Goal-oriented cooperation in primates involves intricate exchanges of visual cues that guide behavior, according to a Houston Methodist Hospital-Rice University study that provides an unprecedented look at how real-time social stimuli activates brain regions.

In freely moving macaques working together for food rewards, the researchers employed wireless neural monitoring alongside eye-tracking technology to find evidence that the visual cortex sends signals to the prefrontal cortex needed to carry out desired actions.

"We are the first to use telemetric devices to record neural activity from multiple cortical populations in the visual and prefrontal cortex while animals explore their environment and interact with one another," Valentin Dragoi, PhD, the Rosemary and Daniel J. Harrison III Presidential Distinguished Chair in Neuroprosthetics at Houston Methodist and a professor of electrical and computer engineering at Rice, said in a Rice press release. "When primates, including humans, interact, we make eye contact and use body language to indicate to conspecifics what we want to do."

Study findings were published recently in Nature.

Brain research the focus of newly launched Houston Methodist-Rice center

The findings emerged from research performed in a lab of the Center for Neural Systems Restoration, a Houston Methodist-Rice interdisciplinary initiative for neuroscience research and treatment innovation launched earlier this year. Brain processes are one of the main research focus areas promoted at the center.

The center, housed at Houston Methodist, is dedicated to advancing understanding of the human brain and developing next-generation technologies, neural prosthetics and rehabilitation regimens for the treatment of neurological conditions. It brings together Rice engineers and researchers and Houston Methodist neurosurgeons, neuroscientists and regeneration biologists to tackle challenges like stroke recovery and spinal cord injury.

While previous research has identified brain regions activated by social stimuli, such as facial expressions and social ranks, understanding how visual cues influence behavior during dynamic social interactions has remained elusive.

The Rice press release noted that most knowledge about the neural underpinnings of cognition comes from studies in which restrained, isolated animals performed a task in response to artificial stimuli on a computer screen, not during actual interaction with peers in a more naturalistic environment.

"Until now, we didn't know how what we are looking at guides our decision to cooperate or not, because of our inability to measure oculomotor events and correlate them with what neurons are doing in that instant," said Dr. Dragoi, the Center for Neural Systems Restoration's scientific director. "Because the technology was not there, that knowledge was just unattainable."

In the experiment, the neural activity of two pairs of macaques was recorded as they learned to cooperate for food rewards. The pairs — both consisting of a dominant macaque and a subordinate macaque — moved freely about an enclosure, separated by a clear divider.

The macaques already had been trained to press a button to bring a snack tray within reach, but in the study the tray only moved if they pressed the button simultaneously. Recordings of their neural activity showed that as their cooperation skills improved, the frequency with which they picked up on visual cues — in their partner, in the movement of the tray — increased before they began acting in concert.

Advancing the frontiers of translational neuroscience

Tracking neural activity as animals move and behave naturally represents a significant step forward in neuroscience research and promises to reveal new insights into the inner workings of the brain.

"This has been the golden dream of neuroscientists for a long time — to record from neurons on the fly while the animal is free-moving," Dr. Dragoi said in the Rice release.

Dr. Dragoi said the research team will move on to examine how the behavior of neuronal populations underlies brain function and adaptive responses following injury or disease.

The research was supported by the National Institutes of Health.

The Center for Neural Systems Restoration is led by co-directors Dr. Gavin Britz, MD, chief of Neurosurgery at Houston Methodist, and Behnaam Aazhang, PhD, a professor of Electrical and Computer Engineering at Rice.