Author Archives: umbrellabrain
Are you an extrovert or an introvert? Personality types are often lumped into one of these categories. Frequent social engagement and novelty-seeking behavior are characteristic of extroverts, whereas introverts prefer to be alone and engage in familiar activities. The differences in brain chemistry that cause these personality traits arise from both ‘nurture’ or individual experiences, and ‘nature’ or genetic predisposition. But which one is more important? This is a classic theme in neuroscience that I will not fully explore here; but new evidence from honey bees scores another point for team nature.
A recent article1 published in Science by Liang et al. investigates the molecular basis for novelty-seeking behavior in the honey bee, Apis mellifera. The authors seek to understand how individual differences in gene expression lead to behavioral variation. They explain that 5-25% of bees within a population continually seek new food sources, even when there is no food shortage. Other individuals stick to the hive and only venture to new sites after the pioneers or “scouts” have told them the way. But how do bees communicate?
Unlike ants or termites, bees can’t leave a trail of pheromones for others to follow because volatile chemicals like pheromones dissipate in the air. Instead honey bees have come up with a creative mapping strategy. They encode the location of newly found food sources within a complicated series of movements called the “waggle dance.” First discovered by Karl von Frisch in 1965, the waggle dance is only performed by scouts2.
So what determines if a bee has what it takes to be a scout? As it turns out, dance moves aren’t the only criteria.
Liang and colleagues collected honey bees that consistently displayed scouting behavior and analyzed gene expression in the brain. Several differences in neurotransmitter signaling were found between scout bees and non-scouts. For example, genes that encode receptors for glutamate, a major excitatory neurotransmitter, had increased expression levels in scouts. A direct relationship between glutamate signaling and novelty-seeking was demonstrated when bees that were given MSG (mono-sodium glutamate) showed increased scouting behavior after administration. Differential expression of DopR1, a gene encoding a subset of dopamine receptors, was also found. Blocking dopamine signaling resulted in an overall 44% decrease in scouting behavior.
The authors point out that both glutamate and dopamine are known to be involved in novelty-seeking behaviors among many vertebrates. Interestingly, DopR1 is known to be involved in drug-seeking behavior in humans3. Although the brain circuits involved in this behavioral dichotomy have not yet been sorted out, it is clear that a similar pattern of gene expression is involved in what I like to call adventurousness. Perhaps a closer analysis of the relationship between genetics and adventurous behavior in other animal models will provide a basis for identifying genetic predisposition to drug addiction or even thrill-seeking in humans.
Written By Alyssa R. Wheeler
1. Liang ZS, Nguyen T, Mattila HR, Rodriguez-Zas SL, Seeley TD, Robinson GE. Molecular determinants of scouting behavior in honey bees. Science. 2012 Mar 9;335(6073):1225-8. PubMed PMID: 22403390.
2. von Frisch K. [The “language” of bees and its utilization in agriculture. 1946]. Experientia. 1994 Apr 15;50(4):406-13. German. PubMed PMID: 8174688.
3. Le Foll B, Gallo A, Le Strat Y, Lu L, Gorwood P. Genetics of dopamine receptors and drug addiction: a comprehensive review. Behav Pharmacol. 2009 Feb;20(1):1-17. Review. PubMed PMID: 19179847.
Did you know that there is a neuron in your brain that only responds to Halle Berry? There’s also one for your best friend, and one for your grandmother! These neurons are located downstream of sensory brain areas, and recognize faces and voices of familiar individuals. They are aptly named “grandmother cells.” This is just one of many marvels that we will share with anyone seeking scientific enlightenment.
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