Rat 50 kHz Trill Calls Are Tied to the Expectation of Social Interaction.

Rats emit a variety of calls in the 40-80 kHz range (50 kHz calls). While these calls are generally associated with positive affect, it is unclear whether certain calls might be used selectively in certain contexts. To examine this, we looked at ultrasonic calls in 30-40 day old male rats during the expectation of either play or food, both of which are reinforcing.

Reliable induction of sleep spindles with intracranial electrical pulse stimulation.

Neocortical sleep spindles have been shown to occur more frequently following a memory task, suggesting that a method to increase spindle activity could improve memory processing. Stimulation of the neocortex can elicit a slow oscillation (SO) and a spindle, but the feasibility of this method to boost SO and spindles over time has not been tested. In rats with implanted neocortical electrodes, stimulation during slow wave sleep significantly increased SO and spindle rates compared to control rest periods before and after the stimulation session.

A naturalistic method to test depression: Anticipation of play.

The Wistar-Kyoto (WKY) rat was developed as a control for the spontaneous hypertensive rat but has subsequently also been used as a genetic animal model of depression due to its hyper-responsiveness to stress. We used anticipation of social reward (i.e.

Amphetamine reduces reward encoding and stabilizes neural dynamics in rat anterior cingulate cortex.

Psychostimulants such as d-amphetamine (AMPH) often have behavioral effects that appear paradoxical within the framework of optimal choice theory. AMPH typically increases task engagement and the effort animals exert for reward, despite decreasing reward valuation. We investigated neural correlates of this phenomenon in the anterior cingulate cortex (ACC), a brain structure implicated in signaling cost-benefit utility.

Memory reactivation in rat medial prefrontal cortex occurs in a subtype of cortical UP state during slow-wave sleep.

Interaction between hippocampal sharp-wave ripples (SWRs) and UP states, possibly by coordinated reactivation of memory traces, is conjectured to play an important role in memory consolidation. Recently, it was reported that SWRs were differentiated into multiple subtypes. However, whether cortical UP states can also be classified into subtypes is not known.

Unsupervised Detection of Cell-Assembly Sequences by Similarity-Based Clustering.

Neurons which fire in a fixed temporal pattern (i.e., "cell assemblies") are hypothesized to be a fundamental unit of neural information processing.

Can Slot-Machine Reward Schedules Induce Gambling Addiction in Rats?

Similar to drugs of abuse, random-ratio reward schedules are highly motivating and, in humans, are thought to foster gambling addiction. Animal gambling models, however, have not yet demonstrated the compulsivity so characteristic of drug addiction. Three criteria have been used to evaluate addiction-like behavior in drug models: (1) response inhibition when reward is not available, (2) persistence under a progressive ratio schedule, in which the response-to-reward ratio is stretched, and (3) persistence in spite of punishment.

Rat anterior cingulate cortex recalls features of remote reward locations after disfavoured reinforcements.

The anterior cingulate cortex (ACC) encodes information supporting mnemonic and cognitive processes. We show here that a rat's position can be decoded with high spatiotemporal resolution from ACC activity. ACC neurons encoded the current state of the animal and task, except for brief excursions that sometimes occurred at target feeders.

Avoiding escalation from play to aggression in adult male rats: The role of ultrasonic calls.

Play fighting is most commonly associated with juvenile animals, but in some species, including rats, it can continue into adulthood. Post-pubertal engagement in play fighting is often rougher and has an increased chance of escalation to aggression, making the use of play signals to regulate the encounter more critical. During play, both juvenile and adult rats emit many 50-kHz calls and some of these may function as play facilitating signals.

Specific 50-kHz vocalizations are tightly linked to particular types of behavior in juvenile rats anticipating play.

Rat ultrasonic vocalizations have been suggested to be either a byproduct of physical movement or, in the case of 50-kHz calls, a means to communicate positive affect. Yet there are up to 14 distinct types of 50-kHz calls, raising issues for both explanations. To discriminate between these theories and address the purpose for the numerous 50-kHz call types, we studied single juvenile rats that were waiting to play with a partner, a situation associated with a high number of 50-kHz calls.

Are 50-khz calls used as play signals in the playful interactions of rats? III. The effects of devocalization on play with unfamiliar partners as juveniles and as adults.

When playing, rats emit 50-kHz calls which may function as play signals. A previous study using devocalized rats provides support for the hypothesis that 50-kHz function to promote and maintain playful interactions (Kisko et al., 2015).

Are 50-kHz calls used as play signals in the playful interactions of rats? II. Evidence from the effects of devocalization.

During playful interactions, juvenile rats emit many 50-kHz ultrasonic vocalizations, which are associated with a positive affective state. In addition, these calls may also serve a communicative role - as play signals that promote playful contact. Consistent with this hypothesis, a previous study found that vocalizations are more frequent prior to playful contact than after contact is terminated.

Lesions of dorsal striatum eliminate lose-switch responding but not mixed-response strategies in rats.

We used focal brain lesions in rats to examine how dorsomedial (DMS) and dorsolateral (DLS) regions of the striatum differently contribute to response adaptation driven by the delivery or omission of rewards. Rats performed a binary choice task under two modes: one in which responses were rewarded on half of the trials regardless of choice; and another 'competitive' one in which only unpredictable choices were rewarded. In both modes, control animals were more likely to use a predictable lose-switch strategy than animals with lesions of either DMS or DLS.

Not all effort is equal: the role of the anterior cingulate cortex in different forms of effort-reward decisions.

The rat anterior cingulate cortex (ACC) mediates effort-based decision making when the task requires the physical effort of climbing a ramp. Normal rats will readily climb a barrier leading to high reward whereas rats with ACC lesions will opt instead for an easily obtained small reward. The present study explored whether the role of ACC in cost-benefit decisions extends beyond climbing by testing its role in ramp climbing as well as two novel cost-benefit decision tasks, one involving the physical effort of lifting weights and the other the emotional cost of overcoming fear (i.

The role of medial prefrontal cortex in memory and decision making.

Some have claimed that the medial prefrontal cortex (mPFC) mediates decision making. Others suggest mPFC is selectively involved in the retrieval of remote long-term memory. Yet others suggests mPFC supports memory and consolidation on time scales ranging from seconds to days.

Stored-trace reactivation in rat prefrontal cortex is correlated with down-to-up state fluctuation density.

Spontaneous reactivation of previously stored patterns of neural activity occurs in hippocampus and neocortex during non-rapid eye movement (NREM) sleep. Notable features of the neocortical local field potential during NREM sleep are high-amplitude, low-frequency thalamocortical oscillations including K-complexes, low-voltage spindles, and high-voltage spindles. Using combined neuronal ensemble and local field potential recordings, we show that prefrontal stored-trace reactivation is correlated with the density of down-to-up state transitions of the population of simultaneously recorded cells, as well as K-complexes and low-voltage spindles in the local field potential.

Fast-forward playback of recent memory sequences in prefrontal cortex during sleep.

As previously shown in the hippocampus and other brain areas, patterns of firing-rate correlations between neurons in the rat medial prefrontal cortex during a repetitive sequence task were preserved during subsequent sleep, suggesting that waking patterns are reactivated. We found that, during sleep, reactivation of spatiotemporal patterns was coherent across the network and compressed in time by a factor of 6 to 7. Thus, when behavioral constraints are removed, the brain's intrinsic processing speed may be much faster than it is in real time.

Apparent encoding of sequential context in rat medial prefrontal cortex is accounted for by behavioral variability.

Simple sequences can be represented via asymmetrically linked neural assemblies, provided that the elements of the sequence are unique. When elements repeat, however (e.g.

Sequential-context-dependent hippocampal activity is not necessary to learn sequences with repeated elements.

Learning sequences of events (e.g., a-b-c) is conceptually a simple problem that can be solved using asymmetrically linked cell assemblies [e.

From spectrum to space: the contribution of level difference cues to spatial receptive fields in the barn owl inferior colliculus.

Space-specific neurons in the owl's inferior colliculus have spatial receptive fields (RFs) computed from interaural time (ITD) and level (ILD) differences. Because of the shape of the owl's head, these cues vary with frequency in a manner specific for each location. We sought to determine the contribution of ILD to spatial selectivity.