RAT neurons is a concEPT of importance to the ÆPT meaning (and simple definition) of consciousnessT.
The concEPT (ÆPT notion) refers to excitatory neurons of "Reticular Activating Type" (conventionally referred to as "the ascending reticular activating system") that contribute a basic and most essential energizing background to all levels of consciousnessT.
RAT neurons are excitatory neurons that typically have diffuse (widespread) axonal projections and they typically fire in a relatively inert and tonic fashion (i.e. fires in a relatively slow to wind up and to wind down manner).
To the extent that the saying "ontogeny recapitulates phylogeny" is true, one might conclude that the earliest form of consciousnessT (or earliest form of "1st-line" consciousness) came "on line" (in by quantum-weirdness underpinned brain-spacetime) roughly concomitant with the emergence of RAT neurons in the evolution/phylogeny of fauna.
It can be surmised that among RAT neurons, those that play a more fundamental life-maintaining role fire more continuously or more regularly.
A relevant general reference:
Of all the concEPTs that I contrived to be expressible as mirth-inviting and as far as possible also appropriately or deservedly allusive acronyms, RAT-neurons is the least appropriately allusive concEPT—actually, "RAT neurons" is not even in the slightest an appropriately allusive expression. Anyhow, it is definitely inspiring of mirth in me.😄
"RAT neurons" suits being classed as one of the 3 concEPTs that exemplify septic humor. The other two are "Actention Selection Serving System" (ASSS) and "Specific Hibernation Imploring Threat" (the only one that becomes 'distinKtly' septic humored when abbreviated💩).
The function of RAT neurons in an ASSS (actention selection serving system) is ÆPTly seen (most simply and schematically so) as partnered by neurons with a "specific" type of functure. An 'S-type neuron' would typically have axons that terminate on relatively few target neurons, and fire readily and in a phasic fashion (in short bursts).
With non-vital RAT neurons rendered silent we could not pay anything but fleeting and affectless/feelingless actentions — if that.