B01 Subcortical control of neuronal activity in the hipocampal formation
We have shown previously that a mechanistic coupling of motor signaling and hippocampal theta-oscillations exists on the subcortical level of the medial septum and the diagonal Band of Broca (MSDB). We have found that the action potential firing of medial septal neurons actively controls movement velocity during locomotion, entrains movement-correlated theta oscillations and leads to velocity-adapted membrane potential changes in CA1 principal neurons and neurons of the medial entorhinal cortex. However, almost nothing is known about the functional integration of medial septal neurons into locomotor circuits. We have identified specific anatomical and functional connectivity patterns between subcortical areas and excitatory VGluT2+ cell populations in the MSDB. We have early evidence for direct synaptic transmission from MRN onto glutamatergic neurons of the MSDB, while norepinephrine likely modulates the firing rates of glutamatergic neurons via MSDB interneurons. We will therefore investigate if the interaction of excitatory and inhibitory neurons in the MSDB is controlled by an antagonistic action of median raphe nucleus and locus coeruleus, which may be relevant for the initiation of different behavioral states. This interaction may control not only the onset and vigor of locomotor activity, but also hippocampal theta oscillations.