Physiology
Thalamocortical signaling is primarily excitatory, causing the activation of corresponding areas of the cortex, but is mainly regulated by inhibitory mechanisms. The specific excitatory signaling is based upon glutamatergic signaling, and is dependent on the nature of the sensory information being processed. Recurrent oscillations in thalamocortical circuits also provide large-scale regulatory feedback inputs to the thalamus via GABAergic neurons that synapse in the TRN . 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 . Computational neuroscientists are particularly interested in thalamocortical loops because they represent a structure that is disproportionally larger and more complex in humans than other mammals (when body size is taken into account), which may contribute to humans' special cognitive abilities. Evidence from one study (Arcelli et al. 1996) offers partial support to this claim by suggesting that thalamic GABAergic local circuit neurons in mammalian brains relate more to processing ability compared to sensorimotor ability, as they reflect an increasing complexity of local information processing in the thalamus. It is proposed that core relay cells and matrix cells projecting from the dorsal thalamus allow for synchronization of cortical and thalamic cells during "high-frequency oscillations that underlie discrete conscious events", though this is a heavily debated area of research.
Read more about this topic: Thalamocortical Radiations
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