The Limbic System
“Far from being a state of consciousness divorced from the physical brain, a person's emotions are produced by chemicals exquisitely intertwined with the physiological processes of the body so that in the truest sense what affects the body affects the mind and emotions, and vice versa.The center of emotions in the brain can be found in the limbic system where the vast panoply of emotions is regulated through the release of excitatory and inhibitory neurotransmitters: Pleasure may be linked with chemical signals produced by the release of noradrenalin, and pain is associated with many neurotransmitters. Mood appears to be linked with serotonin and dopamine.
In response to a variety of stimuli, emotions arise in the limbic system, travelling along neural pathways to the frontal lobes of the cortex, where feelings are monitored and interpreted. These two brain structures next influence the hypothalamus, which transmits the messages that trigger appropriate physical responses.”
"The Brain Encyclopedia" by Carol Turkington
Entry: "Emotions and the Brain"
The Limbic system connects the higher and lower functions of our brains, it is called both the "Emotional Center" and the "Conscious System" of the brain. If we, as Humans, had to consider one part of our brains to be the core of our personal consciousness, it would be the Limbic System and, especially, the interaction between the limbic system and the cortex. Physical disruption or disease of the Limbic System causes major behavioural changes.
“A number of highly inter-related structures which, when seen from the side, seem to nest inside each other, encircling the brainstem in a 'wishbone'. The major structures are: (i) thalami bodies; (ii) hypothalamus; (iii) mamillary bodies; (iv) septum pellucidum; (v) cingulate gyrus; (vi) hippocampus; (vii) amygdala; (viii) fornix; and (ix) olfactory bulbs.
The human limbic system is very similar to that of primitive mammals and so it often called 'the old mammalian brain'.[...] The hippocampus is involved in memory; someone whose hippocampus is damaged is very easily distracted and they will be unable to carry out an intended sequence of actions (e.g. making a cup of tea) because they have forgotten what they had planned to do.
The limbic system as a whole serves as a meeting place between the cortex (or 'neocortex', in evolutionary terms the most recent part of the brain to have developed) and older parts of the brain, such as the hypothalamus, [...] these are integrated and the 'conclusions' are fed back to the cortex and to the older, subcortical areas.”
"Psychology: The Science of Mind and Behaviour" by Richard Gross, p58-59
If these nine parts of the limbic system together form the chair on which consciousness sits, the focus that sits in the chair is the interaction between these nine parts and the neocortex, which is the house of our higher functions.
“The cerebral hemispheres are the two largest structures at the top of the brain which enfold (and, therefore, conceal from view) most other brain structures. [...] The top layer of the cerebrum (about 1cm at its deepest) is the cerebral cortex (usually just called 'cortex' which means 'bark'). [...] About three-quarters of the cortex does not have an obvious sensory or motor function and is known as the association cortex; this is where the 'higher mental functions' (cognition) - thinking, reasoning, learning, etc. - probably 'occur'. [...] There is no doubt that the cortex is not necessary for biological survival [...] as some species do not have one to begin with (e.g. birds) and in those that do, surgical removal does not prevent the animal from displaying a wide range of behaviour, although it becomes much more automatic and stereotyped.”"Psychology: The Science of Mind and Behaviour" by Richard Gross, p55-56
If anything resembles the actions of a 'soul' in the Human brain machine, it is the interaction between the cortex and the limbic system.
It is also known that over-activation of the limbic system can result in depression as well as religious phenomenon. In the case of depression, symptoms can be removed by medicating with drugs that affect certain parts of the limbic system, in particular through quantitively altering the action of certain neurotransmitters.
“Because of its relevance to the so-called vegetative symptoms of depression, such as disturbances in appetite and sleep, the hypothalamic - pituitary - adrenocortical axis is thought to be overactive in depression. Various findings support this proposition.”
"Abnormal Psychology" by Davison & Neale, p242
The Conscious System
Our brains bring to the fore items which require wide access to the brains' mechanisms. Most processes cycle within their sub-stations within the brain only communicating with neighbours and hemispheral opposites, but when something is brought up to the general attention of the limbic system, the whole brain becomes involved.
"5. Prioritizing and Access-Control. : Attentional mechanisms exercise conscious and unconscious control over what will become conscious. By relating some particular conscious content to deeper goals, we can raise its access priority, making it conscious more often and increasing the chances of successful adaptation to it.6. Decision-making or Executive Function. : When automatic systems cannot routinely resolve some choice-point, making it conscious helps recruit unconscious knowledge sources to help make the proper decision. In the case of indecision, we can make a goal conscious to allow widespread recruitment of conscious and unconscious 'votes' for or against it."
www.wrightinst.edu/faculty/~baars/book/text/CTC_ch10.htm
The Inner Voice
Your inner voice constantly explains and explores, asking questions to yourself and answering itself! Cyclic, automatic, unstoppable, it is the powerful base of our conscious thinking lives. It is the window through which we view and explain our own experiences and emotions. Our inner voice is largely the same as our center of speech in the brain. If you are engaged in speech, your inner voice is silent. It can't multitask, yet it is the system that requires the most brain power and is the most potent output of conscious thought!
But it can make automatic responses, and you can queue up a series of words and send them off to your medulla and think about other stuff whilst your body deals with the technical procedure or turning a queue of words into actual verbalisation. Sometimes you can go on "automatic", speaking without thinking, as long as we stick to the automatic over-learned patterns of speech we can set our speech center off on its own, and let our inner voice wander off on its own tangents. But as soon as you're not repeating over-learned patterns of words, you're inner voice is required to conjure up more of them and you're internal monologue is silenced.
If you see something, your memory may recall something else, and start your voice talking about that. Input from the environment affects the memory in a big way. Your inner voice and limbic system are cyclic, in combination with the rest of the systems of your brain, largely your memory, a near-constant monologue is upheld. The system is self-referential, the inner voice meandering through topics and the memory responding in kind, then once again the interpretation machinery wanders over the material retrieved by the memory... stimulating more memories and thoughts. This cyclic, chaotic web serves as the ultimate expression of our consciousness, the culmination of a massive network of neurones and biochemistry.
Religion as a Limbic System Dysfunction
Neuroscientists have performed multiple studies of religiosity and the correlated neural responses in the brain. Related to this are the results of a series of experiments that show that electrically stimulating certain parts of the brain induces mystical experiences related to the culture of the individual.
“Most of the neurological phenomena associated with religious experience involve some form over-activation of the limbic system, and correspondingly intensified experiences. Conversely, Alzheimer's disease is associated with a deterioration of the limbic system and those afflicted tend to lose interest in religion, even those who have exhibited a lifelong interest.”M. Spinella and O. Wain, Skeptical Inquirer, 20062