The title of the paper is "Distributed Fading Memory for Stimulus Properties in the Primary Visual Cortex" and it is the collaboration of the Max Planck Institute for Brain Research, the Frankfurt Institute for Advanced Studies, and the Institute for Theoretical Computer Science, Graz University of Technology in Austria. These teams were able to collect data using multielectrode recordings from the primary visual cortex of cats. Then using a 3 visual stimulus's (letters of the alphabet), they recorded brain activity of stimulus-related information in the spiking activity of large ensembles of around 100 neurons.

From the authors summary: "Researchers usually assume that neuronal responses carry primarily information about the stimulus that evoked these responses. We show here that, when multiple images are shown in a fast sequence, the response to an image contains as much information about the preceding image as about the current one. Importantly, this memory capacity extends only to the most recent stimulus in the sequence. The effect can be explained only partly by adaptation of neuronal responses."

As Danko Nikolić from the Max Planck Institute for Brain Research and his Austrian colleagues Wolfgang Maass and Stefan Häusler have shown, the activity in early brain areas depends on stimuli that arose some time ago. "The brain functions like a jug of water into which stones are thrown and, as a result, generate waves," explains Nikolić. "The waves overlap but the information as to how many stones were thrown into the jug and when they were thrown in is retained in the resulting complex activity patterns of the fluid."

The brain is clearly able to render this information usable and, for example, to superimpose images seen in succession. The duration and intensity of the continuing effect of images that have just been seen corresponds to a very detailed visual memory also known as iconic memory. If you see an image and close your eyes immediately afterwards it remains visible for a short while. It may be located in the primary visual cortex.

Press Release: Max Planck Institute for Brain Research - "Researchers crack part of the neuronal code"

Article from PLoS Biology: Distributed Fading Memory for Stimulus Properties in the Primary Visual Cortex

Danko Nikolić1,2#*, Stefan Häusler3#, Wolf Singer1,2, Wolfgang Maass2,3

1 Department of Neurophysiology, Max-Planck-Institute for Brain Research, Frankfurt, Germany, 2 Frankfurt Institute for Advanced Studies (FIAS), Johann Wolfgang Goethe University, Frankfurt, Germany, 3 Institute for Theoretical Computer Science, Graz University of Technology, Graz, Austria