Different coding schemes in dorsal and ventral hippocampus

1. Different coding schemes in dorsal and ventral hippocampus Sebastien Royer Jagdish Patel

2. rodent primate cortex cortex P D V A Space representation Other-than-space representation

3. Extrapolation from existing data ? ? dMEC Prediction:giant place fields in VH small larger ? Jung et al. Hippocampus (1994) Hafting et al. Nature 2005 Maurer, Vanrhoads, Sutherland, Lipa, McNaughton, Hippocampus 2005 Hafting et al. Science 2008

4. water port 7-arm radial zig-zag maze open field

5. Absence of place cells in the ventral hippocampus? Ventral CA3 Large, diffuse or multiple peak firing fields, low peak firing rates Dorsal CA3 1 m Discrete place fields, high peak firing rates

6. Absence of place cells in the ventral hippocampus? Field size (contour) % area spatial information stability (R: first half/second half) bits Field size (# pixels) % area

7. Dorsal CA3 neurons have small, single, direction-specific place fields (as in McNaughton, Barnes, O’Keefe, Brain Res, 1983) 1 neuron # 329

8. Ventral CA3 neurons fire on multiple-arms, in a direction-specific manner

9. vCA3 neurons fire on multiple-arms % of arms # of active arms vCA3 neurons are more direction-specific than dCA3 % of cells r vCA3

10. Ventral CA3 neurons are arm type-specific (only on reward-bound journeys)

11. ventral CA3 Ventral CA3 population increases firing rate on reward-bound travels dorsal CA3

12. ventral CA3 Ventral CA3 neurons in the zig-zag maze respond to local geometrical features dorsal CA3

13. Firing fields of vCA3 neurons are larger and less directional right journey right journey left journey

14. vCA3 Firing patterns of vCA3 neurons in the zig-zag maze reflect distances from the goal vCA3 L R R L int

15. Paucity of theta oscillations in ventral hippocampus

16. Paucity of theta-rhythmic vCA3 neurons dCA3 interneurons vCA3 interneurons 107 35 dCA3 pyramidal cells vCA3 pyramidal cells 1313 162

17. Fewer vCA3 neurons show phase precession vCA3 pyramidal cells dCA3 pyramidal cell

18. Differences between vCA3 and dCA3 • vCA3 neurons fired on multiple arms of the radial maze • firing fields of vCA3 often formed a ring (similar mechanisms in each arm) • vCA3 neurons differentiated between open and closed arms in the radial maze. • Both arm type differentiation and arm segment generalization (ring) of v CA3 depended on the direction of travel • vCA3 neurons showed mirror-symmetric firing patterns in the zig-zag maze (distance from the goal) • cone-shaped place fields were exceptionally rare in vCA3 • LFP theta power in vCA3 was smaller than in dCA3 • Only a small fraction of vCA3 pyramidal cells and interneurons showed theta rhythmicity • Only a small fraction of vCA3 neurons showed phase precession

19. Hypothesis:Ventral hippocampus in the rat is functionally similar to pes and body of the primate hippocampusDorsal hippocampus may be functionally similar to the tail tail pes/uncus body VH

20. CA1 Differential CA3 projections (ventral CA3 strongly projects to granule cells) mol layer CA1 mol layer CA1 Li, Somogyi, Ylinen, Buzsaki, J comp Neurol 1994