Information-processing Abnormalities: Trait- and State-dependent Components

Abstract

Schizophrenics were compared to schizoaffective, bipolar, and nonpsychotic depressed patients in a visual masking paradigm in which an informational target stimulus was followed at varying intervals by a noninformational masking stimulus. In limiting the availability of the sensory signal provided by the target stimulus, the mask was used to probe how information from the environment enters and is processed by the central nervous system. The use of the masking paradigm was originally based on the hypothesis that thought disorder is a result of a more primary dysfunction in the processes that precede and result in thought. Results confirmed previous findings of a performance deficit in the schizophrenics when compared to nonpsychotic controls. Schizoaffective and bipolar patients also showed evidence of impaired processing, however. Results were interpreted in terms of a trait/state formulation in which impaired information processing is seen as a fundamental trait of schizophrenia spectrum disorders and as a state that can covary with psychotic illness in general. A unifying concept centers on the effects of psychopathological conditions on an individual's processing resources that results in either underprovision or overprovision of information from sensory input to complex cognitive operations dependent on the cerebral cortex. Findings from a variety of paradigms are consistent with those of the masking paradigm in revealing that the processing deficits of schizophrenics are time dependent and occur in the 500 ms following stimulus input.

What's in a face? Effects of stimulus duration and inversion on face processing in schizophrenia

“…Within patients, increased duration threshold needed to perform at 70% correct on the object discrimination task correlated with reduced contrast sensitivity to low (magnocellular-biased), but not medium or high spatial frequency stimuli, suggesting that the increased duration thresholds may be due to magnocellular dysfunction within this group. The finding of an elevated critical duration for house discrimination in schizophrenia echoes well-established findings of elevated duration thresholds for more primitive objects (Slaghuis and Bakker, 1995) or letters (Saccuzzo and Braff, 1986). Deficits in contrast sensitivity have also been seen in other studies of schizophrenia Keri et al, 2002;Slaghuis, 1998).…”

“…Although such deficits have been documented most comprehensively with regard to face emotion processing (Kerr and Neale, 1993;Kohler et al, 2000), deficits have been documented as well in processing of other face characteristics -such as unfamiliarity, identity or age (Addington and Addington, 1998;Kerr and Neale, 1993;Kohler et al, 2000;Sachs et al, 2004) -as well as for processing of non-face objects (Doniger et al, 2002;Saccuzzo and Braff, 1986). An initial finding of this study is that patients, as a group, needed substantially more time than controls -375 vs. 250 ms -to perform at 70% correct in our object discrimination task.…”

Early-Stage Visual Processing Deficits in Schizophrenia

“…Most backward masking studies in schizophrenia have been done using masks that spatially overlap the targets [13,26,[63][64][65]. Rassovsky et al [66] recently examined masking in schizophrenia using masks that surround, rather than overlap, the target.…”

GABAergic Interneurons Implications for Understanding Schizophrenia and Bipolar Disorder

“…For example, as early as 1972, Eugene Roberts postulated that this compound might play a central role in the pathophysiology of schizophrenia (Roberts 1972). Schizophrenia typically involves disturbances of cognitive functioning that include impaired attentional responses (McGhie and Chapman 1961), disruptions of normal information processing (Saccuzzo and Braff 1986; Braff et al 1991), and a selective impairment in declarative memory (Heckers et al 1998). Overall, the thought pattern of schizophrenics has been described as being "over-inclusive", i.e.…”