Comparing memory encoding across species
Animal models are widely used to study memory, in the hope that the knowledge will inform our understanding of the human brain. But due to differences in experimental design, extrapolating findings from animal models to humans is difficult. As an example, studies of how the hippocampus represents navigation-based memory in rodents often use freely moving animals, whereas studies in humans and non-human primates normally use immobile subjects navigating in virtual reality. Does a lack of movement affect how the hippocampus represents a memory?
In this study, researchers tested this question, finding that real-world navigation engages more neurons in a particular region of the hippocampus. The study also looked at the size of the memory-encoding ensemble, which hints at the memory storage capacity of the hippocampus. The authors found that in non-human primates, memories are encoded more efficiently than in rodents (i.e. a smaller proportion of cells is engaged), although the same number of neurons is used. The authors suggest that memories may be stored in groups of neurons with an optimal size, even across species.
Thome et al. (2017) Evidence for an evolutionarily conserved memory coding scheme in the mammalian hippocampus. J Neurosci 37(10):2795-2801
How to make your brain like that of a memory champion
Memory athletes can perform remarkable feats, like memorizing the order of a deck of play cards in just 17 seconds, or a sequence of 520 digits in five minutes. Is there something characteristic about their brains that gives them these extreme capabilities? To find out, a group of researchers from Germany, the Netherlands and the US scanned the brains of 23 memory experts. In addition, they also scanned the brains of everyday folk before and after they were trained in a commonly used mnemonic aide known as the method of loci.
Six weeks of mnemonic training in naïve subjects improved recall. In addition, training changed the way their brains were activated during memory encoding, making it more like that of superior memory athletes. In fact, after training, the patterns of brain activity during rest also became more similar to that of memory champions. The changes in brain activation and memory recall lasted over 4 months, showing that mnemonic training can enduringly alter brain networks and improve memory performance.
Dresler et al. (2017) Mnemonic training reshapes brain networks to support superior memory. Neuron 93(5):1227-1235
Synchronizing brain waves improves working memory
Working memory allows us to concentrate on one task while we hold other information in mind, enabling complex thought processes and contributing significantly to intelligence. Two recent papers show that working memory can be improved by stimulating the brain in a way that synchronizes brain waves.
In the first, by researchers at University College London, electrical stimulation was simultaneously applied at two locations in frontal and parietal cortex. When this stimulation was synchronized at theta frequency (~6 Hz), participants responded more rapidly, and with no decrease in accuracy, in a difficult verbal working memory task.
In the second study, researchers at McGill University used transcranial magnetic stimulation (TMS) to increase the strength of theta frequency waves, while subjects performed an auditory working memory task. They found that rhythmic TMS, delivered at theta frequency to a brain region needed for the task, improved working memory performance, but that arrhythmic stimulation did not.
Together, the two reports show that rhythmic coordination of brain waves at theta frequency is important for working memory. Furthermore, by enhancing theta activity, working memory performance can be temporarily improved.
Violante et al. (2017) Externally induced frontoparietal synchronization modulates network dynamics and enhances working memory performance. eLife 6:e22001
Albouy et al. (2017) Selective entrainment of theta oscillations in the dorsal stream causally enhances auditory working memory performance. Neuron doi:http:/dx.doi.org/10.1016/j.neuron.2017.03.015
when a child is ready for school
Both academic and behavioral considerations determine whether a child is ready to begin her schooling. For this, measuring certain traits and abilities can be useful. In this study, researchers sought to find out how well a child’s executive functioning could predict their academic and social readiness for school.
Executive functions allow goal-directed thought and planning, and two sub-categories exist: hot and cool. Hot executive functions refer to self-management when emotions are involved. Cool executive functions, in contrast, do not involve emotions and are generally used for abstract, symbolic tasks.
The researchers wanted to know whether cool and hot executive functions could predict academic and social readiness for school, respectively. They did: Cool executive functions like working memory and attention were good predictors of academic readiness, while hot executive functions like delayed gratification (waiting for a larger reward rather than immediately taking a smaller reward) predicted a child’s social and emotional readiness for school. The authors concluded that sound development of executive functions is important for a child’s readiness to begin school.
Mann et al. (2017) Pathways to school readiness: executive functioning predicts academic and social-emotional aspects of school readiness.
Mind, Brain and Education 11(1):21-31