Interaction of negative olfactory stimulation and working memory in schizophrenia patients: development and evaluation of a behavioral neuroimaging task

Emotional Experience of People With Schizophrenia and People at Risk for Psychosis: A Meta-Analysis

Importance

Psychotic symptoms are associated with subjective reports of aberrant emotion, such as excessive fear or anhedonia, but whether these aberrations reflect aberrant emotional experience of normative stimuli is uncertain both for individuals with schizophrenia and those at risk for psychosis.

Objective

To provide a meta-analysis of study samples of emotional experience in individuals with schizophrenia and those at risk for psychosis as assessed in laboratory-based emotion-induction studies.

Data Sources

MEDLINE and PsycINFO databases were searched for articles published from January 1986 and Google Scholar citations of a relevant earlier meta-analysis until August 2022. Reference lists were manually searched for additional studies.

Study Selection

Included studies measured positive or negative emotional experience in response to standardized emotionally evocative stimuli and compared participants diagnosed with schizophrenia or participants at risk for psychosis with healthy controls.

Data Extraction and Synthesis

The meta-analysis was registered with PROSPERO and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guidelines. Data were extracted by 2 independent coders, and random-effects analyses were conducted.

Main Outcomes and Measures

Outcomes were 3 scales of emotional experience (unipolar positive emotion, unipolar negative emotion, bipolar valence), analyzed separately for pleasant, neutral, and unpleasant stimuli. A meta-analysis was conducted for differences between the 2 clinical groups combined and controls. Subgroup differences (schizophrenia vs at risk) and the influence of several other variables were tested in moderator analyses.

Results

This systematic review and meta-analysis included data from 111 studies and 6913 participants (schizophrenia: 2848 [41.2%]; at risk: 877 [12.7%]; healthy controls: 3188 [46.1%]). Compared with controls, people with schizophrenia and those at risk for psychosis experienced pleasant stimuli as less positive (unipolar positive: standardized mean difference [SMD] Hedges g = -0.19; P =.001; bipolar valence: SMD Hedges g = -0.28; P <.001) and more negative (Hedges g = 0.52; P <.001), neutral stimuli as more negative (Hedges g = 0.55; P <.001), and unpleasant stimuli as both more positive (unipolar positive: SMD Hedges g = 0.23; P =.005; bipolar valence: Hedges g = 0.12; P =.01) and more negative (Hedges g = 0.22; P <.001). Moderator analyses indicated a less aberrant emotional experience for odors than for visual stimuli (unipolar negative, pleasant z score = -2.97; P =.003; unipolar negative, neutral z score = -2.70; P =.007), an association between higher negative symptoms and diminished positive emotion for pleasant stimuli in schizophrenia (z score = -2.98; P =.003), and that subgroup differences were limited to neutral stimuli.

Conclusions and Relevance

Results suggest a pattern of aberrant emotional experience of normative stimuli in schizophrenia and that this already was observable before disorder onset. In particular, the aberrant experience of pleasant stimuli needs to be considered as an intervention target.

Pain Perception, Brain Connectivity, and Neurochemistry in Healthy, Capsaicin-Sensitive Subjects

Most of the occupational exposure limits (OELs) are based on local irritants. However, exposure to much lower concentrations of irritant substances can also lead to health complaints from workers. Exposure to irritants is often accompanied by strong unpleasant odors, and strong odors might have distracting effects and hence pose a safety risk. The findings obtained in human exposure studies with chemically sensitive, stressed, or anxious persons suggest that their ability to direct attention away from the odorous exposure and to focus on a cognitive task is reduced. In addition, after repeated odor exposure, these persons show signs of sensitization, i.e., difficulties in ignoring or getting used to the exposure. The question arises as to whether certain health conditions are accompanied by a change in sensitivity to odors and irritants, so that these persons are potentially more distracted by odors and irritants and therefore more challenged in working memory tasks than nonsusceptible persons. In our study, susceptible persons with sensory airway hyperreactivity ("capsaicin-sensitive") respond more strongly to mechanical skin stimuli than controls and show altered network connectivity. Capsaicin-sensitive subjects have a lower pain threshold and thus are more sensitive to mechanical skin stimuli. The intrinsic functional connectivity of their saliency network is higher, and the lower the GABAergic tone of the thalamus, the higher their pain sensitivity to mechanical stimuli. It seems that the increased communication between resting-state networks promotes a stronger perception of the sensory input signal. The results can be used to inform about actual risks (i.e., attention diversion and increased risk of accidents) and "pseudo" risks such as odor perception without a negative impact on one's well-being. This way, uncertainties that still prevail in the health assessment of odorous and sensory irritating chemicals could be reduced.

Aberrant interference of auditory negative words on attention in patients with schizophrenia

Previous research suggests that deficits in attention-emotion interaction are implicated in schizophrenia symptoms. Although disruption in auditory processing is crucial in the pathophysiology of schizophrenia, deficits in interaction between emotional processing of auditorily presented language stimuli and auditory attention have not yet been clarified. To address this issue, the current study used a dichotic listening task to examine 22 patients with schizophrenia and 24 age-, sex-, parental socioeconomic background-, handedness-, dexterous ear-, and intelligence quotient-matched healthy controls. The participants completed a word recognition task on the attended side in which a word with emotionally valenced content (negative/positive/neutral) was presented to one ear and a different neutral word was presented to the other ear. Participants selectively attended to either ear. In the control subjects, presentation of negative but not positive word stimuli provoked a significantly prolonged reaction time compared with presentation of neutral word stimuli. This interference effect for negative words existed whether or not subjects directed attention to the negative words. This interference effect was significantly smaller in the patients with schizophrenia than in the healthy controls. Furthermore, the smaller interference effect was significantly correlated with severe positive symptoms and delusional behavior in the patients with schizophrenia. The present findings suggest that aberrant interaction between semantic processing of negative emotional content and auditory attention plays a role in production of positive symptoms in schizophrenia. (224 words).

Emotion-cognition interactions in schizophrenia

OBJECTIVES

Negative emotion exerts a considerable influence on cognitive processes. This may have clinical implications in mental illnesses, such as schizophrenia, where negative emotions often prevail. Experimentally this influence can be studied by using olfactory emotion induction.

METHODS

Fourteen schizophrenia patients and 14 healthy volunteers were investigated with functional magnetic resonance imaging with respect to the neural correlates of emotion-cognition interactions. Emotion was induced by odorants during an n-back working memory task.

RESULTS

Similar detrimental effects of negative stimulation on working memory performance were observed in patients and control subjects. Among the neural correlates modulating this interaction a decreased activation emerged in patients in the anterior cingulate and the medial superior frontal cortex and increased activation in the medial orbitofrontal and middle frontal area.

CONCLUSIONS

During emotion-cognition interaction hypoactivations were found in regions crucial for the monitoring/control of ongoing processes but also for emotion regulation. Decreased activations may reflect failure to adapt to higher task requirements. In contrast, increased activations could be indicative of a greater emotional response and irritation induced by the odour. These patterns may represent the neural correlates of an inefficient control of emotional influences on cognitive processes in patients with schizophrenia.

Multisensory integration of emotionally valenced olfactory-visual information in patients with schizophrenia and healthy controls

BACKGROUND

Patients with schizophrenia frequently have deficits in social cognition, and difficulties in the discrimination of emotional facial expressions have been discussed as an important contributing factor. We investigated whether this impairment is aggravated by difficulties relating the observed facial expression to contextual information, as is often provided by emotionally valenced crossmodal stimulation.

METHODS

We investigated the effects of odorant primes on the accuracy and speed of emotional face recognition. Healthy controls and patients with schizophrenia were exposed to 2-second odorant stimuli: vanillin (pleasant), ambient air (neutral) and hydrogen sulfide (unpleasant). The odours were followed by an emotional face recognition task, in which participants determined if a face showed happiness, disgust or neutral affect.

RESULTS

Controls showed improved performance in the categorization of disgusted faces after all types of odour stimulation irrespective of the emotional valence. However, in controls, the response time for happy faces was slower after presentation of any odour. Schizophrenia patients showed an attenuated effect of olfactory priming on disgust recognition, which resulted in the increased performance differences between the groups. This effect was particularly strong for the unpleasant odour.

LIMITATIONS

The study design did not allow us to fully differentiate between the effects of perceived odour intensity and valence. A possible contribution of cognitive deficits on the observed effects should be investigated in future studies.

CONCLUSION

Our results provide novel evidence for a special connection between the presentation of odorant cues and the accuracy of recognition of disgusted faces in healthy controls. This recognition advantage is disturbed in patients with schizophrenia and appears to contribute to the observed deficit in emotional face recognition.

Cerebral dysfunctions of emotion-cognition interactions in adolescent-onset schizophrenia

OBJECTIVE

Schizophrenia is among the most severe of psychiatric disorders, leading to impairments of affective and cognitive abilities. These dysfunctions affect each other mutually. Adolescent-onset schizophrenia (AOS) constitutes a particularly severe form of the disorder. In this study, possible dysfunctions of the neural correlates underlying the interaction of negative emotion and working memory in AOS were investigated.

METHOD

During functional magnetic resonance imaging, 12 patients with AOS and 12 non-AOS adolescents performed a verbal n-back task. Intermittently, negative and neutral emotions were induced by olfactory stimulation. Group differences in working memory, emotion, and their interaction were evaluated.

RESULTS

In patients with AOS, lower performance sensitivity was observed, along with dorsolateral prefrontal, anterior cingulate, and inferior parietal hypoactivation during working memory demands. For negative versus neutral emotion induction, patients with AOS mainly showed increased brain activation compared with control subjects in widespread brain regions including the left orbitofrontal cortex and the medial frontal gyrus. Finally, during the interaction of emotion and cognition, altered patterns of activation in patients with AOS were found in the thalamocortical network, including the angular and the middle cingulate gyri extending to the precuneus. These activation differences were further decomposed by parameter estimates.

CONCLUSIONS

Our results provide new insights into the neural correlates underlying the mutual influence of affective and cognitive symptoms in AOS. During the n-back task, areas typically associated with working memory performance were found hypoactivated in patients relative to the control subjects, including the dorsolateral prefrontal and parietal cortex and the anterior cingulate. However, patients with AOS mainly demonstrated increased activation in key areas of emotion processing, such as the left orbitofrontal cortex and medial frontal areas, during negative emotion induction. A dysfunctional thalamocortical network during the interaction mainly included regions involved in the integration of converging information--either on the subcortical (thalamus) or on a higher-order cortical level (comprising the angular gyrus). These findings point to dysfunctional emotion-cognition interactions in AOS, which may explain its poor prognosis.

Psychosocial stress induces working memory impairments in an n-back paradigm

In contrast to the substantial number of studies investigating the effects of stress on declarative memory, effects of stress on working memory have received less attention. We compared working memory (numerical n-back task with single digits) in 40 men exposed either to psychosocial stress (Trier Social Stress Test (TSST)) or a control condition. Task difficulty was varied using two conditions (2-back vs. 3-back). Salivary cortisol (as a marker of hypothalamus-pituitary-adrenal (HPA) activity) and salivary alpha-amylase (sAA as a marker of sympathetic nervous system (SNS) activity) were assessed immediately before and three times after the stress or control condition. As expected stress resulted in an increase in cortisol, sAA, and negative affect. Subjects exposed to stress showed significant working memory impairments in both workload conditions. The analysis of variance indicated a main effect of stress for reaction time as well as accuracy. In addition, for reaction time a stress-block interaction occurred. Follow up tests revealed that only during the first block at each level of difficulty performance was significantly impaired by stress. Thus, the effects of stress became smaller the longer the task was performed. Results provide further evidence for impaired working memory after acute stress and illustrate the time course of this phenomenon.

Neural substrates of olfactory processing in schizophrenia patients and their healthy relatives

Odorants represent powerful stimuli capable of eliciting various emotional responses. In schizophrenia patients and their non-affected relatives, olfactory and emotional functions are impaired, revealing a familial influence on these deficits. We aimed at determining the neural basis of emotional olfactory dysfunctions using odors of different emotional valence for mood induction and functional magnetic resonance imaging (fMRI) by comparing 13 schizophrenia patients, their non-affected brothers and 26 matched healthy controls. Blood-oxygen-level-dependent (BOLD) effects and subjective mood changes were assessed during negative (rotten yeast), positive (vanilla) and neutral (ambient air) olfactory stimulation. Group comparisons of brain activation were performed in regions of interest. Subjective ratings were comparable between groups and indicated successful mood induction. However, during stimulation with the negative odor, hypofunctional activity emerged in regions of the right frontal and temporal cortex in the patients. A familial influence in the neural substrates of negative olfactory dysfunction was indicated by a similar reduced frontal brain activity in relatives. Dysfunctions therefore appeared to be located in regions involved in higher cognitive processes associated with olfaction. No familial influences were indicated for cerebral dysfunctions during positive olfactory stimulation. Results point to a differentiation between trait and state components in cerebral dysfunctions during emotional olfactory processing in schizophrenia.

The influence of olfactory-induced negative emotion on verbal working memory: individual differences in neurobehavioral findings

The influence of emotion on cognition plays an important role in people's everyday life as well as in psychiatric and neurological disorders. The present study used fMRI to examine the neural correlates of cognitive-emotional interactions and its inter-individual differences. Twenty-one healthy males performed a 0-back/2-back task while negative or neutral emotion was induced by negative/neutral olfactory stimulation. Subjects revealed a differential effect of emotion on cognition; in 9 subjects, negative odor had a deteriorating influence on verbal working memory ("affected group", AG) while in 12 subjects, performance was not affected in a negative way ("unaffected group", UAG). Although no brain activation differences emerged during the working memory task, the interaction of working memory and emotion yielded significant differences between the AG and the UAG. The latter showed greater activation in the fronto-parieto-cerebellar working memory (WM) network including the precuneus while the AG demonstrated stronger activation in more "emotional" areas (mainly the temporal and medial frontal cortex) as well as compensatory activations in prefrontal regions known to be essential for the cognitive down-regulation of emotions. Hence, the UAG may have been better able to counteract the detrimental influence of negative stimulation during the 2-back task and to effectively sustain or even increase activation in the task-relevant WM network. Correlation analyses for the whole group supported this interpretation; reduced working memory performance during negative stimulation was accompanied by higher activation in the inferior frontal gyrus whereas less performance impairment was related to higher activation in the precuneus. Results confirm the importance of incorporating individual differences in emotion processing and its interaction with cognitive functions in neuroimaging.

Gender differences in the cognitive control of emotion: An fMRI study

The interaction of emotion and cognition has become a topic of major interest. However, the influence of gender on the interplay between the two processes, along with its neural correlates have not been fully analysed so far. In this functional magnetic resonance imaging (fMRI) study we induced negative emotion using negative olfactory stimulation while male (n=21) and female (n=19) participants performed an n-back verbal working memory task. Based on findings indicating increased emotional reactivity in women, we expected the female participants to exhibit stronger activation in characteristically emotion-associated areas during the interaction of emotional and cognitive processing in comparison to the male participants. Both groups were found to be significantly impaired in their working memory performance by negative emotion induction. However, fMRI analysis revealed distinct differences in neuronal activation between groups. In men, cognitive performance under negative emotion induction was associated with extended activation patterns in mainly prefrontal and superior parietal regions. In women, the interaction between emotion and working memory yielded a significantly stronger response in the amygdala and the orbitofrontal cortex (OFC) compared to their male counterparts. Our data suggest that in women the interaction of verbal working memory and negative emotion is associated with relative hyperactivation in more emotion-associated areas whereas in men regions commonly regarded as important for cognition and cognitive control are activated. These results provide new insights in gender-specific cerebral mechanisms.