Lemniscal system

The Leminiscal system, also known as the Dorsal Column Tract, is important for conveying sensory information from the peripheral and internal structures to the brain

Pathway

 * 1) First order neuron - the tract starts at the dorsal root ganglion cell (pseudo-unipolar cells) with its dendrites in the periphery; axons enter the posterior funiculus and ascend in the posterior column nucleus (spinobulbar tract)


 * 1) Second order neuron - nerve fibres reach the gracilis and cuneate nucleus in the lower medulla oblongata, where its axons project to the thalamus (bulbothalamic tract); fibres of the bulbothalamic tract are internal arcuate fibres, crossing the mid-line (decussation) as they ascend, forming the medial Leminiscal pathway


 * 1) Third order neuron - these neurons are located in the ventro-posterolateral (VPL) and posterior nucleus of the thalamus (pulvinar) with VPL neurons terminating in the primary somato-sensory cortex; fibres from the pulvinar of thalamus terminates in the secondary somato-sensory and association cortex

Function

 * Form recognition
 * Proprioceptive sensation
 * Tactile discrimination
 * Vibration sensation