Thalamus Overview

These flashcards cover key concepts and information about the thalamus from the lecture notes, focusing on its functions, structures, and clinical implications.

What is the primary function of the thalamus in the brain?

The thalamus receives, processes, and directs information to the cerebral cortex, sorting and interpreting incoming sensory and motor information.

What two types of inputs do thalamic nuclei receive?

Thalamic nuclei receive specific inputs (drivers) and regulatory inputs (modulators) that determine whether information is forwarded to the cortex.

What is the role of relay nuclei in the thalamus?

Relay nuclei receive specific input particular to the cortical areas they connect to and decide what to send to the brain.

Name two major functions of the association nuclei.

Association nuclei modulate interactions between different parts of the cortex and are critical for higher cortical functions.

How does the thalamic reticular nucleus (TRN) function as a 'gatekeeper'?

The TRN integrates feedback from the cortex and can inhibit the thalamus to control the flow of information to the cortex.

What are the primary sensory nuclei and their respective modalities?

Ventral posterior nucleus (VPL for body sensations, VPM for face sensations), Medial Geniculate nucleus (MGN for auditory), and Lateral Geniculate nucleus (LGN for visual).

What are the consequences of thalamic syndrome?

Thalamic syndrome can lead to sensory disturbances, exaggerated reactions to sensory input, and motor symptoms such as muscle weakness or involuntary movements.

Describe the two firing patterns of thalamic neurons.

Thalamic neurons can fire in tonic mode (prolonged low-frequency) or burst mode (short bursts of high frequency followed by silence).

What are some clinical symptoms associated with thalamic damage?

Symptoms can include sensory disturbances, motor dysfunction, cognitive issues such as memory problems, and disorientation.

What role does the pulvinar nucleus play in visual processing?

The pulvinar is involved in visual salience, attention to specific visual stimuli, and visuospatial working memory.

what is a driver?

“what message is being sent?”

• Main message .

• The main input to a thalamic neuron.

What is a modulator 

A substance that influences the activity of a thalamic neuron by modifying the effects of the main input, often affecting the overall response of the neuron.

• Volume control

• It can make the thalamus more or less responsive, but it doesn’t carry new information.

Small damage within the thalamus can lead to big prbolems? T or F

True

The thalamus has complex networks that travel to and from NUCLEI? T or F

True, these nuclei are critical in processing sensory and motor information.

All thalamic nuclei have _____________ communication w/ the _______. 

bidirectional , cortext 

Most nuclie in thalamus are (> 75%) ______________ neurons , rest are inhibitory interneurons.

PROJECTION

What is a specific input driver?

Excitatory, glutaminergic - contain info must be fowarded to the cortext.

Regulatory input are also known as ?

modulators

specific inputs are also known as? 

drivers 

what is considered a regulatory input (modulator)?

Gabba. - regulate if it can be fowarded to the cortext.

Sensory nuclei

Relayed on to cortext through interal capsuel.

what is internal capsule?

The internal capsule is a bundle of white matter fibers deep inside the brain.

• It carries messages up from the thalamus to the cortex (like sensory information).

• It also carries messages down from the cortex to the brainstem and spinal cord (like motor commands).

Ventral posterior nucleus

• VPL( ventral posterior lateral) - sensory body. - think of limbs lateral

• VPM (ventral posterior medial) - sensory face.- face medial

Medial Geniculate nucleus

MGN- auditory 

Lateral geniculate nucleus 

LGN- Visual 

MODULATORY SYSTEM

FILTERS information that is relayed to the cortex. ( Awareness of a stimulis & CONSCIOUSNESS)

List the 3 Relay nuclei

• Sensory - 3types

• Motor nuclei- 2 types

• Limbic nuclei ( Anterior - LD complex & DM)

Sensory nuclei list all 3: 

Ventral posterior nucleus: body and face sensory

Medial Geniculate nucleus : auditory

Lateral geniculate nucleus : visual

Motor nuclei list both types 

VA & VL : 

input in basal ganglia, cerebellum

Association nuclei 

Pulvinar: visual and auditory

Dorsomedial nucleus-: executive control, olfactory processing

What do Association nuclei do?

Connect different part of cortext to eachother.

• They are critical modulators - not just passing info but SHAPING how one cortical area interacts w/ another.

• “Control towers” - between cortical regions

Dorsalmedial (DM) - reciprocal connection to Prefrontal cortext 

ROLE: emotion, decision making, executive function (problem solving) 

Pulvinar -  Reciprocal connections to Parietal , temporal, occipital, association cortext

Attention, sensoryintegration, higher order visual processing.

Intralaminar nuclei

• Arousal

• Goal oriented behavior

What does TRN stand for? 

Thalamic Reticular Nucleus 

Neurons that filter senses and boost attention.

• GABA ( inhibitory)

• critical role for slective attention

What are intralaminar nucleus? 

CM / PF : Centromedian and Parafascicular nuclei involved in regulating arousal and attention.

• excitatory input

What is the reticular nucleus?

TRN: Thalamic Reticular Nucleus, a group of GABAergic neurons that modulate sensory information and play a crucial role in attention and sleep-wake cycles.

• inhibitor

what is blood supply in thalamus?

Mostly by branches of PCA (posterior communicating artery)

Thalamic syndrome is also known as ….

Dejerine- Roussy syndrome : disturbance of emotional response to sensory experience.

what causes Dejerine- Roussy syndrome? 

Damage to postoventral and posterolateral nuclei 

s/s occurs on contralateral side 

Thalamic syndrome list sensory symptoms: 4 total

Thalamic phantom limb - cant locate positiion of limb , loss of kinesthetic sensation .

Astereognosis - Inability to tell to recognize objects by touch w/ eyes close.

Thalamic over reaction - Exagerated sensory reaction to touch,pain,temp.

Amelognosis - Ilusion of absent limb

Thalamic syndrome ( Motor symptoms) 

Thalamic hand/ athetoid hand:

• flexion of wrist w/ hyper extended fingers 

• Ataxia / mm weakness

• involuntary movements,( tremors, chorea, athetosis. ) 

Thalamic stroke ( bilateral lesions ) causes

Cognition and sensory motor deficits

cognitive: agitation, disorientation, memory

sensory : pain and hemiparesis