Thalamocortical radiations
[10] In a study done by Gibbs, Zhang, Shumate, and Coulter (1998) it was found that endogenously released zinc blocked GABA responses within the TC system specifically by interrupting communication between the thalamus and the connected TRN.[12] Activation of the thalamocortical neurons relies heavily on the direct and indirect effects of glutamate, which causes excitatory postsynaptic potentials (EPSPs) at terminal branches in the primary sensory cortices.When this circuit becomes disrupted symptoms are produced similar to those that accompany multiple sclerosis, suggesting thalamocortical rhythms are involved in regulating sensori-motor pathways in a highly specialized manner.[16] TC-CT rhythms evident during sleep act to inhibit these thalamocortical fibers so as to maintain the tonic cycling of low frequency waves and the subsequent suppression of motor activity.[8] The lateral geniculate nucleus and the pulvinar nuclei project to and terminate in V1, and carry motor information from the brain stem as well as other sensory input from the optic tract.Thalamocortical axons project primarily from the medial geniculate nucleus via the sublenticular region of the internal capsule, and terminate in an organized topographic manner in the transverse temporal gyri.[22] The cortico-basal ganglia-thalamo-cortical loop has been traditionally associated with reward-learning, and though has also been noted by some researchers to have a modulatory effect on thalamocortical network functioning, this is due to inherent activation of the premotor areas connecting the VA nucleus with the cortex.Past research has shown how an increase in spike-and-wave activity within the TC network can disrupt normal rhythms involved with the sleep-wakefulness cycle, ultimately causing absence seizures and other forms of epileptic behavior.Burst firing within a part of the TC network stimulates GABA receptors within the thalamus, causing moments of increased inhibition, leading to frequency spikes, which offset oscillation patterns.[26] The bilateral interruption or severing of the connection between thalamocortical radiations and the medial and anterior thalamic nuclei results in a prefrontal lobotomy, which causes a drastic personality change and a subdued behavioral disposition without cortical injury.