Why does sleeping on it help? This is the question tackled by new research at the University of Bristol, which reveals how brain activity during sleep sorts through the huge number of experiences we encounter every day, filing only the important information in memory.
The new discoveries, made by researchers from Bristol’s Centre for Synaptic Plasticity, provide further evidence for the benefits of a good night’s sleep. This is important because the bad nights of sleep often experienced by both the healthy population, and people with schizophrenia or Alzheimer’s disease, lead to impaired mental function.
The findings, published today in the journal Cell Reports,and put into context in an article in Trends in Neuroscience, show that patterns of brain activity that occur during the day are replayed at fast-forward speed during sleep.
This replayed activity happens in part of the brain called the hippocampus, which is our central filing system for memories. The key new finding is that sleep replay strengthens the microscopic connections between nerve cells that are active – a process deemed critical for consolidating memories. Therefore, by selecting which daytime activity patterns are replayed, sleep can sort and retain important information.
Lead researcher Dr Jack Mellor, from the School of Physiology, Pharmacology and Neuroscience, said: ‘These findings are about the fundamental processes that occur in the brain during the consolidation of memory during sleep. It also seems that the successful replay of brain activity during sleep is dependent on the emotional state of the person when they are learning. This has major implications for how we teach and enable people to learn effectively.’
Funding: The research team involved the University of Bristol’s Centre for Synaptic Plasticity within the School of Physiology, Pharmacology & Neuroscience and was supported by the MRC, Wellcome Trust, EPSRC and Eli Lilly & Co.
The other papers mentioned in this research are:
Memory trace replay: the shaping of memory consolidation by neuromodulation by Atherton, LA, Dupret, D & Mellor, JR (2015) in Trends in Neuroscience. 38, 560-70.
Decoupling of sleep-dependent cortical and hippocampal interactions in a neurodevelopmental model of schizophrenia. By Phillips, KG, Bartsch, U, McCarthy, AP, Edgar, DM, Tricklebank, MD, Wafford, KA, Jones, MW (2012) in Neuron, 76, 526-33.
Source: University of Bristol
Image Credit: The image is adapted from the University of Bristol press release.
Original Research: Full open access research for “Sharp-Wave Ripples Orchestrate the Induction of Synaptic Plasticity during Reactivation of Place Cell Firing Patterns in the Hippocampus” by Sadowski, JHLP, Jones, MW and Mellor, JR in Cell Reports. Published online January 19 2016 doi:10.1016/j.celrep.2016.01.061
Abstract
Sharp-Wave Ripples Orchestrate the Induction of Synaptic Plasticity during Reactivation of Place Cell Firing Patterns in the Hippocampus
•Reactivated place cell firing patterns can induce LTP in the hippocampus
•Sharp-wave ripples are required for the induction of LTP
•Dendritic depolarization during sharp-wave ripples is required for LTP
•The timing of place cell firing within sharp-wave ripples controls LTP induction
Summary
Place cell firing patterns reactivated during hippocampal sharp-wave ripples (SWRs) in rest or sleep are thought to induce synaptic plasticity and thereby promote the consolidation of recently encoded information. However, the capacity of reactivated spike trains to induce plasticity has not been directly tested. Here, we show that reactivated place cell firing patterns simultaneously recorded from CA3 and CA1 of rat dorsal hippocampus are able to induce long-term potentiation (LTP) at synapses between CA3 and CA1 cells but only if accompanied by SWR-associated synaptic activity and resulting dendritic depolarization. In addition, we show that the precise timing of coincident CA3 and CA1 place cell spikes in relation to SWR onset is critical for the induction of LTP and predictive of plasticity generated by reactivation. Our findings confirm an important role for SWRs in triggering and tuning plasticity processes that underlie memory consolidation in the hippocampus during rest or sleep.
“Sharp-Wave Ripples Orchestrate the Induction of Synaptic Plasticity during Reactivation of Place Cell Firing Patterns in the Hippocampus” by Sadowski, JHLP, Jones, MW and Mellor, JR in Cell Reports. Published online January 19 2016 doi:10.1016/j.celrep.2016.01.061
