Amygdala inputs to prefrontal cortex guide behavior amid conflicting cues of reward and punishment

Orchestrating appropriate behavioral responses in the face of competing signals that predict either rewards or threats in the environment is crucial for survival. The basolateral nucleus of the amygdala (BLA) and prelimbic (PL) medial prefrontal cortex have been implicated in reward-seeking and fear-related responses, but how information flows between these reciprocally connected structures to coordinate behavior is unknown. We recorded neuronal activity from the BLA and PL while rats performed a task wherein competing shock- and sucrose-predictive cues were simultaneously presented. The correlated firing primarily displayed a BLA→PL directionality during the shock-associated cue. Furthermore, BLA neurons optogenetically identified as projecting to PL more accurately predicted behavioral responses during competition than unidentified BLA neurons. Finally photostimulation of the BLA→PL projection increased freezing, whereas both chemogenetic and optogenetic inhibition reduced freezing. Therefore, the BLA→PL circuit is critical in governing the selection of behavioral responses in the face of competing signals.National Institutes of Health (U.S.) (Award 1R25-MH092912-01)National Institute of Mental Health (U.S.) (Grant R01- MH102441-01)National Institutes of Health (U.S.) (Award DP2- DK-102256-01

Gestational Valproate Alters BOLD Activation in Response to Complex Social and Primary Sensory Stimuli

Valproic acid (VPA) has been used clinically as an anticonvulsant medication during pregnancy; however, it poses a neurodevelopmental risk due to its high teratogenicity. We hypothesized that midgestational (GD) exposure to VPA will lead to lasting deficits in social behavior and the processing of social stimuli. To test this, animals were given a single IP injection of 600 mg/kg of VPA on GD 12.5. Starting on postnatal day 2 (PND2), animals were examined for physical and behavior abnormalities. Functional MRI studies were carried out after PND60. VPA and control animals were given vehicle or a central infusion of a V1a antagonist 90 minutes before imaging. During imaging sessions, rats were presented with a juvenile test male followed by a primary visual stimulus (2 Hz pulsed light) to examine the effects of prenatal VPA on neural processing. VPA rats showed greater increases in BOLD signal response to the social stimulus compared to controls in the temporal cortex, thalamus, midbrain and the hypothalamus. Blocking the V1a receptor reduced the BOLD response in VPA animals only. Neural responses to the visual stimulus, however, were lower in VPA animals. Blockade with the V1a antagonist did not revert this latter effect. Our data suggest that prenatal VPA affects the processing of social stimuli and perhaps social memory, partly through a mechanism that may involve vasopressin V1a neurotransmission

Nature

The ability to associate temporally segregated information and assign positive or negative valence to environmental cues is paramount for survival. Studies have shown that different basolateral amygdala (BLA) projections are potentiated following reward or punishment learning1–7. However, we do not yet understand how valence specific information is routed to the BLA neurons with the appropriate downstream projections. Nor do we understand how to reconcile the subsecond timescales of synaptic plasticity8–11 with the longer timescales separating the predictive cues from their outcomes. Here, we demonstrate that neurotensin (NT) neurons in the paraventricular nucleus of the thalamus (PVT) projecting to the BLA (PVT-BLA:NT) mediate valence assignment by exerting concentration-dependent modulation in BLA during associative learning. We found that optogenetic activation of the PVT-BLA:NT projection promotes reward learning, while PVT-BLA projection-specific Nt gene knockout augments punishment learning. Using genetically encoded calcium and NT sensors, we further revealed that both calcium dynamics within the PVT-BLA:NT projection and NT concentrations in the BLA are enhanced after reward learning and reduced after punishment learning. Finally, we showed that CRISPR-mediated knockout of the Nt gene in the PVT-BLA pathway blunts BLA neural dynamics and attenuates the preference to active behavioral strategies to reward and punishment predictive cues. Taken together, we have identified NT as a neuropeptide that signals valence in the BLA, and showed that NT is a critical neuromodulator that orchestrates positive and negative valence assignment in amygdala neurons by extending valence-specific plasticity to behaviorally-relevant timescales

Social interactions and other behaviors in rats pre-exposed to saline (Sal) and valproic acid (VPA) during gestation.

<p>Measurements were taken immediately before setup for fMRI studies and 60 minutes after an intracerebroventricular (ICV) injection. Experiments tested whether VPA altered social behavior and neural processing, and if this involves an altered role for the V_1a receptor. Thus, Sal and VPA rats were subdivided into animals that were given an ICV injection of Sal or a vasopressin V_1a receptor antagonist. The groups are: Sal-CSF (open bar), VPA-CSF (close bar), Sal-V_1a (diagonal patterned), and VPA- V_1a (upward patterned). Data shown as mean ± standard error. VPA rats showed lower social interaction (left) and trended towards higher locomotor activity (p = 0.07). *Significantly different from Sal-Sal (p<0.05; two way ANOVA).</p

Novel object recognition in rats pre-exposed to saline and valproic acid (VPA) during gestation.

<p>Left bar graph shows total time spent exploring both objects inside a test arena. Middle bar graph shows the time saline treated rats spent exploring a novel versus a familiar object. Right bar graph shows data for VPA pre-exposed rats. While saline animals spent less time exploring a familiar object (<i>middle</i>), VPA animals spent equal amounts of time exploring each object (<i>right</i>). This was not associated with overall levels of object exploration (<i>left</i>). Data shown as mean ± standard error. Asterisks indicate significant differences p<0.05 (two tailed t-test).</p

Number of voxels in visual pathway regions of rats pre-exposed to saline and VPA during gestation.

<p>The study design is as explained in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037313#pone-0037313-g004" target="_blank">Figures 4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037313#pone-0037313-g005" target="_blank">5</a>. Sal and VPA rats were subdivided into animals that were given an ICV injection of Sal or a vasopressin V_1a receptor antagonist. The groups are: Sal-CSF (open bar), VPA-CSF (close bar), Sal-V_1a (diagonal patterned), and VPA-V_1a (upward patterned). VPA treatment did not have the same effect on the visual stimulus as with the social stimulus (VPA-CSF versus Sal-CSF). V1a receptor blockade reduced voxels in superior colliculus, an area containing a moderate density of V_1a receptor mRNA <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037313#pone.0037313-Ostrowski1" target="_blank">[19]</a>, in both Sal and VPA rats. Data shown as mean ± standard error. Data shown as mean ± standard error. Asterisks indicate specific posthoc comparisons with * p<0.05 and **p<0.01 (two way ANOVA).</p

Visual system BOLD activation in response to 2 Hz flashing LED in rats pre-exposed to saline and VPA during gestation.

<p>The study design is as explained in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037313#pone-0037313-g004" target="_blank">Figures 4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037313#pone-0037313-g005" target="_blank">5</a>. Sal and VPA rats were subdivided into animals that were given an ICV injection of Sal or a vasopressin V1a receptor antagonist. Left column shows BOLD signal time courses for the visual cortex, superior colliculus and lateral genticulate nucleus. The groups are: Sal-CSF (white circles), VPA-CSF (blue squares), Sal-V_1a (green triangles), and VPA-V_1a (red inverted triangles). Data shown as mean ± standard error. BOLD signal changes in Sal-CSF rats (white circles) were greater in the visual cortex than VPA-CSF rats (p<0.05, repeated measures ANOVA). Shown on the right are 2D maps at the level of the visual cortex. Scale bar hue (red-yellow) indicates the percentage change (from 1–15%) for areas of increased activity.</p

Number of ultrasonic vocalizations (USV) emitted by saline (SAL) and valproic acid (VPA) pre-exposed pups.

<p>Data were collected on postnatal days 5 and 11 (D5 and D11). USV's were categorized and analyzed separately according to specific USV characteristics. Bar graphs all have representative sonograms overlying the category title. All data presented as mean ± standard error. *Significantly different from SAL D5; **significantly different from VPA D5 (Kruskall-Wallis Analysis of Variance, p<0.05). VPA D11 showed a nonsignificant trend when compared to VPA D5 (p = 0.05).</p

Social stimulus-induced changes in BOLD in rats pre-exposed to saline (Sal) and VPA during gestation.

<p>The study design is as explained in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037313#pone-0037313-g004" target="_blank">Figures 4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037313#pone-0037313-g005" target="_blank">5</a>. An <i>in vivo</i> social stimulus juvenile was presented during scanning between repetitions 51–100, with repetitions 1–50 corresponding to baseline acquisitions (see text for details). Shown are 2D atlas maps for two treatment conditions (Sal and VPA). Close ups highlight several ROI's of saline control and VPA treated animal's. Scale bar hue (red-yellow) shown at the bottom indicates the percentage change (from 1–15%) for areas of increased activity. Note predominant yellow hue (indicative of higher activity) pixels in VPA-CSF compared to saline (Sal-CSF).</p

Social stimulus-induced changes in BOLD in rats pre-exposed to saline (Sal) and VPA during gestation.

<p>The study design is as explained in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037313#pone-0037313-g004" target="_blank">Figures 4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037313#pone-0037313-g005" target="_blank">5</a>. Sal and VPA rats were subdivided into animals that were given an ICV injection of Sal or a vasopressin V_1a receptor antagonist. The groups are: Sal-CSF (open bar), VPA-CSF (close bar), Sal-V_1a (diagonal patterned), and VPA-V_1a (upward patterned). The percent changes correspond to the averaged timecourse for the stimulus epoch. Graphs show percent change in BOLD across groups for various ROI's. Data shown as mean ± standard error. Asterisks and lines indicate specific posthoc comparisons with * p<0.05 and **p<0.01 (two way ANOVA).</p