The assumption of an avian consciousness also brings the reptilian brain into focus. The reason is the structural continuity between avian and reptilian brains, meaning that the phylogenetic origin of consciousness may be earlier than suggested by many leading neuroscientists. Joaquin Fuster of UCLA has advocated the position of the importance of the prefrontal cortex in humans, along with the areas of Wernicke and Broca, as being of particular importance to the development of human language capacities neuro-anatomically necessary for the emergence of higher-order consciousness in humans. Biological function and evolution
Opinions are divided as to where in biological evolution consciousness emerged and about whether or not consciousness has any survival value. Some argue that consciousness is a byproduct of evolution. It has been argued that consciousness emerged (i) exclusively with the first humans, (ii) exclusively with the first mammals, (iii) independently in mammals and birds, or (iv) with the first reptiles. Other authors date the origins of consciousness to the first animals with nervous systems or early vertebrates in the Cambrian over 500 million years ago. Donald Griffin suggests in his book Animal Minds a gradual evolution of consciousness. Each of these scenarios raises the question of the possible survival value of consciousness. Thomas Henry Huxley defends in an essay titled On the Hypothesis that Animals are Automata, and its History an epiphenomenalist theory of consciousness according to which consciousness is a causally inert effect of neural activity—"as the steam-whistle which accompanies the work of a locomotive engine is without influence upon its machinery".
Research in this area has not yet reached firm conclusions, but a recent questionnaire-based study identified eleven significant factors contributing to drug-induced states of consciousness: experience of unity; spiritual experience; blissful state; insightfulness; disembodiment; impaired control and cognition; anxiety; complex imagery; elementary imagery; audio-visual synesthesia; and changed meaning of percepts. Entropic brain
The entropic brain is a theory of conscious states informed by neuroimaging research with psychedelic drugs. The theory suggests that the brain in primary states such as rapid eye movement (REM) sleep, early psychosis and under the influence of psychedelic drugs, is in a disordered state; normal waking consciousness constrains some of this freedom and makes possible metacognitive functions such as internal self-administered reality testing and self-awareness. Criticism has included questioning whether the theory has been adequately tested. Theories of origin
The origin and mechanism of subjective experience within the brain remains unknown, although several scientific theories have been proposed. Roger Penrose has said that there are four such current theories.Integrated information theory (IIT) postulates that consciousness resides in the information being processed and arises once the information reaches a certain level of complexity. Orchestrated objective reduction (Orch OR) postulates that consciousness originates at the quantum level inside neurons. The mechanism is held to be a quantum process called objective reduction that is orchestrated by cellular structures called microtubules. However the details of the mechanism would go beyond current quantum theory. Medical aspects
The medical approach to consciousness is scientifically oriented.