Neuroscience: An ongoing series of Big Questions

Introduction

Studying the brain is complicated to say the least.  The best way is to study it in parts.  The tabs on this page represent a segmented approach the grows more complex as the roman numerals increase.  That is not to say that any segment is easy. There are different levels of analysis at every level. I have names for these levels: Biggest (level of behavior); Big(level of anatomical systems); Small (level of cells); Smallest (level of subcellular structures) and Teeny-Tiny (level of chemical reactions and ion movement).  Every behavior contains Teeny-Tiny elements and events at the subcellular level effect anatomical systems.  So the levels are all interconnected.  

You can see why trying to sort out how the brain works is a such a huge endeavor and is the work of hundreds of thousands of scientists over the past four centuries.  What they each have in common is that they ask a specific question and when it is answered other scientists use it as a foundation on which to ask more questions.  

I got this idea about questions from Dr. Gerald Schneider of MIT in his Open Courseware lecture on Neuroanatomy. Dr. Schneider is an anatomists of some renown.  He begins his courses with a look at the Big Ideas and Big Questions that are at the foundation of Neuroscience. I have added some of my own ideas also.

Big Ideas and Big Questions

QUESTION #1-

HOW DOES THE BRAIN CAUSE BEHAVIOR?

So this was the idea- "If we could understand the brain the perhaps we could understand human behavior." This question had been posed by many scholars across the centuries.  It was Renee Descartes who asked the question in a very precise way...by considering behavior.

Renee Descartes
Reflex arc

EVIDENCE-

Withdrawal reflex or stimulus response was first worked out by Renee Descartes. His analyses was incorrect but he did emphasize connectivity.  Further evidence supplied by dorsal root ganglion  The idea for nerve connectivity was necessary in order to discover the role of individual neurons.

Santiago Ramon y Cajal focused on Neural Pathway, established the Neuron Doctrine and used Golgi stain to reveal individual cells with long projections.

Sir Charles Scott Sherrington, – coined the term “synapse” because neurons are not connected. They do not touch each other...although they are extremely close together.

CONCLUSION

So, looking at specific neuron circuits are involved in movement researchers got more information about the central nervous syste.  They concluded, the certain behaviors elicit reflexive movements. This conclusion led to larger questions ….Is all behavior reflexive? 

QUESTION #2- IF BEHAVIOR IS REFLEXIVE HOW DO HUMANS ACT ‘WILLFULLY?”  

If all behavior is a reflex does that mean that human behavior is not determined  Francoise Magendie.

Why the stimulus and response idea abandoned.

Examining the spinal root that demonstrates neuro-circuitry revealed a specific type of morphology (or design) and placement of cells involved in reflex circuits. This same type of circuitry was not present through out the nervous system.

EVIDENCE

Lamitree stated that the uniqueness of humans differs form animals only in the complexity of behavior.  Did not believe in reflexology  Human Brain is far too complex…More than 10 billion cells just in cerebellum. Between 4k-10k synapes in cortex.

Although too complex to trace reflex arcs between cells there was evidence of regional involvement.

Investigators sought to find “seat of the soul”

Franz Joseph Gall & Phrenology- discovered gray and white matter but incorrectly linked brain function to skull shape. 

Differences in the size of brain area is important in anthropology but functional correlations are not substantiated.

Paul Broca was a neurologist who had patients who had a stroke and subsequent speech impairment. After autopsy Broca defined the damaged area responsible for vocalized speech.  Broca also observed how difficult and diffuse language functions are in the brain. For instance, Wernicke  found that specific brain areas were responsible for decoding speech sounds. This condition is known as Wernicke's aphasia- speech is fluent but comprehension, repetition and naming abilities are hampered. Wernicke discovered a different area of the brain from Broca's region that caused the aphasia. He published a drawing:

Study from dog motor cortices Gustav Fritsch and Eduard Hitzig showed areas devoted to specific function like speech, and in addition the sensory and motor homunculus

This led to study of the “How.” What is the mechanism?  

Vladimir Betz discovered and named the Betz cell which is the longest pyramidal cell. We now knew that different brain cells had distinct morphologies and placements that defined their function.  Structure and Function became key to understanding behavior. 

CONCLUSION  --Brain function is not reflexive but localized. BUT if that is true then,  how do you explain soul if function is localized on brain tissue? This is led to next question……

QUESTION-

 IF THE BRAIN IS IN THE SOUL AND THE BRAIN CAN BE CUT UP- CAN THE SOUL BE DIVIDED? 

This led to Anti-localization of function tradition or Generalized localization of function

EVIDENCE

Pierre Flourens 1824 He found that Certain lesions caused different effects (different lesions resulted in different function) 

Goetz (1826)  Dog lesions studies disturbed higher function demonstrated that function was regional but was considered not “scientific” enough

Karl Lashley used more of scientific method. He used histological methods to show the accuracy of the lesions. He concluded that as the area of lesion increased the number of errors made by the rats in the maze also increased.  He led to his theory of mass action and  is called equipotential  He wrongly concluded that localization exists throughout the brain and is used for all brain function.

MIT investigators in 1965  Gross repeated Lashley experiment and saw that multiple areas were invovled because maze navigation requires many numerous skills.

Hunter, a contemporary of Lashley argued that the rat maze behavior was complex even then but he was often argued down

Other studies with sexual behavior in rats showed that male and female rats behaved differently. So researchers have to know about behavioral factors and relate that to anatomy. We also know that hormonal and chemical activities help determine brain function.

CONCLUSION The brain is not the soul.  The soul emerges from brain matter that is localized by the physiological substrate. The biological actions of the physiological substrates dictate behavior. We still don't really understand much about the soul!! But we do no more and more about the biological substrates necessary for behavior

We soon learned that the substrates are connected and have  input outputs and intermediary pathways.

Luria concluded that mental functions cannot be localized to a narrow bed of cortex in isolated cell groups. While it is possible to disturb the function the greater complexity is made up of connections. Function is therefore made from complex connections BETWEEN regions.

CONCLUSION McKaie- The brain does not think or decide but provides the NEURAL CORRELATES IN THEIR PHYSICAL DIMENSION.  Thus providing the basis for deciding, feeling, believing hoping etc..

REVIEW- The history of neuroscience resolves around Big Questions.

Is behavior a circuit and reflexive?

Is behavioral function localized to a specific brain area and if so, what about the soul?

CURRENT BIG QUESTIONS: 

How do the neural correlates work to produce a given behavior?  

When something goes wrong in the neural correlates how can they be repaired so that function is restored? 

Can the function of neural correlates be copied and  reproduced in a machine.  

Can machines be taught to think?  Can machines be taught to move?  Can machines be taught to feel?