Somatosensory cortex

• Primary motoric area
• Pre / Supplementär - motor areas
• Primary sensory areas
• Sensible association areas
• Hörfelder
• Fields of view

The somatosensory or somatosensory cortex ( gr σώμα soma " body "; Latin sensorius " the sensation serving " sensibilis " sentient " cortex " bark ") is the circumscribed portion of the cerebral cortex, which serves the central processing of haptic perception. The information comes either from receptors in the skin that there a variety of environmental stimuli record ( Exterozeption ) or allow by receptors inside the body 's self-perception ( proprioception ). In the somatosensory cortex processed sensory modalities are touch, pressure, vibration and temperature, sometimes this also applies to pain sensations.

However, not all mechanical and physical stimuli are converted here, already at the level of the spinal cord, there are neural circuits that simple trigger without the intervention of the brain (usually escape ) movements: the reflexes.

The somatosensory cortex belongs to functional consideration for Neolemniscus and is its endpoint.

Classification and location

It is divided into the primary sensory areas (S1, Brodmann areas Area 1, 2 and 3, and later was made a subdivision in Figures 3a and 3b) and the secondary - sensitive or sensitive association areas (S2, according areae 40 and 43). The vast majority of primary sensory cortex in humans is on the dentate gyrus, the first gyrus behind the central sulcus. The secondary fields close to the rear (posterior) and lower (ventral, S2) to.

Construction

The somatosensory cortex is part of the six-layered isocortex. Histologically striking is the stressed inner granule cell layer, which is particularly pronounced in the area 3b, so that in the latter speaks of koniocortex. In particular, the primary sensory cortex is - as well as the immediately adjacent primary motor cortex - a strictly somatotopically. This means that adjacent areas of the body are adjacent to each other here. The result is a ( though with the respective weighting distorted ) image of the body to the cerebral cortex, the so-called Homunculus. The representations of hand, fingers, face and lips are especially extended. Probably exists for each of the four areas of S1 and S2 of the areas of a separate somatotopy, but which partially out of focus presents itself, sometimes even double representation of body parts (eg hand in Area 2).

Neural connections

The afferents (inputs ) of Somatosensory Cortex ultimately come from different sense cells or organs that are distributed over the entire body in different density. The afferent pathways are repeatedly switched synaptically: from the actual sensory cell on pseudounipolar nerve cells whose Zellsomata lie in the spinal ganglia of the dorsal root, the dorsal column nuclei to the thalamus in the second and finally the third neuron. For the sensitivity of the face, the track runs in a similar way via the fifth cranial nerve ( trigeminal nerve ), the first and in the trigeminal nucleus in the brainstem, the second time it is switched in the trigeminal ganglion and also reaches the thalamus. This zentropetale web is in its entirety - including the Sensory Cortex - called Lemniskales system. A second, fundamentally different structure of the sensory conduction system is the spinothalamic tract, but reached only a very small part of the thalamus and thus the cerebral cortex.

Efferents (outputs ) from the Somatosensory Cortex achieve especially associative areas of the same ( ipsilateral ) and the corpus callosum of the other ( contralateral ) hemisphere of the cerebrum. More tracks go back to the thalamus, via the pons to the cerebellum, the basal ganglia and the spinal cord. There are also fibers that contribute to the pyramidal tract.