Jekyll2021-03-03T16:21:38-05:00https://jeremyforest.github.io//feed.xmlJeremy ForestJeremy ForestNew paper on adult-born neurons and memory in the olfacory bulb of mice2020-03-30T00:00:00-04:002020-03-30T00:00:00-04:00https://jeremyforest.github.io//posts/paper-changing-perceptual-learning<p>This is the second paper from my PhD work.</p>
<p>It’s entitled ‘Short-term availability of adult-born neurons for memory encoding’.
In this paper we were wondering how the olfactory bulb is able to balance the persistance versus transience of memories with the incoming stream of adult-born neurons that constantly integrate into the network. To test this we asked mice to perform two successive olfactory discrimination learning tasks with varying times between tasks.</p>
<p>First we showed that the presence of adult born neurons correlates with performance (using adult-born neurons labelling with Brdu). In other words performances are linjed to adult-born neurons fate.</p>
<p><img src="/assets/2020-03-30-paper-changing-perceptual-learning/figure1.jpg" alt="figure 1" /></p>
<p>Next we added a second discrimination learning task and showed that time between learning session affects stored memory in a critical way.</p>
<p><img src="/assets/2020-03-30-paper-changing-perceptual-learning/figure2.jpg" alt="figure 2" /></p>
<p>Importantly sensory reactivatiion prevents both cells and memory loss !</p>
<p><img src="/assets/2020-03-30-paper-changing-perceptual-learning/figure3.jpg" alt="figure 3" /></p>
<p>Finally using optogenetics we demonstrate that distinct adult-born neurons cohorts are recruited for distinct memories.</p>
<p><img src="/assets/2020-03-30-paper-changing-perceptual-learning/figure4.jpg" alt="figure 4" /></p>
<p>So to answer the question of this paper we can take from these experiments that it seems that:</p>
<ul>
<li>cohorts of neurons of different ages, but still within their critical period, are required to allow the encoding of successive learning experiences.</li>
<li>availability of adult-born neurons for encoding new experience lasts no longer than 20 days.</li>
<li>performance relies on adult-born neurons recruited in the initial task suggesting that the memory is recalled rather than re-encoded.</li>
<li>the state of synaptic integration of the adult-born neurons seems to make them more or less sensitive to competition from later waves of adult-born neurons.</li>
</ul>
<p>So to sum up (and copy pasta from the paper) : Much of what we experience is ultimately forgotten, but memories for some events persist. Here, we report that modulation of the OB circuitry, as a function of the environment and dependent on the fate of maturing adult-born neurons, is responsible for the balance between the transience or persistence of memory. This is made possible thanks to distinct neuronal populations encoding temporally distinct experiences.</p>Jeremy ForestTitle is 'Short-term availability of adult-born neurons for memory encoding'New paper on Complex perceptual learning2020-01-29T00:00:00-05:002020-01-29T00:00:00-05:00https://jeremyforest.github.io//posts/paper-complex-perceptual-learning<p>The first paper from my PhD work is now published ! This one took a few years to get all the data needed and quite a number of behavior and microscope hours !</p>
<p>It’s actually been out for a couple of month now, but I’m just taking the time to write this now. It’s entitled ‘Role of Adult-Born Versus Preexisting Neurons Born at P0 in Olfactory Perception in a Complex Olfactory Environment in Mice’. Here I’ll attempt to sum up the main take home message of this paper.</p>
<p>What we wanted to know was if and how olfactory bulb neuronal populations (the preexisting neurons and the new neurons born from adult neurogenesis) differ when the animal is learning. We used a non-reinforced passive discrimination learning task with several level of difficulty (environmental complexity) in which the animal was exposed to different number of similar odorants for several days. Then we tested the mice on their ability to discriminate these odorant pairs.</p>
<p><img src="/assets/2020-01-29-paper-complex-perceptual-learning/figure1.jpg" alt="figure 1" /></p>
<p>Animals were able to learn to discriminate all the odorants that we exposed them to.</p>
<p><img src="/assets/2020-01-29-paper-complex-perceptual-learning/figure2.jpg" alt="figure 2" /></p>
<p>Previous data tells us that with learning we see an increased in the survival of adult-born neurons, which we also observed here. However, learning to discriminate more odorants did not lead to a proportional increase in adult-born neurons survival. More complex learning however lead to an increased in the recruitment of the surviving neurons to the processing of the task (as indexed by immediate early gene labelling).</p>
<p><img src="/assets/2020-01-29-paper-complex-perceptual-learning/figure3 and 4.jpg" alt="figure 3-4" /></p>
<p>A detailed analysis of neuronal morphology in every group showed a differential involvement of adult-born versus preexisting neurons. On the one hand, adult-born neurons showed increased spine density in the basal, apical proximal and apical distal domains after learning and that independantly of environmental complexity. On the other hand, preexisting neurons showed a spine increase only after being exposed to the more complex learning environment and only in the apical distal domains.</p>
<p><img src="/assets/2020-01-29-paper-complex-perceptual-learning/figure5 and 6.jpg" alt="figure 5-6" /></p>
<p>This lead us to test the hypothesis that preexisting neurons could support learning in the complex perceptual learning task only while adult-born neurons in both simple and complex perceptual learning tasks. To test this we used optogenetic inhibition of each population in the simpler or more complex environment in freely behaving mice and showed that is it indeed the case.</p>
<p><img src="/assets/2020-01-29-paper-complex-perceptual-learning/figure7 8 and 9.jpg" alt="figure 7-8-9" /></p>Jeremy ForestComplex perceptual learningNew year2020-01-24T00:00:00-05:002020-01-24T00:00:00-05:00https://jeremyforest.github.io//posts/writing-more<p>It’s still January so I guess there is a few more days for some new year resolutions !</p>
<p>The main thing I see right now is that I want to take a bit more time and write the things I don’t take the time to write.
Well that’s a convoluted sentence. Anyway …
You might want to know why right ? Well it’s not for you primarily (sorry :p) but for me. Why is that ? Simple enough, I figured out that wirting things down was helping me a lot structuring the ideas I get every day, into a coherent ensemble (well sometimes! some ideas are just too crazy or studid but hey we all have those right?). Discarding the ones that are bad will clear up some thought for new ones and writing down the good ones will allow me to formulate a plan to get them done.</p>
<p>There always seems to be something more urgent than writing, or so that’s what it has always been for me. But besides being a (probably) good experience and a good outlet for structuring thought processes, I’m hoping that it will also make me gain time by having having a more coherent and structured thought process.
At least I’m hoping !</p>
<p>See you in the next post ! ;)</p>Jeremy ForestNew year resolutionsPostdoc2019-06-02T00:00:00-04:002019-06-02T00:00:00-04:00https://jeremyforest.github.io//posts/postdoc<p>I started a postdoctoral position mid-april at New York University. I’m working on a project which is a collaboration between the Reyes lab in NYU and the Fusi lab in Columbia. The project is centered around understanding the mechanisms of learning and long-term memory using cortical cultures from mice and computational models.</p>Jeremy ForestPostdoc positionWebsite update2018-09-28T00:00:00-04:002018-09-28T00:00:00-04:00https://jeremyforest.github.io//posts/website-update<p>Hello all,</p>
<p>The version 1.0 of my website is now done. You can find a list of my papers, talks, posters and everything related in the ‘papers’ section. My CV is also available as a pdf file in the ‘cv’ section. More to come soon.</p>Jeremy ForestV1.0 functionalHello World2018-09-01T00:00:00-04:002018-09-01T00:00:00-04:00https://jeremyforest.github.io//posts/hello-world<p>Hello,</p>
<p>I’m in the process of building this website. Things will come online bits by bits. In the meantime you can check out my CV, my github page or my twitter page.</p>Jeremy ForestHello world ! First post !