How Do We Perceive Sound?
Tony Zador is the Professor of Biology and Program Chair in Neuroscience at Cold Spring Harbor Laboratory. There he uses a combination of physiological, molecular, behavioral and computational approaches to study the neural mechanisms underlying auditory processing, attention and decision making in rodents. Zador's pedigree includes graduate work with Caltech professor Christof Koch, Yale professor Tom Brown, and postdoctoral work with Chuck Stevens of the Salk Institute. Zador is also the co-founder of the annual Computational and Systems Neuroscience (COSYNE) meeting, which now draws over 500 participants.
Question: How does sound travel from the ear to the brain?
Tony Zador: So actually we know a lot about the early stages of auditory processing. We know that there are sound waves. They are propagated down into a structure in your ear called the cochlea. Within that structure there are neurons that are exquisitely sensitive to minute changes in pressure. They are sensitive to those changes at different frequencies, so actually what your cochlea does is it acts as what is called a spectral analyzer, so there are some neurons that are sensitive to low frequency sounds and other neurons that are sensitive to middle frequency and other neurons that are sensitive to high frequency and each one of those is coded separately along a set of nerve fibers, then they’re passed through a bunch of stages in your auditory system before they get to your cortex, so the last stage... So I’ll say that what is interesting is that the stages of processing a sound are incredibly different as you might imagine from the stages of processing a visual scene, so those stages that I just told you are designed for processing physical vibrations between the ranges in a human of 20 hertz to 20 kilohertz. We have eyes that aren’t responsible for transducing sound vibrations, but rather, light. And you know the structure of the retina is also well understood. There are photoreceptors that pick up photons and transmit those signals, but what is interesting is that once those signals get processed or, if you like, preprocessed they end up in structures that now look remarkably similar. A structure called the thalamus and there is a part of the thalamus that receives input from the auditory system, another part of the thalamus that receives input from the visual system, from the retina, and then after it gets to the thalamus it goes to the cortex and within the cortex the signals now look very similar.
And so what seems to be the case is that there is this preprocessor in the... on the auditory side, on the visual side and actually all your sensory modalities that’s highly specialized for the kind of sensory input we have, but then it converts it into sort of a standard form that gets passed up to the cortex, so what we actually believe is that if that the mechanisms of auditory attention are actually not probably fundamentally different from the mechanisms of any other kind of attention, including visual attention.
Recorded August 20, 2010
Interviewed by Max Miller
Neuroscientist Tony Zador explains how a sound wave is converted into neural signals that the brain can understand and speculates about the role of auditory attention in this process.
What do we see from watching birds move across the country?
- A total of eight billion birds migrate across the U.S. in the fall.
- The birds who migrate to the tropics fair better than the birds who winter in the U.S.
- Conservationists can arguably use these numbers to encourage the development of better habitats in the U.S., especially if temperatures begin to vary in the south.
Explore how alcohol affects your brain, from the first sip at the bar to life-long drinking habits.
- Alcohol is the world's most popular drug and has been a part of human culture for at least 9,000 years.
- Alcohol's effects on the brain range from temporarily limiting mental activity to sustained brain damage, depending on levels consumed and frequency of use.
- Understanding how alcohol affects your brain can help you determine what drinking habits are best for you.
If you want to know what makes a Canadian lynx a Canadian lynx a team of DNA sequencers has figured that out.
- A team at UMass Amherst recently sequenced the genome of the Canadian lynx.
- It's part of a project intending to sequence the genome of every vertebrate in the world.
- Conservationists interested in the Canadian lynx have a new tool to work with.
If you want to know what makes a Canadian lynx a Canadian lynx, I can now—as of this month—point you directly to the DNA of a Canadian lynx, and say, "That's what makes a lynx a lynx." The genome was sequenced by a team at UMass Amherst, and it's one of 15 animals whose genomes have been sequenced by the Vertebrate Genomes Project, whose stated goal is to sequence the genome of all 66,000 vertebrate species in the world.
Sequencing the genome of a particular species of an animal is important in terms of preserving genetic diversity. Future generations don't necessarily have to worry about our memory of the Canadian Lynx warping the way hearsay warped perception a long time ago.
Artwork: Guillaume le Clerc / Wikimedia Commons
13th-century fantastical depiction of an elephant.
It is easy to see how one can look at 66,000 genomic sequences stored away as being the analogous equivalent of the Svalbard Global Seed Vault. It is a potential tool for future conservationists.
But what are the practicalities of sequencing the genome of a lynx beyond engaging with broad bioethical questions? As the animal's habitat shrinks and Earth warms, the Canadian lynx is demonstrating less genetic diversity. Cross-breeding with bobcats in some portions of the lynx's habitat also represents a challenge to the lynx's genetic makeup. The two themselves are also linked: warming climates could drive Canadian lynxes to cross-breed with bobcats.
John Organ, chief of the U.S. Geological Survey's Cooperative Fish and Wildlife units, said to MassLive that the results of the sequencing "can help us look at land conservation strategies to help maintain lynx on the landscape."
What does DNA have to do with land conservation strategies? Consider the fact that the food found in a landscape, the toxins found in a landscape, or the exposure to drugs can have an impact on genetic activity. That potential change can be transmitted down the generative line. If you know exactly how a lynx's DNA is impacted by something, then the environment they occupy can be fine-tuned to meet the needs of the lynx and any other creature that happens to inhabit that particular portion of the earth.
Given that the Trump administration is considering withdrawing protection for the Canadian lynx, a move that caught scientists by surprise, it is worth having as much information on hand as possible for those who have an interest in preserving the health of this creature—all the way down to the building blocks of a lynx's life.
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