Traveling waves are hypothesized to support the long-range coordination of anatomically distributed circuits. Whether separate strongly-interacting circuits exhibit traveling waves remains unknown. The hippocampus exhibits traveling 'theta' waves and interacts strongly with the medial entorhinal cortex (MEC). To determine whether the MEC also activates in a traveling wave, we performed extracellular recordings of LFP and multi-unit activity along the MEC. These recordings revealed progressive phase shifts in activity, indicating that the MEC also activates in a traveling wave. Variation in theta waveform along the region, generated by gradients in local physiology, contributed to the observed phase shifts. Removing waveform-related phase shifts left significant residual phase shifts. The residual phase shifts covaried with theta frequency in a manner consistent with those generated by weakly coupled oscillators. These results show that coordination of anatomically distributed circuits could be enabled by traveling waves but reveal heterogeneity in the mechanisms generating those waves.
- Ehren L Newman
- Jesus J Hernández-Pérez
- Ehren L Newman
The funders provided resources for the study design, data collection, and interpretation.
Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols (#18-026) of Indiana University, Bloomington. The protocol was approved by the Committee on the Ethics of Animal Experiments of Indiana University, Bloomington (Animal Welfare Assurance Number D16-00587). All surgery was performed under isoflurane anesthesia, and every effort was made to minimize suffering.
- Neil Burgess, University College London, United Kingdom
© 2020, Hernández-Pérez et al.
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