Ruiz Muñoz, M. J. 1, 2 , Colzato, L. 2 , Bajo, M. T. 1 , van den Wildenberg, W. P. 3 & Hommel, B. 2
1 Department of Psychology. Granada University. Granada, Spain
2 Cognitive Psychology Unit, and Leiden Institute for Brain and Cognition. Leiden University. Leiden, The Netherlands
3 Amsterdam Center for the Study of Adaptative Control in Brain and Behaviour, Department of Psychology. University of Amsterdam. Amsterdam, The Netherlands
Catha Edulis is a plant grown in the countries around the Red sea and Eastern Africa. Its leaves are chewed by local people for their stimulant properties. Khat leaves contains alkaloids called cathine and cathinone. These active ingredients are similar in pharmacological activity and structure to amphetamines. We investigated whether khat users show detrimental performance in updating of Working Memory, Inhibitory control and Mental Flexibility as measured by N-back task, Stop Signal task and Global-Local task respectively. We found khat users showed longer SSRTs in the Stop-Signal task than khat-free participants reflecting general slowing of inhibitory processes and indicating lower levels of inhibitory efficiency. Similarly, regular users showed a significant increase in the error rates of the N-back task, suggesting that long-term regular khat use is associated with impairments in WM updating. So this result shows an impairment in monitoring of information. This deficit in monitoring could be decisive to adapt and update the cognitive system in response to changing environments. Finally, Khat users had increased switching costs in the Global-local task, suggesting that recreational use is associated with impaired cognitive flexibility.