Lateral Corticospinal Tract (LCSp)

Carries: ipsilateral somatic motor axons (descending)

Range: decPy (medulla) --> sacral cord

Cell bodies: pre-central gyrus

Synapse at: ventral horn of spinal level

Lesion -->: ipsilateral spastic paralysis or paresis below level

See also: Decussation of Pyramids, Pyramidal tract, Corticospinal Tract

Dorsal Column System (FGr, FCu)

Carries: ipsilateral proprioception, 2pd, vibratory sense (ascending) (type II fibers)

              fasciculus gracilis: below T6

              fasciculus cuneatus: above T6

              (higher spinal levels more lateral)

Range: in sacral cord --> NuGr and NuCu in caudal medulla

Cell bodies: dorsal root ganglia, level-down

Synapse at: nucleus cuneatus / gracilis, then joins medial lemniscus (ML) via interal arcuate fibers (ALF)

Lesion -->: ipsilateral loss of sterognosis, graphesthesia; reduced vibratory, 2pd, proprioception

Anterolateral System (ALS)

aka: spinothalamic tract (part of it, at least)

Carries: contralateral pain, temp, crude touch

Range: sacral cord --> thalamus

Cell bodies: ipsilateral dorsal horn at spinal level. Decussates in VWCom at level.

Synapse at: medullary and mesencephalic reticular formations, thalamus

Lesion -->: contralateral analgesia below level

(VWCom lesion --> bilateral analgesia)

Dorsal Spinocerebellar Tract (DSCT)

Carries: ipsilateral proprioception (ascending) from large fibers in golgi tendon organs, muscle spindles.

Range: L3 (below, comes up in FGr) --> ICP (in medulla)

Cell bodies in: Dorsal nucleus of Clarke (L3 - C8) in dorsal horn at level.  (Above C8 in FCu)

Synapse at: two copies of info:

-Nucleus Z (then decussates in ML)

-cerebellum (remains ipsilateral)

** above C8 synapse at lateral (or accessory) cuneate nucleus near nucleus Z, and from there, send to MLS-->cortex contralateral, cerebellum ipsilateral

Lesion -->: ataxia below level

Anterior Corticospinal Tract (ACSp)

carries: ipsilateral somatic motor for axial musculature

*is a remnant of pyramidal tracts, and thus part of the CST.  Can control respiration and balance even when LCS lesioned.

Medial Longitudinal Fasciculus (MLF)

(sometimes aka "medial vestibulospinal" in cord)

Carries: ipsilateral motor fibers from vestibular system --> eye and cervical musculature

Range: oculomotor nucleus (midbrain) --> cervical cord

Cell bodies: vestibular nuclei

Synapse at: oculomotor, abducens, trochlear nuclei; ipsilateral ventral horn of cervical cord

Lesion -->: "internuclear ophthalmoplegia" (e.g. contralateral medial rectus palsy)

**no isolated lesions below abducens nuclei

Spinal Trigeminal Nucleus (SpTNu) & Tract (SpTT)

aka: medullary dorsal horn (hint about function)

Carries: ipsilateral afferents: pain, temp, crude touch from CN V fibers.

Range: caudal medulla --> pons

Cell bodies: SpTNu gets info from CN V cells in ipsilateral trigeminal ganglia

Synapse at: cross midline at level to form VTTr in pons, so...

Lesions --> CONTRAlateral analgesia!

** mapped like dermatomes: rostral = nose, lips; caudal = posterior face

Nucleus Gracilis (NuGr) and Cuneatus (NuCu)

Info: vibratory, 2pd, crude touch

Range: medulla only

Get info from: FGr, FCu

Send info to: cross midline via internal arcuate fibers (IAF) to form medial lemniscus (ML) and eventualy synapse at ventroposterior lateral nuclei (VPL) in thalamus.

Accessory Nucleus (AccNu)

contains: cell bodies for CN XI

range: very caudal medulla

gets info from: contralateral cortex for traps, ipsilateral (mostly) cortex for SCM.

lesion -->: flaccid paralysis of ipsilateral traps, SCM

**suprasegmental lesions may present as ipsilateral SCM and contralateral traps

Pyramidal tract (Py) and decussation (decPy)

Carries: contralateral somatic motor (descending) -- continuous with LCSp

range: throughout the medulla (decPy caudal)

cell bodies: pre-central gyrus in cortex

synapse at: ventral horn motor nuclei

lesion -->: contralateral hemiparesis/paralysis

Medullary Reticular Formation (MRetF)

function: cell bodies and fibers for autonomic regulation

range: throughout medulla (continuous w/ PRetF)

lesion-->: dysautonomia (heart, lungs)

descending autonomic fibers-->ipsilateral Horner's syndrome

Medial Lemniscus (ML)

Carries: contralateral vibratory, 2pd, proprioception

Range: medulla and pons

Cell bodies: dorsal column nuclei (NuGr and NuCu) AND Nucleus Z

Synapse at: ventroposterior lateral nuclei (VPL) in thalmus

Lesion-->: (like combined FGr/Cu and DSCT) contralateral loss of vibr, 2pd, proprioception

**ventral = Lower Extr.; dorsal = Upper Extr.

Nucleus Ambiguous (NuAm)

function: motor for CN IX, X

range: medulla from decML to PONu (like SolNu)

get info from: ???

lesion -->:

unilateral --> hoarseness, dysphonia (nasal twang), dysphagia, dyspnea, diminished gag, hiccups

bilateral --> palatine droop, severe dysphagia and dyspnea

Solitary Tract (SolTr) and Nucleus (SolNu)

function: relays lots of visceral sensory information up to rostral brainstem and cortex.  Related to chem. trigger zone & vomit center.

range: medulla from decML to PONu (like NuAm)

gets input from: via SolTr, gets:

visceral sensory (touch and taste) from VII, IX, X (incl. heart, GI)

Dorsal Motor Nucleus of the Vagus (DMNu)

function: pre-ganglionic, parasypmathetic for vagus

range: throughout medulla

gets info from: SolNu, hypothalamus

synapses at: parasympathetic ganglia in throax, abdomen

lesion -->: tachycardia, stomach dilation (lack of parasympathic outflow)

Hypoglossal Nucleus (HyNu)

function: motor neurons for CN XII

range: caudal medulla

gets info from: bilateral corticonuclear fibers

lesion -->: slurred speach, tongue protrudes toward lesion, possible atrophy, fasciculations

Lateral Cuneate Nucleus (LCNu)

function: ipsilateral proprioception from muscle spindles (equiv. of Dorsal Nu of Clarke, above C8)

range: small part of medulla, embedded in FCu

gets info from: dorsal columns above C8

synapse at: ipsilateral cerebellum via ICP, & contralateral cerebral cortex

lesion -->: ipsilateral diminished proprioception

Prinicpal Inferior Olivary Nucleus (PONu)

function: part of cerebellar motor control and training

gets info from: ipsilateral red nucleus, contralateral DC nuclei, bilateral cerebelleum

synapse at: "climbing fibers" go to Purkinje Cells in contralateral cerebellum

Inferior Cerebellar Peduncle (ICP)

carries: proprioceptive info from body (DSCT, principle inferior olivary nuclei PONu, LCNu)

synapse at: anterior lobe of cerebellum

lesion-->: ipsilateral ataxia (clumsiness, leaning, veering)

Vestibular Nuclei (MVNu, LVNu, SVNu)

function: coordinate head/neck/eye movement

range: small part of rostral medulla

gets info from: ipsilateral vestibular apparatus

synapse at: via MLF --> ipsilat. spinal cord, contralat AbdNu, occulomotor nucleus

lesion -->: nystagmus, gaze palsies

Cochlear Nucleus (CoNu)

function: part of the auditory pathway

location: lateral to the ICP in the rostral medulla

info from: auditory nerve

synapse at: bilateral to SONu, contralateral inferior colliculus

lesion-->: ipsilateral sensorineural deafness

Inferior Salivatory Nucleus (ISNu)

function: preganglionic parasympathetic to otic ganglion

lesion -->: no salivary release from ipsilateral parotid gland.

Vestibulocochlear Nerve Root (VCNr)

position: ventral to MCP

lesion -->: unilateral deafness, often w/tinnitus

"peripheral vestibular syndrome": nystagmus, vertigo, limb drift, Rhomberg.  Shorter-lived than central vestibular syndrome, severe paroxsysmal vertigo, signs lateralize more (e.g. slow-drift of nystagmus toward lesion).

Middle Cerebellar Peduncle (MCP)

carries: made of transverse pontine fibers as part of the cortico-ponto-cerebellar pathway.

from: contralateral pontine nuclei

synapse at: ipsilateral cerebellum

lesion -->: ipsilateral limb ataxia

Abducens Nucleus (AbNu)

input: bilateral MVNu, ipsilateral paramedian pontine reticular formation

output: CN VI, and --> MLF --> contralateral oculomotor nucleus (for lateral gaze)

Facial Nucleus (FacNu) and radiations (FacNr)

input: motor cortex--lower half of face contralateral only, upper half bilateral.

**emotional control of FacNu is by different pathway!

Pontine Reticular Formation (PRetF)

lesion-->: disturbances in REM sleep

Superior Salivary Nucleus (SSNu)

*extension of DMNu = hint as to position/function!

function: preganglionic parasympathetics to submandibular and pterygopalatine ganglia

lesion: diminished salivation, lacrimation (ipsilateral)

Mesencephalic Trigeminal Nucleus (MesNu)

and Tract (MesTr)

lesion-->: diminished jaw-jerk reflex

Pontine Nuclei (PonNu)

lesion-->: contralateral limb ataxia (often masked by hemiparesis due to damaged CST nearby)

Pontocerebellar Fibers (PCeF)

a.k.a "transverse pontine fibers"

decussation of connections between pontine nuclei and MCP

Trigeminar Motor Nucleus (TriMoNu)

lesion-->: ipsilateral weakness in mastication muscles, deviation of jaw to weakened side.  Bilateral--> jaw-jerk hyper-reflexia

Ventral Trigeminothalamic Tract (VTTr)

from: SpTNu decussates as it branches off

to: ventroposterior medial thalamic nucleus

Chief Sensory Nucleus of the Trigeminal Nerve (CSNu)

function: complements dorsal column nuclei in that it carries cutaneous touch (2pv for face)

lesion-->: loss of above, and possibly analgesia

Vestibulocerebellum

function: uses info from otolithic organ (gravity) to control posture, balance, eye movements

input:

-ipsilateral vestibular apparatus (nodulus)

-visuomotor nuclei (flocculus)

output:

--> vestibular nuclei --> VST & MLF --> axial muscles and extraoccular eye muscles

Spinocerebellum - median zone

where: vermis and anterior lobe

input: neck and trunk muscles, vestibular, auditory, visual systems

output: --> fastigial nucleus --> vestibulospinal and rubrospinal tracts --> axial muscles

Spinocerebellum - intermediate zone

input: spinocerebellar tracts

output: --> interpositus nuclei --> red nucleus and ventrolateral thalamic nucleus --> rubrospinal and corticospinal tracts (coordinates limb musculature)

Pontocerebellum

where: lateral hemispheres of posterior lobe

input: pontine nuclei <-- ipsilat cerebral cortex (cortico-ponto-cerebellar pathway)

output: --> dentate nucleus --> contralateral thalamus --> motor cortex --> distal limbs

Cerebellar Cortex

monolayer of Purkinje cells: huge cells, dendrites extent way out in transverse plane, receive axons from granule cells and contralateral PONu

granule cells: deep to purkinje cells, input from vestibular, spinal, pontine nuclei.  Output to purkinje cells.

Dorsal Longitudinal Fasciculus (DLF)

carries: fibers for autonomic regulation

range: hypothalamus to caudal medulla

Layers of Cerebral Cortex

Layer I - III: Associational connections

Layer IV: Afferent connections

Layer V: Efferent (going out of cortex) connections

Layer VI:  Associational connections (again)

Superior Cerebellar Peduncles (SCP)

function: major cerebellar output pathway

*decussates near thalamus

lesion-->: like a cerebellar hemispherectomy

caudal --> ipsilateral limb ataxia

rostral --> contralateral limb ataxia

Lateral Lemniscus (LL) and nuclei (LLNu)

from: cochlear nucleus, inferior olive

to: inferior colliculus

lesion-->: contralateral diminished hearing

around base of inf. colliculus--> acoustic hallucinations!

Occulomotor Nucleus (OcNu)

function: vertical eye movements (extraocular eye muscles), levator palpebrae

input from:

-MLF (vestibular nuclei, abducens nuclei)

-paramedian pontine reticular formation (horizontal gaze center)

-RINMLF & interstitial nucleus of Cajal (vertical gaze center)

lesion-->: "down and out" gaze, pupil fixed, dilated and unresponsive, ptosis

Substancia Nigria (SN)

function: produce dopamine

*Parkinson's = degeneration of SN past 80%

Cerebral Peduncle/Crus (CC)

contains (ventral to dorsal order): frontopontine, corticonuclear, corticospinal, corticopontine (temporo-, occipito-, parieto-)

lesion-->: contralateral hemiparesis (distal > proximal), contralateral lower quadrant facial paralysis,

Pretectal Nuclei (PreTec)

function: pupillary light reflex

info from: contralateral visual hemisphere (bilateral retinae)

output to: both Edinger-Westphal nuclei (contralateral via posterior commisure), parasympathetics then leave via CNIII to synapse on ciliary ganglion

Rostral Interstitial Nucleus of the Median Longitudinal Fasciculus (RINMLF)

controls vertical gaze

lesion-->: ??

Red Nucleus (RuNu)

input from: cortex, dentate nucleus (cerebellum)

output to: RuSp (lateral motor), inferior olive-->cerebellum (feedback circuit necessary for learning new motor patterns)

Posterior Commissure (PoCom)

decussation of fibers from pretectal area, crossing to innervate the contralateral Edinger-Westphal nucleus.

lesion-->: conjugate upward gaze palsy

Dentothalamic (Cerebellothalamic) Tract(s) (CThT)

=SCP between decussation and thalamus

(dentothalamic --> ventrolateral thalamic nuc.)

"Paramedian Syndrome"

arteries: paramedian branches of basilar, post. cerebral

damages: OcNu, OcNr, RINMLF, decSCP, (maybe into thalamus)

presentation:(think it through...)

- occulomotor (CN III) palsy

- vertical gaze palsy

- limb ataxia

- dysmetria

"Weber's Syndrome"

arteries: anterolateral branches of basilar, post. cerebral, etc.

affects: cerebral peduncles, OcNr roots, SN

presentation: (think about it...)

- occulomotor palsy

- contralateral spastic paralysis

- all sensory intact, often

- maybe assoc. akinesia, tremor, central facial palsy

"Benedict's Syndrome"

arteries: distal parts of paramedian branches of basilar, post cerebral.

affects: OcNr roots, RuNu, Dentothalamic fibers, SN

presentation: (think...)

- ipsilateral occulomotor palsy

- contralateral motor hyper-/a-kinesia

Pulvinar

-related to posterior parietal association cortex

-reciprocal connections w/ parieto/occipital/temporal junction area

lesion-->:

non-dominant: topo memory disturb., visual neglect

dominant: aphasia similar to mixed transcortical

Pineal Body/Gland

-produces melatonin to act as circadian clock

-NOT directly connected to CNS by fiber tracts!!

-gets sympathetic autonomic innervation from: hypothalamus-->T-spine-->cervical ganglion to indicate the presence/absence of light

- tumor --> Parinaud's syndrome

Lateral Geniculate Nucleus (LGNu)

- contains representation of contralateral visual space

input from: optic tract

output to: visual cortex (directly?)

lesion-->: homonymous hemianopsia

Medial Geniculate Nucleus (MGNu)

input from: inferior colliculus

output to: cerebral cortex, (and limbic system)

lesion-->: diminished (not absent) hearing

Optic Radiations (OpRad)

from: lateral geniculate

to: visual cortex

Meyer's Loop = curved pathway, spread out:

-superior field -> temporal lobe

-inferior field -> deep to parietal lobe

lesion-->: contralateral quadrantanopsia

Ventroposterior thalamic nuclei (VPL, VPM)

major somatic sensory nuclei

input from:

   lateral part: medial lemniscus (incl. ALS)

   medial part: VTTTr

output to: post-central gyrus

lesion-->: contralateral face and body somatic sensory loss

Dorsomedial thalamic nuclei (DMNu)

input from: prefrontal cortex, amygdala, olfactory cortex, substantia nigra

output to: prefrontal cortex

function: probably integrates somatic sensory information, memory processing, cognition, maintains consciousness.

lesion-->: verbal/topographic memory disturbance.  Familial degeneration: dysautonomia, insomnia

Lateral thalamic nuclei (LP, LD, pulvinar)

input from:

LP: visual cortex, superior colliculus

LD: hippocampus, pretectum, lat. geniculate

output to: parieto-occipital lobes, cingulate, parahypocampal

Internal Medullary Lamina (IML)

function: transmission of pain, maintenance of arousal

input from: ALS, midbrain RetF

Ventroateral thalamic nuclei (VL)

input from:

- cerebello-thalamic fibers (from contralateral dentate nucleus),

- globus pallidus (via lenticular fasciculus)

output to: motor area

lesion-->: hypotonia, diminished emotional expression, transitory neglect

Lenticular Fasciculus (LenFas)

connects globus pallidus --> VL thalamic nucleus

lesion-->: contralateral choreiform or athetotic movements

Mammillary Bodies (MB)

function: part of limbic circuit (memory, learning)

input: hippocampus and septal area --> fornix -->

output: anterior thalamic nuclei --> cingulate

Mammillothalamic Tract (MTTr)

- connects mammillary bodies to anterior thalamic nucleus

- carries memory-forming information

lesion-->: spatial memory impairment (frequently seen in alcoholics).

Posterior Hypothalamus (PHyTh)

output to: autonomic brainstem nuclei

function: sympathetic regulation

lesion-->: hypothermia, Horner's, apathy, hypersomnia, coma

Lateral Hypothalamus (LHyTh)

function: appetite stimulation

lesion-->: loss of apetite, adipsia, apathy

Medial Hypothalamus (MHyTh)

function: pituitary control, satiety

lesion-->: diabetes insipidus, hyperphagia, obesity, inappropriate ADH release, dwarfism, behavioral dysfunctions (rage, amnesia)

Anterior Hypothalamus (AHyTh)

function: control of anterior pituitary gland, parasympathetic NS.  (receptors for sex hormones, set points for the control of temperature )

lesion-->: hyperthermia (cyclic w/ fever, chills), diabetes insipidus, insomnia

Ansa Lenticularis (AnLen)

part of pallidothalamic fibers

from: globus pallidus internus

around to: VA thalamic nuclei

lesion-->: see LenFas

Ventroanterior thalamic nuclei (VA)

input from: globus pallidus internus (via ansa lenticularis)

output to: pre-/supplementary motor area

function: scale intensity in motor system (complex loop)

Anterior thalamic nuclei (AN)

input from: mammillothalamic tract

output to: cingulate gyrus

function: part of limbic circuit

lesion--> confusion to time and place

Superior Colliculus (SC)

function: map of body/space---guide head, eye, upper limb in response to unexpected stimuli (e.g. saccades)

input from: visual, auditory, somatic sensory, cortex

output to: visual cortex, cervical spine, accessory optic nuclei

Inferior Colliculus (IC)

creates a map of acoustic space

from: contralateral cochlear nucleus, lateral lemniscus, bilateral superior olives

to: ipsilateral medial geniculate nuc. (thalamus), and back to cochlear, sup. olives

Prefrontal cortex

- executive functions dorsolateral part... (frontomedial is more targetted to controlling survival behaviors)

- working memory

- inhibit activity from other parts of the brain

    - utilization behavior / stimulus-bound behavior

    - supresses inappropriate actions

Premotor and Supplementary Motor Cortex

part of frontal cortex

function: contral axial and proximal limb muscles (medial motor system)

input from: ipsi VA, VL thalamic & post. parietal

output to: corticospinal, corticonuclear

Primary Motor Cortex

located on pre-central gyrus

function: distal limb muscles (lateral motor system)

input from: VL thalamus, primary somatic sensory cortex, premotor and supplementary motor cortex

output to: corticospinal fibers

Broca's Area

located within premotor cortex

function: language mechanics

lesion-->: motor aphasia (comprehension intact).  Larger lesions may move into hand representations and show agraphia as well.

Postcentral Gyrus

function: primary somatic sensory cortex

lesion-->:

-loss of 2pv, proprioception

-asterognosis

-parasthesias

-vague pain and thermal INTACT

Posterior Parietal Lobule

function:

- dominant side

    - language (see Wernicke's area)

    - single side of space for that side

- non-dominant side

    - bilateral space representation

lesion-->: fluent aphasia

Wernicke's Area

-occurs on dominant side of the brain

-puts meaning to incoming sensory data

lesion-->: fluent aphasia

(lesion to band around this area: transcortical sensory aphasia)

Visual Cortex

aka: striate cortex

located on either side of calcarine sulcus in the occipital lobe

function: map of visual space (inverted)

input from:lateral geniculate

output to:

lesion-->: unable to identify objects, but can still respond to light (autonomic response, circadian rhythm, etc.)

(lesion of visual association cortex --> Anton's syndrome: cortical blindness without the patient's acknowledgement of visual loss!)

Auditory Cortex

function: tonotopic map of auditory space

input from: medial geniculate nuclei

output to: Wernicke's area, posterior parietal, adjacent temporal cortex

lesion-->: only visible if bilateral --> "cortical deafness" (cannot hear speech, but occasionally other sounds)

Inferior temporal cortex

- posterior (or still occipital lobe??), color

- middle, use

- anterior, name

*interfaces with Wernicke's area, visual cortex

Insula Lobe

function: integrate taste, smell, visceral sensory data and influence autonomics.

input from: medial geniculate (auditory, vestibular), VP medial (gustatory, visceral), solitary Nu, olfactory bulb

lesions-->: rare... can cause gustatory hallucinations

Cingulate Gyrus

prioritizes attention to information

connections: association cortex; AN, VA, DM thalamus; part of limbic loop (see diagrams)

lesion-->: akinetic mutism, indifference to pain, apathy, incontinence, probably some memory loss?

Hippocampus

declarative memory

input from: amygdala, septal area (SA), hypothalamus, thalamus

output to: via fornix-->mamillary bodies

lesion-->

dominant side: language-related anterograde loss

non-dominant side: spatial anterograde loss

Amygdala

(forms uncus, grossly)

"fear memory"

- acts on autonomic system more than declarative

- negative reinforcement

input from: association cortex, SolNu, DMNu

output to: via Stria Terminalis --> premotor/prefrontal, DM thalamus, hypothal, others

lesion-->: Kluver-Bucy Syndrome

- visual agnosia (aka. "psychic blindness")

- oral tendencies

- hypermetamorphosis (react to even small stimuli)

- emotional change

- incr. sexuality

- incr. eating

Nucleus Accumbens

"pleasure center"

- antithesis of amydala

- positive reinforcement

*facilitation --> addiction

Fornix

part of limbic system, memory

from: hippocampus

to: mammillary bodies, septal area

Stria Terminalis (StTer)

input from: amygdala

output to: hypothalamus, thalamus

Stria Medullaris (StMed)

from: septal nuclei

to: habenular nuclei

- part of limbic system pathway from septal area to brainstem

Lamina Terminalis

anterior wall of 3rd ventricle

- brain contacts and analyzes blood here

- generates autonomic response through hypothalamus

Corpus Striatum

contains both caudate nucleus and putamen

connections: see diagrams

function:

caudate - behavior and cognitive

putamen - limb musculature

lesions-->: hyperkinesias (athetosis, chorea, dystonia)

Globus Pallidus

input from: corpus striatum

- GPi: GABA/substance P

- GPe: GABA/enkaphalin

output to:

- GPi: subthalamus (GABA)

- GPe: thalamus (GABA)

lesion-->:

- severe hypokinesia

Subthalamic Nucleus

b/w internal capsule and LenFas

input: inhibited by GPe

output: excites GPi

lesion-->: ballisms