Philosophy and Neuropsychology: Why Neuroscience Needs You !

1. Philosophy and Neuropsychology: Why Neuroscience Needs You ! www.neuro.spc.org/philosophy Vaughan Bell vaughan@backspace.org Outline • Why neuropsychology ? • Tools of the trade. • Philosophy and Neuropsychology in action: • Consciousness • Free will • Psychopathology

2. 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.

3. 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.

4. 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.

5. 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 brain’s ability to fill in our blind spot. x o x o

6. 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)

7. 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.

8. Neural Stimulation

9. 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 !

10. 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 doctor’s 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.

11. 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.

12. Activation Error Propagation Connectionism / Neural Nets Output units Input units Hidden units

13. Studies of Brain Injured Patients “You don’t know what you’ve got till it’s gone” Joni Mitchell Damasio et al (1994)

14. 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)

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. Psychopathology “I think therefore I am” Rene Descartes • In Cotard’s 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-law’s and said to her “I’m dead” and started stabbing my arm to try and get some blood out. It wouldn’t bleed so I was saying “Look, I must be dead - there’s 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.

21. 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.

22. 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.