Intracellular foundations of mammalian cognitive capabilities

In reptilian 3-layer cortex and immature mammalian 6-layer neocortex apical inputs provide excitatory drive to pyramidal cells. In mature neocortex they modulate response to basal input by amplifying signals that are relevant in the current context while suppressing those that are irrelevant or interfering. This supports the theory of coherent infomax, which is based on such context-sensitive flexibility, and which has now been further developed using recent advances in information theory. Computational studies indicate that apical amplification (AA) can be used in algorithms for Gestalt organization, contextual disambiguation, priming, attention, and invariant object recognition. Apical function in neocortex depends upon HCN channels that have a long post-natal developmental time-course. They tend to isolate distal apical input from the soma unless closed by the adrenergic system. Adrenergic arousal turns AA on when we awake and turns it up when we attend, thus relating it to the state of consciousness. It is likely that malfunctions of AA are involved in the altered conscious states that occur in several developmental and psychotic disorders. For a review see: https://doi.org/10.1093/nc/niw015