The role of basal forebrain cholinergic neurons in fear and extinction memory

Neurobiol Learn Mem. 2016 Sep:133:39-52. doi: 10.1016/j.nlm.2016.06.001. Epub 2016 Jun 2.

Abstract

Cholinergic input to the neocortex, dorsal hippocampus (dHipp), and basolateral amygdala (BLA) is critical for neural function and synaptic plasticity in these brain regions. Synaptic plasticity in the neocortex, dHipp, ventral Hipp (vHipp), and BLA has also been implicated in fear and extinction memory. This finding raises the possibility that basal forebrain (BF) cholinergic neurons, the predominant source of acetylcholine in these brain regions, have an important role in mediating fear and extinction memory. While empirical studies support this hypothesis, there are interesting inconsistencies among these studies that raise questions about how best to define the role of BF cholinergic neurons in fear and extinction memory. Nucleus basalis magnocellularis (NBM) cholinergic neurons that project to the BLA are critical for fear memory and contextual fear extinction memory. NBM cholinergic neurons that project to the neocortex are critical for cued and contextual fear conditioned suppression, but are not critical for fear memory in other behavioral paradigms and in the inhibitory avoidance paradigm may even inhibit contextual fear memory formation. Medial septum and diagonal band of Broca cholinergic neurons are critical for contextual fear memory and acquisition of cued fear extinction. Thus, even though the results of previous studies suggest BF cholinergic neurons modulate fear and extinction memory, inconsistent findings among these studies necessitates more research to better define the neural circuits and molecular processes through which BF cholinergic neurons modulate fear and extinction memory. Furthermore, studies determining if BF cholinergic neurons can be manipulated in such a manner so as to treat excessive fear in anxiety disorders are needed.

Keywords: Contextual conditioning; Extinction recall; Fear conditioning; Fear extinction; Inhibitory avoidance; Magnocellular; Nucleus basalis.

Publication types

  • Review
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Basal Forebrain / physiology*
  • Basal Nucleus of Meynert / physiology*
  • Basolateral Nuclear Complex / physiology*
  • Cholinergic Neurons / physiology*
  • Conditioning, Classical / physiology*
  • Extinction, Psychological / physiology*
  • Fear / physiology*
  • Humans
  • Mental Recall / physiology*