Brain stimulation perks up memory
By recording brain activity in patients undergoing epilepsy surgery, Michael Kahana and colleagues from The University of Pennsylvania have found that brain stimulation can improve or hamper memory encoding, depending on the precise time that stimulation occurs.
Patients were asked to remember lists of words while their brain activity was recorded. On some days, a patient would perform well, but on others their memory would be poorer. Importantly, the researchers showed that how well a memory was encoded was predictable based on brain activity patterns. Next, the researchers checked how brain stimulation affected memory, finding that its effects depended on what state the brain was in. If the brain activity pattern predicted poor memory encoding, stimulation improved performance. Conversely, if the brain was in a state conducive to good memory formation, stimulation was detrimental.
The study is important for two reasons. First, it shows that we can predict memory performance based on brain activity. Second, it provides an explanation for conflicting results on whether brain stimulation improves or impairs memory – the key is in the timing.
How self-belief helps learning
Self-belief is important in learning. Children who believe they can learn and improve – those with a so-called “growth mindset” – perform better than children who think their abilities are fixed. In this study, researchers investigated whether children with fixed or growth mindsets differed in the way they responded to mistakes, and whether that was linked with learning performance.
First, children were separated into two groups – growth mindset or fixed mindset – based on their answers to a questionnaire. Next, the children undertook a go/no-go task. As they performed the task, an EEG measured the children’s brain activity to monitor their attention. The researchers found that compared to children with a fixed mindset, those with a growth mindset paid more attention to their mistakes; they also performed better in subsequent trials. This suggests that having self-belief in your ability to learn helps you pay attention to the mistakes you make, and therefore to learn more efficiently.
The authors suggest that teachers should instill students with self-belief in order to maximise their learning, and urge them to pay attention to the mistakes they make.
Schroder et al. (2017) Neural evidence for enhanced
attention to mistakes among school-aged children with a growth mindset.
Developmental Cognitive Neuroscience 24:42-50
A new model of memory formation
A commonly accepted view of memory storage is that short- and long-term memories are stored in the hippocampus and neocortex, respectively. In this model, short-term memory achieves long-term storage when it is transferred from hippocampus to neocortex during a sleep-dependent process called consolidation.
A new study by Susumu Tonegawa and colleagues at MIT suggests this model of memory formation needs revision. The researchers used a technique that allows them to identify which brain cells hold a memory, the so-called “engram” cells. With this approach, they showed that cells in the neocortex already hold memories just one day after learning, but that they aren’t actually necessary for memory recall – the neocortex remains silent when an animal recalls a memory in the days immediately following learning. However, artificially activating the engram cells in neocortex at this early stage can trigger memory recall. Some two weeks after learning, the neocortex has become necessary for recall, just as in the traditional model.
Thus memories seem to be created simultaneously in hippocampus and neocortex, although they remain in a silent state within cortex until consolidation is complete.
Kitamura et al. (2017) Engrams and circuits crucial for
systems consolidation of a memory. Science 356(6333):73-78
Rejuvenating memory capabilities in old age
As we age, our cognition slows and our memory worsens. Previous work had shown that cognitive function in aged mice improved when they were given infusions of blood plasma from young mice – something in the young blood evidently helped memory and cognition, although its identity remained unknown. On the surface, this finding has potential for treating Alzheimer’s disease. However, because the study was done in mice, many open questions remain.
In the current study, researchers assessed whether human blood might also have restorative properties. To check, they took umbilical cord plasma from humans and gave it to aged mice. This improved mouse spatial memory performance and enhanced hippocampal plasticity. What’s more, the researchers isolated a single protein – found at high levels in human umbilical cord blood – that could produce similar benefits. The study moves us a step closer to lessening the memory deficits that accompany human ageing.
Castellano et al. (2017) Human umbilical cord plasma
proteins revitalize hippocampal function in aged mice. Nature 544:488-492