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Neuroscientists identify brain circuit necessary for memory formation: New findings challenge standard model of memory consolidation -- ScienceDaily

The researchers labeled memory cells in three parts of the brain: the hippocampus, the prefrontal cortex, and the basolateral amygdala, which stores memories' emotional associations. Just one day after the fear-conditioning event, the researchers found that memories of the event were being stored in engram cells in both the hippocampus and the prefrontal cortex. However, the engram cells in the prefrontal cortex were "silent" -- they could stimulate freezing behavior when artificially activated by light, but they did not fire during natural memory recall. "Already the prefrontal cortex contained the specific memory information," Kitamura says. "This is contrary to the standard theory of memory consolidation, which says that you gradually transfer the memories. The memory is already there." Over the next two weeks, the silent memory cells in the prefrontal cortex gradually matured, as reflected by changes in their anatomy and physiological activity, until the cells became necessary for the animals to naturally recall the event. By the end of the same period, the hippocampal engram cells became silent and were no longer needed for natural recall. However, traces of the memory remained: Reactivating those cells with light still prompted the animals to freeze. In the basolateral amygdala, once memories were formed, the engram cells remained unchanged throughout the course of the experiment. Those cells, which are necessary to evoke the emotions linked with particular memories, communicate with engram cells in both the hippocampus and the prefrontal cortex.

Hippocampal and prefrontal processing of network topology to simulate the future : Nature Communications

Here we tested the hypotheses that the hippocampus retrieves representations of the topological structure of the environment when new paths are entered in order to support goal-directed navigation and the lateral PFC performs path-planning via a BFS mechanism. We combined a graph-theoretic analysis of the city streets of London with functional magnetic resonance imaging (fMRI) data collected from participants navigating a film simulation of London’s streets. Our analysis reveals that the right posterior hippocampus specifically tracks the changes in the local connections in the street network, the right anterior hippocampus tracks changes in the global properties of the streets and the bilateral lateral prefrontal activity scales with the demands of a BFS. These responses were only present when long-term memory of the environment was required to guide navigation.

Satnavs 'switch off' parts of the brain: Using a satnav to get to your destination 'switches off' parts of the brain that would otherwise be used to simulate different routes -- ScienceDaily

When volunteers navigated manually, their hippocampus and prefrontal cortex had spikes of activity when volunteers entered new streets. This brain activity was greater when the number of options to choose from increased, but no additional activity was detected when people followed satnav instructions. "Entering a junction such as Seven Dials in London, where seven streets meet, would enhance activity in the hippocampus, whereas a dead-end would drive down its activity. If you are having a hard time navigating the mass of streets in a city, you are likely putting high demands on your hippocampus and prefrontal cortex," explains senior author Dr Hugo Spiers (UCL Experimental Psychology). "Our results fit with models in which the hippocampus simulates journeys on future possible paths while the prefrontal cortex helps us to plan which ones will get us to our destination. When we have technology telling us which way to go, however, these parts of the brain simply don't respond to the street network. In that sense our brain has switched off its interest in the streets around us."

New avenue for anti-depressant therapy discovered -- ScienceDaily

The researchers found that a protein called JNK when active, represses the generation of new neurons in the hippocampus, a part of the brain that controls emotions and learning. By inhibiting JNK solely in newly generated nerve cells in the hippocampus, the researchers were able to alleviate anxiety and depressive behaviour in mice. This previously unknown mechanism brings fresh insight on how the brain works to regulate mood and indicates that inhibitors of JNK, such as the one used here, can provide a new avenue for anti-depressant and anxiolytic drug development.

Stress and hippocampus

Research in the neurological literature for years has shown changes in the hippocampus when one has experienced long stress – so a release of hormones such as cortisol actually causes damage to the hippocampus. But as it turns out, it may be that damage to the hippocampus also regulates one’s stress response – and that could contribute to the onset of depression. Again, it’s another one of these vicious cycles. We have a list of 100 potentially stressful events – divorce, moving house, losing loved ones, etc. We found that our group of depressed individuals had not experienced more stressful events in their lives – but they had experienced them as more stressful.

Imagination specificity helps pull people forward

[Research] has shown that people who can imagine future events in detail are more likely to go out and seek social support when they need it, they experience less worry about the upcoming event and they’re more likely to put good, successful behaviours into practice when they experience those events they’ve been thinking about.

breath in through your nose

"One of the major findings in this study is that there is a dramatic difference in brain activity in the amygdala and hippocampus during inhalation compared with exhalation," said lead author Christina Zelano, assistant professor of neurology at Northwestern University Feinberg School of Medicine. "When you breathe in, we discovered you are stimulating neurons in the olfactory cortex, amygdala and hippocampus, all across the limbic system."

Stress and hippocampus

New research now shows that even a brief period of stress can cause the hippocampus to start shrinking.This shrinking of the hippocampus -- a change in the brain's structure -- actually precedes the onset of a change in behaviour, namely, the loss of memory.

Mapping social space in the hippocampus

Participants played the lead role in a “choose-your-own-adventure” game, in which they interacted with cartoon characters. We found that a geometric model of social relationships, in a “social space” framed by power and affiliation, predicted hippocampal activity. Moreover, participants who reported better social skills showed stronger covariance between hippocampal activity and “movement” through “social space.” These results suggest that the hippocampus is critical for social cognition, and imply that beyond framing physical locations, the hippocampus computes a more abstract, multidimensional cognitive map. Importantly, these neural representations of social space may be relevant for psychological wellbeing. Here we report new evidence on how this model can be predictive of social behavior and cognition. We found that a number of geometric variables, extracted from participants’ behavior in the game, correlated robustly with trait scores: participants with higher social anxiety tended to give less power to the game’s characters; and participants who reported less social avoidance and higher self-efficacy showed increased exploration of the social space. Additionally, we found that lower hippocampal volumes predicted lower fidelity tracking of social distance in the posterior cingulate cortex.