Biomedical subjects

Kristin R Laurens

Publications and source records attributed to Kristin R Laurens.

11 recordsLinked to original sources

PubMed2007

Community screening for psychotic-like experiences and other putative antecedents of schizophrenia in children aged 9-12 years.

Prospective longitudinal investigations are needed to identify causal processes leading to schizophrenia. However, there is presently no cost-effective way to identify children who are at risk of developing schizophrenia spectrum disorders: Although having a family history of schizophrenia is associated with elevated risk for developing spectrum disorders, the majority of individuals with schizophrenia do not have an afflicted relative. The present study aimed to test the feasibility of screening a community sample of children, aged 9 to 12 years, to identify children who experienced a triad of putative antecedents of schizophrenia that had been identified from previous research, including: (1) speech and/or motor development lags or problems; (2) social, emotional, or behavioural problems; and (3) psychotic-like-experiences (PLEs). 548 children and 264 caregivers completed questionnaires. 9.2% of boys and 4.1% of girls displayed the triad of antecedents. 58.9% of the children reported "certain experience" of one or more PLEs. The results suggest that questionnaire screening of community samples of children for the putative antecedents of schizophrenia spectrum disorders is feasible. Accuracy of identification will only be established by follow-up studies.

Child↗

PubMed2006

Abnormal function of the brain system supporting motivated attention in medicated patients with schizophrenia: an fMRI study.

BACKGROUND: Patients with schizophrenia have an impaired ability to generate activity that is appropriate to current circumstances and goals. METHOD: We report a study using functional magnetic resonance imaging (fMRI) to examine cerebral activity during a three-tone auditory oddball target detection task in a sample of 28 patients with schizophrenia and 28 healthy controls. RESULTS: The patients exhibited significantly less activation in response to target stimuli relative to baseline in an extensive set of sites in association neocortex, paralimbic cortex, limbic structures and subcortical nuclei, yet demonstrated a normal level of activation in the sensorimotor cortex. Comparison of activity elicited by rare target stimuli with that elicited by equally rare novel stimuli makes it possible to distinguish cerebral activity associated with attention to behaviourally salient stimuli from activity associated with attending to other attention-capturing stimuli. This comparison revealed that the patients with schizophrenia also exhibited a deficit in activation of basal forebrain areas that mediate motivation during the processing of behaviourally salient stimuli, including the amygdala, ventral striatum, orbital frontal cortex and rostral anterior cingulate cortex. CONCLUSION: Patients with schizophrenia have a deficit in function of the brain system concerned with mediating motivation, in addition to a more general deficit in the cerebral response to attention-captivating stimuli.

Acoustic Stimulation↗

PubMed2006

Brain potentials implicate temporal lobe abnormalities in criminal psychopaths.

Psychopathy is associated with abnormalities in attention and orienting. However, few studies have examined the neural systems underlying these processes. To address this issue, the authors recorded event-related potentials (ERPs) while 80 incarcerated men, classified as psychopathic or nonpsychopathic via the Hare Psychopathy Checklist--Revised (R. D. Hare, 1991, 2003), completed an auditory oddball task. Consistent with hypotheses, processing of targets elicited larger frontocentral negativities (N550) in psychopaths than in nonpsychopaths. Psychopaths also showed an enlarged N2 and reduced P3 during target detection. Similar ERP modulations have been reported in patients with amygdala and temporal lobe damage. The data are interpreted as supporting the hypothesis that psychopathy may be related to dysfunction of the paralimbic system--a system that includes parts of the temporal and frontal lobes.

Adult↗

PubMed2005

The hemodynamics of oddball processing during single-tone and two-tone target detection tasks.

Event-related potential (ERP) studies have shown that the neural systems engaged during performance of oddball tasks are sensitive to contextual manipulations, such as the number of stimulus classes. Some ERP components (i.e., N1) are modulated by the number of stimulus types, while others (i.e., P3) are not greatly affected. However, little is known about how these contextual manipulations affect the hemodynamics underlying oddball processing. The purpose of this study was to examine the hemodynamic correlates of target stimulus processing in single-tone (targets alone) and two-tone (targets and standard tones) auditory oddball tasks. The primary hypothesis was that processing of salient stimuli in both contextual conditions would engage the same spatially distributed cortical and subcortical networks observed in previous oddball fMRI studies. Results were consistent with this hypothesis and suggest that the brain engages many potentially useful brain regions during salient stimulus processing despite the low probability that said regions are necessary for task performance, which likely reflects a form of "adaptive reflexive processing". Results were also consistent with ERP data that shows that the N1 is larger for single-tone tasks by showing greater amplitude of hemodynamic response for single-tone targets, relative to two-tone targets, in bilateral temporal cortex and bilateral inferior lateral frontal cortex. The results are discussed as they relate to the understanding of neurocognitive function pertaining to contextual manipulations in general, and orienting processes in particular.

Acoustic Stimulation↗

PubMed2005

An adaptive reflexive processing model of neurocognitive function: supporting evidence from a large scale (n = 100) fMRI study of an auditory oddball task.

Recent hemodynamic imaging studies have shown that processing of low probability task-relevant target stimuli (i.e., oddballs) and low probability task-irrelevant novel stimuli elicit widespread activity in diverse, spatially distributed cortical and subcortical systems. The nature of this distributed response supports the model that processing of salient and novel stimuli engages many brain regions regardless of whether said regions were necessary for task performance. However, these latter neuroimaging studies largely employed small sample sizes and fixed-effect analyses, limiting the characterization and inference of the results. The present study addressed these issues by collecting a large sample size (n = 100) and employed random effects statistical models. Analyses were also conducted to determine the inter-subject reliability of the hemodynamic response and the effects of gender and age on target detection and novelty processing. Group data demonstrated highly significant activation in all 34 specified regions of interest for target detection and all 24 specified regions of interest for processing of novel stimuli. Neither age nor gender systematically influenced the results. These data are discussed within the context of a model that proposes that the mammalian brain has evolved to adopt a strategy of engaging distributed neuronal systems when processing salient stimuli despite the low probability that many of these brain regions are required for successful task performance. This process may be termed 'adaptive reflexive processing.' The implications of these results for interpreting functional MRI studies are discussed.

Adolescent↗

PubMed2005

Attention orienting dysfunction during salient novel stimulus processing in schizophrenia.

Schizophrenia is characterised by marked disturbances of attention and information processing. Patients experience difficulty focusing on relevant cues and avoiding distraction by irrelevant stimuli. Event-related potential recordings indicate an amplitude reduction in the P3a component elicited by involuntary orienting to task-irrelevant, infrequent novel stimuli presented during auditory oddball detection in patients with schizophrenia. The goal of the present study was to elucidate the functional abnormality underlying the disturbed orienting to novel stimuli in schizophrenia. Twenty-eight stable, partially remitted, medicated patients with schizophrenia and 28 healthy control participants completed a novelty oddball variant during event-related fMRI. Relative to healthy participants, patients with schizophrenia were characterised by underactivity during novel stimulus processing in the right amygdala-hippocampus, within paralimbic cortex in the rostral anterior cingulate and posterior cingulate cortices and the right frontal operculum, and in association cortex at the right temporo-parietal-occipital junction, bilateral intraparietal sulcus, and bilateral dorsal frontal cortex. Subcortically, relative hypoactivation during novelty processing was apparent in the cerebellum, thalamus, and basal ganglia. These results suggest that patients less efficiently reorient processing resources away from the ongoing task of detecting and responding to the task-relevant target stimuli. In addition, trend results suggest that patients experienced increased distraction by novel stimuli.

Amygdala↗

PubMed2005

A supramodal limbic-paralimbic-neocortical network supports goal-directed stimulus processing.

Limited processing resources are allocated preferentially to events that are relevant for behavior. Research using the novelty "oddball" paradigm suggests that a widespread network of limbic, paralimbic, and association areas supports the goal-directed processing of task-relevant target events. In that paradigm, greater activity in diverse brain areas is elicited by rare task-relevant events that require a subsequent motor response than by rare task-irrelevant novel events that require no response. Both stimulus infrequency (unexpectedness) and novelty, however, may contribute to the pattern of activity observed using that paradigm. The goal of the present study was to examine the supramodal neural activity elicited by regularly occurring, equiprobable, and non-novel stimuli that differed in the subsequent behavior they prescribed. We employed event-related functional magnetic resonance imaging (fMRI) during auditory and visual versions of a Go/NoGo task. Participants made a motor response to the designated "Go" (target) stimulus, and no motor response to the equiprobable "NoGo" (nontarget) stimulus. We hypothesized that task-relevant Go events would elicit relatively greater hemodynamic activity than would NoGo events throughout a network of limbic, paralimbic, and association areas. Indeed, Go events elicited greater activity than did NoGo events in the amygdala-hippocampus, paralimbic cortex at the anterior superior temporal sulcus, insula, posterior orbitofrontal cortex, and anterior and posterior cingulate cortex, as well as in heteromodal association areas located at the temporoparietal junction, anterior intraparietal sulcus and precuneus, and premotor cortex. Paralimbic cortex offers an important site for the convergence of motivational/goal-directed influences from limbic cortex with stimulus processing and response selection mediated within the frontoparietal areas.

Acoustic Stimulation↗

PubMed2003

Abnormal processing of speech during oddball target detection in schizophrenia.

Healthy subjects show increased activation in left temporal lobe regions in response to speech sounds compared to complex nonspeech sounds. Abnormal lateralization of speech-processing regions in the temporal lobes has been posited to be a cardinal feature of schizophrenia. Event-related fMRI was used to test the hypothesis that schizophrenic patients would show an abnormal pattern of hemispheric lateralization when detecting speech compared with complex nonspeech sounds in an auditory oddball target-detection task. We predicted that differential activation for speech in the vicinity of the superior temporal sulcus would be greater in schizophrenic patients than in healthy subjects in the right hemisphere, but less in patients than in healthy subjects in the left hemisphere. Fourteen patients with schizophrenia (selected from an outpatient population, 2 females, 12 males, mean age 35.1 years) and 29 healthy subjects (8 females, 21 males, mean age 29.3 years) were scanned while they performed an auditory oddball task in which the oddball stimuli were either speech sounds or complex nonspeech sounds. Compared to controls, individuals with schizophrenia showed greater differential activation between speech and nonspeech in right temporal cortex, left superior frontal cortex, and the left temporal-parietal junction. The magnitude of the difference in the left temporal parietal junction was significantly correlated with severity of disorganized thinking. This study supports the hypothesis that aberrant functional lateralization of speech processing is an underlying feature of schizophrenia and suggests the magnitude of the disturbance in speech-processing circuits may be associated with severity of disorganized thinking.

Adult↗

PubMed2003

Rostral anterior cingulate cortex dysfunction during error processing in schizophrenia.

Previous research has demonstrated that patients with schizophrenia have an impaired ability to monitor erroneous responses to stimuli internally. Event-related potential (ERP) studies of error-eliciting tasks indicate that, in healthy adults, the commission of an erroneous response is associated with a fronto-centrally distributed negative voltage component termed the error negativity (Ne) or error-related negativity (ERN). In patients with schizophrenia, the Ne/ERN elicited by errors of commission (EoC) is reduced in amplitude compared with that elicited in healthy participants. Functional MRI (fMRI) studies and source localization analyses of ERP data in healthy participants suggest that EoC are associated with activity in the rostral anterior cingulate cortex (ACC). Using event-related fMRI, we examined the brain activity associated with EoC in a group of 10 patients with schizophrenia and 16 matched healthy participants. Patients were stable, partially remitted, medicated out-patients recruited from the community. Participants performed a Go/NoGo task variant that was shown previously to elicit a reduced Ne/ERN during EoC in patients with schizophrenia relative to healthy participants, as well as robust rostral ACC activation during EoC in healthy participants. Patients with schizophrenia were characterized by relative underactivity in the rostral ACC compared with healthy participants. There was also evidence for more widespread underactivity in the limbic system. In contrast to these regions of relative hypoactivity, patients with schizophrenia demonstrated hyperactivity relative to healthy participants in bilateral parietal cortex during both EoC and correctly rejected NoGo trials. Our results are consistent with previous ERP research demonstrating functional abnormalities during error processing in schizophrenia. In light of the role of the rostral ACC and other limbic structures in mediating affective and motivational behaviour, our results suggest there may be a disturbed affective or motivational response to the commission of errors in schizophrenia.

Adult↗

PubMed2002

Error-related negativity and correct response negativity in schizophrenia.

OBJECTIVES: To examine error-related negativity (ERN) and correct response negativity (CRN) in schizophrenia in light of two previous conflicting reports, and to determine their relation to disorganization, psychomotor poverty and reality distortion. METHODS: Event-related potentials were recorded from 21 schizophrenic and 21 control participants who performed a simple go/no-go task. Response-locked potentials were computed for errors of commission and for correct-hits. Scores for reality distortion syndrome, psychomotor poverty syndrome and disorganization syndrome were determined for each schizophrenic participant using the Signs and Symptoms of Psychotic Illness (SSPI) scale. RESULTS: ERN produced during error trials and CRN produced during correct trials were significantly larger in the control participant group than in the schizophrenic participant group. In the schizophrenic patients, ERN amplitude was negatively correlated with psychomotor poverty syndrome score and CRN amplitude was negatively correlated with disorganization syndrome score. CONCLUSIONS: Decreased ERN and CRN in the schizophrenic participant group suggests abnormal internal behavior monitoring in schizophrenic patients. Patients with high disorganization symptoms may employ an abnormal strategy for comparing actual response outcome with desired response outcome, while patients with psychomotor poverty may be less emotionally responsive to errors.

Adolescent↗

PubMed2002

Reading anomalous sentences: an event-related fMRI study of semantic processing.

We report a random-effects analysis of an event-related fMRI study (n = 28) of cerebral activity during the reading of sentences that ended with a word that was either congruent or incongruent with the previous sentence context. Event-related potential studies have shown that this task elicits a late negativity peaking around 400 ms poststimulus (N400) that is larger for incongruent than for congruent sentence endings. A direct comparison of the activation for incongruent words versus that for congruent words revealed significantly greater activation for incongruent words than congruent words in bilateral inferior frontal and inferio-medial temporal cortex, left lateral frontal cortex, left posterior fusiform gyrus, bilateral motor cortex, and supplementary motor area. These results are consistent with data from intracranial electrical recording studies of the N400 electrical potential. The results are discussed as they relate to the localization of the cerebral sites underlying semantic processing in general and the localization of the scalp recorded N400 event-related potential in particular.

Adult↗