BSIE 2010: Session 11

Brain, Science, and Inquiry-Based Education K-12 Summer Institute 2010

 

  Session 11

The Brain as a Distributed System, and a Second Loop

Picking up  from yesterday

Our brain is very different from one another and the brain is always in a process of changing. We tend to learn more when we are active and engaged learners. That's why as a teacher it is important to put our maxiumum effort to make the student active ... Shoshana

if enough people walked on a certain area of grass, a new path will be form.  The brain forms new pathways with different experiences/thoughts/inputs.  The pathway becomes "stronger" with the repetition of these experiences/thoughts/inputs" ... Regina Toscani

 

The brain as an empirical inquirer - Loop 1

An ongoing conversation between the brain and the outside world involving expectation ("summary of observations") output, somewhat random,  (trying something out, "making new observation") input ("new observation") Learning from difference ("conflict") between expectation and input "Keeping students in vacillating state of equilibrium" ... Joyce Going on all the time, largely unconscious ("without thinking"), beginning at birth How Babies Think, Alison Gopnick, Scientific American, July 2010 Active learning more effective than passive learning (eg sudoku)

The "real" nervous system - an input/output box consisting of interconnected input/output boxes?

 

	photo from Kemali and Braitenberg, Atlas of the Frog Brain, Springer-Verlag, 1969

Caudal to rostral sequence of "boxes" of "central nervous system" originates in neural tube development, is commmon to all vertebrates

(will defer to later discussion of invertebrates, variations among vertebrates)

Each box in turn (somewhat arbitrarily) subdividable into smaller boxes (with some differences among vertebrates, to return to)

And those ... yes, "its boxes all the way down"

• dorsal medulla, cerebellum
• ventral medulla
• forebrain
• spinal cord

The smallest box: neurons everywhere

Invertebrate nervous systems also have neurons, but differently arranged - makes sense?

Neuron as common, smallest box and as input/output element, connected to other boxes

• Cells, like other cells, but specialized to receive/process transmit "information" (as opposed to matter or energy)
• Size scale - tens of microns (10-6) meters)
• Larger boxes must differ in how smallest interconnected
• Relevance of numbers? enough to "account for all the uniqueness that exists among people"? ... 1012exp1012 possible nervous systems?
• Differences between people, differences between organisms due to .... not building blocks but assembly (architecture)
• Need to know how neurons work - to return to

Can use boxes->boxes ... ->boxes(neurons) to show that larger boxes interconnected, in relatively specific ways (anatomical specificity) and to rigorously specify "input" and "outputs" of largest box ... nervous system itself

• grey matter (soma, dendrites, pre-synaptic terminals, neuropil) vs white matter (bundles of axons, tracts)
• central vs peripheral nervous system (some ganglia, but largely axon bundles
• output elements of nervous system (motoneurons, plus) = neurons with axon terminating outside nervous system
• input elements of nervous system (sensory neurons, plus) = neurons with receiving surface (dendrites) outside of nervous system
• everything else = interneurons
• numbers/proportions: more reason to think of ns as "semi-autonomous"

So ... at least parts of our box within box model real ... and helps define "input" and "output" more rigorously

Implies: different regions on brain, different brains, different behaviors largely because of different assemblies of similar elements ("architecture")

 

Topographic organization - anatomical specificity (input and output locations)

Outputs - (myotomes)

• Motoneurons located at levels of neuraxis related to location of muscles controlled
  • spinal AND cranial motor nuclei/nerves
• Each motoneuron activates only one muscle
• Implications:
  • "action" is not one output but pattern of activity across lots of them - "motor symphony"
  • source of lots of additional variation in behavior
  • lots of outputs/nervous system involved in any "action", is "distributed" characteristic
  • need to understand how patterns of activity created, parts coordinated

Inputs -  (dermatomes)

• Sensory neurons terminate at levels of neuraxis related to location of receptors
  • spinal AND cranial ganglia/nerves/terminal zones
• Implications
  • "sensation"/"perception" not one input but pattern of activity across lots of them (across modalities and, as will be seen, in one modality - another "distributed" characteristic
  • need to understand how inputs combined
  • thought = pattern of activity across lots of neurons

For additional information: central nervous system - regional neuroanatomy peripheral nervous system overview Sympathetic/parasymaphetic systems Enteric nervous system cranial nerves/sensory ganglia/motor nuclei spinal nerves/sensory ganglia/motor nuclei

 

 

 

 

 

 

Usefulness of the interconnected box model and ... another box?

• Capabilities of spinal cord
• Quadriplegia (slightly better) - relevance of topographic organization
  • Christopher Reeves and ... , from NIH
• The "I-function"

 

Observations "surprising", but have to be accepted - Issue is "how to make sense of them"

Two kinds of behavior ("reflex" versus something-else) intuition probably not useful

• Spinal cord capable of very sophisticated activity
• Brain capable of quite unsophisticated activity
• Distinction between "reflex" and other things?

Break problem down into components, see what actually difficult/suprising (good general principle in science)

 

• "foot withdraws when irritated" - spinal cord capable of sophisticated activity on own
  • is ok ... given topography and "physical contiguity principle ("PCP")

• "person doesn't say ouch when foot irritated" - behavior frequently depends on linking paths within nervous system
  • is ok ... given topography and "physical contiguity principle ("PCP")

• "person doesn't move foot when hearing (or reading) request to do so" - behavior frequently depends on linking paths within nervous system
  • is ok ... given topography and "physical contiguity principle ("PCP")

• "person says foot irritation not felt/experienced" - behavior frequently depends on linking paths within nervous system
  • is ok ... given topography and "physical contiguity principle ("PCP") AND ..
  • "behavior" can occur without it being experienced by the behaving organism AND ...
  • neuronal circuitry adequate to support "feeling/experiencing" (I-function) is in the brain (spinal cord not needed for this function)

   

• Where is Christopher Reeves? Is he paralyzed? Does he feel pain? - has to do with "mind", "self", "soul", "personality", "consciousness" ?
  • words requiring redefinition in light of new experiences/observations?

 

 

Ascending somatosensory pathways Descending motor pathways   Action (and perception) as problems of patterns of activity (thinking?) Behavior as dependent on internal communication among boxes I-function as a distinct box I-function is not necessary for behavior dependent on other boxes for access to input and influence on output necessary/helpful in thinking about meanings of "paralysis", "pain"?, "choice"?

Brain a distributed system, works by interaction/conversation among boxes

 

No one in charge, non-hierarchical, coordination by conversation Emergent systems Checks and balances Relevance for classroom - Emergent pedagogy (open-ended transactional inquiry, co-constructive dialogue Multiple selves is a feature of all of us First Person Plural, Paul Bloom, Atlantic, November 2008 Plural Selves, kgould

 

 

 

 

 

 

 

 

 

The bipartite brain and a second loop (conversation between unconscious and conscious, "reflection")

 

Uncovering the cognitive unconscious - an informed guesser, observations as constructions

• The blind spot
• Visual illusions
• The color problem and "reality"
• Perception as construction

Reflection - learning to use a conversation between the cognitive unconscious and the I-function, story teller

Being skeptical, being creative