New research using bats gives an intriguing insight into how mammals focus their attention.
For the entirety of our waking lives, our senses are bombarded by sensory stimulation.
It is easy to forget how much information flows through our senses every second of the day; our brains are so astute at presenting our consciousness with only the information that is important to us.
For instance, as you read this, you are probably seated. Your nether regions are nested against a chair, and your body weight is pushing down on your buttocks.
When you focus on this fact, you can feel the weight bearing down on your gluteus maximus. But before this was brought to your attention, that information was far from your focus.
Perhaps, if you are lucky, and you strain your ears, you can hear some distant birds. Until you consciously listen for them, however, their songs are as good as absent.
The mammalian brain is excellent at prioritizing inputs to ensure that the world is presented to us in a way that we can handle. If we were to focus on every single item that our senses detected, we would surely go mad.
Researchers at Johns Hopkins University have made new discoveries in the brains of bats that help us to understand how mammals pay such laser-guided attention.
Bats and sonar
Bats hunt by making sounds, then listening to them as they bounce back off any objects in front of them. This incredible use of sonar allows them to hunt during the darkest hours, a time when insects are off their guard and they can hunt in relative safety.
To use echolocation, the bats must be able to distinguish the echoes that their vocalizations make among a field of extraneous noise, including other bats' calls and their echoes, insects, trees, aircraft and cars.
Lead author Melville J. Wohlgemuth, a postdoctoral fellow in the Krieger School of Arts and Sciences' Department of Psychological and Brain Sciences, says:
"The bat brain has developed special sensitivities that allow it to pick out sounds from the environment that are pertinent to the animal. We were able to uncover these sensitivities because we used the perfect stimulus - the bat's own vocalizations."
Wohlgemuth and co-author Cynthia F. Moss, a Johns Hopkins professor and neuroscientist, set out to understand which sounds bats deemed important enough to pay attention to; they wanted to discover what kind of noise would be of enough interest to make the bats orient toward the sound.
Brain scans and the superior colliculus
The researchers used five big brown bats (Eptesicus fuscus), playing them a selection of different sounds while monitoring the activity in a specific section of their midbrain known as the superior colliculus.
The superior colliculus (SC) is known to play a role in collating sensory information and issuing the correct motor response, for instance, moving away from a threatening sound or toward one that sounds like food.
The researchers played bats a series of sounds, from natural vocalizations produced during a hunt, to white noise, and a selection of sounds ranging between the two extremes. All of the noises were equal in amplitude, bandwidth and duration.
The team found that the sensorimotor neurons in the ventral region of the SC responded to all of the sounds that were played, artificial or bat-based; however, neurons in the dorsal sensory regions of the SC only responded to natural bat-produced hunting sounds.
The following video from Johns Hopkins explains the experiment:
Relevance to human attention
Because mammalian brains have great inter-species similarities, these findings are probably relevant for the human brain, too. The superior colliculus is known to be involved in directing eye movements in humans; Medical News Today asked Wohlgemuth whether the results might have implications for visual attention as well as sound, and he said:
"The superior colliculus is a multimodal structure that uses visual, auditory and somatosensory information to control orienting motor responses.
I believe that the results we found for auditory selectivity do indeed apply to other sensory systems, such as selecting a stimulus for visual orientation."
MNT asked Wohlgemuth whether he will continue his research into this most fascinating of mammals. He next plans to investigate bats while hunting prey items; his "future experiments will involve examining how the bat processes the actual sensory information being used for target tracking."
This fascinating and, at first, intractable area of neuroscience may soon yield more of its secrets. MNT recently covered research on the effect of flame retardants on children's attention spans.