London, April 2 : Scientists from the Hebrew University of Jerusalem and elsewhere have discerned how the reactions of single neurons give humans the capability of detecting fine differences in frequencies better than animals.
The researchers achieved this breakthrough by exposing the subjects to sound stimuli, and simultaneously utilising a technique to record the activity of single neurons in the auditory cortex-the brain region that is fundamental to the perception of sounds by the brain.
The study revealed that neurons in the human auditory cortex responded to specific frequencies with unexpected precision.
The researchers say that frequency differences as small as a quarter of a tone-in western music, the smallest interval is half a tone-could be reliably detected from individual responses of single neurons.
According to them, such resolution exceeds that typically found in the auditory cortex of other mammalian species like bats, serving as a possible correlate of the finding that the human auditory system can discriminate between frequencies better than animals.
The study, appearing in the journal Nature, suggests that the neural representation of frequency in the human brain has unique features.
The researchers said that as they exposed the patients in the study to "real-world" sounds like dialogues, music and background noise, the neurons exhibited complex activity patterns which could not be explained based solely on the frequency selectivity of the same neurons.
They say that this phenomenon has been shown in animal studies, but never before in humans.
Based on their observations, the researchers concluded that in contrast to the artificial sounds, behaviourally relevant sounds like speech and music engage additional, context-dependant processing mechanisms in the human auditory cortex.