Tool Use Specific Adult Neurogenesis and Synaptogenesis in Rodent (Octodon degus) Hippocampus

Abstract

We previously demonstrated that degus (Octodon degus), which are a species of small caviomorph rodents, could be trained to use a T-shaped rake as a hand tool to expand accessible spaces. To elucidate the neurobiological underpinnings of this higher brain function, we compared this tool use learning task with a simple spatial (radial maze) memory task and investigated the changes that were induced in the hippocampal neural circuits known to subserve spatial perception and learning. With the exposure to an enriched environment in home cage, adult neurogenesis in the dentate gyrus of the hippocampus was augmented by tool use learning, but not radial maze learning, when compared to control conditions. Furthermore, the proportion of new synapses formed in the CA3 region of the hippocampus, the target area for projections of mossy fiber axons emanating from newborn neurons, was specifically increased by tool use learning. Thus, active tool use behavior by rodents, learned through multiple training sessions, requires the hippocampus to generate more novel neurons and synapses than spatial information processing in radial maze learning.

Enriched Environment Increases PCNA and PARP1 Levels in Octopus vulgaris Central Nervous System: First Evidence of Adult Neurogenesis in Lophotrochozoa

“…In insects mushroom bodies, neuroblasts proliferation results an increase in specimens reared in enriched environment compared to specimens housed in sensory deprivation, also demonstrated in analogue experiments on crustaceans (Hansen and Schmidt, , ; Sullivan et al., ; Ayub et al., ), and the ablation of neuroblasts implies a damage of learning capabilities (Scotto‐Lomassese et al., , , ; Cayre et al., ). In mammals, both enriched environment and cognitive stimulation influence proliferation and survival of newborn interneurons (Rochefort et al., ; Shors et al., ; Clemenson et al., ), and their capacity to form new synapses (Kondo et al., ; Kumazawa‐Manita et al., ; Lepousez et al., ), in olfactory bulb as well as in hippocampus, as shown in numerous behavioral experiments (Kempermann and Gage, ; Magavi et al., ; Snyder et al., ; Lepousez et al., ). The function of new neurons seems to alter the existent circuitry to enhance the information processing (Kempermann, ; Glasper et al., ).…”

“…The effects of the environment on adult neurogenesis are emphasized in numerous studies showing its influence on hippocampus of the laboratory animals kept in specific housing conditions, such as environmental enrichment (Brown et al., ; Sale et al., ; Curlik et al., ; Opendak and Gould, ). One definition of enriched environment is “a designed world, aiming at providing a particular, mostly cognitive challenge” (Kempermann et al., ), it consists of adding live prey, sibling and new objects to standard housing conditions, in order to provide a set of sensory, intellectual, social, and physical stimulations (Sale et al., ; Kumazawa‐Manita et al., ).…”

RECOLLECTION OF WHAT-WHERE-WHICH MEMORY IN DEGUS (<i>OCTODON DEGUS</i>)

“…use: Okanoya, Tokimoto, Kumazawa, Hihara, & Iriki, 2008;Kumazawa-Manita, Hama, Miyawaki, & Iriki, 2013;spatial cognition: Popović, Madrid, Rol, Caballero-Bleda, & Popović, 2010;Uekita & Okanoya, 2011;Kumazawa-Manita et al, 2013). Further studies of various non-social cognitive abilities in degus would be valuable; in view of their role as a model of Alzheimer disease, their memory processes may be especially worthy of attention.…”

Development of a control task for clarifying the neural mechanisms underlying tool-use behavior in rats (Rattus norvegicus)

“…Previous studies on humans [1] and non-human animals [2] have attempted to examine the neural mechanisms underlying tool-use behavior. One study on rodents reported that tool-use behavior induced adult neurogenesis in the dental gyrus of the hippocampus [3]. Another study on monkeys reported a significant increase in cerebral blood flow in specific areas when performing tool-use behavior [4].…”