Effect of the environment on the dendritic morphology of the rat auditory cortex

Abstract

The present study aimed to identify morphological correlates of environment-induced changes at excitatory synapses of the primary auditory cortex (A1). We used the Golgi-Cox stain technique to compare pyramidal cells dendritic properties of Sprague-Dawley rats exposed to different environmental manipulations.Sholl analysis, dendritic length measures, and spine density counts were used to monitor the effects of sensory deafness and an auditory version of environmental enrichment (EE). We found that deafness decreased apical dendritic length leaving basal dendritic length unchanged, whereas EE selectively increased basal dendritic length without changing apical dendritic length. On the contrary, deafness decreased while EE increased spine density in both basal and apical dendrites of A1 layer 2/3 (LII/III) neurons.To determine whether stress contributed to the observed morphological changes in A1, we studied neural morphology in a restraint-induced model that lacked behaviorally relevant acoustic cues. We found that stress selectively decreased apical dendritic length in the auditory but not in the visual primary cortex. Similar to the acoustic manipulation, stress-induced changes in dendritic length possessed a layer specific pattern displaying LII/III neurons from stressed animals with normal apical dendrites but shorter basal dendrites, while infragranular neurons (layers V and VI) displayed shorter apical dendrites but normal basal dendrites. The same treatment did not induce similar changes in the visual cortex, demonstrating that the auditory cortex is an exquisitely sensitive target of neocortical plasticity, and that prolonged exposure to different acoustic as well as emotional environmental manipulation may produce specific changes in dendritic shape and spine density.

A Role for RhoB in Synaptic Plasticity and the Regulation of Neuronal Morphology

“…The functional significance of this change is unclear, although it is likely to alter the integrative properties of the neurons. It is, however, interesting that secondary dendrites may show more activity-dependent morphological plasticity than primary dendrites (Charych et al, 2006;Horton et al, 2007), and that basal and apical dendrites differ in their activity-dependent plasticity (Cook et al, 2004;Brown et al, 2005;Bose et al, 2010). The levels of RhoB in the rat and mouse CNS are high from around embryonic day 16 to birth, and then decrease slightly postnatally (Olenik et al, 1999;Komagome et al, 2000;Yoon et al, 2007).…”

Synaptogenesis and development of pyramidal neuron dendritic morphology in the chimpanzee neocortex resembles humans

“…Dendrites regulate the integration of inputs and provide sites for synapses on spines (41, 42). As such, they are extremely plastic structures that undergo changes in response to experience, which is especially evident during development (12,(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57). For this reason, a delay in the formation of dendritic trees in the prefrontal cortex may be important for processing and integrating the extensive load of information that both humans and chimpanzees acquire during development and for maintaining plasticity of executive functions.…”

Mother’s voice and heartbeat sounds elicit auditory plasticity in the human brain before full gestation

“…Numerous animal studies have shown that brain development relies on developmentally appropriate acoustic stimulation early in life (22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32). Auditory deprivation during critical periods can adversely affect brain maturation and lead to long-lasting neural despecialization in the auditory cortex (AC), whereas auditory enrichment in the early postnatal period can enhance neural sensitivity in the primary AC, as well as improve auditory recognition and discrimination abilities.…”