Abnormal Locus Coeruleus Sleep Activity Alters Sleep Signatures of Memory Consolidation and Impairs Place Cell Stability and Spatial Memory.

Sleep is critical for proper memory consolidation. The locus coeruleus (LC) releases norepinephrine throughout the brain except when the LC falls silent throughout rapid eye movement (REM) sleep and prior to each non-REM (NREM) sleep spindle. We hypothesize that these transient LC silences allow the synaptic plasticity that is necessary to incorporate new information into pre-existing memory circuits. We found that spontaneous LC activity within sleep spindles triggers a decrease in spindle power. By optogenetically stimulating norepinephrine-containing LC neurons at 2 Hz during sleep, we reduced sleep spindle occurrence, as well as NREM delta power and REM theta power, without causing arousals or changing sleep amounts. Stimulating the LC during sleep following a hippocampus-dependent food location learning task interfered with consolidation of newly learned locations and reconsolidation of previous locations, disrupting next-day place cell activity. The LC stimulation-induced reduction in NREM sleep spindles, delta, and REM theta and reduced ripple-spindle coupling all correlated with decreased hippocampus-dependent performance on the task. Thus, periods of LC silence during sleep following learning are essential for normal spindle generation, delta and theta power, and consolidation of spatial memories.

Different Simultaneous Sleep States in the Hippocampus and Neocortex.

STUDY OBJECTIVES: Investigators assign sleep-waking states using brain activity collected from a single site, with the assumption that states occur at the same time throughout the brain. We sought to determine if sleep-waking states differ between two separate structures: the hippocampus and neocortex. METHODS: We measured electrical signals (electroencephalograms and electromyograms) during sleep from the hippocampus and neocortex of five freely behaving adult male rats. We assigned sleep-waking states in 10-sec epochs based on standard scoring criteria across a 4-h recording, then analyzed and compared states and signals from simultaneous epochs between sites. RESULTS: We found that the total amount of each state, assigned independently using the hippocampal and neocortical signals, was similar between the hippocampus and neocortex. However, states at simultaneous epochs were different as often as they were the same (P = 0.82). Furthermore, we found that the progression of states often flowed through asynchronous state-pairs led by the hippocampus. For example, the hippocampus progressed from transition-to-rapid eye movement sleep to rapid eye movement sleep before the neocortex more often than in synchrony with the neocortex (38.7 ± 16.2% versus 15.8 ± 5.6% mean ± standard error of the mean). CONCLUSIONS: We demonstrate that hippocampal and neocortical sleep-waking states often differ in the same epoch. Consequently, electrode location affects estimates of sleep architecture, state transition timing, and perhaps even percentage of time in sleep states. Therefore, under normal conditions, models assuming brain state homogeneity should not be applied to the sleeping or waking brain.

Stress-free automatic sleep deprivation using air puffs.

BACKGROUND: Sleep deprivation via gentle handling is time-consuming and personnel-intensive. NEW METHOD: We present here an automated sleep deprivation system via air puffs. Implanted EMG and EEG electrodes were used to assess sleep/waking states in six male Sprague-Dawley rats. Blood samples were collected from an implanted intravenous catheter every 4h during the 12-h light cycle on baseline, 8h of sleep deprivation via air puffs, and 8h of sleep deprivation by gentle handling days. RESULTS: The automated system was capable of scoring sleep and waking states as accurately as our offline version (∼90% for sleep) and with sufficient speed to trigger a feedback response within an acceptable amount of time (1.76s). Manual state scoring confirmed normal sleep on the baseline day and sleep deprivation on the two manipulation days (68% decrease in non-REM, 63% decrease in REM, and 74% increase in waking). No significant differences in levels of ACTH and corticosterone (stress hormones indicative of HPA axis activity) were found at any time point between baseline sleep and sleep deprivation via air puffs. COMPARISON WITH EXISTING METHOD: There were no significant differences in ACTH or corticosterone concentrations between sleep deprivation by air puffs and gentle handling over the 8-h period. CONCLUSIONS: Our system accurately detects sleep and delivers air puffs to acutely deprive rats of sleep with sufficient temporal resolution during the critical 4-5h post learning sleep-dependent memory consolidation period. The system is stress-free and a viable alternative to existing sleep deprivation techniques.

Open-source logic-based automated sleep scoring software using electrophysiological recordings in rats.

Manual state scoring of physiological recordings in sleep studies is time-consuming, resulting in a data backlog, research delays and increased personnel costs. We developed MATLAB-based software to automate scoring of sleep/waking states in rats, potentially extendable to other animals, from a variety of recording systems. The software contains two programs, Sleep Scorer and Auto-Scorer, for manual and automated scoring. Auto-Scorer is a logic-based program that displays power spectral densities of an electromyographic (EMG) signal and sigma, delta, and theta frequency bands of an electroencephalographic (EEG) signal, along with the delta/theta ratio and sigmaxtheta, for every epoch. The user defines thresholds from the training file state definitions which the Auto-Scorer uses with logic to discriminate the state of every epoch in the file. Auto-Scorer was evaluated by comparing its output to manually scored files from 6 rats under 2 experimental conditions by 3 users. Each user generated a training file, set thresholds, and auto-scored the 12 files into 4 states (waking, non-REM, transition-to-REM, and REM sleep) in 1/4 the time required to manually score the file. Overall performance comparisons between Auto-Scorer and manual scoring resulted in a mean agreement of 80.24+/-7.87%, comparable to the average agreement among 3 manual scorers (83.03+/-4.00%). There was no significant difference between user-user and user-Auto-Scorer agreement ratios. These results support the use of our open-source Auto-Scorer, coupled with user review, to rapidly and accurately score sleep/waking states from rat recordings.

Electroporation-induced cell lysis in SWLA-2 hybridomas.

This paper describes experimental results involving the percentage cell lysis in SWLA-2 murine hybridomas produced by square wave electric field pulses of 100, 200, and 300 V across a 1 mm gap width in a standard cuvette. Pulse lengths were of 0.2 and 0.6 ms duration; 1, 2, or 3 pulses were applied with 100 ms time interval between pulses. Cells were cultured and separate samples examined at 48 hours to determine cell mortality. Nearly 90% cell mortality was produced by applying 3 pulses at of 0.6 ms duration at 300 V.

BioMEMs.

This session is intended to provide insight into the development of BioMEMS in the academic and industrial settings and address the current challenges facing R&D. Each speaker will address the field of bioMEMS and collaborations between academia and industry from his point-of-view and provide examples of developmental successes and failures in his setting. The speakers will also submit potential solutions to the organizational problems they presently face and foresee in the future. As a panel, the speakers will exchange ideas with the attendees with the hope of collectively introducing solutions to the problems submitted during the talks and general guidelines for successful R&D of BioMEMS through productive collaboration among engineers and scientists of different disciplines and between academia and industry. Speakers: Professor Kensall D. Wise (Professor of EECS and Director of WIMS, U of Michigan), Dr. Michael A. Huff (Director of the MEMS Exchange), Colin Brenan (CTO, Biotrove).