My proposed structure of the brain organised hierarchically as superimposed neural loops is consistent with most historical perspectives of the hierarchical organisation of the nervous system from early philosophy to modern neuroscience.
This hierarchy becomes obvious to anyone who tried to kill a chicken by simply cutting its neck, as I tried in my childhood at the family farm. Like me, they would have discovered that the headless chicken can still run around for several seconds, spattering blood everywhere. Only by twisting its neck can this is avoided. In these vertebrates, the spinal cord appears to be under some inhibitory control from the levels above. This suggests that lower levels of the nervous system disconnected from higher centres are released from inhibition.
An early idea of hierarchy of human functions was expressed by some Greek and Eastern philosophers as a rational control over instincts and is still widely shared.
Although many of the ideas summarised below have been superseded, they represent a clear historical trend in the thinking of a hierarchical organisation of the brain.
Ernst Haeckel (1834–1919) proposed that ontogeny, ie the individual development, recapitulates phylogeny, ie the species evolution, with increasing hierarchical control appearing in evolution of vertebrates.
Source: https://en.wikipedia.org/wiki/Ernst_Haeckel
Herbert Spencer (1820–1903) provided a coherent theory on the evolution, structure, and function of the nervous system. In his Principles of Psychology (1855), he postulated that the human mind can only be fully understood by considering its phylogenetic development. In his view, the phylogeny of mental functions implies that the human mind had evolved in the same way from simple automatic responses in lower animals to higher cognitive processes in humans with a gradual replacement of automatic movements by intentional and goal-directed movements. During evolution, higher centres acquired ability of suppressing more primordial circuits.
Source: https://en.wikipedia.org/wiki/Herbert_Spencer
John Hughlings Jackson (1835–1911) proposed that the brain evolved with increasingly higher levels of re-representation of basic sensorimotor processes. Jackson suggested that the frontal lobes contain representations of action, ranging from the representation of the simplest and most concrete movements to that of the most complex behaviours and language and is hierarchically organised in a series of progressively- and evolutionarily higher areas of the frontal cortex. He proposed that principles governing the reflex arc extend to the cerebral hemispheres with activation of sensory systems propagating upwards from lower to higher cerebral centres governing “ideas” and then to centres producing (or inhibiting) movements.
Jackson explored the consequences of diseases as forms of ‘dissolution’ of the integrated hierarchical brain based on the principle that higher or mature motor systems control or inhibit lower and automatic motor systems, with associated disinhibitory phenomena or release mechanisms.
Source: https://en.wikipedia.org/wiki/John_Hughlings_Jackson
Jackson’s views influenced William James (1842–1910), who, in his classic book The Principles of Psychology (1890), described psychical evolution in terms of the emergence of brain function (and therefore mind) from simple sensory and motor elements.
Sigmund Freud (1856–1939) also contemplated mental hierarchy as based on a stratification of similar neural circuits. His process of ‘regression’ with the collapse of mental levels to more primitive ones reflects a kind of hierarchy. Other psychologists suggested conceptual hierarchical stratification of neural functions with the psychic development of a personality following similar steps.
The French psychologist, Pierre Janet (1859–1947), one of the early proposers of unconscious actions, also suggested that there is a hierarchical organisation of mental function1.
Source: https://en.wikipedia.org/wiki/Pierre_Janet
Constantin von Economo (1876–1931) maintained bold propositions on intelligence and future brain evolution. He postulated a principle of ‘progressive cerebration’, a term to connote the mind’s constant evolution through generations, especially in the prefrontal and parieto-temporal cortex (which also matures later in ontogeny).
Alfred Smee (1818–1877) had already suggested diagrams to portray the hierarchical architecture of the brain circuits2.
Paul MacLean (1913–2007) based his largely superseded theory, also known as the triune brain theory, on the assumption that the human brain actually integrates three different brains, ie. each “brain” represents a specific hierarchic or evolutionary level, ranging from an ancient “reptilian” to a “paleomammalian” and a “neomammalian” brain. The cerebral cortex, due to its high connectivity, is specialised in the integration of multisensory information, and it is the seat of language, abstraction, and planning3.
According to Jaak Panksepp (1943–2017), the image of a “triune brain” provides a useful overview of mammalian brain organisation above the lower brainstem. He suggested nested hierarchies of affective processing, with primal emotional functions being foundational for the secondary processes of learning and memory mechanisms, which interface with the tertiary processes of cognitive or thoughtful functions. According to findings using electrical brain stimulation, Panksepp proposed that instinctual emotional behaviours and feelings emanate from homologous brain functions in all mammals, and that these are regulated by higher brain regions.
- P Janet (1903) Les obsessions et al psychastenie. Alcan, Paris. ↩︎
- A Smee (1875) The Mind of Man: Being a Natural System of Mental Philosophy. G Bell, London. ↩︎
- PD MacClean (1973) A triune concept of the brain and behaviour. University of Toronto Press. ↩︎