Episodic memory: neurological and neuromediator mechanisms

Abstract

Significant advances in understanding of neurological and neuromediatormechanisms of memory along with the causes ofmemory decline in aging were achieved recently. Functioning ofepisodic memory system needs considerable energetic andmaterial (neuromediator, protein) resources, and appears to behighly consuming for the body. Therefore, physiological mechanismsinhibiting episodic memory system exist in order to distributeresources for other brain functions. Primary engram isrecorded by hippocampal structures, which maintain reciprocalconnectivity with neocortex zones involved in synchronizedactivity. Cholinergic innervation of hippocampus and primaryzones of neocortex stabilizes process of primary engram formationwith consequent transformation of synapses in hippocampusstructures. At the next stage hippocampus transfers theengram to neocortex, where the information is processed byassociating with previous knowledge and is fixed by slowly developingsynaptogenesis and axonal growth. Noradrenergic innervationis an essential part of neuroplastic processes. Possiblecauses of memory decline in aging include powerful influencesof mature prefrontal cortex, inhibiting the hippocampal activity;insufficient stimulation of hippocampal memory system bynovel events with consequent decline of neurogenesis and neuroplasticity;disturbances in mechanisms of phasic release and clearance of neuromediators.

Keywords

• acetylcholine
• hippocampus
• noradrenaline
• prefrontal cortex
• synaptogenesis