Hucke, C. I. | Search bioRxiv

bioRxiv2026

Odor Annoyance, Sensory Irritation or Relaxation: Acute Effects of Real Pinewood Emissions in Indoor Air Scenarios

Wood is commonly used in the building sector, emitting volatile organic compounds (VOCs) contributing to indoor air quality. These VOC profiles can have a pleasant smell and positive effects e.g., induce relaxation. Contrarily, VOCs can have adverse health effects in higher concentrations. Therefore, some VOCs are regulated by guide values (GV). Potentially positive and negative effects of pinewood emissions, ranging from 0.2 mg/m3 (German GV I for bicyclic terpenes) to 2.0 mg/m3 (GV II) were investigated in an experimental 2 h exposure study using a within-subject design. Thirty-two healthy participants rated the perception, pleasantness, symptoms of irritation, and indicators of well-being. During a demanding working memory task (n-back) and a resting period, heart rate (HR) and HR variability (HRV) changes were measured. Before and after each session physiological markers of sensory irritation were assessed. Ratings indicated that the exposure to GV I and GV II were not perceived as more intense or pleasant. Mostly concentration-independent effects were revealed, indicating that inter-individual factors influenced the ratings rather than the VOCs. The pinewood odors during the n-back task did not cause distraction nor did it facilitate performance as previously suggested. HR/V changes indicated that pinewood odors during and after the n-back tasks did not induce relaxation. Only symptoms of nasal irritation showed some weak concentration-dependency, not supported by physiological markers or comparable ratings of sensory irritation. In conclusion, the fact that no distinct odor is detected suggests that interfering factors potentially prevent the regulation of odors at relevant indoor air concentrations. HighlightsO_LISuccessful exposure to realistic indoor pinewood VOCs C_LIO_LINo effect on ratings of indoor air quality, performance or sensory irritation C_LIO_LINo induction of relaxation during or after stressful tasks C_LIO_LIShort-term exposure to concentrations between GV I and II are non-effective C_LI

physiology↗

bioRxiv2024

Behavior and alpha-band oscillations reveal cross-modal interactions between chemosensory and auditory processing

The ventriloquism effect, where sounds are mislocalized towards a spatially disparate but temporally synchronous visual stimulus, is well established. Liang et al. (2022) provided first evidence that chemosensory cues can similarly bias sound localization. This study, conducted in 2023, replicates and extends their behavioral findings, using diffusion modeling and EEG to identify underling computational and neural mechanisms. Participants localized (left vs. right) each sound in eight-item sequences, with trigeminally-potent odorants presented concurrently with the first four sounds (left, right, or both nostrils). Unbeknownst to participants, some sounds originated from the center. For central sounds, the proportion of right-ward responses increased with right-nostril stimulation but decreased with left-nostril stimulation (relative to controls). This bias was strongest in the second half of the sequence and disappeared at larger sound eccentricity. Diffusion modeling showed the bias was best explained by changes in drift rate (perceptual evidence accumulation), not in starting point (decision bias). EEG alpha-band activity lateralized towards the chosen side for central sounds, consistent with attentional orienting towards the perceived location, and was diminished at large eccentricities with incongruent chemosensory stimulation. The findings corroborate an odorant-sound spatial ventriloquism effect and provide novel insights into the cognitive and attentional processes involved. Public significance statementOur findings reveal that trigeminally potent odors can subtly influence sound localization judgments, even when those odors are irrelevant to the task at hand. This influence is strongest when sound information is uncertain (i.e., when unbeknownst to participants, a sound that had to be localized as coming from the left or right side, originated from a central location), suggesting that trigeminal stimulation can act as a spatial cue under ambiguous conditions. In addition, concurrent EEG cording revealed that the influence of odorant stimulation was also reflected in neural correlates of auditory spatial attention. Critically, diffusion modeling showed that the observed cross-modal bias occurs at a perceptual level. These findings highlight that the human brain integrates information from the chemical sense and hearing more deeply than previously assumed, revealing that even task-irrelevant odors can shape spatial perception in other senses.

neuroscience↗