Understanding the neural dynamics of ventromedial hypothalamus in defence and aggression

Fear and aggression are evolutionary conserved emotional responses that can be evoked by different stimuli. One of these stimuli is exposure to a threatening conspecific that depending on the context and history of previous encounters can elicit either defence and avoidance or approach and aggression. The ventrolateral division of the ventromedial hypothalamus (VMHvl) has been recently identified as a structure involved in both behaviours. Neural activity in the ventromedial hypothalamus has been shown to be necessary for defensive and aggressive behavioural responses to conspecific threats. In male mice, inhibition of neural activity in VMHvl reduces avoidance behaviour following exposure to an aggressive male, as well as attack behaviour following exposure to a subordinate male. However, whether the same or different neurons in VMHvl are responsible for defence and aggression toward social threat, how experience affects these responses and the identity of defence neurons in VMHvl remains unknown. Here we performed serial cFos labelling experiments and found that defence and aggression recruited partially overlapping populations in VMHvl. Using in vivo calcium endoscopy of VMHvl neuron activity during social defence and aggression we found that strong calcium responses were elicited upon exposure to the social stimulus and these were further modulated as the animal exhibited defensive or aggressive behaviours. Notably, specific neuronal calcium responses were identified that were correlated with defensive behaviours, some of these neurons were reacted to more than one behaviour, showing complex patterns of activity during aggression and defence. Moreover, calcium recordings over several days of either defence or aggression revealed a change in the ensemble activity between defence and aggression and this effect was dependent on the previous experience of an animal. At the same time we performed a series of functional manipulation experiments blocking or activating neuronal activity in different cell types of the VMHvl. We found separate populations of VMHvl Esr1+ and Nos1+ neurons that were able to modulate defensive responses to social threat. Together, these results demonstrate that the VMHvl encodes and controls both specific and overlapping features of defensive and aggressive behavioural responses to social threat

Hat problem on a graph

The topic of this thesis is the hat problem. In this problem, a team of n players enters a room, and a blue or red hat is randomly placed on the head of each player. Every player can see the hats of all of the other players but not his own. Then each player must simultaneously guess the color of his own hat or pass. The team wins if at least one player guesses his hat color correctly and no one guesses his hat color wrong, otherwise the team loses. The aim is to maximize the probability of winning. This thesis is based on publications, which form the second chapter. In the first chapter we give an overview of the published results. In Section 1.1 we introduce to the hat problem and the hat problem on a graph, where vertices correspond to players, and a player can see the adjacent players. To the hat problem on a graph we devote the next few sections. First, we give some fundamental theorems about the problem. Then we solve the hat problem on trees, cycles, and unicyclic graphs. Next we consider the hat problem on graphs with a universal vertex. We also investigate the problem on graphs with a neighborhood-dominated vertex. In addition, we consider the hat problem on disconnected graphs. Next we investigate the problem on graphs such that the only known information are degrees of vertices. We also present Nordhaus-Gaddum type inequalities for the hat problem on a graph. In Section 1.6 we investigate the hat problem on directed graphs. The topic of Section 1.7 is the generalized hat problem with q >= 2 colors. A modified hat problem is considered in Section 1.8. In this problem there are n >= 3 players and two colors. The players do not have to guess their hat colors simultaneously and we modify the way of making a guess. We give an optimal strategy for this problem which guarantees the win. Applications of the hat problem and its connections to different areas of science are presented in Section 1.9. We also give there a comprehensive list of variations of the hat problem considered in the literature

On the hat problem, its variations, and their applications

The topic of our paper is the hat problem in which each of n players is randomly fitted with a blue or red hat. Then everybody can try to guess simultaneously his own hat color by looking at the hat colors of the other players. The team wins if at least one player guesses his hat color correctly, and no one guesses his hat color wrong; otherwise the team loses. The aim is to maximize the probability of a win. There are known many variations of the hat problem. In this paper we give a comprehensive list of variations considered in the literature. We describe the applications of the hat problem and its variations, and their connections to different areas of science. We give the full bibliography of any papers, books, and electronic publications about the hat problem

Hat problem on a graph

The topic of this thesis is the hat problem. In this problem, a team of n players enters a room, and a blue or red hat is randomly placed on the head of each player. Every player can see the hats of all of the other players but not his own. Then each player must simultaneously guess the color of his own hat or pass. The team wins if at least one player guesses his hat color correctly and no one guesses his hat color wrong, otherwise the team loses. The aim is to maximize the probability of winning. This thesis is based on publications, which form the second chapter. In the first chapter we give an overview of the published results. In Section 1.1 we introduce to the hat problem and the hat problem on a graph, where vertices correspond to players, and a player can see the adjacent players. To the hat problem on a graph we devote the next few sections. First, we give some fundamental theorems about the problem. Then we solve the hat problem on trees, cycles, and unicyclic graphs. Next we consider the hat problem on graphs with a universal vertex. We also investigate the problem on graphs with a neighborhood-dominated vertex. In addition, we consider the hat problem on disconnected graphs. Next we investigate the problem on graphs such that the only known information are degrees of vertices. We also present Nordhaus-Gaddum type inequalities for the hat problem on a graph. In Section 1.6 we investigate the hat problem on directed graphs. The topic of Section 1.7 is the generalized hat problem with q >= 2 colors. A modified hat problem is considered in Section 1.8. In this problem there are n >= 3 players and two colors. The players do not have to guess their hat colors simultaneously and we modify the way of making a guess. We give an optimal strategy for this problem which guarantees the win. Applications of the hat problem and its connections to different areas of science are presented in Section 1.9. We also give there a comprehensive list of variations of the hat problem considered in the literature.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Independent hypothalamic circuits for social and predator fear

The neural circuits mediating fear to naturalistic threats are poorly understood. We found that functionally independent populations of neurons in the ventromedial hypothalamus (VMH), a region that has been implicated in feeding, sex and aggression, are essential for predator and social fear in mice. Our results establish a critical role for VMH in fear and have implications for selective intervention in pathological fear in humans