Limits...
Long-term avoidance memory formation is associated with a transient increase in mushroom body synaptic complexes in leaf-cutting ants.

Falibene A, Roces F, Rössler W - Front Behav Neurosci (2015)

Bottom Line: Long-term avoidance memory formation was associated with a transient change in MG densities.At days 4 and 15 after learning-when ants still showed plant avoidance-MG densities had decreased to the initial state.Sensory exposure by the simultaneous collection of several, instead of one, non-harmful plant species resulted in a decrease in MG densities in the olfactory lip.

View Article: PubMed Central - PubMed

Affiliation: Department of Behavioral Physiology and Sociobiology, Biozentrum, University of Würzburg Würzburg, Germany.

ABSTRACT
Long-term behavioral changes related to learning and experience have been shown to be associated with structural remodeling in the brain. Leaf-cutting ants learn to avoid previously preferred plants after they have proved harmful for their symbiotic fungus, a process that involves long-term olfactory memory. We studied the dynamics of brain microarchitectural changes after long-term olfactory memory formation following avoidance learning in Acromyrmex ambiguus. After performing experiments to control for possible neuronal changes related to age and body size, we quantified synaptic complexes (microglomeruli, MG) in olfactory regions of the mushroom bodies (MBs) at different times after learning. Long-term avoidance memory formation was associated with a transient change in MG densities. Two days after learning, MG density was higher than before learning. At days 4 and 15 after learning-when ants still showed plant avoidance-MG densities had decreased to the initial state. The structural reorganization of MG triggered by long-term avoidance memory formation clearly differed from changes promoted by pure exposure to and collection of novel plants with distinct odors. Sensory exposure by the simultaneous collection of several, instead of one, non-harmful plant species resulted in a decrease in MG densities in the olfactory lip. We hypothesize that while sensory exposure leads to MG pruning in the MB olfactory lip, the formation of long-term avoidance memory involves an initial growth of new MG followed by subsequent pruning.

No MeSH data available.


Related in: MedlinePlus

Size-dependent synaptic organization in the MB calyces. (A) Body morphometry for A. ambiguus workers. The following relationship was found between head width (HW) and body mass (M): HW = 0.9066*M0.4139; R2 = 0.99. To compare the MB structure between ants of different sizes we selected outside workers with sizes corresponding to both extremes of the foragers’ size range (HW: 1.0–2.0 mm), defining them as medium and large. Every dot represents an ant (N = 40). (B) Bouton densities remained constant between ants of different sizes. (C) Lip volume increased with ant size. In (B,C) dots represent the mean value and lines the S.D. ***p < 0.001. Medium, N = 8; large, N = 10.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4389540&req=5

Figure 3: Size-dependent synaptic organization in the MB calyces. (A) Body morphometry for A. ambiguus workers. The following relationship was found between head width (HW) and body mass (M): HW = 0.9066*M0.4139; R2 = 0.99. To compare the MB structure between ants of different sizes we selected outside workers with sizes corresponding to both extremes of the foragers’ size range (HW: 1.0–2.0 mm), defining them as medium and large. Every dot represents an ant (N = 40). (B) Bouton densities remained constant between ants of different sizes. (C) Lip volume increased with ant size. In (B,C) dots represent the mean value and lines the S.D. ***p < 0.001. Medium, N = 8; large, N = 10.

Mentions: Comparison of medium (HW = 1.14 ± 0.02 mm) and large (HW = 1.89 ± 0.02 mm) outside workers (Figure 3A) did not reveal significant differences in ND lip bouton densities (F1,16 = 2.46, p = 0.14; ANOVA; Figure 3B). However, both lip (F1,16 = 20.57, p = 0.0003; ANOVA; Figure 3C) and collar volumes (F1,16 = 19.91, p = 0.0004; ANOVA) increased with ant body size. Both results are in accordance with results reported for the highly polymorphic leaf-cutting ant A. vollenweideri (Groh et al., 2014). In the following experiments, we therefore analyzed brains of ant foragers of a similar range in size to exclude variability within and between groups.


Long-term avoidance memory formation is associated with a transient increase in mushroom body synaptic complexes in leaf-cutting ants.

Falibene A, Roces F, Rössler W - Front Behav Neurosci (2015)

Size-dependent synaptic organization in the MB calyces. (A) Body morphometry for A. ambiguus workers. The following relationship was found between head width (HW) and body mass (M): HW = 0.9066*M0.4139; R2 = 0.99. To compare the MB structure between ants of different sizes we selected outside workers with sizes corresponding to both extremes of the foragers’ size range (HW: 1.0–2.0 mm), defining them as medium and large. Every dot represents an ant (N = 40). (B) Bouton densities remained constant between ants of different sizes. (C) Lip volume increased with ant size. In (B,C) dots represent the mean value and lines the S.D. ***p < 0.001. Medium, N = 8; large, N = 10.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4389540&req=5

Figure 3: Size-dependent synaptic organization in the MB calyces. (A) Body morphometry for A. ambiguus workers. The following relationship was found between head width (HW) and body mass (M): HW = 0.9066*M0.4139; R2 = 0.99. To compare the MB structure between ants of different sizes we selected outside workers with sizes corresponding to both extremes of the foragers’ size range (HW: 1.0–2.0 mm), defining them as medium and large. Every dot represents an ant (N = 40). (B) Bouton densities remained constant between ants of different sizes. (C) Lip volume increased with ant size. In (B,C) dots represent the mean value and lines the S.D. ***p < 0.001. Medium, N = 8; large, N = 10.
Mentions: Comparison of medium (HW = 1.14 ± 0.02 mm) and large (HW = 1.89 ± 0.02 mm) outside workers (Figure 3A) did not reveal significant differences in ND lip bouton densities (F1,16 = 2.46, p = 0.14; ANOVA; Figure 3B). However, both lip (F1,16 = 20.57, p = 0.0003; ANOVA; Figure 3C) and collar volumes (F1,16 = 19.91, p = 0.0004; ANOVA) increased with ant body size. Both results are in accordance with results reported for the highly polymorphic leaf-cutting ant A. vollenweideri (Groh et al., 2014). In the following experiments, we therefore analyzed brains of ant foragers of a similar range in size to exclude variability within and between groups.

Bottom Line: Long-term avoidance memory formation was associated with a transient change in MG densities.At days 4 and 15 after learning-when ants still showed plant avoidance-MG densities had decreased to the initial state.Sensory exposure by the simultaneous collection of several, instead of one, non-harmful plant species resulted in a decrease in MG densities in the olfactory lip.

View Article: PubMed Central - PubMed

Affiliation: Department of Behavioral Physiology and Sociobiology, Biozentrum, University of Würzburg Würzburg, Germany.

ABSTRACT
Long-term behavioral changes related to learning and experience have been shown to be associated with structural remodeling in the brain. Leaf-cutting ants learn to avoid previously preferred plants after they have proved harmful for their symbiotic fungus, a process that involves long-term olfactory memory. We studied the dynamics of brain microarchitectural changes after long-term olfactory memory formation following avoidance learning in Acromyrmex ambiguus. After performing experiments to control for possible neuronal changes related to age and body size, we quantified synaptic complexes (microglomeruli, MG) in olfactory regions of the mushroom bodies (MBs) at different times after learning. Long-term avoidance memory formation was associated with a transient change in MG densities. Two days after learning, MG density was higher than before learning. At days 4 and 15 after learning-when ants still showed plant avoidance-MG densities had decreased to the initial state. The structural reorganization of MG triggered by long-term avoidance memory formation clearly differed from changes promoted by pure exposure to and collection of novel plants with distinct odors. Sensory exposure by the simultaneous collection of several, instead of one, non-harmful plant species resulted in a decrease in MG densities in the olfactory lip. We hypothesize that while sensory exposure leads to MG pruning in the MB olfactory lip, the formation of long-term avoidance memory involves an initial growth of new MG followed by subsequent pruning.

No MeSH data available.


Related in: MedlinePlus