Faster but less precise: expectation enhances response speed while reducing sensory fidelity

Area of Science:

• Cognitive Neuroscience
• Computational Neuroscience
• Sensory Processing

Background:

• The brain efficiently processes sensory information using predictive mechanisms and internal models.
• It remains unclear if efficiency prioritizes expected or unexpected events, each offering adaptive advantages.
• Understanding this balance is key to explaining how the brain minimizes metabolic cost while maintaining flexibility.

Purpose of the Study:

• To investigate whether brain efficiency arises from prioritizing expected or unexpected sensory events.
• To independently manipulate task relevance (attention) and stimulus predictability to isolate expectation effects.
• To elucidate the neural mechanisms underlying the brain's adaptive efficiency in sensory processing.

Main Methods:

• Combined electroencephalography (EEG), pupillometry, and behavioral measures in human participants.
• Developed a paradigm to independently manipulate attention and stimulus predictability, controlling for low-level adaptation.
• Employed feature-specific neural decoding to analyze pre- and post-stimulus effects of attention and expectation.

Main Results:

• Participants responded faster and more accurately to expected events, an effect enhanced by attention.
• Expected events were encoded with lower representational fidelity (reduced precision), independent of attention.
• Neural decoding revealed attention's pre-stimulus effects and expectation's post-stimulus effects, with no interaction.

Conclusions:

• The brain employs two complementary processes for leveraging environmental redundancy: early attention-mediated response to expected events and later dampened sensory response to expected events.
• Attention enhances rapid motor responses to expected stimuli, while expectation reduces sensory precision, prioritizing unexpected stimuli for updating internal models.
• These findings offer a unified explanation for balancing sensory processing efficiency with adaptability across different timescales.