title: Changes in reward contingency modulate the trial-to-trial variability of hippocampal place cells.
abstract: Pyramidal cells in the rodent hippocampus often exhibit clear spatial tuning. Theories of hippocampal function suggest that these "place cells" implement multiple, independent neural representations of position (maps), based on different reference frames or environmental features. Consistent with the "multiple maps" theory, previous studies have shown that manipulating spatial factors related to task performance modulates the within-session variability (overdispersion) of cells in the hippocampus. However, the influence of changes in reward contingency on overdispersion has not been examined. To test this, we first trained rats to collect food from three feeders positioned around a circular track (task(1)). When subjects were proficient, the reward contingency was altered such that every other feeder delivered food (task(2)). We recorded ensembles of hippocampal neurons as rats performed both tasks. Place cell overdispersion was high during task(1) but decreased significantly during task(2), and this increased reliability could not be accounted for by changes in running speed or familiarity with the task. Intuitively, decreased variability might be expected to improve neural representations of position. To test this, we used Bayesian decoding of hippocampal spike trains to estimate subjects' location. Neither the amount of probability decoded to subjects' position (local probability) nor the difference between estimated position and true location (decoding accuracy) differed between tasks. However, we found that hippocampal ensembles were significantly more self-consistent during task(2) performance. These results suggest that changes in task demands can affect the firing statistics of hippocampal neurons, leading to changes in the properties of decoded neural representations.
authors: Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA.
authors: Andrew M
authors: AM
authors: Wikenheiser
authors: A David
authors: AD
authors: Redish
references: Neuroscience. 2008 May 2;153(2):349-60
references: 18406064
references: J Neurosci. 1997 Aug 1;17(15):5900-20
references: 9221787
references: J Neurophysiol. 1998 Feb;79(2):1017-44
references: 9463459
references: J Neurophysiol. 2004 May;91(5):2259-72
references: 14736863
references: Hippocampus. 1997;7(1):15-35
references: 9138665
references: Neuron. 2004 Apr 22;42(2):283-95
references: 15091343
references: Nat Rev Neurosci. 2006 May;7(5):358-66
references: 16760916
references: Hippocampus. 2007;17(12):1209-29
references: 17764083
references: PLoS Biol. 2010 Jun 22;8(6):e1000403
references: 20585373
references: Brain Res. 1971 Nov;34(1):171-5
references: 5124915
references: Neuron. 2010 Jul 15;67(1):25-32
references: 20624589
references: Nature. 2005 Oct 20;437(7062):1158-61
references: 16237445
references: J Neurosci. 2007 Nov 7;27(45):12176-89
references: 17989284
references: Trends Cogn Sci. 2009 Feb;13(2):55-64
references: 19135406
references: Hippocampus. 1996;6(3):247-70
references: 8841825
references: Network. 2003 Nov;14(4):629-45
references: 14653496
references: Neuroscience. 2002;111(3):553-66
references: 12031343
references: J Neurophysiol. 2009 Mar;101(3):1575-87
references: 19144741
references: J Neurosci. 2010 Mar 31;30(13):4613-25
references: 20357112
references: Exp Brain Res. 1983;52(1):41-9
references: 6628596
references: J Physiol. 1969 Jun;202(3):699-718
references: 5789945
references: J Neurosci. 1989 Aug;9(8):2737-63
references: 2769364
references: Neuron. 2010 Mar 11;65(5):695-705
references: 20223204
references: Science. 1993 Aug 20;261(5124):1055-8
references: 8351520
references: J Neurophysiol. 1967 Sep;30(5):1043-71
references: 6055348
references: Neuron. 1999 Jun;23(2):209-26
references: 10399928
references: J Neurosci. 1998 Sep 15;18(18):7411-25
references: 9736661
references: J Exp Biol. 1996 Jan;199(Pt 1):173-85
references: 8576689
references: Proc Natl Acad Sci U S A. 1998 Mar 17;95(6):3182-7
references: 9501237
references: J Neurosci. 1995 Nov;15(11):7079-94
references: 7472463