Feature-based attention modulates direction-selective hemodynamic activity within human MT.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Visual Perception

Background:

• Feature-based attention modulates neural activity in sensory cortices.
• In area V5/MT, attention to motion direction increases firing of tuned neurons and suppresses others.
• Integration of these single-neuron responses at the population level remains unclear.

Purpose of the Study:

• To investigate how feature-based attention influences population-level neural responses in human visual cortex.
• To test the validity of the feature similarity gain model in explaining attention-modulated population responses.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to measure brain activity.
• Participants attended to specific movement directions of a dot field stimulus.
• Stimulus coherence was varied to assess its interaction with attention.

Main Results:

• Attending to a movement direction enhanced responses in the human MT region (hMT) proportionally to stimulus coherence.
• Attending to the opposite direction suppressed hMT responses inversely to stimulus coherence.
• These results indicate enhanced direction-selective population responses modulated by attention.

Conclusions:

• Multiplicative scaling of single-neuron responses by attention leads to enhanced direction-selective population responses.
• Findings support the feature similarity gain model for integrated population responses in humans.
• Parametric fMRI provides a method to quantify these effects.