Movement Tolerance Did Not Remove THC-Related Memory Effects in Mice
Mice that adapted to THC's movement-suppressing effects still showed spatial-memory and reversal-learning impairment in a repeated-exposure study. Motor tolerance therefore did not establish cognitive tolerance.
The comparison included prior exposure
One group received repeated THC before memory testing, while another did not receive that pretreatment. Both groups received THC during the testing phase. Researchers assessed water-maze performance and zif268-related brain immunoreactivity.
The behavioral and molecular results diverged
The abstract reports persistent memory and reversal-learning effects despite locomotor tolerance in pretreated animals. Selected zif268 changes appeared in non-pretreated animals but not the same way after prior exposure.
A normalized marker need not mean normalized performance
Adaptation in a neuronal-activity marker does not establish recovery in every cognitive task. Likewise, apparently normal movement does not prove that an animal can learn or revise a learned spatial response normally.
The observations occurred during a regimen in which THC continued to be administered. They should not be presented as proof of permanent impairment after abstinence. The study also cannot determine whether a particular human user was impaired while driving. It supports the narrower point that different functions can remain sensitive to THC after another response has become tolerant.
Related: interpreting cannabis tolerance claims.
Research cited
Boucher AA; Vivier L; Metna-Laurent M; Brayda-Bruno L; Mons N; Arnold JC; Micheau J. Chronic treatment with Delta(9)-tetrahydrocannabinol impairs spatial memory and reduces zif268 expression in the mouse forebrain. Behavioural pharmacology (2009). doi:10.1097/FBP.0b013e3283242f6a. Findings discussed from the study abstract.
