Sunday, December 10, 2017

Excerpt form 'The Mind at Night'

The Mind at Night

Neuromodulators for wakefulness.

When we are awake, tow neuromodulators are essential to alert, waking consciousness : nerepinephrine ( help direct and focus our attention), and serotonin.Serotonin is not only in charge of mood regulation, but also judgment, learning, and memory. After we fall asleep, acetylcholine  excites visual, motor, and emotional centers of the brain and transmit signals that trigger rapid eye movements and visual imagery in dreams. (Ach is also responsible for neuro-muscluar junctions transmission in mammal.)


Anti Freudism
Hobson and McCarley's study maintained that since the signal that initiated the creation of dream imagery and came from brain stem and neocortex were just passively response. The resulting dream was the product of the forebrain making the best of the bad job producing even partially coherent dream imagery.

We forgot most of our dream because the two neuromodulators need to imprint them on memory are in short supply until we akwen.

PET scanning shows that prefrontal cortex takes the first and deepest plunge before the overall decrease of global activities. The area is the first to fall asleep and the last to come back on-line. Deactivation of the area is accompanied by sharp drops in levels of serotonin and nerepinephrine, which help us focus when we are awake. Then surge the acetylcholine (which fosters free-wheeling association) that turns on REM sleep. Its inactivity would explain why we have no reality testing in dreams.

REM may provide a situation where long-term memory traces can be processed off-line, either consolidated or pruned (LTP and LTD), while the prefrontal area is not actively processing information generated during REM itself.

Deja vu : 
The feeling that we have seen something before but we connot recall. Deja vu is like the episodic memory version of getting lost in a maze because of its grid cell firing pattern overlaps with another location in mental spatial map.



Hypothesis I  :  Clear address to empty house
Would it be possible that we dreamed of it before? Although our brain is designed not to remember the dream content (because it makes no sense in reality), but there's chances that some part of the memory circuits that were strengthened synthetically during sleep is activated by the daytime experience. This pathway is distinctive, but it doesn't contain interpretable information.

Hypothesis II : Associative emotional memory
Deja vu might be caused by activation of 'emotional memories'. Emotional memories are not declarable, but participate in the formation of declarable episodic memory. Deja vu may involves emotional memory, which also account for feeling of nostalgia. Nostalgia get summoned by songs and odor but not vision because Auditory pathway or olfactory pathway are more ancient and are therefore less filtered by our consciousness.  Their quick access to emotional memory reflects their nature of 'reptilian of brain'. The function of emotional memory in reptiles is directly relating to fight or flight behavior, where memory of fear and satisfaction decides the reward function of decision making.
The emotional tone of a current experience may evoke certain emotional memory due to their similarity in certain properties. In short, these two emotions associates to each other in the memory circuit. 

Hypothesis III : glitch of neural circuits
Deja vu may arise from spontaneous large scale synchronization (analogous to avalanche in complex system ) of association memory between current experience and a set of incomplete memories.

P.52 Maquet concluded that patterns of acturation in the amygdala and other cortical area provided a biological basis for the processing of memory.

P.77 MIT professor Matthew Wilson on mice dream and maze. Mice replay their day time experience of walking in a maze during sleep, according to the sequential firing pattern of place cells. This sequential memory replay may be the origin of latter evolved episodic memory of more intelligent primates.

REM sleep is crucial to consolidate procedual memory by by skiill rehersal, givien us an edge in survivial of the fittest.

P.84 If our emotions are aroused during an experience, our memory of it will be strengthened by that emotional tagging. Extreme emotional arousal, particularly stress increases the concentration of cortisol.


Ultimate Spin Doctor
P.122 
Thanks to brain-imaging studies showing the dreaming brain in action, the limbic system(amygdala, hippocampus,hypothalamus, mammilian body, cingulate gyrus,  entohrinal cortex, etc.), command center for directing emotion and storing strong emotional memory - is directing the dream show. Clearly, a dream is a product of multiple layers of mental activity. The brain is running tests of genetically programmed, survival-related behavior, as well as reviewing recent experience and integrating significant bits of new information with what's already in the memory database in order to update our individual concepts of how the world works and how we fit into it (reinforcement learning.) And having the brain's emotional center in the driver's seat means that the memories that are being singled out most prominently for processing are those that are emotionally charged : anxieties, feelings, of loss, blows to self-esteem, and physical or psychological trauma.  Meanwhile, all of this is taking place under unusual physiological conditions, in which the neuromodulators that help focus attention are in short supply and the brain responds only to its own internally generated signals. --This theory nicely explains why children are more prone to have nightmare than adults -- Their reptilian brain have larger influence on their dream due to late maturation of neocortex.

Brain can create pattern our of any noise (think of brain as as hierarchical pattern completion machine) The brain relentlessly try to create meaning out of whatever it encounters. The brain makes the best sense it can of the barrage of internally generated neural signals it receives, including random neural noise, and pass it to the next part of the system. If a visual image of two dots is created in the visual cortext, the parietal cortex is likely to turn them into a couple of eyes, and then put those two eyes into a face. If that face isn't recognized, the limbic system says 'Ah, that's worrisome; Let's run'. That signal goes to the motor system and the dream plot takes off. explains Antrobus.




Consciousness
According to Micheal Gazaniga's experiment with split-brain patients, the left hemisphere contains a neural system that he labels the 'interpreter', which continually seek to provide explanations for both internal and external perceptions and experiences.'Once you realize the brain is so gullible, you don't want to believe a damn thing it does. It alway tyring to make sense, and in doing so, it fabricates more than just dreams.'  says John Antobus. 'When we encounter a new decision, the emotional brain help us sort out which cognitive strategy to use'

Split patients spin stories, making up reasons to explain our actions. Maybe we make up the concept of consciousness to explain the unity of our self-identity when our attentions drift from one to another things constantly every second.

P.126 'It is the glue that unifies our story and creates our sense of being a whole, rational agent.'

P.183 "Why then should consciousness --whether in waking or dreaming form-- have emerged at all ? It may be because consciousness allows the system to plan future actions, opening up a potentially infinite behavioral repertoire and making explicit memory possible." says Koch. "Consciousness could involve synchronized firing of neurons at the millisecond level, whereas uncorrleated firing can influence behaviors without generating that special buzz in the head that makes us subjectively aware "


Vision is not just a bottom-up process, but also a top-down selection. We can recognize a character by seeing a fraction of it in a unconscious fashion. This pattern completion property is not presented in deep-learning. 


 P.144 Perhaps dreaming generates a wide range of behavioral schema. universal dreams are the equivalent of literary archetypes, akin to stories of jealousy, desire, and revenge that have unfolded from Greek mythology.

P.126 While all animals can learn to avoid food that makes them ill, only humans have the ability to ask why the plant made them sick. This ability to reason give human species a survival edge. Reasoning enable us to generalize the fragmented facts into knowledge. The same capacity to spin narratives in awake state is used to construct the tales that comprise our dreams, and eventually lead us to become psychologically interesting to ourselves as a species.

Epilogue
As the human brain evolved --acquiring the capability for language and for subjective awareness of our emotions.  -- dreaming took on added dimensions that reflected the growing complexity of our won brand of consciousness. As neural circuitry matures and becomes more sophisticated, human dreams ultimately become narratives, with the dreamer as the key player in a true-as-life reality that our brain constructs anew each night, drawing on both recent and long-term memory. Emotionally tagged memory has everything to do with our sense of self.