Olfactory deficits in schizophrenia

Investigating the Link between Eating Attitudes, Taste and Odour Preferences and the Chemical Senses

OBJECTIVES

To examine if higher degrees of pathological eating attitudes in a non-clinical sample are associated with odour and taste perception and preferences based on psychophysical ratings.

PARTICIPANTS AND METHODS

A total of 80 female university students completed the eating attitudes test (EAT-26), followed by four chemosensory measures including olfactory and gustatory perception plus perceptual ratings and preferences for food odours and tastes.

RESULTS

There were no significant correlations between EAT-26 scores and measures of olfactory and gustatory perception. However, a significant interaction effect indicated higher degrees of pathological eating attitudes may be associated with differential sensitivity to sweet and fatty food odours compared to those with lower levels of pathological eating attitudes.

CONCLUSIONS

This was the first study to examine pathological eating attitudes using food stimuli with a non-clinical sample. The results remain preliminary until replication. However, the findings highlight the need for development of measures of disordered eating attitudes and behaviours that go beyond caloric restriction.

Peripheric and central olfactory measurements in patients with bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a mental health disorder.

PURPOSE

To investigate the peripheric and central olfactory measurements in patients with BD using magnetic resonance imaging (MRI).

MATERIAL AND METHODS

This study was conducted retrospectively. Group 1 consisted of 27 euthymic patients with BD (14 men, 13 women) and Group 2 consisted of 27 healthy controls (14 men, 13 women). Olfactory bulb (OB) volume and olfactory sulcus (OS) depth (peripheric), and corpus amygdala and insular gyrus area (central) measurements were performed using cranial MRI.

RESULTS

OB volume and OS depth value of the bipolar group were lower than the control group, but there were no significant differences between the groups (P > 0.05). The corpus amygdala and left insular gyrus area of the bipolar group were significantly lower than those in the control group (P < 0.05). There were positive correlations between OB volumes and OS depths, the insular gyrus areas, and the corpus amygdala areas (P < 0.05). As the number of depressive episodes and duration of illness increased in bipolar patients, the depth of the sulcus decreased (P < 0.05).

CONCLUSION

In the present study a correlation was detected between OB volumes and the structures, known as emotional processing (e.g. insular gyrus area, corpus amygdala), and clinical features. Accordingly, new treatment techniques, such as olfactory training, may be considered an option in the treatment of such patients with BD.

Olfactory impairment in psychiatric disorders: Does nasal inflammation impact disease psychophysiology?

Olfactory impairments contribute to the psychopathology of mental illnesses such as schizophrenia and depression. Recent neuroscience research has shed light on the previously underappreciated olfactory neural circuits involved in regulation of higher brain functions. Although environmental factors such as air pollutants and respiratory viral infections are known to contribute to the risk for psychiatric disorders, the role of nasal inflammation in neurobehavioral outcomes and disease pathophysiology remains poorly understood. Here, we will first provide an overview of published findings on the impact of nasal inflammation in the olfactory system. We will then summarize clinical studies on olfactory impairments in schizophrenia and depression, followed by preclinical evidence on the neurobehavioral outcomes produced by olfactory dysfunction. Lastly, we will discuss the potential impact of nasal inflammation on brain development and function, as well as how we can address the role of nasal inflammation in the pathophysiological mechanisms underlying psychiatric disorders. Considering the current outbreak of Coronavirus Disease 2019 (COVID-19), which often causes nasal inflammation and serious adverse effects for olfactory function that might result in long-lasting neuropsychiatric sequelae, this line of research is particularly critical to understanding of the potential significance of nasal inflammation in the pathophysiology of psychiatric disorders.

Can olfactory dysfunction be a marker of trait or states of bipolar disorders? A comprehensive review

BACKGROUND

Olfactory deficits (OD) are reported as markers for a large spectrum of neuro-psychiatric disorders. Alterations can concern perception, identification, discrimination and assignment of odour's valence of olfaction process. We propose a comprehensive review to summarize which kind of OD were reported in bipolar disorders (BD) and in which phase of the disease, to know if they could be a marker of state or trait.

METHODS

A Systematic Literature Review was conducted using PRISMA guidelines to include all studies assessing olfaction with objective measures in BD.

RESULTS

9 studies were identified. All of them have assessed odour identification and 3 reported deficits mainly in patients with psychotic features or elements of illness severity in comparison to healthy subjects. There is no difference in threshold of perception between BD patients and controls and it is no possible to conclude for discrimination because only one study has assessed this dimension in comparison to control. We cannot conclude for hedonic value of odours regarding these studies.

LIMITATIONS

These studies are very incomplete because only one has evaluated all the processes involved in olfaction process.

CONCLUSIONS

In light of this review, evidence is still missing to unveil potential disturbances of olfactory process as a marker of BD. These new avenues of research could help to clarify the links between OD and BD and provide information on the pathophysiology of the disorder according to the impaired dimension.

Neuroimaging of smell and taste

The senses of taste and smell developed early in evolution and are of high ecological and clinical relevance in humans. Chemosensory systems function, in large part, as hazard avoidance systems, thereby ensuring survival. Moreover, they play a critical role in nutrition and in determining the flavor of foods and beverages. Their dysfunction has been shown to be a key element of early stages of a number of diseases, including Alzheimer's and Parkinson's diseases. Advanced neuroimaging methods provide a unique means for understanding, in vivo, neural and psychological processing of smell, taste, and flavor, and how diseases can impact such processing. This chapter provides, from a neuroimaging perspective, a comprehensive overview of the anatomy and physiology involved in the odor and taste processing in the central nervous system. Some methodological challenges associated with chemosensory neuroimaging research are discussed. Multisensory integration, the mechanisms that enable holistic sensory experiences, is emphasized.

Olfactory processing in bipolar disorder, major depression, and anxiety

OBJECTIVES

Although olfactory abnormalities are well established in schizophrenia, considerably less work has examined olfactory performance in other neuropsychiatric conditions. In the current study, we examined odor identification, odor discrimination, detection threshold, and odor hedonic processing performance in individuals with bipolar I disorder (n = 43; n = 13 with psychotic features), bipolar II disorder (n = 48), major depressive disorder (MDD) (n = 134), anxiety (n = 48), and no mental disorder (n = 72) who participated in a community-based family study.

METHODS

Best estimate DSM-IV diagnoses were based on in-depth personal interviews as well as interviews with family members. Olfactory tests were administered during an in-person clinical visit and were compared using robust linear regression adjusting for age, sex, and psychiatric medication use, as well as nicotine use when necessary.

RESULTS

Compared to controls, odor identification performance was lower among individuals with MDD (b = -1.37, 95% confidence interval [CI]: -2.50, -0.24) and bipolar I disorder (b = -1.79, 95% CI: -3.51, -0.67). Among the latter group, performance was only reduced among those with psychotic features (b = -3.49, 95% CI: -6.33, -0.65), particularly for pleasant odors (b = -1.46, 95% CI: -2.51, -0.42). Those with MDD showed lower identification accuracy for neutral odors (b = -0.63, 95% CI: -1.20, -0.06). Performances on measures of odor discrimination and detection threshold did not differ by diagnostic group.

CONCLUSIONS

Collectively, these findings indicate that odor identification difficulties may exist in mood disorders, especially when psychotic features are present. In contrast, the global olfactory dysfunction observed in schizophrenia may not be a feature of other neuropsychiatric conditions.

Olfactory impairment in first-episode schizophrenia: a case-control study, and sex dimorphism in the relationship between olfactory impairment and psychotic symptoms

BACKGROUND

A body of studies has focused on the olfactory impairment among people with schizophrenia. The effect of sex on this relationship has attracted the attention of researchers. These issues have not been studied much in Chinese schizophrenia patients.

METHODS

We conducted a case-control study of 110 first-episode antipsychotic medicine naïve schizophrenia patients aged 18-35 years and 110 controls, matched by age and sex. Odour threshold, discrimination and identification were assessed by the "Sniffin' Sticks" test. Psychotic symptoms were assessed by the Positive and Negative Syndrome Scale (PANSS).

RESULTS

The odour threshold, discrimination and identification scores of patients with schizophrenia were significantly lower than those of the healthy control group. The difference in identification score had statistical significance between male and female patients with schizophrenia (t = - 2.45, P < 0.05). Controlling for confounding factor, in male schizophrenia participants, the negative subscale score was significantly and inversely correlated with the discrimination (γ = - 0.37, p < 0.008), identification (γ = - 0.45, p < 0.008) and TDI (γ = - 0.50, p < 0.008) scores; the general psychopathology subscale score was inversely and significantly correlated with the identification (γ = - 0.47, p < 0.008) and TDI (γ = - 0.41, p < 0.008) scores. For female schizophrenia patients, positive and general psychopathology subscale scores had a significant inverse correlation with the identification score (positive: γ = - 0.47, p < 0.008; general psychopathology: γ = - 0.42, p < 0.008).

CONCLUSIONS

Controlling for confounder, negative symptoms were related to impaired odour discrimination and identification in male schizophrenia patients, while positive symptoms were correlated with impaired odour identification in female schizophrenia patients. This sex dimorphism could provide useful information for future studies aiming to finding biomarkers of schizophrenia.

Male rats treated with subchronic PCP show intact olfaction and enhanced interest for a social odour in the olfactory habituation/dishabituation test

The olfactory system participates in many sensory processes, and olfactory endophenotypes appear in a variety of neurological disorders such as Alzheimer's and Parkinson's disease, depression and schizophrenia. Social withdrawal is a core negative symptom of schizophrenia and animal models have proven to be invaluable for studying the neurobiological mechanisms and cognitive processes behind the formation of social relationships. The subchronic phencyclidine (PCP) rat model is a validated model for negative symptoms of schizophrenia, such as impaired sociability. However, the complete range of social behaviour and deficits in the model are still not fully understood. Intact rodent olfaction is essential for a wide range of social behaviour and disrupted olfactory function could have severe effects on social communication and recognition. In order to examine the olfactory ability of male rats treated with subchronic PCP, we conducted an olfactory habituation/dishabituation test including both non-social and social odours. The subchronic PCP-treated rats successfully recognized and discriminated among the odours, indicative of intact olfaction. Interestingly, the subchronic PCP-treated rats showed greater interest for a novel social odour compared to the saline-treated rats and the rationale remains to be elucidated. Our data indicate that subchronic PCP treatment does not disrupt olfactory function in male rats. By ruling out impaired olfaction as cause for the poor social interaction performance in subchronic PCP-treated rats, our data supports the use of NMDA receptor antagonists to model the negative symptoms of schizophrenia.

Olfactory Functioning in First-Episode Psychosis

BACKGROUND

Though olfactory deficits are well-documented in schizophrenia, fewer studies have examined olfactory performance profiles across the psychosis spectrum. The current study examined odor identification, discrimination, and detection threshold performance in first-episode psychosis (FEP) patients diagnosed with schizophrenia, schizoaffective disorder, bipolar disorder with psychotic features, major depression with psychotic features, and other psychotic conditions.

METHOD

FEP patients (n = 97) and healthy adults (n = 98) completed birhinal assessments of odor identification, discrimination, and detection threshold sensitivity for lyral and citralva. Participants also completed measures of anticipatory pleasure, anhedonia, and empathy. Differences in olfactory performances were assessed between FEP patients and controls and within FEP subgroups. Sex-stratified post hoc analyses were employed for a complete analysis of sex differences. Relationships between self-report measures and olfactory scores were also examined.

RESULTS

Individuals with psychosis had poorer scores across all olfactory measures when compared to the control group. Within the psychosis cohort, patients with schizophrenia-associated psychosis had poorer odor identification, discrimination, and citralva detection threshold scores relative to controls. In schizophrenia patients, greater olfactory disturbance was associated with increased negative symptomatology, greater self-reported anhedonia, and lower self-reported anticipatory pleasure. Patients with mood-associated psychosis performed comparable to controls though men and women in this cohort showed differential olfactory profiles.

CONCLUSIONS

These findings indicate that olfactory deficits extend beyond measures of odor identification in FEP with greater deficits observed in schizophrenia-related subgroups of psychosis. Studies examining whether greater olfactory dysfunction confers greater risk for developing schizophrenia relative to other forms of psychosis are warranted.

Disrupted Olfactory Integration in Schizophrenia: Functional Connectivity Study

BACKGROUND

Evidence for olfactory dysfunction in schizophrenia has been firmly established. However, in the typical understanding of schizophrenia, olfaction is not recognized to contribute to or interact with the illness. Despite the solid presence of olfactory dysfunction in schizophrenia, its relation to the rest of the illness remains largely unclear. Here, we aimed to examine functional connectivity of the olfactory bulb, olfactory tract, and piriform cortices and isolate the network that would account for the altered olfaction in schizophrenia.

METHODS

We examined the functional connectivity of these specific olfactory regions in order to isolate other brain regions associated with olfactory processing in schizophrenia. Using the resting state functional MRI data from the Center for Biomedical Research Excellence in Brain Function and Mental Illness, we compared 84 patients of schizophrenia and 90 individuals without schizophrenia.

RESULTS

The schizophrenia group showed disconnectivity between the anterior piriform cortex and the nucleus accumbens, between the posterior piriform cortex and the middle frontal gyrus, and between the olfactory tract and the visual cortices.

CONCLUSIONS

The current results suggest functional disconnectivity of olfactory regions in schizophrenia, which may account for olfactory dysfunction and disrupted integration with other sensory modalities in schizophrenia.

Deficits in the identification of pleasant odors predict the transition of an at-risk mental state to psychosis

OBJECTIVE

Existing knowledge of the relationship between olfactory identification (OI) ability and clinical risk of psychosis is inconsistent. To address this inconsistency, the aim of the present study was to identify the relationship between OI ability, with regard to the hedonic attributes of odors, and the risk of transition to psychosis in individuals with an ARMS.

METHODS

A group of 81 individuals meeting the ARMS criteria according to the Comprehensive Assessment of At Risk Mental State were at baseline administered with the University of Pennsylvania Smell Identification Test. The hedonic attributes of odorants were normatively established. Participants were followed up for transition to psychosis for a mean period of 36.1months (SD:27.5months).

RESULTS

The presence of deficits in the identification of pleasant odors was found to be a risk factor for conversion from an ARMS to schizophrenia. The hazard ratio for each point in deficit scores in the Cox regression model was 1.455 (95% CI: 1.211-1.747), p<0.0001. Significant deficits in the identification of pleasant odors were associated with a risk for conversion at both early and late time points from baseline.

CONCLUSIONS

The findings imply that the impaired identification of pleasant odorants may be a risk factor for the transition of an ARMS into a psychotic disorder, and highlights the need for further research of OI in "at-risk" cohorts, taking into account the hedonic attributes of odors.

Relationship between olfactory function and social cognition in euthymic bipolar patients

OBJECTIVE/INTRODUCTION

There is a close functional and neuroanatomical relationship between olfactory ability and emotional processing. The present study seeks to explore the association between olfactory ability and social cognition, especially facial emotion perception, in euthymic bipolar patients.

METHODS

Thirty-nine euthymic outpatients meeting DSM-IV-TR criteria for bipolar disorder and 40 healthy volunteers matched on socio-demographic criteria were recruited. Both groups were assessed at one time point with the University of Pennsylvania Smell Identification Test (UPSIT), the Emotion Recognition Test, and The Faux Pas Recognition Test, as well as measures of general cognition and functioning.

RESULTS

The bipolar patients showed a significant impairment in olfactory identification (UPSIT) and social cognition measures compared to healthy controls. Analyses revealed significant relationships between olfactory identification and facial emotion recognition, theory of mind, general cognition, and a trend-level relationship with functioning. Controlling for age and cigarettes smoked, relationships remained significant between olfactory function and facial emotion recognition.

CONCLUSION

There is a deficit of olfactory identification in euthymic patients with bipolar disorder that is correlated with a deficit in both verbal and non-verbal measures of social cognition.

Brain structural imaging correlates of olfactory dysfunction in obsessive-compulsive disorder

Olfactory dysfunction has been described in obsessive-compulsive disorder (OCD). Brain regions involved in smell processing partially overlap with structures included in the neurobiological models of OCD, although no previous studies have analyzed the neuroanatomical correlates of olfactory dysfunction in this disorder. The aim of our study was to examine the association between regional gray matter volume, as assessed by a voxel-based morphometry analysis of magnetic resonance images (MRI), and olfactory function, as assessed by the Sniffin' Sticks test (SST). Olfactory function was assessed in 19 OCD patients and 19 healthy volunteers. All participants were also scanned in a 1.5-T magnet to obtain T1-weighted anatomical MRIs, which were pre-processed and analyzed with SPM8. Three different correlation models were used to study the association between regional gray matter volumes and olfactory function in the domains assessed by the SST: detection threshold, discrimination, and identification. OCD patients showed a significant impairment in all the domains assessed by the SST. Voxel-based mapping revealed a positive association in healthy controls between detection threshold and the gray matter content of a left anterior cingulate cortex cluster. In OCD patients, a positive correlation was observed between identification errors and the gray matter volume of the left medial orbital gyrus. In a post hoc analysis, these two gray matter regions were shown to be enlarged in OCD patients. Our findings support the idea that olfactory dysfunction in OCD is associated with volumetric changes in brain areas typically implicated in the neurobiology of the disorder.

Olfaction in the psychosis prodrome: electrophysiological and behavioral measures of odor detection

Smell identification deficits (SIDs) are relatively specific to schizophrenia and its negative symptoms, and may predict transition to psychosis in clinical high-risk (CHR) individuals. Moreover, event-related potentials (ERPs) to odors are reduced in schizophrenia. This study examined whether CHR patients show SIDs and abnormal olfactory N1 and P2 potentials. ERPs (49 channels) were recorded from 21 CHR and 20 healthy participants (13 males/group; ages 13-27 years) during an odor detection task using three concentrations of hydrogen sulfide (H2S) or blank air presented unilaterally by a constant-flow olfactometer. Neuronal generator patterns underlying olfactory ERPs were identified and measured by principal components analysis (unrestricted Varimax) of reference-free current source densities (CSD). Replicating previous findings, CSD waveforms to H2S stimuli were characterized by an early N1 sink (345 ms, lateral-temporal) and a late P2 source (600 ms, mid-frontocentroparietal). N1 and P2 varied monotonically with odor intensity (strong > medium > weak) and did not differ across groups. Patients and controls also showed comparable odor detection and had normal odor identification and thresholds (Sniffin' Sticks). However, olfactory ERPs strongly reflected differences in odor intensity and detection in controls, but these associations were substantially weaker in patients. Moreover, severity of negative symptoms in patients was associated with reduced olfactory ERPs and poorer odor detection, identification and thresholds. Three patients who developed psychosis had poorer odor detection and thresholds, and marked reductions of N1 and P2. Thus, despite the lack of overall group differences, olfactory measures may be of utility in predicting transition to psychosis among CHR patients.

Olfaction in affective and anxiety disorders: a review of the literature

BACKGROUND

Olfaction and its relation to mental health is an area of growing interest. Brain areas linked to olfaction partially overlap with brain areas involved in psychiatric disorders; consequently, the study of olfactory function allows us to explore the integrity of these brain areas with a non-invasive and effective method. Accordingly, the aim of this paper is to review olfactory function in affective and anxiety disorders.

METHODS

For this purpose, an extensive literature review of English-language studies on olfactory function in patients with the aforementioned pathologies was performed using several online databases. A manual search of relevant journals and books as well as reference lists from selected papers was also performed.

RESULTS

The available data show that depressed patients are usually characterised by preserved olfactory function, except for detection threshold, where contrasting reports have been found. Bipolar disorder has been studied to a lesser extent, but the findings have shown a lack of impairment in most cases. Research on seasonal affective disorders is scant, and future studies are needed to make conclusions. Anxiety disorders have been scarcely approached, but the results note identification deficits in obsessive-compulsive and posttraumatic stress disorders.

CONCLUSIONS

Olfactory assessment appears to be a complementary, valuable research tool in the study of psychiatric disorders. However, further investigation is needed to improve our understanding of olfactory function in these disorders.

Olfaction, "olfiction," and the schizophrenia-spectrum: an updated meta-analysis on identification and acuity

Olfaction deficits in individuals with schizophrenia are well documented. A meta-analysis conducted nearly a dozen years ago on the topic revealed a deficit of a full standard deviation in magnitude compared to nonpatient controls. Recent efforts have been attempted to determine whether deficits in olfactory identification and acuity reflect a vulnerability marker of schizophrenia-spectrum pathology. To address this issue, the present study conducted a meta-analysis of 16 studies of individuals with schizotypy, defined in terms of a) "ultra-high risk" status, b) having an affected biological family member, or c) having extreme scores on a schizotypy questionnaire. We also conducted an updated meta-analysis of 40 studies of olfactory functioning in schizophrenia. Consistent with the prior meta-analysis, patients with schizophrenia showed impairments in olfaction identification on a full standard deviation in magnitude (d = -.99). Individuals with schizotypy showed much more subtle (d = -.24) differences in olfaction, though the effect sizes were higher for studies examining individuals at "ultra-high risk" (d = -.67) versus studies examining individuals with psychometrically-defined (d = -.14) schizotypy. Differences in olfactory acuity, relative to their respective control groups, were small for both the schizophrenia (d = -.45) and schizotypy (d = -.38) studies but were similar in magnitude. The present findings argue against the notion that deficits in olfaction identification are a vulnerability marker of schizophrenia. Suggestions for future research are recommended.

Olfactory sulcal depth and olfactory bulb volume in patients with schizophrenia: an MRI study

The current report used structural magnetic resonance imaging (MRI) to objectively measure olfactory bulb volume and olfactory sulcal depth in patients diagnosed with chronic schizophrenia and healthy controls. Additional measures were obtained to assess olfactory function. The olfactory bulb and sulcus were manually traced on structural 3T MRIs for 25 right-handed male patients diagnosed with chronic schizophrenia and 25 matched male healthy controls. A sub-set of subjects received the University of Pennsylvania Smell Identification Test (UPSIT). Olfactory bulb volume was significantly decreased in patients with schizophrenia compared to healthy controls, as was their performance on the UPSIT. Additionally, a positive correlation was seen in patients between right bulb volume and UPSIT scores. Overall, our findings support earlier research studies showing morphometric and functional changes in the olfactory system in patients with schizophrenia.

Olfactory acuity is associated with mood and function in a pilot study of stable bipolar disorder patients

OBJECTIVES

Olfactory dysfunction is described in several neuropsychiatric disorders but there is little research on olfactory processing in bipolar disorder.

METHODS

We assessed odor detection threshold (sensitivity) and smell identification test scores, along with symptoms, cognition, and social function in 20 DSM-IV bipolar disorder patients and 44 control subjects.

RESULTS

The patient and control groups had similar demographic measures, intelligence, and mean olfaction scores, but significantly differed in social domains, including adjustment, function, and anxiety. Odor detection sensitivity showed significantly opposite correlations for the depressive and manic mood domains in bipolar disorder (r to z = 2.83, p = 0.005). Depressive symptoms were related to increased sensitivity (the ability to detect odors at a lower concentration) and mania symptoms were related to decreased sensitivity for odor detection. Increased sensitivity for odor detection also predicted significantly better employment (r = -0.642, p = 0.024), whereas less sensitivity was associated with social avoidance (r = 0.702, p =0.024) and social fear (r = 0.610, p = 0.046).

CONCLUSIONS

Diminished odor detection sensitivity predicted mania and social avoidance, whereas more sensitive odor detection predicted more depressive symptoms but better employment functioning in bipolar disorder patients. Odor acuity may be an illness state marker of mood syndromes in bipolar disorder. Alternatively, differences in odor acuity may identify heterogeneous subgroups within the bipolar spectrum. Longitudinal assessments in a large, sex-stratified sample are needed to understand the implications of odor sensitivity in patients with bipolar disorder.

Olfactory identification and preference in bipolar disorder and schizophrenia

Olfactory identification deficit appears to be an enduring feature of schizophrenia, but it is unclear whether it is specific to schizophrenia or present in psychotic disorders in general. The aim of the present study was to compare olfactory identification and olfactory preference in schizophrenia and bipolar disorder. Individuals with schizophrenia or bipolar disorder and demographically matched healthy participants were given the University of Pennsylvania Smell Identification Test (UPSIT) to assess olfactory identification ability. To examine olfactory hedonic judgment, participants were also asked to indicate their preference for each UPSIT item on a 5-point rating scale, immediately after odor identification. Clinical symptoms and social competence were also assessed. Both schizophrenic and bipolar groups showed olfactory identification deficits compared with the healthy controls, but schizophrenic patients were more impaired than bipolar patients on the UPSIT accuracy. Interestingly, both bipolar and schizophrenic patients rated odors to be more pleasant than did healthy controls, but all groups preferred odors that they could correctly identify to unidentified smells. Restricted range of preference ratings was associated with the severity of negative symptoms in schizophrenia, and with mania in bipolar disorder. Social competence was associated with better olfactory identification performance. These findings suggest that olfactory identification and preference are compromised in bipolar disorder as well as in schizophrenia, but the precise nature of these abnormalities needs to be further elucidated.

Olfactory dysfunction in schizophrenia: a review of neuroanatomy and psychophysiological measurements

Olfactory processing is thought to be mediated via the frontal and temporolimbic brain regions, both of which, as well as olfactory dysfunction, are implicated in schizophrenia. Likewise, several empirical studies of olfactory dysfunction--in particular, olfactory deficits in identification, odor detection threshold sensitivity, and odor memory, along with associated brain structural changes--have been conducted to illuminate the pathophysiology of schizophrenia. These anomalies have been investigated, more recently, as possible biological markers of that disabling illness. This article summarizes recent research on neuroimaging changes associated with olfactory impairments in schizophrenia patients and on related functional changes in psychophysiological measurements (e.g., odor identification, odor discrimination, odor detection threshold, and odor memory). The possible role of these changes as biological markers of the disorder will be discussed, as will potentially productive directions for future research.

Scents and nonsense: olfactory dysfunction in schizophrenia

Among the sensory modalities, olfaction is most closely associated with the frontal and temporal brain regions that are implicated in schizophrenia and most intimately related to the affective and mnemonic functions that these regions subserve. Olfactory probes may therefore be ideal tools through which to assess the structural and functional integrity of the neural substrates that underlie disease-related cognitive and emotional disturbances. Perhaps more importantly, to the extent that early sensory afferents are also disrupted in schizophrenia, the olfactory system-owing to its strategic anatomic location-may be especially vulnerable to such disruption. Olfactory dysfunction may therefore be a sensitive indicator of schizophrenia pathology and may even serve as an "early warning" sign of disease vulnerability or onset. In this article, we review the evidence supporting a primary olfactory sensory disturbance in schizophrenia. Convergent data indicate that structural and functional abnormalities extend from the cortex to the most peripheral elements of the olfactory system. These reflect, in part, a genetically mediated neurodevelopmental etiology. Gross structural and functional anomalies are mirrored by cellular and molecular abnormalities that suggest decreased or faulty innervation and/or dysregulation of intracellular signaling. A unifying mechanistic hypothesis may be the epigenetic regulation of gene expression. With the opportunity to obtain olfactory neural tissue from live patients through nasal epithelial biopsy, the peripheral olfactory system offers a uniquely accessible window through which the pathophysiological antecedents and sequelae of schizophrenia may be observed. This could help to clarify underlying brain mechanisms and facilitate identification of clinically relevant biomarkers.

The functional role of the medio dorsal thalamic nucleus in olfaction

Olfaction is unique relative to other sensory modalities in terms of how its neuroanatomy is organized within the brain and its perceptual properties. Olfactory information processing occurs via connections made directly from primary processing areas (piriform cortex) to neocortical structures (orbitofrontal cortex) as well as indirectly via the medio-dorsal nucleus of the thalamus (MDNT). To date, little is known about the functional significance of the MDNT in olfactory information processing. The aim of this article is to review and discuss thalamic function in olfaction. We draw upon research in human neuroimaging, neuropsychology, as well as animal and neurophysiological studies on the thalamus and MDNT in general, before focusing our discussion on the effects of MDNT lesions specific to olfactory function. Finally, although these data are currently limited and sometimes conflicting, especially those based upon human pathology, the putative roles of the MDNT in olfactory information processing and notably its role in attention, are discussed.

Olfactory identification in young relatives at risk for schizophrenia

OBJECTIVE

Olfactory identification deficits (OIDs) are seen in schizophrenia, but it is unclear whether they are state- or trait-related.

METHODS

We examined the prevalence of OIDs, as assessed by the University of Pennsylvania Smell Identification Test (UPSIT), and their correlations with prodromal symptoms in young relatives at risk for schizophrenia or schizoaffective disorder (HR-S).

RESULTS

UPSIT scores were lower in HR- S than in healthy controls, but were non-significant after covarying the effects of age, gender and IQ. OID deficits in HR-S were correlated, after covarying out the effects of age and IQ, with prodromal disorganisation.

CONCLUSION

The potential value of OID deficits as markers of psychopathological vulnerability in young relatives at risk for schizophrenia deserves further investigation.

Olfaction: a potential cognitive marker of psychiatric disorders

Cognitive deficits are well documented in psychiatric disorders, particularly in schizophrenia and depression. Cognitive activity roots in perceptions. However, research on sensorial alterations in psychiatric conditions has mainly focused on visual or auditory processes and less on olfaction. Here, we examine data on olfactory deficits in psychiatric patients using a systematic review of recent publications. Schizophrenic patients are mainly characterized by no reliable change in odour sensitivity and by a deficit in odour identification, recognition and discrimination. Depressed patients principally exhibit a deficit in the hedonic aspects of this perception, even if, in some case, alterations in sensitivity or identification are also found. Changes in odour perception are also found in dementia and in some neurodegenerative disease, but in this case alterations concern all aspects of the sensorial experience (detection threshold, identification and recognition). Taken together, these data indicate that olfactory abnormalities might be a marker of psychiatric conditions, with a specific pattern for each disease.

Increased processing speed for emotionally negative odors in schizophrenia

Although olfactory identification deficits in schizophrenia have been repeatedly demonstrated, some studies indicate that schizophrenia patients may also show an olfactory hypersensitivity. In addition, recent evidence points to impaired odor hedonics in schizophrenia. It was the aim of the present study to investigate olfactory information processing in schizophrenia patients with positive symptoms, by means of chemosensory event-related potential (CSERP) analysis. To control for modality-specific effects, these data were compared to visual event-related potentials (VERP), and in order to control for disorder-specific effects, the schizophrenia patients were compared to healthy controls as well as to patients with major depressive disorder (MDD). In each group, nine subjects were investigated. During EEG recording (32 scalp locations) two odors (positive valence: phenyl-ethylalcohol, negative valence: isobutyraldehyde) were presented using the constant flow method. Afterwards, two colors (red, yellow) were presented. The schizophrenia patients responded to both odors with shorter CSERP latencies than healthy controls and MDD-patients. This effect was most pronounced for the early processing (N1 component) of the emotionally negative odor. However, in response to colors, schizophrenia patients showed increased N1 latencies and a reduced P3 amplitude. It will be discussed whether schizophrenia patients with positive symptoms show a general processing advantage for emotionally negative (threat-related) information.

The vulnerability to alcohol and substance abuse in individuals diagnosed with schizophrenia

Individuals with schizophrenia are at increased risk for developing substance abuse disorders. Here, we consider factors that might elevate their risk for substance abuse. The tendency among schizophrenic individuals to overvalue drug-like rewards and to devalue the potential negative consequences of substance abuse may be a contributing factor to their substance abuse risk. This bias, which may partly reflect the convergence of glutamatergic and dopaminergic input to the limbic striatum, also may contribute to disadvantageous decision-making and other impulsive behavior. This propensity to seek drug-like rewards is augmented by alterations in nicotinic cholinergic, GABAergic, glutamatergic, and cannabinnoid receptor function associated with schizophrenia that increase the abuse liability of low doses of nicotine, ethanol, and perhaps cannabis, and augment the dysphoric effects of higher doses of ethanol and cannabis. The distortions in reward processing and altered response to substances of abuse also increase the likelihood that individuals with schizophrenia will self-medicate their subjective distress with abused substances. The focus on distinctions between motivation and reward with respect to substance abuse risk by schizophrenic patients suggests a need for a reconsideration of the construct of "negative symptoms" for this dually-diagnosed patient group.

Associations between olfactory identification and verbal memory in patients with schizophrenia, first-degree relatives, and non-psychiatric controls

OBJECTIVE

Olfactory identification deficits and verbal memory impairments may represent trait markers for schizophrenia. The aims of this study were to: (1) assess olfactory identification in patients, first-degree relatives, and non-psychiatric controls, (2) determine differences in verbal memory functioning in these three groups, and (3) study correlations between olfactory identification and three specific verbal memory domains.

METHOD

A total of 106 participants-41 patients with schizophrenia or related disorders, 27 relatives, and 38 controls-were assessed with the University of Pennsylvania Smell Identification Test (UPSIT) and the Wechsler Memory Scale-Third Edition. Linear mixed models, accounting for clustering within families and relevant covariates, were used to compare scores across groups and to examine associations between olfactory identification ability and the three verbal memory domains.

RESULTS

A group effect was apparent for all four measures, and relatives scored midway between patients and controls on all three memory domains. UPSIT scores were significantly correlated with all three forms of verbal memory. Age, verbal working memory, and auditory recognition delayed memory were independently predictive of UPSIT scores.

CONCLUSIONS

Impairments in olfactory identification and verbal memory appear to represent two correlated risk markers for schizophrenia, and frontal-temporal deficits likely account for both impairments.

Olfactory deficits, cognition and negative symptoms in early onset psychosis

BACKGROUND

Smell identification deficits (SID) are common in adult schizophrenia, where they are associated with negative symptoms and lower intelligence. However, smell identification has not been examined in adolescents with early onset psychosis, wherein diagnosis is often obscure, and there are few prognostic predictors.

METHOD

We examined smell identification, diagnosis, neuropsychological performance and symptoms in 26 well characterized adolescents with early onset psychosis, age 11-17 years.

RESULTS

SID existed in the sample and were more common in patients with schizophrenia and psychotic depression than in patients with psychosis NOS and bipolar disorder. As in adults, SID were significantly associated with greater negative symptoms and lower verbal IQ. However, the associations of verbal IQ (and other verbal tasks) to smell identification in this pediatric sample were explained by the relation of both of these types of variables to negative symptoms.

CONCLUSIONS

SID existed across this sample of youths with psychotic disorder, and were specifically related to typical characteristics of schizophrenia, such as negative symptoms and lower intelligence, but not to features of bipolar disorder, such as grandiosity. SID is a characteristic of early onset psychosis that may be useful for prognostic purposes.

Characterization of olfactory bulb glomeruli in schizophrenia

Olfactory deficits, observed in schizophrenia, may be associated with a disruption of synaptic transmission in the olfactory system. Using immunohistochemistry and optical densitometry, we assessed the integrity of the synaptic connection between olfactory receptor neurons and olfactory bulb target neurons in schizophrenia by comparing the level of eight proteins, expressed in the olfactory bulb glomeruli, among schizophrenia and control subjects. In schizophrenia, no change was observed in the levels of OMP, GAP43 and NCAM, proteins expressed by olfactory receptor neurons, suggesting an intact innervation of the olfactory bulb by these neurons. This was supported by the absence of change in calbindin level, which has been shown to decrease after the destruction of the olfactory epithelium. The level of synaptophysin, a pre-synaptic protein, was also unchanged. These findings suggested that axons of olfactory receptor neurons establish synapses with their olfactory bulb targets in schizophrenia. The absence of change in the level of poorly phosphorylated neurofilament of moderate and high molecular weight (NFM/HP) suggested no lack of dendritic innervation despite a previously seen reduction of glomerular MAP2 level in schizophrenia subjects. This and above findings were consistent with the absence of change in the level of beta-tubulin III, a protein expressed by neurons of both olfactory epithelium and bulb. Finally, we noted no significant decrease in trkB level, a neurotrophin receptor involved in the olfactory epithelium maintenance. This study showed no evidence of major structural alteration of the synapse between the olfactory epithelium and bulb in schizophrenia.

Olfactory impairment in monozygotic twins discordant for schizophrenia

OBJECTIVE

Several studies demonstrated olfactory dysfunction in patients with schizophrenia, some reported deficient olfaction in unaffected relatives of schizophrenics as well. This study differentially assessed olfactory acuity as well as smell identification and smell discrimination in monozygotic twins discordant for schizophrenia and healthy, monozygotic control twins, to determine the genetic basis of different olfactory modalities and their association to schizophrenia.

METHOD

The Sniffin'Sticks test,a comprehensive and standardized olfactory test, was employed to assess the olfactory function of 10 monozygotic twin pairs discordant for schizophrenia versus 10 age- and sexmatched healthy,monozygotic twin pairs.

RESULTS

Olfaction of affected monozygotic twins was globally impaired. Partial olfactory impairment of their unaffected co-twins may point to a genetic cause of olfactory impairment in schizophrenia. The influence of genetic factors was most evident for olfactory acuity and least evident for smell identification. All olfactory functions declined with duration of illness. Side of stimulus presentation did not influence olfactory performance.

CONCLUSIONS

Genetic factors associated with olfactory dysfunction may contribute to schizophrenia. The degree of the genetic influence on olfaction depends on the olfactory domain under examination.

From superior adaptation and function to brain dysfunction--the neglect of epigenetic factors

With optimal pregnancy conditions (natural, enriched diet which includes fish) African (Digo) infants are 3-4 weeks ahead of European/American infants in sensorimotor terms at birth, and during the first year. Infants of semi-aquatic sea-gypsies swim before they walk, and have superior visual acuity compared with us. With adverse pregnancy behaviour (fear of fat, a trend to dieting), neglecting the need for brain fat to secure normal brain development and function, we run a risk of dysfunction--death. Sudden Infant Death Syndrome victims have depressed birth weight, lower levels of marine fat in brainstem than controls, and >80 suffer multiple hypoxic episodes prior to death. Depressed birth weight (more than 10% below mean) is seen in learning and behaviour disorders, and a trend towards weights of less than 3kg is increasing, which supports a rise in antenatal sub optimality. Given marine fat deficiency in pregnancy and infancy, neurons starved for fuel could delay myelination and maturation in the latest developed Frontal Lobes. The phylogenetic oldest Lateral Frontal Lobe System (feed-back mechanism etc.) derived from olfactory bulb-amygdala, which crosses in Anterior Commisure is probably spared, while the Medial Frontal Lobe System derived from Hippocampus-Cingulum and crosses in Corpus Callosum (delayed response task) is most likely affected. The rise in infantile autism (intact vision and hearing) with deficit in delayed response task only, could suggest a deficit in the Medial Frontal Lobe System. The human species is unique; 70% of total energy to the foetus goes to development of the brain, which mainly consists of marine fat. It undergoes pervasive regressive events, before birth, in infancy and at puberty. Minimal retraction of neuronal arborisation is advantageous. Attributable to adverse pregnancy childrearing practice, excessive retraction is likely prenatally and in infancy. Pubertal age affects the fundamental property of nervous tissue, excitability: excessive excitatory drive is seen in early, and a deficiency in late puberty. It is postulated that with adequate marine fat, there is probably no risk of psychopathology at the extremes, whereas a deficiency could lead to paroxysmal (subcortical) dysfunction in early puberty, and breakdown of cortical circuitry and cognitive dysfunctions in late puberty. The post-pubertal psychoses, schizophrenia and manic-depressive psychosis at the extremes of the pubertal age continuum, with contrasting excitability and biological treatment, are probably the result of continuous dietary deficiency, which has inactivated the expression of genes for myelin development and oligodendrocyte-related genes in their production of myelin. The beneficial effect of marine fat in both disorders, in other CNS disorders as well as in developmental dyslexia (DD) and ADHD among others, supports our usual diet is persistently deficient. We have neglected the similarity of our great brain to other mammals, and our marine heritage. Given the amount of marine fat needed to secure normal brain development and function is not known, nor the present dietary level, it seems unduly conjectural to postulate that a dietary deficiency in marine fat is causing brain dysfunction and death. However, all observations point in the same direction: our diet focusing on protein mainly, is deficient, the deficiency is most pronounced in maternal nutrition and in infancy.

Trail making and olfaction in schizophrenia: implications for processing speed

BACKGROUND

Previous research has established a relationship between smell identification deficits (SID) and particular aspects of cognitive function among patients with schizophrenia.

OBJECTIVE

To expand the extant literature, we examined the relationship between SID and the Trail Making Test to determine if processing speed is related to SID.

METHODS

Our sample included 60 inpatients from the New York State Psychiatric Institute's Schizophrenia Research Unit. We considered age, deficit syndrome, verbal intelligence quotient, and education in our analyses due to their documented relationship to smell identification ability.

RESULTS

Trails A errors and Trails A seconds accounted for a significant amount of the variance in University of Pennsylvania Smell Identification Test scores in a regression analysis (R2=.10, P=.008 and R2=.05, P=.04).

CONCLUSION

Linking neurocognition to smell identification deficits may prove to be an essential marker for schizophrenia research.

Investigation of unirhinal olfactory identification in antipsychotic-free patients experiencing a first-episode schizophrenia

Although olfactory deficits have been reported in patients with schizophrenia, few studies have examined whether these deficits are lateralized or investigated their possible clinical correlates. In this study, we administered the University of Pennsylvania Smell Identification Test (UPSIT) unirhinally (one nostril at a time) to 15 patients experiencing a first-episode of schizophrenia and 17 healthy comparison subjects. Clinical and olfactory assessments were conducted on the same day in patients while they were antipsychotic drug-free. Patients performed more poorly compared to healthy volunteers in their ability to identify odors across both nostrils, but there were no group differences in right and left nostril impairment. Among patients, greater deficits in grooming and hygiene correlated significantly and more strongly with poorer ability in identifying odors presented to the left compared to the right nostril. Our findings suggest that deficits in grooming and hygiene, including poor body odor, observed in patients experiencing a first-episode of schizophrenia are associated with an impairment in left nostril, and possibly left hemisphere, olfactory processing.

The Smell Identification Test as a Measure of Olfactory Identification Ability in Schizophrenia and Healthy Populations: A Rasch Psychometric Study

This study examines University of Pennsylvania Smell Identification Test (UPSIT; R. L. Doty, 1995) performance in 133 controls and 54 chronic, medicated outpatients with schizophrenia (SZ) using item-response theory modeling. Results show that UPSIT items contribute to 1 factor, cover a range of 8 standard errors of measurement, and articulate 3 ability levels. Although it is not difficult enough to discriminate among persons of above-average ability, the test has diagnostic utility in detecting moderate impairment. Independent of item difficulty, 13 items differentiate patients from controls. When 45 patients and 45 controls were matched on gender and age, patient accuracy remained significantly reduced. The findings support the test's utility and demonstrate how traditional data analysis is insensitive to complexities in test performance.

A brief smell identification test discriminates between deficit and non-deficit schizophrenia

Evidence is accumulating that smell identification deficits (SID) and social dysfunction in schizophrenia may share a common pathophysiology. While most schizophrenia studies utilize the lengthy 40-item University of Pennsylvania Smell Identification Test (UPSIT) to assess smell identification ability, a brief 12-item smell identification test (B-SIT) has recently been constructed as a culturally neutral substitute for the UPSIT. By selecting the 12 items of the UPSIT from which the B-SIT was originally derived, we constructed a proxy for the B-SIT and compared the performance of 83 patients with schizophrenia to 69 normal subjects. We examined select properties of the B-SIT proxy in relation to the UPSIT to determine its efficacy for use in psychiatric populations. We considered the sensitivity of the B-SIT proxy and evaluated a cutoff score for identifying deficit syndrome schizophrenia (DS). The UPSIT and B-SIT proxy were significantly related in the patients (n=83, r=0.85, P=0.01) and in comparison subjects (n=69, r=0.83, P=0.01), and both measures similarly distinguished DS from non-deficit syndrome (non-DS) patients. The results of this study support the utility of the B-SIT for schizophrenia research and highlight the robustness of the relationship between SID and social dysfunction in schizophrenia.

Scent of a disorder: olfactory functioning in schizophrenia

The use of olfactory probes to assess frontal and temporal-limbic system functioning in patients with schizophrenia has garnered increasing interest among basic and clinical investigators. Deficits in odor identification, detection threshold sensitivity, discrimination, and memory have been reported and are thought to represent a centrally mediated deficit in the processing of this information. These impairments are seen in affected probands, first-degree family members, and those at risk for developing the illness, suggesting a genetic vulnerability or predisposition to chemosensory abnormalities. The observed deficits are not explained by gender, medication use, cognitive impairment, or smoking status, and support the hypothesis of primary dysfunction in the olfactory system. Along this same line, structural abnormalities in the peripheral and central olfactory brain regions, as well as disruptions of the basic physiology of this system, have been described. The study of olfactory processing in schizophrenia has already advanced the knowledge of the neural substrate for this disorder. Because the olfactory system continuously regenerates throughout life, it allows for a unique view of an ongoing neurodevelopmental process.

Deviant olfactory experiences, magical ideation, and olfactory sensitivity: a study with healthy German and Japanese subjects

Little is known about the relationship between olfactory hallucinations and olfactory sensitivity in psychiatric populations. However, in healthy subjects, a 'psychotic-like' feature, namely magical ideation, has been linked to deviant olfactory experiences. We thus assessed olfactory sensitivity, magical ideation and deviant olfactory experiences in 42 healthy subjects (21 Germans and 21 age- and gender-matched Japanese). The results show that: (1) Germans had significantly higher magical ideation scores and a higher frequency of deviant olfactory experiences than Japanese, and more Germans than Japanese reported having had deviant olfactory experiences at least once in their lives; (2) in Germans, the occurrence of deviant olfactory experiences was correlated with higher magical ideation scores; and (3) there was no relationship between olfactory sensitivity (olfactory thresholds) and either deviant olfactory experiences or magical ideation, respectively. We conclude that: (1) the lack of deviant olfactory experiences in Japanese may best be explained by cultural differences in the response attitude towards questionnaires requiring self-disclosure; (2) the positive relationship between magical ideation and deviant olfactory experiences strengthens the supposed link between 'psychotic-like' features in healthy populations and real hallucinations of psychiatric patients; and (3) the absence of a relationship between olfactory sensitivity and deviant olfactory experiences suggests that their anatomical-functional correlates within temporo-limbic regions may differ.

Odor identification, eye tracking and deficit syndrome schizophrenia

BACKGROUND

Deficit syndrome (DS) schizophrenia patients have smooth pursuit eye movement (SPEM) dysfunction. We examined if they also had smell identification deficits, since social affiliation is related to olfaction in other mammals.

METHODS

Sixty-seven patients had DS assessments: 31 patients had SPEM and 50 had Smell Identification Test (SIT) assessments, and 14 patients had both measurements.

RESULTS

DS patients had worse SPEM and SIT performance than the non-DS patients. Areas under the receiver-operator characteristic (ROC) curves for SIT and SPEM were both fairly accurate in identifying the DS. The odds ratio (OR) for the DS for impaired versus normal SPEM was 6.21 (95% confidence interval [CI]: 1.21, 32.25) and for microsmia versus normosmia was 10.4 (95% CI: 1.23, 88.18). Further analyses showed that the association of SIT with both SPEM and the DS could account for the SPEM-DS association.

CONCLUSIONS

We found a strong association between the DS and SIT scores suggesting that the neural substrates of olfaction may be related to social affiliation in humans, as they are in other mammals. These data further support the notion that the DS defines a homogeneous subgroup of schizophrenia patients and further suggest that dysfunction in the neural circuitry of olfaction may contribute to its pathophysiology.

Odor identification impairments in schizophrenia: relationship with demographic measures, clinical variables, and diagnostic subtypes

Smell identification deficits are consistently found in schizophrenia (SZ), but little is known about the nature and characterization of this deficit or its relationship to the phenomenology of the illness. This study aims to further delineate smell identification errors in SZ by examining the relationship of patient demographic differences with smell-identification performance. Our results showed that a patient's gender and education were related to odor-identification scores, with better performance seen in female patients and in those with greater educational attainment. However, there was no effect related to age, ethnicity, or socioeconomic status on odor identification. A smell identification deficit was also unrelated to clinical characteristics of the patients, including age at first hospitalization, number of psychiatric hospitalizations, and duration of illness. Odor identification also did not differ by SZ subtype, nor between SZ and schizoaffective disorder patients. These findings emphasize that odor identification deficits in SZ are unrelated to clinical illness features, cannot be explained by other confounds related to olfaction in the general population, and may be core features related to the SZ disease process.

Manic depressive psychosis and schizophrenia are neurological disorders at the extremes of CNS maturation and nutritional disorders associated with a deficit in marine fat

The maturational theory of brain development comprises manic depressive psychosis and schizophrenia. It holds that the disorders are part of human diversity in growth and maturation, which explains their ubiquity, shared susceptibility genes and multifactorial inheritance. Rate of maturation and age at puberty are the genotype; the disorders are localized at the extremes with normality in between. This is based on the association between onset of puberty and the final regressive event, with pruning of 40% of excitatory synapses leaving the inhibitory ones fairly unchanged. This makes excitability, a fundamental property of nervous tissue, a distinguishing factor: the earlier puberty, the greater excitability--the later puberty, the greater deficit. Biological treatment supports deviation from the norm: neuroleptics are convulsant; antidepressives are anti-epiletogenic. There is an association between onset of puberty and body-build: early maturers are pyknic broad-built, late ones linearly leptosomic. This discrepancy is similar to that in the two disorders, supporting the theory that body-build is the phenotype. Standard of living is the environmental factor, which affects pubertal age and shifts the panorama of mental illness accordingly. Unnatural death has increased with antipsychotics. Other treatment is needed. PUFA deficit has been observed in RBC in both disorders and striking improvements with addition of minor amounts of PUFA. This supports that dietary deficit might cause psychotic development and that prevention is possible. Other neurological disorders also profit from PUFA, underlining a general deficit in the diet.

Impaired olfactory identification in relatives of patients with familial schizophrenia

OBJECTIVE

Impaired olfactory identification ability has previously been demonstrated in patients with schizophrenia. This study assessed olfactory function in psychotic and nonpsychotic members of multigenerational families with familial schizophrenia to determine whether deficits were present in both groups.

METHOD

The University of Pennsylvania Smell Identification Test was administered birhinally to three groups of subjects aged less than 65 years: 19 psychotic and 27 nonpsychotic members of families with familial schizophrenia and 43 age- and sex-matched healthy volunteers.

RESULTS

Nonpsychotic family members had significantly higher mean University of Pennsylvania Smell Identification Test scores than psychotic family members but were impaired relative to the healthy volunteer group. These group differences could not be accounted for by age, sex, or smoking habit. Fifty-eight percent of the psychotic and 34% of the nonpsychotic family members performed in the microsmic (impaired) range, compared to 9% of the healthy volunteers.

CONCLUSIONS

Impaired olfactory deficits may aggregate in families with schizophrenia and may be indicative of a genetic predisposition to psychosis.

Regional cerebral glucose metabolism in never-medicated patients with schizophrenia

OBJECTIVE

The purpose of this study was to assess regional cerebral glucose metabolism in patients with schizophrenia who had never received antipsychotic medication and whose olfactory identification ability had been assessed. Two hypotheses were examined. First, the patients were compared with normal controls to determine whether differences in regional cerebral metabolism were apparent. Second, regional rates of metabolism were correlated with olfactory ability and the relation between them determined.

METHODS

The patient (n = 26) and control (n = 32) subjects were scanned at rest using positron emission tomography (PET) after administration of 18F-fluorodeoxyglucose (FDG). In addition, the University of Pennsylvania Smell Identification Test was administered to each patient.

RESULTS

Patients with schizophrenia had reduced rates of glucose metabolism in the right and left thalamus that reached significance if not corrected for multiple comparisons. However, if a Bonferroni correction was applied over the 27 regions of interest, the differences were not significant. Scores on the Smell Identification Test were negatively correlated with 8 regions of interest. When scores were analyzed using multiple regression, the left frontal cortex and the medial parietal cortex were significant predictors.

CONCLUSIONS

The finding of reduced metabolism in the thalami is consistent with some of the previous literature, whereas the negative correlations between specific regions and olfactory function are not consistent with studies using activation paradigms.

Unilateral olfactory perception and magical ideation

We assessed olfactory detection thresholds and discrimination abilities in 40 healthy right-handers (20 women and 20 men). All subjects were also required to complete the Magical Ideation (MI) scale, a well-validated 30-item schizotypy inventory. Over both nostrils, we found elevated thresholds for subjects with high MI scores (at or above the median score of 9.0) compared with those with low scores. In men but not women, specifically left-nostril acuity was inversely correlated to MI raw scores. MI was unrelated to olfactory discrimination performance. These results suggest an association, at least in healthy men, between even moderate signs of schizotypy and deficits in odor detection. The selective impairment of left-nostril performance adds to the growing evidence for left temporal lobe functional abnormalities in people high on MI. This laterality effect is known from previous studies in patients with schizophrenia. However, as a rule, in psychiatric patients olfactory identification rather than simple detection performance was found to be impaired, indicating that the integration of odor information is affected at different levels of processing in schizotypy compared with schizophrenia. Work with completely normal subjects may reasonably complement clinical studies of olfactory perception. Among its advantages are the good subject compliance and the absence of medication effects.

Olfaction and its alteration by nasal obstruction, rhinitis, and rhinosinusitis

The sense of smell has been largely ignored by otorhinolaryngologists, even though 1) its medical stewardship falls within their specialty's purview, 2) olfactory dysfunction is not uncommon in the general population, and 3) disorders of olfaction have significant quality of life, nutritional, and safety consequences. This report provides a succinct overview of the major intranasal neural systems present in humans (namely, cranial nerves O, I, and V, and the nonfunctional accessory [vomeronasal] organ system), along with a summary of notable findings resulting from the application of modern olfactory tests to patient populations, emphasizing diseases of the nose. Such tests have led to the discovery of significant influences of age, gender, smoking, toxic exposure, and genetics on the ability to smell. Within the field of otorhinolaryngology, they have revealed that 1) surgical and medical interventions in patients with rhinosinusitis do not, on average, lead to complete recovery of olfactory function, despite common beliefs to the contrary, and 2) associations are generally lacking between measures of airway patency and olfactory function in such cases. These findings have thrown into question the dogma that olfactory loss in rhinosinusitis is attributable primarily to blockage of airflow to the receptors and have led to histopathological studies demonstrating significant olfactory epithelial compromise in sinonasal syndromes.

Asymmetrical olfactory acuity and neuroleptic treatment in schizophrenia

Uni-rhinal olfactory acuity in schizophrenia was investigated in two experiments. The first assessed the presence of a predicted atypical asymmetry of nostril laterality and the second assessed the effect of antipsychotic treatment on the asymmetry. Although olfactory identification impairment has been well documented in schizophrenia, olfactory acuity has been neglected. This may be an oversight as cerebral structures of the mesial temporal lobe important to olfactory perception have often been implicated in the pathophysiology of schizophrenia and it is thus reasonable to postulate a primary impairment of olfactory acuity in schizophrenia. In addition, unmedicated patients with schizophrenia have exhibited asymmetrical laterality favouring the right over the left hemisphere in studies of visual, haptic, and auditory perception, and the few published prospective treatment studies have suggested a reversal of this asymmetry with first generation neuroleptic treatments. In experiment 1 a generalization of the perceptual asymmetry to olfactory acuity was examined by measurement of n-butanol olfactory thresholds with the Connecticut Chemosensory Perception Exam (CCPE) in an unmedicated sample of 17 patients with schizophrenia and 17 age, gender, and handedness matched normal controls. The patient sample showed an asymmetrical impairment of the left nostril that was not apparent in the normal control sample. In experiment 2, the CCPE was administered to a new sample of 10 patients with schizophrenia before and after neuroleptic treatment. The asymmetry observed in experiment 1 was replicated, and the relative advantage of the right nostril shifted to a relative advantage of the left nostril over the course of 8weeks of treatment. Results are discussed in relation to cerebral aspects of schizophrenia and potential implications to cognitive change from treatment.

Olfactory identification in combat-related posttraumatic stress disorder

Recent neuropsychological conceptualizations of posttraumatic stress disorder (PTSD) implicate dysfunction of the fronto-limbic system, a brain system thought to be involved in the mediation of emotion. However, few studies have examined fronto-limbic subregions, such as the orbitofrontal cortex, in PTSD. As a measure of orbitofrontal integrity, olfactory identification was assessed in 26 Vietnam War veterans with PTSD, 25 Vietnam War veterans without mental disorders, and 17 Vietnam-era, non-war-zone veterans without mental disorders. Relative to veterans without PTSD, those diagnosed with PTSD were less proficient in odor identification and verbal learning but not on other cognitive tests sensitive to dorsolateral prefrontal and mesial temporal functioning. Results bolster prior research indicating fronto-limbic dysfunction in PTSD, and suggest involvement of the orbitofrontal region.

Olfactory identification and psychosis

BACKGROUND

Olfactory identification performance has been investigated in several psychiatric populations, with deficits most commonly reported in patients with schizophrenia. In this study, olfactory identification performance was investigated in a more homogenous group of treatment-refractory patients with schizophrenia (T-RS) and in two additional psychiatric groups who demonstrate some similarities to the patients with schizophrenia in terms of symptomotology and medication regime.

METHODS

The olfactory identification performance of 16 T-RS patients was assessed using the University of Pennsylvania Smell Identification Test (UPSIT) and compared to that of 16 normal control subjects and two other psychiatric patient groups: 19 affective disorder patients requiring maintenance antipsychotic medication and 20 affective disorder patients not receiving antipsychotic medication.

RESULTS

The olfactory identification performance of T-RS patients was significantly lower than that of normal controls but not significantly different from either affective disorder group. The olfactory identification performance of affective disorder patients receiving antipsychotic medication was significantly lower than that of affective disorder patients not receiving antipsychotic medication.

DISCUSSION

Results are discussed in the context of a possible link between psychotic symptomotology and olfactory identification performance.