32 research outputs found

    Learning-related modulation in LFP activities.

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    <p><b>A,</b> Perievent raster plots of representative LFP recording. Both examples display depolarization following reward delivery. B, Perivent histograms of representative LFP recorded from 3 rats during the first training session and the last session (top, MD; bottom, mPFC). LFPs exhibit depolarization (negativity in the extracellular recording) with learning.</p

    Changes in coherence between MD and mPFC during learning.

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    <p>A, Left, Overall coherence from two representative electrodes during the first (green) and last (red) session in MD and mPFC. Right, dynamic changes of theta and gamma coherence during 4 sessions of instrumental learning (n = 33 pairs in each session). Error bars represent SEM. B, Left, coherence upon reward delivery measured from activity from two representative electrodes. Right, dynamic modulation of theta and gamma coherence by the reward delivery. Error bars indicate SEM.</p

    Theta and gamma frequency oscillations.

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    <p>(A and C) Perievent spectrograms of representative MD (<i>A</i>) and mPFC <i>(C)</i> LFP during the first (top) and last (bottom) session. MD Theta power is much stronger compare to mPFC. mPFC gamma power is much stronger compared to MD. After learning, gamma power is maximal at the time of reward delivery. (B and D) Changes of normalized power spectra of theta and gamma frequency oscillations in MD (n = 22) <i>(B)</i> and mPFC (n = 14) <i>(D</i>) upon the reward deliver across four sessions. Error bars indicate SEM.</p

    Neuronal activity in MD and mPFC during acquisition.

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    <p>A, Left, action potential waveform and distribution of interspike intervals of representative neurons recorded from MD and mPFC. Right, Perievent raster plots of representative neurons. Each row in raster plot represents a single trial. Green line represents time of reward delivery. Reward excited neuron increases firing after the completion of lever press action and delivery of reward. Reward inhibited neuron decreases firing upon the delivery of reward. B, Top, spike density functions of individual neurons that transiently increased (MD n = 42; mPFC n = 28) or decreased (MD n = 32; mPFC n = 17) activity following reward delivery. Each row shows a z-score normalized spike density function for a single neuron. The neurons are sorted by the latency to the maximum or minimum amplitude. Bottom, normalized population firing rate of reward excited and inhibited neurons at the time of reward delivery. Shaded areas indicate SEM.</p

    LFP recording in MD and mPFC during behavior.

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    <p>Representative LFP traces recorded from the four electrodes during the final session. LFPs in the MD exhibit prominent theta band (∼7–8 Hz) oscillations, whereas LFPs in the mPFC show prominent gamma band (∼50 Hz) oscillations.</p

    With free access to food and water, mice were indifferent to risk.

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    <p>A. Experienced risk measured by reward variance. The actual experienced risk is calculated by counting the safe reward size (0.01 ml) as 1. When the trial is unrewarded, the outcome is 0, when the outcome is 0.02 ml or twice the safe reward size, the outcome is counted as 2. Error bars indicate standard error of the means (SEM). Sucrose = 10% sucrose; alcohol = 10% sucrose and 20% ethanol. B. Risk preference under different levels of risk (average of last 3 sessions; probability of reward on the risky lever = 12.5%). Mice were trained successively on 4 levels of risk (100%, 0.01 ml; 50%, 0.02 ml; 25%, 0.04 ml; 12.5%, 0.08 ml). Risk aversion index was calculated by dividing number of safe choices by the total number of presses. If the index is greater than 0.5, the animal is risk averse; if it is less than 0.5, the animal is risk prone. C. Number of presses on the two levers (average of last 3 sessions; probability of reward on the risky lever = 12.5%). D. Rate of lever pressing during the last session.</p

    Electrode placement and behavioral results.

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    <p>A, Coronal sections of the rat brain illustrating MD and mPFC electrode placements. The coordinates are based on a standard rat brain atlas <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050578#pone.0050578-Paxinos1" target="_blank">[58]</a>. The numbers indicate distance in mm from Bregma. MDC, mediodorsal thalamic nucleus, central part; MDM, mediodorsal thalamic nucleus, medial part; Cg1, cingulate cortex, area1; PrL; prelimbic cortex. B, Outcome devaluation test. Devalued, rats received 1 h of unlimited food pellets, same as earned by lever pressing. Non-devalued, rats did not receive any food for 1 h before test. Normalized rate of presses were the ratio of presses under each condition. Error bars indicate SEM.</p

    Dynamic changes in oscillatory activity during learning.

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    <p>A, Power spectral analysis of theta and gamma oscillations in the MD. Theta band oscillations increased during training, but gamma oscillations did not. First, first session; Last, last (4th) training session. Representative data are shown from one rat with simultaneous MD and mPFC recordings. B, Normalized (% of the first session) power of theta and gamma oscillations in the MD (n = 22) during acquisition. Theta oscillations in the MD increased significantly over time, whereas gamma oscillations did not. Data from all animals are averaged and shown here. Error bars present SEM. C, Power spectral analysis of theta and gamma oscillations in the mPFC. Representative data are shown from one rat with simultaneous MD and mPFC recordings. D, Normalized (% of the first session) power of theta and gamma oscillations in the mPFC (n = 14) during acquisition. There was a significant increase in the gamma oscillation but not in theta oscillations.</p

    Reward reversal.

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    <p>To demonstrate that the effects we observed were due to the identity of the reward outcome, we also reversed the identity of the reward (sucrose to alcohol and alcohol to sucrose). A. Experienced reward variance on the risky lever average of last 3 sessions at 12.5%). B. Risk preference (average of last 3 sessions at 12.5%). The sucrose group displayed higher risk aversion, whereas the alcohol group was risk neutral. C. Total presses on the two levers (average of last 3 sessions at 12.5%). D. Rate of lever pressing in a session (average of last 3 sessions at 12.5%).</p

    Reducing alcohol concentration reduces risk aversion.

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    <p>A. Experienced reward variance. Error bars indicate standard error of the means (SEM). Sucrose = 10% sucrose; alcohol = 10% sucrose and 20% ethanol. B. Risk preference of mice when the concentration of alcohol was manipulated. Alcohol dose-dependently reduced risk aversion. C. Number of presses. The addition of alcohol to the sucrose reward dose-dependently reduced the number of safe choices. D. Increasing alcohol concentration increased choice latency. E. Rate of lever pressing during the last session.</p
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