Linus Andersson

Looking as if you know: Systematic object inspection precedes object recognition

Sometimes we seem to look at the very object we are searching for, without consciously seeing it. How do we select object relevant information before we become aware of the object? We addressed this question in two recognition experiments involving pictures of fragmented objects. In Experiment 1, participants preferred to look at the target object rather than a control region 25 fixations prior to explicit recognition. Furthermore, participants inspected the target as if they had identified it around 9 fixations prior to explicit recognition. In Experiment 2, we investigated the influence of semantic knowledge in guiding object inspection prior to explicit recognition. Consistently, more specific knowledge about target identity made participants scan the fragmented stimulus more efficiently. For instance, non-target regions were rejected faster when participants knew the target objects name. Both experiments showed that participants were looking at the objects as if they knew them before they became aware of their identity.

Attention bias and sensitization in chemical sensitivity

OBJECTIVE We investigated whether persons with self-reported chemical sensitivity (CS) have an attention bias and enhanced sensitization to chemical exposure. METHODS Chemosomatosensory, olfactory, and auditory event-related potentials (ERPs) were recorded from 21 CS subjects and 17 controls in attend and ignore conditions. Reaction times (RTs) and magnitude estimations of perceived intensity were collected in the attend condition. ERPs were averaged over attention conditions and during the first/second part of the testing. RESULTS ERP patterns indicated that CS subjects did not habituate to the same extent as the controls and had difficulties ignoring the chemical exposure. CS subjects had faster overall RT, and the perceived intensities for the chemosomatosensory stimuli did not decrease with time in the CS group, which was the case for the controls. CONCLUSIONS These results indicating attention bias and enhanced sensitization in CS suggest alterations in central, cognitive responses to chemical exposure.

The idiopathic environmental intolerance symptom inventory : development, evaluation, and application

Objective: To develop, evaluate, and apply a questionnaire-based instrument for investigation of specific symptoms in idiopathic environmental intolerance (IEI), called the Idiopathic Environmental Intolerance Symptom Inventory (IEISI). Methods: Participants with IEI to chemicals responded to 82 candidate symptoms and to three subscales of the Quick Environmental Exposure and Sensitivity Inventory (QEESI) at a test (n = 207) and retest (n = 193) occasion. Results: The 27 most commonly reported symptoms were selected and grouped into five symptom categories. Internal consistency, test–retest reliability, and concurrent validity were found to be satisfying. Cluster analysis identified two subgroups of IEI to chemicals. Conclusions: The results provide support for the IEISI being a reliable, valid, and fast tool for the study of specific symptom prevalence in IEI and encourage further study of subgroups.

Prevalence and risk factors for chemical sensitivity and sensory hyperreactivity in teenagers

The prevalence of chemical sensitivity (CS) and sensory hyperreactivity (SHR) was assessed in a teenage population. Among a random sample of 401 teenagers, 326 (81.3%) answered questionnaires assessing sensitivity to chemicals and noise, anxiety and depression. A subgroup of 85 teenagers conducted a capsaicin inhalation test. The estimated prevalence was 15.6% for general self-reported CS, 3.7% for CS with affective and behavioral consequences, about 1% for SHR. Sensitivity variables were positively intercorrelated. Risk factors for general CS were noise sensitivity (OR: 2.1), probable anxiety (OR: 2.5) and female sex (OR: 2.0). CS problems seem to be present also in teenagers, although less so than in adults. Furthermore, CS seems to be related to other environmental sensitivities.

The influence of health-risk perception and distress on reactions to low-level chemical exposure

The general aim of the current study was to investigate how perceived health risk of a chemical exposure and self-reported distress are related to perceived odor intensity and odor valence, symptoms, cognitive performance over time as well as reactions to blank exposure. Based on ratings of general distress, 20 participants constituted a relatively low distress group, and 20 other participants a relatively high distress group. Health risk perception was manipulated by providing positively and negatively biased information regarding n-butanol. Participants made repeated ratings of intensity, valence and symptoms and performed cognitive tasks while exposed to 4.7 ppm n-butanol for 60 min (first 10 min were blank exposure) inside an exposure chamber. Ratings by the positive and negative bias groups suggest that the manipulation influenced perceived health risk of the exposure. The high distress group did not habituate to the exposure in terms of intensity when receiving negative information, but did so when receiving positive information. The high distress group, compared with the low distress group, rated the exposure as significantly more unpleasant, reported greater symptoms and performed worse on a cognitively demanding task over time. The positive bias group and high distress group rated blank exposure as more intense. The main findings suggest that relatively distressed individuals are negatively affected by exposures to a greater degree than non-distressed.

Chemosensory attention, habituation and detection in women and men

The aim of this study was to investigate whether there are differences between women and men in how chemosensory stimuli are processed. Event-related potentials from 36 participants (18 men) showed that women had larger P3 amplitudes when attending, but not when ignoring CO(2) and amyl acetate stimuli compared with men. Conversely, auditory P3 was reduced by the same degree in women and men. No gender differences were found in magnitude estimations over time. Women had lower detection thresholds for CO(2), but not for n-butanol, compared with men. The main finding was that women and men differ in cognitive measures of chemosensory processing.

Coping strategies, social support and responsibility in chemical intolerance

AIMS AND OBJECTIVES To study coping strategies, social support and responsibility for improvement in chemical intolerance (CI). BACKGROUND Limited knowledge of CI among health professionals and lay persons places demands on the chemically intolerant individuals coping strategies and perception of social support and ability to take responsibility for improvement. However, there is sparse literature on these issues in CI. DESIGN A cross-sectional, questionnaire-based, quasi-experimental study. METHOD Fifty-nine persons with mild, 92 with moderate and 31 with severe CI participated by rating (i) usage and effectiveness of six problem- and six emotion-focused coping strategies, (ii) emotional, instrumental and informative support provided by various sources and (iii) societys and the inflicted individuals responsibility for improvement. RESULTS The participants reported that the most commonly used and effective coping strategies were avoiding odorous/pungent environments and asking persons to limit their use of odorous/pungent substances (problem-focused strategies) as well as accepting the situation and reprioritising (emotion-focused strategies). High intolerance severity was associated with problem-focused coping strategies and relatively low intolerance with emotion-focused strategies. More emotional than instrumental and informative support was perceived, predominantly from the partner and other family members. Responsibility attributed to society was also found to increase from mild to moderate/severe intolerance. CONCLUSIONS Certain coping strategies are more commonly used and perceived as more effective than others in CI. However, intolerance severity plays a role regarding both coping strategies and responsibility. Emotional support appears to be the most available type of support. RELEVANCE TO CLINICAL PRACTICE For improved care, certain coping strategies may be suggested by nurses, the healthcare system needs to provide better social support to these patients and the issue of responsibility for improvement may be discussed with the patient.

Characteristics of hyperacusis in the general population.

There is a need for better understanding of various characteristics in hyperacusis in the general population. The objectives of the present study were to investigate individuals in the general population with hyperacusis regarding demographics, lifestyle, perceived general health and hearing ability, hyperacusis-specific characteristics and behavior, and comorbidity. Using data from a large-scale population-based questionnaire study, we investigated individuals with physician-diagnosed (n = 66) and self-reported (n = 313) hyperacusis in comparison to individuals without hyperacusis (n = 2995). High age, female sex, and high education were associated with hyperacusis, and that trying to avoid sound sources, being able to affect the sound environment, and having sough medical attention were common reactions and behaviors. Posttraumatic stress disorder, chronic fatigue syndrome, generalized anxiety disorder, depression, exhaustion, fibromyalgia, irritable bowel syndrome, migraine, hearing impairment, tinnitus, and back/joint/muscle disorders were comorbid with hyperacusis. The results provide ground for future study of these characteristic features being risk factors for development of hyperacusis and/or consequences of hyperacusis.

Brain responses to olfactory and trigeminal exposure in idiopathic environmental illness (IEI) attributed to smells — An fMRI study

OBJECTIVE Idiopathic environmental intolerance (IEI) to smells is a prevalent medically unexplained illness. Sufferers attribute severe symptoms to low doses of non-toxic chemicals. Despite the label, IEI is not characterized by acute chemical senses. Theoretical models suggest that sensitized responses in the limbic system of the brain constitute an important mechanism behind the symptoms. The aim was to investigate whether and how brain reactions to low-levels of olfactory and trigeminal stimuli differ in individuals with and without IEI. METHODS Brain responses to intranasally delivered isoamyl acetate and carbon dioxide were assessed in 25 women with IEI and 26 non-ill controls using functional magnetic resonance imaging. RESULTS The IEI group had higher blood-oxygenated-level-dependent (BOLD) signal than controls in the thalamus and a number of, mainly, parietal areas, and lower BOLD signal in the superior frontal gyrus. The IEI group did not rate the exposures as more intense than the control group did, and there were no BOLD signal differences between groups in the piriform cortex or olfactory regions of the orbitofrontal cortex. CONCLUSIONS The IEI reactions were not characterized by hyper-responsiveness in sensory areas. The results can be interpreted as a limbic hyperreactivity and speculatively as an inability to inhibit salient external stimuli.

Inflammatory Mediator Profiling of n-butanol Exposed Upper Airways in Individuals with Multiple Chemical Sensitivity

Background Multiple Chemical Sensitivity (MCS) is a chronic condition characterized by reports of recurrent symptoms in response to low level exposure to various chemical substances. Recent findings suggests that dysregulation of the immune system may play a role in MCS pathophysiology. Objectives The aim of this study was to examine baseline and low dose n-butanol-induced upper airway inflammatory response profiles in MCS subjects versus healthy controls. Method Eighteen participants with MCS and 18 age- and sex-matched healthy controls were enrolled in the study. Epithelial lining fluid was collected from the nasal cavity at three time points: baseline, within 15 minutes after being exposed to 3.7 ppm n-butanol in an exposure chamber and four hours after exposure termination. A total of 19 cytokines and chemokines were quantified. Furthermore, at baseline and during the exposure session, participants rated the perceived intensity, valence and levels of symptoms and autonomic recordings were obtained. Results The physiological and psychophysical measurements during the n-butanol exposure session verified a specific response in MCS individuals only. However, MCS subjects and healthy controls displayed similar upper airway inflammatory mediator profiles (P>0.05) at baseline. Likewise, direct comparison of mediator levels in the MCS group and controls after n-butanol exposure revealed no significant group differences. Conclusion We demonstrate no abnormal upper airway inflammatory mediator levels in MCS subjects before or after a symptom-eliciting exposure to low dose n-butanol, implying that upper airways of MCS subjects are functionally intact at the level of cytokine and chemokine production and secretory capacity. This suggests that previous findings of increased cytokine plasma levels in MCS are unlikely to be caused by systemic priming via excessive upper airway inflammatory processes.