Philosophy and Neuropsychology:

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Philosophy and Neuropsychology Why Neuroscience
Needs You !
www.neuro.spc.org/philosophy
Vaughan Bell vaughan_at_backspace.org
Outline

• Why neuropsychology ?
• Tools of the trade.
• Philosophy and Neuropsychology in action
• Consciousness
• Free will
• Psychopathology

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Why Neuropsychology ?

• Neuropsychology and Philosophy have aimed to
  answer many of the same fundamental questions.
• Can the workings of the mind be described in
  purely physical terms ? (Descartes)
• What is the difference between internally
  generated ideas and sense experience ? (Locke)
• How much of human cognitive ability can be
  modelled computationally (Searle)
• Even the nature of god... (Neitzsche)
• In fact many of the fundamental assumptions that
  neuropsychologists work with are the result of
  philosophical enquiry (Fodor)
• However, people are complex, and philosophers are
  good at understanding complexity.

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Why Neuropsychology ?

• Philosophers are already working in cognitive
  science.
• As well as well know figures such as Daniel
  Dennet, David Chalmers and Paul Churchland...
• Many other philosophers are working on other
  important (and probably more useful !) areas.

• Philip Gerrans, works on the theoretical
  foundations of neuropsychiatry, the application
  of neuropsychology to mental illness.

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Tools of the Trade

• Neuropsychology uses a wide and varied set of
  tools to obtain data on how people think and how
  this relates to brain function.
• Behavioural studies on healthy people.
• Behavioural studies on brain injured or
  psychiatric patients.
• Neural activation / stimulation.
• Connectionism or Neural Nets
• Although the development of comprehensive
  theories involve, convergent evidence from as
  many sources as possible.

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Experiments on Healthy People

• We can conduct experimental investigations on
  healthy individuals to test hypothesis.
• For example, we may wish to know the extent of
  the brains ability to fill in our blind spot.

x
o
x
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Neural Activation

• Functional imaging allows us to see which parts
  of the brain are active when we perform certain
  tasks.
• The most commonly used methods are fMRI, PET and
  EEG / ERP.
• For example, we may wish to see which part of
  the brain is more active when we view faces
  compared to non-face pictures as in this fMRI
  study.

George et al (1999)
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Neural Stimulation

• We may also wish to stimulate parts of the brain
  to see what effect it has.
• One way of doing this is with TMS or Transcranial
  Magnetic Stimulation.
• It uses a magnetic coil to induce a small
  electrical current in the brain.
• This can temporarily stimulate or inhibit brain
  function in a specific area of the brain for a
  very short period of time.
• We can then ask participants to perform a task
  whilst brain function is being altered to see how
  behaviour is affected.

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Neural Stimulation
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Single Cell Techniques

• Electrodes which are implanted directly in the
  brain have also been used to either
• Record electrical activity from single cells.
• Stimulate areas of the brain directly.
• This is usually done concurrently with
  neurosurgical procedures for obvious reasons !

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Vignal et al (2000)

• Implanted depth electrode to record activity as a
  precursor to neurosurgery for severe epilepsy.
• Also conducted experiment where certain brain
  areas were stimulated.
• Patient report during electrical stimulation to
  the anterior frontal gyrus - the patient was
  looking at the doctors white lab coat
• I see many faces that appear.
• The faces that appear, are they mine ?
• No, a succession of portraits passing by.
• It was not familiar faces ?
• No, one might say of television celebrities,
  faces of people that one might encounter in
  everyday life, a face of a peasant, many many
  faces. It lasted 3 or 4 seconds.

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Connectionism / Neural Nets

• Another method that is increasingly used is to
  build neural nets to model cognitive processes.
• This gives us an idea of how a distributed
  neurally inspired interconnected system may
  process information.
• Once a cognitive process is successfully modelled
  we can then damage the model to simulate brain
  damage or impairment.

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Connectionism / Neural Nets
Output units
Input units
Hidden units
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Studies of Brain Injured Patients
You dont know what youve got till its
gone Joni Mitchell
Damasio et al (1994)
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Studies of Brain Injured Patients

• An area of the brain called the fusiform gyrus
  seems to be specialised for understanding faces.
• We know this largely from evidence from
  prosopagnosic or face blind patients.
• Who may be able to perceive everyday objects, but
  are not able to understand faces when they see
  them.

De Renzi (1986)
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Philosophy / Neuropsychology in Action
Consciousness

• One of the most talked about area in both
  neuropsychology and philosophy is consciousness.
• Particularly, the hard problem, that is how
  physical processes in the brain give rise to
  subjective experience.
• There is no one part of the brain that seems to
  be a control centre for conscious experience.
• Although this is not unusual as almost all
  cognitive abilities arise from the interaction of
  networks that are distributed across the brain.
• However, damage to certain areas of the brain
  seem to affect consciousness is particular ways.

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Blindsight

• Weiskrantz (1986) reported on Patient DB who has
  surgical removal of part of the left occipital
  cortex, resulting in a scotoma or visual field
  cut.

• He reported no conscious experience of any visual
  sensation in the damaged visual field, but could
  successfully localise spots of light within the
  same area when asked to guess.

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Blindsight

• Indeed, work by Goodale and Milner (1992) showed
  that there are two visual pathways.
• One which mediates vision for action..
• ..and one which mediates vision for
  identification.
• Patient DF, who has bilateral occipital lesions
  cannot identify objects but can reach for them
  correctly.
• In Balint-Holmes syndrome the reverse is true.
• This suggests that there is a mechanism of
  consciousness that is being impaired in
  blindsight.
• And that consciousness could be experienced on
  many levels.

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Free Will

• Our phenomenal experience is that we are fully in
  control of our bodies, however neuropsychological
  evidence would seem to suggest otherwise.
• Anarchic or alien hand syndrome and utilisation
  behaviour suggest that after brain damage, we may
  lose conscious control over parts of our bodies.
• In these cases, the patient loses control of one
  of their hands, and may have to use the other to
  fight its action if deemed inappropriate.

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Free Will

• Data from ERP recordings suggests that the
  feeling of free will may be the final point in an
  action, rather than the initial one.
• Recordings from the motor cortex by Haggard and
  Eimer (1999) show why.
• Participants are simply asked to move whenever
  they feel the need.

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Psychopathology
I think therefore I am Rene Descartes

• In Cotards Delusion patients may deny the
  existence of the external world and believe they
  are dead.
• In effect they believe, I think but I am not.
• One day I went out for a walk, right round town
  and ended up at my mother-in-laws and said to
  her Im dead and started stabbing my arm to try
  and get some blood out. It wouldnt bleed so I
  was saying Look, I must be dead - theres no
  blood.
• This would seem to be a fundamental reasoning
  error, however the exact cause of such delusional
  beliefs is unclear.
• Such patients may perform perfectly normally on
  logical reasoning tests, although may be impaired
  on tasks involving the assessment of what is
  adequate data.

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Psychopathology

• And if we say that a patient has a delusional or
  pathological belief
• We first need to know exactly what constitutes
  belief.
• And this is the major philosophical problem in
  psychopathology.
• The question of what can be considered normal
  functioning.
• In this field, philosophers, psychologists and
  psychiatrists are pooling their skills to
  understand the nature of mental illness.

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Conclusion

• Modern neuroscience is a complex field which
  deals with some fundamental questions for the
  benefit of science and society.
• Philosophy has had exactly these aims for
  thousands of years.
• Philosophers can enrich their arguments with data
  coming from neuropsychology.
• As well as providing insightful analysis which
  can provide cognitive science with drive and
  direction.