Second order components of moving plaids activate extrastriate cortex: a positron emission tomography study

Area of Science:

• Neuroscience
• Visual Perception
• Computational Neuroscience

Background:

• Moving plaids are complex visual stimuli formed by superimposing gratings with different orientations and motion directions.
• Perception of plaid motion involves both binocular (intersection of constraints) and monocular (contrast envelope tracking) mechanisms.
• Neurones in area V5/MT respond to plaids, but psychophysical evidence suggests contrast envelope tracking is monocular, posing a localization challenge.

Purpose of the Study:

• To localize the neural mechanisms responsible for monocular contrast envelope tracking in moving plaid perception.
• To investigate the role of specific visual areas in processing complex motion stimuli.

Main Methods:

• Positron emission tomography (PET) activation study comparing brain activity during presentation of plaid components versus a superimposed moving plaid.
• Subjects viewed alternating plaid components during control scans and the moving plaid during activation scans.
• Analysis focused on differential brain activation between the two conditions.

Main Results:

• Differential brain activation was observed in area V3 when subjects viewed the moving plaid compared to its components.
• These findings align with recent macaque studies showing increased sensitivity to moving plaids in V3 neurons.
• Area V3 appears to be involved in processing the contrast envelope of moving plaids.

Conclusions:

• The contrast envelope tracking mechanism, crucial for perceiving plaid motion, is localized to area V3.
• Area V3 plays a significant role in the neural processing of complex moving patterns beyond component motion.
• This study bridges psychophysical and neurophysiological findings regarding plaid perception.