In 2005, Nintendo debuted Brain Age, a handheld video game console claiming to improve brain function "in minutes a day."  Since then, a collection of computer and video games purporting to improve cognitive fitness, known as "brain training," have become popular as a way to maintain healthy brain function into old age.  Brain training start-ups such as Cognifit, Jungle Memory, and Lumosity claim that the games will improve memory and help prevent the dementia caused by brain diseases such as Alzheimer's disease. However, no scientific consensus exists on the benefits of such mental fitness apps and computer games. Nevertheless, brain training continues to enjoy a popular following among consumers and investors alike.

What is brain training, anyway?

The brain operates by a "use it or lose it" principle – the better proficiency you develop in performing a task, the more neuronal pathways that task recruits in order to better support the complex processing related to that task. Brain training, utilizing this principle, seeks to improve aspects of attention, memory, sensory processing, and reasoning. The "training" itself involves playing computer and mobile games that target these systems.

Lumosity: from the lab bench to the palm of your hand

Ranked #66 on Forbes' list of America's Most Promising Companies, the San Francisco-based Lumosity may be the most well-known of the brain training start-ups.  Lumosity reached 35 million users this year, and their mobile app is #1 in the iTunes App Store's "Education" category, with over 50,000 downloads a day.

Lumosity was founded in 2005 by Kunal Sarkar, Michael Scanlon, and David Drescher to fill a void in the health and exercise market: software seeking to improve brain function. The company launched in 2007, receiving $400,000 from angel investors . In 2008, Lumosity received $3 million in Series B funds from Norwest Venture Partners, FirstMark Capital, and Harrison Metal Capital. In 2011, Lumosity raised $32.5 million from Menlo Ventures and prior investors, and TechCrunch  reported in August 2012 that the company had raised an additional $31.5 million in financing from Discovery Communications (DISC.A) .

Lumosity's revenue is driven largely by its online and mobile brain training games. For $14.95 a month, subscribers can play a variety of games testing memory, attention, mental speed, mental flexibility, and problem solving. The company also conducts research on brain training through the Human Cognition Project, which includes a network of over 1,500 international researchers and is primarily focused on developing more effective training programs.

Lumosity's brain training games have enjoyed a popular following by health-conscious individuals and educators. More than 40 million members use the website and mobile games. The company's mobile app, which has been downloaded over 10 million times, offers a variety of games to improve attention and focus.

Do brain training programs work?

Several peer-reviewed research studies have indicated that users of Lumosity benefit from an increase in cognitive performance. However, these studies have been limited to small samples of participants, including patients suffering from cognitive and behavioral deficits due to cancer therapy, traumatic brain injury, and Turner syndrome.

Currently, no scientific consensus exists regarding the efficacy of brain training software. In his recent article in the New Yorker, "Brain Games are Bogus," Pulitzer Prize-winning science writer Gareth Cook reviewed several studies of brain training, suggesting that cognitive fitness programs, in their current state, may not be as effective as advertised. Randomized, controlled studies on a large scale that test the effect of Lumosity software in healthy individuals over time are required before the effects of the software can be understood in the general population.

Is brain training just another fad?

Well, yes and no. While some scientific evidence supports the utility of cognitive training programs to improve attention and memory, the evidence is sparse and the known benefits of brain training are limited. Researchers at the University of Amsterdam suggest that, in the future, the most effective brain training programs will have three core components including novelty, a focus on decision-making and memory strategies, and forms of training tailored to the individual.

Cook argues that the time spent on brain training apps could be better used in other ways – exercising, for instance – which is also known to boost brain function.