Coffee kickstarts many a sleepyhead's day, but a new study argues that it's not the caffeine alone that provides the morning wake-up.

People who took a basic caffeine pill did not experience the same sort of brain boost they did from sipping a cup of coffee, according to brain scans.

Caffeine alone does activate some regions of the brain associated with readiness to tackle tasks, the researchers said.

But the act of drinking coffee produced a more comprehensive response in the brain, the results showed.

"Taking into account that some of the effects that we found were reproduced by caffeine, we could expect other caffeinated drinks to share some of the effects," said lead researcher Maria Picó-Pérez, a postdoctoral researcher with Jaume I University in Spain. "However, others were specific for coffee drinking, driven by factors such as the particular smell and taste of the drink, or the psychological expectation associated with consuming that drink."

For the study, researchers recruited a group of people who typically drink at least one cup of coffee daily. They asked these folks to refrain from eating or drinking caffeinated beverages for at least three hours before going into the lab.

Researchers then performed two brief functional MRI (fMRI) scans, one before and another a half-hour after the participant took either a caffeine pill or drank a cup of coffee.

During the fMRI scans, the participants were asked to relax and let their mind wander.

Because of the known effects of drinking coffee, the scientists expected that the participants would experience a higher integration of networks that are linked to the prefrontal cortex (which is associated with executive memory) and the default mode network (which is involved in introspection and self-reflection processes).

The connectivity of the default mode network decreased both after drinking coffee and after taking caffeine, which indicates that consuming either made people more prepared to move from resting to working on tasks, the researchers said.

But only drinking coffee increased connectivity in parts of the brain associated with working memory, cognitive control and goal-oriented behavior, the results showed.

So if a person wants to feel not just alert but ready to get things done, caffeine alone won't do the trick, the researchers concluded. The experience of a cup of coffee is essential.

The study was published June 28 in Frontiers in Behavioral Neuroscience.

"In simple words, the subjects were more ready for action and alert to external stimuli after having coffee," Picó-Pérez said in a journal news release.

The study authors pointed out that it is possible that drinking decaffeinated coffee might also produce these benefits, in which case coffee drinking would be acting as a placebo. The study could not differentiate the effects of the experience alone from the experience combined with the caffeine.

Another potential explanation could be that the benefits coffee-drinkers claim are actually due to the relief of withdrawal symptoms, the researchers added.

"Moreover, there could be individual differences in the metabolism of caffeine among participants that would be interesting to explore in the future," said co-researcher Dr. Nuno Sousa of the University of Minho in Portugal.