The Knierim Lab studies the behavioral and cognitive correlates of the hippocampal formation—a brain region that is critical for forming and storing long-term memories. Read more about our research.
Bharath Krishnan receives Kavli fellowship
Bharath Krishnan, a fourth year BME PhD student in the lab, was awarded a Kavli Neuroscience Discovery Institute (NDI) fellowship for the research project “Mechanisms governing modulation of path integration gain in the Medial Entorhinal Cortex”. The fellowship will help fund Bharath’s graduate research in the laboratory for the next two years.
Heekyung Lee publishes in Current Biology
Heekyung Lee recently published research in Current Biology investigating a functional gradient along the transverse axis of the hippocampal CA3 subfield. The transition from pattern-separated outputs (dominant in the more proximal CA3) to pattern-completed outputs (dominant in the more distal CA3) is altered in aging rats impaired in the water maze task. Age-impaired rats show reduced orthogonalization in proximal CA3 but show normal (i.e., generalized) representations in distal CA3, with little evidence of a functional gradient. Her experiments support the hypotheses that the age-related bias toward hippocampal pattern completion is due to the loss in AI rats of the normal transition from pattern separation to pattern completion along the CA3 transverse axis.
Brian Li graduates with BS in Neuroscience
Congratulations to Brian Li for graduating with honors with a BS in Neuroscience here at JHU. He is currently working in the lab as a research technician while applying to medical school.
Will Hockeimer accepts postdoc position in Collinger lab at Univ of Pittsburgh
Will Hockeimer will be working on brain-computer interface projects as a postdoctoral associate with Dr. Jennifer Collinger at the Rehab Neural Engineering Labs at the Univ. of Pittsburgh. Good luck to Will as he embarks on this exciting new phase in his career.
Will Hockeimer Delivers Thesis Seminar
Will Hockeimer successfully defended his Ph.D. dissertation on Dec 11, 2020 and presented his public Thesis Seminar on February 17, 2021, titled “Non-spatial information encoding in hippocampal area CA1.” Congratulations, Dr. Hockeimer!
Shan Wang Publishes Dissertation Research in Current Biology
Former graduate student Chia-Hsuan (Shan) Wang recently published her dissertation research in the journal Current Biology. The study demonstrated that the boundaries between surface textures on an open field can create distortions in the brain’s “cognitive map.” These distortions may be related to how the brain segments space into separate compartments (e.g., how a border between floor tile and carpet segments space psychologically into a kitchen vs. a dining room). They may also explain perceptual illusions that occur when people estimate distances across such boundaries.
See nice “Dispatch” by Ryan Place and Doug Nitz describing these results in the journal:
Leo Lee Defends Master’s Dissertation
Leo Lee successfully defended his Master’s Dissertation on March 31, 2020. Leo’s dissertation was titled “Translating the Optical Imaging Technique for Measuring Neuronal Activity from Mice to Rats.” Leo worked with former Asst. Research Scientist Xiaojing Chen and current Postdoctoral Fellow Yueqing Zhou to pioneer the use of in vivo, miniscope Ca++ imaging in freely moving animals. Congratulations Leo on a great thesis!
Doug GoodSmith and Heekyung Lee Publish Paper in The Journal of Neuroscience
In their continuing investigations of the heterogeneity of response types in the CA3 and DG regions of the hippocampus, Doug and Heekyung published a new study showing that proximal CA3 (CA3c) pyramidal cells and granule cells and mossy cells of the dentate gyrus act as a functional unit that appears to support pattern separation processes in the hippocampus (GoodSmith et al., J Neurosci 2019). Using a classifier that Doug developed for his dissertation, they were able to identify with confidence recordings from each of these anatomically close cell types and showed that they all had similar remapping properties in a local-global cue mismatch manipulation. Importantly, these data reinforce the extremely sparse nature of granule cell firing, and suggest strongly that the majority of all prior published extracellular recordings of DG were mostly from mossy cells, rather than the granule cells that had been assumed.
Ravi Jayakumar defends dissertation research
Ravi Jayakumar, Ph.D., successfully defended his dissertation, “Self Estimation in Complex Biological Systems” on Sept. 13th, 2019. Part of his dissertation was based on the development of a new augmented reality system for freely-moving rodents developed in collaboration with Manu Madhav and Noah Cowan, Ravi’s adviser, in the Mechanical Engineering Department. See https://www.nature.com/articles/s41586-019-0939-3 Congratulations, Dr. Jayakumar!
Welcome New Postdoctoral Fellow Yueqing Zhou and Graduate Student Bharath Krishnan!
Dr. Yueqing Zhou joins the lab from Peking University, where she obtained her Ph.D., and Stanford University, where she was a visiting student. Yueqing will begin experiments using head-mounted miniscopes to track calcium activity in neurons in freely moving rats. Welcome to Baltimore, Yueqing!
Bharath Krishnan, graduate student in Biomedical Engineering, has decided to join the laboratory to pursue his dissertation research. Bharath will begin recordings of the medial entorhinal cortex in our augmented reality “Dome” apparatus, in collaboration with the Cowan lab of Mechanical Engineering. Welcome, Bharath!
Doug GoodSmith Successfully Defends His Ph.D. Thesis
Doug GoodSmith, Ph.D., successfully defended his Ph.D. dissertation on July 17, 2019. His dissertation was titled “Firing correlates and mnemonic functions of dentate gyrus granule cells and mossy cells.” This work was the result of a long collaboration between the Knierim lab and Kim Christian of the lab of Hongjun Song (formerly at Hopkins, now at UPenn). Doug will deliver his public seminar on August 16 at 10:00 am at the Mind/Brain Institute. Congratulations, Doug!
Shan Wang Successfully Defends Her Ph.D. Thesis
Congratulations to Chia-Hsuan (Shan) Wang, Ph.D., who successfully defended her Ph.D. dissertation on May 6, 2019 and presented her public thesis seminar on June 13, 2019. The title of her thesis was “The Cognitive Map and Compartmentalized Space: Neural Representations of Surface Cue Boundaries.” Congratulations, Shan!
Congratulations to Ravi, Manu, and Francesco for Nature paper
March 24, 2019: In collaboration with the LIMBS lab of Noah Cowan (JHU Mechanical Engineering) and the lab of Tad Blair (UCLA), we recently published a paper in Nature showing that the path integration system has a dynamic gain variable that can be recalibrated with experience. We used an augmented reality system to produce a continuous conflict between self-motion cues and visual landmarks, in that rotation of the landmarks produced an illusion that the rat ws running faster or slower than it really was. When we subsequently turned the landmarks off, we showed that CA1 place cells had recalibrated the rate at which they updated the rat’s position based on path integration.
Cheng and Xiaojing publish Science paper
March 24, 2019: Last fall, we published a paper in Science showing that the lateral entorhinal cortex represented the location of the rat in an egocentric framework relative to external locations or items. This result confirms predictions from a model that the LEC encodes the locations of “other” items in the environment from a first-person perspective, as opposed to the MEC, which encodes the position of the “self” in allocentric coordinates. The egocentric coding of LEC is consistent with the notion that the LEC provides the hippocampus with information about the content of an episode, in accordance with the first-person perspective that characterizes episodic memories.
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