Translating Time

Instructions for the use of this site.


In order to use the “Translate” and “Predict” functions, you should first note that all input and output is in Postconceptional Days (PC Days) and not Postnatal Days, an essential feature of the model as birth varies widely with respect to maturational state.   If the information you presently have is in postnatal days, the information you need, and some considerations are described below.  You must also have a particular class of events in mind for "Translate" or a specific event for “Predict”.  By  “class of events” we mean that the prediction depends in some cases on the Location of the event in the brain (typically a brain region but also includes "Whole Brain" for brain growth or “Whole Organism” for behavioral events). The maturational Process must also be identified. The Locations and Processes of particular importance are “Cortex”, “Retina”, and “Neurogenesis”.


Postconceptional Day

All days are estimated from conception, not birth. To calculate a postnatal day, subtract gestation length from the given output of Postconceptional Days. The gestation length for each species is listed in Species Information. In our model, birth is considered postnatal day 0, and all empirical studies are adjusted to that convention.  For example, an event that occurs 10 days after birth will occur on “Postnatal Day 9.” The majority of studies follow this convention, although a few studies refer to birth as Postnatal day 1 .


Location and Process Classifications

In the “Translate” section of the website, a user can select a post-conceptional date in any of our eighteen species and determine an analogous post-conceptional day for a different one of the species. Users need to select a location and a process for the comparison in question. There are 10 locations and 12 process classifications. In the current model, cortical neurogenesis is delayed in all non-glires species, and retinal neurogenesis is delayed in the cat, so any events corresponding to either of these combinations will have special transformations. There are 10 locations that can be selected from, and there are 12 processes.  

In the “Predict” section, the predicted timing for any of the 271 events can be determined for any of the 18 species, for a total of 4878 combinations. 

Below are descriptions of the locations and processes:


 Brain Stem – Encompasses the spinal cord, medulla, and mesencephalon

 Cerebellum – The presumptive cerebellum

 Limbic System – Amygdala, hippocampus, septum, olfactory bulbs, olfactory cortex, subicular corticies, entorhinal cortex

 Thalamus – All thalamic nuclei

 Striatum – Globus pallidus, caudate nucleus

 Cortex – Isocortex

 Whole Brain – Gross brain growth

 Whole Organism – Behavioral events

 Sensory Periphery – Peripheral nervous system

 Retina – Retina, retinal ganglion cells


Neurogenesis – Cell cycle exit for any group of cells

Axon Extension – When axons arrive at targets, form synapses, axon growth

Segregation – Differentiation of a population of cells

Gaba Cortex – Gabaergic cells that have origins in the striatum or isocortex

Subtractive Event – Cell death

Retinal Waves – Patterns of developing retinal activity

Synapse Elimination – Decrease in synapse numbers

Sensorimotor – Behavioral or reflexive event

Brain Growth – Gross brain development

Myelination – First wrap of a glial cell around a neuron

Electrophysiology – Onset of electrical activity