15 research outputs found
Geniculo-Cortical Projection Diversity Revealed within the Mouse Visual Thalamus
This is the final version of the article. It was first available from PLOS via http://dx.doi.org/10.1371/journal.pone.0144846All dLGN cell co-ordinates, V1 injection sites, dLGN boundary coordinates, experimental protocols and analysis scripts are available for download from figshare at https://figshare.com/s/36c6d937b1844eec80a1.The mouse dorsal lateral geniculate nucleus (dLGN) is an intermediary between retina and primary visual cortex (V1). Recent investigations are beginning to reveal regional complexity in mouse dLGN. Using local injections of retrograde tracers into V1 of adult and neonatal mice, we examined the developing organisation of geniculate projection columns: the population of dLGN-V1 projection neurons that converge in cortex. Serial sectioning of the dLGN enabled the distribution of labelled projection neurons to be reconstructed and collated within a common standardised space. This enabled us to determine: the organisation of cells within the dLGN-V1 projection columns; their internal organisation (topology); and their order relative to V1 (topography). Here, we report parameters of projection columns that are highly variable in young animals and refined in the adult, exhibiting profiles consistent with shell and core zones of the dLGN. Additionally, such profiles are disrupted in adult animals with reduced correlated spontaneous activity during development. Assessing the variability between groups with partial least squares regression suggests that 4?6 cryptic lamina may exist along the length of the projection column. Our findings further spotlight the diversity of the mouse dLGN?an increasingly important model system for understanding the pre-cortical organisation and processing of visual information. Furthermore, our approach of using standardised spaces and pooling information across many animals will enhance future functional studies of the dLGN.Funding was provided by a Wellcome Trust grant jointly awarded to IDT and SJE (083205, www.wellcome.ac.uk), and by MRC PhD Studentships awarded to MNL and ACH (http://www.mrc.ac.uk/)
Supplementary Material for: Comparison of Dolphins' Body and Brain Measurements with Four Other Groups of Cetaceans Reveals Great Diversity
<p>We compared mature dolphins with 4 other groupings of mature
cetaceans. With a large data set, we found great brain diversity among 5
different taxonomic groupings. The dolphins in our data set ranged in
body mass from about 40 to 6,750 kg and in brain mass from 0.4 to 9.3
kg. Dolphin body length ranged from 1.3 to 7.6 m. In our combined data
set from the 4 other groups of cetaceans, body mass ranged from about 20
to 120,000 kg and brain mass from about 0.2 to 9.2 kg, while body
length varied from 1.21 to 26.8 m. Not all cetaceans have large brains
relative to their body size. A few dolphins near human body size have
human-sized brains. On the other hand, the absolute brain mass of some
other cetaceans is only one-sixth as large. We found that brain volume
relative to body mass decreases from Delphinidae to a group of
Phocoenidae and Monodontidae, to a group of other odontocetes, to
Balaenopteroidea, and finally to Balaenidae. We also found the same
general trend when we compared brain volume relative to body length,
except that the Delphinidae and Phocoenidae-Monodontidae groups do not
differ significantly. The Balaenidae have the smallest relative brain
mass and the lowest cerebral cortex surface area. Brain parts also vary.
Relative to body mass and to body length, dolphins also have the
largest cerebellums. Cortex surface area is isometric with brain size
when we exclude the Balaenidae. Our data show that the brains of
Balaenidae are less convoluted than those of the other cetaceans
measured. Large vascular networks inside the cranial vault may help to
maintain brain temperature, and these nonbrain tissues increase in
volume with body mass and with body length ranging from 8 to 65% of the
endocranial volume. Because endocranial vascular networks and other
adnexa, such as the tentorium cerebelli, vary so much in different
species, brain size measures from endocasts of some extinct cetaceans
may be overestimates. Our regression of body length on endocranial
adnexa might be used for better estimates of brain volume from endocasts
or from endocranial volume of living species or extinct cetaceans.</p