Dynamics of dendritic spines in the mouse auditory cortex during memory formation and memory recall

Abstract

Long-lasting changes in synaptic connections induced by relevant experiences are believed to represent the physical correlate of memories. Here, we combined chronic in vivo two-photon imaging of dendritic spines with auditory-cued classical conditioning to test if the formation of a fear memory is associated with structural changes of synapses in the mouse auditory cortex. We find that paired conditioning and unpaired conditioning induce a transient increase in spine formation or spine elimination, respectively. A fraction of spines formed during paired conditioning persists and leaves a long-lasting trace in the network. Memory recall triggered by the reexposure of mice to the sound cue did not lead to changes in spine dynamics. Our findings provide a synaptic mechanism for plasticity in sound responses of auditory cortex neurons induced by auditory-cued fear conditioning; they also show that retrieval of an auditory fear memory does not lead to a recapitulation of structural plasticity in the auditory cortex as observed during initial memory consolidation.learning | auditory fear conditioning | reconsolidation

Drug-Paired Contextual Stimuli Increase Dendritic Spine Dynamics in Select Nucleus Accumbens Neurons

“…Repeated administration of DA-releasing psychostimulant drugs produces both transient and long-lasting changes in the size and density of dendritic spines on these GABAergic neurons (Dumitriu et al, 2012;Kolb, 1997, 1999;Shen et al, 2009). These dendritic spines may be locations of memory storage in the brain (Lamprecht and LeDoux, 2004); various behavioral experiences have been shown to increase spine formation in vivo (Holtmaat et al, 2005(Holtmaat et al, , 2006Lai et al, 2012;Moczulska et al, 2013;Muñoz-Cuevas et al, 2013). Importantly, by comparing the effects of intra-VTA and systemic injections of amphetamine, we recently found that spine plasticity maps onto the accrual of associative drug conditioning rather than the induction of nonassociative drug sensitization (Singer et al, 2009).…”

Integrating Hebbian and homeostatic plasticity: the current state of the field and future research directions

“…Hebbian mechanisms have correlates in synaptic structural plasticity, in which LTP is correlated with the formation of new spines [71,72], and LTD is associated with the loss of pre-existing spines [73]. The in vivo upregulation of spine dynamics has been observed following sensory deprivation in somatosensory cortex [74 -77], olfactory cortex [78,79], auditory cortex [80] and visual cortex [74,77,81 -83], and following learning in motor cortex [84][85][86] where the memory of the learned motor task depends on the newly formed synapses [87].…”

The dynamic connectome

“…Thus, there are structural correlates of LTP and LTD, which can be assessed with imaging methods. Importantly, also chronic imaging in transgenic mice during a behavioral task showed that transient increases in spine formation rates are correlated with learning [6,12]. Major findings from a study investigating the impact of auditory cued fear conditioning on spine dynamics in the .…”