Re: Place and Grid field Analysis Ideas

Here are two ideas for data analysis that could be used to explore the hc-2/3 data provided by the Buzsaki group:

(1) I once plotted CA1 place field size (the distance between the first and last spike) as a function of velocity (the amount of time it took the rat to run between the spikes). If you look at the figure I uploaded, the first interesting thing to note is that there are striations. These striations are due to the fact that hippocampal place field size is a somewhat quantal function of the number of theta cycles that the neuron is active for (for example, if the rat is moving at 3cm/theta cycle, then a place field can be roughly 3,6,9,12... cm in size). You will also note that these striations "fan out". This suggests that the distance the rodent covers within a theta cycle increases with velocity, which is somewhat counter-intuitive: theta frequency should increase with velocity (Michael Recce's thesis shows a nice curve that increases and then plateaus). In my personal experience, sometimes theta frequency changes with velocity and other times it does not. So here are a few questions- "Does place field size increase as a function of velocity or were my data the abnormality?", "Does theta frequency change as a function of velocity?", "Is there a novelty/familiarity effect?",  "Is the size increase with velocity also present in the entorhinal cortex?"

In my experiments on circular tracks, there was an issue that velocity was coupled to location (rats moved slow when they were near a food dish and fast when they were away from a food dish). These data (open-field, linear tracks and wheels) provide a great database to explore this phenomenon more intensively than my data could. 

(2) It may be worthwhile to re-visit the "center-of-mass shift" phenomenon (Mehta et al., 1997) with respect to the different sub-fields of the hippocampus and how this alters the "phase-position" density profiles (Mehta et al., 2002). Note that CA3 may or may not show a COM shift (Lee et al., 2004). I am unaware of anyone looking at this in the dentate. Hafting et al., (2008) explored center of mass within the MEC, but this provides a chance to replicate results. 

Please email me if you are interested: Drewmaurer at ufl dot edu