Abstract
SummaryThe hippocampal formation is anatomically and functionally divided into a dorsal and a ventral part, being involved in processing cognitive tasks and emotional stimuli, respectively. The ventral subiculum as part of the hippocampal formation projects to the medial prefrontal cortex (mPFC), but only very little is known about connections arising from the dorsal SUB (dSUB). Here, we investigate the dSUB to mPFC connectivity in acute brain slices using electrophysiology and optogenetics. We show that the anterior cingulate cortex (ACC) is the main target of dorsal subicular projections to the mPFC, with no preference between excitatory or inhibitory neurons. In addition to superficial neurons in the ACC, the prelimbic and infralimbic PFC are also targeted by subicular fibers. Thus, these novel region- and layer-specific connections between the dSUB and the prefrontal cortices challenge existing anatomical data and refine the hippocampocortical wiring diagram.
Highlights
The hippocampal formation is an anatomically complex brain region that consists of many different subregions, including the subiculum (SUB)
The ventral subiculum as part of the hippocampal formation projects to the medial prefrontal cortex, but only very little is known about connections arising from the dorsal SUB
We show that the anterior cingulate cortex (ACC) is the main target of dorsal subicular projections to the medial prefrontal cortex (mPFC), with no preference between excitatory or inhibitory neurons
Summary
The hippocampal formation is an anatomically complex brain region that consists of many different subregions, including the subiculum (SUB). Lesions of the ventral hippocampus, but not the dorsal part, for example, affect stress responses and emotional behavior. The SUB follows the hippocampus along the longitudinal axis. It receives its main input from the CA1 area, and together with the CA1, it is considered the main hippocampal output region as it is extensively connected to various cortical and subcortical regions The intrinsic hippocampal neuronal circuit is maintained along the dorsoventral axis; a functional dichotomy has been ascribed to the dorsal (dSUB) and ventral subiculum (vSUB). The dorsal part abundantly contains navigation-specific cells (O’Mara et al, 2009; but see Torromino et al, 2019), whereas the ventral part of the subiculum is involved in mediating stress responses (Herman and Mueller, 2006)
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