Ventrobasal complex
| Ventrobasal complex | |
|---|---|
| Details | |
| Identifiers | |
| Latin | nuclei ventrobasales |
| TA | A14.1.08.640 |
| FMA | 77794 |
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Anatomical terminology
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The ventrobasal complex ("'VB"') is a relay nucleus of the thalamus for nociceptive stimuli received from nociceptive nerves. The VB consists of the Ventral posteromedial nucleus (VPM) and the Ventral posterolateral nucleus (VPL). In some species the ventral posterolateral nucleus, pars caudalis is also a part of the VB. The VB gets inputs from the Spinothalamic tract, Medial lemniscus, and corticothalamic tract. The main output of the VB is the primary somatosensory cortex.
The VB serves as the main relay for nociceptive stimuli and the modulation of that stimuli to the primary somatosensory cortex. The modulation occurs through different types of receptors present in the VB.
Spinothalamic Tract (STT) cells that project from laminae I and V in the lumbrosacral area of the spinal cord project to the VPL in the VB. STT cells located in the cervical area of the spinal cord are the densest and project from the neck of the dorsal horn to the VPL of the VB. Most projections to the VB are contralateral while only a few projections to the VB are ipsilateral.
Excitatory inputs to the VB are medial lemniscal (ML) and corticothalamic (CT) glutamatergic synapses. The ML is a sensory afferent input and the CT is from layer VI of the primary sensory cortex.
The VB also gets inputs from areas in the brain stem which release Acetylcholine (ACh) that can modulate activity in the VB.
The VB has outputs to the primary somatosensory cortex.
There is two types of nociceptive neurons that provide input to the VB: nociceptive specific (NS) neurons and Wide dynamic range neuron (WDR).
NS neurons respond specifically to a noxious mechanical stimuli, whereas WDR neurons respond to a graded mechanical stimuli. NS and WDR neurons within the VB are somatotopically organized. NS neurons are located more caudally in the VB, while WDR neurons are located more rostrally. All inputs into the VB are contralateral and have two different receptive fields within the VB. The VPM receptive field receives input from the contralateral trigeminal nerve and the VPL receptive field receives input from the contralateral spinal nerve. Each have NS and WDR neurons but terminate either caudally or rostrally respectively.
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