Recurrent thalamo-cortical resonance
Recurrent thalamo-cortical resonance or Thalamocortical oscillation is an observed phenomenon of oscillatory neural activity between the thalamus and various cortical regions of the brain.
[1][2] Thalamocortical oscillation is proposed to be a mechanism of synchronization between different cortical regions of the brain, a process known as temporal binding.
[5] Because of the leaky channel properties, spontaneous, inherent oscillation can also occur independent of any rhythmic input as well,[2] though the ramifications of this capability are not entirely known and may add nothing but background noise to the thalamocortical loop.
The cortex provides feedback to the thalamus through links to dendrites of these thalamocortical cells and serves as the source of constant thalamic oscillation.
Similarly, nonspecific inputs provide context from internal state of the brain and enter into intralaminar "non-specific" nuclei in the centrolateral thalamus with axons in layers I and VI.
It is not known what the exact function of these columns is, although their formation occurs only when the cortical white matter afferents are stimulated at the gamma frequency range, implying an association with task-focused thought.
The regions of inactive cortex that form between cortical columns were determined to be actively inhibited; administration of a GABAA blocker stops columnar development.
Temporal coincidence could occur through this mechanism by the integration of both specific and non-specific thalamic nuclei at the pyramidal cortical cell, as they both synapse on its apical dendrites.
As there are numerous thalamocortical loops throughout the cortex, this process takes place simultaneously across many different regions of the brain during conscious perception.
Altogether, the specific, ventrobasal neurons in the thalamus serve to introduce sensory input to a self-sustained feedback loop that is sustained by the non-specific, centrolateral TCs relaying information about the current cognitive state of the brain.
[10] Magnetoencephalography (MEG) has been used to show that during conscious perception, gamma-band frequency electrical activity and thalamocortical resonance prominently occurs in the human brain.
In the case of vision, stimulation from light sources can be seen to cause direct changes in the amplitude of the thalamocortical oscillations as measured by EEG.
[2] Contrary to the conscious state, however, it appears that sensory input may be blocked or gated from interfering with the intrinsic activity of the brain during REM.
Non-rapid eye movement (NREM) sleep differs from REM in that gamma activity is no longer prominent, stepping aside for lower frequency oscillations.
While the effect of the deviation from normal patterns of gamma oscillatory activity during conscious perception is not entirely settled, it is proposed that the phenomenon can be used to explain chronic pain in cases where there is no specific peripheral nerve damage.
