Darlington and Lisberger (2020) have brought to the fore the notion that we now have an empirical way of evaluating a vertebrate’s level of consciousness/thinking by assessing the prevalence of preparatory activity preceding a movement, particularly when the movement is not generated even though the preparatory activity is a precise predictor of the visuomotor parameters needed to accomplish the act (namely, thinking about doing without doing, see Footnote 1). William James (1890), whose knowledge of the brain paled in comparison to the current knowledge on the topic, was very aware that consciousness is merely a representation of a delayed sequence of movements (see Footnote 2), such that thinking about going to the bank versus actually going to the bank is not that different vis-à-vis consciousness, both engage the same neurons in the neocortex (Darlington and Lisberger 2020). The energy expended per neuron in neocortex is 20 times greater than it is for a neuron in the cerebellum, a least in mammals (Herculano-Houzel 2011). This high level of activity in the neocortex has been attributed to consciousness being a continuous process (with no gaps) and not dependent on whether a subject is immobile or moving (Herculano-Houzel 2011; Tehovnik, Hasanbegović, Chen 2024). Furthermore, the foregoing challenges the assumption that different neocortical neurons are active during consciousness versus automaticity for the performance of the same task (Tononi et al. 2016), since even when one is executing an automated act (which is now mediated by a skeleton-crew of neurons in the neocortex and cerebellum, Tehovnik, Hasanbegović, Chen 2024), the consciousness required to trigger automaticity still depends on the neocortex. Therefore, the neural segregation between the neurons mediating consciousness and those mediating automaticity should be based on the different tasks being performed simultaneously by the neocortex: e.g., the neurons mediating the automatic driving of a car and the neurons subserving one’s plans for the day while driving; it is for this reason that practitioners of information theory never make a distinction between a conscious and an unconscious act, but instead consider only the amount of information transferred per task by way of the brain (Coupé et al. 2019; Reed and Durlach 1998; Tehovnik et al. 2013; Tehovnik and Chen 2015; Tehovnik, Hasabegović, Chen 2024; Tehovnik and Teixeira e Silva 2014).

Since all declarative conscious information is stored in the neocortex (at a maximal capacity of 1.6 x 10^14 bits, Tehovnik, Hasanbegović, Chen 2024), what can we expect when the specific storage areas are damaged by stroke, tumors, infection, or other trauma? Expect the loss of cognitive functions subserved by the damage area. Damage to Wernicke’s or Broca’s areas produces aphasia that cannot be recovered if the damage is extensive by including all the vital storage neurons (Kimura 1993; Ojemann 1991; Penfield and Roberts 1966). Likewise, complete damage to area V1 causes blindness such that all conscious vision is eliminated while sparing blindsight (Tehovnik et al. 2021). Blindsight, which is being able to detect high-contrast (> 95% contrast) visual stimuli in the absence of conscious awareness, is mediated by at least two pathways: the tecto-extrastriate pathway the subserves the detection of punctate targets and the pretecto-extrastriate pathway that subserves the detection of large barriers and tunnels (Tehovnik et al. 2021). Some have suggested that projections between the lateral geniculate nucleus and extrastriate cortex participate in blindsight, but there are serious methodological problems with this study (Schmidt et al. 2010; see Footnote 3). When other primary sensory channels are damaged in the neocortex a similar type of ‘blindsight’ ensues for the other senses, but more work needs to be done in this regard (Tehovnik, Hasanbegović, Chen 2024).

The neocortex is responsible for setting the performance gains for most behaviors including something as basic as VOR (i.e., the vestibuloocular reflex, as alluded to in the study of Darlington and Lisberger 2020), prism adaptation (Held and Hein 1958), and classical conditioning (Pavlov 1927; Tehovnik, Hasanbegović, Chen 2024) and therefore at least for vision the subcortical pathways are insufficient for learning (Schiller and Tehovnik 2015; Tehovnik, Hasanbegović, Chen 2024). What this suggests is that declarative consciousness as mediated by the neocortex is likely responsible for both simple and complex learning (Hebb 1949, 1960, 1968).

Finally, preparatory activity in the absence of movement can act as a proxy to determine the extent of consciousness in a vertebrate species (using the methods of Darlington and Lisberger 2020). All vertebrates have a neocortex or its homologue, the telencephalon; what proportion of neocortical/telencephalic neurons per species exhibit preparatory activity in the absence of movement and how well correlated is the activity in the prediction of behavior needs to be determined. This might be called an animal’s aptitude for thinking. According to Chomsky (2012), such an aptitude should not be possible for any animal other than the human; this we disagree with (Tehovnik, Hasanbegović, Chen 2024). Christof Koch (2013) declared that all animals have consciousness. Now we have one way to study this. Another would be to determine the ratio of energy consumed per neurons for telencephalic neurons vs. cerebellar neurons (Herculano-Houzel 2011). An animal exhibiting a high level of consciousness should have telencephalic neurons that consume high amounts of energy, even when the animal is immobile.

Footnote 1: Darlington and Lisberger (2020) studied the preparatory activity of neurons in the frontal eye fields preceding the smooth pursuit of a target by monkeys. The preparatory neurons in the frontal eye fields faithfully discharged to the predicted velocity of a future pursuit response irrespective of whether there was a response or not (see Figs 1-9 of Darlington and Lisberger 2020).

Footnote 2: James (1890) believed that consciousness or movement (he did not discriminate between the two) occurs in a stream. This stream is part of a continuous feedback-loop based on the proprioceptive and vestibular states of one’s body concurrently linked to the other senses (present and remembered) as it pertains to vision, audition, somatosensation, gustation, and olfaction. Proprioceptive and vestibular systems are often associated with unconscious processing, but when they are not functioning as is common with extreme Parkinsonism, such patients can be put into a perpetual state of falling into a vortex for years, as has been reported by L-DOPA-recovered subjects (Sacks 1976).

Footnote 3: Schmidt et al. (2010) have suggested that projections via the lateral geniculate nucleus (LGN) to extrastriate cortex are sufficient to maintain blindsight (Schmidt et al. 2010), but in this study unilateral inactivation was performed in the LGN (of V1 damaged animals) which induces a position habit such that saccades occur preferentially into the field ipsilateral to the LGN lesion, i.e., the intact field. Bilateral lesions of the LGN would have been the better way to do this experiment. Also, the fMRI signal strength of extrastriate cortex to visual presentations was minimally different for the V1-only-lesion condition and the V1-LGN-lesion condition, and often not significant.