Scientists in Texas used a brain scanning technique to carry out a hi-tech version of the Pepsi challenge and found that, when it comes to fizzy black drinks, brand love is just as important as taste.

Neuroscientist Read Montague carried out the research almost a year ago at the Baylor College of Medicine in Houston. Volunteers were scanned by functional magnetic resonance imaging (fMRI), which can identify activity in different parts of the brain, while they blindly drank either Coke or Pepsi and told scientists which they preferred.

The results, which Professor Montague intends to publish soon in a scientific journal, show that different parts of the brain "light up", depending on the type of cola being drunk.

His team found that a brain region called the ventral putamen - associated with seeking reward - was highly active when people blindly drank their favourite cola.

However, things changed when volunteers were told what they were drinking. This time, Coke was the undisputed king and a different part of the brain was seen to be more active by the fMRI scans.

The medial prefrontal cortex, an area of the brain associated with higher thinking processes, was being used when volunteers knew what they were drinking. According to New Scientist magazine, where the results are reported today, this shows that people make decisions based on their memories or impressions of a particular drink, as well as taste.

The research will come as welcome news to advertisers, for whom "brand recognition" among consumers is a highly valued commodity. The research is also the latest in the field of so-called "neuromarketing", which digs deep into consumers' minds in an attempt to work out what they like and why they like it.

Stephen Quartz, a neuroscientist at the California Institute of Technology, recently pioneered the use of neuromarketing to improve movie trailers to fit the subconscious desires of moviegoers.

He put 40 volunteers into his fMRI scanner and tested their brain reactions as he projected films such as Casablanca and Good Will Hunting on to a mirror suspended above their eyes. Professor Quartz has sold the technique to film companies and said that it will help studios predict blockbusters.