When Doors of Perception Close: Bottom-up Models of Disrupted Cognition in Schizophrenia
Schizophrenia Research Center, Nathan Kline Institute for Psychiatric Research/New York University School of Medicine, Orangeburg, NY 10962, USA.Annual Review of Clinical Psychology (Impact Factor: 12.67). 02/2009; 5(1):249-75. DOI: 10.1146/annurev.clinpsy.032408.153502
Schizophrenia is a major mental disorder that affects approximately 1% of the population worldwide. Cognitive deficits are a key feature of schizophrenia and a primary cause of long-term disability. Current neurophysiological models of schizophrenia focus on distributed brain dysfunction with bottom-up as well as top-down components. Bottom-up deficits in cognitive processing are driven by impairments in basic perceptual processes that localize to primary sensory brain regions. Within the auditory system, deficits are apparent in elemental sensory processing, such as tone matching following brief delay. Such deficits lead to impairments in higher-order processes such as phonological processing and auditory emotion recognition. Within the visual system, deficits are apparent in functioning of the magnocellular visual pathway, leading to higher-order deficits in processes such as perceptual closure, object recognition, and reading. In both auditory and visual systems, patterns of deficit are consistent with underlying impairment of brain N-methyl-d-aspartate receptor systems.
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- "Stage 1 APS scores that were averaged across a range of auditory stimuli were further associated with executive functioning , whereas APS scores averaged across the entire hour of training (Hour 1 metrics) were also moderately associated with baseline verbal memory. These findings are consistent with previous research demonstrating relationships between auditory perception and performance in complex cognitive domains (Javitt, 2009; Kawakubo et al., 2006; Leitman et al., 2005; Light et al., 2007; Rissling et al., 2014). As evidenced by their moderate-to-strong associations with all cognitive domains, the composite metrics calculated after a full hour of training appear to provide a more robust indicator of auditory perceptual efficiency than do metrics derived from Level 1 or Stage 1. "
ABSTRACT: Conclusions: Sound Sweeps performance correlates with a range of neurocognitive abilities. APS improvement may provide a particularly sensitive index of "plasticity potential" within the neural network underlying verbal learning and memory.
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- "Our study thus provides the first direct evidence for temporally facilitated responses to chromatic and, thus, putatively parvocellularbiased , stimuli. While the neurophysiologic bases for this latency difference as well as for the discrepancies between single-unit and population-based levels of quantification remain to be fully resolved in future research, the present results lay grounds for further investigations of the visual system dynamics and of the 'division of labour' between the two pathways and, thus, for a better understanding of their contribution to visual processing deficits in clinical populations (e.g.,Javitt, 2009). That said, it is important to also note that peak latency and amplitude of VEP components, such as P1 and N1, are strongly influenced by low-level stimulus features, including contrast (e.g.Butler et al., 2007), the number and distribution of pixels within an image (Doniger et al., 2002;Foxe et al., 2001), and stimulus location within the visual field (Clark et al., 1995;Murray et al., 2001). "
ABSTRACT: Objects’ borders are readily perceived despite absent contrast gradients, e.g. due to poor lighting or occlusion. In humans, a visual evoked potential (VEP) correlate of illusory contour (IC) sensitivity, the “IC effect”, has been identified with an onset at ~90ms and generators within bilateral lateral occipital cortices (LOC). The IC effect is observed across a wide range of stimulus parameters, though until now it always involved high-contrast achromatic stimuli. Whether IC perception and its brain mechanisms differ as a function of the type of stimulus cue remains unknown. Resolving such will provide insights on whether there is a unique or multiple solutions to how the brain binds together spatially fractionated information into a cohesive perception. Here, participants discriminated IC from no-contour (NC) control stimuli that were either comprised of low-contrast achromatic stimuli or instead isoluminant chromatic contrast stimuli (presumably biasing processing to the magnocellular and parvocellular pathways, respectively) on separate blocks of trials. Behavioural analyses revealed that ICs were readily perceived independently of the stimulus cue – i.e. when defined by either chromatic or luminance contrast. VEPs were analysed within an electrical neuroimaging framework and revealed a generally similar timing of IC effects across both stimulus contrasts (i.e. at ~90ms). Additionally, an overall phase shift of the VEP on the order of ~30ms was consistently observed in response to chromatic vs. luminance contrast independently of the presence/absence of ICs. Critically, topographic differences in the IC effect were observed over the ~110-160ms period; different configurations of intracranial sources contributed to IC sensitivity as a function of stimulus contrast. Distributed source estimations localized these differences to LOC as well as V1/V2. The present data expand current models by demonstrating the existence of multiple, cue-dependent circuits in the brain for generating perceptions of illusory contours.
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- "The highlighting of sensorimotor systems is in contrast to the frequent emphasis on dysfunction of executive and highlevel association areas, which intuitively may be more related to cardinal symptoms of the disease. Sensory and motor impairments are nevertheless indicated by multiple lines of research (Butler et al., 2008; Javitt, 2009; Walther and Strik, 2012). Motor cortex, like prefrontal cortex, has lower neuronal density in schizophrenia when measured post-mortem (Benes et al., 1986) and imaging studies have shown alterations in cortical and subcortical motor areas (Dazzan et al., 2004; Honey et al., 2005). "
ABSTRACT: Schizophrenia is increasingly recognized as a neurodevelopmental disorder with altered connectivity among brain networks. In the current study we examined large-scale network interactions in childhood-onset schizophrenia, a severe form of the disease with salient genetic and neurobiological abnormalities. Using a data-driven analysis of resting-state functional magnetic resonance imaging fluctuations, we characterized data from 19 patients with schizophrenia and 26 typically developing controls, group matched for age, sex, handedness, and magnitude of head motion during scanning. This approach identified 26 regions with decreased functional correlations in schizophrenia compared to controls. These regions were found to organize into two function-related networks, the first with regions associated with social and higher-level cognitive processing, and the second with regions involved in somatosensory and motor processing. Analyses of across- and within-network regional interactions revealed pronounced across-network decreases in functional connectivity in the schizophrenia group, as well as a set of across-network relationships with overall negative coupling indicating competitive or opponent network dynamics. Critically, across-network decreases in functional connectivity in schizophrenia predicted the severity of positive symptoms in the disorder, such as hallucinations and delusions. By contrast, decreases in functional connectivity within the social-cognitive network of regions predicted the severity of negative symptoms, such as impoverished speech and flattened affect. These results point toward the role that abnormal integration of sensorimotor and social-cognitive processing may play in the pathophysiology and symptomatology of schizophrenia.
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