Neurobiology and Anatomy Department at The University of Texas Medical School at Houston
Department of Neurobiology and Anatomy
The Department ofNeurobiology

James J. Knierim, Ph.D.

Associate Professor
Telephone: 713.500.5622
E-mail: james.j.knierim@uth.tmc.edu


Neural Network Mechanisms For Spatial Learning And Navigation

James Knierim, Ph.D. - Assistant ProfessorThe hippocampus is a brain structure that has long been implicated in learning and memory processes. In rats, the hippocampus appears to be especially important for spatial learning. Accordingly, the most salient firing correlate of hippocampal neurons is the spatial location of the animal. The ensemble activity of these "place cells" constitutes an internal cognitive map of the rat’s environment which may serve as a framework to organize and store episodic memory. Another class of cells, located in brain areas associated with the hippocampus, are the "head direction cells," which serve as an internal compass to orient the cognitive map. The firing properties of place cells and head direction cells are controlled by a complex interaction between internally generated, self-motion cues (e.g., vestibular information) and external sensory input (e.g., visual landmarks). The exact nature of this interaction, and how it changes during the learning of a spatial task, are not well understood.

This laboratory studies these questions at the neural systems level by using state-of-the-art techniques to record populations of single neurons in the hippocampus simultaneously with populations of single neurons in its input and output structures. We hope to understand how the multimodal sensory information represented in the input structures is transformed into a spatial map in the hippocampus, and how this map is then used to underlie both the navigational abilities of the rat and the other hippocampal-dependent forms of learning (e.g., trace conditioning, context-dependent memory).

A) Waveforms from 65 well-isolated neurons recorded simultaneously from CA1 and CA3 during a 20-min sleep session. Each group of 4 waveforms represents the average waveform for that cell recorded on each of the 4 channels of a tetrode. (B) Place fields for 12 of the units in (A) when the rat subsequently performed a foraging session in a cylindrical enclosure.
(A) Waveforms from 65 well-isolated neurons recorded simultaneously from CA1 and CA3 during a 20-min sleep session. Each group of 4 waveforms represents the average waveform for that cell recorded on each of the 4 channels of a tetrode. (B) Place fields for 12 of the units in (A) when the rat subsequently performed a foraging session in a cylindrical enclosure.

For example, are there separate brain areas that encode the internal and external sensory inputs onto place cells? How do the neurons in these areas interact to construct a coherent, stable representation of a spatial environment? Does the nature of this interaction change during the exploration and learning of a new environment? Do spatially selective place cells acquire other characteristics as an animal learns a task? Standard recording techniques limit the population analysis of these kinds of questions to well-learned, stereotyped behaviors that can be performed repeatedly while neurons are recorded one-by-one over many weeks to months. The advantage of the powerful new simultaneous recording techniques is that 50-100 neurons can be recorded in a single trial, thus enabling an analysis of the changes in neuronal populations over time as an animal acquires a spatial learning task.

Selected Reading

Knierim, JJ. (2002) Dynamic interactions between local surface cues, distal landmarks, and intrinsic circuitry in hippocampal place cells. J. Neurosci. 22:6254-6264.

Knierim, JJ, Rao, G. (2003) Distal landmarks and hippocampal place cells: Effects of relative translation vs. rotation. Hippocampus 13:604-617.

Lee, I, Rao, G, Knierim, JJ. (2004) A double dissociation between hippocampal subfields: Differential time course of CA3 and CA1 place cells for processing changed environments. Neuron 42:803-815.

Lee, I, Yoganarasimha, D, Rao, G, Knierim, JJ. (2004) Comparison of population coherence of place cells in hippocampal subfields CA1 and CA3. Nature 430:456-459.

Hargreaves, EL, Rao, G, Lee, I, Knierim, JJ. (2005) Major dissociation between medial and lateral entorhinal input to dorsal hippocampus. Science 308:1792-1794.

Yoganarasimha, D, Knierim, JJ. (2005) Coupling between place cells and head direction cells during relative translations and rotations of distal landmarks. Exp. Brain Res. 160:344-359.

Yoganarasimha, D, Yu, X, Knierim, JJ. (2006) Head direction cell representations maintain internal coherence during conflicting proximal and distal cue rotations: Comparison with hippocampal place cells. J. Neurosci. 26:622-631.

Yu, X, Knierim, JJ, Lee, I, Shouval, HS. (2006) Simulating place field dynamics using spike timing dependent plasticity.  Neurocomputing 69:1253-1259.

Yu, X, Yoganarasimha, D, Knierim, JJ. (2006) Backward shift of head direction tuning curves of the anterior thalamus: Comparison with CA1 place fields.
Neuron 52:717-729.

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