Information from sensory organs, such as the eyes or the ears, is passed from nerve cell to nerve cell in the form of electrical impulses. These impulses can have very different repetition rates, occurring between one and one thousand times per second. At the end of their path, they eventually reach the granule cells in the cerebellum, where particular information is stored. Until now, scientists had assumed that granule cells are a uniform population of neurons that handle these different signals in the same way.
Dr Isabelle Straub from the Carl Ludwig Institute for Physiology investigated the electrical properties of cerebellar granule cells in mice. She discovered that the cells have different properties, enabling them to store more information. Granule cells can detect and transmit electrical impulses with specific frequencies. “Granule cells function rather like a sieve. They filter out specific information according to frequency,” said Straub. The ability to decompose signals based on their repetition rate is similar to the Fourier transform – the transformation used in the digital compression of music files into MP3s. The MP3 method makes it possible to store music as a greatly reduced amount of data. And indeed, computer simulations by Straub and her colleagues show that neural circuits with different granule cells have an increased storage capacity.
These latest research findings will help scientists to better understand how our brain processes and stores temporal information. In a further step, the scientists can now investigate whether the possibility of separating incoming electrical impulses according to frequency, and thus increasing the storage capacity, can also be applied by other regions of the brain. The Carl Ludwig Institute for Physiology at Leipzig University’s Faculty of Medicine is researching the basic functions of the nervous system. In particular, its scientists are investigating how nerve cells communicate with each other, the changes that occur during learning, and brain energy metabolism.
Original title of the publication at eLifesciences.org:
Gradients in the mammalian cerebellar cortex enable Fourier-like transformation and improve storing capacity