Melzack & Katz, Pain. Part 12f: Surfacing out of basal ganglia

The paper, Pain

Most recent blogposts:

Part 12: Action! 12b: Examining the motor system, first pass. 12c: Motor output and nervous systems - where they EACH came from Part 12d... deeper and deeper into basal ganglia Part 12e: Still awfully deep in basal ganglia

SEE ALL PREVIOUS BLOGPOSTS IN THIS SERIES LISTED AT THE END

OK, we're turned around now and heading back to the Melzack & Katz river we had been traveling on, but I thought, since it'll be a few days before we get back to where we first turned off, I'll keep posting info Peggy Mason provides in her wonderful text, Medical Neurobiology, written in easy page-turner style. [I gotta say, I was up in the middle of the night reading about basal ganglia, so it's not an easy topic to let go of, obviously.] 

Here is a great sample of her clarity, a summary after about 20 pages of detailed explanation about how info gets in to basal ganglia, how its handled, how it's allowed through: 

"Every time we act, the cerebellum and basal ganglia, the two great loops in the brain, receive information about the action generated from cortex. Both structures communicate indirectly with the motor hierarchy, only affecting motor neurons and motor interneurons via a circuitous route. Both structures receive at least an order of magnitude more information than they send out to target structures, making them processing bottlenecks that reduce an overwhelming confusion of conflicting input to a concise and decisive winner-takes-all output. Further, the basal ganglia are critical to, and the cerebellum may influence, many nonmotor functions, processing thoughts, emotions, and memories, all of which, of course, ultimately influence movements. Even the functions of the two, in sequencing movements and learning associations, overlap. 

 
" In marked contrast to the case with the cerebellum, the basal ganglia do not receive spinal input. Instead, input to the basal ganglia comes from virtually all areas of the cerebral cortex, as well as from subcortical regions that can themselves direct movement, such as the superior colliculus. Whereas some efference copy input to the cerebellum arises from spinal border cells, efference copy input to the basal ganglia comes from cortical and brainstem motor control centers exclusively. Thus, the cerebellum receives information about muscle contractions, whereas the basal ganglia only receive input about movements and actions. Sensory input to the cerebellum comes from the spinal cord and represents the sensory consequences of movement termed reafference. In contrast, neurons in cortical and brainstem regions interpret and then present sensory information about the world to the basal ganglia. Consider the sequential versions of an action, from motivation and selection of a goal in the prefrontal cortex to action in motor cortex, to movement in the ventral horn interneurons, and muscle control in the α- motoneurons. The basal ganglia receive motor information biased toward goal selection and action whereas the cerebellum receives information biased toward movement and muscle contraction.  

"The cerebellum smooths out movements, important and trivial ones alike, whereas the skeletomotor loop of the basal ganglia ensures that salient actions take priority over automatic, mundane ones. The nonmotor functions of the cerebellum and basal ganglia may similarly diverge with the cerebellum focusing on automatisms and the basal ganglia on matching motivation, thought, emotion, strategy, and movement to urgency and circumstance.  

"Both the cerebellum and basal ganglia support operational learning. The cerebellum associates sensory input with motor output, so that a set of inputs related to the body and the outside world - an entire sensory gestalt - becomes associated with a particular movement. In contrast, the basal ganglia associate self-generated actions with their consequences, biasing present and future selection of actions toward previously rewarding ones. Ultimately our actions are those dictated by the cerebellum and the basal ganglia, incorporating influences from the sensory world as well as from our cognitive, motivational, and emotional states." p. 579-80:

All the bolds are hers. 

Here are the bits that really caught my eye: 

Processing bottlenecks

"...processing bottlenecks that reduce an overwhelming confusion of conflicting input to a concise and decisive winner-takes-all output."

If both basal ganglia and cerebellum receive "at least an order of magnitude" more information than they let through, then that is some heavy darn braking they are required to do! How is all the other info (that doesn't get through) handled? Is it dampened or deconstructed or recycled somehow?

Basal ganglia and nonmotor function

"the basal ganglia are critical to...many nonmotor functions, processing thoughts, emotions, and memories, all of which, of course, ultimately influence movements."

This kind of puts them in the middle of not just the physical brain, but of everything the brain "does." In the middle of the neuromatrix, not just off to the right of the diagram. 

Cerebellum and basal ganglia are a team

"Even the functions of the two, in sequencing movements and learning associations, overlap."

So nice they work together so well. I suppose that will happen over 500 million years - kinks get smoothed out quite a bit.

Projections to basal ganglia

"basal ganglia do not receive spinal input"

They really do only work with brain input, none from the "body." 

Note to self - study up on superior colliculus. It has something to do with reflexive vision and output to neck muscles or something.. handy if something (like a predator sliding through the grass) happens to catch the eye.

Culture, habit formation

"neurons in cortical and brainstem regions interpret and then present sensory information about the world to the basal ganglia."

They only receive info that has already been "milled" by the rest of the brain. The rest of the brain has already been programmed by "culture." 

"The basal ganglia receive motor information biased toward goal selection and action"

Unless the patient can change his or her "mind" about moving, the basal ganglia won't receive any novel stimuli. Ever. 

"The cerebellum smooths out movements, important and trivial ones alike, whereas the skeletomotor loop of the basal ganglia ensures that salient actions take priority over automatic, mundane ones. The nonmotor functions of the cerebellum and basal ganglia may similarly diverge with the cerebellum focusing on automatisms and the basal ganglia on matching motivation, thought, emotion, strategy, and movement to urgency and circumstance.  

The implications of this whole paragraph are HUGE.

We (people) are domesticated primates/animals, not wild free ones tuned to every nuance of our environment. Not that I'm not grateful for that. But it likely means not as much fresh input as might be desirable, from a basal ganglia standpoint. 

"The cerebellum associates sensory input with motor output, so that a set of inputs related to the body and the outside world - an entire sensory gestalt - becomes associated with a particular movement."

The cerebellum would totally turn us into robots if it could. 

"the basal ganglia associate self-generated actions with their consequences, biasing present and future selection of actions toward previously rewarding ones."

The basal ganglia operate on information that is already "old" by the time it reaches them. They are biased toward whatever worked before. I see Tim Conway banging his head against the wall in some Carol Burnett skit, having completely missed the doorway. Yet basal ganglia are our only way out of movement dilemmas, it seems. Movement bottle neck, for sure. 

Implications

So... what does this mean for us, as therapists? 

What does it mean as part of a neuromatrix model? 

What does it mean for our patients whose brains have "decided" not to let them move certain parts in certain ways, by dishing them "pain" if they try? 

What does it mean in terms of a painful experience of movement? 

By the sound of it, the critter brain is pretty much in charge of everything. Clearly (to me at least) therapy involves:
1. setting up a benign context, non-noceboic, containing only the clear desire to be of help

2. pain explanations to feed the cognitive parts of the human brain, which I see as desperate for answers, which get people thinking about their own brains
3. some sort of human primate social grooming (to provide innocuous and at the same time, novel interesting sensory input)

4. the patience to wait for improved output to emerge all on its own. From the critter brain itself.

Simple, but not easy...

See Barrett Dorko for more on "movement secondary to thought." 

"Ideomotion has two purposes - it expresses us, and it makes us comfortable."

Here is a short youtube video in which he explains how he treats the movement outflow bottleneck system, helps it change its "mind" about what kinds of movement it will permit. 

DORKO'S DIAMONDS 

YouTube series featuring Barrett Dorko PT

......

Previous blogposts

Part 1 First two sentences Part 2 Pain is personal Also Pain is Personal addendum., Neurotags! Pain is Personal, Always.

Part 3a Pain is more than sensation: Backdrop Part 3b Pain is not receptor stimulation Part 3c: Pain depends on everything ever experienced by an individual

Part 4: Pain is a multidimensional experience across time

Part 5: Pain and purpose

Part 6a: Descartes and his era; Part 6b: History of pain - what’s in “Ref 4”?; Part 6c: History of pain, Ref 4, cont.. : There is no pain matrix, only a neuromatrix; Part 6d: History of Pain: Final takedown Part 6e: Pattern theories in the history of pain Part 6f: Evaluation of pain theories Part 6g: History of Pain, the cautionary tale. Part 6h: Gate Control Theory.

Part 7: Gate control theory has stood the test of time: Patrick David Wall;  Part 7b: Gate control: "The theory was a leap of faith but it was right!"

Part 8: Beyond the gate: Self as mayor Part 8b: 3-ring circus of self Part 8c: Getting objective about subjectivity

Part 9: Phantom pain - in the brain! Part 9b: Dawn of the Neuromatrix model Part 9c: Neuromatrix: MORE than just spinal projection areas in thalamus and cortex Part 9d: More about phantom body pain in paraplegics

Part 10: "We don't need a body to feel a body." Part 10b: Conclusion1: The brain generates its own experience of being in a body Part 10c:Conclusion 2: Your brain, not your body, tells you what you're feeling Part 10d: Conclusion 3: The brain's sense of "Self" can INclude missing parts, or EXclude actual parts, of the biological body Part 10e: The neural network that both comprises and moves "Self" is (only)modified by sensory experience
Part 11: We need a new conceptual brain model! Part 11b: Intro to a new conceptual nervous system Part 11c: Older brain models just don't cut it Part 11d: The NEW brain model!