Numerous studies show a breakdown of functional connectivity during various states of unconsciousness. For example, fMRIs reveal cortico-cortical and thalamocortical disconnections during sleep, general anesthesia, and pathological states.
EEG analysis shows similar connectivity breakdowns. Additionally, the repertoire of possible connectivity configurations that can be accessed diminishes during unconscious states and is restored as consciousness resumes. This obviously limits the robustness of information processing that can occur in unconsciousness.
Conscious selective attentiveness likely requires a different repertoire of connectivity than inattentive consciousness. Neuroscientists are also discovering the importance not only of multi-area coherence at a given frequency band, but also that the phase synchrony to two different frequencies can also modulate network communication.
Cross-frequency coupling of the alpha and beta oscillations with higher frequency gamma oscillations can amplify, inhibit, or gate the flow of nerve impulses throughout circuitry. Future advancements will surely include more emphasis on monitoring functional connectivity as the brain shifts into and out of various states of consciousness and unconsciousness.
I think, however, that we will not make definitive progress in consciousness research until we make progress in one area of theory and another of tactical methodology. The theory deficiency lies in models of neural networks. Computer models of man-made networks yield interesting results, but they are probably not relevant.
Brains do not work with the same principles that computers do. Moreover, brain networks have the intrinsic plasticity that cannot yet be duplicated by computers.
The method deficiency is that we have no non-invasive way to monitor the actually signaling in even a significant fraction of all the neurons in all the networks. Moreover, even if we had a way to monitor individual neurons noninvasively, it would likely be necessary to selectively monitor neurons in defined circuits. Ultimately, we may confirm that some things are just not knowable. Surely, however, we can learn more than we do now.
Bonnefond, Mathilde et al. Communication between brain areas base on nested oscillators.
Mashour, George A. Neural correlates of unconsciousness in large-scale brain networks. Trends in Neurosciences. It is impossible to get behind consciousness and observe it, as it is the one that is doing all the observations. It is self luminous and self evident and unknowable and incomprehensible because it is not an object.
Science will never ever understand consciousness as it only deals with what is within the domain of the five senses. William Klemm , Ph. Positive mood is teachable and learnable—and can make you smarter.
Back Psychology Today. Back Find a Therapist.
Back Get Help. Back Magazine. Consequently, to minimise confusion, it is important not to load these terms with added meanings that are peculiar to a given theoretical position. These include not only experiences that we commonly associate with ourselves, such as thoughts, feelings, images, dreams, body sensations and so on, but also the experienced three-dimensional world the phenomenal world beyond the body surface. However some terminological distinctions are important. How phenomenal consciousness relates to preconscious and unconscious mental processing is now a major topic for psychological research.
However it does not accept that thoughts exemplify all conscious contents. Unlike thoughts, pains, tactile sensations, itches and other body experiences appear to have both spatial location and extension in different regions of the body, and the sights and sounds of the experienced external world the phenomenal world appear to have locations and extensions in a surrounding three-dimensional space. These interoceptive and exteroceptive experiences also differ widely from each other and many descriptive systems have been developed for investigating their phenomenology in studies of visual and auditory perception, emotion, pain, and so on.
As one can be conscious of many things other than oneself other people, the external world, etc. Being awake or asleep or in some other state such as coma clearly influences what one can be conscious of. However these global states have a complex relationship to phenomenal consciousness. When sleeping, for example, one can still have visual and auditory experiences in the form of dreams.
Conversely, when awake there are many things at any given moment that one does not experience. This is an important feature of consciousness. However, at any moment, much knowledge is unconscious, or implicit for example, the knowledge gained over a lifetime, stored in long-term memory.
Although the EEG does monitor the appropriate target electrical activity , that activity is an envelope of the algebraically summed signals from heterogeneous neuronal ensembles, which are nerve impulses and their associated postsynaptic potentials nearest the sensing electrodes.
Nonetheless, we do know many useful things about brain function that are surely involved in conscious functioning. Neuroscientists have discovered much of this in lower animals from invasive procedures that are not permissible in humans.
In summary, we can list the following brain functions that are relevant to consciousness:. Oscillatory electrical activity is thought to have a key role in selective routing of information in the brain. Oscillations seem to modulate excitability, depending on phase relationships of linked neuronal ensembles. Two prominent hypotheses have been advanced as crucial for consciousness, and they are not mutually exclusive:.
The key to discovering mechanisms of consciousness is to identify all the neural correlates and then winnow the list to those that are both necessary and sufficient for consciousness. Sometimes, important discoveries occur when you study the opposite of what you want to study. This principle is manifest in studies on brain function during various states of unconsciousness like anesthesia, coma, or non-dream sleep.
A recent review of research compared the neural correlates of unconsciousness with those of consciousness. The evaluation showed disrupted connectivity in the brain and greater modularity during unconscious state, which inhibited the efficient integration of information required during consciousness. Additionally, the review made the key point that the neural correlates of consciousness that matter are the ones that occur in consciousness but not in unconscious states.
Of particular relevance are the correlates related to functional connectivity among networks, because multiple lines of evidence reveal that this connectivity degrades during unconscious states and returns when consciousness resumes. In rodents, multi-array recordings in visual cortex indicate that connectivity patterns are the same during anesthesia as in wakefulness.
Understanding Consciousness () is a book by Max Velmans, Emeritus Professor of Psychology at Goldsmiths, University of London, which combines an . Many scientists, even physical scientists, assert that the Holy Grail of science is to understand human consciousness. This human state is even.
Perhaps this indicates that rodents do not have the needed network architecture to enable consciousness. They can be awake but not conscious. Being awake is clearly necessary for consciousness, but not sufficient. At any given instant, we are only consciously aware of the specific cognitive targets to which we attend. Statistical co-variation of activity in linked networks is a measure of functional connectivity.
The activity in linked networks may randomly jitter or be in phase or locked at certain time lags. Operationally, the connectivity may enable one group of neurons to mediate or modulate activity in another for past, present, or future operations. The temporal dynamics of these processes differ depending on the state of consciousness.
Changes in oscillatory frequency and coherent coupling of the oscillations among various pools of neurons are thought to reflect the nature and intensity of thought. The issue arises as to how these voltages, commonly called field potentials, can influence the underlying nerve impulse activity that causes the oscillation in the first place. The messages of thought are carried in patterns of nerve impulses flowing in neural networks. Field potentials are not signaling, at least not directly. They may well indirectly influence messaging by electrostatically biasing networks to be more or less able to generate and propagate nerve impulse traffic.
Neuroscientists attach much importance to the temporal dynamics of EEG voltage frequencies. Later, investigators thought they had found a crucial role for higher frequency gamma synchrony, but that too is now called into question. This gamma synchrony can be present or even enhanced during unconsciousness. However, the spatial extent of synchrony may be the meaningful correlate of consciousness.
Widespread synchrony breaks down during unconsciousness, while more localized synchrony remains intact or even enhanced.