Diencephalon structures
- thalamus
- hypothalamus
- epithalamus
Thalamus
Gateway to cerebral cortex; sorts, edits, and relays ascending input
Hypothalamus
Controls autonomic nervous system and endocrine system
Epithalamus
Pineal gland (body) extends from posterior border and secretes melatonin
Thalamus impulses
- impulses from hypothalamus for regulating emotion and visceral function
- impulses from cerebellum and basal nuclei to help direct motor cortices
- impulses for memory or sensory integration
Thalamus main function
Mediates sensation, motor activities, cortical arousal, learning, and memory
Anatomy of the thalamus
- internal medullary lamina: dense thick band of fibers formed by tracts running between masses
- anterior nuclei
- medial nuclei
- lateral nuclei
Anterior nuclei
Collection of nuclei at the rostral end of the dorsal thalamus:
- anteroventral nucleus
- anteromedial nucleus
- anterodorsal nucleus
Anterior nuclei connections
Limbic system, mamillary bodies, cingulate gyrus, and hippocampus
Anterior nuclei function
Emotional behavior and memory
Medial nuclei function
- affective behavior
- decision making
- judgement
- memory
- stimulates anxiety and dread
Limbic thalamus
Comprised of anterior nuclei and mediodorsal nuclei
Limbic thalamus lesions
- produce emotional disorders and some long-term memory loss
- severe anxiety: bilateral dorsomedial nuclear lesions or severing frontal lobe connections
Lateral nuclei
- sensory and motor
- medial and lateral geniculate
Lateral posterior and pulvinar nucleus
Receives afferent fibers from superior colliculus and has recripocal connections to the superior parietal lobe
Ventral posterior lateral (VPL)
- Dorsal column medial lemniscus tract
- spinothalamic tract
Ventral lateral
Cerebellothalamic tract
Medial geniculate
- Represents the thalamic relay station of the auditory pathway
- receives input from auditory system
- cochlear nuclei and inferior colliculus
- projects to temporal lobe
- aids with auditory perception
Lateral geniculate
- Represents thalamic relay station of the visual pathway
- receives input from retina
- projects to occipital lobe for visual perception
- species difference
Motor thalamus
- ventral lateral and ventral anterior nuclei of the lateral mass
- input: extrapyramidal (involuntary) motor centers—> basal ganglia, substantia nigra, cerebellum
- projections: motor cortisol areas of the frontal lobe
Sensory thalamus
- ventral posterior medial
- ventral posterior lateral
- medial geniculate body
- lateral geniculate body
Sensory thalamus tracts
- VPL nucleus: somatosensory input from the body
- VPM nucleus: input from the head
Cognitive thalamus
- pulvinar: modulate cortical synchrony needed for perception; attention and emotional processing
- lesions: loss of mental life and awareness of surroundings
Thalamic disorders
- stroke/lesion
- unconsciousness
- sleep disorders
- aphasia
- movement disorders
- pain syndrome
- korsakoff syndrome
