Music, language may meet in the brain.

Corresponding left- and right-brain areas that are considered crucial for understanding spoken language also orchestrate the perception of musical passages, according to a study in the May NATURE NEUROSCIENCE.

These brain regions deal with implicit rules that organize complex information, such as music and language, theorizes a team of neuroscientists led by Burkhard Maess of the Max Planck Institute of Cognitive Neuroscience in Leipzig, Germany.

Music principles function much as grammatical rules in language do, Maess' group says. For instance, music theorists hold that certain chord sequences in the same key fit harmonically better than others, at least in Western classical music. Moreover, musically untrained listeners usually agree with the theorists about whether or not chord sequences sound musical.

The researchers used a technique called magnetoencephalography (MEG) to measure magnetic fields produced by the brain's electrical activity in six volunteers as they listened to brief sequences of chords. Some of the five-chord passages followed accepted musical rules of harmonic arrangement. Others contained a harmonically unexpected chord in which two of four notes were out of key.

Harmonic sequences elicited a distinct magnetic response in participants' brains, the scientists report. Less-musical chords--especially those at the end of sequences, where they dramatically violated listeners' expectations--yielded a different pattern of magnetic activity.

Hearing unexpected chords was linked to magnetic activity in a left-brain region known as Broca's area and in adjacent right-brain tissue. Previous MEG studies found that these areas generate the same response, with one intriguing variation, when people hear ungrammatical words in sentences. In the face of such linguistic violations, Broca's area produces a stronger magnetic field than the right-brain area does, Maess and his coworkers say. In contrast, the right brain reacts more strongly to musical breaches.

"This is pretty solid work," remarks neuroscientist Robert J. Zatorre of McGill University in Montreal, who studies music perception. "Broca's area and related right-brain tissue might help to process other types of rule-based information."

For instance, these brain regions may foster understanding of cultural rules for social behavior, Zatorre says.

The proposed extension of Broca's area into music appreciation will spark controversy, he adds. Many linguists and cognitive scientists regard Broca's area as part of a brain network wired solely for language.