The spatial extent of lateral interactions in flicker perception.

Area of Science:

• Visual Perception
• Neuroscience
• Psychophysics

Background:

• The perceived intensity of visual stimuli can be influenced by surrounding elements.
• Understanding the spatial and temporal interactions in visual processing is key to deciphering neural mechanisms.

Purpose of the Study:

• To investigate how the relative phase of a temporally modulated annulus affects the perceived flicker strength of a central stimulus.
• To determine the role of annulus size in this phase-dependent modulation of visual flicker perception.

Main Methods:

• Two subjects participated in psychophysical experiments.
• Measurements involved varying the phase difference between a central flickering stimulus and a surrounding annulus.
• The outer diameter of the annulus was systematically altered.

Main Results:

• Perceived flicker strength of the center stimulus was significantly modulated by the phase difference between the center and annulus.
• This modulation was dependent on the size of the annulus, initially increasing with size before plateauing.
• In the absence of an annulus, no modulation of flicker strength was observed.

Conclusions:

• The findings suggest that the perceived flicker strength of a central stimulus is influenced by surrounding visual context.
• The spatial characteristics of this influence, with a space constant of approximately 0.5 degrees, align with receptive field sizes of subcortical neurons.
• This supports the hypothesis that the neural basis for perceived flicker strength is established at a subcortical level of visual processing.