Keeping our eyes focused on what we’re looking for, whether it’s an item in the supermarket or the ball your trusty pup brought you, can seem transparent. But this ability is actually due to a complex neurological process that involves complex timing and coordination.
A new study fixed our eyes on the neurological mechanism behind “gaze anchoring” – the temporary stopping of eye movement in order to coordinate scopes. He discovered that neurons in the part of the brain used for reaching actually inhibit neural activity in the part of the brain used for eye movement.
This suppression of neural firing inhibits eye movement, keeping our eyes focused on the target within our reach.
“Our results show that we anchor our gaze to the target of the range motion, thereby gazing at that target for longer periods of time,” says Bijan Pesaran, a professor at the Center for Neural Science at New York University in the United States and one of the authors of the article. . “That’s what makes our scopes so much more accurate.
“The big question was, how does the brain orchestrate this kind of natural behavior?
How do you study gaze anchoring?
Neuroscientists used a non-human primate model to study gaze anchoring, training two male rhesus macaques (macaca mulatta) to perform a sequence of eye and arm movements.
The first move was a coordinated look and reach at a target. Then, as little as 10 milliseconds (ms) later, a second target was presented for the subjects to look at as quickly as possible.
These movements are similar to those performed when changing radios while driving and then focusing on a traffic light – if you quickly look away from the radio at the traffic light, you may not be selecting the correct channel ( although you may also cause an accident, so keep your eyes on the road).
Reaction times to the second target were significantly longer when it spawned within 300ms of the first target, compared to when it spawned 500-800ms later, exposing the gaze anchoring effect by keeping eyes centered on the first target.
Simultaneously, they studied the firing of neurons using multiple electrodes implanted in specific areas of the brain – the parietal reach region used to reach work and the parietal saccade region used for eye movements.
During gaze anchoring (while reaching the object), they found that neurons in the parietal involvement region suppressed neural activity in the parietal saccade region and inhibited eye movements.
Importantly, the scientists note, the effects were linked to patterns of 15-25 Hz brain waves, called beta waves, which organize neural firing in different regions of the brain.
“Beta waves have previously been linked to attention and cognition, and this study reveals how beta activity can control inhibitory brain mechanisms to coordinate our natural behavior,” says Pesaran.
This research offers the possibility of better understanding the afflictions of attention and executive control that orchestrate natural behaviors – such as coordinated gazing and reaching. It was published in Nature.