Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fixating on faces

26.01.2017

When we are walking down a crowded street, our brains are constantly active, processing a myriad of visual stimuli. Faces are particularly important social stimuli, and, indeed, the human brain has networks of neurons dedicated to processing faces. These cells process social information such as whether individual faces in the crowd are happy, threatening, familiar, or novel.

New research from Caltech now shows that the activation of face cells depends highly on where you are paying attention--it is not enough for a face to simply be within your field of vision. The findings may lead to a better understanding of the mechanisms behind social cognitive defects that characterize conditions such as autism.


Dots represent locations of electrodes in the amygdala region of the brain. Each electrode measured activity of a single brain cell.

Credit: J. Minxha/Adolphs lab

The research was conducted in the laboratories of Ralph Adolphs (PhD '93), Bren Professor of Psychology and Neuroscience and professor of biology, and collaborator Ueli Rutishauser (PhD '08) of Cedars-Sinai Medical Center in Los Angeles and a visiting associate in biology and biological engineering at Caltech.

A paper about the work appears in the January 24 issue of Cell Reports.

... more about:
»human face »monkeys »species

"The ability to recognize other human faces is the basis of social awareness and interaction," Adolphs says. "Previous work on this subject has typically been conducted under rather artificial conditions--a single, large image is displayed on a monitor in front of a subject to focus on. We wanted to understand how brain activity changes with eye movements and capture the natural dynamics of how people constantly shift their attention in crowded scenes."

The researchers focused on face cells in a particular region of the brain called the amygdala.

"We know that a damaged amygdala can result in profound deficits in face processing, especially in recognizing emotions, but how amygdala neurons normally contribute to face perception is still a big open question," says Juri Minxha, a graduate student in Caltech's computation and neural systems program and lead author on the paper. "Now, we have discovered that face cells in the amygdala respond differently depending on where the subject is fixating."

When a face cell responds to a stimulus, it fires electrical impulses or "spikes." By working with patients who already had electrodes implanted within their amygdalae for clinical reasons, the group measured the activity of individual face cells while simultaneously monitoring where a subject looked. Subjects were shown images of human faces, monkey faces, and a variety of other objects such as flowers and shapes. This study is the first in which subjects were free to look around at various parts of a screen and focus their attention on different things.

The study found two types of face cells: those that fire more spikes when the patient is looking at a human face and those that fire a few spikes when the patient is looking at a face of another species (in this case, that of a monkey). Neither type of face cell fired when the subjects were paying attention to objects that were not faces, even if those objects were near a face in the image.

"We saw that if a person was paying attention to a flower picture, for example, the face cells would not fire even if the flower was close to a face," says senior author Rutishauser. "This suggests that the responses of face cells are controlled by where we are focusing our attention."

Experiments in monkeys, performed in collaboration with Katalin Gothard of the University of Arizona, showed similar results. In both groups of subjects, face cells were most responsive to conspecifics--faces of the same species. "This is remarkable because many aspects of social perception and social behavior are different between the two species," Gothard says. "This discovery now indicates that the primate amygdala is an integral part of the network of brain areas dedicated to processing the faces we pay attention to, and is the first such direct comparison between humans and monkeys."

The studies showed that when the monkey and human subjects were viewing images of the same species, the monkeys' face cells reacted about one-tenth of a second more quickly than the face cells of humans, validating a long-standing hypothesis that face cells in monkeys would respond more quickly than corresponding cells in humans. The tenth-of-a-second difference is larger than what can be explained by variation in human and monkey brain size, leaving open the question of why human face cells have a delayed response. "The power of this comparative approach is that it identifies critical differences in brain function that might be unique to humans," Rutishauser says.

"The experimental design brings researchers a step closer to studying how the brain works during natural behaviors," Minxha says. "Ideally, we would want to observe neural activity while a person actually moves through a crowded scene. The next step is to study how face-cell activation changes with the subject's emotional state, or when they are interacting with someone. We would also like to understand how face-cell responses are different in subjects with specific clinical disorders, such as in people with autism, which is work we have been conducting as well."

###

The paper is titled "Fixations gate species-specific responses to free viewing of faces in the human and macaque amygdala." Other co-authors include Clayton Mosher and Jeremiah Morrow of the University of Arizona and Adam Mamelak of Cedars-Sinai Medical Center. The work was funded by the National Science Foundation, the National Institute of Mental Health, the McKnight Endowment Fund for Neuroscience, and a NARSAD Young Investigator Award from the Brain and Behavior Research Foundation.

Media Contact

Lori Dajose
ldajose@caltech.edu
626-658-0109

 @caltech

http://www.caltech.edu 

Lori Dajose | EurekAlert!

Further reports about: human face monkeys species

More articles from Social Sciences:

nachricht Illinois researchers researchers find tweeting in cities lower than expected
21.02.2018 | University of Illinois College of Engineering

nachricht Polluted air may pollute our morality
08.02.2018 | Association for Psychological Science

All articles from Social Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

Im Focus: The Future of Ultrafast Solid-State Physics

In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.

Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...

Im Focus: Stronger evidence for a weaker Atlantic overturning

The Atlantic overturning – one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards – is weaker today than any time before in more than 1000 years. Sea surface temperature data analysis provides new evidence that this major ocean circulation has slowed down by roughly 15 percent since the middle of the 20th century, according to a study published in the highly renowned journal Nature by an international team of scientists. Human-made climate change is a prime suspect for these worrying observations.

“We detected a specific pattern of ocean cooling south of Greenland and unusual warming off the US coast – which is highly characteristic for a slowdown of the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

New capabilities at NSLS-II set to advance materials science

18.04.2018 | Materials Sciences

Strong carbon fiber artificial muscles can lift 12,600 times their own weight

18.04.2018 | Materials Sciences

Polymer-graphene nanocarpets to electrify smart fabrics

18.04.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>