Hippocampal sharp-wave ripple architecture after high-frequency closed head impact exposure in male mice

STUDY PURPOSE: Repeated head impact in sports can lead to chronic cognitive and neurobehavior deficits even in the absence of brain pathology. The high-frequency head impact (HFHI) model is a closed head injury model designed to mimic head impacts in sports. Mice receive 30 head impacts over 6 consecutive days (5 head impacts per day), which results in impaired cognitive function. We have previously shown that this loss of cognition occurs through chronic changes to synaptic properties in core hippocampal circuits - which occurs without causing hippocampal cell death, axonal damage, inflammation, or tau or amyloid accumulation.

Sharp wave ripples (SWR) are hippocampal population events that are strongly associated with memory and are an established biomarker for cognition and memory. It is unknown how HFHI affects intrinsic plasticity events, including hippocampal SWR. To characterize the effect of HFHI on SWR, we exposed male C57/Bl6J mice to sham or HFHI procedures (n = 11 for each group) and prepared acute hippocampal slices 24 hours after the final head impact. We used field recordings to characterize hippocampal SWR. The dataset contains measures of SWR architecture. DATA COLLECTED: The dataset consists of sharp-wave and ripple events that were automatically detected from 2-minute-long acute hippocampal slice recordings at 24h after the final head impact. There were n = 11 mice from each group (sham and HFHI). The data was recorded using open-source MATLAB software which enables quantification of metrics including, but not limited to, rates, amplitudes, and durations of events in raw or filtered field potentials. This software detects SWR events by flagging all instances of lasting at least 10 milliseconds that are concurrently elevated greater than four standard deviations above baseline in both the sharp wave (1-30 Hz) and ripple (120-220 Hz) frequencies. If SWR events are detected, those events are analyzed for metrics including duration (start and end times), power (area under the curve at the analyzed frequency), amplitude (baseline subtracted from sharp wave peak), and number of cycles (filtered only, eg ripple cycles) from start to end of SWR event. When SWR were detected in multiple slices from the same animal, we averaged the data to generate a single datapoint per animal.

Exclusion criteria: If SWR were not detectable from a brain, that brain was removed from the study. WE detected SWR in n = 8 brains from each group. Prior to analysis, outlier testing was performed using the ROUT test, with a threshold of Q > 1%. One animal from the HFHI group was statistically identified as an outlier in over half of the metrics reported and thus was removed from the entire study. The final n after exclusion criteria was sham = 8, HFHI = 7. DATA USAGE NOTES: