Task-related hemodynamic responses in human early visual cortex are modulated by task difficulty and behavioral...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Visual Neuroscience

Background:

• Early visual cortex shows task-related responses (TRRs) even without visual stimulation.
• These responses are linked to arousal and reward, but their trial-to-trial variability is not well understood.

Purpose of the Study:

• To investigate if TRRs in the early visual cortex vary with individual trial performance and task difficulty.
• To determine if TRRs reflect arousal on a trial-by-trial basis.

Main Methods:

• Measured functional magnetic resonance imaging blood-oxygen-level-dependent (fMRI-BOLD) responses in the early visual cortex during an orientation discrimination task.
• Analyzed fMRI-BOLD signals in relation to task difficulty (easy vs. hard trials), behavioral accuracy, reaction time, and lapses.
• Correlated fMRI-BOLD findings with concurrent pupil size measurements.

Main Results:

• TRRs in the early visual cortex scaled with task difficulty, behavioral accuracy, reaction time, and lapses across individual trials.
• These modulations were independent of physiological noise sources like respiration, cardiac activity, or head movement.
• Pupil size exhibited similar trial-by-trial modulations with task difficulty and behavior.

Conclusions:

• Task-related responses in the early visual cortex reflect arousal and behavioral state on the timescale of individual trials.
• These findings suggest a broader role for the early visual cortex in monitoring task engagement and performance beyond basic visual processing.