New Publication - Laurenz Muessig and Wills Lab by Joshua Bassett

The Wills and Cacucci labs are excited to announce the publication of their latest paper, out now in Current Biology. 

The hippocampus is a brain region that is important for the formation and consolidation of episodic memories (memories of events, as well as where and when they happened). In rodents the hippocampus contains neurons that encode an animal’s current position in space (place cells). Different place cells are active in different discrete locations of an environment forming a neural map of space, necessary for animals to create spatial memories (for example learning the location of a reward in a maze). The consolidation of experiences is known to involve the ‘reactivation’ of place cell waking activity during sleep. We were interested when ‘reactivation’ emerges in early development. Episodic memory is mostly absent in young altricial mammals (including humans): we hypothesised that this may be due to a lack of reactivation in developing place cells. 

We recorded the activity of large ensembles of place cells from the hippocampus in young rats (2-5 weeks old) while these explored an environment and also recorded the same neuronal ensembles in subsequent sleep. Surprisingly, we found that reactivation of place cells’ waking activity is present even in the youngest animals. However, reactivated networks represented only single locations in the environment the rat had just visited. When adults sleep, instead, place cells ‘replay’ sequences of place cell firing corresponding to extended trajectories through the environment the animal had previously explored. This ‘replay’ of place cell sequences, which allows the hippocampus to stitch together different locations into ordered sequences, emerges gradually during the following few weeks, a time span that correlates well with the period when spatial memory emerges in rats. 

Our results might therefore suggest a reason why young children do not form episodic memories of experiences: the developing hippocampus cannot yet link different elements of an event to a cohesive memory, but only stores individual fragments of it. 

You can find the full paper here

New Publication - Guifen Chen et al by Joshua Bassett

Guifen Chen et al celebrate their latest publication entitled ‘Differential influences of environment and self-motion on place and grid cell firing’ in Nature Communications (7th February 2019).

A team of researchers at UCL, funded by Wellcome Trust and the European Union, have shown that our brains understand where we are by combining two independent information streams.

The authors looked at the activity of two types of spatial cells, place cells and grid cells, using a new immersive virtual reality system developed specifically for rodents. By dissociating the visual movement of the world from physical self-motion of the animal they found that place cells predominantly rely on visual information in order to provide a location signal, while grid cells were more strongly influenced by physical motion.

The lead author, Dr Guifen Chen explains:

“Ever since place cells and grid cells were discovered, scientists have wanted to believe these cells form a unified representation of space. However, our study shows for the first time that place and grid cells, when recorded simultaneously, reflect visual and self-motion inputs independently, and need not be tightly coupled”,

Guifen also worked with Yi Lu, a PhD student here in the Cacucci lab, Dr John King, Prof Francesca Cacucci and Prof Neil Burgess on this paper.

With this result, we can begin to understand how people combine different types of information when navigating through the world. The results may have broader implications for how we process conceptual knowledge. If place cells represent specific states or concepts and grid cells represent the transitions between them, then together the system could support learning and planning within all kinds of tasks.

you can read the full paper here:

We Are Live! by Joshua Bassett

Here in the Cacucci lab, we are excited to be launching our website. Here you can find out more information about our research, the amazing scientists who work here, links to our publications, opportunities to join us and some Cacucci lab related news! Peruse at your leisure!