Spatial Representation in the Entorhinal Cortex

Abstract

Conclusions. Our study is part of recent attempts in "neuroeconomics" and the "cognitive neuroscience of social behavior" to understand the social brain and the associated moral emotions (37-44). However, this study sought to identify the neural basis of the altruistic punishment of defectors. The ability to develop social norms that apply to large groups of genetically unrelated individuals and to enforce these norms through altruistic sanctions is one of the distinguishing characteristics of the human species. Altruistic punishment is probably a key element in explaining the unprecedented level of cooperation in human societies (1-3). We hypothesize that altruistic punishment provides relief or satisfaction to the punisher and activates, therefore, reward-related brain regions. Our design generates five contrasts in which this hypothesis can be tested, and the anterior dorsal striatum is activated in all five contrasts, which suggests that the caudate plays a decisive role in altruistic punishment. Caudate activation is particularly interesting because this brain region has been implicated in making decisions or taking actions that are motivated by anticipated rewards (17)(18)(19)(20). The prominent role of the caudate in altruistic punishment is further supported by the fact that those subjects who exhibit stronger caudate activation spend more money on punishing defectors. Moreover, our results also shed light on the reasons behind this correlation. Subjects who exhibit higher caudate activation at the maximal level of punishment if punishment is costless for them also spend more resources on punishment if punishment becomes costly. Thus, high caudate activation seems to be responsible for a high willingness to punish, which suggests that caudate activation reflects the anticipated satisfaction from punishing defectors. Our results therefore support recently developed social preference models (6-8), which assume that people have a preference for punishing norm violations, and illuminate the proximate mechanism behind evolutionary models of altruistic punishment. As the interface between hippocampus and neocortex, the entorhinal cortex is likely to play a pivotal role in memory. To determine how information is represented in this area, we measured spatial modulation of neural activity in layers of medial entorhinal cortex projecting to the hippocampus. Close to the postrhinal-entorhinal border, entorhinal neurons had stable and discrete multipeaked place fields, predicting the rat's location as accurately as place cells in the hippocampus. Precise positional modulation was not observed more ventromedially in the entorhinal cortex or upstream in the postrhinal cortex, suggesting that sensory input is transformed into durable allocentric spatial representations internally in the dorsocaudal medial entorhinal cortex.An extensive body of evidence suggests that the hippocampus is essential for fast encoding and storage of new episodic memories but has a more limited role in remote memory, which is thought to be st...

Towards a functional organization of the medial temporal lobe memory system: Role of the parahippocampal and medial entorhinal cortical areas

“…Areas that lie along the central stem constitute overlapping elements of both types of episodes. Consistent with previous reports (Fyhn et al, 2004;Hargreaves et al, 2005), MEC neuronal activity was associated with an animal's position along the maze. A strict and consistent periodic spacing in the spatial firing pattern was not observed in these cells, similar to a recent report of a breakdown in the consistent grid pattern (characterized as a ''resetting'') of MEC neuronal grid firing when animals' movements on a maze were constrained to make hairpin turns (Derdikman et al, 2006).…”

“…Studies in humans have indentified a ''parahippocampal place area'' within the parahippocampal cortex, which is activated by presentation of spatial scenes but not single or multiple objects (Epstein and Kanwisher, 1998;Epstein, 2005). In rats, while perirhinal and LEC neurons have poor spatial coding properties, MEC neurons show strong spatial coding (Quirk et al, 1992;Fyhn et al, 2004;Hargreaves et al, 2005), and there is some evidence of weak spatial firing in the postrhinal cortex Burwell and Hafeman, 2003). In particular, the MEC is the location of the grid cells, boundary cells, and head direction cells that reflect different aspects of spatial processing (Sargolini et al, 2006;Moser and Moser, 2008;Solstad et al, unpublished).…”

Computation by oscillations: Implications of experimental data for theoretical models of grid cells

“…Behavioral research indicates that cells in the medial entorhinal cortex (mEC), called ''grid cells,'' fire in spatially specific locations, which repeat at regular intervals (Fyhn et al, 2004;Sargolini et al, 2006;Moser and Moser, 2008). The pattern of spiking activity forms a hexagonal grid of firing, and the spacing and field size of the spiking changes along the dorsal-ventral axis of mEC (Sargolini et al, 2006).…”

Le codage de l’espace

“…Les travaux du couple Moser se focalisent alors sur la recherche d'une activité dépendante de l'espace dans le cortex entorhinal : existet-il un code spatial dans cette structure qui permette de générer la carte hippocampique ? Ils découvrent ainsi des neurones du cortex entorhinal médian 1 dont l'activité corrèle avec la position de l'animal dans l'espace [14]. Toutefois, ces cellules ont une activité particulière puisqu'elles présentent plusieurs champs de lieu, qui ne se recouvrent pas et forment un motif hexagonal répétitif en forme de « grille » [15].…”

“…De plus, ces cellules déchargent à intervalles réguliers et au-delà de l'environnement déjà exploré. Il s'agit donc d'un codage global de l'espace qui contraste avec la décharge locale de la cellule de lieu [14,15]. Lorsqu'une cellule de grille est enregistrée dans différents environnements, elle maintient la taille et l'espacement du champ, mais l'orientation et la phase de la grille sont modifiées [16].…”