How does our brain see the world? Most people would say through our eyes. Then, they would possibly describe how the eye works. How light enters the eye through the cornea, and the cornea and lens refract the light rays to produce a sharply focused image on the retina. How the iris can open or close to control the amount of light that reaches the retina. How the retina is made up of three main layers: the rods and cones, the bipolar cells, and the ganglion cells, whose axons make up the optic nerve. But this is only a probability if they researched or studied the eye.
Our brain’s visual system consists of a dorsal pathway and a ventral pathway also known as the where and what pathway. A normally functioning brain can indicate motion from still pictures, such as the speed line in cartoons meant to show motion streaks of a still object. On the contrary, patients with lesions to the dorsal pathway know where objects are but have difficulty recognizing them, while patients with lesions to the ventral pathway have trouble recognizing objects but no problem locating them. The responsiveness of the human visual system for detecting motion cues is a critical evolutionary advantage, in this modern day and age where there is constant change, activity and progress.
Akinetopsia is a rare condition where a person has the inability to perceive motion. L.M. who developed this disorder, because of a blood clot in her brain, was diagnosed at the age of 43. She was unable to perceive motion, even though other aspects of her vision such as: her ability to recognize objects, to see color, or to discern detail in a visual pattern, seemed to function normally. Due to her Akinetopsia, she can detect an object now is in a different position from the position it was in a moment ago, but she reported not seeing anything in between these positions. For people diagnosed with Akinetopsia like L.M., it is difficult to do day to day things such as crossing the street because they can’t tell if a car is moving or how fast it is changing positions. They perceive objects as a series of stills.
Zhengang Lu, a doctoral student in Psychological and Brain Sciences at Dartmouth College, have revealed how the brain understands motion and still objects to help navigate our complex visual world. The findings have a number of potential practical applications, ranging from treatment for motion blindness to improved motion recognition algorithms used in airport and other public security systems. Lu and his colleagues studied neural activity to understand how the brain processes motion in still pictures of objects. They found that the brain may process motion differently based on whether the motion is inanimate or animate. This suggests that the brain not only categorizes objects into these two categories but that the brain knows it location as well. Lu says “Our results might not be able to provide treatment directly, but they suggest that treatment for people with motion blindness should consider the functional interaction between these two pathways.”
Zhengang Lu, Xueting Li, Ming Meng. Encodings of implied motion for animate and inanimate object categories in the two visual pathways. NeuroImage, 2016; 125: 668 DOI: 10.1016/j.neuroimage.2015.10.059