Content

1. What is visual perception?
2. Research
3. Section #3
   

Visual perception is a process of identification, organization, and interpretation of sensory data received by the human through the eye

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My research is focused on the neural correlates of visibility. What is required for an object to be visible? One might think, at first, that visibility should require only that light falls on the retina. But it can be more complicated, as shown in the illusions below: Unfilled Flicker, the Standing Wave of Invisibility, the Dichoptic Standing Wave, and the Stoper-Mansfield Effect. Illusions of invisibility such as these show that a stimulus can be projected onto our retinas, and nevertheless be partly or wholly invisible. By using these types of illusions one can focus on the portions of the stimulus that generate neuronal responses best correlated to visibility. Transient bursty activity occurs when a stimulus turns either on or off (the stimulus’ temporal edges), or when the eyes move. This same transient activity also occurs at the spatial edges of the stimulus. Moreover, when this transient – as opposed to sustained – activity is suppressed, visibility is decreased. We therefore conclude that visibility is linked to the spatiotemporal edges of stimuli, and that the neural correlate of spatiotemporal edges is transient bursty activity.

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To do: Press the button above to vary the duration and size of the box.

To notice: When the box flickers slowly, each flicker is of long duration and the box appears to be filled-in. When it flickers quickly (short duration flicker) it appears to be "unfilled": the center appears to be about the same color as the background. But even in the unfilled condition, the inside of the box is filled from the edges to some small extent, which is why we see a black frame. When the box flickers quickly and is skinny, however, the edges of the box are closer together and it appears filled-in, even though it has short duration flicker.

Unfilled Flicker is an illusion in which we can see that it is the edges of stimuli that evoke the strongest neural signals in our brains.

SOURCE:

Macknik, SL & Martinez-Conde, S, & Haglund, MM (2000) The Role of Spatiotemporal Edges in Visibility and Visual Masking. Proceedings of the National Academy of Sciences (USA) Vol. 97(13) pp. 7556-7560.

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