Core of sensory gating deficits in first-episode schizophrenia: attention dysfunction

Background

Sensory gating deficits are a common feature of schizophrenia and may be indicative of higher-order psychopathological impairments. It has been proposed that incorporating subjective attention components into prepulse inhibition (PPI) measures may improve the accuracy of assessing these deficits. This study aimed to investigate the relationship between modified PPI and cognitive function, with a specific focus on subjective attention, to gain a better understanding of the underlying mechanisms of sensory processing deficits in schizophrenia.

Methods

Fifty-four unmedicated first-episode schizophrenia (UMFE) patients and 53 healthy controls participated in this study. The modified Prepulse Inhibition paradigm, including Perceived Spatial Separation PPI (PSSPPI) and Perceived Spatial Colocation PPI (PSCPPI), was used to evaluate sensorimotor gating deficits. Cognitive function was assessed in all participants using the Chinese version of the MATRICS Consensus Cognitive Suite Test (MCCB).

Results

UMFE patients had lower MCCB scores and deficient PSSPPI scores than healthy controls. PSSPPI was negatively correlated with total PANSS scores and positively correlated with the speed of processing, attention/ vigilance, and social cognition. Multiple linear regression analysis showed that the PSSPPI at 60 ms had a significant effect on attentional/ vigilance and social cognition, even after controlling for gender, age, years of education, and smoking.

Conclusion

The study revealed notable impairments in sensory gating and cognitive function in UMFE patients, best reflected by the PSSPPI measure. Specifically, PSSPPI at 60 ms was significantly associated with both clinical symptoms and cognitive performance, suggesting that PSSPPI at 60 ms may capture psychopathological symptoms related to psychosis.

Circuit activity underlying a distinct modulator of prepulse inhibition

Prepulse inhibition (PPI), the diminished eye blink response to a startling pulse induced by a prepulse, is regulated by brainstem, and modulated by cerebral, processes. Attentional modulation by the prepulse (AMP), a potential biomarker of psychotic disorders, differs from other modulatory processes because it only occurs if the interval between the prepulse and pulse exceeds 100 ms (>PP100). Videotaped eye blinks were measured during fMRI scanning in 15 healthy subjects hearing 64 pulse alone, 64 PP60 and 64 PP120 trials in a rapid event-related design. Because attentional influences on PPI vary spontaneously, we posited AMP could be isolated by comparing eye blink and Blood Oxygen Level Dependent covariation during the two PP trial types. Behavioral regressor coefficients reflecting significant covariation covered the insula and auditory cortices during PP120 but not PP60 trials. Clusters within the right anterior insula and auditory cortex were specific to AMP. Functional connections (FCs) between cerebral ROIs implicated in PPI were stronger during PP120 trials. The four FCs that were individually stronger during PP120 trials involved the right insula or auditory cortex and three were not present during PP60 trials. Converging evidence indicates the right insula is the hub of a network underlying AMP.

Not All Differences between Patients with Schizophrenia and Healthy Subjects Are Pathological: Performance on the Conners' Continuous Performance Test

OBJECTIVE

This study analyzed attentional performance in patients with schizophrenia during a continuous performance task requiring a high response rate.

METHOD

The Conners' Continuous Performance Test-II (CPT-II) was administered to 64 patients with schizophrenia and 64 healthy comparison subjects. A cross-sectional design was used in order to allow analysis of the means between patients and healthy subjects. Differences in performance were assessed for significance using ANCOVA. Percentiles were also analyzed in order to determine whether a participant showed normal or pathological performance. Pearson's correlation was used to detect possible relationships between attentional performance and psychopathology.

RESULTS

Of the 12 CPT-II measures, response style and slowing of reaction time (RT) between targets increased to similar extents between patients and healthy comparison subjects. Patients performed significantly less well than non-patient group on all other measures. Nevertheless, patient's performance on four of these measures remained within the normal range, and patient's performance on the remaining measures qualified as pathological only in the case of variability in hit RT. No significant correlations between attention performance and symptoms were found.

CONCLUSIONS

These results suggest that although patients may show lower attentional functioning than non-patients on tasks requiring a high response rate, their attentional performance remains within the normal range on most dimensions.

Effects of Stimulus-Driven and Goal-Directed Attention on Prepulse Inhibition of Brain Oscillations

OBJECTIVE

Prepulse inhibition (PPI) is an operational measure of sensory gating. PPI of cortical response to a startling pulse is known to be modulated by attention. With a time-frequency analysis, we sought to determine whether goal-directed and stimulus-driven attention differentially modulate inhibition of cortical oscillations elicited by a startling pulse.

METHODS

An electroencephalogram (EEG) was recorded in 26 healthy controls performing an active acoustic PPI paradigm. Startling stimuli were presented alone or either 400 or 1000 ms after one of three types of visual prepulse: to-be-attended (goal-directed attention), unexpected (stimulus-driven attention) or to-be-ignored (non-focused attention). We calculated the percentage PPI for the auditory event-related spectral perturbation (ERSP) of theta (4-7 Hz), alpha (8-12 Hz), beta1 (13-20 Hz) and beta2 (20-30 Hz) oscillations and changes in inter-trial coherence (ITC), a measure of phase synchronization of electroencephalographic activity.

RESULTS

At 400 ms: (i) PPI of the ERSP of alpha, theta and beta1 oscillation was greater after an unexpected and a to-be-attended prepulse than after a to-be-ignored prepulse; and (ii) PPI of beta2 oscillations was greater after a to-be-attended than a to-be-ignored prepulse. At 1000 ms: (i) PPI of alpha oscillations was greater after an unexpected and a to-be-attended prepulse than after a to-be-ignored prepulse; and (ii) PPI of beta1 oscillations was greater after a to-be-attended than a to-be-ignored prepulse. The ITC values did not vary according to the type of prepulse.

CONCLUSIONS

In an active PPI paradigm, stimulus-driven and goal-directed attention each have differential effects on the modulation of cortical oscillations.

TCF4 gene polymorphism is associated with cognition in patients with schizophrenia and healthy controls

BACKGROUND

Cognitive deficits have been identified as an important core feature of schizophrenia. Single nucleotide polymorphisms in the transcription factor 4 (TCF4) gene have been reported to be involved in the susceptibility to schizophrenia and be significantly related to cognitive deficits of schizophrenia and controls. This study examines whether the TCF4 rs2958182 polymorphism influences cognitive functions in chronic schizophrenia and controls.

METHODS

The presence of the TCF4 rs2958182 was determined in 976 patients and 420 controls using a case-control design. We assessed all the patients' psychopathology using the Positive and Negative Syndrome Scale (PANSS). Cognition was assessed in 777 patients and 399 controls by using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).

RESULTS

There were marginally significant differences in the TCF4 rs2958182 allelic and genotypic distributions between patients and controls (χ2 = 3.48, p = 0.062 and χ2 = 0.036, p = 0.036, respectively). Cognitive test scores were significantly lower in patients than in controls on all scales (all p < 0.001) except for the visuospatial/constructional index (p > 0.05). There were significant genotype effects on delayed memory score (p = 0.013), the RBANS total score (p = 0.028) and language score (p = 0.034). Further analysis showed that the language score significantly differed according to the genotypic groups (A/A+T/A group versus T/T group) (p = 0.007) in patients but not in controls (p > 0.05), and the delayed memory score also significantly differed according to the genotypic groups (A/A+T/A group versus T/T group) (p = 0.021) in controls but not in patients (p > 0.05).

CONCLUSIONS

This study found that the A allele of the TCF4 rs2958182 polymorphism was the risk allele of schizophrenia, and was associated with lower cognitive performance in language in schizophrenia and delayed memory in controls. In contrast, the T allele of this polymorphism was found to be the schizophrenia risk allele in another study in Han Chinese people.

TCF4 gene polymorphism and cognitive performance in patients with first episode psychosis

BACKGROUND

Single nucleotide polymorphisms in TCF4 gene have been consistently associated with schizophrenia in genome wide association studies, including the C allele of rs9960767. However, its exact role in modulating the schizophrenia phenotype is not known.

AIMS

To comprehensively investigate the relationship between rs9960767 risk allele (C) of TCF4 and cognitive performance in patients with first episode psychosis (FEP).

METHODS

173 patients with FEP received a comprehensive neurocognitive evaluation and were genotyped for rs9960767. Carriers of the risk allele (CA/CC) were compared to non-carriers (AA) using Multivariate Analysis of Covariance MANCOVA. Ethnicity, negative symptoms and substance abuse were included as covariates.

RESULTS

Carriers of the risk allele had a statistically significant lower performance in the cognitive domain of Reasoning/Problem-Solving compared to non-carriers (F1,172=4.4, p=.038). There were no significant genotype effects on the other cognitive domains or general cognition. This effect on the Reasoning/Problem-Solving domain remained significant even when controlling for IQ (F1,172=4.3, p=.039).

CONCLUSIONS

rs9960767 (C) of TCF4 appears to be associated with neurocognitive deficits in the Reasoning/Problem-Solving cognitive domain, in patients with FEP. A confirmation of this finding in a larger sample and including other TCF4 polymorphisms will be needed to gain further validity of this result.

Effects of stimulus-driven and goal-directed attention on prepulse inhibition of the cortical responses to an auditory pulse

OBJECTIVE

Inhibition by a prepulse (prepulse inhibition, PPI) of the response to a startling acoustic pulse is modulated by attention. We sought to determine whether goal-directed and stimulus-driven attention differentially modulate (i) PPI of the N100 and P200 components of the auditory evoked potential (AEP) and (ii) the components' generators.

METHODS

128-channel electroencephalograms were recorded in 26 healthy controls performing an active acoustic PPI paradigm. Startling stimuli were presented alone or either 400 or 1000ms after a visual prepulse. Three types of prepulse were used: to-be-attended (goal-directed attention), unexpected (stimulus-driven attention) or to-be ignored (non focused attention). We calculated the percentage PPI for the N100 and P200 components of the AEP and determined cortical generators by standardized weighted low resolution tomography.

RESULTS

At 400ms, the PPI of the N100 was greater after an unexpected prepulse than after a to-be-attended prepulse, the PPI of the P200 was greater after a to-be-attended prepulse than after a to-be ignored prepulse. At 1000ms, to-be-attended and unexpected prepulses had similar effects. Cortical sources were modulated in areas involved in both types of attention.

CONCLUSIONS

Stimulus-driven attention and goal-directed attention each have specific effects on the attentional modulation of PPI.

SIGNIFICANCE

By using a new PPI paradigm that specifically controls attention, we demonstrated that the early stages of the gating process (as evidenced by N100) are influenced by stimulus-driven attention and that the late stages (as evidenced by P200) are influenced by goal-directed attention.

Associations between TCF4 gene polymorphism and cognitive functions in schizophrenia patients and healthy controls

The SNP rs2958182 was reported to be significantly associated with schizophrenia (SCZ) in Han Chinese. This study examined this SNP's associations with cognitive functions in 580 SCZ patients and 498 controls. Cognitive functions were assessed using the Wechsler Adult Intelligence Scale-Revised (WAIS-RC), the Attention Network Task (ANT), the Stroop task, the dot pattern expectancy (DPX), task and the N-back working memory task. Results showed significant or marginally significant interaction effects between genotype and diagnosis status on IQ (P=0.011) and attention-related tasks (ie, the forward digit span of WAIS-RC, P=0.005; the ANT conflict effect; P=0.020, and its ratios over mean reaction time (RT), P=0.036; the Stroop conflict effect, P=0.032, and its ratios over mean RT, P=0.062; and the DPX task's error rate under the BX condition, P<0.001, and the error rate of BX minus the error rate of AY (BX-AY), P=0.002). There were no such interaction effects on the measures of working memory (all P-values >0.05). Further analysis of the significant genotype-by-diagnosis interactions showed that the risk (T) allele was associated with better performance on cognitive tasks in patients but with worse performance in controls. These results seem to indicate that the association between this SNP and selected cognitive functions may be of an inverted U-shaped pattern. Future research is needed to replicate these results and to explore the biochemical mechanisms behind this association.

Simultaneous EMG-fMRI during startle inhibition in monosymptomatic enuresis--an exploratory study

Evidence is growing that monosymptomatic enuresis (ME) is a maturational disorder of the central nervous system with a lack of arousal and lacking inhibition of the micturition reflex. Previous studies have shown a significant reduction of prepulse inhibition (PPI) of startle in children with enuresis. However, it is still unclear whether the abnormal PPI in enuresis is based on an inhibitory deficit at brainstem or cortical level. Nine children with ME and ten healthy children were investigated using simultaneous recording of EMG from the M. orbicularis oculi and functional MRI. The experimental paradigm consisted of acoustic startle stimulation, with startle-alone stimuli and prepulse-startle combinations. Functional MRI data were processed using multiple regression and parametric modulation with startle amplitudes as a parameter. Neither patients with enuresis nor healthy children revealed measurable PPI in the MRI scanner. Startle stimuli caused equal hemodynamic changes in the acoustic cortex, medial prefrontal and orbitofrontal cortex in both groups. The amplitude of startle correlated with more prominent BOLD signal changes in the anterior cingulate cortex in healthy subjects than in patients with ME. This pronounced frontal activation in healthy controls was related to the PPI condition, indicating that the prefrontal cortex of healthy children was activated more strongly to inhibit startle than in patients with ME. In conclusion, apart from the possibility that recordings of PPI inside the MRI scanner may be compromised by methodological problems, the results of this study suggest that high cortical control mechanisms at the prefrontal level are relevant for the pathogenesis of ME.

Lack of relationship between acoustic startle and cognitive variables in schizophrenia and control subjects

Measures of acoustic startle such as prepulse inhibition (PPI) and startle latency have been found to be impaired in schizophrenia, and are commonly thought to be related to cognitive deficits in this disease. However, findings about the relationship between startle variables and cognitive performance have been equivocal. In this study, we examined correlations between startle measures (baseline startle magnitude, latency, habituation and PPI) and cognitive performance (using the Benton Visual Retention Test, Conner's Continuous Performance Test, California Verbal Learning Test, Finger Tapping Test, and Wisconsin Card Sort Test) in 107 schizophrenia patients and 94 healthy controls. Overall, there was a lack of any significant relationship between these constructs in both populations when correcting for multiple comparisons. This suggests that alterations in startle measures seen in schizophrenia may not reflect elements of information processing that cause cognitive deficits in the disease.

Emotion-modulated startle in anxiety disorders is blunted by co-morbid depressive episodes

BACKGROUND

While anxiety has been associated with exaggerated emotional reactivity, depression has been associated with blunted, or context insensitive, emotional responding. Although anxiety and depressive disorders are frequently co-morbid, surprisingly little is known about emotional reactivity when the two disorders co-occur.

METHOD

We utilized the emotion-modulated startle (EMS) paradigm to examine the effects of a concurrent depressive episode on emotional reactivity in young adults with anxiety disorders. Using an archival dataset from a multi-disciplinary project on risk factors in childhood-onset depression, we examined eye-blink startle reactions to late-onset auditory startle probes while participants viewed pictures with affectively pleasant, unpleasant and neutral content. EMS response patterns were analyzed in 33 individuals with a current anxiety (but no depressive) disorder, 24 individuals with a current anxiety disorder and co-morbid depressive episode and 96 healthy controls.

RESULTS

Control participants and those with a current anxiety disorder (but no depression) displayed normative linearity in startle responses, including potentiation by unpleasant pictures. By contrast, individuals with concurrent anxiety and depression displayed blunted EMS.

CONCLUSIONS

An anxiety disorder concurrent with a depressive episode is associated with reactivity that more closely resembles the pattern of emotional responding that is typical of depression (i.e. context insensitive) rather than the pattern that is typical for anxiety (i.e. exaggerated).

Sensorimotor gating and vigilance-dependent choice accuracy: a within-subject correlative analysis in wild-type C57BL/6 mice

Deterioration in attention and related processes is an early sign in schizophrenia predictive of disease development. Amongst the various translational paradigms for assessing attention in rodents, it is not known if they are equivalent in detecting individual differences. Answers here are pertinent to their use in the general human population for identifying individuals at high risk of developing schizophrenia. The present study employed a within-subject approach to examine in mice two common paradigms for assessing attention that differ markedly in their implementation. An operant-based two-choice visual discrimination task (2-CVDT) that depends on effortful attention to brief visual cues was contrasted with prepulse inhibition (PPI) of the acoustic startle reflex, a well-established test of pre-attentive gating whereby processing of a startle-eliciting stimulus is inhibited by a preceding weak prepulse stimulus. Here, we revealed a correlation showing that individual mice with low PPI tended to perform poorly in the 2-CVDT in terms of choice accuracy but not response speed. This specific positive correlation suggests that the two readouts might be regulated via common attentional mechanisms, which might be critically dependent on normal muscarinic and N-methyl-d-asparate receptor functions. As demonstrated here, blockade of either receptor type by scopolamine or dizocilpine impaired 2-CVDT performance at doses that have been shown to disrupt PPI in mice. Further studies contrasting these two paradigms would be warranted to characterize the possible underlying psychological constructs that give rise to this correlation and to clarify whether the two paradigms may effectively capture schizophrenia-related cognitive deficits belonging to orthogonal domains.

Alterations to pre-pulse inhibition (PPI) in chronic cannabis users are secondary to sustained attention deficits

RATIONALE

Given the hypothesised association between cannabis use and schizophrenia, and the well documented alterations in pre-pulse inhibition (PPI) that are observed in schizophrenia, it is of interest to examine the effects of cannabis use on PPI.

OBJECTIVE

The objective of the study was to use novel methodology for the measurement and characterisation of attentional modulation of PPI, in order to examine the nature of PPI in chronic cannabis users.

METHODS

PPI was measured in 34 chronic cannabis users (who were otherwise healthy) and 32 healthy controls, across a range of startling stimulus intensities, during two attention set conditions, one in which they were instructed to attend to the auditory stimuli and one in which they were instructed to ignore the auditory stimuli and focus on a visual task. Curves of best fit were fitted to the startle magnitudes, across the stimulus intensities. A number of reflex parameters were extracted from these logistic functions, each of which reflects a different characteristic of the startle response.

RESULTS

Cannabis users failed to show attentional modulation of any of the reflex parameters and showed altered PPI, relative to controls, but only when they were instructed to sustain attention to the auditory stimuli.

CONCLUSION

Cannabis users showed an attention-dependant alteration in PPI, which appeared to reflect a deficit in sustain attention, and which was different to that which has been observed in schizophrenia using the same methodology.

Prefrontal cognitive dysfunction is associated with tobacco dependence treatment failure in smokers with schizophrenia

BACKGROUND

Patients with schizophrenia have higher rates of smoking (58-88%) than in the general population ( approximately 22%), and are more refractory to smoking cessation. These patients also exhibit numerous neurocognitive deficits, some of which may be ameliorated by cigarette smoking. The neurocognitive benefits derived from nicotine may, in turn, contribute to elevated rates of smoking and smoking persistence in schizophrenia. The present study examined the relationship between neurocognitive function and smoking cessation in schizophrenia.

METHODS

Treatment-seeking smokers with schizophrenia (N=58) participated in a 10-week placebo-controlled trial of sustained-release (SR) bupropion plus transdermal nicotine patch. Neuropsychological performance was evaluated in a subset of patients (n=31), prior to pharmacological treatment, using a neurocognitive battery.

RESULTS

Subjects were compared as a function of endpoint smoking status (Quit versus Not Quit), assessed by end of trial 7-day point prevalence abstinence, confirmed by CO level (< 10 ppm) on demographic traits, smoking, and clinical outcomes. While there were no significant baseline differences between quitters and non-quitters, non-quitters exhibited significantly greater deficits in performance on Trail Making Test, Part B (p=0.01) and on Digit Span backwards (p=0.04) compared to quitters. No associations were found between quit status and performance on other neuropsychological measures.

CONCLUSIONS

Our findings extend results of previous studies which suggest deficits in frontal executive function are associated with smoking cessation failure in schizophrenia. This may have implications for the development of tailored smoking cessation treatments in this population.

Frontal-striatal-thalamic mediodorsal nucleus dysfunction in schizophrenia-spectrum patients during sensorimotor gating

Prepulse inhibition (PPI) refers to a reduction in the amplitude of the startle eyeblink reflex to a strong sensory stimulus, the pulse, when it is preceded shortly by a weak stimulus, the prepulse. PPI is a measure of sensorimotor gating which serves to prevent the interruption of early attentional processing and it is impaired in schizophrenia-spectrum patients. In healthy individuals, PPI is more robust when attending to than ignoring a prepulse. Animal and human work demonstrates that frontal-striatal-thalamic (FST) circuitry modulates PPI. This study used functional magnetic resonance imaging (fMRI) to investigate FST circuitry during an attention-to-prepulse paradigm in 26 unmedicated schizophrenia-spectrum patients (13 schizotypal personality disorder (SPD), 13 schizophrenia) and 13 healthy controls. During 3T-fMRI acquisition and separately measured psychophysiological assessment of PPI, participants heard an intermixed series of high- and low-pitched tones serving as prepulses to an acoustic-startle stimulus. Event-related BOLD response amplitude curves in FST regions traced on co-registered anatomical MRI were examined. Controls showed greater activation during attended than ignored PPI conditions in all FST regions-dorsolateral prefrontal cortex (Brodmann areas 46, 9), striatum (caudate, putamen), and the thalamic mediodorsal nucleus. In contrast, schizophrenia patients failed to show differential BOLD responses in FST circuitry during attended and ignored prepulses, whereas SPD patients showed greater-than-normal activation during ignored prepulses. Among the three diagnostic groups, lower left caudate BOLD activation during the attended PPI condition was associated with more deficient sensorimotor gating as measured by PPI. Schizophrenia-spectrum patients exhibit inefficient utilization of FST circuitry during attentional modulation of PPI. Schizophrenia patients have reduced recruitment of FST circuitry during task-relevant stimuli, whereas SPD patients allocate excessive resources during task-irrelevant stimuli. Dysfunctional FST activation, particularly in the caudate may underlie PPI abnormalities in schizophrenia-spectrum patients.