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Barnard IL, Onofrychuk TJ, Toderash AD, Patel VN, Glass AE, Adrian JC, Laprairie RB, Howland JG. High-THC Cannabis Smoke Impairs Incidental Memory Capacity in Spontaneous Tests of Novelty Preference for Objects and Odors in Male Rats. eNeuro 2023; 10:ENEURO.0115-23.2023. [PMID: 37973381 PMCID: PMC10714893 DOI: 10.1523/eneuro.0115-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Revised: 09/19/2023] [Accepted: 10/16/2023] [Indexed: 11/19/2023] Open
Abstract
Working memory is an executive function that orchestrates the use of limited amounts of information, referred to as working memory capacity, in cognitive functions. Cannabis exposure impairs working memory in humans; however, it is unclear whether Cannabis facilitates or impairs rodent working memory and working memory capacity. The conflicting literature in rodent models may be at least partly because of the use of drug exposure paradigms that do not closely mirror patterns of human Cannabis use. Here, we used an incidental memory capacity paradigm where a novelty preference is assessed after a short delay in spontaneous recognition-based tests. Either object or odor-based stimuli were used in test variations with sets of identical [identical stimuli test (IST)] and different [different stimuli test (DST)] stimuli (three or six) for low-memory and high-memory loads, respectively. Additionally, we developed a human-machine hybrid behavioral quantification approach which supplements stopwatch-based scoring with supervised machine learning-based classification. After validating the spontaneous IST and DST in male rats, 6-item test versions with the hybrid quantification method were used to evaluate the impact of acute exposure to high-Δ9-tetrahydrocannabinol (THC) or high-CBD Cannabis smoke on novelty preference. Under control conditions, male rats showed novelty preference in all test variations. We found that high-THC, but not high-CBD, Cannabis smoke exposure impaired novelty preference for objects under a high-memory load. Odor-based recognition deficits were seen under both low-memory and high-memory loads only following high-THC smoke exposure. Ultimately, these data show that Cannabis smoke exposure impacts incidental memory capacity of male rats in a memory load-dependent, and stimuli-specific manner.
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Affiliation(s)
- Ilne L Barnard
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N5E5, Canada
| | - Timothy J Onofrychuk
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N5E5, Canada
| | - Aaron D Toderash
- Department of Computer Science, University of Saskatchewan, Saskatoon, Saskatchewan, S7N5C9, Canada
| | - Vyom N Patel
- Department of Computer Science, University of Saskatchewan, Saskatoon, Saskatchewan, S7N5C9, Canada
| | - Aiden E Glass
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N5E5, Canada
| | - Jesse C Adrian
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N5E5, Canada
| | - Robert B Laprairie
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan, S7N5E5, Canada
- Department of Pharmacology, College of Medicine, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - John G Howland
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N5E5, Canada
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