Image copyright RUSSELL KIGHTLEY/SPL Image caption The Human Brain Project aims to integrate what we know about the billions of cells inside our heads

Senior neuroscientists have attacked the Human Brain Project, a billion-pound European Commission initiative aiming to simulate the human brain.

An open letter to the EC from over 200 scientists says the project is "not on course", pre-empting a scheduled review.

They ask that the review be transparent and carried out by top neuroscientists not affiliated with the HBP.

If the letter is not heeded, they have pledged to boycott associated funds.

The project's figurehead, Prof Henry Markram from the EPFL (Ecole Polytechnique Fédérale de Lausanne) in Switzerland, says the criticisms are "premature" and likens the debate to the backlash faced by the Human Genome Project.

Instead of sequencing all of our DNA, the Human Brain Project aims to compile what we know about brain cells and networks and use a new generation of supercomputers to model how the brain functions.

The failure to include the opinions of most of the neuroscience community is huge Dr Zachary Mainen, Director, Champalimaud Neuroscience Programme, Portugal

The ten-year scheme was announced in 2013, months before the US launched a related initiative to map the brain's connections on an unprecedented scale.

"We're dealing here with a new paradigm," Prof Markram told the BBC. "Every new paradigm comes with this kind of difficulty, as some fight the inevitable change."

But the authors of the open letter claim the focus of the HBP is too narrow and point to a "lack of flexibility and openness" in its implementation.

Conflicting accounts

The request for independent, eminent neuroscientists to review the project stems partly from the fact that its inception was settled by a 25-member committee that selected the HBP, alongside the Graphene Flagship, to receive up to 1 billion euros from the EC. Opponents describe that panel as a "secret jury" but Prof Markram insists his project "could not have been more rigorously reviewed".

Dr Zachary Mainen, the Director of the Champalimaud Neuroscience Programme in Portugal, has withdrawn from the HBP and helped orchestrate the letter. He says concern is widespread both inside and outside the project.

"The fact is, it's not very transparent - a lot of people are [annoyed]. It'd be nice to figure out why, and try to do it better," he told BBC News. "There's just a crazy degree of resentment and distrust."

"They've gotten rid of anyone who objected to anything that they wanted to do."

In particular, the letter protests against recent changes to the project, claiming its scope has been further narrowed and one of its key strands removed. That strand focussed on cognition: higher-order brain processes, like thinking and decision-making.

Prof Markram denies this interpretation. "Those projects are still there, their leader is there," he said. "Cognition is a crucial part of this whole thing."

Last year there were 100,000 peer-reviewed papers on the brain. What we're missing is a plan, to work with all the data that we're generating Prof Henry Markram, Professor of Neuroscience, EPFL, Switzerland

He also does not share the concern that such a large project will take funding away from smaller, more varied neuroscience projects. The project's core funding, he points out, comes from information technology funding sources.

"It's a computing project," he said. "The money doesn't even come from neuroscience."

Pent-up frustration

This is sleight of hand, according to Dr Mainen. "The project was sold as neuroscience - the public associates it with understanding the human brain," he said.

Dr Mainen also points out that alongside the 50 million euros the HBP receives from the European Commission each year, 50 million is sourced for "partner projects", predominantly from member states' science budgets. "That is not money that was set aside for information technology," he said.

He and the letter's other signatories, including several many prominent UK neuroscientists, favour individual project grants over the HBP's centralised spending, which they see as opaque, restrictive and poorly managed.

The project's leaders, on the other hand, say they are offering much-needed integration. "Last year there were 100,000 peer-reviewed papers on the brain," Prof Markram said. "Take [our] 50 million euros, it's going to get you another 200, maybe 500 papers. Is that suddenly going to make the difference? What we're missing is a plan, to work with all the data that we're generating."

Prof Markram views the HBP as a "service provider", building a unified resource for others to use. "On month 30 of the project, two years from now, this platform opens to the public," he said. "We will release it - it's on schedule."

But Dr Mainen, and others, want more oversight, sooner. "The failure to include the opinions of most of the neuroscience community is huge," he said, adding that it had led to "pent-up frustration".

"This took three days, to get 150 signatures - it was absolutely trivial."