The Psychophysics Psyber Lab




John Podd's Home Page

Current Research

I have been working with Parkinson's disease people for the last few years. Parkinson's disease slowly destroys a midbrain nucleus called the substantia nigra, the main dopamine-producing area in the human brain. Most PD symptoms are motor but we have been interested in assessing cognitive functioning, especially recognition memory. The prevailing view is that recall deficits occur but not recognition deficits. We did a lot of preliminary work before the major study which first assessed recognition deficits in earlier work by meta-analysis; we found a small but seemingly real deficit. We then designed sensitive tests to demonstrate recognition memory deficits using both verbal and pictorial stimuli. The methodology was that associated with signal detection theory.

The other neuroscience line or research looks at various "substances" that might adversely affect the CNS. So, for instance, we have run several studies (again TSD methodology) to find out if weak, extremely low frequency magnetic fields can affect human behaviour. We have concentrated on visual duration discrimination in a 2AFC design using LED flashes (very fast rise-fall time).

Some studies seem to show that magnetic fields can affect both accuracy and reaction time. However, when we aggregated the results from several studies the overall effect seems to be zero. That made me feel very good because I could never figure out how the tiny amounts of energy in the magnetic fields used could perturb an ion, let alone anything bigger. Apart from further investigations of some amplification system that could cause the fields to perturb a biological system (like stochastic resonance) I do not intend to do anymore studies with humans.

I have now joined forces with a biologist and we are looking at the effects of these magnetic fields at the cellular level. We have obtained some interesting results, but again, nothing that we can reliably replicate.

Linked to this research is some work we are doing on the effects of mercury poisoning on the CNS, and the effects of nuclear radiation on both the CNS and on white blood cells.


  • Galvin, S. J., Podd, J. V., Drga, V., and Whitmore, J. (2003) Type 2 tasks in the theory of signal detectability: Discrimination between correct and incorrect decisions. Psychonomic Bulletin & Review, 10 (4), 843-867.


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Last updated 08 Nov 2009 04:37 PM

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