Facilitation and Attention

Recent research has shown that facilitation follows attention in the Cerebral Cortex.

In order to understand why this might be, it is important to recognize the fact that the 40 hertz signal noted in a recent article on anesthesia, and Facilitation might be connected. What the anesthetist discovered, was a link between the 40 hertz signal, and Long-term Implicit Memory.

One model of Cerebral Plasticity, suggests that the Facilitation effect, is just as much a trigger of cerebral plasticity, as LTP is a trigger of Hippocampal Plasticity. To understand how this might work, we need to look at the nature of the biochemical pathway that links synapses to the DNA, something that is well characterized for the hippocampal neurons and the NMDA ion channel.

The Facilitation effect, which reverses almost instantly cellular habituation, is triggered by the S synapse, which is a Calcium synapse that pumps calcium into the cell. The primary difference between this and the NMDA synapse, is the fact that the S synapse does not also, pump Potasium out of the cell, potentiating the cell.

What facilitation makes possible is strings of activation of the same cell. Habituation would attenuate the firing of the cell, as Calcium content dropped in the Axial Buds. This is thought to be because Calcium makes it practical for NeuroTransmitter Vessicles to bond to the Presynaptic surface so that they can secrete the NeuroTransmitter into the synaptic gap.

A shortage of calcium, due to a supply shortage, would therefore result in a gradual attenuation of the signal, as the same neuron fires multiple times. This effect called habituation will reverse as soon as a calcium supply hits the axion buds.

The Facilitative effect is therefore a result of an increase in supply of Calcium to the Axion.

However this is not all that is happening when the S synapse fires. The calcium reacts with other chemicals in the cell, causing the formation of a secondary messenger called cAMP The combination of increased calcium, and a supply of cAMP causes a number of chemical pathways to operate, which trigger eventually DNA expression, that triggers the growth of new Synaptic Spikes, and new Neural processes such as dendrites, and Axions.

The link between the 40 hertz signal and implicit memory probably happens because of activation of the S synpase.

The link to Attention however that is suggested by the new work linking Facilitation to Attention, probably lies in the direction of the 40 hertz signal during pre-activation of cortex areas by the Thalamus in the bottom-up attention system. 

Other blog entries written by Graeme Smith:

• Phosphorylation, the link between Bipolar and Schizophrenia
• A possible role for the anterior cingulate cortex in hypnosis