Noise as a mechanism of anomalous face processing among persons with Schizophrenia

Abstract

There is substantial evidence that people with Schizophrenia (SCZ) have altered visual perception and cognition, including impaired face processing. However, the mechanism(s) underlying this observation are not yet known. Eye movement studies have found that people with SCZ do not direct their gaze to the most informative regions of the face (e.g., the eyes). This suggests that SCZ patients may be less able to extract the most relevant face information and therefore have decreased calculation efficiency. In addition, research with non-face stimuli indicates that SCZ is associated with increased levels of internal noise. Importantly, both calculation efficiency and internal noise have been shown to underpin face perception among healthy observers. Therefore, the current study applies noise masking to upright and inverted faces to determine if face processing deficits among those with SCZ are the result of changes in calculation efficiency, internal noise, or both. Consistent with previous results, SCZ participants exhibited higher contrast thresholds in order to identify masked target faces. However, higher thresholds were associated with increases in internal noise but unrelated to changes in calculation efficiency. These results suggest that SCZ-related face processing deficits are the result of a decreased noise-to-signal ratio. The source of increased processing noise among these patients is unclear, but may emanate from abnormal neural dynamics.

Computational Modeling of Genetic Contributions to Excitability and Neural Coding in Layer V Pyramidal Cells: Applications to Schizophrenia Pathology

“…When this heterogeneity is present in many cells in the local circuits, it might lead to network dynamics that are more sensitive to perturbations. This hypothesis is a cell type-specific (although likely generalizable to other pyramidal neurons), genetically based adaptation of a higher-level hypothesis of an excessive noise in information processing in SCZ (Spitzer and Neumann, 1996; Christensen et al, 2013) (reviewed in Silverstein et al, 2017).…”

Increased Equivalent Input Noise in Glaucomatous Central Vision: Is it Due to Undersampling of Retinal Ganglion Cells?

“…This paradigm has been employed in a number of studies that aim to elucidate the mechanism underpinning changes in contrast sensitivity due to either aging, [33][34][35][36][37] perceptual learning, [38][39][40] spatial attention, 41 or stimulus properties, such as spatial frequency. [42][43][44] The equivalent input noise paradigm has been also used to characterize a loss of contrast sensitivity in various clinical populations, including amblyopia, [45][46][47] retinitis pigmentosa, 48 diabetes, 49 schizophrenia, 50 and dyslexia. 51 It was also used to study the mechanism underlying a loss of motion sensitivity in glaucoma.…”

Effects of Domain-Specific Noise on Visual Motion Processing in Schizophrenia

“…To perform the motion perception task, patients required a larger proportion of signal dots or a smaller proportion of noise dots [29], [30], suggesting that either heightened internal noise or weakened signal encoding undermines their performance levels. In perceiving biological motion and face perception, when target stimuli were combined with noise stimuli the degradation of patients' performance depended upon the noise level, a result consistent with the existence of heightened internal noise [20], [21]. In visual and auditory speech perception, when various levels of non-uniform and frequency-dependent noise were present patients showed deficits specifically under the condition where sensory integration was optimal for controls [31].…”