Preattentional processes and disorganization in schizophrenia: Influence of a 6-week risperidone treatment

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.

"To see or not to see: that is the question." The "Protection-Against-Schizophrenia" (PaSZ) model: evidence from congenital blindness and visuo-cognitive aberrations

The causes of schizophrenia are still unknown. For the last 100 years, though, both “absent” and “perfect” vision have been associated with a lower risk for schizophrenia. Hence, vision itself and aberrations in visual functioning may be fundamental to the development and etiological explanations of the disorder. In this paper, we present the “Protection-Against-Schizophrenia” (PaSZ) model, which grades the risk for developing schizophrenia as a function of an individual's visual capacity. We review two vision perspectives: (1) “Absent” vision or how congenital blindness contributes to PaSZ and (2) “perfect” vision or how aberrations in visual functioning are associated with psychosis. First, we illustrate that, although congenitally blind and sighted individuals acquire similar world representations, blind individuals compensate for behavioral shortcomings through neurofunctional and multisensory reorganization. These reorganizations may indicate etiological explanations for their PaSZ. Second, we demonstrate that visuo-cognitive impairments are fundamental for the development of schizophrenia. Deteriorated visual information acquisition and processing contribute to higher-order cognitive dysfunctions and subsequently to schizophrenic symptoms. Finally, we provide different specific therapeutic recommendations for individuals who suffer from visual impairments (who never developed “normal” vision) and individuals who suffer from visual deterioration (who previously had “normal” visual skills). Rather than categorizing individuals as “normal” and “mentally disordered,” the PaSZ model uses a continuous scale to represent psychiatrically relevant human behavior. This not only provides a scientific basis for more fine-grained diagnostic assessments, earlier detection, and more appropriate therapeutic assignments, but it also outlines a trajectory for unraveling the causes of abnormal psychotic human self- and world-perception.

Auditory orienting and inhibition of return in schizophrenia: a functional magnetic resonance imaging study

Patients with schizophrenia (SP) exhibit deficits in both attentional reorienting and inhibition of return (IOR) during visual tasks. However, it is currently unknown whether these deficits are supramodal in nature and how these deficits relate to other domains of cognitive dysfunction. In addition, the neuronal correlates of this pathological orienting response have not been investigated in either the visual or auditory modality. Therefore, 30 SP and 30 healthy controls (HC) were evaluated with an extensive clinical protocol and functional magnetic resonance imaging (fMRI) during an auditory cuing paradigm. SP exhibited both increased costs and delayed IOR during auditory orienting, suggesting a prolonged interval for attentional disengagement from cued locations. Moreover, a delay in the development of IOR was associated with cognitive deficits on formal neuropsychological testing in the domains of attention/inhibition and working memory. Event-related fMRI showed the characteristic activation of a frontoparietal network (invalid trials>valid trials), but there were no differences in functional activation between patients and HC during either attentional reorienting or IOR. Current results suggest that orienting deficits are supramodal in nature in SP, and are related to higher-order cognitive deficits that directly interfere with day-to-day functioning.

Alertness can be improved by an interaction between orienting attention and alerting attention in schizophrenia

BACKGROUND

Attention is impaired in schizophrenia. Early attention components include orienting and alerting, as well as executive control networks. Previous studies have shown mainly executive control deficits, while few of them found orienting and alerting abnormalities. Here we explore the different attentive networks, their modulation and interactions in patients with schizophrenia.

METHODS

Twenty-one schizophrenic patients (DSMIV), compared to 21 controls, performed a modified version of the Attention Network Task, in which an orienting paradigm (with valid, invalid and no cues) was combined with a flanker task (congruent/incongruent) and an alerting signal (tone/no tone), to assess orienting, executive control and alerting networks independently.

RESULTS

Patients showed an abnormal alerting effect and slower overall reaction time compared to controls. Moreover, there was an interaction between orienting and alerting: patients are helped more than controls by the alerting signal in a valid orientation to solve the incongruent condition.

CONCLUSION

These results suggest that patients with schizophrenia have altered alerting abilities. However, the orienting and alerting cues interact to improve their attention performance in the resolution of conflict, creating possibilities for cognitive remediation strategies.

Real world referencing and schizophrenia: are we experiencing the same reality?

Psychotic symptoms in schizophrenia patients encompass the difficulty to distinguish between the respective points of view of self and others. The capacity to adopt and switch between different perspectives is, however, fundamental for ego- and allocentric spatial referencing. We tested whether schizophrenia patients are able to adopt and maintain a non-egocentric point of view in a complex visual environment. Twenty-four chronic schizophrenic outpatients (11 females) and 25 controls matched for age, gender, years of education and handedness were recruited from a population-based sample. In a virtual environment, participants had to make a decision as to which of two trash cans was closest to themselves (viewer-centered, egocentric), to a ball (object-centered, unstable allocentric), or to a palace (landmark-centered, stable allocentric). Main outcome measures were reaction time, error rate, learning rate and local task switch cost. While egocentric reaction time was preserved, patients showed an increased reaction time in both allocentric referencing conditions (stable and unstable) and an overall increased error rate. Switch cost was diminished in patients when changing from the egocentric to the landmark-centered condition and elevated when changing from the landmark-centered to the egocentric condition. The results imply that schizophrenia patients' adoption of an egocentric perspective is preserved. However, adopting an allocentric point of view and switching between egocentric and landmark-centered perspectives are impaired. Perturbations in non-egocentric referencing and transferring efficiently between different referential systems might contribute to altered personal and social world comprehension in schizophrenia.