Color Stroop and negative priming in schizophrenia: an fMRI study

Neural correlates of prediction error in patients with schizophrenia: evidence from an fMRI meta-analysis

Abnormal processes of learning from prediction errors, i.e. the discrepancies between expectations and outcomes, are thought to underlie motivational impairments in schizophrenia. Although dopaminergic abnormalities in the mesocorticolimbic reward circuit have been found in patients with schizophrenia, the pathway through which prediction error signals are processed in schizophrenia has yet to be elucidated. To determine the neural correlates of prediction error processing in schizophrenia, we conducted a meta-analysis of whole-brain neuroimaging studies that investigated prediction error signal processing in schizophrenia patients and healthy controls. A total of 14 studies (324 schizophrenia patients and 348 healthy controls) using the reinforcement learning paradigm were included. Our meta-analysis showed that, relative to healthy controls, schizophrenia patients showed increased activity in the precentral gyrus and middle frontal gyrus and reduced activity in the mesolimbic circuit, including the striatum, thalamus, amygdala, hippocampus, anterior cingulate cortex, insula, superior temporal gyrus, and cerebellum, when processing prediction errors. We also found hyperactivity in frontal areas and hypoactivity in mesolimbic areas when encoding prediction error signals in schizophrenia patients, potentially indicating abnormal dopamine signaling of reward prediction error and suggesting failure to represent the value of alternative responses during prediction error learning and decision making.

Selective processing in attention and memory in schizophrenia: A meta-analysis of the negative priming effect

Individuals with schizophrenia show impairments in a variety of selective attention tasks. Research on the negative priming (NP) effect in schizophrenia has yielded mixed evidence. This meta-analysis aimed to examine the NP effect exhibited by patients with schizophrenia and the impact of study methodology on findings. The methods and reporting of this meta-analysis followed the PRISMA guideline. Eligible studies were identified through primary literature search in MEDLINE, PsycInfo, PsycArticles, and Embase and secondary search based on included studies and important reviews. Three-level random effects-models were used to summarize between-group differences in the raw NP score, as well as the NP ratio and baseline reaction time (RT) as secondary outcomes. We identified 1383 studies published between 1966 and 2022 and reviewed 27 studies that consist of 627 patients with schizophrenia and 653 controls in total. Compared to healthy controls, patients with schizophrenia showed a mildly reduced raw NP score with marginal significance, Hedges' g = -0.16, 95% confidence interval (CI) -0.35 to 0.02, p = 0.084. However, analysis of a subsample of studies indicated a significant, moderate reduction in the NP ratio among patients, g = -0.52, 95% CI -0.91 to -0.14; p = 0.014. Moderator analyses revealed a longer illness duration as predictive of a more reduced NP effect. This meta-analysis lends tentative evidence to impaired attention or memory process as measured by the NP task in schizophrenia. More research is needed to substantiate our results and clarify the impact of study design and patient characteristics on findings.

How processing emotion affects language control in bilinguals

Research has shown that several variables affect language control among bilingual speakers but the effect of affective processing remains unexplored. Chinese-English bilinguals participated in a novel prime-target language switching experiment in which they first judged the affective valence (i.e., positive or negative) of auditorily presented words and then named pictures with neutral emotional valence in either the same (non-switch trial) or different language (switch trial). Brain activity was monitored using functional magnetic resonance imaging (fMRI). The behavioral performance showed that the typical switch cost (i.e., the calculated difference between switch and non-switch trials) emerged after processing positive words but not after negative words. Brain imaging demonstrated that processing negative words immediately before non-switch picturing naming trials (but not for switch trials) increased activation in brain areas associated with domain-general cognitive control. The opposite patterns were found after processing positive words. These findings suggest that an (emotional) negative priming effect is induced by spontaneous exposure to negative words and that these priming effects may be triggered by reactive emotional processing and that they may interact with higher level cognitive functions.

A multimodal magnetoencephalography 7 T fMRI and 7 T proton MR spectroscopy study in first episode psychosis

We combined magnetoencephalography (MEG), 7 T proton magnetic resonance spectroscopy (MRS), and 7 T fMRI during performance of a task in a group of 23 first episode psychosis (FEP) patients and 26 matched healthy controls (HC). We recorded both the auditory evoked response to 40 Hz tone clicks and the resting state in MEG. Neurometabolite levels were obtained from the anterior cingulate cortex (ACC). The fMRI BOLD response was obtained during the Stroop inhibitory control task. FEP showed a significant increase in resting state low frequency theta activity (p < 0.05; Cohen d = 0.69), but no significant difference in the 40 Hz auditory evoked response compared to HC. An across-groups whole brain analysis of the fMRI BOLD response identified eight regions that were significantly activated during task performance (p < 0.01, FDR-corrected); the mean signal extracted from those regions was significantly different between the groups (p = 0.0006; d = 1.19). In the combined FEP and HC group, there was a significant correlation between the BOLD signal during task performance and MEG resting state low frequency activity (p < 0.05). In FEP, we report significant alteration in resting state low frequency MEG activity, but no alterations in auditory evoked gamma band response, suggesting that the former is a more robust biomarker of early psychosis. There were no correlations between gamma oscillations and GABA levels in either HC or FEP. Finally, in this study, each of the three imaging modalities differentiated FEP from HC; fMRI with good and MEG and MRS with moderate effect size.

The effect of bilateral high frequency repetitive transcranial magnetic stimulation on cognitive functions in schizophrenia

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Despite their major effects on positive symptoms, antipsychotics do not have a significant effect on cognition in schizophrenia

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Bilateral high frequency rTMS targeting dorsolateral prefrontal cortices has been effective on working memory

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Bilateral 20 Hz rTMS improved attention and verbal working memory in schizophrenia patients,

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It also improved the competence of switching the perceptional set up under a disruptive effect towards new instructions, in this study

Eye Movement Performance on the Stroop Test in Adults With ADHD

Objective: To compare the eye movement patterns of adults with ADHD with those of controls as they perform the Stroop test. Method: Thirty individuals with ADHD (ages 18-31), and 30 controls participated in this study. The hypothesis was that under the incongruent condition, the group with ADHD would focus longer on the distracter than the controls. Results: Participants with ADHD showed a more pronounced Stroop effect than the controls. Eye movements indicated that more time was spent fixating on the target than on the distracter. The most significant differences between the groups were the overall time spent on the target and the number of fixations on the target, rather than on the distracter. Furthermore, the group with ADHD made more transitions between the target and distracter stimuli. Conclusion: These results were interpreted to indicate an inefficient strategy used by the group with ADHD in their attempt to ignore the distracter stimuli.

A review of impaired visual processing and the daily visual world in patients with schizophrenia

Several studies have investigated perceptual processes in patients with schizophrenia. Research confirms that visual impairments are one of the most important features of schizophrenia. Many studies, using behavioral and psychological experiments, confirm that visual impairments can be used to determine illness severity, state, and best treatments. Herein, we review recent research pertaining to visual function in patients with schizophrenia and highlight the relationship between laboratory findings and subjective, real-life reports from patients themselves. The purpose of this review is to 1) describe visual impairments that manifest in patients with schizophrenia, 2) examine the relationship between visual dysfunction, assessed by laboratory tests, and the experiences of patients themselves, and 3) describe real-life experiences related to visual function in this population. In this review, the impairments of motion and color perception, perceptual organization, and scan paths are summarized, along with the relationship between laboratory findings and patients' real-world subjective experiences related to visual function.

Relationship Between Cortical Excitation and Inhibition and Task-Induced Activation and Deactivation: A Combined Magnetic Resonance Spectroscopy and Functional Magnetic Resonance Imaging Study at 7T in First-Episode Psychosis

BACKGROUND

Schizophrenia is thought to be a disorder of brain dysconnectivity. An imbalance between cortical excitation/inhibition is also implicated, but the link between these abnormalities remains unclear. The present study used magnetic resonance spectroscopy and functional magnetic resonance imaging at 7T to investigate how measurements of glutamate and gamma-aminobutyric acid (GABA) relate to the blood oxygen level-dependent (BOLD) response during a cognitive task, and how these relationships are altered in schizophrenia.

METHODS

Usable functional magnetic resonance imaging data from 17 first-episode psychosis (FEP) patients (4 women, 13 men) and 21 matched healthy control subjects (HCs) (5 women, 16 men) were acquired during a Stroop task. Within- and between-group comparisons of the BOLD response were performed. Neurometabolite levels were measured in the dorsal anterior cingulate cortex. Two multiple regressions investigated how glutamate, glutamine, and GABA related to the BOLD response in HCs and FEP patients separately. A third investigated between-group differences in the relationships between the BOLD response and each of these neurometabolites.

RESULTS

Compared with HCs, FEP patients showed an increased BOLD response within regions of the executive and default mode networks. In FEP patients, the relationship between anterior cingulate cortex glutamate levels and the BOLD response in regions of the posterior default mode network was opposite to that of HCs. In FEP patients but not HCs, anterior cingulate cortex GABA levels correlated with the local BOLD response and with the Stroop reaction time.

CONCLUSION

These results suggest a mechanism whereby alterations in the relationship between cortical glutamate/GABA and BOLD response is disrupting the dynamic of major neural networks, possibly affecting cognition.

Executive Functions Brain System: An Activation Likelihood Estimation Meta-analytic Study

Background and objective

To characterize commonalities and differences between two executive functions: reasoning and inhibitory control.

Methods

A total of 5,974 participants in 346 fMRI experiments of inhibition or reasoning were selected. First level analysis consisted of Analysis of Likelihood Estimation (ALE) studies performed in two pooled data groups: (a) brain areas involved in reasoning and (b) brain areas involved in inhibition. Second level analysis consisted of two contrasts: (i) brain areas involved in reasoning but not in inhibition and (ii) brain areas involved in inhibition but not in reasoning. Lateralization Indexes were calculated.

Results

Four brain areas appear as the most critical: the dorsolateral aspect of the frontal lobes, the superior parietal lobules, the mesial aspect of the premotor area (supplementary motor area), and some subcortical areas, particularly the putamen and the thalamus. ALE contrasts showed significant differentiation of the networks, with the reasoning > inhibition-contrast showing a predominantly leftward participation, and the inhibition > reasoning-contrast, a clear right advantage.

Conclusion

Executive functions are mediated by sizable brain areas including not only cortical, but also involving subcortical areas in both hemispheres. The strength of activation shows dissociation between the hemispheres for inhibition (rightward) and reasoning (leftward) functions.

Neuroimaging results suggest the role of prediction in cross-domain priming

The repetition of a stimulus leads to shorter reaction times as well as to the reduction of neural activity. Previous encounters with closely related stimuli (primes) also lead to faster and often to more accurate processing of subsequent stimuli (targets). For instance, if the prime is a name, and the target is a face, the recognition of a persons’ face is facilitated by prior presentation of his/her name. A possible explanation for this phenomenon is that the prime allows predicting the occurrence of the target. To the best of our knowledge, so far, no study tested the neural correlates of such cross-domain priming with fMRI. To fill this gap, here we used names of famous persons as primes, and congruent or incongruent faces as targets. We found that congruent primes not only reduced RT, but also lowered the BOLD signal in bilateral fusiform (FFA) and occipital (OFA) face areas. This suggests that semantic information affects not only behavioral performance, but also neural responses in relatively early processing stages of the occipito-temporal cortex. We interpret our results in the framework of predictive coding theories.

Cognitive fatigue effects on physical performance: A systematic review and meta-analysis

Recent research has examined the effect that undertaking a cognitively fatiguing task for ≤90 min has on subsequent physical performance. Cognitive fatigue is claimed to affect subsequent physical performance by inducing energy depletion in the brain, depletion of brain catecholamine neurotransmitters or changes in motivation. Observation of the psychophysiology and neurochemistry literature questions the ability of 90 min' cognitive activity to deplete energy or catecholamine resources. The purpose of this study, therefore, was to examine the evidence for cognitive fatigue having an effect on subsequent physical performance. A systematic, meta-analytic review was undertaken. We found a small but significant pooled effect size based on comparison between physical performance post-cognitive fatigue compared to post-control (g = -0.27, SE = -0.12, 95% CI -0.49 to -0.04, Z(10) = -2.283, p < 0.05). However, the results were not heterogenous (Q(10) = 2.789, p > 0.10, Τ² < 0.001), suggesting that the pooled effect size does not amount to a real effect and differences are due to random error. No publication bias was evident (Kendall's τ = -0.07, p > 0.05). Thus, the results are somewhat contradictory. The pooled effect size shows a small but significant negative effect of cognitive fatigue, however tests of heterogeneity show that the results are due to random error. Future research should use neuroscientific tests to ensure that cognitive fatigue has been achieved.

RETRACTED: The effects of perceptual load in processing emotional facial expression in psychotic disorders

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the authors and Editor-in-Chief. The Authors have recently discovered an error in the database that affects the results and, consequently, the discussion, conclusions and abstract of this article on the effects of perceptual load and task-irrelevant facial expression during a target-letter discrimination task in psychotic disorders. The error was discovered by the Authors during the analysis of new data using the same experimental task, but collected from a distinct clinical sample, and involves a systematic error in the database: pictures of one actor were coded as depicting the same valence (angry, happy, neutral) during the programming of the experimental task, regardless of the real facial expression portraited by the picture in each trial. As a result, the information provided by the ‘Emotion’ variable in the database, created by the E-Prime software for each participant during the performance of the task, was not correct. Because the Authors used the ‘Emotion’ variable to perform the statistical analysis, the results of lower accuracy for individuals diagnosed with psychotic disorders in trials where the task-irrelevant stimuli are happy facial expressions - as revealed by a significant interaction between group and facial expression (p = .016) and between group, perceptual load and facial expression (p = .027) - are not correct, thus partially affecting the discussion, conclusions and abstract of the manuscript. Besides the ‘Emotion’ variable, the raw database contains the filename of the picture presented in each trial. Therefore, the Authors were able to correct the error and to re-analyse the data, and will proceed with the submission for publication of the corrected version of the manuscript. The error had no influence on the design and procedure of the experimental task, as the order of the pictures was fully randomized per participant. The Authors apologize for the inconvenience caused by these mistakes and agree with the retraction. The Authors advise all researchers to pay special attention when scripting/coding the stimuli to be used in the experimental tasks, and to confirm all scripting/coding with independent researchers, whenever possible, to prevent mistakes (Strand, 2021). The Journal apologizes that these errors were not detected during peer review.

Long-Term Experience of Chinese Calligraphic Handwriting Is Associated with Better Executive Functions and Stronger Resting-State Functional Connectivity in Related Brain Regions

Chinese calligraphic handwriting (CCH) is a traditional art form that requires high levels of concentration and motor control. Previous research has linked short-term training in CCH to improvements in attention and memory. Little is known about the potential impacts of long-term CCH practice on a broader array of executive functions and their potential neural substrates. In this cross-sectional study, we recruited 36 practitioners with at least 5 years of CCH experience and 50 control subjects with no more than one month of CCH practice and investigated their differences in the three components of executive functions (i.e., shifting, updating, and inhibition). Valid resting-state fMRI data were collected from 31 CCH and 40 control participants. Compared with the controls, CCH individuals showed better updating (as measured by the Corsi Block Test) and inhibition (as measured by the Stroop Word-Color Test), but the two groups did not differ in shifting (as measured by a cue-target task). The CCH group showed stronger resting-state functional connectivity (RSFC) than the control group in brain areas involved in updating and inhibition. These results suggested that long-term CCH training may be associated with improvements in specific aspects of executive functions and strengthened neural networks in related brain regions.

ACC Neuro-over-Connectivity Is Associated with Mathematically Modeled Additional Encoding Operations of Schizophrenia Stroop-Task Performance

Functional magnetic resonance imaging at 7.0 Tesla was undertaken among Schizophrenia participants (Sz), and clinical (major mood disorder; MDD) and healthy controls (HC), during performance of the Stoop task. Stroop conditions included congruent and incongruent word color items, color-only items, and word-only items. Previous modeling results extended to this most widely used selective-attention task. All groups executed item-encoding operations (subprocesses of the item encoding process) at the same rate (performance accuracy being similarly high throughout), thus displaying like processing capacity; Sz participants, however, employed more subprocesses for item completions than did the MDD participants, who in turn used more subprocesses than the HC group. The reduced efficiency in deploying cognitive-workload capacity among the Sz participants was paralleled by more diffuse neuroconnectivity (Blood-Oxygen-Level-Dependent co-activation) with the anterior cingulate cortex (ACC) (Broadman Area 32), spreading away from this encoding-intensive region; and by less evidence of network dissociation across Stroop conditions. Estimates of cognitive work done to accomplish item completion were greater for the Sz participants, as were estimates of entropy in both the modeled trial-latency distribution, and its associated neuro-circuitry. Findings are held to be symptom and assessment significant, and to have potential implications for clinical intervention.

Behavior, neuropsychology and fMRI

Cognitive neuroscientists in the late 20th century began the task of identifying the part(s) of the brain concerned with normal behavior as manifest in the psychological capacities as affective powers, reasoning, behaving purposively and the pursuit of goals, following introduction of the 'functional magnetic resonance imaging' (fMRI) method for identifying brain activity. For this research program to be successful two questions require satisfactory answers. First, as the fMRI method can currently only be used on stationary subjects, to what extent can neuropsychological tests applicable to such stationary subjects be correlated with normal behavior. Second, to what extent can correlations between the various neuropsychological tests on the one hand, and sites of brain activity determined with fMRI on the other, be regarded as established. The extent to which these questions have yet received satisfactory answers is reviewed, and suggestions made both for improving correlations of neuropsychological tests with behavior as well as with the results of fMRI-based observations.

The negative priming paradigm: An update and implications for selective attention

Negative Priming (NP) is an influential paradigm in cognitive psychology that was originally developed to measure attentional selection. Yet, up to the mid-1990s, a large number of experimental reports questioned whether the NP effect is based on attentional inhibition and/or episodic retrieval processes. In this review, we summarize findings since the mid-1990s and discuss new and old theoretical approaches to Negative Priming. We conclude that more than one process contributes to NP and that future research should analyze the conditions under which a particular process contributes to NP. Moreover, we argue that the paradigm--although it does not measure a single cognitive process alone--is still a useful tool for understanding selection in cognition. In fact, it might be a virtue of the paradigm that several cognitive processes work here together as selection in nonexperimental contexts is surely a multidimensional process. From this perspective, research on NP is relevant for all research fields analyzing selection. We therefore close our review by discussing the implications of the new evidence on NP for theories of selective attention.

An fMRI study of multimodal selective attention in schizophrenia

BACKGROUND

Studies have produced conflicting evidence regarding whether cognitive control deficits in patients with schizophrenia result from dysfunction within the cognitive control network (CCN; top-down) and/or unisensory cortex (bottom-up).

AIMS

To investigate CCN and sensory cortex involvement during multisensory cognitive control in patients with schizophrenia.

METHOD

Patients with schizophrenia and healthy controls underwent functional magnetic resonance imaging while performing a multisensory Stroop task involving auditory and visual distracters.

RESULTS

Patients with schizophrenia exhibited an overall pattern of response slowing, and these behavioural deficits were associated with a pattern of patient hyperactivation within auditory, sensorimotor and posterior parietal cortex. In contrast, there were no group differences in functional activation within prefrontal nodes of the CCN, with small effect sizes observed (incongruent-congruent trials). Patients with schizophrenia also failed to upregulate auditory cortex with concomitant increased attentional demands.

CONCLUSIONS

Results suggest a prominent role for dysfunction within auditory, sensorimotor and parietal areas relative to prefrontal CCN nodes during multisensory cognitive control.

Increased glutamate levels observed upon functional activation in the anterior cingulate cortex using the Stroop Task and functional spectroscopy

It has been shown in recent studies that it is possible to detect changes in the main excitatory neurotransmitter, glutamate, upon functional activation with visual and motor paradigms using a 7 T MRI and functional magnetic resonance spectroscopy. A cognitive task would be desirable for this technique because it could then be used to examine psychiatric disorders that have cognitive deficiencies. The aim of the work presented here was to use functional magnetic resonance spectroscopy with a 7 T MRI to show that increases in glutamate can be observed within the anterior cingulate cortex using the Stroop Task as the activation paradigm in healthy controls. Significant glutamate increases (0.24±0.09 µmol/g, P<0.025), comparable with what has been reported in the studies of the occipital cortex and motor cortex, were observed when the participants (n=7) performed the task, followed by a trend toward returning to baseline in the post-task recovery period (−0.23±0.13 µmol/g). This method would be ideal for the study of neuropsychiatric disorders that have been shown to have abnormal resting glutamate levels and cognitive deficiencies in the anterior cingulate cortex, such as schizophrenia. This exploratory study is the first to demonstrate functional magnetic resonance spectroscopy in the anterior cingulate with a cognitive task using a 7 T MRI.

Functional magnetic resonance spectroscopy of glutamate in schizophrenia and major depressive disorder: anterior cingulate activity during a color-word Stroop task

Background:

Glutamate abnormalities have been suggested to be associated with symptoms of schizophrenia. Using functional magnetic resonance spectroscopy (¹H-fMRS), it is possible to monitor glutamate dynamically in the activated brain areas, which has yet to be reported in schizophrenia. It was hypothesized that subjects with schizophrenia would have weaker glutamatergic responses in the anterior cingulate to a color-word Stroop Task.

AIMS:

The aim of this study was to gain insight into the health of GLU neurotransmission and the GLU-GLN cycle in SZ using a ¹H-fMRS protocol.

Methods:

Spectra were acquired from the anterior cingulate of 16 participants with schizophrenia, 16 healthy controls and 16 participants with major depressive disorder (MDD) while performing the Stroop task in a 7T magnetic resonance imaging scanner. ¹H-fMRS spectra were acquired for 20 min in which there were three 4-min blocks of cross fixation interleaved with two 4-min blocks of the Stroop paradigm.

Results:

A repeated-measures analysis of variance revealed a main effect of time for glutamate concentrations of all groups (P<0.001). The healthy control group increased glutamate concentrations in the first run of the Stroop task (P=0.006) followed by a decrease in the recovery period (P=0.007). Neither the schizophrenia (P=0.107) nor MDD (P=0.081) groups had significant glutamate changes in the first run of the task, while the schizophrenia group had a significant increase in glutamine (P=0.005). The MDD group decreased glutamate concentrations in the second run of the task (P=0.003), as did all the groups combined (P=0.003).

Conclusions:

¹H-fMRS data were successfully acquired from psychiatric subjects with schizophrenia and mood disorder using a cognitive paradigm for the first time. Future study designs should further elucidate the glutamatergic response to functional activation in schizophrenia.

Baroreceptor activity impacts upon controlled but not automatic distractor processing

Changes within the cardiovascular system have been shown to alter sensorimotor and memory performance, pain perception as well as cortical arousal. This influence is assumed to be mediated by afferent feedback of baroreceptors that when stimulated exert inhibitory effects on cortical structures. Mainly responsible for short-term regulation of blood pressure, afferents of the baroreceptors are widely connected to subcortical and cortical structures like the insular cortex. A putative impact on cognitive control processes remains an open question, however. Using a sequential distractor priming task, the present study investigated whether inhibitory influences of baroreceptor activation apply to selective information processing in the presence of irrelevant information. In particular, we assessed distractor-response binding and Negative Priming as indices of automatic and controlled distractor processing, respectively. Baroreceptor activation was experimentally manipulated by the systematic variation of body position. The results showed that only Negative Priming but not distractor-response binding was modulated by body position suggesting that controlled but not automatic processing of distractors is affected by baroreceptor activity.

Evidence for corticostriatal dysfunction during cognitive skill learning in adolescent siblings of patients with childhood-onset schizophrenia

Patients with schizophrenia perform poorly on cognitive skill learning tasks. This study is the first to investigate the neural basis of impairment in cognitive skill learning in first-degree adolescent relatives of patients with schizophrenia. We used functional magnetic resonance imaging to compare activation in 16 adolescent siblings of patients with childhood-onset schizophrenia (COS) and 45 adolescent controls to determine whether impaired cognitive skill learning in individuals with genetic risk for schizophrenia was associated with specific patterns of neural activation. The siblings of patients with COS were severely impaired on the Weather Prediction Task (WPT) and showed a relative deactivation in frontal regions and in the striatum after extensive training on the WPT compared with controls. These differences were not accounted for by performance differences in the 2 groups. The results suggest that corticostriatal dysfunction may be part of the liability for schizophrenia.

Meta-analysis of functional neuroimaging studies indicates that an increase of cognitive difficulty during executive tasks engages brain regions associated with time perception

OBJECTIVES

We hypothesize that time perception and executive functions are interrelated and share neuroanatomical basis, and that fluctuations in levels of cognitive effort play a role in mediating that relation. The main goal of this study was to identify brain structures activated both by increases in cognitive activity and during time perception tasks.

METHODS

We performed a multimodal meta-analysis to identify common brain regions in the findings of (a) an SDM meta-analysis of neuroimaging studies assessing the brain response to increasing levels of cognitive difficulty, and (b) an ALE meta-analysis on neuroimaging of time perception (Ortuño, Guillén-Grima, López-García, Gómez, & Pla, 2011. Schizophr. Res., 125(2-3), 129-35).

RESULTS AND CONCLUSIONS

Consistent with results of previous, separate meta-analyses, the current study supports the hypothesis that there exists a group of brain regions engaged both in time perception tasks and during tasks requiring cognitive effort. Thus, brain regions associated with working memory and executive functions were found to be engaged during time estimation tasks, and regions associated with time perception were found to be engaged by an increase in the difficulty of non-temporal tasks. The implication is that temporal perception and cognitive processes demanding cognitive control become interlinked when there is an increase in the level of cognitive effort demanded.

Subcortical modulation of attentional control by second-generation antipsychotics in first-episode psychosis

Psychotic disorders are characterized by significant deficits in attentional control, but the neurobiological mechanisms underlying these deficits early in the course of illness prior to extensive pharmacotherapy are not well understood. Moreover, little is known regarding the symptom and brain changes associated with amelioration of attentional impairments through antipsychotic pharmacotherapy. In this study 14 male patients experiencing a first-episode of psychosis with minimal prior antipsychotic treatment completed an attentional control task while undergoing functional magnetic resonance imaging at the onset of treatment with a second generation antipsychotic (risperidone or aripiprazole) in a double blind randomized clinical trial and then again following approximately 12 weeks of treatment. In addition, 14 age-, and performance-matched healthy male volunteers who were not treated completed the same task at a baseline timepoint and then again following 12 weeks. Patients showed significantly greater activation than healthy volunteers in the right globus pallidus, left thalamus, and right thalamus at the time of the baseline scan. Among patients there was a significant reduction in right globus pallidus blood-oxygen level dependent (BOLD) response following antipsychotic treatment that correlated significantly with improvement in response accuracy and reductions in thought disturbance. No changes in globus pallidus activation were observed in healthy volunteers over this time period. These preliminary findings suggest that improvement in attentional control and concomitant reductions in thought disturbance in first-episode psychosis may be associated with reductions in subcortical activity following administration of second-generation antipsychotics early in the course of illness. These findings have implications for understanding how changes in basal ganglia activity may be linked to improvements in attentional control through antipsychotics.

A multiple kernel learning approach to perform classification of groups from complex-valued fMRI data analysis: application to schizophrenia

FMRI data are acquired as complex-valued spatiotemporal images. Despite the fact that several studies have identified the presence of novel information in the phase images, they are usually discarded due to their noisy nature. Several approaches have been devised to incorporate magnitude and phase data, but none of them has performed between-group inference or classification. Multiple kernel learning (MKL) is a powerful field of machine learning that finds an automatic combination of kernel functions that can be applied to multiple data sources. By analyzing this combination of kernels, the most informative data sources can be found, hence providing a better understanding of the analyzed learning task. This paper presents a methodology based on a new MKL algorithm (ν-MKL) capable of achieving a tunable sparse selection of features' sets (brain regions' patterns) that improves the classification accuracy rate of healthy controls and schizophrenia patients by 5% when phase data is included. In addition, the proposed method achieves accuracy rates that are equivalent to those obtained by the state of the art lp-norm MKL algorithm on the schizophrenia dataset and we argue that it better identifies the brain regions that show discriminative activation between groups. This claim is supported by the more accurate detection achieved by ν-MKL of the degree of information present on regions of spatial maps extracted from a simulated fMRI dataset. In summary, we present an MKL-based methodology that improves schizophrenia characterization by using both magnitude and phase fMRI data and is also capable of detecting the brain regions that convey most of the discriminative information between patients and controls.

Negative priming in amphetamine psychosis

Amphetamine abuse may lead to a psychotic state, its symptomatology being very similar to what is seen in paranoid schizophrenia. Failure of attentional inhibition of irrelevant information is thought to be associated with the psychotic symptoms in schizophrenia. Negative priming (NP) paradigm is believed to measure this impairment. Several studies have shown impaired NP in schizophrenia. In the present study a spatial NP task was used to assess attentional inhibition in a group of amphetamine-induced psychosis patients. Nineteen patients with amphetamine-induced psychotic disorder and 20 healthy subjects participated in this study. Severity of psychotic symptoms was measured prior to testing using the Brief Psychiatric Rating Scale (BPRS). Patients showed no deficit in NP, and the amount of their NP effect was not significantly different from healthy subjects. Besides, we did not find any correlation between the amount of NP effect and severity of symptoms. Our results may indicate that cognitive mechanisms underlying NP might not be affected in amphetamine psychosis.

Computational modeling of the negative priming effect based on inhibition patterns and working memory

Negative priming (NP), slowing down of the response for target stimuli that have been previously exposed, but ignored, has been reported in multiple psychological paradigms including the Stroop task. Although NP likely results from the interplay of selective attention, episodic memory retrieval, working memory, and inhibition mechanisms, a comprehensive theoretical account of NP is currently unavailable. This lacuna may result from the complexity of stimuli combinations in NP. Thus, we aimed to investigate the presence of different degrees of the NP effect according to prime-probe combinations within a classic Stroop task. We recorded reaction times (RTs) from 66 healthy participants during Stroop task performance and examined three different NP subtypes, defined according to the type of the Stroop probe in prime-probe pairs. Our findings show significant RT differences among NP subtypes that are putatively due to the presence of differential disinhibition, i.e., release from inhibition. Among the several potential origins for differential subtypes of NP, we investigated the involvement of selective attention and/or working memory using a parallel distributed processing (PDP) model (employing selective attention only) and a modified PDP model with working memory (PDP-WM, employing both selective attention and working memory). Our findings demonstrate that, unlike the conventional PDP model, the PDP-WM successfully simulates different levels of NP effects that closely follow the behavioral data. This outcome suggests that working memory engages in the re-accumulation of the evidence for target response and induces differential NP effects. Our computational model complements earlier efforts and may pave the road to further insights into an integrated theoretical account of complex NP effects.

Neural correlate of impulsivity in subjects at ultra-high risk for psychosis

OBJECTIVE

Impulsivity is one of the most commonly reported behavioral characteristics of patients with schizophrenia. Although there is accumulating evidence regarding behavioral problems in individuals at ultra-high risk (UHR) for psychosis, as yet, no study has reported on impulsivity in this population. The aim of the present study was to assess impulsivity in UHR subjects and to investigate the associated gray matter correlates.

METHOD

This study included 32 UHR subjects and 32 age- and gender-matched healthy controls (HCs). The Barratt Impulsiveness Scale version-11 (BIS-11) was employed to assess impulsivity. Differences between the groups in gray matter volume in the anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC), and orbitofrontal cortex (OFC) were assessed. Then, a correlational analysis between the BIS-11 scores and significant clusters of gray matter volume was conducted in UHR subjects.

RESULTS

UHR subjects were more impulsive than HC subjects in terms of attention (t = 3.5187, p<0.01), motor (t = 3.1751, p<0.01), and non-planning (t = 4.4154, p<0.01) scores. The gray matter volume of the ACC was negatively correlated with the motor (r = -0.472, p<0.01) and non-planning (r = -0.354, p = 0.04) scores of the BIS-11 in UHR subjects.

CONCLUSION

These results suggest that impulsivity in UHR subjects may reflect altered integrated conflict processing, which likely stems from abnormalities in the ACC, rather than altered reward/punishment processing or executive control.

Intranasal oxytocin impedes the ability to ignore task-irrelevant facial expressions of sadness in students with depressive symptoms

The administration of oxytocin promotes prosocial behavior in humans. The mechanism by which this occurs is unknown, but it likely involves changes in social information processing. In a randomized placebo-controlled study, we examined the influence of intranasal oxytocin and placebo on the interference control component of inhibition (i.e. ability to ignore task-irrelevant information) in 102 participants using a negative affective priming task with sad, angry, and happy faces. In this task, participants are instructed to respond to a facial expression of emotion while simultaneously ignoring another emotional face. On the subsequent trial, the previously-ignored emotional valence may become the emotional valence of the target face. Inhibition is operationalized as the differential delay between responding to a previously-ignored emotional valence and responding to an emotional valence unrelated to the previous one. Although no main effect of drug administration on inhibition was observed, a drug × depressive symptom interaction (β = -0.25; t = -2.6, p < 0.05) predicted the inhibition of sad faces. Relative to placebo, participants with high depression scores who were administered oxytocin were unable to inhibit the processing of sad faces. There was no relationship between drug administration and inhibition among those with low depression scores. These findings are consistent with increasing evidence that oxytocin alters social information processing in ways that have both positive and negative social outcomes. Because elevated depression scores are associated with an increased risk for major depressive disorder, difficulties inhibiting mood-congruent stimuli following oxytocin administration may be associated with risk for depression.

The National Alliance for Medical Image Computing, a roadmap initiative to build a free and open source software infrastructure for translational research in medical image analysis

The National Alliance for Medical Image Computing (NA-MIC), is a multi-institutional, interdisciplinary community of researchers, who share the recognition that modern health care demands improved technologies to ease suffering and prolong productive life. Organized under the National Centers for Biomedical Computing 7 years ago, the mission of NA-MIC is to implement a robust and flexible open-source infrastructure for developing and applying advanced imaging technologies across a range of important biomedical research disciplines. A measure of its success, NA-MIC is now applying this technology to diseases that have immense impact on the duration and quality of life: cancer, heart disease, trauma, and degenerative genetic diseases. The targets of this technology range from group comparisons to subject-specific analysis.

Characterization of groups using composite kernels and multi-source fMRI analysis data: application to schizophrenia

Pattern classification of brain imaging data can enable the automatic detection of differences in cognitive processes of specific groups of interest. Furthermore, it can also give neuroanatomical information related to the regions of the brain that are most relevant to detect these differences by means of feature selection procedures, which are also well-suited to deal with the high dimensionality of brain imaging data. This work proposes the application of recursive feature elimination using a machine learning algorithm based on composite kernels to the classification of healthy controls and patients with schizophrenia. This framework, which evaluates nonlinear relationships between voxels, analyzes whole-brain fMRI data from an auditory task experiment that is segmented into anatomical regions and recursively eliminates the uninformative ones based on their relevance estimates, thus yielding the set of most discriminative brain areas for group classification. The collected data was processed using two analysis methods: the general linear model (GLM) and independent component analysis (ICA). GLM spatial maps as well as ICA temporal lobe and default mode component maps were then input to the classifier. A mean classification accuracy of up to 95% estimated with a leave-two-out cross-validation procedure was achieved by doing multi-source data classification. In addition, it is shown that the classification accuracy rate obtained by using multi-source data surpasses that reached by using single-source data, hence showing that this algorithm takes advantage of the complimentary nature of GLM and ICA.

Altered patterns of cortical activation in ALS patients during attention and cognitive response inhibition tasks

Since amyotrophic lateral sclerosis (ALS) can be accompanied by executive dysfunction, it is hypothesised that ALS patients will have impaired performance on tests of cognitive inhibition. We predicted that ALS patients would show patterns of abnormal activation in extramotor regions when performing tests requiring the inhibition of prepotent responses (the Stroop effect) and the inhibition of prior negatively primed responses (the negative priming effect) when compared to healthy controls. Functional magnetic resonance imaging was used to measure activation during a sparse sequence block design paradigm investigating the Stroop and negative priming effects in 14 ALS patients and 8 healthy age- and IQ-matched controls. Behavioural measures of performance were collected. Both groups' reaction times (RTs) reflected the Stroop effect during scanning. The ALS and control groups did not differ significantly for any of the behavioural measures but did show significant differences in cerebral activation during both tasks. The ALS group showed increased activation predominantly in the left middle temporal gyrus (BA 20/21), left superior temporal gyrus (BA 22) and left anterior cingulate gyrus (BA 32). Neither group's RT data showed clear evidence of a negative priming effect. However the ALS group showed decreased activation, relative to controls, particularly in the left cingulate gyrus (BA 23/24), left precentral gyrus (BA 4/6) and left medial frontal gyrus (BA 6). Greater cerebral activation in the ALS group accompanying the performance of the Stroop effect and areas of decreased activation during the negative priming comparison suggest altered inhibitory processing in ALS, consistent with other evidence of executive dysfunction in ALS. The current findings require further exploration in a larger study.