Summary: New research from the University of Alberta shows that the nucleus reuniens, a small thalamic region, coordinates synchronous slow-wave activity between the prefrontal cortex and the hippocampus during deep sleep. These findings indicate the nucleus reuniens may be essential for sleep-dependent memory consolidation.
Source: University of Alberta
Neuroscientists at the University of Alberta have uncovered a mechanism that helps form lasting memories during deep, slow-wave sleep.
This study focused on the nucleus reuniens, a thalamic structure that connects two brain areas central to memory processing—the prefrontal cortex and the hippocampus. The research indicates the reuniens coordinates their activity during slow-wave sleep, promoting synchronous slow-wave oscillations that are associated with consolidating recent experiences into long-term memory.
“Slow-waves during sleep support our ability to retain personal experiences, likely through coordinated activity in the prefrontal cortex and hippocampus,” explained Brandon Hauer, PhD candidate in the Faculty of Science and lead author of the study. “We found that the nucleus reuniens is responsible for coordinating synchronous slow-waves between these two structures. This suggests the reuniens plays an essential role in sleep-dependent memory consolidation.”
Slow-wave sleep is the deepest stage of non-REM sleep, characterized by slow oscillations—about one cycle per second—across wide regions of the brain. This stage of sleep is important for both physical recovery and cognitive processes; past work has linked slow-wave activity to the strengthening and reorganization of memory traces. The new study adds evidence that coordinated oscillations between the prefrontal cortex and hippocampus are facilitated by the nucleus reuniens, making it a key node for memory-related communication during sleep.
“Prior to this work, the pathway responsible for linking the prefrontal cortex and hippocampus during slow-wave sleep was unclear,” added Hauer, who conducted the research under the supervision of Clayton T. Dickson, professor in the Department of Psychology, and Silvia Pagliardini, associate professor in the Department of Physiology. “This relatively understudied region likely has a substantial role in forming long-term memories while you sleep. So if you studied for an exam and then slept, the nucleus reuniens may have helped to stabilize that information into a more permanent memory.”
Source:
University of Alberta
Media Contacts:
Katie Willis – University of Alberta
Image Source:
The image is in the public domain.
Original Research: Open access
“The Reuniens Nucleus of the Thalamus Has an Essential Role in Coordinating Slow-Wave Activity between Neocortex and Hippocampus”. Brandon E. Hauer, Silvia Pagliardini and Clayton T. Dickson. eNeuro. DOI: 10.1523/ENEURO.0365-19.2019.
Abstract
The Reuniens Nucleus of the Thalamus Has an Essential Role in Coordinating Slow-Wave Activity between Neocortex and Hippocampus
Researchers and educators have long considered how to optimize training and learning for humans, animals, and machines. In this work, we examine how a single variable—the difficulty of training—affects the rate of learning. Across many situations, we identify a “sweet spot” where training is neither too easy nor too difficult, and where learning proceeds most rapidly. We derive general conditions for this optimal zone for a broad class of learning algorithms, framed in terms of binary classification tasks. For all stochastic gradient descent–based learning algorithms considered, we find an optimal error rate during training of approximately 15.87%, corresponding to an optimal training accuracy near 85%. We demonstrate the effectiveness of this “Eighty-Five Percent Rule” both for artificial neural networks used in machine learning and for biologically plausible neural networks hypothesized to describe animal learning.