TY - JOUR
T1 - Unmasking the CA1 ensemble place code by exposures to small and large environments
T2 - More place cells and multiple, irregularly arranged, and expanded place fields in the larger space
AU - Fenton, André A.
AU - Kao, Hsin Yi
AU - Neymotin, Samuel A.
AU - Olypher, Andrey
AU - Vayntrub, Yevgeniy
AU - Lytton, William W.
AU - Ludvig, Nandor
PY - 2008/10/29
Y1 - 2008/10/29
N2 - In standard experimental environments, a constant proportion of CA1 principal cells are place cells, each with a spatial receptive field called a place field. Although the properties of place cells are a basis for understanding the mammalian representation of spatial knowledge, there is no consensus on which of the two fundamental neural-coding hypotheses correctly accounts for how place cells encode spatial information. Within the dedicated-coding hypothesis, the current activity of each cell is an independent estimate of the location with respect to its place field. The average of the location estimates from many cells represents current location, so a dedicated place code would degrade if single cells had multiple place fields. Within the alternative, ensemble-coding hypothesis, the concurrent discharge of many place cells is a vector that represents current location. An ensemble place code is not degraded if single cells have multiple place fields as long as the discharge vector at each location is unique. Place cells with multiple place fields might be required to represent the substantially larger space in more natural environments. To distinguish between the dedicated-coding and ensemble-coding hypotheses, we compared the characteristics of CA1 place fields in a standard cylinder and an approximately six times larger chamber. Compared with the cylinder, in the chamber, more CA1 neurons were place cells, each with multiple, irregularly arranged, and enlarged place fields. The results indicate that multiple place fields is a fundamental feature of CA1 place cell activity and that, consequently, an ensemble place code is required for CA1 discharge to accurately signal location.
AB - In standard experimental environments, a constant proportion of CA1 principal cells are place cells, each with a spatial receptive field called a place field. Although the properties of place cells are a basis for understanding the mammalian representation of spatial knowledge, there is no consensus on which of the two fundamental neural-coding hypotheses correctly accounts for how place cells encode spatial information. Within the dedicated-coding hypothesis, the current activity of each cell is an independent estimate of the location with respect to its place field. The average of the location estimates from many cells represents current location, so a dedicated place code would degrade if single cells had multiple place fields. Within the alternative, ensemble-coding hypothesis, the concurrent discharge of many place cells is a vector that represents current location. An ensemble place code is not degraded if single cells have multiple place fields as long as the discharge vector at each location is unique. Place cells with multiple place fields might be required to represent the substantially larger space in more natural environments. To distinguish between the dedicated-coding and ensemble-coding hypotheses, we compared the characteristics of CA1 place fields in a standard cylinder and an approximately six times larger chamber. Compared with the cylinder, in the chamber, more CA1 neurons were place cells, each with multiple, irregularly arranged, and enlarged place fields. The results indicate that multiple place fields is a fundamental feature of CA1 place cell activity and that, consequently, an ensemble place code is required for CA1 discharge to accurately signal location.
KW - CA1
KW - Extracellular recording
KW - Hippocampal function
KW - Hippocampus
KW - Neuronal ensembles
KW - Place cells
KW - Spatial cognition
UR - http://www.scopus.com/inward/record.url?scp=56149120491&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=56149120491&partnerID=8YFLogxK
U2 - 10.1523/JNEUROSCI.2862-08.2008
DO - 10.1523/JNEUROSCI.2862-08.2008
M3 - Article
C2 - 18971467
AN - SCOPUS:56149120491
SN - 0270-6474
VL - 28
SP - 11250
EP - 11262
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 44
ER -