Impaired top-down processes in schizophrenia: A DCM study of ERPs

Affective processing in positive schizotypy: Loose control of social-emotional information

“…Absorption implicates weak control of representations of perceptual input, presumably by reduced prefrontal executive control, and may share a common biological basis with positive schizophrenic symptoms (Ott, Reuter, Henning, & Vaitl, 2005;van Kampen, 2012). Together these findings support the notion that attenuated top-down modulation of perceptual processing may apply across the schizophrenia spectrum (Dima et al, 2010;Koychev et al, 2012).…”

“…Reduced task-related inhibitory connectivity between frontal and posterior cortices during the performance of cognitive tasks were observed in patients with schizophrenia as compared to healthy controls (Koychev, El-Deredy, Mukherjee, Haenschel, & Deakin, 2012;Winterer, Coppola, Egan, Goldberg, & Weinberger, 2003) and in nonclinical individuals with elevated levels of schizotypal traits (Koychev, Deakin, Haenschel, & El-Deredy, 2011). It was proposed that these findings refer to attenuated top-down regulation of perceptual processing across the schizophrenia spectrum (Koychev et al, 2012; see also Dima, Dietrich, Dillo, & Emrich, 2010). Only very little research has addressed correlations between positive schizophrenia symptoms and prefrontal-posterior coupling in the context of social-emotional processing.…”

Translational Perspectives for Computational Neuroimaging

“…Intriguingly, patients with schizophrenia are, on average, considerably less susceptible to this illusion than healthy controls (Dima et al, 2009). Two separate fMRI and EEG studies examined potential mechanisms for this phenomenon: applying structurally analogous DCMs to fMRI and EEG data, these two studies consistently found a strengthening of bottom-up connections and diminished top-down connectivity in patients, consistent with the notion of reduced precision of predictions about facial stimuli (Dima et al, 2009(Dima et al, , 2010. Notably, weakening of top-down predictions may explain a range of perceptual alterations in schizophrenia (Notredame et al, 2014) and may also play a role in the initial formation of delusions (Schmack et al, 2013).…”

“…et al (2014) reported, similar to the hollow mask illusion study byDima et al (2010), a marked reduction of top-down connections in the visual hierarchy. For auditory MMN, the DCM results byDima et al (2012) suggested that patients exhibited both abnormal forward and backward effective connectivity, accompanied by reduced postsynaptic gain of pyramidal cells in primary auditory cortex.…”

Dynamic Causal Models for fMRI

“…Other notable work on schizophrenia examined possible mechanisms why perceptual illusions are less impaired in schizophrenic patients. Two separate studies, applying DCM to fMRI and EEG data from the hollow-mask illusion paradigm, found increased strength of bottom-up but decreased strength of top-down connections (Dima, Dietrich, Dillo, & Emrich, 2010;Dima et al, 2009). This replicated finding nicely agrees with predictions from theories of impaired perceptual inference in schizophrenia, which posit a reduction in the precision of perceptual priors (for a recent review, see Adams, Stephan, Brown, Frith, and Friston (2013)).…”