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Working Memory Relies On Synchronizing Neurons

New research from Finland suggests that working memory relies on synchronizing brain cells or neurons to link up different parts of the brain and help them communicate with each other and that this mechanism also determines working memory capacity.

You can read about the study by researchers at the Neuroscience Center of the University of Helsinki online in the 5 April ahead of print issue of the Proceedings of the National Academy of Sciences, PNAS.

In this study the researchers found that the synchronization of neuronal activity in different brain areas affects both the maintenance and the contents of working memory; and they were able to predict individuals’ working memory capacity by studying images of their brain activity.

The working memory, or as the researchers term it, the visual working memory (VWM), of the average human being can only hold about three or four objects at any one time before they are sent to “cognitive processing” whereupon we become aware of them, have thoughts about them, make decisions, and put things in long term memory.

Problems with VWM are linked to several neuropsychological disorders, including dementia, schizophrenia and autism.

We already know, wrote the authors, that the frontal, parietal, occipital, and temporal regions of the cerebral cortex (the “grey matter” on the surface of the brain) maintain VWM through a sustained neuron activity in a complex network that links them together.

However, we know very little about the workings and capacity of the underlying brain cell mechanisms that coordinate these distributed and networked processes so they can hold coherent mental images in VWM.

Led by Drs. Satu and Matia Palva, the researchers used magneto- and electroencephalography (MEG and EEG) to image the brain activity of people while they carried out working memory tasks.

They developed a new way of using MEG and EEG to identify networks of fast brain cell interactions (ie. synchrony) linking the different areas of the cerebral cortex.

They wrote that they:

“… mapped the anatomical and dynamic structures of network synchrony supporting VWM by using a neuro informatics approach and combined magnetoencephalography and electroencephalography.”

Altogether they mapped nearly four billion different neuronal interactions and using the new approach they were able to spot functional networks in the brain areas to an accuracy of milliseconds.

The researchers were particularly interested in rhythmic interactions among the different brain regions and they found that these were temporarily synchronized while they sustained the working memory of visual stimuli:

“Interareal phase synchrony was sustained and stable during the VWM retention period among frontoparietal and visual areas in α- (10-13 Hz), β- (18-24 Hz), and γ- (30-40 Hz) frequency bands,” they wrote.

They also found that synchrony of neuronal activity among different brain areas was linked both to the maintenance and to the contents of working memory.

For instance, as memory load increased, the synchrony among the “frontoparietal regions known to underlie executive and attentional functions during memory maintenance” got stronger, and memory capacity was predicted by synchrony in a network where the “intraparietal sulcus was the most central hub”.

They concluded that these findings could be revealing a “systems level mechanism for coordinating and regulating the maintenance of neuronal object representations in VWM”.

Working memory, like attention, plays a central role in cognition and consciousness, in how we become aware of and deal with the world around us, so the more we find out about their underlying neuronal mechanisms the better our chances of improving the diagnosis and treatment of brain conditions like autism, Alzheimer’s disease, dementia, schizophrenia, perception and learning disorders.



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