Learning the vibe. When people walk into a room, they take in a variety of sensory cues to navigate in a new situation. Research by Barbara Shinn-Cunningham, a CAS assistant professor of cognitive and neural systems, indicates that people learn the aud- itory terrain of a room in a relatively short time, building on their auditory experience to better locate sound emanating from an unseen source within the room.

Shinn-Cunningham and her colleagues used a Polhemus tracker, a device made up of a receiver and a transmitter, which accurately registers how well a subject, with no visual cues, identifies the point in space where a sound is produced. The researchers placed subjects in three locations in the same room: in the center, the least confusing location because there are fewer echoes from sounds bouncing off surfaces; with their backs against a wall, which produces more echoes and consequently more confusion; and in a corner, the most confusing location because of competing echoes. They found that although the subjects performed best in the center of the room, with repeated testing, accuracy improved in all three positions. Learning occurred even though subjects were given no verbal feedback about their performance. Interestingly, learning seemed to be generalized from position to position in the room. When a subject who had been in one position was moved to another, performance improved over time, independent of whether the subject was moving to an easier or to a more difficult location in the room.

"Identical experiments conducted previously in anechoic space, space in which there are no echoes or reverberation, did not produce learning," says Shinn-Cunningham. "This leads us to conclude that our results are not merely the result of practice in the skills locating sounds, but are really about learning, through experience, about the acoustics of a particular room."

A new twist on a powerful theme. Polymerase chain reaction, more commonly known as PCR, is a powerful technology that allows researchers to rapidly copy a target area on the DNA double helix many times over, providing enough material to identify individuals from minute amounts of tissue or blood, to diagnose genetic diseases, and to research evolution. Conceived in 1983 by Kary B. Mullis, development of this technology earned him a Nobel prize in 1993.

Now Charles Cantor, ENG professor and director of biomedical engineering, Senior Research Associate Natalia Broude and graduate student Lingang Zhang (ENG'05) of ENG's Center for Advanced Biotechnology (CAB), with colleagues from the Packard Instrument Company in Meriden, Conn., have devised a new PCR strategy that enables the amplification of multiple DNA targets with a simplified process that decreases the costs involved and makes the process more amenable to automation.

Traditional PCR uses two primers, synthetic DNA fragments that correspond to those that flank the target area. The CAB variant uses a single primer that is specific to the target area and another primer that is common for all targets. The common primer corresponds to adapters attached to both ends of each DNA fragment. Because the common primer is rich in two of DNA's bases, guanine and cytosine, which results in an especially strong base pair, the DNA fragments form hairpin structures, with the target DNA forming a loop. This means that only half the number of primers needs to be engineered to amplify multiple targets on a strand of DNA.

The new process not only holds the promise of more reliable amplification of multiple segments of DNA at the same time, it also is highly specific because it occurs within narrower temperature constraints than traditional PCR. In addition, Cantor and his colleagues believe their new form of multiplex PCR may prove to be effective in amplifying SNP (single nucleotide polymorphisms), genomic areas considered to be associated with inheritable diseases. SNP scoring will provide more knowledge about the hereditary aspects of these diseases, and consequently new ways of preventing or treating them.

This work was presented in the January 2, 2001, issue of The Proceedings of the National Academy of Sciences.