Uncoupling Sensation and Perception in Human Time Processing.

Area of Science:

• Neuroscience
• Cognitive Science
• Perception

Background:

• Temporal processing involves a hierarchy from basic duration encoding to abstract time perception.
• The neural underpinnings of subjective time experience remain largely unknown.
• Differentiating sensory and perceptual timing mechanisms is crucial for understanding time perception.

Purpose of the Study:

• To distinguish brain activity associated with lower-level sensory duration encoding and higher-order perceptual timing.
• To investigate the neural basis of subjective time experience.
• To map objective versus subjective duration processing in the brain.

Main Methods:

• Event-related functional magnetic resonance imaging (fMRI) was employed.
• Participants compared standard visual stimuli with probe stimuli exhibiting objective or subjective duration differences.
• Stimuli included sinusoidal gratings with constant or accelerating velocity to manipulate perceived duration.

Main Results:

• Objective duration processing activated early extrastriate and fusiform visual areas.
• Subjective duration experience engaged a distributed network including the superior frontal gyrus, cerebellum, basal ganglia, parietal cortex, and posterior cingulate cortex.
• Independent neural substrates were identified for objective duration encoding and subjective time perception.

Conclusions:

• Two distinct stages of timing were proposed: early sensory extraction of duration and higher-order subjective experience.
• Sensory cortices handle objective duration, while a cortical-subcortical network underlies subjective time perception.
• This research provides a neural framework for understanding the dissociation between physical time and perceived duration.