Differential emotional experience induces elevated spine densities on basal dendrites of pyramidal neurons in the anterior cingulate cortex of Octodon degus

It appears likely that, in analogy to the synaptic development of sensory a nd motor cortices, which critically depends on sensory or motor stimulation (Rosenzweig and Bennett, 1996), the synaptic development of limbic cortica l regions are modulated by early postnatal cognitive and emotional experien ces. The very first postnatal experience, which takes place in a confined a nd stable familial environment, is the interaction of the newborn individua l with the parents and siblings (Gray, 1958). The aim of this quantitative morphological study was to analyze the impact of different degrees of juven ile emotional experience on the synaptic development in a limbic cortical a rea, the dorsal anterior cingulate cortex, a region which is involved in th e perception and regulation of emotions. We study the precocious trumpet-ta iled rat (Octodon degus) as the animal model, because, like human babies, t his species is born with functional visual and acoustic systems and the pup s are therefore capable of detecting even subtle environmental changes imme diately after birth (Reynolds and Wright, 1979; Poeggel and Braun, 1996; Br aun et al., 2000; Ovtscharoff and Braun, 2001). The results demonstrate tha t already a subtle disturbance of the familial environment such as handling induced Significantly elevated spine densities on the basal dendrites of l ayer III cortical pyramidal neurons. More severe disturbances of the emotio nal environment, such as periodic parental deprivation with or without subs equent chronic social isolation, resulted in an elevation of spine densitie s of similar magnitude as seen after handling and in addition, altered spin e densities confined to specific dendritic segments were observed in these groups. These observations unveil the remarkable sensitivity of the dorsal anterior cingulate cortex towards environmental influences and behavioral e xperiences during phases of postnatal development. The behavioral consequen ces of these experience-induced synaptic changes still need to be analyzed further to assess if they are beneficial or detrimental to the animals cogn itive and emotional capacities in later life. (C) 2001 IBRO. Published by E lsevier Science Ltd. All rights reserved.