Scientific Understanding of Consciousness
The neural requirements for minimal consciousness are currently unknown but may become more clearly delineated in coming decades.
· Consciousness requires an object, a focus of the gestalt.
· Yoga Meditation may be an attempt to achieve Voluntary Minimal Consciousness.
· In the practice of Yoga, a person tries to voluntarily minimize the dynamic core gestalt.
· By some interpretations, dreaming is a state of consciousness.
Human-type consciousness built upon basal consciousness can be viewed as ‘normal’ everyday conscious experience. The state of dreaming can be considered one state of consciousness. Abnormal states such as concussion, coma, vegetative state, etc. may have equivocal states of consciousness.
For most of us, our ‘normal’ everyday conscious experience involves our long-term declarative memory. However, this long-term memory is not necessary for consciousness, because we all probably agree that human infants have consciousness although they have not developed long-term memories.
Normal ‘everyday’ consciousness vs. minimal consciousness
Consciousness state can vary from highly alert, to relaxed reverie, sleeping, anesthesia, coma, vegetative state.
At today’s state of scientific knowledge, the minimal brain functionality required for consciousness is unknown.
My understanding is that functionality of portions of working memory, thalamocortical loops, and the limbic system would be required to comprise a minimal dynamic core. Many other regions and functions would necessarily provide a supporting role but would not be a part of the dynamic core directly.
What is known is that the dynamic core of neural activity is the biological basis of consciousness. Consciousness is an emergent property of the dynamic core.
Minimal consciousness -- minimal brain functionality required
Human infants at some stage of development have basal consciousness, although they do not have long term memory. Abnormal states resulting from concussion, anesthesia, coma, vegetative state, etc. may have transient states of partial or minimal consciousness.
Damasio provides a brief description of coma and vegetative state. (Damasio; Feeling of What Happens, 236)
(paraphrase of Shadlen & Kiani; Nature, 2 August 2007, 539-540)
To be awake is to be in a state of engaging with the environment. To have agency is to interrogate this environment with some goal or purpose. This capacity to engage and interrogate seems to go awry in various disorders that affect cognition. And nowhere is this incapacitation more patent than in coma and related conditions.
Coma. The patient seems to be asleep and cannot be awakened. There is no spontaneous organized behaviour, not even pushing away of an irritant, and there is no evidence of any awareness of sensory cues — no response beyond reflexes mediated by the brainstem and the spinal cord. Most patients in coma do not recover meaningful neurological function, but many do progress to states that are clearly distinguishable from coma, such as:
Persistent vegetative state (PVS). This is similar to coma in all respects except that, at times, the patient does not seem to be asleep. The eyes may be open, and spontaneous, non-purposeful, roving eye movements occur. PVS is probably the result of a return of some of the functions that would govern the sleep–wake cycle, albeit in the absence of a functioning cerebral cortex. As a result, it is only the brainstem and perhaps a few islands of dysfunctional (or disconnected) cortex that regain function.
Minimally conscious state (MCS). In contrast to PVS, patients show occasional signs of arousal and organized behaviour. Nevertheless, for the most part, there is a profound deficit in consciousness. Indeed, functional brain-imaging studies indicate that parts of the cortex may be able to function even when the patient seems to be unconscious. This observation and the differential prognosis of MCS and PVS call for more careful classification of patients, which may currently be biased towards PVS.
(end of paraphrase)
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