Over 50% of human neocortex is devoted to three main sensory modalities—vision, audition, and somatosensation/proprioception—which are topographic senses (Sereno et al. 2022); olfaction and taste have a lesser representation and they are largely non-topographic (Kandel et al. 2013). Thus, even though the neocortex contains 16 billion neurons with 1.6 x 10^14 synapses (Herculano-Houzel 2009; Tehovnik, Hasanbegović, Chen 2024), at least half of these fibres are involved in the transmission of information, along with its eventual storage at a final destination. Neurons of the parietal, temporal, and fronto-orbital cortices house object information as conveyed by the senses (Brecht and Freiwald 2012; Bruce et al. 1981; Kimura 1993; Ojemann 1991; Penfield and Roberts 1966; Rolls 2004; Schwarzlose et al. 2005). The neurons in these areas are devoid of a topography, which is an attribute of the retrosplenial, lateral intraparietal, infratemporal, and orbital cortices all of which are association areas (Sereno et al. 2022). These areas are important for the integration of information before it is sent to the cerebellum (for further storage and efference-copy updating) and to the motor nuclei for task execution (Schiller and Tehovnik 2015; Tehovnik, Hasanbegović, Chen 2024; Tehovnik, Patel, Tolias et al. 2021).
If the first station for a given sense is ablated in neocortex of humans, then all ability to work with that sense is lost as it pertains to consciousness (Tehovnik, Hasanbegović, Chen 2024). For sensory information to be stored in the neocortex, the primary sensory areas must be intact and therefore cannot rely on subcortical channels to replace this function. For example, when V1 is damaged in human subjects they experience blindsight by utilizing residual subcortical pathways through the superior colliculus, pretectum, and lateral geniculate nucleus to transfer information to extrastriate cortex. Under such conditions human and non-human subjects, including rodents, respond only to high-contrast punctate targets or high-contrast barriers such that a human subject will declare that they are unaware of the visual stimuli, namely, they are only aware of their blindness (Tehovnik, Hasanbegović, Chen 2024; Tehovnik, Patel, Tolias et al. 2021). The same occurs for the other senses, but less work has been done in this regard; somatosensation has been investigated and confirmed to exhibit properties akin to ‘blindsight’ when S1 and S2 are damaged in human subjects (per. com., Jeffry M. Yau, Baylor College of Medicine, 2021).
Based on the recent fMRI work of Vigotsky et al. (2022), consciousness is stored in the association/non-topographic areas of neocortex, such that lesions of just the association areas would be expected to abolish all consciousness, which is normally supported by a continuous flow of declarative information by way of the hippocampus (Corkin 2002). Furthermore, it is the association areas that have priority access to the cerebellum (as verified with resting-state fMRI, as reviewed in Tehovnik, Patel, Tolias et al. 2021) for the long-term storage of consciousness after being converted into executable code so that motor routines can be evoked at the shortest latencies after being triggered by minimal signaling by the neocortex, which we believe is what happens in the generation of express saccades and other automated behaviors (Tehovnik, Hasanbegović, Chen 2024).
**The foregoing is an excerpt from a book we (Tehovnik, Hasanbegović, Chen 2024) are writing entitled ‘Automaticity, Consciousness, and the Transfer of Information’ which explores the relationship of the neocortex and cerebellum from fishes to mammals using Shannon’s information theory. It is notable that at the level of the cerebellum, a similar efference-copy mechanism is operative across vertebrates, so that the transition from consciousness to automaticity can be achieved using a common circuit with a long evolutionary history**
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