Human retrosplenial cortex displays transient theta phase locking with medial temporal cortex prior to activation during autobiographical memory retrieval.

The involvement of retrosplenial cortex (RSC) in human autobiographical memory retrieval has been confirmed by functional brain imaging studies, and is supported by anatomical evidence of strong connectivity between the RSC and memory structures within the medial temporal lobe (MTL). However, electrophysiological investigations of the RSC and its interaction with the MTL have mostly remained limited to the rodent brain. Recently, we reported a selective increase of high-frequency broadband (HFB; 70-180 Hz) power within the human RSC during autobiographical retrieval, and a predominance of 3-5 Hz theta band oscillations within the RSC during the resting state. In the current study, we aimed to explore the temporal dynamics of theta band interaction between human RSC and MTL during autobiographical retrieval. Toward this aim, we obtained simultaneous recordings from the RSC and MTL in human subjects undergoing invasive electrophysiological monitoring, and quantified the strength of RSC-MTL theta band phase locking. We observed significant phase locking in the 3-4 Hz theta range between the RSC and the MTL during autobiographical retrieval. This theta band phase coupling was transient and peaked at a consistent latency before the peak of RSC HFB power across subjects. Control analyses confirmed that theta phase coupling between the RSC and MTL was not seen for other conditions studied, other sites of recording, or other frequency ranges of interest (1-20 Hz). Our findings provide the first evidence of theta band interaction between the human RSC and MTL during conditions of autobiographical retrieval.

Aberrant lymphatic drainage and risk for melanoma recurrence after negative sentinel node biopsy in middle-aged and older men.

BACKGROUND: Aberrant lymphatic drainage is believed to contribute to the high recurrence rate of head and neck melanomas. The purpose of this study was to identify the clinical significance of unexpected lymphatic drainage patterns. METHODS: A single institution retrospective analysis was performed of middle-aged and older men (mean age, 66.2 years; range, 41-87 years) who underwent successful lymphoscintigraphy with sentinel lymph node biopsy (SLNB) from 1997 through 2012. Node status, distribution, and recurrence were assessed comparing patients with expected and unexpected drainage patterns. RESULTS: Sixty-six patients were identified with 55.8 months median follow-up (range, 5.6-206.1 months). Unexpected sentinel lymph node drainage was associated with multiple basin drainage (p < .01) and greater recurrence after negative SLNB (p = .03). Both groups had similar anatomic distribution, sentinel lymph node sampling, histopathologic characteristics, follow-up, and survival. CONCLUSION: Lymphatic drainage differing from expected patterns is associated with greater recurrence after negative SLNB in middle-aged and older men. © 2015 Wiley Periodicals, Inc. Head Neck 38: E754-E760, 2016.