I now return to the article by Spruston to focus on a possible role for apical pyramidal cell tufts in the cognitive activity of the immaterial mind. I am posting excerpts from his article along with my comments, primarily reflecting posts I have made in previous blogs and in my books.
“Pyramidal neurons are abundant in the cerebral cortex . . . they are found primarily in structures that are associated with advanced cognitive functions. . . . Critical to the function of each pyramidal neuron is how it responds to its synaptic inputs to produce an action potential that excites its postsynaptic targets. . . . All pyramidal neurons have several relatively short basal dendrites. Usually, one large apical dendrite connects the soma (cell body) to a tuft of dendrites. . . . [there is] some evidence [that] supports the division of pyramidal cell dendritic trees into . . . domains, which correspond to regions that receive distinct synaptic inputs and/or have synapses with distinct properties. . . . it is reasonable to postulate that pyramidal neurons with different structural features are also likely to differ functionally. . . . inputs to the main apical dendrite and the oblique apical dendrites might be integrated differently, but it is not known whether synaptic inputs to these domains are identical or different.”
Hence, it is acceptable for me to offer a postulate on how wave forms generated by cognition interact with the pyramidal tufts and their numerous spines to stimulate changes in the microstructures of ionic channels to initiate dendritic spikes. This action could involve quantum tunneling as we have seen with the transmission of wave forms through potential barriers at neural synapses to initiate spike trains of action potentials that transmit specified codes. Just where, I am asking, would wave forms generated by the immaterial mind act? In subsequent blogs I will address the statements of Sir John C. Eccles that are prescient in this regard. Let us read on.
“Pyramidal neurons are covered with thousands of dendritic spines that constitute the postsynaptic site for most excitatory glutamatergic synapses. . . . The function of dendritic spines remains enigmatic. . . . Spines vary considerably in their size and shape and are highly plastic [so that they may be functional in memory and learning].”
I have discussed in my books and several blogs how the immaterial mind “learns” to interpret neural codes over a lifetime as well as generates their formation within spike trains of action potentials. Neural codes are archived in memory and accessed by the mind to effect desired actions with purpose and meaning. An example I have discussed in my books is the supplementary motor area, where neural codes for various motor actions are archived in the so-called liaison brain described by Eccles.
When dendritic spines are stimulated by incoming wave forms they “exert significant influence over action-potential initiation through the activation of dendritic voltage-gated channels, which can enhance charge entry at distal synapses and might even lead to dendritic spike initiation. Several observations suggest that synapses at different dendritic locations are specialized to perform different functions . . . The apical tuft also has a relatively large number of [spine] synapses on the dendritic shaft. These differences suggest that these various dendritic regions receive synaptic inputs that have distinctive properties.” [The author does not address cognitive function and its potential application to this process.]
In my next blog I will continue to draw upon Spruston’s article, focusing on the process of dendritic excitability and coincidence detection, leading to the discussions by Eccles that are prescient in this context.