Thalamus

diencephalon

Thalamus

Hypothalmus

Epithalamus

Subthalamus

pineal gland

secretes melatonin

regulates Circadian rhythm

MGN

for hearing

LGN

for vision

VPM

ventral posteromedial

in the thalamus, taste

sensory from face thru the trigeminal nerve

pulvinar

behavior orientation , visual attention

retinal ganglion cells projections

1. LGN for visual perception

2. superior colliculus (midbrain) control eye movement

3. pretectal area (midbrain) control pupillary light response

4. suprachiasmatic nucleus (hypothalamus) for circadian rhythms

visual pathway

light → photoreceptors → bipolar cells → retinal ganglion cells → optic nerve → primary visual cortex (occipal lobe)

Types of RGCs

Parvocellular (midget) RGC

Magnocellular (parasol)

RGC orientation in LGN

6 layers numbers from ventral to dorsal

1,2 = Magnocellular layers: motion, no color

3,4,5,6 = Parvocellular layers: form, color (red-green), fine spatial vision

Interlaminar neurons = Koniocellular layer (K cells): color (blue-yellow)

Optic nerves / Optic Chiasms / Optic tract

they are all different names given to RGC in different locations of the brain

LGN function

1. simple relay of retinal signals

2. sorting of retinal information

3. control of retinal signals

LGN Layers Input

1,4C Beta,6 = contralateral optic tract

2,3,5 = ipsilateral optic tract

is the LGN layer 2,3,5 ipsilateral or contralateral?

ipsilateral

Dorsal stream pathway

WHERE? Motion/gross spatial vision

Parasol cells (RGC) → Magno layer (Thalamus LGN) → Layer 4C alpha (area 17) → layer 4B (area 17) → maybe go to thick stripe (area 18) → dorsolateral Pareto-occipital cortex (visual association cortex - area 18)

Ventral stream pathway

WHAT?

Form:

midget cells (RGC) → Parvo layer (thalamus LGN)→ layer 4C Beta (area 17)→ Layer 2,3 inter blobs (area 17) → pale stripe (area 18)→ inferior occipital temporal cortex

Color:

midget cells (RGC) → Parvo layers (thalamus LGN) → layer 4C Beta (area 17) → layer 2,3 (area 17)→ thin stripe (area 18)→ inferior occipital temporal cortex (area 18)

Which cranial nerves carry taste information? 

CN 7: ant 2/3 of tongue

CN 9: post. 1/3 of tongue

CN 10: epiglottis and pharynx

Mnemonic: Non Stop Tasting - nine seven ten

MGN auditory relay

MGN receives auditory input from inferior colliculus, send output to Heschl’s gyrus

Posterior column - medial lemniscus pathway

relay from trunk & limbs - VPL = Very Personal Limbs

vibration, proprioception, tactile discrimination

steps:

signals send to dorsal root ganglion → primary sensory neuron →  dorsal (posterior) columns → brain → cross at medulla → secondary sensory neuron → medial lemniscus → VPL (thalamus) → primary motor cortex