Schedule of Events | Symposia

Stimulus expectations drive conditioned olfactory hallucinations

Poster Session F - Tuesday, April 1, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Lauren Wolters¹, Xiaolin Qiao¹, James Howard¹; ¹Brandeis University

Olfactory hallucinations represent a significant portion of experienced hallucinations in both clinical and healthy populations. Empirical studies of auditory and visual hallucinations have used Pavlovian conditioning paradigms to demonstrate that false perception is driven by overly robust representations of stimulus expectations. However, no study has established that a similar mechanism underlies olfactory hallucinations in humans. Here we implemented a conditioned olfactory hallucination paradigm in which we first determined the odor detection thresholds of butanol for each participant (n = 55) using an adaptive psychometric algorithm. Participants then completed an odor detection task where on each trial one of two distinct visual cues was paired with either a supra-threshold, threshold, or sub-threshold concentration of butanol, or no odor. In the first three blocks of task trials, one visual stimulus (“strong cue”) was paired more frequently with supra-threshold concentrations, and the other visual stimulus (“weak cue”) was paired more frequently with sub-threshold concentrations. In the last three blocks both cues were paired most frequently with the no odor condition. We found significantly greater odor detection rates on no odor trials for the strong cue compared to the weak cue (t54 = 2.08, p = 0.043). Importantly, this finding could not be explained by differences in total number of visual cue presentations or other task variables. We thus demonstrate that false odor perception can be enhanced by the expectation of an olfactory stimulus in a Pavlovian conditioning paradigm. Such findings could yield therapeutic insight into the mechanisms underlying pathological olfactory hallucinations.

Topic Area: PERCEPTION & ACTION: Other