Electrophysiological characterization of interlaminar entorhinal connections: an essential link for re-entrance in the hippocampal-entorhinal system.
The hippocampal formation communicates with the neocortex mainly through the adjacent entorhinal cortex. Neurons projecting to the hippocampal formation are found in the superficial layers of the entorhinal cortex and are largely segregated from the neurons receiving hippocampal output, which are located in deep entorhinal layers. We studied the communication between deep and superficial entorhinal layers in the anaesthetized rat using field potential recordings, current source density analysis and single unit measurements. We found that subiculum stimulation was able to excite entorhinal neurons in deep layers. This response was followed by current sinks in superficial layers. Both responses were subject to frequency dependent facilitation, but not depression. Selective blockade of deep layer responses also abolished subsequent superficial layer responses. This clearly demonstrates a functional deep-to-superficial layer communication in the entorhinal cortex, which can be triggered by hippocampal output. This pathway may provide a means by which processed hippocampal output is integrated or compared with new incoming information in superficial entorhinal layers, and it constitutes an important link in the process of re-entrance of activity in the hippocampal-entorhinal network, which may be important for consolidation of memories or retaining information for short periods.
Kloosterman
Fabian
F
Swammerdam Institute of Life Sciences, Section Neurobiology, University of Amsterdam, Graduate School of Neurosciences Amsterdam, Amsterdam, The Netherlands. fkloos@mit.edu
Van Haeften
Theo
T
Witter
Menno P
MP
Lopes Da Silva
Fernando H
FH
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D004594:Electrophysiology / Q000379:methods; D018728:Entorhinal Cortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time
D018691:Excitatory Amino Acid Antagonists; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione