Task-related hemodynamic responses are modulated by reward and task engagement

Area of Science:

• Neuroscience
• Systems Neuroscience
• Cognitive Neuroscience

Background:

• Hemodynamic responses in the visual cortex show endogenous task-related activity.
• This activity may reflect task engagement, a state distinct from attention.

Purpose of the Study:

• To investigate the relationship between task engagement and hemodynamic responses in the primary visual cortex (V1).
• To differentiate task engagement from attention using hemodynamic measurements.

Main Methods:

• Intrinsic-signal optical imaging was used to record hemodynamic measurements from the primary visual cortex (V1) of monkeys.
• Task engagement was manipulated by varying reward size and incorporating rest periods during a periodic fixation task.
• Hemodynamic responses were analyzed across different timescales (seconds to minutes).

Main Results:

• Higher rewards correlated with increased temporal precision and modest strengthening of task-related responses in V1.
• Sustained high-reward periods induced ramp-like decreases in local blood volume, which reversed during low-reward periods.
• Complete task disengagement (e.g., closing eyes) led to sharp increases in blood volume over longer durations (5-10 minutes).

Conclusions:

• Hemodynamic recordings reveal distinct neural and vascular changes associated with task engagement.
• A mechanism controlling vascular tone, alongside neural responses, likely modulates task engagement across various timescales.
• Findings suggest task engagement is a significant factor influencing brain hemodynamics beyond mere attentional states.