Thalamic Nuclei and Functional Organization

Functional Organization of Thalamic Nuclei

• Associative nuclei: receive impulses from other thalamic nuclei, process information, and send it to the association areas of the cerebral cortex
• Examples of associative nuclei:
  • Part of dorsomedial nucleus
  • Pulvinar
  • Lateral dorsal nucleus
  • Lateral posterior nucleus

Thalamic Nuclei Functions

• Anterior nucleus: association; receives inputs from mamillary body and hippocampus, sends outputs to cingulate cortex
• Medial nuclear group: association; receives inputs from amygdala, olfactory cortex, and hippocampus, sends outputs to prefrontal cortex and hippocampus
• Lateral dorsal nucleus: association; receives inputs from amygdala, olfactory cortex, and hippocampus, sends outputs to cingulate cortex and other limbic regions
• Lateral posterior nucleus: association; receives inputs from superior colliculus and pretectum, sends outputs to occipital, parietal, and temporal association areas

Specific Nuclei

• Medial geniculate nucleus: specific nucleus; receives inputs from inferior colliculus, sends outputs to primary auditory cortex
• Lateral geniculate nucleus: specific nucleus; receives inputs from left and right eyes (optic tract), sends outputs to primary visual cortex
• Posteromedial ventral nucleus: specific nucleus; receives inputs from trigeminothalamic tract, sends outputs to primary somatosensory cortex
• Posterolateral ventral nucleus: specific nucleus; receives inputs from medial and spinal lemnisci, sends outputs to primary somatosensory cortex

Thalamus Structure

• Divided into two oval masses of grey matter
• Relays and sends received information to the cerebral cortex
• Axons from every sensory system (except olfaction) synapse in the thalamus as the last relay site before the information reaches the cerebral cortex

Thalamus Surfaces and Relations

• Lateral surface: related to the posterior limb of the internal capsule
• Medial surface: related to the 3rd ventricle
• Superior surface: related to the fornix and lateral ventricle
• Inferior surface: related to the hypothalamus and subthalamus

Internal Structure of Thalamus

• External medullary lamina: covers the lateral surface of the thalamus, consists of thalamocortical and corticothalamic fibers
• Internal medullary lamina: bundle of Y-shaped myelinated fibers, divides the thalamus into anterior, medial, and lateral nuclear groups

Lateral Nuclear Group

• Divided into dorsal and ventral tiers
• Dorsal tier: contains lateral dorsal, lateral posterior, and pulvinar nuclei
• Ventral tier: contains ventral anterior, ventral lateral, ventral posterior, medial geniculate, and lateral geniculate nuclei

Functional Organization of Thalamic Nuclei

• All thalamic nuclei project to the ipsilateral cerebral cortex, except reticular nucleus
• Precise point-to-point projections sometimes found between individual thalamic nuclei and restricted cortical zones

Classification of Thalamic Nuclei

• Classified into three groups: simple sensory relay nuclei, circuit relay nuclei, and diffuse nuclei
• Simple sensory relay nuclei: receive sensory impulses and relay them to the sensory cortex
• Circuit relay nuclei: receive impulses from different areas of CNS and relay them to specific areas in cerebral cortex

Limbic System

• Set of brain structures including cortical structures, subcortical structures, and olfactory system
• Main functions: control of emotions, emotional responses, behavior, mood, motivation, memory, and visceral and motor responses involved in survival

Limbic System Structures

• Limbic cortex or limbic lobe
• Hippocampus and hippocampal formation
• Amygdala
• Anterior thalamic nuclei
• Hypothalamus (mammillary body)
• Septum
• Fornix
• Olfactory system
• Habenular nuclei

Organisation del Thalamo

• Le thalamo es dividite in duo tieres: dorsal e ventral
• Le tier dorsal contains:
  • Lateral dorsal (LD)
  • Lateral posterior (LP)
  • Pulvinar
• Le tier ventral contains:
  • Ventral anterior (VA)
  • Ventral lateral (VL)
  • Ventral posterior (VP)
  • Medial geniculate nucleus
  • Lateral geniculate nucleus

Functional Organisation del Thalamo

• Omne thalamic nuclei projecta al cortex cerebral ipsilateral, excepto le nucleus reticular
• Precise projections point-to-point sono trovate inter individual thalamic nuclei e zonas cortical restricted
• Le nuclei specific lie dentro le tier ventral del grupo nuclear lateral

Classification del Thalamo

• Le nuclei thalamic peuvent essere classificate in tre gruppos, cada uno con quatro nuclei:
  • A) Simple Sensory Relay Nuclei:
    • Receive impulses sensory, e relay them to le cortex sensory
    • Include: PLVN, PMVN, LGB, MGB
  • B) Circuit Relay Nuclei:
    • Receive impulses from different areas del CNS, e relay them to specific areas del cortex cerebral
    • Include: Lateral ventral nucleus, anterior ventral nucleus, anterior nucleus, part del dorsomedial nucleus
  • C) Associative Nuclei:
    • Receive impulses from other nuclei thalamic, e send information processed to le areas del cortex cerebral
    • Include: part del dorsomedial nucleus, pulvinar, lateral dorsal nucleus, lateral posterior nucleus

Functional Organisation del Nuclei Thalamic

• Anterior nucleus:
  • Function: association
  • Inputs: mamillary body, hippocampus
  • Outputs: cingulate cortex
• Medial nuclear group:
  • Function: association
  • Inputs: amygdala, olfactory cortex, hippocampus
  • Outputs: prefrontal cortex, hippocampus
• Lateral dorsal nucleus:
  • Function: association
  • Inputs: amygdala, olfactory cortex, hippocampus
  • Outputs: cingulate cortex, other limbic regions
• ... (continua con le other nuclei)

Systema Limbic

• Definition: un set de structuras del cerebro evolutionariamente primitive, locate sur le brainstem, e buriate sub le cortex
• Functiones: involve emotions, motivations, sensations de pleasure, e memoria
• Partes del systema limbic:
  • Cortical structures: limbic lobe, hippocampal formation, septal areas, prefrontal area
  • Subcortical structures: hippocampus, amygdala, anterior thalamic nuclei, hypothalamus, septum, fornix, olfactory system
  • Olactory system: olfactory bulb, olfactory tract, olfactory cortex

Hippocampo

• Location: parte del systema limbic
• Function: involvement in memoria, emotions, e comportamento
• Lesions: associate con loss de memoria, e alteration de comportamento