Latent inhibition,learned irrelevance,and schizotypy: Assessing their relationship

Introduction. Previous research suggests that latent inhibition is reduced in patients with acute schizophrenia and in healthy participants with high levels of schizotypic characteristics. Other evidence indicates the disruption of a related effect (learned irrelevance) in patients with acute schizophrenia.

Method. This study used a recently developed latent inhibition procedure, that avoids methodological limitations of previous studies, and a related learned irrelevance procedure to assess the relationship between these phenomena and schizotypic characteristics in undergraduate participants.

Results. Participants preexposed to a letter (S) learnt the predictive relationship between that letter and another letter (X) slower than the relationship between a novel letter and X (a latent inhibition effect). Experiment 1 found reduced latent inhibition in the high schizotypy group after 10, but not 20 preexposures. In Experiment 2, participants preexposed to both S and X learnt a subsequent relationship between them slower than the relationship between a novel letter and X (a learned irrelevance effect). This effect was abolished in participants with high levels of schizotypy.

Conclusions. These results are both the first demonstration of abolished learned irrelevance and of a significant reduction in latent inhibition without employing an explicit masking task in participants with high levels of positive schizotypy.     

Cognitive functioning in schizotypy through the lens of the accessibility model

Introduction: Individuals with schizotypy self-report subjective cognitive complaints commensurate with deficits reported by individuals with schizophrenia. In contrast to schizophrenia, objective deficits in memory are modest in individuals with schizotypy, as compared to their self-reported cognitive complaints. It has been proposed that abnormalities in semantic memory systems may underlie this dysjunction.

Methods: This study employed a modified verbal memory paradigm in a sample of 87 individuals with psychometrically defined schizotypy. Appraisals of memory performance were evaluated across global (i.e. drawing on semantic memory systems and assessing perceived typical performance) and situation-specific (i.e. drawing on episodic memory systems) epochs. Objective memory performance was assessed using a verbal recall paradigm.

Results: Individuals with schizotypy did not differ in situation-specific appraisals or in objective memory performance. Global appraisals of memory performance predicted negative and disorganised schizotypy scores. No other measure of memory performance predicted any facet of schizotypy. Individuals with schizotypy appraised their global memory performance higher than controls at a medium effect.

Conclusions: Higher order global appraisals of cognitive performance, subsumed within semantic networks, may be important in the subjective–objective paradox in schizotypy, suggesting the importance of considering demand characteristics when assessing measures of neurocognitive performance in individuals with schizotypy.     

Pupillary responses and attentional allocation problems on the backward masking task in schizophrenia.

Early visual information processing impairment has consistently been found on the backward masking task in patients with schizophrenia, but the nature of this impairment remains unclear. Pupillometry was used to measure attentional allocation during visual backward masking task performance in patients with schizophrenia (n=16) and nonpsychiatric controls (n=16). The extent of pupil dilation recorded during a cognitive task reflects the processing load placed on the nervous system by the task. Schizophrenia patients detected significantly fewer targets than controls only when the stimulus onset asynchrony (SOA) between targets and masks reached 317 ms. For both groups, peak pupil dilation responses were also significantly larger in the 317 ms SOA condition relative to a no-mask condition, suggesting that the processing load of the 317 SOA masking condition was greater than the no-mask condition. In addition, a principal components analysis of pupillary response waveforms identified time-related factors that appeared to differentially index attentional allocation to targets vs. masks. Patients with schizophrenia showed less dilation than controls on a middle factor that appeared to index attentional allocation to targets, but patients showed greater dilation than controls on a late factor that appeared to index attentional allocation to masks. That is, controls attended more to targets than to masks, but patients attended more to masks than to targets. These findings suggest that masking impairments at SOA intervals greater than 100-200 ms may be due abnormalities in attentional allocation mechanisms.     

High and low schizotypal female subjects do not differ in spatial memory abilities in a virtual reality task

Introduction. Schizotypy is a psychological construct related to schizophrenia. The exact relationship between both entities is not clear. In recent years, schizophrenia has been associated with hippocampal abnormalities and spatial memory problems. The aim of this study was to determine possible links between high schizotypy (HS) and low schizotypy (LS) and spatial abilities, using virtual reality tasks. We hypothesised that the HS group would exhibit a lower performance in spatial memory tasks than the LS group.

Methods. Two groups of female students were formed according to their score on the ESQUIZO-Q-A questionnaire. HS and LS subjects were tested on two different tasks: the Boxes Room task, a spatial memory task sensitive to hippocampal alterations and a spatial recognition task.

Results. Data showed that both groups mastered both tasks. Groups differed in personality features but not in spatial performance. These results provide valuable information about the schizotypy–schizophrenia connections.

Conclusion. Schizotypal subjects are not impaired on spatial cognition and, accordingly, the schizotypy–schizophrenia relationship is not straightforward.     

Discriminating between first- and second-order cognition in first-episode paranoid schizophrenia*

Introduction: An impairment of visually perceiving backward masked stimuli is commonly observed in patients with schizophrenia, yet it is unclear whether this impairment is the result of a deficiency in first or higher order processing and for which subtypes of schizophrenia it is present.

Methods: Here, we compare identification (first order) and metacognitive (higher order) performance in a visual masking paradigm between a highly homogenous group of young first-episode patients diagnosed with paranoid schizophrenia (N?=?11) to that of carefully matched healthy controls (N?=?13).

Results: We find no difference across groups in first-order performance, but find a difference in metacognitive performance, particularly for stimuli with relatively high visibility.

Conclusions: These results indicate that the masking deficit is present in first-episode patients with paranoid schizophrenia, but that it is primarily an impairment of metacognition.     

Altered depth perception is associated with presence of schizotypal personality traits

Introduction. Impaired depth perception, a fundamental aspect of early visual processing, has been shown in patients with schizophrenia suggesting a disturbance to magnocellular and possibly parvocellular pathways. Despite some evidence showing visual-perceptive deficits in people with schizotypal personality traits (SPT), depth perception has not been evaluated in these subjects.

Methods. 12 clinically healthy schizotypy and 17 control participants were examined using a novel stereoscopic depth perception task. A mixed ANOVA design considered the Group (SPT/control) as independent factor, and trial Block (BD/BD + /BD–) and target Condition (SDSS/SDDS/DDSS/DDDS) were considered as repeated measures.

Results. Schizotypal participants were not significantly different to controls on simple judgements of depth but demonstrated a subtle impairment in perceiving binocular depth when performing high difficulty judgements.

Conclusions. The presence of subtle depth perception problems in schizotypal subjects, similar but less marked than those of schizophrenia patients, may suggest a less pervasive disturbance of early information processing. If so, such deficits could be considered as innate neurological changes that may occur in people vulnerable for schizophrenia, thus with the potential to be a novel intermediate phenotype.     

Dissection of Schizotypy and Dissociation in Depersonalization Disorder

ABSTRACT

The relationship between dissociation and psychosis-proneness remains controversial to this day. We investigated this relationship in Depersonalization Disorder, a primary dissociative disorder, hypothesizing that the constructs of schizotypy and dissociation would be distinguishable. Forty-eight depersonalization disorder (DPD) and 22 healthy comparison (HC) participants were administered measures of schizotypy (Perceptual Aberration Scale, Magical Ideation Scale) and dissociation (Dissociative Experiences Scale). The DPD group had significantly higher schizotypy scores than the HC group. However, when DPD participants with Axis II disorders were excluded, the remaining “pure” DPD group (N = 22) exhibited higher perceptual aberrations but comparable magical ideations to the healthy group. Within the “pure” DPD group, dissociation and schizotypy scores were not significantly correlated. We conclude that schizotypy was readily distinguishable from dissociation in the current sample. Greater attention to methodological issues promoting the distinction between dissociation and schizotypy may prove helpful in future phenomenological research.     

Is the odour identification deficit in schizophrenia influenced by odour hedonics?

Introduction. While smell identification deficits have been well documented in schizophrenia, less work has examined identification accuracy for pleasant and unpleasant odours. The current investigation examined odour identification performance for pleasant and unpleasant odours in a sample of inpatients with schizophrenia and nonpsychiatric community controls.

Method. The Brief Smell Identification Test was used to investigate accuracy in the identification of pleasant and unpleasant odours in 23 schizophrenia inpatients and 21 nonpsychiatric controls.

Results. Results revealed that schizophrenia patients showed reduced accuracy on pleasant odours, but intact performance for unpleasant odours.

Conclusions. Results provide preliminary support for a specific deficit in identifying pleasant odours in patients with schizophrenia. Future studies separating odours by valence categories are warranted.     

Forward and backward visual masking in schizophrenia: influence of age

BACKGROUND: Visual masking tasks assess the earliest stages of visual processing. This study was conducted to address: (1) whether schizophrenia patients show masking deficits after controlling for sensory input factors; (2) whether patients have relatively intact forward masking (when the mask precedes the target) compared with backward masking (when the mask follows the target); and (3) whether the masking deficits in schizophrenia reflect an accelerated age-related decline in performance. METHOD: A staircase method was used to ensure that the unmasked target identification was equivalent across subjects to eliminate any confounding due to differences in discrimination of simple perceptual inputs. Three computerized visual masking tasks were administered to 120 schizophrenia patients (ages 18-56) and 55 normal comparison subjects (ages 19-54) under both forward and backward masking conditions. The tasks included: (1) locating a target; (2) identifying a target with a high-energy mask; and (3) identifying a target with a low-energy mask. RESULTS: Patients showed deficits across all three masking tasks. Interactions of group by forward versus backward masking were not significant, suggesting that deficits in forward and backward masking were comparable. All three conditions showed an age-related decline in performance and rates of decline were comparable between patients and controls. Two of the masking conditions showed increased rates of decline in backward, compared to forward, masking. CONCLUSIONS: We found age-related decline in performance that was comparable for the two groups. In addition, we failed to find evidence of a relative sparing of forward masking in schizophrenia. These results suggest that: (1) early visual processing deficits in schizophrenia are not due to a simple perceptual input problem; (2) sustained channels are involved in the masking deficit (in addition to transient channels); and (3) for the age range in this study, these deficits in schizophrenia are not age-related.     

Category fluency in psychometric schizotypy: how altering emotional valence and cognitive load affects performance

Introduction. In clinical high-risk populations, category fluency deficits are associated with conversion to psychosis. However, their utility as clinical risk markers is unclear in psychometric schizotypy, a group experiencing schizophrenia-like traits that is at putative high risk for psychosis.

Methods. We examined whether introducing affective or cognitive load, two important stress vulnerability markers, altered category fluency performance in schizotypy (n?=?42) and non-schizotypy (n?=?38) groups. To investigate this question, we developed an experimental paradigm where all participants were administered category fluency tests across baseline, pleasant valence, unpleasant valence, and cognitive load conditions.

Results. Compared to the non-schizotypy group, those with schizotypy performed significantly worse in pleasant and unpleasant valence conditions, but not cognitive load or baseline fluency tests.

Conclusions. This study demonstrated the role of affect – but not cognitive load – on category fluency in psychometric schizotypy, as group differences only emerged once affective load was introduced. One explanation for this finding is that semantic memory may be unimpaired under normal conditions in psychometric schizotypy, but may be compromised once affective load is presented. Future studies should examine whether fluency deficits – particularly when affect is induced – predict future conversion to psychosis in psychometric schizotypy cohorts.     

AERs and Detection in Tasks Yielding U-Shaped Backward Masking Functions

In backward masking, psychophysical performance varies as a function of the interval between target and mask (stimulus onset asynchrony—SOA). Early studies of averaged evoked responses (AERs) and backward masking suggested a close, monotonic relationship, i.e., increasing psychophysical performance accompanied by increasingly larger AERs as a function of SOA. We asked what would happen to AERs if the perceptual task were designed to produce a U-shaped performance function, i.e., one in which performance initially decreased and then increased as a function of SOA? In two experiments U-shaped psychophysical performance was accompanied by monotonic AER functions. In a third experiment, comparing backward and forward masking at comparable SOAs, disparate psychophysical performances were obtained from the same subjects accompanied by similar AERs. Target AERs do not necessarily correlate with a subject's behavioral performance.     

Effects of neurocognitive enhancement therapy in schizophrenia: Normalisation of memory performance

Introduction. A preponderance of research indicates that cognitive function in schizophrenia can be improved through cognitive remediation. However, few studies have attempted to characterise the extent of improvement relative to nonpsychiatric controls.

Method. Cognitive performance on reaction time, digit recall, and word recall of 58 schizophrenia patients at baseline and after 6 months of cognitive remediation was compared to the performance on these tasks of 39 community controls. Schizophrenia patients participated in Neurocognitive Enhancement Therapy (NET) and received hierarchical training on the memory tasks, but not on the reaction time task, which was only administered at intake and follow‐up.

Results. The schizophrenia sample showed significantly poorer performances than the community control sample on all three tasks at baseline. NET led to significant improvements in performance on trained memory tasks, but not the untrained reaction time task. There was a significant increase in the proportion of schizophrenia patients who achieved normal range performance on the memory tasks.

Conclusions. 52% of schizophrenia patients who were impaired on at least one of the memory tasks normalised their performance on at least one of those tasks as a result of cognitive training. Results suggest that clinically meaningful improvement may be possible using cognitive remediation.     

Can individuals with schizophrenia be instructed to deliberately feign memory deficits?

Introduction. Neuropsychological tests are increasingly applied in research studies and clinical practice in psychiatry. In this context, the detection of poor effort is crucial to adequately interpret data. We measured schizophrenia patients' performance on a memory test designed to detect excessive malingering (the “21-Item Test”), before examining whether a second group of schizophrenia patients would excessively malinger on this test when given an incentive to feign memory impairment.

Methods. Two independent studies including respectively 49 schizophrenia patients and 100 controls (study 1) and 25 schizophrenia patients and 25 controls (study 2) were conducted. In study 1, participants were asked to complete the 21-Item Test to the best of their ability. In study 2, participants were given a hypothetical scenario in which having a memory impairment would be financially advantageous for them, before completing the 21-Item Test.

Results. In study 1, no participant scored at levels indicative of excessive malingering. In study 2, 84% of controls but only 36% of patients scored at excessive levels of malingering, and these patients had higher executive functioning than patients who did not excessively malinger, although it should be noted that a significantly greater proportion of patients excessively malingered in study 2 compared to study 1.

Conclusions. These results indicate that schizophrenia patients do not normally feign excessive memory impairment during psychological testing. Furthermore, they are less able and/or less inclined to excessively malinger than controls in situations where a memory impairment would be advantageous, perhaps indicating a better ability to malinger without detection. Potential clinical implications are discussed.     

Alignment and theory of mind in schizophrenia

Introduction. We predicted that participants with schizophrenia would be able to successfully “align” during conversation in the context of impaired theory of mind. Alignment is a process by which interlocutors’ representations of the conversational situation converge; and it may, in part, explain how people with schizophrenia can often participate successfully in dialogue despite experiencing impaired mentalising.

Methods. Fifty-nine people with schizophrenia and 38 healthy adults completed a standardised, empirical conversational alignment task with a mentalising component and a measure of current IQ. The patients also completed two independent theory of mind tests. We used ANCOVAs to compare the groups’ performances.

Results. The participants with schizophrenia and the healthy participants demonstrated equivalent alignment skills even though the schizophrenia participants displayed clear theory of mind difficulties. Symptom subtype analyses found no differences between subtype groups in alignment, but healthy controls and remitted patients performed significantly better on the mentalising component than the paranoia group.

Conclusions. These results are consistent with the schizophrenia participants having intact alignment skills alongside mentalising impairments. We propose that this explains why people with schizophrenia can often participate successfully in conversation but have difficulties with more complex dialogues, with resolving misunderstandings, and with untangling ambiguities during conversation.     

Empathy,schizotypy, and visuospatial transformations

Introduction. Adopting another person's visuospatial perspective has been associated with empathy, which involves adopting the psychological perspective of another individual. Both reduced empathy and abnormal visuospatial processing have been observed in those with schizophrenia and schizophrenia-related personality traits. In the current study, we sought to explore the relationship between empathy, schizotypy, and visuospatial transformation ability.

Methods. 32 subjects (16 women) performed a visuospatial perspective-taking task and a mental letter rotation task. Response times and accuracy were analysed in relation to dimensions of self-reported empathy, indexed using the Interpersonal Reactivity Index, and schizotypy, as measured by the Schizotypal Personality Questionnaire.

Results. We found that: (1) greater cognitive and affective empathy were associated with reduced negative schizotypy, and, in men, greater cognitive empathy was associated with reduced positive schizotypy; (2) improved accuracy for imagined self–other transformations in the perspective-taking task was associated with greater self-reported cognitive empathy in women and higher positive schizotypy across genders; (3) faster mental letter rotation was associated with reduced cognitive empathy and increased negative schizotypy in women.

Conclusions. Together, the findings partially support the commonalities in visuospatial transformation ability, empathy, and schizotypy, and posit an interesting link between spatial manipulations of our internal representations and interactions with the physical world.     

Face perception in schizophrenia: a specific deficit

Introduction. Patients with schizophrenia have a large-scaled and severe cognitive impairment. This study examines whether a well-established deficit in face recognition in schizophrenia is a part of this general cognitive impairment or is specific to faces per se.

Method. The differential deficit in matching upright faces as compared with two psychometrically matched control tasks (matching inverted faces and matching none-face objects) was assessed in two well-matched samples of schizophrenics (n?=?40) and controls (n?=?40).

Results. Indicating a generalised cognitive deficit, schizophrenics were impaired in all tasks. Importantly, however, the deficit in matching upright faces was stronger in magnitude (15.6%) than the deficits in matching inverted faces (10.1%) and non-face objects (10.2%). Consistently, schizophrenics showed weaker face inversion effects, indicating a configural processing dysfunction.

Conclusion. These results provide compelling evidence for a face-specific deficit in schizophrenia that may be associated with, but separable from, a generalised cognitive impairment.     

Working memory and multidimensional schizotypy: dissociable influences of the different dimensions

Compromised working memory is considered a core deficit of schizophrenia and a potential endophenotype for the liability to develop schizophrenia. In keeping with this suggestion, working memory has also been found to be disrupted in people with high levels of schizotypy. However, it is unclear whether this disruption is linked to positive, negative, or disorganized symptoms/characteristics. This issue is the focus of the present investigation. The relationship between multidimensional schizotypy and working memory performance was investigated in 289 participants. Working memory was measured using an n-back task with three conditions; 0-back, 1-back, and 2-back. Covarying for the effect of shared variance between the schizotypy dimensions, we found reduced working memory performance in participants who displayed high levels of positive schizotypy and, to some extent, in participants with low levels of negative schizotypy. The results are discussed in terms of Baddeley's (1986) model of working memory and potential underlying neurological mechanisms.     

'Masked' Span of Apprehension in Schizophrenic Subgroups

Background. This study explored the possible impairment in inhibiting irrelevant stimuli (as reflected in the backward masking version of the forced-choice span of apprehension task) in subgroups of individuals with schizophrenia. Method. Subjects included 48 schizophrenics and 54 nonpsychiatric controls. Letter arrays were presented at three stimulus onset asynchronies (SOAs; 60, 100, 250msec) and three levels of complexity (3, 7, 11 distractor letters). Results. As a group, schizophrenics (n = 54) were impaired relative to nonpsychiatric controls (n = 48) for 7-distractor displays at 60msec and 250msec SOA. Cluster analysis of SAPS and SANS ratings produced four symptom subgroups. Opposing masking performances were found for Psychomotor Poverty (impaired for long SOAs) and Reality Distortion (enhanced at short SOAs) subgroups, whereas the Disorganisation subgroup was globally impaired, and the Episodic subgroup performed similarly overall to controls. Conclusion. The results highlight the potential importance of symptomatology in further elucidating the span of apprehension impairment in schizophrenia.     

A developmental look at the attentional system in the at risk and first episode of psychosis: Age related changes in attention along the psychosis spectrum

Introduction. Neurodevelopmental processes of adolescence, when superimposed on a vulnerable brain, may produce additive effects reflecting the subthreshold psychotic symptoms, cognitive, and functional deterioration that are the hallmark of the early stages of schizophrenia.

Methods. As part of a longitudinal study, we investigated Continuous Performance Task, Identical Pairs Version (CPT-IP) performance in a sample of 301 participants (at risk for psychosis: 109; first episode–FE: 90; and controls: 102). Performance across groups was compared using d' of fast and slow, spatial and verbal conditions over two time points. Age effects were investigated using a regression model.

Results. Across all four CPT-IP conditions FE patients performed significantly worse than controls while AR individuals significantly differed from healthy subjects in the verbal condition. Age-related performance associations across groups significantly differed in the slow verbal condition because the FE sample did not show a significant association with increasing age like the AR and NC samples. CPT performance was stable over time.

Conclusions. Sustained attention in the putative prodrome of psychosis is not only impaired but associated with age. Research focusing on cognitive and neurobiological age-related changes can help to address fundamental questions about the nature of the disorder, including whether the underlying pathophysiology of early psychosis is static or deteriorating.     

Impaired conscious memory in non-clinical schizotypy

Introduction. Impaired controlled and preserved/enhanced automatic memory processes have been reported in schizotypy. This memory pattern has been considered as a marker of vulnerability to schizophrenia. Our aim was to further explore this memory pattern in non-clinical schizotypy in order to determine which specific dimensions of schizotypy (i.e., positive, negative or disorganised), and more specifically which components of the dimensions, are most closely related to memory dysfunctions.

Methods. Fifty-seven undergraduate students performed a category-production task. This was adapted for use with the process dissociation procedure in order to dissociate between automatic and controlled memory processes. The level of schizotypy was assessed using the Schizotypal Personality Questionnaire.

Results. Regression analyses confirmed that controlled memory processes decreased as schizotypy increased. The positive factors (more specifically, the ideas of reference subscale) and disorganised factors (more specifically, the odd or eccentric behaviour subscale) were negatively correlated with the controlled memory processes.

Conclusions. Our study supports the idea that impaired controlled processes are an early cognitive marker of vulnerability to schizophrenia and confirm that the disorganised factor contributes the most to vulnerability to memory dysfunction. It also emphasises the importance of dissociating between each of the features characterising schizotypy rather than considering it as a whole.