How the Visual Cortex Handles Stimulus Noise: Insights from Amblyopia

Abstract

Adding noise to a visual image makes object recognition more effortful and has a widespread effect on human electrophysiological responses. However, visual cortical processes directly involved in handling the stimulus noise have yet to be identified and dissociated from the modulation of the neural responses due to the deteriorated structural information and increased stimulus uncertainty in the case of noisy images. Here we show that the impairment of face gender categorization performance in the case of noisy images in amblyopic patients correlates with amblyopic deficits measured in the noise-induced modulation of the P1/P2 components of single-trial event-related potentials (ERP). On the other hand, the N170 ERP component is similarly affected by the presence of noise in the two eyes and its modulation does not predict the behavioral deficit. These results have revealed that the efficient processing of noisy images depends on the engagement of additional processing resources both at the early, feature-specific as well as later, object-level stages of visual cortical processing reflected in the P1 and P2 ERP components, respectively. Our findings also suggest that noise-induced modulation of the N170 component might reflect diminished face-selective neuronal responses to face images with deteriorated structural information.

Adaptation Duration Dissociates Category-, Image-, and Person-Specific Processes on Face-Evoked Event-Related Potentials

“…Some studies linked this component to task difficulty (Philiastides et al, 2006 ) while others emphasized the role of P2 in face-related tasks for which we have expertise (such as in case of own race effect, Stahl et al, 2008 ). P2 enhancement was also found recently investigating the effect of added noise (Bankó et al, 2011 , 2013 ; Németh et al, 2014 ). Even though the LO/LOC is believed to be an object-selective area, some studies have found that its caudal part is also responsive to faces.…”

Early temporal negativity is sensitive to perceived (rather than physical) facial identity

“…Specifically, the P200 component has been reported to be smaller (less positive) in less difficult tasks or with less sensory noise (Banko et al, 2011;Banko et al, 2013). Using converging evidence from fMRI, their P200 effect was attributed to the lateral occipital complex (Banko et al, 2011).…”

“…Furthermore, a larger P200 component has also been attributed to increased task difficulty (Philiastides, Ratcliff, & Sajda, 2006). Specifically, P200 amplitude may reflect the difficulty of sensory processing, and has been shown to increase when noise was added to face stimuli in gender categorization tasks (Banko, Gal, Koertvelyes, Kovacs, & Vidnyanszky, 2011;Banko, Koertvelyes, Weiss, & Vidnyanszky, 2013).…”

Steady-State Contrast Response Functions Provide a Sensitive and Objective Index of Amblyopic Deficits

“…Several studies have reported abnormalities in the amplitude and latency of visual evoked potentials (VEPs) such as the P100 and N170 for stimuli shown in the amblyopic eye. [14][15][16][17][18] Other studies have used steady-state visual evoked potentials (SSVEPs) to compare the amplitude of normal and amblyopic responses to flickering stimuli. [19][20][21] However, such work has typically measured responses at only a single contrast level, which is insufficient to provide a complete picture of the amblyopic deficit for contrast processing.…”