Regional cerebral blood flow in male schizophrenic patients performing an auditory discrimination task

Basic auditory processing and its relationship with symptoms in patients with schizophrenia: A systematic review

Processing of basic auditory features, one of the earliest stages of auditory perception, has been the focus of considerable investigations in schizophrenia. Although numerous studies have shown abnormalities in pitch perception in schizophrenia, other basic auditory features such as intensity, duration, and sound localization have been less explored. Additionally, the relationship between basic auditory features and symptom severity shows inconsistent results, preventing concrete conclusions. Our aim was to present a comprehensive overview of basic auditory processing in schizophrenia and its relationship with symptoms. We conducted a systematic review according to the PRISMA guidelines. PubMed, Embase, and PsycINFO databases were searched for studies exploring auditory perception in schizophrenia compared to controls, with at least one behavioral task investigating basic auditory processing using pure tones. Forty-one studies were included. The majority investigated pitch processing while the others investigated intensity, duration and sound localization. The results revealed that patients have a significant deficit in the processing of all basic auditory features. Although the search for a relationship with symptoms was limited, auditory hallucinations experience appears to have an impact on basic auditory processing. Further research may examine correlations with clinical symptoms to explore the performance of patient subgroups and possibly implement remediation strategies.

[Evoked potentials N200/P300 disorders and clinical phenotype in Cuban families with paranoid schizophrenia: a family-based association study]

INTRODUCTION

N200 and P300 event-related evoked potentials provide sensitive measurements of sensory and cognitive function and have been used to study information processing in patients with schizophrenia and their unaffected first-degree relatives. Reduced amplitude and increased latency of N200 and P300 potentials have been consistently reported in schizophrenia. Thus, event-related evoked potentials abnormalities are promising possible biological markers for genetic vulnerability to schizophrenia.

OBJECTIVE

To assess the association of changes in latency, amplitude and topographic distribution of potentials N200 and P300 of patients with paranoid schizophrenia and their healthy first-degree relatives, in families with schizophrenia multiplex.

METHODOLOGY

We measured latency and amplitude of the N200 and P300 component of evoked potentials using an auditory odd-ball paradigm in 25 schizophrenic patients (probands) from 60 families multiply affected with paranoid schizophrenia, 23 of their non-schizophrenic first-degree relatives and 25 unrelated healthy controls, through a study of family association.

RESULTS

Schizophrenic patients and their relatives showed significant latency prolongation and amplitude reduction of the N200 and P300 waves compared to controls. Left-temporal as compared to right-temporal N200 and P300 were significantly smaller in schizophrenic patients and their non-schizophrenic first-degree relatives than in controls. Our results suggest that event-related evoked potentials abnormalities may serve as markers of genetic vulnerability in schizophrenia.

CONCLUSIONS

Confirming results of other researchers, this present study suggests that latency prolongation and amplitude reduction of the N200 and P300 waves and an altered topography at temporal sites may be a trait “marker” of paranoid schizophrenia.

Schizophrenia and periodontal disease: An oro-neural connection? A cross-sectional epidemiological study

Background:

Schizophrenia is a psychosis characterized by delusions and hallucinations occurring in clear consciousness. Studies have shown that the cytokines may modulate dopaminergic metabolism and schizophrenic symptomatology in schizophrenia. Cytokine involvement in periodontal disease is also well documented. To date, however, there has been relatively little research assessing periodontal status of patients with schizophrenia. The present study was therefore mainly intended to understand the exact link, if any, between periodontal disease and schizophrenia.

Materials and Methods:

A total of 250 schizophrenic patients (140 males and 110 females), between 25 and 55 years of age, were selected from the out patient department of National Institute of Mental Health and Neural Sciences, Bangalore and their periodontal status was assessed as part of this cross-sectional epidemiological survey.

Results:

ANOVA showed that there was increased evidence of poor periodontal condition, as evidenced by gingival index and plaque index in patients who had been schizophrenic for a longer duration of time (P < 0.001). So also, higher probing pocket depths were found in schizophrenics suffering from a longer period of time than others (P < 0.001).

Conclusions:

Although oral neglect might be a cause of poor periodontal health in schizophrenics, the possible link between periodontal diseases giving rise to schizophrenia cannot be overlooked due to the presence of cytokine activity which is present both in schizophrenia and periodontal disease.

From sensorimotor inhibition to freudian repression: insights from psychosis applied to neurosis

First, three case studies are presented of psychotic patients having in common an inability to hold something down or out. In line with other theories on psychosis, we propose that a key change is at the efference copy system. Going back to Freud's mental apparatus, we propose that the messages of discharge of the motor neurons, mobilized to direct perception, also called "indications of reality," are equivalent to the modern efference copies. With this key, the reading of the cases is coherent with the psychodynamic understanding of psychosis, being a downplay of secondary processes, and consequently, a dominance of primary processes. Moreover, putting together the sensorimotor idea of a failure of efference copy-mediated inhibition with the psychoanalytic idea of a failing repression in psychosis, the hypothesis emerges that the attenuation enabled by the efference copy dynamics is, in some instances, the physiological instantiation of repression. Second, we applied this idea to the mental organization in neurosis. Indeed, the efference copy-mediated attenuation is thought to be the mechanism through which sustained activation of an intention, without reaching it - i.e., inhibition of an action - gives rise to mental imagery. Therefore, as inhibition is needed for any targeted action or for normal language understanding, acting in the world, or processing language, structurally induces mental imagery, constituting a subjective unconscious mental reality. Repression is a special instance of inhibition for emotionally threatening stimuli. These stimuli require stronger inhibition, leaving (the attenuation of) the motor intentions totally unanswered, in order to radically prevent execution which would lead to development of excess affect. This inhibition, then, yields a specific type of motor imagery, called "phantoms," which induce mental preoccupation, as well as symptoms which, especially through their form, refer to the repressed motor fragments.

Assessment of cerebral blood volume in schizophrenia: A magnetic resonance imaging study

Brain atrophy has consistently been observed in schizophrenia, representing a 'gross' evidence of anatomical abnormalities. Reduced cerebral blood volume (CBV) may accompany brain size decrement in schizophrenia, as suggested by prior small SPECT studies. In this study, we non-invasively investigated the hemisphere CBV in a large sample of patients suffering from schizophrenia with perfusion-weighted imaging (PWI). PWI images were obtained, following intravenous injection of paramagnetic contrast agent (Gadolinium-DTPA), for 54 DSM-IV patients with schizophrenia (mean age+/-SD=39.19+/-12.20 years; 34 males, 20 females) and 24 normal controls (mean age+/-SD=44.63+/-10.43 years; 9 males, 15 females) with a 1.5T Siemens magnet using an echo-planar sequence (TR=2160 ms, TE=47 ms, slice thickness=5mm). The contrast of enhancement (CE), a semi-quantitative parameter inversely estimating the CBV, were calculated pixel by pixel as the ratio of the maximum signal intensity drop during the passage of contrast agent (Sm) by the baseline pre-bolus signal intensity (So) (CE=Sm/Sox100) for right and left hemisphere on two axial images. Specifically, higher CE values correspond to lower CBV and viceversa Compared to normal controls, patients with schizophrenia had significantly higher bilateral hemisphere CE values (p=0.02) and inverse CE laterality index (p=0.02). This study showed abnormally reduced and inverse hemisphere CBV in a large population of patients with schizophrenia. Hypothetically, chronic low CBV may sustain neural hypoactivation and concomitant increase of free radicals, ultimately resulting in neuronal loss and cognitive impairments. Thus, altered intracranial hemodynamics may accompany brain atrophy and cognitive deficits, being a crucial factor in the pathophysiology of schizophrenia.

Voxel-based analysis of P300 electrophysiological topography associated with positive and negative symptoms of schizophrenia

Abnormal P300 waveforms of the event-related potentials during the auditory oddball task are one of the most consistent findings in patients with schizophrenia. In the present study, we sought to test the hypothesis that the abnormal P300 waveform results from composite representation of neural activity in anatomically distinct brain regions responsible for the manifestation of positive and negative symptoms. We used the low-resolution brain electromagnetic tomography (LORETA) to obtain current density images of the P300 component from 26 patients with schizophrenia. The statistical parametric mapping (SPM) was applied to the LORETA images in order to identify brain regions that are related with the severity of psychotic symptoms as evaluated by the Brief Psychiatric Rating Scale (BPRS). The BPRS Total score was negatively correlated with the P300 current density in the left superior temporal gyrus (r=-0.615, corrected p=0.009) and that in the right medial frontal region (r=-0.571, corrected p=0.019) by means of SPM single-subject covariates model. These brain regions were included in the region-specific P300 sources as represented by the current density maxima (corrected p<0.05) using SPM one-sample t-test. A subsequent region-of-interest analysis of Pearson correlations revealed specific relationships between the Positive subscale score and the mean current density in the left superior temporal gyrus (r=-0.528, p=0.005) and between the Negative subscale score and the mean current densities in the medial frontal region (r=-0.551, p=0.003) and left superior temporal gyrus (r=-0.499, p=0.009). These results indicate that functional disturbances of neural networks involving the medial prefrontal and superior temporal regions may be responsible for the generation of positive and the negative psychotic symptoms of schizophrenia.

Beneficial effect of atypical antipsychotics on prefrontal brain function in acute psychotic disorders

Disturbance of prefrontal brain functions is assumed to be responsible for prominent psychopathological symptoms in psychotic disorders. Treatment with atypical, in contrast to typical antipsychotics is considered as a possible strategy for an improvement of prefrontal brain function. In the present study, response control as a specific prefrontal brain function was assessed by means of the Nogo-anteriorization (NGA) derived from the event-related potentials elicited during a Go-NoGo task in a consecutive sample of 39 patients suffering from acute psychotic disorders (brief psychotic disorders, 298.8, n = 34 and schizoaffective disorders, 295.70, n = 5; cycloid psychoses according to the Leonhard classification). A highly significant positive correlation between the amount of antipsychotic medication in terms of chlorpromazine equivalents per day and the NGA as a measure of prefrontal response control was only found in the subgroup of patients treated exclusively or predominantly with atypical antipsychotics but not for those treated with typical antipsychotics. These results are in line with the notion that atypical antipsychotics may exert a beneficial effect on prefrontal brain function.

Neuropsychological correlates of an attention-related negative component elicited in an auditory oddball paradigm in schizophrenia

An attention-related, negative component can be detected between the N100 peak and 200 ms after stimulus by subtracting event-related potentials (ERPs) elicited to background tones when subjects ignore tones, from ERPs elicited to background tones when subjects attend to tones to detect target tones in an oddball paradigm. To clarify the cognitive significance of this component in schizophrenia, we examined the correlations of 24 patients between the amplitude and latency of the negative component and results obtained using neuropsychological measurement methods, including the Wisconsin Card Sorting Test, the Trail Making Test, the Verbal Fluency Test and some subtests from the Wechsler Memory Scale. The latency prolongation of the negative component correlated positively with the difference in performance time between parts A and B of the Trail Making Test, which estimates set shift, a frontal-lobe executive function, but not with any other neuropsychological measurements, while the amplitude showed no such correlation. These results suggest that the latency prolongation of the attention-related, negative component induced in an auditory oddball paradigm may serve as an index for frontal dysfunction in schizophrenia.

Hypofrontality in schizophrenia: a meta-analysis of functional imaging studies

OBJECTIVE

Hypofrontality is not a well-replicated finding in schizophrenia either at rest or under conditions of task activation.

METHOD

Studies comparing whole brain and frontal blood flow/metabolism in schizophrenic patients and normal controls were pooled. Voxel-based studies were also combined to examine the pattern of prefrontal activation in schizophrenia.

RESULTS

Whole brain flow/metabolism was reduced in schizophrenia to only a small extent. Resting and activation frontal flow/metabolism were both reduced with a medium effect size. Duration of illness significantly moderated resting hypofrontality, but the moderating effects of neuroleptic treatment were consistent with an influence on global flow/metabolism only. Pooling of voxel-based studies did not suggest an abnormal pattern of activation in schizophrenia.

CONCLUSION

Meta-analysis supports resting hypofrontality in schizophrenia. Task-activated hypofrontality is also supported, but there is little from voxel-based studies to suggest that this is associated with an altered pattern of regional functional architecture.

LORETA imaging of P300 in schizophrenia with individual MRI and 128-channel EEG

We investigated the characteristics of P300 generators in schizophrenics by using voxel-based statistical parametric mapping of current density images. P300 generators, produced by a rare target tone of 1500 Hz (15%) under a frequent nontarget tone of 1000 Hz (85%), were measured in 20 right-handed schizophrenics and 21 controls. Low-resolution electromagnetic tomography (LORETA), using a realistic head model of the boundary element method based on individual MRI, was applied to the 128-channel EEG. Three-dimensional current density images were reconstructed from the LORETA intensity maps that covered the whole cortical gray matter. Spatial normalization and intensity normalization of the smoothed current density images were used to reduce anatomical variance and subject-specific global activity and statistical parametric mapping (SPM) was applied for the statistical analysis. We found that the sources of P300 were consistently localized at the left superior parietal area in normal subjects, while those of schizophrenics were diversely distributed. Upon statistical comparison, schizophrenics, with globally reduced current densities, showed a significant P300 current density reduction in the left medial temporal area and in the left inferior parietal area, while both left prefrontal and right orbitofrontal areas were relatively activated. The left parietotemporal area was found to correlate negatively with Positive and Negative Syndrome Scale total scores of schizophrenic patients. In conclusion, the reduced and increased areas of current density in schizophrenic patients suggest that the medial temporal and frontal areas contribute to the pathophysiology of schizophrenia, the frontotemporal circuitry abnormality.

Functional neuroanatomy of sustained attention in schizophrenia: contribution of parietal cortices

Deficits in sustained attention have been frequently described in schizophrenia. The neuroanatomical basis reported previously have included altered levels of activation in cingulate and prefrontal cortex, but the contribution of further regions remains unclear. We explored the full neuroanatomy underlying the sustained attentional deficits observed in naïve schizophrenics compared with controls. Participants included 10 controls and 11 patients. The experimental design included rest, auditory stimulation using clicks, and two counting tasks. Subjects were instructed to mentally count the clicks, and then to count forward at the same frequency they heard previously when listening to the clicks. Relative cerebral blood flow (relCBF) was measured by means of PET (15)O-water. Differences were observed between both groups at superior temporal cortex, superior parietal gyrus, and cerebellum during tasks requiring listening. During all counting conditions, additionally to supplementary motor area (SMA), dorsolateral prefrontal cortex (DLPCF), precentral gyrus, cingulate, cerebellum, and inferior parietal (IP) gyrus, patients engaged other frontal structures including inferior, medial, and superior frontal areas. When counting with no auditory stimulation (C; requires components of working memory and time estimation), significant differences were observed in the level of activation of frontal and IP regions. Our naïve patients presented abnormal activation of auditory associative pathways. They failed to activate prefrontal and parietal regions at a similar level during tasks requiring increased cognitive effort, and they required a higher activation of inferior frontal regions to properly respond to cognitive demands.

N2 and P3 components of event-related potential in first-episode schizophrenic patients: scalp topography, medication, and latency effects

Auditory N2 and P3 components of event-related potentials were assessed in first-episode schizophrenic and normal control subjects (n=12/group). P3 amplitude was decreased in the patients most prominently over the frontal areas in contrast to a widespread P3 amplitude decrease reported in chronic schizophrenia. Moreover, frontal attenuation of P3 amplitude was greater in the non-medicated compared with medicated patients, a finding that suggests frontal areas are primarily affected at the onset of the first schizophrenic episode. Prolongation of N2 and P3 latencies was also observed in the patients, which indicates that stimulus classification and memory updating processes were slowed even in early stages of schizophrenia. These findings indicate that first-episode schizophrenic patients produce N2 and P3 abnormalities that are distinct from those in chronic patients, and that psychotropic medication can attenuate event-related potential effects in specific ways.

The psychopathology, medical management and dental implications of schizophrenia

BACKGROUND

Schizophrenia is a psychiatric illness characterized by thought disturbances, bizarre behaviors and cognitive impairments that may diminish a person's abilities in the areas of social relations, school or work and self-care. The onset of the disorder typically occurs between the late teens and mid-30s. Advanced dental disease is seen frequently in patients with schizophrenia for several reasons: the disease impairs these patients' ability to plan and perform oral hygiene procedures; some of the antipsychotic medications they take have adverse orofacial effects such as xerostomia; and these patients sometimes have limited access to treatment because of a paucity of financial resources and adequate number of dentists comfortable in providing care. The recent introduction of more effective medications has permitted the majority of patients to receive their psychiatric care from community-based providers rather than in the hospital. Consequently, dentists in the private sector also are being called on more frequently to care for these people.

CONCLUSIONS

Dentists cognizant of the signs and symptoms of schizophrenia are likely to feel more secure in treating patients with schizophrenia and more confident when obtaining consultative advice from the patients' psychiatrists. Dentists usually can provide a full range of services to such patients, can enhance these patients' self-esteem and can contribute to the psychotherapeutic aspect of management.

CLINICAL IMPLICATIONS

To effectively provide treatment to patients with schizophrenia, dentists must be familiar with the disease process so that they can communicate effectively with the patient, the treating psychiatrist and family members who serve as caregivers. In addition, dental treatment may need to be modified because of the patient's impaired ability to think logically, the local and systemic effects of psychiatric medications, and adverse interactions between these drugs and medications used in dentistry.