It is common in the scientific world to take primates as a point of reference in research, especially to understand how the brain can process information in its environment and make quick decisions. When a visual stimulus appears before our eyes, a network of neurons collects the data, evaluates the options and triggers a response within half a second. But now we see the birds play in another league.
They insult us. Even though we think that our brain’s processing power is virtually perfect, the reality is that the crow “tells us” that this is not the case. This conclusion was reached by a group of researchers who published their work science, demonstrated that, faced with the same visual task, these birds performed with astonishing speed that left primates behind.
How they did it. To measure the processing speed of these birds, the team adapted one of the most famous tests in perceptual neurophysiology, the random dot motion discrimination task. This test, which was very popular with primates in the early 2000s, places the subject in front of a screen where a group of dots move randomly, while only a certain percentage move coherently to the left or right.
Now, the crows were placed in front of a touch screen and after the dots appeared, the birds had to turn their heads and peck at a target that indicated the direction of motion. With clear cues, crows’ accuracy was close to 100%, and even in the most difficult and diffuse movement patterns, their decisions often exceeded chance.
Results. What was interesting was not the accuracy, but the time from the appearance of the visual cue to the onset of head turning, which was set at an average of 235 milliseconds. In an identical version of this same experiment, macaques typically take between 410 and 600 milliseconds to initiate a response, so the difference is substantial.
The prefrontal cortex. The finding is more interesting if we focus on the brain anatomy of crows, as they lack the stratified cerebral cortex of mammals. Instead, they created a functionally equivalent structure called nidopallium caudolaterale (NCL) that contains neurons capable of encoding abstract rules and even correlates of sensory awareness.
By recording from single neurons in the NCL as the birds performed the task, the researchers observed the internal dynamics of the decision process. The information points to neurons that are highly selective of the direction chosen, with firing rates increasing as the strength of what appears on the screen increases.
The reason? To understand how it is possible for such a small brain to be so fast, the first hypothesis points to neuronal density. Here, a study published in 2016 found that parrots and passerines house forebrains with twice as many neurons on average as primate brains of the same mass. Added to this packing is the body temperature of birds, which is significantly higher than that of mammals, which accelerates the metabolic rate and speed of transmission of nerve impulses.
Similarly, research from the University of Bochum has shown that the avian sensory forebrain is reminiscent of the microcircuits of the mammalian neocortex, providing optimal structural support for rapid computation.
Picture | Siegfried Poeperl
In Xataka | European bees have lost a third of their territory in a century. And climate change is not the main culprit
