Learning New Words: Give the Hippocampus a Rest
By: Mia Daucourt
Of the many brain regions involved in learning, the small, seahorse-shaped hippocampus, is one of the most critical. In fact, when Alzheimer’s patients cannot remember where they put their keys or whether or not they brushed their teeth, it’s because damage to the hippocampus is disrupting their short-term memory recall. The hippocampus is especially vital for school achievement. Think about it—without being able to hold onto the new information you just learned in school, how would you succeed?
Interestingly, beyond its seahorse-like shape, the hippocampus also has functional similarities to the seahorse. Just as the male seahorse fertilizes and stores newly-implanted eggs in his ventral pouch, the hippocampus also temporarily stores newly-acquired memories. Once the hippocampus brings in this new information, it then transfers memories form short-term to long-term storage, a process known as consolidation. Importantly, in the same vein as the fertilized eggs, which must undergo a gestational period before they can move on, the hippocampus must also undergo a period of rest, where new information is no longer being brought in, for new memories to be properly consolidated.
Recent work by Landi and colleagues (2018) used a community sample of adolescents and young adults to examine how age, vocabulary and reading skills, and hippocampal memory consolidation influenced an individual’s ability to learn new words. As an added layer, the authors also used fMRI scans to investigate whether brain activation was different for participants who were asked to remember new words immediately after learning them, than for participants who learned the new words one day, got to go home and sleep, and were asked to remember the next day. The researchers wondered if the rest period was important for their hippocampus to transfer the new words form short-term to long-term memory. Overall, they found that a rest period (to allow for hippocampal memory consolidation) was important for word learning. In fact, on the neural level, their scans showed significantly greater activation in the hippocampus and language-associated brain regions for the group given a day off before recall than the group that had to recall words immediately.
Different patterns of neural activation were also found for age, and vocabulary and reading skills when learning new words. Specifically, the fMRI scans showed greater neural activation for older participants, and those with better reading and vocabulary scores. Overall, this meant that older participants with better reading-related skills, learned new words more quickly and underwent greater memory consolidation. An important caveat to this finding was that, although the authors found that superior vocabulary and reading skills contributed to improved word learning ability overall, reading and vocabulary skills are especially important for younger participants. The authors concluded that this increased reliance on reading-related skills for younger people’s word learning was most likely related to their poorer sleep habits.
Overall, these findings support the vital role of the hippocampus for word learning. Furthermore, they highlight the importance of giving the hippocampus rest and “offline” time to consolidate new material. Neural scans also showed that age and reading-related skills influence the hippocampus’ ability to consolidate new memories. All in all, these findings beg college students to consider the implications of their last-minute, all-nighter cram sessions. Are they really better off staying up and cramming or would sleep be the best medicine?
Landi, N., Malins, J.G., Frost, S.J., Magnuson, J.S., Molfese, P., Ryherd, K., Fueckl, J.G., Mencl, W.E., & Pugh, K.R. (2018). Neural representations for newly learned words are modulated by overnight consolidation, reading skill, and age. Neuropsychologia
, 111, 133-144.