Neuro 95: Foundations of Neuroscience History

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Neuro 95Foundations of NeuroscienceHistory
Philosophy Module

• Brian Keeley
• Philosophy, Pitzer College
• Office Broad Hall 107

Dion Scott-Kakures Philosophy, Scripps
College Office Humanities Bldg 215
Lecture 5
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Bechtel Mundale
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Multiple Realization, again

• This paper is a direct assault on the concept of
  multiple realizability. They think the best
  response to this worry is simply to deny it, in
  fact, occurs in any robust or interesting sense.
  According to them, it certainly doesnt have any
  important effect on how real neuroscience is
  done.
• According to BM, real neuroscience is done
  comparatively, and comparative neuroscience is
  not hampered by MR in the way functionalists
  worry.

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Comparative Neuro.

• If the gloomy implications of multiple
  realizability were to be taken seriously, one
  would not expect results based on comparative
  neuroanatomy and neurophysi-ological studies to
  be particularly useful in developing functional
  accounts of human psychological processing (p.
  178) (But this is far from the case, in fact,
  they argue).

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Korbinian Brodman

• Cytoarchitectonics The gain in brain lies
  mainly in the stain use staining and nerve
  tracing techniques to map the brain.
• Different parts of the cortex contain different
  kinds of neurons and areas are connected to one
  another in identifiable patterns.

(1868-1918)
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? Left Lateral Cortex
Right medial Cortex ?
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How were the maps constructed?

• Answer Comparatively.
• Thus, in defending the claim of six different
  layers in cortex, he reports preparations made
  from 55 species ranging over 11 different orders
  of mammal, and presents diagrams from the cat,
  wallaby, kinkajou, and rabbit, as well as the
  human. From these maps he argues that there is
  a similarity in the overall patterns of
  parcellation, constancy in broader regions
  across species, and persistence of individual
  areas (181).

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Shows that Brodman is not unusual

• Use of lesioning studies and stimulation studies
  ALSO work together comparatively to figure out
  how the brain works
• Dion talked a bit about Ferriers lesion work
  (and Galls thoughts about it) earlier.

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Wilder Penfield

• Direct brain stimulation In patients requiring
  brain surgery, electrically stimulate the
  cortical surface and see how the patient
  responds.
• Important technique still used today in order to
  identify and spare the more crucial brain regions
  during brain surgery.

(1891-1976)
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Penfields Homunculus
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Where we stand today
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So, why were we ever taken in?

• Assume for a moment that BM are correct. If they
  are, they owe us an explanation of why so many
  were so taken in by this multiple realizability
  argument in the first place.
• Their answer, we were fooled by an
  easy-to-overlook grain-size difference.

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So, why were we ever taken in?

• Usually, when we talk about high-level,
  psychological functions, we use rather gross,
  general terms. And, when we talk about
  neurobiology, we tend to use rather fine-grained
  terms.
• So, we might talk about hunger leading to
  food-seeking and consumption behavior (notice
  how general that is). But when we talk about
  neurons, we notice all the little differences in
  the tiniest details.
• BM argue that if we hold grain-size constant
  multiple realizability goes away.

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Zawidski Bechtel
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Different model of reduction

• The story here is reductionist, but isnt the
  DN-model of reduction.
• They endorse an approach that looks for
  mechanistic explanation through decomposition and
  localization.
• That is, reductive explanation is not about
  scientific laws
• its about identifying mechanisms, figuring out
  how those mechanisms work (decomposing them), and
  then figuring out where they happen (localization)

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Three Strands

• ZB see that Galls legacy lives on in three
  different strands of contemporary research
• Direct localization of whole mental functions
  (found in Fodors modularity theory)
• Top-down functional decomposition (much cognitive
  psychology, AI, and many philosophers, such as
  Lycan Sterelny)
• Interactive decomposition localization
  (cognitive neuroscience)
• (Hint its the third strand that they think is
  closest to the mark)

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1) Direct localization

• Closest to the spirit of Gall
• Sit down and identify mental phenomena (language,
  memory, etc.)
• Figure out how they are related to one another
• Identify where they happen in the brain.
• (Notice you do your psychological theorizing
  first, and only then try to find those things in
  the brain, if at all)

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2) Top-down functional decomposition

• This methodology takes mental functions and
  chops them up into parts that together explain
  the function.
• For example, language comprehension
• You need a mechanism to differentiate the sounds
  (phonology), and another to identify how the
  sounds go together as words, and something figure
  out the meaning of words (semantics) and
  something else to figure out the grammatical
  clues, and so on.

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2) Top-down functional decomposition

• But, its top-down you start with the mental
  phenomenon and then divide it up.
• Neuroscience may have little or nothing to do
  with it.

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3) Interactive decomposition

• This is like top-down functional decomposition,
  in that you take mental tasks and divide them up
  into their component sub-tasks.
• However, unlike top-down functional
  decomposition, here it is done in consultation
  with neuroscience (Churchlands Coevolution?)
• The result is a psychological theory of mental
  phenomena that coheres well with the findings of
  neuroscience
• Hence, its status as a reductionist theory.

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3) Interactive decomposition

• The example they discuss at length is recent work
  in the hot-topic research area of attention
• The cocktail party effect. Notice how quickly
  you tune in when somebody in another part of
  the room mentions your name.
• Thats attention at work.
• BZ discuss recent work in this area in detail,
  showing how the different theories of attention
  have interacted with one another.
• They believe it exemplifies their approach.

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3) Interactive decomposition

• Particularly interesting is the shift from a
  bottle-neck conception of attention (which came
  from a top-down approach) to a spot-light
  conception (which came from brain studies).
• They describe the various studies and theories
  much better than I can, but perhaps there are
  questions about any of this?