Role of the habenular complex in cognitive processes.
演題番号 : S1-10-1-4
Lucas Serge Lecourtier:1
1:Psychology, Strasbourg University
The habenular complex (HbCpl) is a diencephalic structure composed of two subnuclei, namely the medial habenula (MHb) and the lateral habenula (LHb). Those are dissimilar with respect to their intrinsic neuronal populations and their afferents and efferents. The MHb receives inputs mainly from posterior septal nuclei and sends its major projection to the interpeduncluar nucleus. The LHb receives inputs from both limbic and basal ganglia structures and sends projections to monoaminergic areas of the midbrain, through which it participates in the modulation of dopaminergic, serotonergic and noradrenergic transmissions. The LHb tonically inhibits dopaminergic and serotonergic release and stimulates noradrenergic release. Moreover, the LHb indirectly stimulates the cholinergic septohippocampal pathway. This very unique position makes the HbCpl a point of convergence of informations stemming from both the limbic system and the basal ganglia. Recently, a role for the HbCpl in cognitive behaviours has been emphasized through lesion studies in rodents. In fact, HbCpl lesions induced spatial memory deficits in the water maze. Also, in a task of attention, namely the 5-Choice Serial Reaction Time task (5-CSRTT), HbCpl lesions led to two distinct types of alterations, i.e., the immediate occurrence of an impulsive mode of behaviour, indicative of a loss of motor control, and the delayed apparition of attention deficits. One possible explanation for the increased impulsivity in the 5-CSRTT would be that HbCpl lesions provoked the cessation of the tonic inhibition of the LHb upon dopamine transmission. According to spatial memory deficits, it is more likely that those were the consequences of disturbances within serotonergic and cholinergic systems. In conclusion, it has been shown that the HbCpl plays a role not only in limbic system-mediated cognitive processes but also in basal ganglia-mediated motor control during those tasks, making it a true interface between both systems.