Sunday, February 08, 2015

AROUSAL: The Control Central Domain

A sound board lets the engineer manage a zillion small modulations.

If I’m understanding properly, the arousal domain of neural pathways (not just in the brain but in the whole body and inevitably forced to interface with the environment -- I mean, that's what it FOR) is the sound board system, not the little monitoring dashboard but the enormously complex systems that actually turn the other systems on and off.  Accelerator and brake if you like the automobile metaphor better, though that's way over-simplified.  Arousal systems are meant to keep track of "computer-management" levels of adjustment to do what's necessary to maintain homeostasis and its balance with intention, which is the conscious part, the guy in the ball cap.

Though I don't entirely trust Wikipedia, I'll quote the mystery expert who wrote the following entry.  I left the more technical links.

Arousal is a physiological and psychological state of being awake or reactive to stimuli. It involves the activation of the reticular activating system in the brain stem, the autonomic nervous system and the endocrine system, leading to increased heart rate and blood pressure and a condition of sensory alertness, mobility and readiness to respond.

There are many different neural systems involved in what is collectively known as the arousal system. 

"Arousal" is a bit of a misnomer, since the system also turns OFF.

Five major systems originating in the brainstem, with connections extending throughout the cortex, are based on the brain's neurotransmitters, acetylcholine, norepinephrine, dopamine, histamine, and serotonin. When these systems are stimulated, they produce cortical activity and alertness. 

The Noradrenergic system is a bundle of axons that originate in the locus coeruleus [The locus coeruleus is a nucleus in the pons (part of the brainstem) involved with physiological responses to stress and panic.]   It ascends up into the neocortex, limbic system, and basal forebrain. Most of the neurons are projected to the posterior cortex which is important with sensory information, and alertness. The activation of the locus coeruleus and release of norepinephrine causes wakefulness and increases vigilance. The neurons that project into the basal forebrain impact cholinergic neurons that results in a flood of acetylcholine into the cerebral cortex. 

The Acetylcholinergic system has its neurons located in the pons and in the basal forebrain. Stimulation of these neurons result in cortical activity, shown from EEG records, and alertness. All of the other four neurotransmitters play a role in activating the acetylcholine neurons. 

Another arousal system is the dopaminergic system which releases dopamine that is produced by the substantia nigra. The neurons arise in the ventral tegmental area in the midbrain, and projects to the nucleus accumbens, the striatum forebrain, limbic system, and prefrontal cortex. The limbic system is important for control of mood and the nucleus accumbens signal excitement and arousal. The path terminating in the prefrontal cortex is important in regulating motor movements, especially reward oriented movements. [Trouble here is related to Parkinson’s.]

The Serotonergic system which has almost all of its serotonergic neurons originating in the raphe nuclei. This system projects to the limbic system as well as the prefrontal cortex. Stimulation of these axons and release of serotonin causes cortical arousal and impacts locomotion as well as mood. 

The last system is the histamergenic system. The neurons are located in the tuberomammillary nucleus of the hypothalamus. These neurons send pathways to the cerebral cortex, thalamus, and the basal forebrain, where is stimulate the release of acetylcholine into the cerebral cortex. All of these systems are very much linked and show similar redundancy. These pathways I've described are all ascending pathways, but there also arousal pathways that descend. 

One example is the Ventrolateral Preoptic area which release GABA inhibitors, which interrupt wakefulness and arousal. Neurotransmitters of the Arousal system such as Acetylcholine and norepinephrine work to inhibit the Ventrolateral preoptic area.

This material is tough to assimilate (learn) and not available to the consciousness anyway, which is a major difficulty in the attempt to reconcile neuronal biology with reflective metaphorical speculation like psychotherapy.  But finally we CAN see the things above in blood tests, fMRI, and even powerful microscopes if you don't mind a seaslug standing in for a human.

Arousal/Modulatory Systems as discussed by RDoC

Arousal/Regulatory Systems: Systems responsible for generating activation of neural systems as appropriate for various contexts, and providing appropriate homeostatic regulation of such systems as energy balance and sleep.

Arousal: Arousal is a continuum of sensitivity of the organism to stimuli, both external and internal.

Arousal facilitates interaction with the environment in a context-specific manner (e.g., under conditions of threat, some stimuli must be ignored while sensitivity to and responses to others is enhanced, as exemplified in the startle reflex).

-- can be evoked by either external/environmental stimuli or internal stimuli (e.g., emotions and cognition),

-- can be modulated by the physical characteristics and motivational significance of stimuli,

-- varies along a continuum that can be quantified in any behavioral state, including wakefulness and low-arousal states including sleep, anesthesia, and coma,

-- is distinct from motivation and valence but can covary with intensity of motivation and valence,

-- may be associated with increased or decreased locomotor activity, and

-- can be regulated by homeostatic drives (e.g., hunger, sleep, thirst, sex).

Circadian Rhythms: Circadian Rhythms are endogenous self-sustaining oscillations that organize the timing of biological systems to optimize physiology and behavior, and health.

-- are synchronized by recurring environmental cues;

-- anticipate the external environment;

-- allow effective response to challenges and opportunities in the physical and social environment;

-- modulate homeostasis within the brain and other (central/peripheral) systems, tissues and organs;

-- are evident across levels of organization including molecules, cells, circuits, systems, organisms, and social systems.

Sleep and wakefulness: 

Sleep and wakefulness are endogenous, recurring, behavioral states that reflect coordinated changes in the dynamic functional organization of the brain and that optimize physiology, behavior, and health. Homeostatic and circadian processes regulate the propensity for wakefulness and sleep.

-- is reversible, typically characterized by postural recumbence, behavioral quiescence, and reduced responsiveness;  [lying down, not moving, not paying attention.]

-- has a complex architecture with predictable cycling of NREM/REM states or their developmental equivalents. NREM and REM sleep have distinct neural substrates (circuitry, transmitters, modulators) and EEG oscillatory properties

-- intensity and duration is affected by homeostatic regulation;

-- is affected by experiences during wakefulness;

-- is evident at cellular, circuit, and system levels;

-- has restorative and transformative effects that optimize neurobehavioral functions during wakefulness


To me it is remarkable how different one “Domain” is from another, even in terms of the way they organize their issues.  This one is almost masked and, like the Wikipedia entry (which was probably written by one of these people) excludes sexual arousal.  Granted, there’s enough to think about here without including sex, but it reinforces the idea that sexual arousal is something detached from ordinary life and the idea that buying services or toys or pills are going to solve the problems of something like confusing sex with violence or confusing the nurturing of children with reproduction-linked sex or an inability to recognize sex partners as human beings (assuming they are.  Fucking sheep is a different problem.  
Do not mess with polar bears.

It's probably overblown and previous to compare climate change to the huge transformation away from the culture in which humans evolved (including neanderthals and some other now-extinct humans) in the evolutionary consolidation, since 4% of our genes seem to be shared with the neanderthals.  Probably the gene-governed behaviors are about these pathways and are now out-of-sync in the same way that North Pole ice melting means the polar bear hunting practices for catching seals don't work now and indigenous coastal fishing villages are sinking into mud for lack of permafrost.  Most of the time-shift misfit doesn't register with us: all the little birds who migrate at the wrong time, all the animal babies produced at a time when there's nothing to eat yet, the insects moving north too much and too soon in the season.

That's also the way our sexual, eating, sleeping, and community arrangements have gotten out of sync.  Culture shift is like climate shift because our reflexes don't match the situations very well anymore.  But it's not as easy for our intentions to figure out which tiny control should be moved or even what we are aiming for:  more loud bass, a slower beat, an inaudible treble, less brass, more strings?  Sorry there's so much metaphor -- it's the neanderthal coming out in me.

Reconstructed Neaderthal.

No comments: