The dorsal column nuclei are a cluster of nuclei found in the brainstem, specifically the medulla. These neurons are important because it is here where the axons of these neurons cross the midline to the opposite side. 

Dorsal Column Nuclei

A dermatome is the region of skin innervated by a particular spinal nerve. The dermatomal pattern is best understood when depicted on a person in a quadrupedal posture.

Dermatome

The dorsal column system is the pathway in which the touch receptors that have sent their axons to the spinal cord, have entered the spinal cord through the dorsal horn and turn upward, traveling to the brain along the spinal cord's dorsal column of white matter.
- Dorsal column nuclei
- Dermatome

Johns Hopkins University

A large part of our somatosensory system is responsible for our perception of touch.
- Sensory Organ: Skin
- Dorsal Column System
- Primary Sensory Cortex
- Secondary Sensory Cortex
- Skin sensory receptors

Somatosensory System: Touch

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Skin is the largest organ in the human body. It is responsible for receiving the environmental stimuli that we process when perceiving touch and pain. The skin is made up of three separate layers.
- Epidermis
- Dermis
- Hypodermis

Sensory Organ: Skin

Dorsal Column System

The primary somatosensory cortex (S1) is located in both hemispheres and lies in the postcentral gyrus of the parietal cortex, just behind the central sulcus dividing the parietal lobe from the frontal lobe. Each S1 receives touch information from the opposite side of the body. 
- Topographic Mapping
- Plasticity of the Sensory Cortex

Primary Sensory Cortex

The secondary somatosensory cortex (S2) maps both sides of the body in registered overlay (ie. the left-arm and right-arm representations occupy the same part of the map and so forth). In recent studies, the S2 has been implicated in information integration, grounded essentially in spatial body maps, allowing humans to form complex relations between the body and the environmental space (establishing a body-in-world map). 

Secondary Sensory Cortex

Sensory neurons located in the skin that respond to various mechanical stimulations. There are 3 main groups of receptors, categorized by what type of stimulus they detect:
- Mechanoreceptors
- Thermoreceptors
- Nociceptors


Skin Receptors

There are anatomical and functional connections between auditory and somatosensory processing. For instance, hearing a rubbing sound and feeling sandpaper with the fingers activates the same part of the cortical area in the caudal auditory region.

Auditory and Somatosensory Processing

Somatosensation, commonly known as the sense of touch, is the sensory system responsible for perceiving contact with the skin.

Touch (Somatosensation)

The pathway for sensory information begins at the skin's receptors and free nerve endings. From there, signals ascend the spinal cord and are relayed through the medulla and thalamus before reaching their final destination for processing in the somatosensory cortex, which is situated in the postcentral gyrus of the parietal lobe.

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