Perception of invisible masked objects in early infancy

Recurrent loops in the visual cortex play a critical role in visual perception, which is likely not mediated by purely feed-forward pathways. However, the development of recurrent loops is poorly understood. The role of recurrent processing has been studied using visual backward masking, a perceptual phenomenon in which a visual stimulus is rendered invisible by a following mask, possibly because of the disruption of recurrent processing. Anatomical studies have reported that recurrent pathways are immature in early infancy. This raises the possibility that younger infants process visual information mainly in a feed-forward manner, and thus, they might be able to perceive visual stimuli that adults cannot see because of backward masking. Here, we show that infants under 7 mo of age are immune to visual backward masking and that masked stimuli remain visible to younger infants while older infants cannot perceive them. These results suggest that recurrent processing is immature in infants under 7 mo and that they are able to perceive objects even without recurrent processing. Our findings indicate that the algorithm for visual perception drastically changes in the second half of the first year of life.

Perception of invisible masked objects in early infancy

Recurrent loops in the visual cortex play a critical role in visual perception, which is likely not mediated by purely feedforward pathways. However, the development of recurrent loops is poorly understood. The role of recurrent processing has been studied using visual backward masking, a perceptual phenomenon in which a visual stimulus is rendered invisible by a following mask, possibly because of the disruption of recurrent processing. Anatomical studies have reported that recurrent pathways are immature in early infancy. This raises the possibility that younger infants process visual information mainly in a feedforward manner, and thus, they might be able to perceive visual stimuli that adults cannot see because of backward masking. Here, we show that infants under 7 months of age are immune to visual backward masking and that masked stimuli remain visible to younger infants while older infants cannot perceive them. These results suggest that recurrent processing is immature in infants under 7 months and that they are able to perceive objects even without recurrent processing. Our findings indicate that the algorithm for visual perception drastically changes in the second half of the first year of life.

Electrophysiological correlates of visual backward masking in patients with bipolar disorder

BackgroundIn visual backward masking (VBM), a target is followed by a mask that decreases target discriminability. Schizophrenia patients (SZ) show strong and reproducible masking impairments, which are associated with reduced EEG amplitudes. Patients with bipolar disorder (BP) show masking deficits, too. Here, we investigated the neural EEG correlates of VBM in BP.Methods122 SZ, 94 unaffected controls, and 38 BP joined a standard VBM experiment. 123 SZ, 94 unaffected controls and 16 BP joined a corresponding EEG experiment, analyzed in terms of the global field power.ResultsAs in previous studies, SZ and BP show strong masking deficits. Importantly and similarly to SZ, BP show decreased global field power amplitudes at approximately 200 ms after the target onset, compared to controls.ConclusionsThese results suggest that VBM deficits are not specific for schizophrenia but for a broader range of functional psychoses. Potentially, both SZ and BP show deficient target enhancement.

Can a Low-Cost Eye Tracker Assess the Impact of a Valent Stimulus? A Study Replicating the Visual Backward Masking Paradigm

Capturing affective response to valent stimuli using eye tracking is of interest not only to academic research but also to commercial equipment developers (e.g. car dashboards). In order to investigate whether a low-cost eye tracker can effectively detect participants’ physiological response to negatively valent stimuli, 44 participants aged 19–24 (mean = 24.7, SD = 5.8) were recruited to complete the visual backward masking paradigm in a repeated-measure experimental design. Saccadic duration and pupil sizes were recorded using a lower-end 60-Hz tracker. Data was analysed using a mix of parametric and non-parametric tests. Our results suggest that valence in the form of fearful vs neutral faces has a significant main effect on both saccadic duration [V = 931, P < 0.001, d = 0.96] and pupil size [t(43) = 29.81, P < 0.001, d = 3.91)]. Our findings were further supported by Bayes factor analysis, which showed that saccadic duration data was 24 times more likely to occur, and pupil size measurement data was 89 times more likely, under the alternative hypothesis, showing that differences in valence had a main effect. The combined evidence produced by our Bayesian analysis, the large effect sizes of our frequentist analysis and the significant effect on two separate measurements lead us to suggest that, under the right conditions, low-cost eye trackers can successfully detect changes in saccadic duration and pupil sizes as a result of physiological responses to threat-relevant visual stimuli.

Neural Compensation Mechanisms of Siblings of Schizophrenia Patients as Revealed by High-Density EEG

Visual backward masking (VBM) deficits are candidate endophenotypes of schizophrenia indexing genetic liability of the disorder. In VBM, a target is followed by a mask that deteriorates target perception. Schizophrenia patients and, to a lesser extent, their unaffected relatives show strong and reproducible VBM deficits. In patients, VBM deficits are associated with strongly decreased amplitudes in the evoked-related potentials (ERPs). Here, to unveil the neural mechanisms of VBM in schizophrenia, circumventing illness-specific confounds, we investigated the electroencephalogram correlates of VBM in unaffected siblings of schizophrenia patients. We tested 110 schizophrenia patients, 60 siblings, and 83 healthy controls. As in previous studies, patients showed strong behavioral deficits and decreased ERP amplitudes compared to controls. Surprisingly, the ERP amplitudes of siblings were even higher than the ones of controls, while their performances were similar. ERP amplitudes in siblings were found to correlate with performance. These results suggest that VBM is deteriorated in patients and siblings. However, siblings, unlike patients, can partially compensate for the deficits by over-activating a network of brain regions.

The Independence of a Simple Visual-Motor Reaction from the Preconscious Component of Sensation during Backward Masking by Two-Color Stimuli

The model of visual backward masking in its two-color modification is applicable in the study of the mechanisms of conjugation of the processes of sensory sensation formation and realization of sensorimotor reactions. The effect of the full (100 %) two-color backward masking is reliably implemented with the following values of its parameters: the duration of the test stimulus (red and green) is 0 ms, the stimulus masker (blue) is 45 ms, and the stimulus onset asynchrony (SOA) is 0.1 — 25 ms. In the range of SOA values from 25 to 35 ms, the efficiency of backward masking decreases to 14 %, and with an SOA of 40 ms, it completely disappears. The stimulus detection time (sDT) as part of a simple visual-motor reaction in the paradigm of the model of two-color backward masking does not depend on its effectiveness, the color of the test stimulus, the value of asynchrony in the range (0 — 40 ms), the duration of the stimulus-masker in the formation of a conscious light sensation. A comparative analysis of the stimulus detection time values under the conditions of full (100 %) backward masking and in its absence suggests that the mechanism of the two-color backward masking not associated with photoreceptors, but is implemented in the central parts of the visual analyzer.