UNIVERSITY OF MALTA
LIFE SCIENCE RESEARCH SEMINARS
Web: http://events.um.edu.mt/scisem/
Email: scisem@um.edu.mt
Abstract form
Title: Cognitive performance (on Kamin Blocking and Latent Inhibition) in
an opiate and cocaine-using population
Presenter: Martina Castillo
Contact address: 54, St. Margaret Street, Sliema
Tel:
Fax:
Email: martina.castillo@gov.mt
Presentation date: 8th April, 2008
Abstract
Drug addiction has been rampant on researchers’ agendas for the last few decades across the
spectrum of scientific disciplines. In particular, neuroscientists together with learning
theorists have been examining the effect of exogenous drug actions (psychoactive
substances) on learning processes.
This study involves measuring performance in Kamin Blocking (KB) and Latent Inhibition
(LI) via specifically designed experimental tests. KB and LI refer to two cognitive domains
dealing with associative learning and the ability to perceive and learn new stimuli. The
underlying mechanism involved in the process of learning involves the dopaminergic (DA)
pathway, namely projections from the midbrain (the ventral tegmental area and the
substantia nigra) to the nucleus accumbens and to the cortex (Hyman, 2005). High levels of
dopamine however are associated with a deficit in cognitive functioning. In fact cognitive
deficits have been extensively correlated in schizophrenic persons and normal persons with
high levels of schizotypy (both associated with high extracellular dopamine concentrations)
(Moran, Al-Uzri, Watson, Reveley, 2003).
Cocaine has a direct effect on the brain by elevating extracellular dopamine levels.
Similarly, exogenous opiates (heroin, methadone) also raise dopamine, however in a more
indirect manner and involving modulatory neurotransmitter systems.
In its final phase, the study is assessing cognitive performance in a sample of heroin addicts
on methadone treatment; current cocaine addicts as well as a control group consisting of
non-using individuals. Apart from assessing Kamin Blocking and Latent Inhibition,
severity of addiction, distal variables (including affect and socioeconomic factors) are taken
into consideration.
Hyman, S.E. Addiction: A Disease of Learning and Memory. American Journal of Psychiatry 162 (2005);1414–
1422
Morana, P.M., Al-Uzrib, M.M., Watson, J., Reveley, M.A., Reduced Kamin blocking in non paranoid
schizophrenia: associations with schizotypy. Journal of Psychiatric Research 37 (2003); 155–163