The spatial-frequency characteristics of the visual system in schizophrenia

Computational Modeling of Contrast Sensitivity and Orientation Tuning in First-Episode and Chronic Schizophrenia

“…Other parameter changes (e.g., in the V1 excitatory learning rate) were added to reduced inhibition in an exploratory fashion to determine if these led to a better fit to previously reported data than reduced V1 inhibition alone. Our specific hypotheses regarding chronic schizophrenia were that (a) decreased CS, at the level of a 20%–35% reduction in CS at low SFs (O’Donnell et al, 2006 ; Shoshina et al, 2015 ), would emerge as a result of decreased V1 inhibition; (b) broadened OR tuning, at the level of ∼20%, would also emerge as a result of reduced V1 inhibition, based on findings of both reduced V1 GABA concentration and of this level of broadened OR tuning in chronic schizophrenia patients (Rokem et al, 2011 ), as well on known effects of GABA antagonists on OR tuning (Katzner et al, 2011 ); and (c) further broadening in OR tuning would emerge with increases in the Hebbian learning rate for weights of afferent input to V1 and/or excitatory influences within V1.…”

“…Our goal was to develop a model in which reductions in retinal signaling would be associated with an ∼25% increase in CS for low-SF stimuli only. While studies of CS in unmedicated FES have varied in their experimental methods and findings, we chose to fit the pattern demonstrated by Shoshina et al ( 2015 ) because (a) that study used stimuli similar to those used in our models; (b) it had a larger number of untreated first-episode patients ( n = 11) than the study of Cadenhead et al ( 2013 ; n = 5), which examined medication effects in post hoc analyses only; and (c) while it reported a smaller increase in CS compared to Kelemen et al ( 2013 ; n = 28), who reported an ∼33% increase, the stimuli and presentation methods used in the latter study differed significantly from those used in our models (in terms of SFs and stimulus backgrounds), and we also wished to be conservative and assume a smaller between-group effect, given the small number of (mostly small) studies of this issue.…”

“…Multiple aspects of visual processing are impaired in schizophrenia, including visual acuity (Smith, Pantelis, McGrath, Tangas, & Copolov, 1997 ), peripheral vision (Kraehenmann, Vollenweider, Seifritz, & Kometer, 2012 ), stereopsis (Schechter et al, 2006 ), contrast sensitivity (CS; Calderone et al, 2013 ), spatial frequency (SF) processing (Shoshina, Shelepin, Vershinina, & Novikova, 2015 ), vernier acuity (Keri, Kelemen, Benedek, & Janka, 2004 ), forward and backward masking (Green, Lee, Wynn, & Mathis, 2011 ), flanker effects (Keri, Kelemen, Benedek, & Janka, 2005 ), surround suppression (Dakin, Carlin, & Hemsley, 2005 ), size estimation (Asarnow & Mann, 1978 ), distance estimation (Weckowicz, Sommer, & Hall, 1958 ), perceptual organization (Silverstein & Keane, 2011 ), coherent motion perception (Chen, 2011 ), face perception (Turetsky et al, 2007 ), size constancy (Silverstein et al, 2013 ), and effects of prior knowledge on interpretation of visual input (Keane, Silverstein, Wang, & Papathomas, 2013 ). In addition, 25%–30% of individuals with schizophrenia report visual hallucinations (Waters et al, 2014 ), and the rate of patients reporting visual distortions (in the domains of brightness, motion, form, and color) has been estimated to be from 30% to over 60% (Bunney et al, 1999 ; Cutting & Dunne, 1986 ; Phillipson & Harris, 1985 ).…”

“…In short, the goal of our chronic schizophrenia modeling efforts was to reproduce a large impairment, relative to controls, at a low SF, and a small impairment at a higher SF. In contrast, we attempted to model an increase in CS for low SFs and normal CS at medium SFs in unmedicated first-episode schizophrenia (FES), as has now been demonstrated psychophysically in several studies (Cadenhead, Dobkins, McGovern, & Shafer, 2013 ; Kelemen, Kiss, Benedek, & Keri, 2013 ; Kiss, Fabian, Benedek, & Keri, 2010 ; Shoshina et al, 2015 ).…”

Development of a sensory and perceptual assessment test for psychosis and schizophrenia

“…Although the evidence that sensory processes are altered in schizophrenic patients is widely accepted, the exact nature and impact of these alterations are not fully understood. Studies on size perception (Davis, et al, 1967), perceptual organization (Silverstein, et al, 2011), illusions (King, et al, 2017), contrast sensitivity and spatial frequency (Flevaris, et al, 2014;Graham and Meng, 2011;Green, et al, 2008;Shoshina, et al, 2015;Silverstein, et al, 2017), face perception and recognition (Kim, et al, 2015;McBrain, et al, 2010;Silverstein, et al, 2014;Vakhrusheva, et al, 2014), visual integration (Postmes, et al, 2014;Silverstein, et al, 2009;Silverstein, et al, 2012;Silverstein, et al, 2015), visual search (Chen, 2011;Dias, et al, 2013), mismatch negativity or odd ball paradigm (Avissar, et al, 2018;Hamilton, et al, 2019) among others, have all addressed issues related to sensory processes in schizophrenia.…”