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Reward expectation differentially modulates attentional behavior and activity in visual area V4
Jalal K Baruni1, Brian Lau1, C Daniel Salzman1,2,3,4
1Department of Neuroscience, Columbia University, New York, New York, USA.
Nature Neuroscience
|October 20, 2015
Summary
Neural activity in visual area V4 is modulated by absolute reward value, not just relative attention. This suggests downstream mechanisms, rather than V4 signal-to-noise, drive attention's perceptual benefits.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Visual Neuroscience
Background:
- Neural activity in visual area V4 increases with directed attention.
- Previous studies confounded attention with reward magnitude, leaving the source of enhancement unclear.
Purpose of the Study:
- To investigate the independent effects of absolute reward value and relative attention on V4 neural activity.
- To determine the neural mechanisms underlying the perceptual benefits of spatial attention.
Main Methods:
- Monkeys were trained on a visual discrimination task with independently varied reward magnitudes per location.
- Behavioral attention was controlled using relative reward values.
- V4 neuronal activity, gamma-band power, and trial-to-trial variability were recorded.
Main Results:
- V4 neurons showed increased activity and gamma-band power with larger absolute rewards.
- Trial-to-trial variability in V4 decreased with higher absolute rewards.
- Neuronal modulation correlated with absolute reward, not relative attention.
Conclusions:
- V4 neural activity is directly modulated by absolute reward value, challenging the signal-to-noise hypothesis for attention.
- Perceptual benefits of spatial attention likely arise from downstream selection mechanisms, not enhanced V4 signal processing.
