Tag Archives: neun

New neurons mature very slowly in monkeys

ResearchBlogging.orgSo, it turns out that neurogenesis in primates is quite a bit different than in rodents. It’s been over 10 years since adult neurogenesis was first described in the adult primate hippocampus and yet much of the basic work has yet to be done. That’s where this new study by Kohler et al. come in. The data are not so new actually — they were first presented at the Society for Neuroscience meeting back in 2005.

Their question was simple: at what rate do newborn neurons mature in nonhuman primates? Their methods were also simple and easy to compare to previous studies in rodents: they used BrdU to label newborn cells and then they colabeled the BrdU+ cells with immature (DCX) and mature (NeuN) neuronal markers at different cell ages: 2 days, 2 weeks, 6 weeks, 11 weeks and 23 weeks.

First, they found that after labeling with BrdU the number of BrdU+ cells increased over the next 6 weeks. This fits well with the data from Gould and suggests that precursor cells in primates may divide much more infrequently, taking up the BrdU label at injection, retaining it for several days or weeks and then giving rise to additional BrdU+ cells upon redivision, etc etc until the BrdU is diluted. Continue reading New neurons mature very slowly in monkeys

Dorsoventral vs. Septotemporal hippocampus

Everybody knows what the hippocampus is for: memory. And…maybe something about anxiety or depression? Yes – over the last 10 years or so many studies have been published showing that the hippocampus has these two roles and that the mnemonic and emotional functions of the hippocampus are associated with its septal (dorsal) and temporal (ventral) ends, respectively. This new knowledge means that we’ve had to reorient our perspective. What we see when we consider the septal hippocampus may not be the same if we only consider its temporal end. My goal here is not to provide a review of the memory vs. emotional functions of the hippocampus (btw this dichotomy is a vast oversimplification). Instead, I’d like to talk about how people have differentiated these two ends of the hippocampus in their analyses. I’m also happy to showcase a bunch of pretty anatomical images that will probably never be published in a traditional journal article. Continue reading Dorsoventral vs. Septotemporal hippocampus

Everything you always wanted to know about neurogenesis timecourses (but were afraid to ask)

Most studies of adult neurogenesis are concerned with neuronal age. Or at least they should be. This is because new neurons develop from a stage where they have no excitatory synapses to one where they have many. If we assume the traditional view that information is stored at excitatory synaptic connections, then young neurons are initially useless and only become physiologically and behaviorally meaningful when they have matured to a point where they can relay and process information. It is therefore critical that the developmental timecourse of new neurons be mapped out, so we know when new neurons become functionally relevant, or whether they might even have different functions at different ages.

Below are what I hope to be comprehensive visual collages of all published timecourse experiments, where a certain property of new neurons is examined at multiple (≥ 3) different ages. They are grouped by studies of: 1) cell survival, 2) marker expression, 3) functionality, and 4) miscellaneous studies that do not quite fit into the first 3 categories. I’ve ordered the data roughly chronologically and have included the first author’s name and publication year so you can read deeper, if needed. Indeed, if you know these studies already, a brief look at the graphs will bring back the take home message. However, since the data is stripped of text, if the studies are unfamiliar, you’ll have to go to the original source to figure out what the heck they mean (use Pubmed to at least obtain abstracts for the original studies if I didn’t provide a direct link).

Personally, I like timecourse studies for the same reason I like to have all my music albums or books visible at the same time: at a single glance they provide a lot of information – each individual stage of maturation can be interpreted within a bigger picture. The result of these many hours of work will either be a) that the purpose of adult neurogenesis will become immediately clear, or b) that we’ll all have some fancy collages to pin on our bulletin boards and look intelligent.

The survival timecourse

addition of new neurons

New neurons are born and then many die. The survival timecourse answers the questions: How many new neurons are born? Where are they born and where do they end up, anatomically? How many of them survive and can their survival be altered? Survival timecourses are typically performed by injecting animals with a mitotic marker that will label new neurons as they’re being born, e.g. ³H-thymidine (old school), BrdU (tried and true – example), or a GFP-expressing retrovirus (new school). At a later date one can then detect these birthdated new neurons and count them, see where they’re located etc.

Continue reading Everything you always wanted to know about neurogenesis timecourses (but were afraid to ask)