Acetylcholine (ACh) increases the activity of neurons to detect stimuli that would be typically below an attention threshold. As such it enhances visual processing through signal amplification and may represent the biological basis underlying the process that our minds undergo in focusing attention upon something.

“That’s what attention does–it strengthens the signal you’re interested in and that strengthening helps you filter out other things” said Anita Disney of NYU, “Our findings show that acetylcholine has the ability to turn up the volume on visual activity, just like attention does.”

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Link: ScienceDaily