By Adrian Galbreth
Until now, the brain's ability to create a three-dimensional (3D) representation from an object's two-dimensional projection on the retina is something that has not been well understood.
Although many people take it for granted, how the process occurs is not well known and is likely to be highly complex, but now new research published by Cell Press in the journal Neuron sheds light on the process.
It provides the first direct evidence that specific brain areas underlie perception of different 3D structures and highlights the way that the primate brain reconstructs real-world objects.
Senior study author Dr Peter Janssen, from the Catholic University Leuven in Belgium, where the study was carried out, explained that previous research has implicated certain regions as playing a role in 3D processing.
"One candidate for a brain area that could be involved in 3D-structure perception is the inferotemporal (IT) cortex. The IT cortex contains shape-selective neurons that demonstrate selectivity for relatively simple 3D structures, such as convex (curved out) or concave (curved in) surfaces," the expert added.
Researchers interested in investigating the specific role of IT neurons in 3D perception, by using rhesus monkeys that had been trained to report which 3D structure they perceived.
The experts electrically stimulated clusters of IT neurons that had a particular 3D-structure preference (convex or concave) while the monkeys were categorising 3D structures as either convex or concave and observed the results.
Remarkably, stimulation of a particular cluster of neurons could cause the monkeys to choose the 3D structure preferred by those neurons, while stimulation also accelerated the time it took to choose the preferred structure but delayed the choice of the non-preferred structure.
When taken together, Dr Janssen said the results demonstrated that electrical stimulation of specific clusters of IT neurons profoundly and predictably influenced both the monkey's choices and the time taken to reach those decisions.
"To our knowledge, our findings provide the first evidence relating a specific brain area directly to 3D-structure perception. These observations advance the understanding of how the brain reconstructs the 3D world by demonstrating a causal involvement of IT in the perception of different 3D structures," he added.
by Alexa Kaczka