Scientific Understanding of Consciousness
Unexpectedly Meeting a Friend
As a pedagogical example of brain processes and consciousness, I'll consider a scenario in which you unexpectedly meet a friend as you walk along a downtown city sidewalk in normal pedestrian traffic.† As you walk along in reverie of daily thoughts, your vision circuitry perceives and recognizes a familiar face in less than a second.† The novelty of the facial recognition recruits the attention circuitry to focus neural activity on sensory stimuli related to the encounter.† Your emotions and limbic circuitry respond with a facial smile and body gestures of a hand wave, etc.† Your emotions and limbic system also give you a "warm glow" of emotional pleasure.† As you strike up a chatty conversation, Wernicke's area and Broca's area are active in language functionality.† Widespread short-term memory areas are busily processing information via local recurrent circuitry.† Hippocampus and cortex are very active in their reciprocal connections.† The thalamocortical system, working memory and long-term memory cortical areas are busily recalling consolidated long-term memories.† Premotor cortex, motor cortex, basal ganglia, cerebellum, brainstem circuitry and spinal cord are busily concatenating and hierarchically nesting stereotyped motor programs of speech.† Most of this neural activity proceeds unconsciously.† The dynamic core of the thalamocortical system contains the neural activity with the emergent property of consciousness.† The neural synaptic connections of the dynamic core are constantly changing on the basis of† ~100-200 ms as thoughts fleetingly change.
A human normally has orientation in a number of functions and characteristics.† My opinion is that the brain functionality of most of these functions is not well understood.
∑ Sexual Orientation
I think the identity characteristic is engraved into synaptic efficacies comprising a part of the self, resulting from genetics and lifelong experiences.
The sexual orientation characteristic is engraved into synapses via genetics and prenatal hormonal stimulation.
The brain seems to exhibit dominance for consciousness, which for most people exhibits a left-brain dominance.† Roger Sperry and Michael Gazzanigaís work and studies with split-brain patients have discovered what Gazzaniga calls the "left brain interpreter," which is dominant for consciousness, receiving much support from the right hemisphere in areas such as spatial orientation, neural representation of the self, musical cognition, etc.
Split-brain patients (Gazzaniga; Human, 308)
The sensory areas of the cortex contain much hierarchical circuitry that functions in parallel to form memory traces through multiple levels of the hierarchy.† For example, the visual system contains multiple layers culminating in perception mainly in the temporal cortex and its connections with the prefrontal cortex.† Fusterís Perception-Action Cycle emphasizes this hierarchical organization with its reentry and recursion having many forward and back projections continuously circulating signals.† The neural network forms an internal model of reality, which it uses via Bayesian inference to form action plans.
The brain has many widespread local recurrent circuits functioning as short-term memory.† Many of the circuits, which may be momentarily functioning with the dynamic core, may later have the memory traces consolidated as long-term memory.
Hippocampus-Dependent Declarative Memory
Your friend comments that she is going to a department store in response to a newspaper ad for a particular sale item.† You reply that you were in the department store just yesterday, saw the items on display, and thought they were attractive.† The memory of your recent shopping episode is a hippocampus-related memory that will not endure long-term unless it had some feature of emotionality or novelty.
Also, your memory of this sidewalk encounter with your friend will persist for a few weeks, then gradually fade.
Consolidation of Memory during Sleep
Memories of your friend related to special events will have been consolidated during sleep and dreaming.† You will remember graduation from high school, specific vacations, weddings, funerals etc.
If the episode contains some aspects of novelty or emotion, it will likely be tagged and consolidated as long-term memory.† If, for example, your friend was on crutches with a leg in a cast, the episode would likely be consolidated into long-term memory and not require the hippocampus for long-term recall.
While conversing with you friend you likely will invoke long-term memories, which will be reconstructed along memory trace pathways closely aligned with the the original pathways created and consolidated for the memory.
Conversation with your friend will likely evoke some of the primary emotions along with some of the secondary or social emotions. There is no consensus among psychology researchers about the emotions that should be included in these lists.
One researcher lists seven basic, primary or universal emotions: fear, anger, sadness, disgust, contentment, surprise, and happiness.
In addition to the primary emotions, humans have secondary or social emotions such as: embarrassment, jealousy, guilt, pride.
The neural substrate of these emotions is likely to be the limbic system including the orbitofrontal cortex, the anterior cingulate cortex, and perhaps other areas of cortex.
basic regulation of body processes
evolving understanding of the composition and functionality of the limbic system.
orbitofrontal cortex, anterior cingulate cortex, limbic system, pleasure pathway.
Spoken language involves Fixed Action Patterns (FAPs) in the Brocaís area, basal ganglia, cerebellum, and spinal cord.
Listening to spoken language involves FAPs in the auditory cortex, Wernicke area, parietal cortex, and frontal cortex.
While our brains are actively producing spoken language, we are often watching the face and body language of people listening to us, sometimes deciding to make changes in the in the discourse plan as we see them wince or laugh or smile. (Andreasen, Creating Brain, 64)
Modulatory neurotransmitters, operating in seconds, minutes or longer, often emanate from widely-projecting neurons clustered in sub-cortical ganglia. Chemical and functional changes in the synapses of neurons provide many of the short-term and longer-term changes such as memory in the brain function of neural networks.
The four neurotransmitters (norepinephrine, dopamine, serotonin, acetylcholine) originate in nuclear formations of the brain stem and project to orbitomedial and lateral prefrontal cortex. (Fuster; Prefrontal Cortex, 65)
The five senses gather much more information than the human brain is able to process.† We must have a facility to focus attention and to ignore a lot of what is happening around us. (Andreasen, Creating Brain, 103)
Subcortical activating systems in the thalamus, with its rich and diverse connectivity to the cortex, have been considered a likely site for selective engagement of specific cortical functions. (Fischler; Attention and Language, 385)
Oscillations and Synchronization
During normal wake time activities, the brain exhibits a wide spectrum of electrical "hum." This electrical cacophony is the result of myriads of local recurrent circuits at lower hierarchical layers together with lower-frequency feedforward and back projecting signal pathways at hierarchical layers.† The synaptic connections of the signal pathways are dynamically established on the basis of about 10-20 ms at the local level and on the basis of about 100-500 ms at higher levels in the hierarchy.† At the lower, local level of the hierarchy the oscillations are perhaps ~40 Hz or higher, while at higher levels of the hierarchy, the frequencies are probably around ~10 Hz or less. The spectrum of this electrical activity is "pink noise."
A perception is a widely distributed, sparse, neural network (cognit) (Fuster; Cortex and Mind, 14) of neuronal activity overlaid on the brain's ensemble (the self) of synaptic strengths.† The gossamer pattern of neural activity comprising a perception is sparse and highly differentiated, yielding great specificity in the categorization, and yet highly integrated to combine the active synaptic pattern into a perception.
Reentry and Recursion
Reentrant activity leading to recursion is a fundamental feature of thalamocortical activity, and indeed nearly all neural activity.† Reentrant activity is not simple feedback but functions in a network as recursive multiple pathways, which update cyclically on a time scale of tens to hundreds of milliseconds, rapidly converging to the dynamic coreís synaptically connected neuronal network mediating an instantaneous thought.
The brainís Gestalt functionality exploits the Gestalt laws of perceptual interpretation, wherein the laws of proximity, directionality, similarity, closure, and Pragnanz recruit neuronal assemblies via cues and associative memory functionality to form perceptions and via synaptic plasticity to update memory and to form new hippocampus-mediated memories, which later during periods of sleep may be consolidated into long-term memories.
Most of the brainís neural activity proceeds unconsciously, all of it supporting consciousness but not directly a part of consciousness.† All the brain stem and midbrain functionality together with other subcortical neural structures almost never are directly a part of consciousness.† Even in the cortex, most of the neural activity at any one moment is not directly a part of consciousness.† Only the sparse and fleeting dynamic core with its instantaneous activity directly comprise consciousness.
Consciousness is an emergent property of the neural activity of the dynamic core, an instantaneous, fleeting, synaptically connected pattern of neural activity that forms the neural substrate of a current thought.† No particular neurons, synapses, or neuronal pattern are required.†
Degeneracy, Redundancy, Fault-Tolerance
The degeneracy, redundancy, and fault tolerance characteristics of the brain's neural circuits assure that the stochastic and population statistics properties of synaptically connected neuronal circuits will provide a high likelihood of adequate functionality even under multiple kinds of stress.
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