RESUMO
The superior colliculus is a structure located in the dorsal midbrain with well conserved function and connectivity across species. Essential for survival, the superior colliculus has evolved to trigger rapid orientation and avoidance movements in response to external stimuli. The increasing recognition of the widespread connectivity of the superior colliculus, not only with brainstem and spinal cord, but also with virtually all brain structures, has rekindled the interest on this structure and revealed novel roles in the past few years. In this review, we focus on the most recent advancements in understanding its cellular composition, connectivity and function, with a particular focus on how the cellular diversity and connectivity arises during development, as well as on its recent role in the emergence of sensory circuits.
RESUMO
Cajal-Retzius cells (CRs) are transient neurons, disappearing almost completely in the postnatal neocortex by programmed cell death (PCD), with a percentage surviving up to adulthood in the hippocampus. Here, we evaluate CR's role in the establishment of adult neuronal and cognitive function using a mouse model preventing Bax-dependent PCD. CRs abnormal survival resulted in impairment of hippocampus-dependent memory, associated in vivo with attenuated theta oscillations and enhanced gamma activity in the dorsal CA1. At the cellular level, we observed transient changes in the number of NPY+ cells and altered CA1 pyramidal cell spine density. At the synaptic level, these changes translated into enhanced inhibitory currents in hippocampal pyramidal cells. Finally, adult mutants displayed an increased susceptibility to lethal tonic-clonic seizures in a kainate model of epilepsy. Our data reveal that aberrant survival of a small proportion of postnatal hippocampal CRs results in cognitive deficits and epilepsy-prone phenotypes in adulthood.