Visual Perception and Working Memory in Schizotypal Personality Disorder

Abstract

Objective-Patients affected by schizophrenia show deficits in both visual perception and working memory. The authors tested early-stage vision and working memory in subjects with schizotypal personality disorder, which has been biologically associated with schizophrenia.Method-Eleven subjects who met DSM-III-R criteria for schizotypal personality disorder and 12 normal comparison subjects were evaluated. Performance thresholds were obtained for tests of visual discrimination and working memory. Both form and trajectory processing were evaluated for each task.Results-Subjects with schizotypal personality disorder showed intact discrimination of form and trajectory but were impaired on working memory tasks.Conclusions-These data suggest that subjects with schizotypal personality disorder, unlike patients affected by schizophrenia, have relatively intact visual perception. Subjects with schizotypal personality disorder do show specific deficits on tasks of comparable difficulty when working memory demands are imposed. Schizotypal personality disorder may be associated with a more specific visual processing deficit than schizophrenia, possibly reflecting disruption of frontal lobe systems subserving visual working memory operations.Patients with schizophrenia have been reported to show deficits in visual perception. These deficits may be particularly severe in tasks requiring the integration of information over brief time periods, such as discrimination of speed or trajectory (1-4) and temporally modulated (flickering) patterns (5,6). These findings suggest that patients with schizophrenia may have a more pronounced deficit in neural systems involved in the processing of transient stimuli or information that requires sampling at a high temporal frequency. In the visual modality, such processing is often said to place demands on the transient channel, which may be subserved by the magnocellular system in the lateral geniculate nucleus (7) and the dorsal visual stream in the cortex (8). In contrast, the sustained channel of the visual system involved in the perception of form or object properties appears less affected by the disorder (1-5). Backwardmasking deficits in schizophrenia have sometimes been interpreted to be indicative of transient channel abnormalities, although processing speed and short-term memory disturbances may also contribute to these deficits (9-14). These visual deficits are consistent with positron emission tomography and functional magnetic resonance imaging studies reporting hyperactivation of the visual cortex in response to photic stimulation in schizophrenia (15, 16) and neuropathological evidence of increased neuronal density in the occipital area 17 (17).

Pharmacological manipulation of human working memory

“…parents, siblings, children) demonstrate deficits on tasks designed to measure working memory function (Park et al 1995a;Callicott et al 2003). In addition, individuals who score high on measures of psychosis proneness and individuals diagnosed with schizotypal personality disorder (Barch et al, unpublished data;Park et al 1995b;Park and McTigue 1997;Farmer et al 2000;Lenzenweger and Gold 2000;Roitman et al 2000;Mitropoulou et al 2002) also display deficits on working memory tasks.…”

Understanding Predisposition to Schizophrenia: Toward Intervention and Prevention

“…Individuals with SPD, for example, show deficits in nonverbal learning, and especially in verbal learning (51), in working memory (52), and in several executive functions, including concept formation, abstraction, and mental flexibility (53). Similarly, relatives of patients who do not have SPD show dysfunction in several cognitive domains, including motor and perceptual-motor ability, short-term memory, working memory, learning and recall, verbal and language skills, sustained attention, and executive function (2).…”

Neural correlates of visuospatial working memory in the ‘at-risk mental state’

“…Studies of monozygotic and dizygotic twins pairs discordant for schizophrenia (Cannon et al 2000 ;Glahn et al 2005) indicate that SWM deficits are associated with increased genetic risk for schizophrenia, and it has been suggested that a higher genetic loading for disease-related traits is linked to greater cognitive impairment (Saperstein et al 2006). Impaired spatial memory performance has also been reported in subjects with high levels of schizotypy (Park et al 1995) or schizotypal personality disorder (Farmer et al 2000), and in those with a history of very preterm birth (Narberhaus et al 2009). …”