LIMBO: Analysis of hippocampal circuitry

CA differentiation
The aim is to understand the relation between the organization of the hippocampus and its function in memory formation [2,4], along the lines suggested by David Marr. The central hypothesis, shared with several investigators, is that CA3 can be viewed as the core autoassociator [5]: we have shown that even with the storage of multiple spatial maps essentially the same constraints apply as with discrete "episodic memory" firing patterns [9].

Our early proposal of a specific role for each of the two main input systems to the CA3 field [1] is consistent with experimental findings [see JM Lassalle, T Bataille & H Halley, Neurobiol Learning and Mem 73:243-257 (2000) and I Lee & RP Kesner, Hippocampus 14:66-76 (2004)].

An analytical approach has been introduced for understanding quantitatively the operations performed by the Schaffer collaterals [3,7], and later extended to include the effect of direct entorhinal projections to CA1 [8]. Similar measures have been applied, in collaboration with Edmund Rolls and his lab, to monkey hippocampal recordings [6], and to rat hippocampal multi-unit recordings from the lab of Carol Barnes and Bruce McNaughton.

An approach based on simulations has been introduced more recently [11], modeled in part after neurophysiological recordings from the Tucson lab, and applied to assess the neural mechanisms that may underlie temporal prediction in the hippocampus: associative plasticity and firing rate adaptation. The simulations offer a general quantitative approach to address the main outstanding question [3,10]: what is the exact contribution of CA1 to hippocampal processing? or, in other words, what is the computational significance of the CA3-CA1 differentiation in mammals [12]? A new light on this issue has been cast by exciting novel findings from the Trondheim lab [13], with whom is active an intense collaboration, and whose website you should visit for more information on their experiments [14]. A wider collaboration has started since February, 2008 within the EU SPACEBRAIN project.

The discovery of grid cells in Trondheim, and of their locally coherent transition dynamics when CA3 cells undergo global remapping [15] has stimulated ideas about the origin of the grid fields [16] which contrast with the popular attractor and interfering oscillator models; and it has also led to reassess the role of the dentate gyrus [17] in generating new CA3 representations (current work by EC, AT). The theoretical context for this work and its commonalities to seemingly unrelated research is reviewed in [18].

References:

  1. AT & ET Rolls, Hippocampus 2:189-199 (1992). Poorly scanned copy.
  2. AT & ET Rolls, Hippocampus 4:374-391 (1994). Poorly scanned copy.
  3. AT, J Comput Neurosci 2:259-272 (1995)
  4. AT, WE Skaggs & CA Barnes, Hippocampus 6:666-674 (1996) You are welcome to ftp an early draft.ps
  5. ET Rolls, AT, D Foster & C Perez-Vicente, Neural Networks 10:1559-1569 (1997)
  6. ET Rolls, AT, RG Robertson, P Georges-Francois & SP, J Neurophysiol 79:1797-1813 (1998)
  7. SRS, SP, ET Rolls & AT, proceedings in Information Theory and the Brain, p. 257-272, Cambridge UP, (2000)
  8. CFM, SP, ET Rolls & AT, proceedings in Information Theory and the Brain, p. 273-289, Cambridge UP, (2000)
  9. FPB & AT, Phys Rev E 58:7738 (1998)
  10. AT & IS, Cognitive Neuropsychology 12:557-575 (2002). You are welcome to download a draft.ps
  11. AT, Hippocampus 14:539-556 (2004). You are welcome to download a draft.pdf
  12. AT, Neuroinformatics 2:361-366 (2004). You are welcome to download a draft.pdf
  13. S Leutgeb, JK Leutgeb, AT, M-B Moser & EI Moser, Science 305:1295-1298 (2004)
  14. JK Leutgeb, S Leutgeb, AT, R Meyer, CA Barnes, BL McNaughton, M-B Moser & EI Moser, Neuron 48:345-358 (2005)
  15. M Fyhn, T Hafting, AT, MB Moser, EI Moser, Nature 446: 190-194 (2007)
  16. EK, AT, manuscript submitted to Hippocampus (2008)
  17. AT, A Tashiro, MP Witter, EI Moser, Neuroscience 154:1155-1172 (2008)
  18. AT,  Ch.3 in Cognitive Biology (Tommasi et al, eds), MIT press (2009)
Last updated 06/07/08. Back to LIMBO, CNS, SISSA.