Multiple-cell recording from specially designed arrays of microwire electrodes allowed analysis of anatomically defined ensemble activity from 10 different locations within the hippocampus of rats (n = 7) performing a two-lever operant version of a spatial delayed-nonmatch-to-sample task (DNMS). Application of population analysis procedures to ensembles of single-neuron activity within the CA1 and CA3 fields revealed firing patterns related to task-relevant events within a DNMS trial. The patterns were extracted via a canonical discriminant analysis in the form of "roots" that represented sources of variance in firing within the ensemble, such as phase of the task (Sample or Nonmatch), spatial position of the lever press response (left or right), and correct versus error trials. Comparison of the ensemble firing on correct versus error trials revealed important insight into ensemble information encoding, such as "miscoding" of the response position and lack of distinct encoding of the response in the Sample phase, which became increasingly vulnerable to error as a function of the duration of delay interval. The extracted discriminant scores were reflective of multiple representations within ensembles and suggested that "conjunctions" of task-relevant features could be represented effectively by small numbers of hippocampal neurons. The findings support the long-held supposition that hippocampal neurons play a critical role in the encoding and retrieval of information in recognition memory tasks.
Hippocampal complex spike cells were recorded during exploration for water delivered to cups located in various regions of an elevated platform. Place fields were recorded with a video monitoring system that recorded movements as the animal explored each of the 5 cup locations where water was delivered on the platform. Plasticity of place cell firing as a function of selective water delivery to specific cup locations on the platform was also examined. Several characteristics of place cell firing were studied that indicated a high degree of control by factors such as relative direction of movement and trajectory through the field. Time-shift analyses indicated cell firing was most representative of the place field at the time of spike occurrence. It was demonstrated that place fields possess borders in which firing was increased or decreased upon entering or leaving a particular region of the platform. The most important finding from this investigation was the pronounced degree of plasticity exhibited by place cells. Selective delivery of water to a single location on the platform was sufficient in most of the cases tested to shift the location of the field to the location where water was available. These findings suggest hippocampal place cell firing, although highly influenced by spatial and directional features of the environment, can readily change under conditions in which significant stimuli are added or removed from those locations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.