What's that you heard?

SMALL PRINT:BY ANALYSING patterns of electrical activity in the brain, researchers in the US have been able to reconstruct and identify words that a person hears.

The study, carried out on 15 patients who were to undergo procedures for epilepsy or brain tumour, used implanted electrodes to detect neural activity in a region of the brain involved in hearing.

The experiment played words and sentences from different English speakers to the participants, and recorded the corresponding brain activity patterns.

"Using these recordings, we asked what aspects of speech sounds could be reconstructed, or decoded, from higher order brain areas in the human auditory system," write the authors this week in PLoS Biology.

As part of the study, patients heard isolated words and pseudo-words, then the researchers used computer programmes to reconstruct the sounds from the brain activity patterns.

Based on the recorded brain patterns, the scientists were able to reproduce many of the “heard” sounds well enough to be able to recognise the words. “Word identification using averaged trials was substantially higher than chance,” they note.

An article on the University of California, Berkeley’s website says the ultimate goal is to explore how the human brain encodes speech.

“This research is a major step toward understanding what features of speech are represented in the human brain,” says researcher Robert Knight.

“[The] analysis can reproduce the sound the patient heard, and you can actually recognise the word, although not at a perfect level.”