HARDCASTLE, Kiah, Neural code for navigation, MBC, April 2, 2018

<p class="MsoNormal" >HARDCASTLE, Kiah,&nbsp; Neural code for navigation,&nbsp; MBC, April 2, 2018

Kiah is a GS working in the lab of Lisa Giocomo&nbsp; and is co-advised by Surya Ganguli.

This is today at 5:10PM in the MBC series.

abstract is here:

&nbsp;“<b>Understanding neural codes for navigation in medial entorhinal cortex</b>”.

&nbsp;

<b>Medial entorhinal grid cells </b>display strikingly symmetric spatial firing patterns.

&nbsp;The clarity of these patterns motivated the use of specific activity pattern shapes to classify entorhinal cell types.

While this approach successfully revealed cells <b>that encode boundaries, head direction, and running speed, it&nbsp;left a majority of cells unclassified, </b>and its pre-defined nature may have missed unconventional, yet important coding properties.

&nbsp;Here, we apply an unbiased statistical approach to search for cells that encode navigationally relevant variables. This approach successfully classifies the majority of entorhinal cells and reveals unsuspected entorhinal coding principles.

&nbsp;First, we find a high degree <b>of mixed selectivity and heterogeneity in superficial entorhinal&nbsp;neurons</b>. Second, we discover a dynamic and remarkably adaptive code for space that enables <b>entorhinal cells to rapidly encode navigational information accurately at high running speeds</b>. Combined, these observations advance our current understanding of the mechanistic origins and functional implications of the entorhinal code for&nbsp;navigation.

shows a gerbil navigating a maze.

it builds up a map of the maze over a # of days.

penguins,&nbsp; fruit bats,&nbsp; scrubs jays,&nbsp; humans...we all do this.

so,&nbsp; what info do you need to know how to navigate?

need to know your position,and what direction you are facing, head direction,

speed, and distance to landmarks.

how and where encoded.

we look at&nbsp; Entorhinal cortex = EC.

shows her set-up in Lisa's lab...

implant in <b>MEC = medial entorhinal cortex</b>.

&nbsp;into a rat...&nbsp;&nbsp; tetrodes. rat with a hat.

and LEDs in the hat&nbsp; (to help find it on video)...

record&nbsp; over about a 40 minute session.

neural spikes and also record x/y position; head direction, speed..

we find grid cells.

get a tuing curve for positions in the cage.

shows high rate positions...&nbsp; the "grid score."

but also&nbsp; border score&nbsp; along the border of the cage

but also cells that seem to fire with head direction.

and also speed cells.

see eg Hafting 2005... Kropff in 2015.

she shows 794 cells collected in 14 mice.

but maybe 60% of cells just do NOT fit any schema

ie NOT&nbsp; position, speed, border, nor head direction.

so, the classically-defined cell types are the MINORITY of cells.

hd= head direction...

This is <b>Hardcastle in Neuron in 2017...</b>

use a combo of position, head direciton and running speed and

then do linear non linenar Poisson model.

try to fit this model to the actual firing rate.

conjunctive cells...

now,&nbsp; NON-identified cells are only perhaps 30% of total instead of 55%.

P = position;&nbsp; H = head direction and S = speed .

(also additional current and future work... )

&nbsp;

&nbsp;</p>