S52. SPATIAL MEMORY DEFICITS IN SCHIZOPHRENIA: NEUROLOGICAL SOFT SIGNS DIFFERENTIALLY INFLUENCE PERFORMANCES IN 3-D VIRTUAL VERSUS TACTILE RECOGNITION TASKS
Authors: Abichou Kouloud , Gisquet Pascale , Bertholet Lea , Perreti Charles , Preissmann Delphine , Nuss Philippe 
Published: May 2020

Background

Cognitive impairment is a core meta-dimension in schizophrenia. Cognitive function interfaces with brain neural substrate and some of the observed neurocognitive deficits in the disease parallels with various brain structural and functional abnormalities found in schizophrenia, in particular neural dysconnectivity. The motor dysfunctions in schizophrenia such as evidenced by neurological soft signs (NSS) are also viewed as the consequence of this neural deregulation. NSS are seen both state- and trait-related features of schizophrenia and thus critical to identify schizophrenia subtypes. Although association between NSS and cognitive performance is well recognized in schizophrenia, the links between these subtle neurological sensory integration/motor deficits and cognitive abilities to represent space (spatial memory) has not been studied yet.

Here, we tested the spatial memory performances of schizophrenia patients using both tactile and 3D-virtual tests and examine whether the presence of NSS influenced the used strategies to perform a recognition task and examine spatial representation by dissociating spatial reference frameworks

We presumed that spatial memory will be differently affected in schizophrenia patients depending on the type of cues (local vs distal and tactile vs visual), as a function of the presence or not of NSS.

Methods

A total of 20 antipsychotic-treated, clinically stable, schizophrenia patients (SCZ) and 20 healthy matched controls (HC) gave their informed consent to participate in the study. We examined the strategies used by the participants in a protocol using two types of identical radial mazes (3-D virtual and perceptual). The same sequence of tasks was used for both mazes and included: exploration, acquisition, and conflict trials. Participants were proposed to freely explore the maze in order to identify their reinforced arm during the exploration trial. No specific advices were given regarding the use of local/distal or visual/tactile cues during the trials. Psychopathology and cognitive performances were assessed using PANSS, WCST, Digit Symbol Substitution test (DSST); medical and medication history was also evaluated. NSS were assessed using the NSS scale developed in French by Krebs et al. The number of reference memory errors (RME) made during the maze tasks was the main study variable

Results

NSS- and NSS+ patients did not differ in terms of PANSS score or antipsychotic medication. Typicals (haloperidol, loxapine, fluphenazine) and atypicals (risperidone, olanzapine and aripiprazole) were equally distributed within the 2 groups.

Among patients 13 had criteria for NSS (NSS+) and 7 did not meet criteria for NSS (NSS-). None of the HC exhibited NSS. NSS+ patients had more cognitive impairment than NSS- in the WCST.

While HC exhibited acquisition abilities for both spatial maze tasks, NSS+ patients were unable to learn any of them. NSS- patients, failed to learn during the virtual task but behave like control subjects in the tactile task. Data from rotation and permutation tasks in both virtual and tactile mazes could show that NSS+ and NSS- relied on different strategies and cues to try to solve the task. While NSS+ patients were totally unable to succeed the various tasks in the virtual and the tactile maze, NSS- individuals approached the HC performance in the tactile maze by using compensatory strategies but not in the virtual maze.

Discussion

Spatial memory is differently affected in schizophrenia patients as a function NSS. Spatial strategies differs in HC, NSS-, and NSS+ as a function of the type of cues (local vs distal) and the type of maze (virtual versus tactile) indicating that not only performance should be taken into account during the appraisal of spatial memory in schizophrenia