Chronic use of cannabis and poor neural efficiency in verbal memory ability
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The endogenous cannabinoid system is sensitive to the introduction of exogenous cannabinoids such as delta-9-tetrahydrocannabinol, which are known to impact upon memory functioning. We sought to examine the impact of chronic cannabis use upon memory-related brain function via examination of the subsequent memory effect (SME) of the event-related potential (ERP).
The SME is predictive of recall outcome and originates in structures that are dense with cannabinoid receptors (hippocampus and parahippocampus). The SME and performance on a verbal memory task were compared between 24 cannabis users (mean 17 years of near daily use) in the unintoxicated state and 24 non-using controls. The task involved the presentation of word lists, each with a short delay before recall. ERPs were recorded during encoding and later averaged by outcome (correctly recalled/not recalled).
Cannabis users showed poorer recall and altered patterns of SME activation: specifically, attenuation of the negative N4 and an increase in the late positive component. Duration of cannabis use and age of initial use correlated significantly with SME amplitudes. A longer history of use also correlated with greater recall that was related to N4 expression.
The results indicate that relative to non-using controls, chronic users of cannabis have altered memory-related brain activation in the form of dysfunctional SME production and/or poorer neural efficiency, which is associated with deficits in memory recall. Greater alteration was associated with a longer history of cannabis use and an earlier onset of use. Neuroadaptation to the effects of chronic exposure may additionally play a role.
KeywordsCannabis ERP Subsequent memory effect Neural efficiency Neuroadaptation N4
- Felder CC, Nielsen A, Briley EM, Palkovits M, Priller J, Axelrod J, Nguyen DN, Richardson JM, Riggin RM, Koppel GA, Paul SM, Becker GW (1996) Isolation and measurement of the endogenous cannabinoid receptor agonist, anandamide, in brain and peripheral tissues of human and rat. FEBS Lett 393:231–235CrossRefPubMedGoogle Scholar
- Nelson HE, Willison JR (1991) National adult reading test (NART): test manual, 2nd edn. NFER-Nelson, WindsorGoogle Scholar
- Onaivi ES, Ishiguro H, Zhang PW, Lin Z, Akinshola BE, Leonard CM, Chirwa SS, Gong J, Uhl GR (2006) Endocannabinoid receptor genetics and marijuana use. In: Onaivi ES, Sugiura T, Di Marzo V (eds) Endocannabinoids: the brain and body’s marijuana and beyond. CRC, Boca RatonGoogle Scholar
- Roser P, Stadelmann AM, Arning L, Gallinat J, Epplen JT, Juckel G (2008) Acute effects of delta 9-tetrahydrocannabinol on the auditory event-related mismatch negativity depending on genetic variations in the dysbindin, neuregulin, and G72 gene. Int J Neuropsychopharmacol 11:256Google Scholar
- Solowij N, Yücel M, Lorenzetti V, Lubman DI (2009) Structural brain alterations in cannabis users: association with cognitive deficits and psychiatric symptoms. In: Ritsner MS (ed) The handbook of neuropsychiatric biomarkers, endophenotypes and genes neuroanatomical and neuroimaging endophenotypes and biomarkers. Springer, NetherlandsGoogle Scholar
- Tabachnick BG, Fidell LS (2000) Using multivariate statistics, 4th edn. Allyn and Bacon, BostonGoogle Scholar