Introduction

There are at least two ways in which cognitive impairments might contribute to drug misuse and drug dependence or addiction. Cognitive impairments, perhaps involving heightened impulsivity, may facilitate drug-seeking behaviour but also undermine the extent to which drug users are able to assimilate and benefit from treatment programmes that often have strong educational and cognitive components (McCrady and Smith 1986; Majewska 1996).

Recent research has seen a rapid expansion of the investigation of neurocognitive deficits in drug abusers and on the relationship between these deficits and neurochemical, morphological and functional pathologies associated with chronic drug use. This research is now able to call upon advances from several areas of cognitive neuroscience, encompassing neuroanatomy and molecular pharmacology (Gurevich and Joyce 1999; Ongur and Price 2000), psychological theory concerning the nature of motivated action and reinforcement mechanisms as they relate to drugs of abuse (see Altman et al. 1996; Everitt et al. 2001 for reviews), and imaging methodologies (Breiter et al. 1997; Volkow et al. 1997; Gollub et al. 1998; Liu et al. 1998) and event-based electroencephalography (McKetin and Solowij 1999) that allow investigation of the physiological correlates of cognitive and emotional activity in the brain. Moreover, the scope of this research is expanding with the preliminary investigation of neurocognitive deficits associated with drugs, such as ketamine, whose potential for abuse is only recently becoming apparent (Curran and Morgan 2001).