Using images of Hollywood celebrities such as Angelina Jolie and Arnold Schwarzenegger, scientists have shown how individual neurons in the human brain react to ambiguous morphed faces.
An international team of scientists, involving Professor Rodrigo Quian Quiroga, from the University of Leicester, used images of celebrities morphed together to create an ambiguous face which test subjects were asked to identify.
The study found that for the same ambiguous images, the neurons fired according to the subjective perception by the subjects rather than the visual stimulus.
For example, a neuron originally firing to Whoopi Goldberg fired to a morph image between Goldberg and Bob Marley only when the subject identified the morphed image as Goldberg and remained silent when the subject said the very same image was Marley.
They concluded that neurons fire in line with conscious recognition of images rather than the actual images seen.
Furthermore, in most cases the neuron's responses to morphed pictures were the same as when shown the pictures without morphing.
"We are constantly bombarded with noisy and ambiguous sensory information and our brain is constantly making decisions based on such limited data," Quiroga said.
"We indeed see the face of a friend rather than the combination of visual features that compose the person's face. The neurons we report in this article fire exactly to this, to the subjective perception by the subjects, not to the features of the faces they were seeing," said Quiroga.
"In a sense, the interpretation of this result goes way back to British Empiricism and even to Aristotle. As Aristotle put it, we create images of the external world and use these images rather than the sensory stimulus itself for our thoughts. These neurons encode exactly that," said Quiroga.
"This result supports the view that these neurons play a key role in the formation of memory," he added.
The study was published in the journal Neuro.
