Behavioural neuroscienceMapping of brain networks involved in consolidation of lamb recognition memory
Section snippets
Experiment 1: maintenance of lamb recognition after various mother-young contact and separation durations
In this first experiment, we studied the effects of various durations of mother-young separations (from 3 h to 72 h) following different periods of postpartum contact (from 4 h to 7 days) on olfactory recognition of the familiar lamb. We also looked at maternal responsiveness since we had previously observed that ewes separated from their lambs also show a loss of maternal care toward their own young (Lévy et al., 1991). We hypothesized that both maternal responsiveness and recognition of the
Maternal responsiveness
Some ewes were not maternal at the end of the separation and rejected both familiar and unfamiliar lambs. Retention performances of maternal responsiveness appeared to be mainly dependent on the separation duration, whereas time of contact prior to separation had no effect. After 4 h of mother-young contact, the proportion of maternal ewes did not differ significantly between 3 h and 6 h of mother-young separation (Fig. 1A). This proportion was significantly lower when the duration of the
Discussion
Data from this experiment show that maintenance of maternal responsiveness and selectivity are differently affected by the duration of mother-young contact and separation.
A rapid fading of maternal responsiveness with increasing separation length was observed. An increase of mother-young contact cannot compensate for this decline. This fall of maternal responsiveness in ewes separated from their lambs for 36 or 72 h might be related to the fact that experimenters held ewes while alien lambs
Experimental procedures
Eighteen multiparous Ile-de-France ewes were housed individually (2× 1 m) 1 week before parturition. Parturition was synchronized as described in the first experiment. At lambing, only one lamb was left with its mother to standardize litter size. Four groups of ewes were studied. In two experimental groups, mothers were separated from their lamb for 3 h, after either 4 h of contact (n=5) or 7 days of contact (n=6). The lambs were reunited with their mother for 2 h, this period allowing maximal
Results
For all the structures, no difference between both control groups was observed (4 h or 7 days of contact followed by 5 h of separation). Consequently, these groups were pooled in a single control group (n=7).
Discussion
Our experiment explored brain networks activated during retrieval of lamb olfactory memory performed under a labile or a consolidated memory state. While previous studies have shown that during memory formation, extensive activation is found throughout the olfactory processing network (Da Costa et al 1997, Keller et al 2004a), our results suggest that there are only a few brain structures engaged in retrieval of lamb recognition memory.
Acknowledgments
We thank Francis Dupont and the shepherds for the care they provided to the animals. We are also grateful to Francis Paulmier and the whole staff of the hospital for experimental facilities, and especially to Christian Moussu and Jean-Philippe Dubois for their nocturnal assistance. The help of Nicole Jouaneau, Gérard Vénier and Eric Archer was greatly appreciated during the experiments. We thank Guillaume Ferreira and Anne-Marie Mouly for critical reading as well as Raymond Nowak and Sue Edrich
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2018, Behavioural Brain ResearchCitation Excerpt :Recognition of the familiar lamb was assessed through a selectivity test performed at 2 h post-partum just after the last observation of maternal behavior. After removing the familiar lamb, the selectivity test consisted, of a 3 min presentation of an unfamiliar lamb of approximately the same age, followed by presentation again of the familiar lamb for 3 min [32,33]. Duration of suckling instead of licking was recorded, in addition to the behavioral items observed for maternal behavior.
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2017, Behavioural ProcessesCitation Excerpt :The attraction to amniotic fluid helps a female learn the individual olfactory characteristics of her offspring, so that within 5–10 min she has established a selective bond with her young through smell. Most mothers show a stable selectivity in nursing within 0.5–2 h after birth (Keller et al., 2003), but are only able to keep these olfactory cues in memory for no more than 3 days, if not in close proximity to their young (Keller et al., 2005). Non-olfactory recognition with help from vocal and visual cues appears slightly later, and becomes fully effective by 6–12 h (Ferreira et al., 2000; Keller et al., 2003) or in some cases even earlier at 2–4 h postpartum (Poindron et al., 2007b; Keyserlingk and Weary, 2007), when mothers have developed a strong enough visual and acoustic recognition of their neonates to distinguish between their own offspring and an unfamiliar one without the help of olfactory cues.
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2017, Hormones, Brain and Behavior: Third EditionBehavioral evidence of heterospecific bonding between the lamb and the human caregiver and mapping of associated brain network
2016, PsychoneuroendocrinologyCitation Excerpt :However, frontal regions are also known to be involved in retrieval processes (Hasegawa, 2000; Buckner and Wheeler, 2001). For instance, a selective enhancement of c-Fos activation is observed in the frontal medial and orbitofrontal cortices in sheep mothers re-exposed to their lamb after a brief separation at 7 days post-partum, when the olfactory memory is consolidated (Keller et al., 2005). C-Fos activation observed in lambs of the PRESENCE group could therefore reflect retrieval of the caregiver odor.
Common and divergent psychobiological mechanisms underlying maternal behaviors in non-human and human mammals
2015, Hormones and BehaviorCitation Excerpt :However, their maternal responsiveness fades rapidly. A 36–72 hour separation period that follows 4 h of contact after parturition induces rejection of the familiar lamb (Keller et al., 2005; Lévy et al., 1991). This decline in maternal responsiveness cannot be compensated for by increasing initial mother–young contact because the rejection is also observed when the separation is performed after a week of postpartum interaction (Keller et al., 2005).