FEF-microstimulation causes task-dependent modulation of occipital fMRI activity

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Systems Neuroscience

Background:

• Electrical microstimulation of the frontal eye fields (FEF-EM) influences neuronal activity in visual area V4.
• FEF-EM elicits functional magnetic resonance imaging (fMRI) activations in the visual cortex, previously thought to be solely bottom-up dependent.

Purpose of the Study:

• To investigate if FEF-EM-induced fMRI modulations are dependent on task demands.
• To determine if top-down mechanisms gate FEF signals in the early visual cortex.

Main Methods:

• Two monkeys were scanned using fMRI while performing a visually guided saccade task.
• fMRI data was also collected during passive fixation tasks with and without visual stimuli.
• FEF-EM was applied to modulate neural activity.

Main Results:

• FEF-EM effects on visual cortex fMRI activity were significantly increased during the saccade task compared to fixation tasks.
• This indicates that FEF-EM's influence is task-dependent.
• The impact of FEF-EM was most prominent in visual cortex voxels with lower baseline activation by visual stimuli.

Conclusions:

• FEF-EM-induced activation patterns in the early visual cortex are topographically specific.
• These modulations are more pronounced under increased task demands, supporting top-down control.
• FEF plays a crucial role in modulating early sensory cortex activity, with influences enhanced by bottom-up or top-down signals.