158 research outputs found

    Rhythmic activity of both putative DA and non-DA neurons during wheel running.

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    <p>(A) Peri-event rasters and histograms of four simultaneously recorded VTA neurons in response to the conditioned tone that reliably predicted food delivery (units 1 & 2: putative DA neurons; units 3 & 4: non-DA neurons). (B) Smoothed cross-correlation histograms of the same four neurons (as shown in A) during voluntary wheel running. Unit 3 was used as the reference for cross-correlation calculations. (C) Smoothed cross-correlation histograms of shuffled units 1 and 2 (randomized spikes). The same unit 3 (as shown in B) was used as the reference for cross-correlation calculations. (D) Correlation coefficient analyses and comparisons between the recoded and shuffled spikes. A set of simulated sine oscillation curves y β€Š=β€Š sin (ax + b) were used as the reference for the correlation coefficient analysis (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016528#s4" target="_blank">Materials and Methods</a>). nβ€Š=β€Š14 and 29 for DA and non-DA neurons, respectively; *<i>P</i><0.001, Student's paired <i>t</i>-test. Error bars represent s.d.</p

    Activity of the VTA non-DA neuron correlates with the wheel running rhythm.

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    <p>(A and B) Rasters (upper panels) and smoothed auto-correlation histograms (lower panels) of two simultaneously recorded VTA non-DA neurons during high-speed (A) and low-speed (B) voluntary wheel running. (C) VTA neuron activity correlates with the limb-movement rhythm during wheel running.</p

    Classification of VTA putative DA and non-DA neurons.

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    <p>(A) Left panels, peri-event rasters and histograms of two simultaneously recorded VTA neurons (unit 1: putative DA neuron; units 2: non-DA neuron) in response to the conditioned tone (5 kHz, 1 sec) that reliably predicted food delivery. Right panels, cumulative spike activity of the same two neurons before and after (-60-0 and 0–60 min, respectively) the injection of the dopamine receptor agonist apomorphine (1 mg/kg, i.p.). (B) Percentages of classified putative DA (100%; n β€Š=β€Š 25) and non-DA neurons (13%; 6/47) that were significantly activated by the conditioned tone that reliably predicted food delivery. (C) Normalized firing rates of putative DA and non-DA neurons after the injection of apomorphine (firing rates averaged for 30 min). Note that 9 out 10 putative DA neurons tested showed significant suppression (≀ 20% baseline firing rates), while the majority of the non-DA neurons (20/22) showed limited or no change of firing rate by apomorphine (1 mg/kg, i.p.).</p

    1-hr and 24-hr cross species social recognition.

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    <p>A. In comparison to the initial encounter, neither the NR2B nor the wild-type animals show any reduction in the investigation time of the rats during the second encounter. B. In the one hour recall session with the same rat, both the NR2B and the wildtype animals show a significant reduction in the investigation times indicating that both groups of animals have formed a memory of the familiar rat. (* pβ€Š=β€Š0.033, ** pβ€Š=β€Š0.0006) C. There were no significant differences found between the investigation times of the novel rat in the first encounter with the novel rat in the second encounter. D. During the 24 recall session only the NR2B mice showed a reduction in the investigation times of the familiar rat. (* pβ€Š=β€Š0.001) This indicates that only the NR2B mice were able to form a long-term memory of the rats.</p

    Muti-tetrode recording and spike sorting.

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    <p>(A) Electrode array track shown on an example coronal brain section (top-right) and locations of the electrode array tip from 10 mice on the atlas section diagrams <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016528#pone.0016528-Paxinos1" target="_blank">[44]</a>. (B) Left panel, an example of spike sorting using principle component analysis (Plexon OfflineSorter). Here, multiple units were recorded simultaneously from one tetrode; red/purple/blue dots represent isolated units 1–3, respectively; yellow dots represent un-isolated spikes and noises; black dots represent overlapping spike waveforms, which would be manually assigned to units 1–3. Middle and right panels, representative spike waveforms for the units 1–3. Note that only unit 3 was classified as putative DA neuron, while units 1 and 2 were classified as non-DA neurons.</p

    Habituation-Dishabituation Paradigm.

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    <p>During this paradigm the animals were exposed to the stimulus mouse for one minute for four sessions separated by a 10 minute rest period. The NR2B animal showed a significant reduction in exploration times at the second encounter which continued to the fourth encounter. The wild-type animals showed a significant reduction in investigation time from the initial exposure starting at the 3 exposure. During the fifth exposure session, a novel animal was used as a control to account for fatigue and disinterest as a result of repeated exposures. (*β€Š=β€Š4.28Γ—10<sup>βˆ’5</sup>, **β€Š=β€Š1.6Γ—10<sup>βˆ’4</sup>, ***β€Š=β€Š6.3Γ—10<sup>βˆ’4</sup>; #β€Š=β€Š7.7Γ—10<sup>βˆ’5</sup>, # #β€Š=β€Š7.1Γ—10<sup>βˆ’6</sup>).</p

    1-hr and 24-hr recall with no prior isolation.

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    <p>A. Initial encounter and one hour recall using a novel mouse. Here this is no reduction in the investigation time during the second encounter. B. Both the NR2B and the wild-type animals demonstrate a significant reduction in investigation times of the familiar juvenile indicating a memory of that animal. (* pβ€Š=β€Š0.037, ** pβ€Š=β€Š0.005) C. There were no significant differences seen between the investigation times in the initial encounter and the second encounter 24 hours later when a novel animal was used at the second encounter. D. Both groups of animals spent significantly less time investigating the familiar animal at the 24 hour recall session. (* pβ€Š=β€Š0.045, ** pβ€Š=β€Š0.02).</p

    Interstrain social recognition at 1-hr and 24-hr using a white mouse.

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    <p>A. No significant differences were found during the second exposure using a novel mouse after one hour. B. After one hour, both the NR2B and the wild-type animals showed a significant reduction in investigation times of the same white mouse that presented in the first encounter. (* pβ€Š=β€Š0.044, ** pβ€Š=β€Š0.005) C. During the 24 recall the NR2B animals and the wild-type animals show no reduction in investigation time when a novel mouse is presented in the second encounter. D. After 24 hours only the NR2B animals show a significant reduction in investigation times of the familiar white mouse indicating that the wild-type animal was unable to form a long-term social recognition memory of the white mouse . (* pβ€Š=β€Š0.048).</p

    1-hr and 24-hr recall after 24-hr social isolation.

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    <p>A. No reduction in investigation times was seen in the second encounter with a novel animal after one hour. B. Initial encounter and one hour recall using familiar mouse. Here a significant reduction in the investigation times is seen in both the NR2B and the wildtype animals (* pβ€Š=β€Š0.018, ** pβ€Š=β€Š0.029) C. There was no reduction in investigation time at the 24 hour recall encounter using a novel mouse. D. A significant reduction was seen in the investigation times of the familiar mouse in both groups after 24 hours. (* pβ€Š=β€Š0.0136, ** pβ€Š=β€Š0.001).</p

    Phase-specific firing of VTA non-DA neurons during wheel running.

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    <p>(A) Rasters of five simultaneously recorded VTA non-DA neurons during voluntary wheel running. (B) Cross-correlation histograms show that the same five neurons (as shown in A) fire preferentially at specific phases of each cycle and in sequence during voluntary wheel running (unit 4 was used as the reference for cross-correlation calculation).</p
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