THALAMUS Flashcards
What is the THALAMUS?
STRUCTURE
ROLE
Structure:
- Paired structure of GREY MATTER
- found on both sides of the 3rd VENTRICLE
- Connected by INTERTHALAMIC ADHESION
ROLE:
gating, prioritising and modulating information rather than only forwarding information.
“GATEKEEPER” and “INTEGRATOR”
ALL SENSORY information EXCEPT OLFACTION, is directed to the THALAMUS for PROCESSING AND PROJECTION.
Also receives INPUT for many other Areas.
greater than 75% of neurons in THALAMUS are PROJECTION NEURONS
rest are INHIBITORY
What are the THALAMIC NUCLEI?
CATEGORY? (4) AND WHAT ARE IN THEM?
- RELAY NUCLEI
- MOTOR: - VA (Ventral anterior)
- VL (Ventral Lateral)
- SENSORY:
1. VPL (ventral posterolateral)
2. VPM (ventral posteromedial)
3. MGN (medial geniculate nucleus)
4. LGN (lateral geniculate nucleus) - LIMBIC:
1. ANT (anterior nucleus)
2. LD (lateral dorsal)
- ASSOCIATION NUCLEI
- PULVINAR
- LP (lateral posterior)
- DM (lateral dorsal)
- INTRALAMINAR NUCLEI
- 1. CM (CENTROMEDIAN)
- 2. PF (parafasicular) - RETICULAR NUCLEUS
- TRN (thalamic reticular nucleus)
How TRN works in Thalamus = 5
- Sensory Information: DRIVER; specific input, information for the cortex goes to
- THALAMUS
- also goes to THALAMUS;
—–CHOLINERGIC, NORADRENERGIC, SEROTONRGIC and DOPAMINERGIC PROJECTIONS from BAINSTEM - IN THALAMUS
- TRN; THALAMIC RETICULAR NUCLEUS;
acts as the MODULATOR; regulatory input, gating, prioritising, and modulating info. - THALAMUS OUTPUT TO CORTEX
CORTEX can input and output back; as the MODULATOR; regulatory input, gating, prioritising, and modulating info.
List and Categorisation of the THALAMUS NUCLEI:
Anterior: ANT (anterior nucleus)
medial group: DM (dorsomedial)
lateral group:
1. DORSAL TIER
LD: lateral dorsal
LP: lateral posterior
PUL: pulvinar
- VENTRAL TIER
VA (ventral anterior)
VL (ventral lateral)
VP (ventral posterior)
VPL: Ventral posterior lateral and VPM: Ventral posteromedial)
intralaminar:
CM (centromedian)
PF: Parafasicular
Reticular:
TRN (thalamic reticular formation)
MG nucleus relays steps and where: 5
- COCHLEA
- Cochleat nuclei
- INFEROIR Colliculus
- MGN (median geniculate nuclei)
- Primary auditory and auditory association cortices
***MG nucleus relays auditory information to Auditory cortex.
LG nucleus relays steps and where: 5
- RETINA
……….
- OPTIC TRACT
- LGN (lateral geniculate nucleus)
- Primary visual and visual association cortices
***LG nucleus relays visual information to visual cortex
VPL nucleus relays info from the DCML pathway AND spinothalamic tracts to SOMATOSENSORY CORTEX HOW?
3 for both
- ANTERIOR TRIGEMINOTHALAMIC Trigeminal Leminiscus (upper)
- VPM
- SOMATOSENSORY CORTEX
- SPINOTHALAMIC POSTERIOR COLUMN - MEDIAL LEMNISCUS
- VPL
- SOMATOSENSORY CORTEX
VPL nucleus relays info from the DCML pathway and spinothalamic tracts to SOMATOSENSORY CORTEX.
VA/VL nuclei relay info from basal nuclei/ cerebellum to the PRIMARY motor cortex.
HOW
- 3 for both of them
- BASAL GANGLIA
back and forth with
- VA
- then to MOTOR CORTEX
- CEREBELLUM
back and forth with
- VL
- Then to MOTOR CORTEX
VA/VL nuclei relay info from basal nuclei/ cerebellum to the PRIMARY motor cortex.
Mammillary bodies pathway to the thalamus and why?
ANTERIOR NUCLEUS RELAY INFO FROM MAMMILLARY BODIES TO THE CINGULATE CORTEX (LIMBIC LOBE) via MAMMILLOTHALAMIC TRACT
- Mammillary bodies
- Anterior nucleus
- Cingulate nucleus
- Consolidation of memories
- Directing attention
Entorhinal bodies pathway to the thalamus and why?
- Entorhinal cortex
- Lateral dorsal nucleus (LD)
- CINGULATE NUCLEUS
- PARIETAL CORTEX
- Motivation and attention
Diffuse input from limbic system pathway to the thalamus and why?
- DIFFUSE INPUT FROM THE LIMBIC SYSTEM
- DORSALMEDIAL NUCLEUS (DM)
- CINGULATE CORTEX
- PREFRONTAL CORTEX
- ORBITOFRONTAL CORTEX
- INHIBIT INAPPROPRIATE BEHAVIOUR
MEDIATES EXECUTIVE FUNCTION
Blood Supply to the THALAMUS?
- POSTERIOR CEREBRAL ARTERY
- POTERIOR COMMUNICATING ARTERY
Variable supply from ANTERIOR CHORODIAL ARTERY
What are the FIRING PATTERNS of THALAMOCORTICAL NEURONS?
- TONIC FIRING
- BURST FIRING
is related to membrane potential/control of voltage-gated low threshold Ca (2+) conductance that determines response properties of relay cells
Explain Tonic Firing Pathway and best suited for.
- tonic firing of thalamic neurons is suited for a LINEAR transfer of info to the cortex
is related to membrane potential/control of voltage-gated low threshold Ca (2+) conductance that determines response properties of relay cells
PATHWAY
- driver input with sensory info from the periphery
- NO CHANGES in membrane potential of relay neuron via modulator input
- THALAMIC Relay neuron in TONIC MODE.
- LINEAR TRANSFER of driver input to the CORTEX
Explain Burst Firing and its pathway
- SEEN during Sleep to effectively block TONIC firing sending info to the cortex
- also happens when AWAKE to ALLOW NEW and CHANGING STIMULI to be DETECTED
- suited for the detection of new stimuli or changing stimuli
PATHWAY
- DRIVER INPUT with sensory info from the periphery
- CHANGES membrane potential of relay neuron
- THALAMIC relay neuron in BURST MODE
- ONLY NEW or CHANGING INFO IS RELAYED TO CORTEX
is related to membrane potential/control of voltage-gated low threshold Ca (2+) conductance that determines response properties of relay cells
UNDERSTANDING ASSOCIATION NUCLEI
Receives info? for what?
- RECEIVES input from SUBCORTICAL STRUCTURES: basal nuclei, reticular formation, brainstem nuclei and limbic system
- THALAMUS uses info from SUBCORTICAL STRUCTURES to
MODULATE the INTERACTIONS OF CORTICAL AREAS with each other —> “gating”
Thalamocortical projections relay signals integrated in the THALAMUS and MODULATED by INPUT to THALAMUS.
Association cortices vs TRANSTHALMIC CONNECTIONS VIA THE THALAMUS EXPLAIN BOTH
- Frontal, parietal, occipital, temporal = association cortices
back and forth
- Frontal, parietal, occipital, temporal = association cortices
***CONDUCTION VELOCITY OF SIGNAL BETWEEN DIFFERENT AREAS OF CORTEX IS SLOWER THAN TRANS THALAMIC CONNECTIONS
TRANSTHALAMIC CONNECTIONS
- Frontal, parietal, occipital, temporal = association cortices
- THALAMUS : GATING FUNCTIONS
- PULVINAR
- DM
(Also receives information from SUBCORTICAL STRUCTURES) - back to Frontal, parietal, occipital, temporal = association cortices
***RAPID CONDUCTION VELOCITY MAY ENHANCE TEMPORAL SUMMATION OF SIGNAL
Explain ASSOCIATION NUCLEI: PULVINAR
HIGHER ORDER VISUAL PROCESSING
THE PULVINAR AND HIGHER ORDER VISUAL PROCESSING
- VISUAL PROCESSING CORTEX OR
Frontal, parietal, occipital, temporal = association cortices - PULVINAR (BACK AND FORTH)
- Frontal, parietal, occipital, temporal = association cortices OR
VISUAL PROCESSING CORTEX
Visual salience, attention to a specific visual stimulus, visuospatial working network.
Explain ASSOCIATION NUCLEI: PULVINAR
HIGHER AUDITORY-VISUAL PROCESSING
The pulvinar and higher-order Auditory processing
- AUDITORY PROCESSING CORTEX OR
Frontal, parietal, occipital, temporal = association cortices - PULVINAR (BACK AND FORTH)
- Frontal, parietal, occipital, temporal = association cortices OR
AUDITORY PROCESSING CORTEX
Understanding auditory short-term memory
EXPLAIN ASSOCIATION NUCLEI: DORSOMEDIAL NUCLEUS
COMMUNICATION BACK TO FORTH WITH WHAT AND WHY? 5
- PREFRONTAL CORTEX: Gating information and executive function
- BASAL GANGLIA: limbic circuit: motivational and emotional aspects of motor behaviours
- LIMBIC SYSTEM STRUCTURES: Limbic circuit: motivational and emotional aspects of motor behaviours
- ENTORHINAL CORTEX: olfactory learning and odour memory; discrimination
- CRITICAL FOR GATING INFO TO AND FROM THE PREFRONTAL CORTEX = EXECUTIVE CONTROL
INTRALAMINAR NUCLEI: CENTROMEDIAN AND PARAFASICULAR
- INPUT, TO, OUTPUT ANF WHY?
INPUT:
1. CHOLINERGIC INPUT FROM THE BRAINSTEM
2. DOPAMINERGIC INPUT FROM BRAINSTEM (VTA)
TO: CM/PF
OUTPUT:
1. DIFFUSE, NONSPECIFIC CORTICAL AREAS; for arousal, awareness and vigilance
- STRIATUM: CAUDATE NUCLEUS AND PUTAMEN: for prioritising and selecting inputs to the basal ganglia
USES: CRITICAL ROLE IN AROUSAL AND IN FACILITATING AWARENESS AND VIGILANCE
FACILITATE GOAL-ORIENTED BEHAVIOUR BY PRIORITIZING AND SELECTING INFORMATION from basal nuclei
(respectively)
Understanding the thalamic reticular nucleus
DRIVER INPUT
WHERE
BACK AND FORTH?
USES
- DRIVER INPUT; info to THALAMUS: SENSORY
- THALAMUS: thalamus relays the info to CORTEX
- CORTEX sends FEEDBACK on THIS info to TRN
- TRN can INHIBIT the AREA of the THALAMUS from which the INITIAL info came; this can BLOCK FLOW FROM THALAMUS TO CORTEX
USES: CRITICAL ROLE IN SELECTIVE ATTENTION
- All neurons of the TRN are GABAergic and send inhibitory projections to THALAMUS.
