The idea of the dentate gyrus as a gate or filter at the entrance to the hippocampus, blocking or filtering incoming excitation from the entorhinal cortex, has been an intriguing one. Here we review the historical development of the idea, and discuss whether it may be possible to be more specific in defining this gate. We propose that dentate function can be understood within a context of Hebbi...

We studied brain synapsin I and II mRNA levels using the amygdala kindling model of epilepsy. There were significant increases in the synapsin I mRNA level in the granule cell layer of the hippocampal bilateral dentate gyrus. One to 8 h after seizures, the level in the dentate gyrus ipsilateral to stimulation increased by 44.2-73.2%, compared with the control level. Of the time points investiga...

A fundamental property of neuronal networks in Ammon's horn is that each area comprises a single glutamatergic cell population and various types of GABAergic neurons. Here we describe an exception to this rule, in the form of granule cells that reside within the CA3 area and function as glutamatergic nonprincipal cells with distinct properties. CA3 granule cells in normal, healthy rats, similar...

Neurogenesis in the dentate gyrus has been implicated in cognitive functions, including learning and memory, and may be abnormal in major neuropsychiatric disorders, such as depression. Dentate neurogenesis is regulated by interactions between extrinsic factors and intrinsic transcriptional cascades that are currently not well understood. Here we show that Tbr2 (also known as Eomes), a T-box tr...

The dentate gyrus is the primary afferent pathway into the hippocampus, but there is little information concerning the molecular influences that govern its formation. In particular, the control of migration and cell positioning of dentate granule cells is not clear. We have characterized more fully the timing and route of granule cell migration during embryogenesis using in utero retroviral inj...

PURPOSE To identify changes in the embryology of the hippocampus responsible for its adult anatomy. METHODS Ten human fetal specimens ranging from 13 to 24 weeks' gestational age were examined with MR imaging. Dissections and histologic sections of 10 different specimens of similar ages were compared with MR imaging findings. RESULTS At 13 to 14 weeks' gestation, the unfolded hippocampus, o...