretectal & superior colliculus–>parietal & frontal association cortex via the pulvinar nucleus of the thalamus
- Pupillary light reflex, attention-directed eye movements, orientation to visual stimuli
- Movement rather than form perception
How many layers does the archicortex have?
- 3 layers
- Limbic cortex
What substrates are in the hippocampus, and what is it’s main purpose?
- Consists of dentate gyrus, sectors of Ammon’s horn (CA 1-4) and subiculum
- Archicortical and more closely related to the neocortex than the amygdala
- Critical for episodic memory
Describe the trisynaptic circuit.
- Internal connections of the hippocampus
- Entorhinal cortex–>dentate granule cells (synapse 1)–>CA3 mossy fibers (synapse 2)–>CA 1 (synapse 3)–>subiculum–>entorhinal cortex
- Unidirectional connections
What is the subiculum?
-Major source of hippocampal efferent projections
What is the parahippocampal region?
- Rhinal (entorhinal and perirhinal) cortex
- Pre- and parasubicular cortex
- Parahippocampal cortex
Describe the entorhinal cortex.
- The final and common pathway to the hippocampus
- Receives afferents from the perirhinal cortex and the parahippocampal gyrus, which gets projections from association cortex
- Provided with indirect access to information processed in the cortex
What is the ventral temporal lobe memory stream?
Unimodal (primary visual) cortical areas–>perhirhinal cortex–>lateral entorhinal cortex–> HC CA1 and CA3
What is the dorsal temporal lobe memory stream?
Parietal and frontal association areas–>parahippocampal cortex–>medial entorhinal cortex–> HC CA1 and CA3
What are the three main subcortical projections from the hippocampus?
1) CA1, CA3, & subiculum–>precommissural fornix–>lateral spetal nucleus
2) Subicual projections–>postcommissural fornix–>anterior nucleus of the thalamus or mammillary bodies
3) Hippocampus–>amygdala, nucleus accumbens, or other BF regions & ventromedial hypothalamus
What is Papez’s Circuit?
hippocampal–>postcommissural fornix–>mamillary body
-explains how the hypothalamus and cortex coordinate emotion-cognition interaction
What is the medial limbic circuit?
Hippocampus–>mamillary bodies (via fornix)–>anterior thalamus (via mamillothalamic tract)–>cingulate gyrus–>hippocampus
What is the lateral limbic circuit?
Amygdala–>dorsomedial nucleus of the thalamus (via the ventral amygdalofugal pathway )–>orbitofrontal cortex–>uncinate fasiculus–>amygdala
What are the two main parts of the amygdala?
- Anterior to the hippocampus
- Two main parts:
(1) large basolateral group of nuclei: connect to limbic systems, association cortex, and dorsomedial thalamus
(2) smaller corticomedial segment: extensive connections with BF, hypothalamaus, and brainstem - Derived from paleocortex
- Responsible for emotional aspects of cognition
Who was H.M.?
- Scoville and Milner (1957)
- Posterior resections involving the hippocampus and parahippocampal gyrus produced amnesia that was severe
What is the two-systems theory of amnesia?
-Amnesia occurs when both the lateral and medial limbic circuits are damaged
Lesions restricted to either pathway alone cause less severe memory disturbance
What occurs when there are anterior and posterior medial thalamic lesions?
Causes severe amnesia; if only one is affected there is little memory disturbance
What occurs with collateral damage to the perirhinal cortex?
- Responsible for memory deficits after amygdala lesions
- Damage to the perirhinal and parahippocampal cortices produces amnesia equivalent to that of the two systems theory of amnesia, even when the hippocampus and amygdala are spared
What is the thalamus?
-Important sensory relay nucleus
Critical functions in higher cognitive processes including alertness, activation, and memory
-Comprised of multiple nuclear groups
-Includes myelinated fiber tracks called the internal medullary lamina
What is the internal medullary lamina?
- Separates the nuclear groups of the thalamus into ventral-dorsal and anterior-posterior planes
- Includes memory relevant fibers of the mamilothalamic tracts (travles to the anterior thalamus) and ventral amygdofugal pathways (travels to the dorsomedial thalamus)
What is thalamic amnesia?
-Occurs due to disruption of both the IML and mamillothalamc tracks
Where do the midline thalamic nuclei connect and what disease are they damaged in?
- Connect with the hippocampus
- Damaged in patients with Wernicke-Korsokoff disease
What is the basal forebrain and what type of deficits are caused by damage here?
What neurotransmitter input occurs in the basal forebrain?
- Damage causes memory loss with confabulation
- At the junction of the diencephalon and cerebral hemispheres
- Consists of septal area, diagonal band of Broca, nucleus accumbens speti, olfactory tubercle, substantia innominata, bed nucleus of the stria terminalis, and preoptic area
- Major source of cholindergic input
Why does memory loss occur from aneurysms of the ACoA?
- Some patients develop memory loss due to damage to cholinergic neurons in the BF
- These cholinergic neurons project to the medial and lateral limbic circuits
What is the dominant language areas in right and left handed individuals?
- Left hemisphere is dominant for language in 95% or more of R handed individuals
- Left hemisphere is dominant in 60-70 % of left-handed individuals
What is the sylvian fissure?
- Separates the temporal and frontal lobes
- Langauge areas (Broca’s and Wernicke’s) are adjacent to this (e.g., perisylvian aphasias)
What areas are important for phonological sequencing?
-Wernicke’s area and Brodmann areas 37, 39, and 40
What areas are important for the articulation of speech sounds?
-Face area of primary motor cortex and Broca’s area
What is the arcuate fasiculus and what is it’s function?
- Large subcortical white matter pathway connecting Wernicle’s and Broca’s area
- Important for repetition of language
What is Broca’s aphasia?
- Symptom: poor speech production, sparse halting speech, missing function words, syntactic deficits
- Deficit: Impaired speech planning & production
- Lesion location: Posterior aspect of 3rd frontal convolution
What is Wernicke’s aphasia?
Symptom: Poor comprehension, fluent speech, paraphasia, poor repetition and naming
- Deficit: impaired representation of the sound structure of words
- Lesion location: Posterior half of the superior temporal gyrus
What is Anomic aphasia?
-Symptom: poor single word production, repetition and comprehension are intact
-Deficit: Impaired storage/access to lexicon
Lesion location: Inferior parietal lobe or connections with perisylvian language areas
What is transcortical motor aphasia?
- Symptom: Disturbed spontaneous speech similar to Broca’s but relatively persevered repetition and comprehension
- Deficit: Disconnection between conceptual words/sentence representations in perisylvian region and motor speech areas
- Lesion location: Deep WM tracks connecting BA to parietal lobe; caused by anterior watershed infarcts
What is transcortical sensory aphasia?
- Symptom: disturbance in word comprehension with relatively intact repetition
- Deficit: disturbed activation of word meanings despite normal recognition of auditorily presented words
- Lesion location: WM tracks connecting parietal and temporal lobe; caused by posterior watershed infarcts
What is conduction aphasia?
- Symptom: disturbance of repetition and spontaneous speech; phonemic paraphasias
- Deficit: Disconnection btw sound patterns and speech production
- Lesion location: arcuate fasiculus
What is the function of Broca’s area?
- Articulation of speech sounds and production of words and sentences
- Connects with other frontal lobe regions
- Processes syntax and grammatical structure of language
What is the function of Wernicke’s area?
- Enables phonological sequences to be identified and comprehended as words
- Connects with supramarginal and angular gyri in parietal lobe
- Language comprehension and writing
What areas are necessary for the recognition of words forms (reading)?
- Connections with visual areas in inferior temporal lobe with language areas
- Results in grapheme-phoneme conversions
What is the function of the non-dominant hemisphere in language?
- Important for prosodic information to communicate the emotional aspects of speech
- Collosal connections enable this
What is vebral-visual disconnection syndrome?
- Results from large left PCA strokes
- Damaged areas: L visual cortex & splenium of corpus collosum (affects interhemispheric crossing fibers)
- Causes: Disconnection btw info presented in R hemisphere (L visual field) and L language areas
- Symptoms: R homonymous hemianopia, alexia without agraphia, color agnosia, and optic aphasia
What is pure word deafness and what is it’s cause?
- Pt can not understand language but can identify nonverbal sounds
- Cause: WM disconnection of fibers from L and R auditory receptive areas
What is the main purpose of the frontal regions in cognition? What networks are the implicated in?
- Critical to executive functions
- Phylogenetically the youngest regions of the brain
- Last to fully develop
- Participate in cortico-cortico networks and subcortical networks involving the thalamus (especially the DLFPC)
What are frontal cortico-cortico networks and their main functions?
- Interact w/ parietal lobe and temporal lobe
- Involved in attention, proprioception, and visuomotor interaction (w/ parietal lobe)
- Involved in memory and emotional systems (w/ temporal lobe)
What are frontal- subcortical interactions and their main functions?
- Involved in behavior activation and selection
- “Selective engagement”
- Cortico-striatal-pallidal-thalamo-cortical loop
What is the cortico-striatal-pallidal-thalamo-cortical loop?
- Cortex–>striatum (caudate & putamen–>globus pallidus–>thalamus–>cortex
- engages a cortical region needed for task performance or inhibiting another region whose function would interfere with processing
Describe the orbitofrontal loop.
- Cortical input: lateral orbitofrontal, temporal cortex, & anterior cingulate
- Striatal input: ventromedial caudate
- Output nucleus: GPi, SNr
- Thalamic target: MD, VA
- Cortical target: Orbitofrontal cortex
- Function: Response-reward learning
Describe the anterior cingulate/limbic loop.
- Cortical input: Temporal cortex, hippocampus, amygdala
- Striatal input: nucleus accumbens, ventral striatum
- Output nucleus: Ventral pallidium, GPi, SNr
- Thalamic target: MD, VA
- Cortical target: anterior cingulate & orbitofrontal cortex
- Function: Emotion regulation
Describe teh dorsolateral prefrontal loop.
- Cortical input: Posterior parietal, premotor
- Striatal input: Caudate head
- Output nucleus: GPi, SNr
- Thalamic target: VA, MD
- Cortical target: Prefrontal cortex
- Function: Executive functions
Describe the oculomotor loop.
- Cortical input: Posterior parietal, prefrontal
- Striatal input: Caudate body
- Output nucleus: GPi, SNr
- Thalamic target: VA, MD
- Cortical target: frontal eye fields
- Function: eye movement subserving cognition
Describe the motor loop.
- Cortical input: somatosensory motor, premotor
- Striatal input: putamen
- Output nucleus: GPi, SNr
- Thalamic target: VL, VA
- Cortical target: SMA, premotor, primary motor
- Function: motor control
What is “top-down” attention and what system does it utilize?
- Requires interaction with frontal lobe regions involved in volition and prioritizing behaviors
- Utilizes the dorsal frontoparietal system
- Parietal lobe and frontal lobe info are transmitted to colliculi, pulvinar, and frontal eye fields
What are the 3 interconnected systems for attention (Posner & Rothbart, 2007)?
1) Orienting to stimuli
2) Alerting
3) Executive aspects of attention
Describe alerting attention.
- Sensitivity to incoming stimuli
- Modulated by norepinephrine
- Depends on ascending sensory inputs from the thalamus
Describe orienting attention.
-Tuning of perceptual systems to incoming stimuli
-Dependent on acetylcholine
Involves superior colliculus, pulvinar thalamic nucleus, posterior tempoparietal cortex, and frontal eye fields
Describe executive attention.
- Monitoring and resolving conflicts among thoughts, feelings, & behaviors
- Dependent on dopamine
- Involves the anterior cingulate cortex and DLPFC
What is “bottom up” attention and what system does it utilize?
- Attending to salient environmental stimuli
- Utilizes the ventral frontoparietal system
- Sensory signals arrive in frontal and parietal cortices after being prepossessed by superior colliculs and pulvinar
What are the two main systems in frontal working memory?
- Dorsal (spatial) - ventral (object) distinction exists in frontal working memory systems
- Dorsal PFC: codes spatial information
- Ventral PFC: active during object working memory tasks
Acetylcholine
pontomesencephalic origin
- Projection: intralaminar nucleus of thalamus
- Role: indirect excitation of thalamocortical projection
- Cognitive relevance: attention, memory, regulation of thalamic output
Acetylcholine
basal forebrain origin
- Projection: widespread cortical & hippocampus
- Role: excitatory/facilitation
- Cognitive relevance: attention, learning, and mem
Norepinephrine/noradrenaline
locus coeruleus origin
- Projection: Widespread cortical
- Role: excitatory/facilitation
- Cognitive relevance: attention shifting & arousal
Norepinephrine/noradrenaline
lateral tegmental area origin
- Projection: widespread cortical
- Role: excitatory/facilitation
- Cognitive relevance: mood & sleep-wake cycle
Serotonin
rostral raphe origin
- Projection: forebrain (thalamus, basal ganglia, cortex)
- Role: postsynaptic inhibition
- Cognitive relevance: mood & arousal
Serotonin
dorsal raphe origin
- Projection: cerebellum, medulla, spinal cord
- Role: postsynaptic inhibition
- Cognitive relevance: pain, respiration, temperature, motor control
Dopamine
mesostriatal/SNpc origin
- Projection: striatum
- Role: mixed
- Cognitive relevance: motor regulation & thalamic gating
- This is the pathway implicated in Parkinson’s disease
Dopamine
mesolimbic/VTA origin
- Projection: medial temporal lobe, amygdala, cingulate gryus, nucleus accumbens
- Role: mixed
- Cognitive relevance: memory & reward systems
- Implicated in addictive behaviors & overactivity may result in + schizophrenia symptoms
Dopamine
mesocortical/VTA origin
- Projections: cortical/frontal lobe
- Role: mixed
- Cognitive relevance: executive function, working memory, “top-down” attention, motor initiation
- Dysfunction can produce negative symptoms of schizophrenia
Dopamine
tubero-infundibular/hypothalamus origin
- Projections: pituitary gland
- Role:excitation/facilitation
- Cognitive relevance: lactation, menstruation, sexual behavior
GABA
- Origins & projections: widely distributed
- Role: inhibitory
- Cognitive relevance: broad neuromodulatory functions
- Many anti-anxiety meds enhance GABA-ergic neurotransmission
Glutamate
- Origins & projections: widely distributed
- Role: post-synaptic excitation
- Cognitive relevance: broad excitatory functions
- Implicated in long-term potentiation and synaptic plasticity
- Excess glutamate can lead to excitotoxicity
What are muscarinic receptors?
- type of acetylcholine receptors
- mediate the main cognitive effects attributed to cholinergic pathways
- effects on attention, learning, and short-term memory
What are nicotinic receptors?
- type of acetylcholine receptors
- trigger rapid neural and neuromuscular transmission
What is akinetic mutism and it’s cause?
- Results from bilateral medial frontal lobe injury
- Patient does not move or speak but is aware of ongoing events
What does anatomico-clinical correlation mean?
Establishing direct associations between anatomic damage to the brain and sensory, motor, emotional, or cognitive impairments
What is excitotoxicity and what neurotrasmitter is often implicated in this?
- Nerve cells are damaged or destroyed by excessive stimulation by neurotransmitters (like glutamte)
- Key factor in CNS response to spinal cord injury, traumatic brain injury, and neurodegenerative injury
What is neurogenesis?
- Birth and proliferation of new neurons, most active during pre- and perinatal development
- Continues into adulthood in the dentate gyrus of the hippocampus
What is neuroplasticity/synaptic plasticity?
- Changes in neural pathways and synapses due to changes in behavior, environment, or neurochemical processes
- Critical for normal development and recovery from brain damage
What is the difference between unimodal and polymodal cortex?
- Unimodal: cortex devoted to processing information within a specific sensory modality
- Polymodal: cortex that integrates information from multiple modalities, enabling more complex modes of thought
What is one major somatosensory pathway?
Dorsal column/medial lemniscus
Rapidly conducting, highly localized
Fine tactile sensation, vibration, proprioception
Gracile -infor from legs and trunk
Cuneate - from upper extremities
Primary afferent neurons - dorsal medulla - decussate and form medial lemniscus - thalamus VPL (VPM for facial sensations from trigeminal CN) -somatosensory ctx (level VI)
What is the second major somatosensory pathway?
Anterolateral
Spinothalamic, spinomesenthalamic, spinoreticular
Pain, temperature, and “crude” touch
Projections from sensory organis in joints, muscles, organs, and skin -decussate at entry to spintal cord - VPL - some terminate in BG, midrain, thalamus - some project to SS ctx
Face - spinal trigeminal tract, VPM, primary SS ctx
What are four descending/motor pathways?
Corticospinal (or corticobulbarspinal) Rubrospinal Reticulospinal Vestibulospinal Name suggests origin of cell bodies
What is corticospinal tract?
Motor output to limbs (corticospinal) and head (corticobulbar)
Primary motor ctx (+ supplemental motor and posterior parietal ctx) - posterior limb int capsule
CB terminate in red nucleus and CN motor nuclei
CS - 90% cross at pyramidal decussation, become lateral corticospinal tract
10% continue uncrossed as anterior CS tract, cross midline at level of termination on SC interneurons
What is rubrospinal tract?
Motor output to large muscles in upper extremeties
Red nucleus axons - cross immediately after leaving RN - descend through brainstem - pathway just ventral to corticospinal tract
What is reticulospinal tract?
Motor output for extensor and flexor muscles
Pontine and medullary divisions
Pontine - descends in the medial cord, fasciliates extensor motor neurons, inhibits flexor motor neurons of the limbs
Medullary division - descends in the anterolateral column, inhibits extensor, facilitates flexor motor neurons
What is vestibulospinal tract?
Vestibular function
Four subdivisions originating from superior, lateral, medial, and inferior vestibular nuclei, all receive afferent connections from the vestibular nerve
Lateral and medial - descending motor tracts
Medial - to cervical and high thoracic levels, muscles of head and neck
Stable eye platform
Lateral - descends to all levels of spine ipsilaterally
Regulates posture and balance
Injuries result in SC syndromes, typically do not affect NP function
Complete SC transaction
Loss of somatosensory and motor function below the level of injury
At/above C3 - loss of diaphragm function
Central cord syndrome
Hyperextension injuries resulting in hemorrhage, edema, or ischemic to central SC portion
Greater loss of upper vs lower limb
Anterior cord syndrome
Lesions interrupting anterior aspect of cord
Loss of pain and tempt sensation before injury
Fine touch and proprioception carried by posterior fibers, intact
Tabes dorsalie
Degeneration of posterior column due to tertiary syphilis, also in MS
Loss of touch and proprioception below the lesion site
If unilateral injury - ipisilaterally
What are sources of anterior and posterior circulatory system to the brain?
Carotid and vertebral arteries (join to form single basilar artery)
What are arteries originating from ICA?
OPAAM Opthalmic Posterior communicating (PCoA) Anterior choroidal Anterior cerebral (ACA) Middle cerebral (MCA)
What are branches of vertebral artery?
Posterior spinal
Anterior spinal
Posterior inferior cerebellar (PICA)
Blood supply to brainstem and cerebellum
What are branches of basilar artery?
Anterior inferior cerebellar (AICA) - ventral cereb and caudal pons Superior cerebellar (SCA) - remaining cereb, pons, and caudal midbrain Poster cerebral (PCA) - MTL and Occ L, also STN, pos thal, hypothal, and splenium of CC
What it Circle of Willis
Ring of blood vessels formed by major branches of ICA and BA surrounding optic chiasm and pituitary stalk
Allows collateral blood flow to the post and ant cerebrovascular systems
Substantial variability, complete CW in 21-52%
PCoAs connect PCAs to anterior circulation
ACoA connects the R and L ACAs
Venous system
Network of veins and sinuses to carry away deoxy blood to heart
Sinuses drain midsagitally (sup saggital sinus) and laterally (transverse)
Transverse sinuses to sigmoid sinus to jugular vein
Inf saggital sinus drains mesial structures
Sup saggital sinus - great vein if Galen - BA and thalamus
