A behavioural and functional neuroimaging investigation into the effects of nicotine on sensorimotor gating in healthy subjects and persons with schizophrenia

The Association Between Chronic Tobacco Smoking and Brain Alterations in Schizophrenia: A Systematic Review of Magnetic Resonance Imaging Studies

BACKGROUND AND HYPOTHESIS

The high co-occurrence of tobacco smoking in patients with schizophrenia spectrum disorders (SSD) poses a serious health concern, linked to increased mortality and worse clinical outcomes. The mechanisms underlying this co-occurrence are not fully understood.

STUDY DESIGN

Addressing the need for a comprehensive overview of the impact of tobacco use on SSD neurobiology, we conducted a systematic review of neuroimaging studies (including structural, functional, and neurochemical magnetic resonance imaging studies) that investigate the association between chronic tobacco smoking and brain alterations in patients with SSD.

STUDY RESULTS

Eight structural and fourteen functional studies were included. Structural studies show widespread independent and additive reductions in gray matter in relation to smoking and SSD. The majority of functional studies suggest that smoking might be associated with improvements in connectivity deficits linked to SSD. However, the limited number of and high amount of cross-sectional studies, and high between-studies sample overlap prevent a conclusive determination of the nature and extent of the impact of smoking on brain functioning in patients with SSD. Overall, functional results imply a distinct neurobiological mechanism for tobacco addiction in patients with SSD, possibly attributed to differences at the nicotinic acetylcholine receptor level.

CONCLUSIONS

Our findings highlight the need for more longitudinal and exposure-dependent studies to differentiate between inherent neurobiological differences and the (long-term) effects of smoking in SSD, and to unravel the complex interaction between smoking and schizophrenia at various disease stages. This could inform more effective strategies addressing smoking susceptibility in SSD, potentially improving clinical outcomes.

Comparative Analysis of Dopaminergic and Cholinergic Mechanisms of Sensory and Sensorimotor Gating in Healthy Individuals and in Patients With Schizophrenia

Sensory and sensorimotor gating provide the early processing of information under conditions of rapid presentation of multiple stimuli. Gating deficiency is observed in various psychopathologies, in particular, in schizophrenia. However, there is also a significant proportion of people in the general population with low filtration rates who do not show any noticeable cognitive decline. The review article presents a comparative analysis of existing data on the peculiarities of cholinergic and dopaminergic mechanisms associated with lowering gating in healthy individuals and in patients with schizophrenia. The differences in gating mechanisms in cohorts of healthy individuals and those with schizophrenia are discussed.

Biologically Active Compounds Present in Tobacco Smoke: Potential Interactions Between Smoking and Mental Health

Tobacco dependence remains one of the major preventable causes of premature morbidity and mortality worldwide. There are well over 8,000 compounds present in tobacco and tobacco smoke, but we do not know what effect, if any, many of them have on smokers. Major interest has been on nicotine, as well as on toxic and carcinogenic effects and several major and minor components of tobacco smoke responsible for the negative health effects of smoking have been elucidated. Smokers themselves report a variety of positive effects from smoking, including effects on depression, anxiety and mental acuity. Smoking has also been shown to have protective effects in Parkinson’s Disease. Are the subjective reports of a positive effect of smoking due to nicotine, of some other components of tobacco smoke, or are they a manifestation of the relief from nicotine withdrawal symptoms that smoking provides? This mini-review summarises what is currently known about the components of tobacco smoke with potential to have positive effects on smokers.

Nicotine Administration Normalizes Behavioral and Neurophysiological Perturbations in the MAM Rodent Model of Schizophrenia

BACKGROUND

The present study utilized the methylazoxymethanol (MAM) neurodevelopmental rodent model of schizophrenia (SCZ) to evaluate the hypothesis that individuals with SCZ smoke in an attempt to "self-medicate" their symptoms through nicotine (NIC) intake.

METHODS

To explore this question, we examined the effects of acute and chronic administration of NIC in 2 established behavioral tests known to be disrupted in the MAM model: prepulse inhibition of startle and novel object recognition. Additionally, we assessed the effects of acute and chronic NIC on 2 indices of the pathophysiology of SCZ modeled by MAM, elevated dopamine neuron population activity in the ventral tegmental area and neuronal activity in the ventral hippocampus, using in vivo electrophysiological recordings.

RESULTS

Our findings demonstrated that both acute and chronic administration of NIC significantly improved deficits in prepulse inhibition of startle and novel object recognition among MAM rats and normalized elevated ventral tegmental area and ventral hippocampal neuronal activity in these animals.

CONCLUSION

Together, these findings of NIC-induced improvement of deficits lend support for a "self-medication" hypothesis behind increased cigarette smoking in SCZ and illustrate the potential utility of nicotinic modulation in future pharmacotherapies for certain SCZ symptoms.

Prepulse inhibition based grouping of rats and assessing differences in response to pharmacological agents

Schizophrenia modeling by disrupting prepulse inhibition (PPI) is one of the most frequently used psycho-pharmacological methods by administering pharmacological agents to stimulate disruption. However, since PPI is also a biological indicator of schizophrenia, it is possible to classify subjects based on their basal PPI values and group them as "low inhibition" and "high inhibition without taking any pharmacological agent. Therefore this study was conducted to show that rats can be divided into groups in terms of susceptibility to schizophrenia according to basal PPI values. It was also observed that these groups might give different responses to different pharmacological agents (apomorphine, amphetamine, MK-801, scopolamine, nicotine, caffeine). Male Sprague Dawley rats (250-350 g) were used in the study. To examine the effects of different pharmacological agents on the groups, apomorphine (0.5 mg/kg and 1 mg/kg), amphetamine (4 mg/kg), MK-801 (0.05 mg/kg and 0.15 mg/kg), scopolamine (0.4 mg/kg), nicotine (1 mg/kg) and caffeine (10 mg/kg and 30 mg/kg) were used. Amphetamine showed a disruptive effect on PPI in both low and high inhibitory groups, while apomorphine, MK-801, scopolamine, and nicotine showed PPI decrease only in the high inhibitory group. Besides, caffeine decreased PPI levels at two doses in the high inhibitory group; however, 10 mg/kg dose caffeine was increased only in the low inhibitory group. According to the data obtained from this study, rats can be grouped with baseline inhibition values by using PPI, and response differences of pharmacological agents to groups may vary.

Prepulse Inhibition of the Auditory Startle Reflex Assessment as a Hallmark of Brainstem Sensorimotor Gating Mechanisms

When a low-salience stimulus of any type of sensory modality-auditory, visual, tactile-immediately precedes an unexpected startle-like stimulus, such as the acoustic startle reflex, the startle motor reaction becomes less pronounced or is even abolished. This phenomenon is known as prepulse inhibition (PPI), and it provides a quantitative measure of central processing by filtering out irrelevant stimuli. As PPI implies plasticity of a reflex and is related to automatic or attentional processes, depending on the interstimulus intervals, this behavioral paradigm might be considered a potential marker of short- and long-term plasticity. Assessment of PPI is directly related to the examination of neural sensorimotor gating mechanisms, which are plastic-adaptive operations for preventing overstimulation and helping the brain to focus on a specific stimulus among other distracters. Despite their obvious importance in normal brain activity, little is known about the intimate physiology, circuitry, and neurochemistry of sensorimotor gating mechanisms. In this work, we extensively review the current literature focusing on studies that used state-of-the-art techniques to interrogate the neuroanatomy, connectomics, neurotransmitter-receptor functions, and sex-derived differences in the PPI process, and how we can harness it as biological marker in neurological and psychiatric pathology.

Prepulse inhibition and “psychosis-proneness” in healthy individuals: An fMRI study

Objective

Prepulse inhibition (PPI) of the startle response provides an operational index of sensorimotor gating that is reliably demonstrable in both human and animal subjects. Patients with schizophrenia, first-degree relatives of patients with schizophrenia, patients with schizotypal personality disorder and healthy individuals scoring high on psychometric measures of psychosis-proneness display reduced PPI. This study examined associations between individual differences in “psychosis-proneness” and brain activity during a tactile prepulse inhibition paradigm previously found to reveal activation in controls and deficient activation in schizophrenia patients in the striatum, thalamus, insula, hippocampal, temporal, inferior frontal, and inferior parietal regions.

Methods

Fourteen right-handed healthy men underwent psychophysiological testing and functional magnetic resonance imaging (fMRI) during a 15-min tactile PPI paradigm involving the use of tactile stimuli as both the pulse (a 40-ms presentation of 30 psi air-puff) and the prepulse (a 20-ms presentation of 6 psi air-puff presented 30-ms or 120-ms before the pulse). Individual differences in “psychosis-proneness” were assessed with Psychoticism scale of the Eysenck Personality Questionnaire-Revised (EPQ-R).

Results

High psychosis-proneness was associated with lower PPI and reduced activity in the inferior frontal gyrus, insula extending to putamen and thalamus, parahippocampal gyrus, and inferior parietal and middle temporal regions. No regional activity correlated positively with psychosis-proneness.

Conclusions

The present observations extend the findings observed previously in people with schizophrenia to people with high psychosis-proneness, providing support to continuum theories of psychosis with implications for understanding trait-related neural deficits in schizophrenia.

Identification of 34 genes conferring genetic and pharmacological risk for the comorbidity of schizophrenia and smoking behaviors

The prevalence of smoking is significantly higher in persons with schizophrenia (SCZ) than in the general population. However, the biological mechanisms of the comorbidity of smoking and SCZ are largely unknown. This study aimed to reveal shared biological pathways for the two diseases by analyzing data from two genome-wide association studies with a total sample size of 153,898. With pathway-based analysis, we first discovered 18 significantly enriched pathways shared by SCZ and smoking, which were classified into five groups: postsynaptic density, cadherin binding, dendritic spine, long-term depression, and axon guidance. Then, by using an integrative analysis of genetic, epigenetic, and expression data, we found not only 34 critical genes (e.g., PRKCZ, ARHGEF3, and CDKN1A) but also various risk-associated SNPs in these genes, which convey susceptibility to the comorbidity of the two disorders. Finally, using both in vivo and in vitro data, we demonstrated that the expression profiles of the 34 genes were significantly altered by multiple psychotropic drugs. Together, this multi-omics study not only reveals target genes for new drugs to treat SCZ but also reveals new insights into the shared genetic vulnerabilities of SCZ and smoking behaviors.

Neurobiological Determinants of Tobacco Smoking in Schizophrenia

Purpose of review: To provide an overview of the underlying neurobiology of tobacco smoking in schizophrenia, and implications for treatment of this comorbidity. Recent findings: Explanations for heavy tobacco smoking in schizophrenia include pro-cognitive effects of nicotine, and remediation of the underlying pathophysiology of schizophrenia. Nicotine may ameliorate neurochemical deficits through nicotine acetylcholine receptors (nAChRs) located on the dopamine, glutamate, and GABA neurons. Neurophysiological indices including electroencephalography, electromyography, and smooth pursuit eye movement (SPEM) paradigms may be biomarkers for underlying neuronal imbalances that contribute to the specific risk of tobacco smoking initiation, maintenance, and difficulty quitting within schizophrenia. Moreover, several social factors including socioeconomic factors and permissive smoking culture in mental health facilities, may contribute to the smoking behaviors (initiation, maintenance, and inability to quit smoking) within this disorder. Summary: Tobacco smoking may alleviate specific symptoms associated with schizophrenia. Understanding the neurobiological underpinnings and psychosocial determinants of this comorbidity may better explain these potential beneficial effects, while also providing important insights into effective treatments for smoking cessation.

Sensorimotor gating characteristics of violent men with comorbid psychosis and dissocial personality disorder: Relationship with antisocial traits and psychosocial deprivation

Evidence suggests violence amongst those with psychosis is not aetiologically homogeneous, and that a large proportion of those who engage in violent behaviour have a comorbid antisocial personality disorder. Initial investigations indicate that this subgroup has distinct historical and neuropsychological characteristics, which may indicate diverse treatment needs. This study investigated sensorimotor gating characteristics of violent men with diagnoses of both psychosis and dissocial personality disorder (DPD) (n=21) relative to violent men with psychosis alone (n=12), DPD alone (n=14) and healthy, non-violent male controls (n=27), using the prepulse inhibition (PPI) paradigm. The results indicated that, relative to the psychosis alone and healthy control groups, the comorbid group had lower PPI, especially at 60-ms prepulse-to-pulse interval. The DPD group took an intermediary position and did not differ from any group. Antisocial personality traits (factor two scores of the Psychopathy Checklist - Revised), and greater severity of childhood psychosocial deprivation (including physical and sexual abuse), were significantly correlated with poor PPI across the clinical sample. The findings suggest diverse sensorimotor gating profiles amongst subgroups of violent offenders, with comorbid psychosis and DPD showing most impairment. This is consistent with a 'double dose' of deficit explanation amongst those with both diagnoses, explained at least in part by presence of antisocial personality traits and childhood psychosocial deprivation.

A cross-sectional analysis of factors associated with the intention to engage in tobacco treatment among inpatients in a state psychiatric hospital

WHAT IS KNOWN ON THE SUBJECT?: People admitted to psychiatric facilities have high rates of tobacco use and hospitalizations present an opportunity for patients to have conversations about tobacco use treatment. Clinicians may believe that people with mental illnesses are not interested in quitting or that they do not understand the importance of treatment. Positive attitudes towards tobacco treatment, viewing that participating in treatment is normal care, and feeling that one is quite able to participate in such treatment predicts intentions to participate in treatment, which, in turn, predicts actual participation. WHAT DOES THIS PAPER ADD TO EXISTING KNOWLEDGE?: Psychiatric patients who use tobacco use report poor prior involvement with tobacco treatment. Positive attitudes towards, encouraging opinions of other people about, and having a sense of control over taking part in tobacco treatment increases plans to engage in treatment. Having a sense of control in taking part in tobacco treatment is strongly associated with prior experiences with evidence-based treatment. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: Because psychiatric hospitalizations are an opportunity for addressing tobacco use and treatment, clinicians should be prepared to support willing patients, especially those with prior substance use histories. Support should include providing them with information regarding tobacco treatment options during their hospital stay and ways that they can continue to receive care after discharge. Clinicians should be promoters of pro-tobacco treatment attitudes and supporting patients' sense of control over participating in treatment during hospitalization.

ABSTRACT

Introduction Hospitalized tobacco users with mental illnesses (MI) may face several barriers to stopping smoking. However, motivational factors that affect the intention to engage in tobacco treatment have been shown to predict actual engagement. Aim To use the Theory of Planned Behavior to assess intentions to and prior experiences of engaging in evidence-based tobacco treatment among hospitalized individuals with MI. Method A cross-sectional survey was conducted among 115 patients in a state psychiatric hospital. Multivariate analyses were used to examine associations with the intentions and prior experiences of engaging in tobacco treatment. Results After controlling for demographic and smoking history, attitudes, subjective norms and perceived behavioural control towards engaging in tobacco treatment were significantly associated with intentions towards treatment engagement. Only higher scores on perceived behavioural control and lower education levels were associated with reported prior experiences of tobacco treatment. Discussion The low prior treatment engagement scores, but relatively higher intention to engage scores among participants suggests the need for deliberate support for evidence-based tobacco treatment during psychiatric hospitalizations. Implications for practice Clinician training in tobacco treatment can promote self-efficacy to engage patients while supporting patients' control so that tobacco treatment is an expected component of psychiatric care.

Ineffectiveness of the Tobacco Hazards Prevention Act in patients with severe and persistent mental illness

OBJECTIVES

The effect of the Tobacco Hazards Prevention Act (THPA) on the reduction of tobacco use in the general population in Taiwan is understood. However, there has been little research on how these policies affect people with severe and persistent mental illness (SPMI). Hence, the influence of the THPA on daily cigarette use by patients with SPMI was investigated in a 3-year follow-up. The risk and protective factors in smoking behavior and cessation were investigated.

STUDY DESIGN

This is an observational study.

METHODS

A total of 144 participants (78 of whom had smoked >100 cigarettes throughout their lifetime) were randomly selected from a healthcare network. Then, 100 of 144 patients with SPMI, included 50 smokers and 50 non-smokers, have agreed with 1st year follow-up. Eighty-two patients with SPMI, consisted of 44 smokers and 38 non-smokers, have agreed with 2nd year follow-up.

RESULTS

Although women were less likely to smoke than men, those who did smoke reduced the number of cigarettes less than men over the 3-year period. Less-educated patients were more likely to smoke than those who were more educated but reduced the number of daily cigarettes more after implementation of the THPA. Maternal overprotection was a risk factor and paternal care a protective factor for smoking. Addiction, a perception of pleasure, interpersonal relationships, and self-destructive behavior increased cigarette smoking. Patients perceived that smoking alleviated their depressive symptoms.

CONCLUSIONS

The THPA was ineffective for patients with SPMI. Some factors had different effects on the development of smoking behavior and the cessation process. Understanding the etiology of smoking can help policymakers establish more effective programs for smoking prevention and cessation.

Task Performance Modulates Functional Connectivity Involving the Dorsolateral Prefrontal Cortex in Patients with Schizophrenia

Previous studies have suggested that patients with schizophrenia and healthy controls exhibit differential activation of and connectivity involving the dorsolateral prefrontal cortex (DLPFC) during working memory tasks, though their findings remain inconsistent. The functional integration perspective further suggests that working memory performance also modulates differences in functional interactions of the DLPFC between patients and controls. To explore this possibility, 45 healthy controls and 45 patients with schizophrenia were recruited to perform a 2-back task during functional magnetic resonance imaging (fMRI). Each group was further divided into two subgroups based on task performance to examine the modulatory effect of performance on functional interactions of the DLPFC, as measured via psychophysiological interaction (PPI) analyses. We observed that, in patients with schizophrenia who exhibited impaired working memory capacity and decreased brain activation/deactivation, functional interactions between the right/left DLPFC and angular cortex were decreased relative to those of healthy controls. Furthermore, we observed an interaction effect of working memory performance and diagnosis on functional connectivity between the right/left DLPFC seed region and posterior regions such as the angular cortex, fusiform gyrus, and middle occipital gyrus. This interaction effect was mainly driven by the negative correlation between functional connectivity and performance in healthy controls, and by the positive correlation in patients with schizophrenia. These results demonstrate the effects of inter-individual differences in working memory performance on functional interactions between the DLPFC and posterior regions in patients with schizophrenia as well as healthy controls, which may shed new light on the neural basis of working memory.

Factors Associated With Staff Engagement in Patients' Tobacco Treatment in a State Psychiatric Facility

BACKGROUND

Persons with mental illnesses (MI) who use tobacco are likely to experience poorer physical health and worsened psychiatric symptomology as compared to their non-tobacco-using counterparts. Therefore, engaging them in treatment is an important aspect of evidence-based care.

OBJECTIVE

To use the theory of planned behavior to examine factors associated with intentions to provide and the provision of evidence-based tobacco treatment.

DESIGN

This study is based on a cross-sectional analysis of survey data from 195 staff at a state psychiatric hospital.

RESULTS

When controlling for demographic variables, attitudes, subjective norms, and perceived behavioral control toward providing tobacco treatment were associated with intentions to provide tobacco treatment, but only subjective norms and perceived behavioral control were associated with reported provision of evidence-based tobacco treatment.

CONCLUSIONS

Understanding factors that influence provider delivery of tobacco treatment can better determine strategies to reduce the disproportionate tobacco use and related illnesses in behavioral health settings.

CHRNA4 was associated with prepulse inhibition of schizophrenia in Chinese: a pilot study

INTRODUCTION

Prepulse inhibition (PPI) of the auditory startle reflex, as an operational measurement used to evaluate the function of brain sensorimotor gating, appears to be a sensitive potential endophenotype for schizophrenia. CHRNA4 is highly expressed in the central nervous system and has been demonstrated to be significantly associated with schizophrenia by previous studies. The purpose of the current study was to evaluate the effect of CHRNA4 on PPI and acoustic startle parameters in schizophrenia.

METHODS

77 patients with schizophrenia and 62 controls were administered the test PPI, and 3 single nucleotide polymorphisms (SNPs) (rs3746372, rs1044396, and rs3787140) of CHRNA4 were genotyped in these subjects.

RESULTS

Patients with schizophrenia showed significantly lower levels of PPI at the 120 ms prepulse intervals and longer peak latency than controls, and the GG genotype of rs3746372 and the TT genotype of rs1044396 were associated with decreased PPI levels in schizophrenia but not in controls.

CONCLUSION

PPI may be influenced by the polymorphisms of the CHRNA4 in schizophrenia and it may be a potential endophenotype of schizophrenia. An independent replication would greatly increase the value of this study.

Nicotine ameliorates schizophrenia-like cognitive deficits induced by maternal LPS exposure: a study in rats

Maternal exposure to infectious agents is a predisposing factor for schizophrenia with associated cognitive deficits in offspring. A high incidence of smoking in these individuals in adulthood might be, at least in part, due to the cognitive-enhancing effects of nicotine. Here, we have used prenatal exposure to maternal lipopolysaccharide (LPS, bacterial endotoxin) at different time points as a model for cognitive deficits in schizophrenia to determine whether nicotine reverses any associated impairments. Pregnant rats were treated subcutaneously with LPS (0.5 mg/kg) at one of three neurodevelopmental time periods [gestation days (GD) 10-11, 15-16, 18-19]. Cognitive assessment in male offspring commenced in early adulthood [postnatal day (PND) 60] and included: prepulse inhibition (PPI), latent inhibition (LI) and delayed non-matching to sample (DNMTS). Following PND 100, daily nicotine injections (0.6 mg/kg, subcutaneously) were administered, and animals were re-tested in the same tasks (PND 110). Only maternal LPS exposure early during fetal neurodevelopment (GD 10-11) resulted in deficits in all tests compared to animals that had been prenatally exposed to saline at the same gestational time point. Repeated nicotine treatment led to global (PPI) and selective (LI) improvements in performance. Early but not later prenatal LPS exposure induced consistent deficits in cognitive tests with relevance for schizophrenia. Nicotine reversed the LPS-induced deficits in selective attention (LI) and induced a global enhancement of sensorimotor gating (PPI).

Cognitive Dysfunction, Affective States, and Vulnerability to Nicotine Addiction: A Multifactorial Perspective

Although smoking prevalence has declined in recent years, certain subpopulations continue to smoke at disproportionately high rates and show resistance to cessation treatments. Individuals showing cognitive and affective impairments, including emotional distress and deficits in attention, memory, and inhibitory control, particularly in the context of psychiatric conditions, such as attention-deficit hyperactivity disorder, schizophrenia, and mood disorders, are at higher risk for tobacco addiction. Nicotine has been shown to improve cognitive and emotional processing in some conditions, including during tobacco abstinence. Self-medication of cognitive deficits or negative affect has been proposed to underlie high rates of tobacco smoking among people with psychiatric disorders. However, pre-existing cognitive and mood disorders may also influence the development and maintenance of nicotine dependence, by biasing nicotine-induced alterations in information processing and associative learning, decision-making, and inhibitory control. Here, we discuss the potential forms of contribution of cognitive and affective deficits to nicotine addiction-related processes, by reviewing major clinical and preclinical studies investigating either the procognitive and therapeutic action of nicotine or the putative primary role of cognitive and emotional impairments in addiction-like features.

Acoustic startle and prepulse inhibition predict smoking lapse in posttraumatic stress disorder

Most smokers who attempt to quit lapse within the first week and are ultimately unsuccessful in their quit attempt. Nicotine withdrawal exacerbates cognitive and attentional problems and may be one factor in smoking relapse. The startle reflex response and prepulse inhibition (PPI) of the response are sensitive to arousal and early attentional dysregulation. The current study examined whether startle response and PPI are related to early smoking lapse, and if this differs in people with and without posttraumatic stress disorder (PTSD). Participants with (N = 34) and without (N = 57) PTSD completed a startle reflex and PPI assessment during (1) ad lib smoking (2) on the first day of abstinence during a quit attempt. Most (88%) participants lapsed within the first week of the quit attempt. PTSD status predicted shorter time to lapse. Larger startle magnitude and greater PPI predicted a longer duration before smoking lapse. When diagnostic groups were examined separately, greater PPI predicted a longer successful quit attempt only in participants with a PTSD diagnosis. The startle reflex response and PPI may provide an objective, neurophysiological evaluation of regulation of arousal and early attentional processes by nicotine, which are important factors in smoking cessation success.

Nicotine receptors mediating sensorimotor gating and its enhancement by systemic nicotine

Prepulse inhibition (PPI) of startle occurs when intensity stimuli precede stronger startle-inducing stimuli by 10–1000 ms. PPI deficits are found in individuals with schizophrenia and other psychiatric disorders, and they correlate with other cognitive impairments. Animal research and clinical studies have demonstrated that both PPI and cognitive function can be enhanced by nicotine. PPI has been shown to be mediated, at least in part, by mesopontine cholinergic neurons that project to pontine startle neurons and activate muscarinic and potentially nicotine receptors (nAChRs). The subtypes and anatomical location of nAChRs involved in mediating and modulating PPI remain unresolved. We tested the hypothesis that nAChRs that are expressed by pontine startle neurons contribute to PPI. We also explored whether or not these pontine receptors are responsible for the nicotine enhancement of PPI. While systemic administration of nAChR antagonists had limited effects on PPI, PnC microinfusions of the non-α7nAChR preferring antagonist TMPH, but not of the α7nAChR antagonist MLA, into the PnC significantly reduced PPI. Electrophysiological recordings from startle-mediating PnC neurons confirmed that nicotine affects excitability of PnC neurons, which could be antagonized by TMPH, but not by MLA, indicating the expression of non-α7nAChR. In contrast, systemic nicotine enhancement of PPI was only reversed by systemic MLA and not by TMPH or local microinfusions of MLA into the PnC. In summary, our data indicate that non-α7nAChRs in the PnC contribute to PPI at stimulus intervals of 100 ms or less, whereas activation of α7nAChRs in other brain areas is responsible for the systemic nicotine enhancement of PPI. This is important knowledge for the correct interpretation of behavioral, preclinical, and clinical data as well as for developing drugs for the amelioration of PPI deficits and the enhancement of cognitive function.

Smoking in schizophrenia: cognitive impact of nicotine and relationship to smoking motivators

Smoking prevalence in schizophrenia is significantly elevated relative to other clinical and to non-clinical groups. The cognitive self-medication hypothesis attributes this to the beneficial effects of nicotine on illness-related cognitive deficits. Significant effects of nicotine have been observed on visual spatial working memory (VSWM), sustained attention (Continuous Performance Test - Identical Pairs; CPT-IP) and prepulse inhibition (PPI). It remains unclear whether these neurophysiological and neurocognitive effects of nicotine influence self-reported smoking motivation. To explore the relationship between nicotine effects on cognition and self-reported smoking motivation in schizophrenia and non-psychiatric control smokers, the impact of smoking abstinence and reinstatement was examined across three cognitive indices (VSWM, CPT-IP, PPI) and compared to self-reported smoking motivation (Modified Reasons for Smoking Scale revised to include 'cognitive motivators'). Cognitive function was assessed after 'typical' smoking and overnight abstinence. Schizophrenia smokers (but not controls) demonstrated significantly less error on the VSWM task in the smoking relative to abstinent condition. Control (but not schizophrenia) smokers, showed evidence of CPT-IP improvement in the smoking relative to abstinent condition. The overall profile of smoking motivation was comparable between groups. However, significant relationships between subjective and objective indices of smoking related cognitive change were observed for controls. Differential effects of nicotine on cognition have been hypothesised to influence the pattern and persistence of smoking in schizophrenia. These preliminary findings indicate that evidence for such effects is apparent even in small samples - particularly for VSWM. This is the first study to show that neurocognitive effects of smoking may influence self-reported smoking motivation.

Effects of smoking on the acoustic startle response and prepulse inhibition in smokers with and without posttraumatic stress disorder

RATIONALE

Cigarette smokers smoke in part because nicotine helps regulate attention. Prepulse inhibition (PPI) of the startle reflex is a measure of early attentional gating that is reduced in abstinent smokers and in groups with attention regulation difficulties. Attention difficulties are found in people with posttraumatic stress disorder (PTSD).

OBJECTIVES

The aim of this study is to assess whether smoking and abstinence differentially affect the startle response and PPI in smokers with and without PTSD.

METHODS

Startle response and PPI (prepulses at 60, 120, or 240 ms) were measured in smokers with (N = 39) and without (N = 61) PTSD, while smoking and again while abstinent.

RESULTS

Participants with PTSD produced both larger magnitude and faster latency startle responses than controls. Across groups, PPI was greater when smoking than when abstinent. The PTSD and control group exhibited different patterns of PPI across prepulse intervals when smoking and when abstinent. Older age was associated with reduced PPI, but only when abstinent from smoking.

CONCLUSIONS

The effects of PTSD on startle magnitude and of smoking on PPI replicate earlier studies. The different pattern of PPI exhibited in PTSD and control groups across prepulse intervals, while smoking and abstinent suggests that previous research on smoking and PPI has been limited by not including longer prepulse intervals, and that nicotine may affect the time course as well as increasing the level of PPI. The reduced PPI among older participants during abstinence suggests that nicotine may play a role in maintaining attention in older smokers, which may motivate continued smoking in older individuals.

Lower hippocampal volume predicts decrements in lane control among drivers with amnestic mild cognitive impairment

OBJECTIVES

There are few methods to discern driving risks in patients with early dementia and mild cognitive impairment (MCI). We aimed to determine whether structural magnetic resonance imaging (MRI) of the hippocampus-a biomarker of probable Alzheimer pathology and a measure of disease severity in those affected--is linked to objective ratings of on-road driving performance in older adults with and without amnestic MCI.

METHODS

In all, 49 consensus-diagnosed participants from an Alzheimer's Disease Research Center (15 diagnosed with amnestic MCI and 34 demographically similar controls) underwent structural MRI and on-road driving assessments.

RESULTS

Mild atrophy of the left hippocampus was associated with less-than-optimal ratings in lane control but not with other discrete driving skills. Decrements in left hippocampal volume conferred higher risk for less-than-optimal lane control ratings in the patients with MCI (B = -1.63, standard error [SE] = .74, Wald = 4.85, P = .028), but not in controls (B = 0.13, SE = .415, Wald = 0.10, P = .752). The odds ratio and 95% confidence interval for below-optimal lane control in the MCI group was 4.41 (1.18-16.36), which was attenuated to 3.46 (0.88-13.60) after accounting for the contribution of left hippocampal volume.

CONCLUSION

These findings suggest that there may be a link between hippocampal atrophy and difficulties with lane control in persons with amnestic MCI. Further study appears warranted to better discern patterns of brain atrophy in MCI and Alzheimer disease and whether these could be early markers of clinically meaningful driving risk.

Association study of polymorphisms in the alpha 7 nicotinic acetylcholine receptor subunit and catechol-o-methyl transferase genes with sensory gating in first-episode schizophrenia

The purpose of the current study was to explore the association of auditory P50 sensory gating (P50) and prepulse inhibition (PPI) of schizophrenia with polymorphisms in the CHRNA7 and COMT genes. One hundred and fourty patients with schizophrenia participated in this study. They were administered the tests P50 and PPI. Moreover, three single nucleotide polymorphisms (SNPs) (rs2337980, rs1909884 and rs883473) in CHRNA7 and three SNPs (rs4680, rs737865 and rs165599) in COMT were selected to be genotyped by polyacrylamide gel microarray techniques. P50 index showed significant reduction in S2 amplitude between wild-type and mutation groups in the COMT rs4680. S1 amplitude of mutation group in the COMT rs737865 was also lower compared to wild-type group. PPI index revealed a shorter pulse latency of mutation group in the rs4680. The suppression ratio of mutation group was lower in COMT rs165599. Negative findings were shown between comparisons in all the CHRNA7 SNPs. We find that P50 and PPI may be influenced by COMT rs4680 polymorphisms in schizophrenia; more excitingly, we find that P50 might be influenced by COMT rs737865 polymorphisms and PPI may be influenced by COMT rs165599 polymorphisms in schizophrenia, and their mutations are associated with the reduction of the risk of P50 or PPI defects in schizophrenia. Futher studies with a larger number of subjects are needed to verify the present findings.

Brain mechanisms for prepulse inhibition in adults with Tourette syndrome: initial findings

Prepulse inhibition (PPI) of the startle reflex is disrupted in a number of developmental neuropsychiatric disorders, including Tourette syndrome (TS). This disruption is hypothesized to reflect abnormalities in sensorimotor gating. We applied whole-brain functional magnetic resonance imaging (fMRI) to elucidate the neural correlates of PPI in adult TS subjects using airpuff stimuli to the throat to elicit a tactile startle response. We used a cross-sectional, case-control study design and a blocked-design fMRI paradigm. There were 33 participants: 17 with TS and 16 healthy individuals. As a measure of PPI-related brain activity, we looked for differential cerebral activation to prepulse-plus-pulse stimuli versus activation to pulse-alone stimuli. In healthy subjects, PPI was associated with increased activity in multiple brain regions, of which activation in the left middle frontal gyrus in the healthy controls showed a significant linear correlation with the degree of PPI measured outside of the magnet. Group comparisons identified nine regions where brain activity during PPI differed significantly between TS and healthy subjects. Among the TS subjects, activation in the left caudate was significantly correlated with current tic severity as measured by the total score on the Yale Global Tic Severity Scale. Differential activation of the caudate nucleus associated with current tic severity is consistent with neuropathological data and suggests that portions of cortical-striatal circuits may modulate the severity of tic symptoms in adulthood.

Schizophrenia: a neurodevelopmental disorder--integrative genomic hypothesis and therapeutic implications from a transgenic mouse model

Schizophrenia is a neurodevelopmental disorder featuring complex aberrations in the structure, wiring, and chemistry of multiple neuronal systems. The abnormal developmental trajectory of the brain appears to be established during gestation, long before clinical symptoms of the disease appear in early adult life. Many genes are associated with schizophrenia, however, altered expression of no one gene has been shown to be present in a majority of schizophrenia patients. How does altered expression of such a variety of genes lead to the complex set of abnormalities observed in the schizophrenic brain? We hypothesize that the protein products of these genes converge on common neurodevelopmental pathways that affect the development of multiple neural circuits and neurotransmitter systems. One such neurodevelopmental pathway is Integrative Nuclear FGFR1 Signaling (INFS). INFS integrates diverse neurogenic signals that direct the postmitotic development of embryonic stem cells, neural progenitors and immature neurons, by direct gene reprogramming. Additionally, FGFR1 and its partner proteins link multiple upstream pathways in which schizophrenia-linked genes are known to function and interact directly with those genes. A th-fgfr1(tk-) transgenic mouse with impaired FGF receptor signaling establishes a number of important characteristics that mimic human schizophrenia - a neurodevelopmental origin, anatomical abnormalities at birth, a delayed onset of behavioral symptoms, deficits across multiple domains of the disorder and symptom improvement with typical and atypical antipsychotics, 5-HT antagonists, and nicotinic receptor agonists. Our research suggests that altered FGF receptor signaling plays a central role in the developmental abnormalities underlying schizophrenia and that nicotinic agonists are an effective class of compounds for the treatment of schizophrenia.

Structural brain correlates of sensorimotor gating in antipsychotic-naive men with first-episode schizophrenia

BACKGROUND

Prepulse inhibition (PPI) of the startle reflex is modulated by a complex neural network. Prepulse inhibition impairments are found at all stages of schizophrenia. Previous magnetic resonance imaging (MRI) studies suggest that brain correlates of PPI differ between patients with schizophrenia and healthy controls; however, these studies included only patients with chronic illness and medicated patients. Our aim was to examine the structural brain correlates of PPI in antipsychotic-naive patients with first-episode schizophrenia.

METHODS

We performed acoustic PPI assessment and structural MRI (1.5 and 3 T) in men with first-episode schizophrenia and age-matched controls. Voxel-based morphometry was used to investigate the association between PPI and grey matter volumes.

RESULTS

We included 27 patients and 38 controls in the study. Patients had lower PPI than controls. The brain areas in which PPI and grey matter volume correlated did not differ between the groups. Independent of group, PPI was significantly and positively associated with regional grey matter volume in the right superior parietal cortex. Prepulse inhibition and grey matter volume associations were also observed in the left rostral dorsal premotor cortex, the right presupplementary motor area and the anterior medial superior frontal gyrus bilaterally. Follow-up analyses suggested that the rostral dorsal premotor cortex and presupplementary motor area correlations were driven predominantly by the controls.

LIMITATIONS

We used 2 different MRI scanners, which might have limited our ability to find subcortical associations since interscanner consistency is low for subcortical regions.

CONCLUSION

The superior parietal cortex seems to be involved in the regulation of PPI in controls and antipsychotic-naive men with first-episode schizophrenia. Our observation that PPI deficits in schizophrenia may be related to the rostral dorsal premotor cortex and presupplementary motor area, brain areas involved in maintaining relevant sensory information and voluntary inhibition, warrants further study.

Nicotine effects on anterior cingulate cortex in schizophrenia and healthy smokers as revealed by EEG-informed fMRI

Nicotine can have beneficial effects on attention performance and corresponding brain function in both schizophrenia patients and healthy controls, but it remains controversial whether nicotine affects brain function differentially in patients vs. controls. The effects of nicotine on brain activity elicited by attention-requiring oddball-type tasks have not been studied in schizophrenia patients. In this study we sought to investigate the impact of nicotine on the p300 evoked potential component and corresponding fMRI (functional magnetic resonance imaging) activation measures in schizophrenia patients and controls. Applying a double-blind, placebo-controlled cross-over design, the effects of 1mg nasal nicotine on brain activity elicited by a visual oddball-type task in N=14 schizophrenia and N=15 control smokers were studied with simultaneous EEG-fMRI. EEG single trial amplitudes were used to inform the fMRI analysis. We found a nicotine-associated increase in P300-informed fMRI activation in schizophrenia patients and controls, mainly in the anterior cingulate and adjacent medial frontal cortex. No group differences in the response to nicotine were found. Remarkably, averaged EEG and fMRI activation measures considered in isolation were largely unaffected by nicotine. Taken together, the effects of nicotine on P300 amplitude-associated brain activation do not seem to be fundamentally different in schizophrenic smokers and healthy controls.

Effects of acute nicotine on auditory change-related cortical responses

RATIONALE AND OBJECTIVE

Nicotine is known to have enhancing effects on some aspects of attention and cognition. The purpose of the present study was to elucidate the effects of nicotine on pre-attentive change-related cortical activity.

METHODS

Change-related cortical activity in response to an abrupt increase (3 dB) and decrease (6 dB) in sound pressure in a continuous sound was recorded by using magnetoencephalography. Nicotine was administered with a nicotine gum (4 mg of nicotine). Eleven healthy nonsmokers were tested with a double-blind and placebo-controlled design. Effects of nicotine on the main component of the onset response peaking at around 50 ms (P50m) and the main component of the change-related response at around 120 ms (Change-N1m) were investigated.

RESULTS

Nicotine failed to affect P50m, while it significantly increased the amplitude of Change-N1m evoked by both auditory changes. The magnitude of the amplitude increase was similar among subjects regardless of the magnitude of the baseline response, which resulted in the percent increase of Change-N1m being greater for subjects with Change-N1m of smaller amplitude.

CONCLUSIONS

Since Change-N1m represents a pre-attentive automatic process to encode new auditory events, the present results suggest that nicotine can exert beneficial cognitive effects without a direct impact on attention.

Nicotine fails to attenuate ketamine-induced cognitive deficits and negative and positive symptoms in humans: implications for schizophrenia

BACKGROUND

The uncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist, ketamine, induces a range of symptoms resembling those seen in schizophrenia. Enhancement of nicotinic acetylcholine receptor (nAChR) function may have potential as a treatment for the cognitive deficits and negative symptoms of schizophrenia. Accordingly, we examined the modulatory effects of brain nAChR systems on NMDAR antagonist-induced effects.

METHODS

The interactive effects of ketamine and nicotine were evaluated in 37 healthy subjects in a randomized, placebo-controlled, double-blind, crossover counterbalanced, 2 (intravenous ketamine or placebo) × 2 (intravenous nicotine or placebo) design. Verbal and visual memory, sustained attention, working memory, response inhibition, emotion recognition, executive function, reaction time, motor function, and speed of processing were assessed once per test day, while negative and positive symptoms, perceptual alterations, and a number of feeling states were measured several times before and after administration of drugs.

RESULTS

Ketamine induced cognitive deficits and negative and positive symptoms. Nicotine worsened immediate recall, auditory working memory, response inhibition, and executive function and serial processing. Nicotine decreased (improved) reaction time on the sustained attention and choice reaction time tasks. Nicotine did not reduce ketamine-induced cognitive deficits or negative and positive symptoms.

CONCLUSIONS

At blood levels comparable with tobacco smoking, nicotine infusion does not appear to alleviate the ketamine-induced transient cognitive and behavioral effects in healthy subjects that resemble those seen in schizophrenia. The lack of an effect of nicotine on a spectrum of ketamine effects suggests that the consequences of NMDAR antagonism are not likely under the direct influence of nAChR.

Perceptual measurement in schizophrenia: promising electrophysiology and neuroimaging paradigms from CNTRICS

The sixth meeting of the Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) focused on selecting promising imaging paradigms for each of the cognitive constructs selected in the first CNTRICS meeting. In the domain of perception, the 2 constructs of interest were "gain control" and "visual integration." CNTRICS received 6 task nominations for imaging paradigms for gain control and 3 task nominations for integration. The breakout group for perception evaluated the degree to which each of these tasks met prespecified criteria. For gain control, the breakout group believed that one task (mismatch negativity) was already mature and was being incorporated into multisite clinical trials. The breakout group recommended that 1 visual task (steady-state visual evoked potentials to magnocellular- vs parvocellular-biased stimuli) and 2 auditory measures (an event-related potential (ERP) measure of corollary discharge and a functional magnetic resonance imaging (fMRI) version of prepulse inhibition of startle) be adapted for use in clinical trials in schizophrenia research. For visual integration, the breakout group recommended that fMRI and ERP versions of a contour integration test and an fMRI version of a coherent motion test be adapted for use in clinical trials. This manuscript describes the ways in which each of these tasks met the criteria used in the breakout group to evaluate and recommend tasks for further development.

Nicotinic mechanisms in the treatment of psychotic disorders: a focus on the α7 nicotinic receptor

Nicotine is heavily abused by persons with schizophrenia. Nicotine better enables people with schizophrenia to filter out extraneous auditory stimuli. Nicotine also improves prepulse inhibition when compared to placebo. Nicotine similarly increases the amplitude of patients' duration mismatch negativity. The 15q13-14 region of the genome coding for the α7 nicotinic receptor is linked to schizophrenia. Multiple single nucleotide polymorphisms have been identified in this 15q13-14 gene promoter region that are more frequently present in people with schizophrenia than in normal controls. Abnormalities in expression and regulation of central nicotinic cholinoceptors with decreased α7 binding in multiple brain regions are also present. Nicotine enhances cognition in schizophrenia. Alternative agents that activate the nicotinic receptor have been tested including 3-[2,4-dimethoxybenzylidene]anabaseine (DMXB-A). This compound improved attention, working memory, and negative symptoms in an add-on study in nonsmoking patients with schizophrenia. There are multiple other nicotinic agents, including positive allosteric modulators, in the preclinical stages of development. Finally, the effects of varenicline and clozapine and their relation to smoking cessation are discussed.

Stability of prepulse inhibition and habituation of the startle reflex in schizophrenia: a 6-year follow-up study of initially antipsychotic-naive, first-episode schizophrenia patients

Deficits in information processing appear to be core features in the pathogenesis of schizophrenia. Prepulse inhibition (PPI) and habituation of the startle reflex are operational measures of early information processing. Impaired PPI in schizophrenia has been replicated in many studies and is regarded as an endophenotype for schizophrenia. However, reports on the stability of PPI over a longer period of time are lacking, both for patients with schizophrenia and for healthy subjects. The current study examined 25 initially drug-naive, first-episode schizophrenia patients and 23 healthy matched controls. Three PPI measures [stimulus onset asynchrony (SOA) 30, 60, 120 ms] and habituation were assessed at baseline, and again after 6 yr. Sixteen patients and 17 healthy controls completed the study, and 13 patients and 17 healthy controls were included in the final analysis. The schizophrenia patients had PPI deficits compared to controls at baseline. After 6 yr, no significant group differences were found. PPI had increased significantly in the patients and had decreased significantly in controls. In addition, patients showed significantly less habituation than controls while habituation did not change in patients or controls. The present results show that PPI in drug-naive, first-episode schizophrenia patients can improve significantly over time. As PPI increased in patients over the same period that it decreased in controls, it is likely that the increase was caused by disease-related factors such as disease process, clinical state, or medication.

The association of schizophrenia risk D-amino acid oxidase polymorphisms with sensorimotor gating, working memory and personality in healthy males

There is evidence supporting a role for the D-amino acid oxidase (DAO) locus in schizophrenia. This study aimed to determine the relationship of five single-nucleotide polymorphisms (SNPs) within the DAO gene identified as promising schizophrenia risk genes (rs4623951, rs2111902, rs3918346, rs3741775, and rs3825251) to acoustic startle, prepulse inhibition (PPI), working memory, and personality dimensions. A highly homogeneous study entry cohort (n = 530) of healthy, young male army conscripts (n = 703) originating from the Greek LOGOS project (Learning On Genetics Of Schizophrenia Spectrum) underwent PPI of the acoustic startle reflex, working memory, and personality assessment. The QTPHASE from the UNPHASED package was used for the association analysis of each SNP or haplotype data, with p-values corrected for multiple testing by running 10,000 permutations of the data. The rs4623951_T-rs3741775_G and rs4623951_T-rs2111902_T diplotypes were associated with reduced PPI and worse performance in working memory tasks and a personality pattern characterized by attenuated anxiety. Median stratification analysis of the risk diplotype group (ie, those individuals homozygous for the T and G alleles (TG+)) showed reduced PPI and working memory performance only in TG+ individuals with high trait anxiety. The rs4623951_T allele, which is the DAO polymorphism most strongly associated with schizophrenia, might tag a haplotype that affects PPI, cognition, and personality traits in general population. Our findings suggest an influence of the gene in the neural substrate mediating sensorimotor gating and working memory, especially when combined with high anxiety and further validate DAO as a candidate gene for schizophrenia and spectrum disorders.

Cholinergic modulation of cognition: insights from human pharmacological functional neuroimaging

Evidence from lesion and cortical-slice studies implicate the neocortical cholinergic system in the modulation of sensory, attentional and memory processing. In this review we consider findings from sixty-three healthy human cholinergic functional neuroimaging studies that probe interactions of cholinergic drugs with brain activation profiles, and relate these to contemporary neurobiological models. Consistent patterns that emerge are: (1) the direction of cholinergic modulation of sensory cortex activations depends upon top-down influences; (2) cholinergic hyperstimulation reduces top-down selective modulation of sensory cortices; (3) cholinergic hyperstimulation interacts with task-specific frontoparietal activations according to one of several patterns, including: suppression of parietal-mediated reorienting; decreasing ‘effort’-associated activations in prefrontal regions; and deactivation of a ‘resting-state network’ in medial cortex, with reciprocal recruitment of dorsolateral frontoparietal regions during performance-challenging conditions; (4) encoding-related activations in both neocortical and hippocampal regions are disrupted by cholinergic blockade, or enhanced with cholinergic stimulation, while the opposite profile is observed during retrieval; (5) many examples exist of an ‘inverted-U shaped’ pattern of cholinergic influences by which the direction of functional neural activation (and performance) depends upon both task (e.g. relative difficulty) and subject (e.g. age) factors. Overall, human cholinergic functional neuroimaging studies both corroborate and extend physiological accounts of cholinergic function arising from other experimental contexts, while providing mechanistic insights into cholinergic-acting drugs and their potential clinical applications.

Reduced prepulse inhibition in adolescents at risk for psychosis: a 2-year follow-up study

BACKGROUND

Reduced prepulse inhibition (PPI) of the auditory startle reflex is a hallmark feature of attention-processing deficits in patients with schizophrenia and other psychotic disorders. Recent evidence suggests that these deficits may also be present before the onset of psychosis in individuals at ultra-high risk (UHR) and become progressively worse as psychosis develops. We conducted a longitudinal follow-up study to observe the development of PPI over time in UHR adolescents and healthy controls.

METHODS

Two-year follow-up data of PPI measures were compared between UHR adolescents and a matched control group of typically developing individuals.

RESULTS

We included 42 UHR adolescents and 32 matched controls in our study. Compared with controls, UHR individuals showed reduced PPI at both assessments. Clinical improvement in UHR individuals was associated with an increase in PPI parameters.

LIMITATIONS

A developmental increase in startle magnitude partially confined the interpretation of the association between clinical status and PPI. Furthermore, post hoc analyses for UHR individuals who became psychotic between assessments had limited power owing to a low transition rate (14%).

CONCLUSION

Deficits in PPI are present before the onset of psychosis and represent a stable vulnerability marker over time in UHR individuals. The magnitude of this marker may partially depend on the severity of clinical symptoms.

Sex differences and hormonal influences in human sensorimotor gating: implications for schizophrenia

Prepulse inhibition (PPI) of the startle response serves to prevent the interruption of ongoing perceptual and early sensory analysis and provides a simple operational measure of sensorimotor gating. In line with postulated deficits in early stages of information processing, PPI is disrupted in schizophrenia. PPI is considered a valid candidate for an endophenotypic marker in genetic studies of schizophrenia and has also been extensively used in translational research. Importantly, there are well-replicated sex differences and menstrual phase effects in prepulse-elicited startle modulation of nonclinical young populations. Lack of knowledge about the precise roles of sex differences and hormonal effects in prepulse-elicited startle modulation and in the schizophrenia disease process presents a stumbling block to continuous progress in this field. This chapter reviews a wealth of data demonstrating sex and hormonal influences in prepulse-elicited startle modulation and considers their implications for our understanding of the pathophysiology, genetics, and potential treatments of schizophrenia.

No association between prepulse inhibition of the startle reflex and neuropsychological deficit in chronic schizophrenia

Sensorimotor gating deficits are relevant in schizophrenia and can be measured using prepulse inhibition (PPI) of the startle reflex. It is conceivable that such deficits may hinder the cognitive functions in schizophrenia patients. In this study, using PPI and a neuropsychological battery, we studied this possibility in a group of 23 acute, neuroleptic-free schizophrenia patients and 16 controls. A non-significant decrease in PPI was found in the patients as compared to the controls, as well as significant differences in the performance of Trail A and B in Wisconsin Card Sorting and Digit/Symbol Tests. No statistically significant correlations between PPI and neuropsychological performance were found after the correction for multiple comparisons in any group. Our results suggest that PPI deficits in schizophrenia patients may not contribute to the cognitive deficits typical of that illness, at least in patients with a non-significant PPI decrease.

The role of the insula in schizophrenia

Involvement of the insular cortex is a common finding in neuroanatomical studies of schizophrenia, yet its contribution to disease pathology remains unknown. This review describes the normal function of the insula and examines pathology of this region in schizophrenia. The insula is a cortical structure with extensive connections to many areas of the cortex and limbic system. It integrates external sensory input with the limbic system and is integral to the awareness of the body's state (interoception). Many deficits observed in schizophrenia involve these functions and may relate to insula pathology. Furthermore, reports describing deficits caused by lesions of the insula parallel deficits observed in schizophrenia. Examples of insula-related functions that are altered in schizophrenia include the processing of both visual and auditory emotional information, pain, and neuronal representations of the self. The last of these functions, processing representations of the self, plays a key role in discriminating between self-generated and external information, suggesting that insula dysfunction may contribute to hallucinations, a cardinal feature of schizophrenia.

Prepulse inhibition of the startle reflex in schizophrenia remains stable with short-term quetiapine

PURPOSE

To study the short-term effect of treatment with quetiapine on prepulse inhibition (PPI) deficits of the startle reflex in schizophrenia patients.

SUBJECTS AND METHODS

Using PPI, we studied a group of 21 schizophrenia patients and 16 controls. Seventeen of the patients were re-tested with PPI after 21 days of treatment with quetiapine.

RESULTS

At baseline, an almost significant decrease in PPI was found in the patients as compared to the controls. PPI measurements did not change in the patients after 21 days of treatment with quetiapine, despite their clinical improvement.

CONCLUSION

Our results suggest that short-term quetiapine treatment may not modify PPI measures in schizophrenia patients.

Sensorimotor gating is associated with CHRNA3 polymorphisms in schizophrenia and healthy volunteers

Attentional gating deficits, commonly measured by prepulse inhibition (PPI) of the acoustic startle response (ASR), have been established as an endophenotype of schizophrenia. Prepulse inhibition is heritable and has been associated with polymorphisms in serotonin and dopamine system genes. Prepulse inhibition can be enhanced by nicotine, and therefore it has been proposed that schizophrenia patients smoke to ameliorate their early attentional deficits. The PPI-enhancing effects of nicotine in rodents are strain dependent, suggesting a genetic contribution to PPI within the nicotinic acetylcholine receptor (nAChR) system. Recent human genetic studies also imply that tobacco dependence is affected by polymorphisms in the alpha3/alpha5 subunits of the nAChR (CHRNA3/CHRNA5) gene cluster. We, therefore, investigated the impact of two common CHRNA3 polymorphisms (rs1051730/rs1317286) on PPI, startle reactivity, and habituation of the ASR in two independent samples of 107 healthy British volunteers and 73 schizophrenia patients hailing from Germany. In both samples, PPI was influenced by both CHRNA3 polymorphisms (combined p-value=0.0027), which were strongly linked. Moreover, CHRNA3 genotype was associated with chronicity, treatment, and negative symptoms in the schizophrenia sample. These results suggest that sensorimotor gating is influenced by variations of the CHRNA3 gene, which might also have an impact on the course and severity of schizophrenia.

[Predictors of smoking cessation after stroke]

Cigarette smoking is a major modifiable risk factor for stroke. Smoking dose dependently increases the risk of stroke, especially in patients below 75 years of age. Although smoking cessation is considered as one of the most effective methods of secondary stroke prevention, little is known about nicotine dependence and predictors of smoking cessation after stroke. Identification of such predictors could facilitate the development of anti-smoking interventions in post-stroke patients. Results of previous studies showed that smoking cessation is determined by the interplay of multiple factors, including sociodemographic (gender, age, race, living conditions, employment), clinical (functional status), psychobiological (nicotine dependence, depressed mood) and environmental (smoking household members) factors. Limitations of most studies were relatively small sample sizes and lack of verification of smoking status with a biochemical marker (e.g. expired CO). The aim of this article is to summarize current knowledge about predictors of smoking cessation after stroke.

Tolcapone effects on gating, working memory, and mood interact with the synonymous catechol-O-methyltransferase rs4818c/g polymorphism

BACKGROUND

The functional catechol-O-methyltransferase (COMT) valine158methionine (val158met) polymorphism determines prepulse inhibition (PPI) levels and working memory performance and the effects of tolcapone on these functions. Here, we explored the effects of the synonymous COMT rs4818 C/G polymorphism and tolcapone on PPI and working memory.

METHODS

Thirteen G/G (low prefrontal cortex [PFC] dopamine [DA]) and 12 C/C (high PFC DA) healthy male subjects entered and completed the study. Subjects participated in two weekly sessions associated with either acute oral tolcapone (200 mg) or placebo according to a balanced, crossover, double-blind design. Prepulse inhibition was assessed with 5 dB and 15 dB above background prepulses at 30-msec, 60-msec, and 120-msec intervals. Subjective mood and working memory performance (n-back and letter-number sequencing) were also assessed.

RESULTS

Prepulse inhibition was lower and reaction time in the n-back was slower in the G/G compared with the C/C group in the placebo condition. Tolcapone increased PPI and improved performance in both working memory tasks in the G/G group only. Baseline startle was greater in the C/C group and was not affected by tolcapone. Mood profile was worse in the C/C group and tended to deteriorate with tolcapone. Status of val158met alone could not explain these results.

CONCLUSIONS

Catechol-O-methyltransferase haplotype analyses are essential in future research. Prepulse inhibition and working memory may both relate to PFC DA levels according to an inverted U-shaped curve function. Tolcapone could be potentially useful in the treatment of conditions with deficient sensorimotor gating and working memory such as schizophrenia and prodromal states but only in a genotype-specific manner.