A drug-sensitive brain signal may be useful for research without showing that cognition improved. A 2022 human–mouse experiment found amphetamine-related changes in reward EEG signals, while the behavioral and cross-species findings were more limited.
The human experiment
Cavanagh and colleagues analyzed 23 healthy adults, 12 men and 11 women, who completed placebo, 10 mg and 20 mg oral d-amphetamine sessions in a randomized, blinded, counterbalanced crossover. Sessions were separated by one week.
Testing with simultaneous EEG began 120 minutes after dosing. Participants chose between stimuli with different feedback probabilities. The measured reward positivity was an event-related potential associated with feedback, not a direct measurement of pleasure or everyday decision quality.
The animal experiment was distinct
The mouse sample contained 28 animals, 15 male and 13 female. Placebo and 0.1, 0.3 and 1.0 mg/kg d-amphetamine conditions were separated by 72 hours, with testing beginning 15 minutes after administration.
These animal doses and timing cannot be equated with the human oral doses. The main-methods description does not clearly specify an administration route for the mouse dosing; it should not be supplied by assumption. Mouse rewards and punishments also differed from human feedback.
What changed in EEG?
In humans, reward-positivity amplitude increased with dose, alongside changes in reward-related delta-band activity. The corresponding punishment ERP did not show the same significant linear pattern.
In mice, reward and punishment ERP features changed, but the overall dose pattern was quadratic. Examining the lower-dose conditions produced a pattern more similar to the human result. Mouse spectral analyses did not show the corresponding significant effects seen in humans.
Consequently, similarity in one ERP component does not establish that every neural process responded identically across species.
What happened to learning?
The human behavioral analysis included a drug-by-sex interaction, with women tending toward worse performance at higher doses and men unaffected. This was not a uniform cognitive-enhancement result.
Mice showed poor discrimination across the task’s probability conditions, although overall performance exceeded chance when conditions were collapsed. The authors identified poor learning as a limitation for interpreting learning-related spectral effects.
What can the marker establish?
The experiment supports pharmacological sensitivity of selected feedback-related EEG features. It does not establish that a larger signal means better learning, greater pleasure or improved real-world judgment.
The small samples, different reinforcement arrangements and incomplete convergence across signal measures limit translation. An experimental biomarker is not a validated individual test of intoxication, impairment or treatment success.
Scientific source
Cavanagh JF, Olguin SL, Talledo JA, et al. Amphetamine alters an EEG marker of reward processing in humans and mice. Psychopharmacology. 2022;239:923–933. doi:10.1007/s00213-022-06082-z. Original commentary on the supplied paper.
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