The relationship between sleep and brain plasticity, in particular why some EEG rhythms are involved in memory consolidation, is poorly understood. While it is known that dendritic calcium activity is involved in brain plasticity, it has hitherto not been investigated during sleep.
Now, a team of researchers has used simultaneous EEG and calcium recording to clarify this relationship. The results could lead to new avenues for treating learning and memory disorders, such as dementia.
The study recorded activity in rodent neocortical dendrites, the brain region responsible for holding new information. It demonstrated that dendrite activity is increased and synchronized during sleep. The activity is linked to short and repetitive brain waves called spindles, which are key to memory formation. The same relationship was not seen in the neuron cell bodies or throughout the cortical column.
“It is becoming increasingly clear that sleep plays an important role in these adaptive changes,” commented Julie Seibt (University of Surrey, Guildford, UK). “Sleep spindles have been associated with memory formation in humans for quite some time but nobody knew what they were actually doing in the brain. Now we know that during spindles, specific pathways are activated in dendrites, maybe allowing our memories to be reinforced during sleep.”
She continued: “In the near future, techniques that allow brain stimulation, such as transcranial magnetic stimulation (TMS), could be used to stimulate dendrites with the same frequency range as spindles. This could lead to enhance cognitive functions in patients with learning and memory disorders, such as dementia.”
Sources: Seibt J, Richard CJ, Sigl-Glöckner J et al. Cortical dendritic activity correlates with spindle-rich oscillations during sleep in rodents. Nat. Comm. 8, 684 (2017); www.surrey.ac.uk/mediacentre/press/2017/how-sleep-helps-brain-reorganise-itself