Layer IV-Va neurons of the granular retrosplenial cortex (A29) project and control the activity of layers II-IV neurons of dysgranular retrosplenial cortex (A30) during contextual fear memory processing.

Congreso; XXXII Congreso Annual de de la Sociedad Argentina de Investigación en Neurociencia.; 2017

It has long been recognized that retrosplenial cortex (RSC) is anatomically divided in granular (A29) and dysgranular (A30) subregions and there is growing interest to understand how these organization contribute to memory processing. The aim of this study was to reveal functional participation of RSC subdivisions in contextual fear memory. To that end we used a recently characterized method that allows non-invasive and selective elimination of neurons in layers IV-Va of A29 (A29MK801 neurons). We determined that A29MK801 neurons are typical pyramidal neurons projecting to superficial layers of A30, suggesting its participation associating information between RSC subdivisions. Combining behavioral analysis with assessment of cFos and Egr-1 expression we demonstrate that elimination of A29MK801 neurons after, but not before, fear memory consolidation impaired activation of A30 and memory retrieval. The loss of A29MK801 neurons did not affect activation of other brain areas involved in fear memory processing including basolateral amygdala (BLA), CA1 field of hippocampus, medial (MEnt) and caudomedial entorhinal cortex (CEnt). Therefore, we reveal with sophisticated anatomical precision that during fear memory recall A29MK801 neurons are critically required for A30 activation and expression of adaptive freezing behavior.