Life: Like oil and water?

“Rediscovery” of a decades-old physics idea reignites the fields of cellular and molecular biology

Review written by Xinyang (David) Bing (LSI)

Lava lamps are fluorescent mixtures of oil and water that are immiscible and, when heated, float around, generating hypnotizing patterns that lull you to sleep. Now, biologists are seriously considering the possibility that the same physics that govern lava lamps may also control almost everything that goes on inside our cells.1 Walk through the halls of MIT and Harvard, Oxford and Cambridge, or of course Princeton, and you would likely hear what everybody is talking about: liquid-liquid phase separation.

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What can amoebae teach us about “loners”?

Review written by Thiago T. Varella (PSY GS) and Gabriel T. Vercelli (PHY ‘20)

Ever since the spread of SARS-Cov-2 imposed quarantines of global reach, people around the world have voiced their frustrations about social isolation. Indeed, Aristotle said back in 4th century BC, “man is by nature a social animal,” highlighting that our unease towards isolation is at least as ancient as the Classical era. However, as seemingly unnatural as social isolation might be for humans, it plays a crucial role in the current attempts to stave off the pandemic. Interestingly, isolation might serve a similar purpose in the natural world! Individuals that do not engage in collective behaviors have been observed in many social species. This behavioral divergence is usually thought of as an error, a failure to perfectly coordinate all individuals in a population; but this isolation could, at least theoretically be premeditated or shaped by natural selection (Barta, 2016). This leads to the question: are these isolated individuals, also called “loners,” a mere consequence of failed synchronization of the group, or could they be a mechanism nature developed to mitigate the risks of collective action?

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Understanding visual navigation

Understanding visual navigation using cue cells

Review written by Sara Camilli (QCB) and Adelaide Minerva (PNI)

As we go about our daily lives, we often do not consciously think about all the real-world landmarks that we use to position ourselves in space. Yet, as we walk to our local coffee shop or go for a jog in the park, our brain is continuously updating its internal representation of our location, which is critical to our ability to navigate the world. However, we also know that humans and a number of animals can update this internal representation of their position in space even in the absence of external cues. This phenomenon, known as path integration, involves interaction between the parietal cortex, medial entorhinal cortex (MEC), and hippocampus regions of the brain. Prior work has shown that grid cells in the MEC have firing fields that are arrayed in a hexagonal lattice, tiling an environment. Further, there is evidence of inputs to the MEC that encode the velocity at which an animal is moving, which can be used to update the animal’s internal representation of its position. Together, these features support a role of the MEC in path integration. 

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