An item in ScienceDaily (here) reports on a paper by Salazar, Gray and others, Content-Specific Fronto-Parietal Synchronization During Visual Working Memory in Science Express.
They looked at the visual short-term memory in the monkey brain by recording from neuron activity. The monkeys had to remember an object or location during a delay period and determine if it matched a later signal. They were rewarded if correct. For each object, the pattern of synchronous activity between the neurons was noted.
Brain waves of many neurons in the two hubs, called the prefrontal cortex and posterior parietal cortex, synchronized to varying degrees — depending on an object’s identity. This and other evidence indicated that neurons in these hubs are selective for particular features in the visual field and that synchronization in the circuit carries content-specific information that might contribute to visual working memory.
The researchers also determined that the parietal cortex was more influential than the prefrontal cortex in driving this process. Previously, many researchers had thought that the firing rate of single neurons in the prefrontal cortex, the brain’s executive, is the major player in working memory.
The location and identity of the objects was represented by the pattern of synchronous waves between the parietal and prefrontal cortex.
Here is the abstract:
Lateral prefrontal and posterior parietal cortical areas exhibit task-dependent activation during working memory tasks in humans and monkeys. Neurons in these regions become synchronized during attention-demanding tasks, but the contribution of these interactions to working memory is largely unknown. Using simultaneous recordings of neural activity from multiple areas in both regions, we find widespread, task-dependent, and content-specific synchronization of activity across the fronto-parietal network during visual working memory. The patterns of synchronization are prevalent among stimulus-selective neurons and are governed by influences arising in parietal cortex. These results indicate that short-term memories are represented by large-scale patterns of synchronized activity across the fronto-parietal network.