To investigate whether or not aging of nonhuman primates is accompanied by a region-specific neuron loss in the hippocampal formation, we used the optical fractionator technique to obtain stereological estimates of unilateral neuron numbers of the hippocampi of eight young (0-4 years) and five aged (18-31 years) male rhesus monkeys (Macaca mulatta). Our results show a preservation of neurons (m...

This paper presents a computational model for encoding and inferential reuse of memories, based on novelty and familiarity principle. The method is strongly inspired by the state of the art understanding of the hippocampal functioning and especially its role in novelty detection and episodic memory formation in relation to spatial context. A navigation task is used to provide an experimental se...

Morphine’s effects on learning and memory processes are well known to depend on synaptic plasticity in the hippocampus. Whereas the role of the hippocampus in morphine-induced amnesia and state-dependent learning is established, the biochemical and molecular mechanisms underlying these processes are poorly understood. The present study intended to investigate whether administration of morphine ...

In a review of the literature on the development of the medial temporal lobe region in humans, monkeys, and rodents, Bachevalier and Beauregard indicated that in primates, memory functions subserved by this neural system emerge early in life and increment gradually with further postnatal maturation. Furthermore, they stated that the late-developing memory functions of normal neonates was more l...

The serotonergic and cholinergic neurotransmitter systems interact during processes of learning and memory. Although the effects of aging on cholinergic innervation has been extensively investigated, it is not clear how the serotonergic innervation is altered during aging. The hippocampal formation, a target area of both cholinergic and serotonergic fibers, is a crucial structure for learning a...

Understanding the neural correlates of brain function is an extremely challenging task, since any cognitive process is distributed over a complex and evolving network of neurons that comprise the brain. In order to quantify observed changes in neuronal dynamics during hippocampal memory formation, we present metrics designed to detect directional interactions and the formation of functional neu...

The amyloid precursor protein (APP) undergoes sequential cleavages to generate various polypeptides, including the amyloid b (1–42) peptide (Ab[1–42]), which is believed to play a major role in amyloid plaque formation in Alzheimer’s disease (AD). Here we provide evidence that, in contrast with its pathological role when accumulated, endogenous Ab in normal hippocampi mediates learning and memo...

Although extensive behavioral studies have demonstrated that hippocampal lesions impair navigation toward specific places, the role of hippocampal neuronal activity in the development of efficient navigation during place learning remains unknown. The aim of the present study was to investigate how hippocampal neuronal activity changes as rats learn to navigate efficiently to acquire rewards in ...

PURPOSE We determined the frequency of amygdalar-hippocampal atrophy in patients with congenital porencephaly-related seizure disorders to ascertain whether specific MR features of the porencephaly correlate with amygdalar-hippocampal atrophy and epilepsy. METHODS We studied brain MR images of 22 patients with congenital porencephaly and measured the volume of the amygdala, the hippocampal fo...