Jun 2, 2017

Only a few hundreds neurons help the brain recognize faces

Doris Tsao / Caltech

Researchers believe they've cracked the code for how primates are able to recognize faces. And, it may be relatively simple: only 200 neurons or so in the brain appear to be responsible for the ability of macaque monkeys to identify the faces of humans that they know over those of complete strangers.

Why it matters: Humans and other primates are thought to use a similar face recognition system, so understanding how images are encoded by the neurons could inform the development of artificial vision.

The question: Researchers had previously identified six parts of the brain (in a place called the inferior temporal cortex) that were responsible for identifying faces. Specific nerve cells in these six regions of the brain respond more strongly when we see faces compared to objects. What scientists didn't know was the exact combination of these "face cells" required to identify those we know from strangers.

The study: Researchers inserted electrodes into the brains of macaque monkeys in the six regions. They then mapped various features of faces (like the distance between eyes) onto a grid and used them to create 2000 photos of manipulated human faces. When they were shown to the monkeys, just 205 neurons from two of the six regions where "face cells" exist activated. Using the pattern of neuron activation, the researchers were then able to reconstruct the faces the monkey was looking at.

Fun quote: "People always say a picture is worth a thousand words. But I like to say that a picture of a face is worth about 200 neurons." —Doris Tsao, professor of biology and biological engineering at the California Institute of Technology.

Go deeper

Hong Kong police fire pepper pellets at demonstrators

Hong Kong riot policeissue a warning as they aim to clear away people gathered downtownon Wednesday. Photo: Anthony Wallace/AFP via Getty Images

Hong Kong riot police have fired pepper pellets at activists and surrounded the Legislative Council during demonstrations against a bill proposing to criminalize "disrespect of the Chinese anthem" on Wednesday, per Reuters.

Why it matters: The bill is the latest concern pro-democracy protesters have that Chinese authorities are encroaching on the high degree of autonomy the former British colony has retained since it was returned to China in 1997.

Minneapolis unrest as hundreds protest death of George Floyd

Tear gas is fired as police clash with protesters demonstrating against the death of George Floyd outside the 3rd Precinct Police Precinct in Minneapolis, Minnesota, on Tuesday. Photo: Stephen Maturen/Getty Images

Minneapolis police used tear gas during clashes with protesters demanding justice Tuesday night for George Floyd, an African American who died in police custody, according to multiple news reports.

Driving the news: The FBI is investigating Floyd's death after video emerged of a Minneapolis police officer kneeling on his neck for several minutes, ignoring protests that he couldn't breathe. Hundreds of protesters attended the demonstration at the intersection where Floyd died, per the Guardian.

U.S. coronavirus updates

Data: The Center for Systems Science and Engineering at Johns Hopkins; Map: Andrew Witherspoon/Axios. This graphic includes "probable deaths" that New York City began reporting on April 14.

Virginia Gov. Ralph Northam announced plans Tuesday to make wearing face coverings mandatory statewide for most people over the age of 10 when inside public places like retailers, on public transportation and government buildings. He announced the measure, effective Friday, as coronavirus case numbers increased to 39,342.

By the numbers: More than 98,900 people have died from COVID-19 and over 1.6 million have tested positive in the U.S. Over 384,900 Americans have recovered and more than 14.9 million tests have been conducted.