Dear family and friends,
Imagine a day in Paris dedicated to music – voilà, Fête de la Musique!
My friends and I decided to first explore the music scene in the Saint Michel-Notre Dame area, one of our favorite parts of Paris (see map below). As soon as we emerged from the underground metro station near the Saint Michel Fountain, we heard a lively cacophony of sounds from every direction. Immediately, my appreciation for jazz music pulled me towards a jazzy trio on Rue Serpente. After they concluded their piece, I felt compelled to keep moving and enjoying as much music as possible. Further along, at the intersection of Rue Serpente with Rue Hautefeuille, we bumped into a crowd of spectators swaying to a soft rock band and our faces instantly brightened with auditory pleasure. Earlier in the day, I felt stressed by schoolwork and my upcoming departure from Paris, but I was beginning to notably relax upon joining the musical festivities.
While I was absorbed in the drum rhythms of another music group – I even watched a dance-off between a young girl and a grown man! – I considered the ways in which music was positively impacting my mental state (see image below). But the neuroscientist in me also wondered, what happens at the neurobiological level?
After some internet research, I chose a study by Sheikhi and Saboory examining the impact of musical stimuli on the rat brain, because the study was uniquely conducted during the fetal period. Isn’t that incredible? Previous studies have identified the connection between environmental factors and prenatal development, demonstrating how sensory and motor stimuli entering the central nervous system can lead to neuroplasticity changes in neurons (Mathies et al., 2013). Neuroplasticity refers to changes in neural pathways and synapses. Specifically, stimuli can cause an increase in synaptic connections in the brain (Pirulli et al., 2013). In the fetal brain, other studies have examined the fetal response to music (Gerhardt et al., 2000). In this particular study, Sheikhi and Saboory examined neuroplasticity and neuronal cell density in the parietal cortex (see image below) of the fetal rat brain that was exposed to music as part of a prenatal model.
As part of the methodology, the researchers utilized twelve female Wistar rats (see image below) and followed ethical guidelines established by the Medical Ethics Committee of Iran. (Ethics boards encourage researchers to use the lowest number of rats and cause the least amount of pain possible!) At twelve weeks, the researchers mated the female rats and then divided pregnant rats into a control group and a musical group. Thus, each group included six pregnant rats. Twice per day, from day 2-20 of gestation, researchers exposed the musical group to classical music. However, they did not expose the control group to music. Before labor could occur on the 21st day of gestation, the researchers anesthetized the pregnant rats and collected blood samples from them. Sheikhi and Saboory removed the fetuses and randomly chose one fetus from each mother for brain dissection. Then, the researchers horizontally sliced the parietal cortex and examined the slices via an electron microscope. Returning to the blood samples collected from the pregnant rats, Sheikhi and Saboory measured corticosterone (COS) levels in each blood sample. Corticosterone refers to a hormone secreted by the adrenal cortex in rodents (see image below). COS protects against stress, in a similar way to cortisol in humans.
The adrenal cortex is the outer part of the adrenal gland.
Sheikhi and Saboory found that control rats exhibited simpler and smoother cells, while the music-treated group exhibited a more complex cell membrane and cytoplasmic organelles, which are the specialized structures inside of cells. Alternatively, the intercellular space, or the space between cells, displayed a greater density of structures in music-treated rats than in control rats. To determine the effect of prenatal music on the density of parietal cortical cells, researchers counted the number of nuclei in one electron microscope field, since each cell should theoretically have one nucleus. As expected, researchers found a greater cell density in the parietal cortex of music-treated rats than in control rats. Additionally, prenatal music helped to reduce COS blood levels in pregnant rats. Aha! I bet that a decrease in my cortisol levels is one of the reasons why I felt so relaxed during Fête de la Musique.
I believe the prenatal music model is a unique strength in study design and the findings can be related to an intra-uterine musical effect. However, I would like to offer a few of my own criticisms and suggestions for future experiments. According to the methodology, researchers only collected blood samples on the 21st day of gestation, and then claimed to see a reduction in COS blood levels. However, in order to draw comparisons, the researchers should have collected at least one other blood sample on the 1st day of gestation. Preferably, Sheikhi and Saboory should also have drawn blood from the pregnant rats at various, controlled time points throughout the experiment for stronger comparisons. In this research study, researchers exposed pregnant rats to only classical music, but I wonder if results would change with exposure to different types of music, such as jazz or soft rock. In a future experiment, Sheikhi and Saboory could also test the effect of music on rat infants immediately following birth. Additionally, the researchers only examined the fetal parietal cortex, but should examine other cortical areas as well.
Gerhardt KJ, Abrams RM (2000) The Fetus Fetal Exposures to Sound and Vibroacoustic Stimulation. Journal of Perinatology 20:S20-S29 Available at: http://www.ncbi.nlm.nih.gov/pubmed/11190697 [Accessed June 22, 2015].
Matthies U, Balog J, Lehmann K (2013) Temporally coherent visual stimuli boost ocular dominance plasticity. J Neurosci 33:11774–11778 Available at: http://www.ncbi.nlm.nih.gov/pubmed/23864666 [Accessed June 22, 2015].
Pirulli C, Fertonani A, Miniussi C (2013) The role of timing in the induction of neuromodulation in perceptual learning by transcranial electric stimulation. Brain Stimul 6:683–689 Available at: http://www.ncbi.nlm.nih.gov/pubmed/23369505 [Accessed June 22, 2015].
Sheikhi S, Ph D, Saboory E, Ph D (2015) Neuroplasticity Changes of Rat Brain by Musical Stimuli during Fetal Period. 16:448–455 [Accessed June 22, 2015].
*I photographed the rock band and drum group, and found the other images through Google Maps and Images.