Luo and Maunsell used a specially designed task to show that the only effect of attention in visual cortex is to improve the signal-to-noise ratio of neurons.

Neuronal Modulations in Visual Cortex Are Associated with Only One of Multiple Components of Attention
TZ Luo, JHR Maunsell – Neuron, 2015

See highlight by Timothy J. Buschman:
Paying Attention to the Details of Attention
TJ Buschman – Neuron, 2015

About the Author

The Miller Lab uses experimental and theoretical approaches to study the neural basis of the high-level cognitive functions that underlie complex goal-directed behavior.