Person:
Serrano Pedraza, Ignacio

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First Name
Ignacio
Last Name
Serrano Pedraza
URI
https://hdl.handle.net/20.500.14352/80226
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Psicología
Department
Psicología Experimental, Procesos Cognitivos y Logopedia
Area
Psicología Básica
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2013 - 20152
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Author: Brash, Claire × Subject: 159.93 ×

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    Moderate acute alcohol intoxication has minimal effect on surround suppression measured with a motion direction discrimination task.
    (Journal of vision, 2015) Read, Jenny C A; Georgiou, Renos; Brash, Claire; Yazdani, Partow; Whittaker, Roger; Trevelyan, Andrew J; Serrano Pedraza, Ignacio
    A well-studied paradox of motion perception is that, in order to correctly judge direction in high-contrast stimuli, subjects need to observe motion for longer in large stimuli than in small stimuli. This effect is one of several perceptual effects known generally as "surround suppression." It is usually attributed to center-surround antagonism between neurons in visual cortex, believed to be mediated by GABA-ergic inhibition. Accordingly, several studies have reported that this index of surround suppression is reduced in groups known to have reduced GABA-ergic inhibition, including older people and people with schizophrenia and major depressive disorder. In this study, we examined the effect on this index of moderate amounts of ethanol alcohol. Among its many effects on the nervous system, alcohol potentiates GABA-ergic transmission. We therefore hypothesized that it should further impair the perception of motion in large stimuli, resulting in a stronger surround-suppression index. This prediction was not borne out. Alcohol consumption slightly worsened duration thresholds for both large and small stimuli, but their ratio did not change significantly.
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    Testing the horizontal-vertical stereo anisotropy with the critical-band masking paradigm
    (Journal of vision, 2013) Serrano Pedraza, Ignacio; Brash, Claire; Read, Jenny C A
    Stereo vision has a well-known anisotropy: At low frequencies, horizontally oriented sinusoidal depth corrugations are easier to detect than vertically oriented corrugations (both defined by horizontal disparities). Previously, Serrano-Pedraza and Read (2010) suggested that this stereo anisotropy may arise because the stereo system uses multiple spatial-frequency disparity channels for detecting horizontally oriented modulations but only one for vertically oriented modulations. Here, we tested this hypothesis using the critical-band masking paradigm. In the first experiment, we measured disparity thresholds for horizontal and vertical sinusoids near the peak of the disparity sensitivity function (0.4 cycles/°), in the presence of either broadband or notched noise. We fitted the power-masking model to our results assuming a channel centered on 0.4 cycles/°. The estimated channel bandwidths were 2.95 octaves for horizontal and 2.62 octaves for vertical corrugations. In our second experiment we measured disparity thresholds for horizontal and vertical sinusoids of 0.1 cycles/° in the presence of band-pass noise centered on 0.4 cycles/° with a bandwidth of 0.5 octaves. This mask had only a small effect on the disparity thresholds, for either horizontal or vertical corrugations. We simulated the detection thresholds using the power-masking model with the parameters obtained in the first experiment and assuming either single-channel and multiple-channel detection. The multiple-channel model predicted the thresholds much better for both horizontal and vertical corrugations. We conclude that the human stereo system must contain multiple independent disparity channels for detecting horizontally oriented and vertically oriented depth modulations.