Neural Mechanisms of Cannabinoid-impaired Decision-Making in Emerging Adults

In a Probabilistic Reinforcement Learning Choice (PRLC) task, two stimuli are presented and choosing either could result in a monetary reinforcer, but the reinforcement probabilities of the stimuli differ, and change throughout the task. Individuals attempt to optimize choices according to learned probabilities and track changing probabilities over time. PRLC performance allows mathematical modeling of trial-by-trial data under real-world uncertainty and yields computational parameters, such as the learning rate. Choice data were analyzed using a Rescorla-Wanger learning model with an alpha learning rate, beta inverse temperature, and perseveration global parameters. Model-derived learning rates are indicative of an individual's ability to learn from previous choice outcomes to update future decision-making. For this task, learning rates range from 0-1 with lower values indicative of more optimal learning.

Time frame: Measure collected at 2 time points: Baseline (0HR) and Post TMS Administration (3HR)

Population: Of the 58 total participants assigned to the excitatory TMS condition, 15 individuals completed at least one experimental session.~Of the 8 total participants assigned to the inhibitory TMS condition, 6 individuals completed at least one experimental session.

Elasticity of Demand was measured by the Cannabis Purchase Task (CPT) where participants are asked how many hits of cannabis they would consume at 16 different price points in ascending order ($0-$140). Higher elasticity values indicate a greater sensitivity to changing price points resulting in a reduced demand for hits of THC at increasing price points.

Time frame: Measured 2 times: Baseline (0HR) and Post-TMS (3HR) after THC administration on each drug condition (0mg, 10mg, 30mg).

Population: Of the 58 participants assigned to the excitatory TMS condition, 13 individuals had usable data from at least one experimental session.~Of the 8 participants assigned to the excitatory TMS condition, 4 individuals had usable data from at least one experimental session.

A Visual Analogue Scale (VAS) was used to measure the acute subjective effects of THC at varying doses (0mg, 10mg, 30mg). Responses are made for VAS items along a 100-unit scale anchored on the extremes by Not At All (0) and Extremely (100) with a higher score meaning more of the effect. Participants were instructed to select Not At All (0) for all baseline (0HR) measures. Post-TMS administration (real or sham), participant self-reported their subjective high on the VAS with higher values indicating a more intense sensation of high.

Time frame: Measured 2 times: Baseline (0HR) and 3 hours (3HR) after capsule administration on each drug condition (0mg, 10mg, 30mg)

Population: Of the 58 participants assigned to the Excitatory TMS condition, as max of 14 participants had usable data from at least one experimental session.~Of the 8 participants assigned to the Inhibitory TMS condition, as max of 4 participants had usable data from at least one experimental session.

Working memory (WM), the ability to hold a finite amount of information for a set amount of time, is measured by the N-Back task. Here, participants were presented with a sequence of letters and must indicate when the letter currently being viewed matches the one from N steps earlier in the sequence. The load factor N is adjusted between 0, 1, and 2 to adjust the difficulty of the task (0-Back = no WM load, 1-Back = minimal WM load, 2-Back = greater WM load) where a higher score means better memory performance. Outcomes are reported as the Total Accuracy Percentage (Correct Choices/Total Choices) x 100%

Time frame: Measured 2 times: Baseline (0HR) and Post-TMS (3HR) after THC administration on each drug condition (0mg, 10mg, 30mg).

Population: Of the 58 participants assigned to the excitatory TMS condition, 14 individuals had usable data from at least one experimental session.~Of the 8 participants assigned to the excitatory TMS condition, 4 individuals had usable data from at least one experimental session.