Author Archives: Sydney Dennis

There is Peace in Harmony

Maybe you can’t stop listening to the pop-harmonies of Taylor Swift or perhaps you find yourself enjoying the elusive “up-and-coming” SoundCloud rappers. Regardless, even with these dissimilarities, we can all agree on the fact that some chords sound ‘good’ and others notes brawl when they’re played at the same time outlining the idea of consonance versus dissonance.

Figure 1. (A) represents a consonant interval while (B) represents one of dissonance. Solid lines indicate the frequency components of the root note; dotted lines represent the frequency components of the interval note.

Music is a universal human phenomenon. An understanding of the underlying auditory processing concerned with listening to music may unravel which musical parameters are innate in our biology. Behavioral studies have shown that listeners prefer consonant intervals and assign them a higher status in hierarchical rankings (Plomp and Levelt, 1965). It is this hierarchical organization of pitch that contributes to the sense of a musical key and pitch structure in Western music (Rameau, 1722).

In any case, the question remains: why is it that we prefer consonance over dissonance? Bones et al. (2014) hypothesized that the perception of consonance can be accounted for by the neural representation of harmonicity (the closeness of fit of two notes). To test their hypothesis, participants were presented with dyads (two-note chords) made up of a lower note (the ‘root’) and a higher note (the ‘interval’) and asked to rate them on their pleasantness or unpleasantness.

To test the effects of interactions within the cochlea, researchers also measured the electrophysiological frequency following response (FFR). FFRs are neural signals generated in the brain when people hear sounds as measured by frequency components. FFRs were recorded in two scenarios: when each dyad was presented to both ears (diotic) or one note assigned to each ear (dichotic). To measure the strength of the representation of harmonicity, a neural consonance index (NCI) was calculated giving a quantitative look into how consonant a dyad is

Figure 2. Schematic of dichotic vs. diotic listening tasks.

The results of this study establish that average dyad pleasantness ratings are consistent with prior studies in that consonant dyads were more pleasant over dissonant dyads (Bidelman and Krishnan, 2009; McDermott et al., 2010). Consonance preference for differing intervals was found to have a close correspondence to the neural representation of harmonicity as reflected in the FFR. Additionally, when the dyads were presented to both ears, the perception of consonance was higher than when the two notes were presented to separate ears. The FFR showed a stronger representation of harmonicity in the diotic scenario and interactions between the harmonics of the two notes on the basilar membrane of the cochlea resulted in further frequency components being present in the FFR. Therefore, a diotic scenario enhances the consonance of a sound. Overall, the research suggests that a preference for consonance depends both in part by the neural representation of harmonics as well as their cochlear interactions.

One weakness of this study is its specificity to Western music. In a study of Tsimane’s – a native Amazonian society – in comparison to Western culture found that cultures sufficiently isolated from Western music are devoid of consonance preference (McDermott, 2016). Thus, it is unlikely that there is an innate bias toward harmonic sounds (McDermott, 2016). However, there are conflicting studies regarding infants’ ability to show preference for consonant sounds (Trainor, 2002) that suggest that it is indeed innate. There is no conclusion in Bones et al. (2014) regarding the innateness of consonance preference. The confliction of these studies leads to confusion in their conclusions.

In general, this study provided great insight into the neural components of what makes consonance sound so right. Though we may not be able to figure out if this is innate or learned, it can at least be agreed upon that Westerns find more peace in harmony.



Bidelman GM, Krishnan A (2009) Neural correlates of consonance, dissonance, and the hierarchy of musical pitch in the human brainstem. Journal of Neuroscience 29(42):13165-13171. doi: 10.1523/JNEUROSCI.3900-09.2009 

Bones O, Hopkins K, Krishnan A, Plack CJ (2014) Phase locked neural activity in the human brainstem predicts preference for musical consonance. Neuropsychologia 59:23-32. doi: 10.1016/j.neuropsychologia.2014.03.011

McDermott JH, Hauser MD (3005) The origins of music: Innateness, uniqueness, and evolution. Music Perception 23(1):29-59. doi: 10.1525/mp.2005.23.1.29

McDermott JH, Schultz AF, Undurraga EA, Godoy RA (2016) Indifference to dissonance in native Amazonians reveals cultural variation in music perception. Nature 535:547-550. doi: 10.1038/nature18635

Rameau JP (1722) Treatise on harmony. Reprint. New York: Dover, 1971

Plomp R, Levelt WJM (1965) Tonal consonance and critical bandwidth. Journal of the Acoustical Society of America 38:548-560. doi: 10.1121/1.1909741

Trainor LJ, Tsang CD, Cheung VHW (2002) Preference for Sensory Consonance in 2- and 4-Month-Old Infants. Music Perception 20(2):187-194. doi: 10.1525/mp.2002.20.2.187


Figure 1: Bones O, Hopkins K, Krishnan A, Plack CJ (2014) Phase locked neural activity in the human brainstem predicts preference for musical consonance. Neuropsychologia 59:23-32. doi: 10.1016/j.neuropsychologia.2014.03.011

Figure 2 Girl: (

Figure 2 Music notes: (

Just by Looking at It, I Think It’s a Red

Everybody knows that one wine enthusiast that insists you must let the wine ‘breathe’ and exclaims “Ah, we have some truly wide legs on show here! What a treat!”, in response to the swirl of their glass.

Famous for being the city to where Popes fled following the corruption of Rome in the 14th century, Avignon should also be celebrated for its location in the South of France, a region famous for its wine. Though its sanctity should not be understated, its wine must not be either.

Figure 1. Me and two friends at the Carré du Palais wine tasting.

After walking into the refurbished bank vault at the Carré du Palais, the crisp, cool air hit my skin like the droplets of a bright Sauvignon Blanc with notes of Asian pear and celery. As we all took our places, there were 2 clear wine glasses and 1 small black wine glass that, in my blatant naïvety, I thought was for water. After integrating the sommelier for most of the wine tasting’s duration, he informed me that, in fact, the 1 small black wine glass was for white wine. He stated that our perceived taste of the wine can be influenced by the color because, as everyone knows, a deep yellow is probably an aged Riesling and a deep gold is probably a Chardonnay. This is referred to as ‘crossmodal bias’ (Verhagen and Engelen, 2006), a phenomenon in which one sensory modality (vision) can influence another (taste).

Figure 2. The two clear wine glasses and smaller black wine glass that caused confusion.

I thought this was a very fascinating precaution to take. To investigate the relationship between taste and vision, Rolls and Baylis (1994) recorded singular neurons from five macaques. Food related visual stimuli was presented to macaques and directly after, five different taste stimuli were delivered intraorally. It was found that 29.7% of neurons in the primary taste cortex were bimodal; they were found to have visual responses as well as olfactory responses (Rolls and Baylis, 1994). This discovery exhibits the ability of these sensory modalities to ‘communicate’ early on and can help us understand the phenomenon of crossmodal bias.

The sommelier also made a point to smell the wine deeply before taking his first sip. Following in his footsteps, I tried it. Though I didn’t pick up the hints of black current that he was noting, I did get a sense for the taste that was to come. In 1963, Thompson et al. suggested that sensory information entered its appropriate primary cortex brain region and then, through higher order processing, converged with other sensory modalities to create a more cohesive cognitive stimulus (Thompson et al., 1963). More recent discoveries suggest that the sensory modalities converge much sooner than this (Small et al., 2013). The piriform cortex, a structure within the primary olfactory cortex known to encode for odor memories (Meissner-Bernard et al., 2019), was found to contain neurons that selectively respond to taste (Small et al., 2013). Single neurons in the primary olfactory cortex of 19 rats were found to respond to taste solutions to the tongue (Small et al., 2013). This suggests that there is direct communication between sensory systems. That is, crossmodal bias occurs through exchanges of information between primary sensory systems.

Figure 3. Earlier models suggested a convergence pathway similar to (A) but findings from Small et al. (2013) suggest a schematic more like (B).

Immediately after telling my boyfriend about my cathartic wine tasting, he pronounced that sommeliers are simply full of it. In fact, in a study done by Castriota-Scanderbeg et al. (2005) investigating the differences between sommeliers and naïve research subjects, it was found that sommeliers actually have more refined olfactory and taste perception sensitivity (Castriota-Scanderbeg et al., 2005). 7 male sommeliers and 7 males with no wine tasting training were given either wine or glucose and a subsequent functional magnetic resonance imaging (fMRI) was performed. The left insula, orbit-frontal cortex, and bilateral dorsolateral prefrontal cortex were significantly more involved in wine tasting of sommeliers in comparison to naïve subjects (Castriota-Scanderbeg et al., 2005). Modulated by expertise, these regions represent areas where taste and olfactory stimuli converge and therefore give rise to the representation of flavor (Castriota-Scanderbeg et al., 2005). Moreover, in comparison to glucose, the wine elicited a neural response after the initial taste period which the researchers attribute to the presence of olfactory stimulus (Castriota-Scanderbeg et al., 2005) giving more evidence to the influence of smell on taste.

Over the past 50 years, the well-established organization of sensory systems has been dissolved through discoveries of sensory-sensory connectivity and the influences of one sensory modality on another. So, next time you uncork a nice bottle of wine, or dare I say, screw the top of your $3 bottle, recognize the convergence of your senses.



Baylis LL, Rolls ET (1994) Gustatory, olfactory, and visual convergence within the primate orbitofrontal cortex. Journal of Neuroscience 14(9):5437-5452. doi: 10.1523/JNEUROSCI.14-09-05437.1994

Castriota-Scanderbeg A, Hagberg GE, Cerasa A, Committeri G, Galati G, Patria F, Pitzalis S, Caltagirone C, Frackowiak R (2005) The appreciation of wine by sommeliers: a functional magnetic resonance study of sensory integration. NeuroImage 25(2):570-578. doi: 10.1016/j.neuroimage.2004.11.045

Rolls ET, Deco G (2002) Computational neuroscience of vision. Oxford University Press, Oxford (2002)

Small DM, Veldhuizen MG, Green B (2013) Sensory neuroscience: taste responses in primary olfactory cortex. Current Biology 23(4): R157-R159. doi: 10.1016/j.cub.2012.12.036

Thompson RF, Johnson RH, Hoopes JJ (1963) Organization of auditory, somatic sensory, and visual projection to association fields of cerebral cortex in the cat. Journal of Neurophysiology 26(3): 43-364. doi: 10.1152/jn.1963.26.3.343

Verhagen JV, Engelen L (2006) The neurocognitive bases of human multimodal food perception: sensory integration. Neuroscience and Biobehavioral Reviews 30(5):613-650. doi: 10.1016/j.neubiorev.2005.11.003


Figure 1 and 2 were taken by me

Figure 3: Small DM, Veldhuizen MG, Green B (2013) Sensory neuroscience: taste responses in primary olfactory cortex. Current Biology 23(4): R157-R159. doi: 10.1016/j.cub.2012.12.036


Are you sure the sky is blue?

The dreaded question by every parent – “why is the sky blue??”. It is a long-standing fact that the sky is classified as blue, but when it is put into question, this idea that has been so deeply ingrained in our brains begins to falter. Depending on so many factors, the sky can be garnished by so many other colors. This is especially true in terms of artwork and the abstraction that accompanies it. The constructs that we have grown up in have assigned very concrete terms to very abstract objects – without this, how would we begin to explain the color blue?

A Parisian sunset of orange, pink, purple, and lastly, blue.

As Norris notes in her review of Color in the Age of Impressionism (2019), artists such as Degas, Renoir, and Monet encouraged the use of brighter color palettes. Color became abstracted and independent – autonomized in a sense. This created a world in which color and object were not always married in comparison to those in the natural world…this became especially true in post-impressionism. Artists such as Van Gogh, Seurat, Cézanne, and Gauguin truly divorced color from form. In this case, the sky could be painted green but the context of the painting would still allow your mind to label it as the ‘sky’.

A Parisian rainstorm causing the sky to turn completely grey.

These painters began to venture into a more abstruse realm of color. Object-associated color is implicated in the left fusiform gyrus in the posterior temporal cortex; near here is also where color is perceived (Simmons et al., 2007). Through an fMRI study performed by the discussed paper, it was found that color knowledge is also stored in this area lending evidence to the theory that knowledge is contained in modality-specific brain regions (Simmons et al., 2007). In this case, color knowledge is stored where object recognition takes place. By this token, recognition of the sky in a painting stimulates both color knowledge and object-associated color simultaneously. This can be occasionally problematic when object-associated color does not match with color knowledge.

One of Monet’s many Water Lilies paintings that shows extreme abstraction of color where the ‘sky’ is magenta.

However, memory is also involved in the perception of color as it’s inherently involved in most everything we do (Hansen et al., 2006). These researchers asked participants to tweak the color of fruits until they appeared to be grey; this was typically when the grey point was manipulated to that of opposite the fruit’s natural color (Hansen et al., 2006). This demonstrates that perception of color is heavily regulated by visual memory. Seeing the sky as blue during a particularly beautiful day is not rare, it has been consolidated as a memory in the brain. Perceiving the sky as blue in a painting, therefore, is easy. Yet, a lime green sky is an incompatible scene to imagine. Therefore, the brain must use unconsciously use the surrounding context clues to fill in the gaps. Though we may not notice this, it is happening constantly within our minds to fill in small gaps within our world that may not make logical sense.

The Sower by Vincent van Gogh, November 1888 adorning a green sky.

The general question, “what color is the sky?” opened a can of worms in the visual perception of color from an artistic viewpoint. As I explore Paris and learn of all its history and artwork, many of the paintings request a second longer to interpret. This was true especially for paintings from the post-impressionism movement as seen at the Musée d’Orsay. The uncoupling of objects from their natural color removes the ability of memory archives to be used contributing to the beauty and allure of these paintings.


Hansen T, Olkkonen M, Walter S, Gegenfurtner KR (2006) Memory modulates color appearance. Nature Neuroscience 9:1367-1368. doi: 10.1038/nm17

Pope N (2019) Color in the age of impressionism: commerce, technology, and art by laura anne kalba (review). Technology and Culture 60(1):330-33. doi: 10.1353/tech.2019.0018

Simmons WK, Ramjee V, Beauchamp MS, McRae K, Martin A, Barsalou LW (2007) A common neural substrate for perceiving and knowing about color. Neuropsychologia 45(12):2802-2810. doi: 10.1016/j.neuropsychologia.2007.05.002

Van Gogh V. (1888) The Sower. [Painting]. Retrieved from

my bubble has been popped

It’s 9 AM – rush hour on the metro. The platform is packed and the people of France know very little regarding personal space. As the offensive warning of door closure sounds, it’s as if the lid to a tightly packed sardine tin is being jammed shut. Looking around, the only person that might give you a smile is the baby in the stroller, the rest adorn deadpan expressions, chatter is low, and the screech of the metro rings through my ears. As a man stands on my foot and the hair of the woman in front of me grazes across my lips, the words “excusez-moi” or “pardon” fail to be uttered. It is a way of life and, honestly, I was probably in the way.

A typical platform of the RER after a full ride.

This unapologetic lack of personal space can be attributed to the amygdala based on an fMRI study done by Kennedy et al. (2009). A bilateral lesion of the amygdala resulted in very little regard to personal space. The amygdala plays a role in strong emotional responses and in this case, in regards to the proximity to others. In this experiment, a patient with bilateral lesions of the amygdala felt comfortable with an individual at a significantly closer distance than a healthy individual reported. Given my experience on the metro, I predict that my amygdala activity was quite high.

In another study done by Graziano and Cooke (2006), it was found that the ventral intraparietal area (VIP) and a polysensory zone in the precentral gyrus (PZ) both respond to objects that are touching or looming toward the body’s surface. These areas give rise to the ‘personal space bubble’ that most of us cherish in the United States. In fact, stimulation of these areas can result in defensive behavior such as avoidance or blocking maneuvers (Graziano and Cooke, 2006). My New Englander mentality reports that a quick elbow nudge or jerk of my foot from beneath my fellow passenger’s may send the message of my discontent but, apparently not.

In a different context, in a study of Borderline Personality Disorder patients, amygdala and parietal cortex activation of patients was lower than baseline when in close proximity to others (Schienle et al., 2015). Invasion into the subject’s ‘personal bubble’ was simulated by zooming in on pictures of facial expressions. Borderline Personality Disorder patients only showed increased activation in these areas if the facial expression showed disgust. Otherwise, there was very little concern with a lack of personal space in comparison to the control patients.

An average metro ride.

Perhaps the French have evolved to have lower activation in the amygdala and parietal cortex? Just food for thought. Either way, I know that I’m certainly not used to it and for about 35 minutes on the metro (and many other places) I feel like my bubble has been popped. Everything and everyone is about 5 inches closer to my body than it should be…but maybe my amygdala and parietal cortex will adapt as the weeks go on!



Graziano MSA, Cooke DF (2006) Parieto-frontal interactions, personal space, and defensive behavior. Neuropsychologia 44: 845-859. doi: 10.1016/j.neuropsychologia.2005.09.009

Kennedy DP, Gläscher J, Tyszka JM, Adolphs R (2009) Personal space regulation by the human amygdala. Nature Neuroscience 12: 1226-1227. doi: 10.1038/nn.2381

Schienle A, Wabnegger A, Schöngassner F, Leutgeb L (2015) Effects of personal space intrusion in affective contexts: an fMRI investigation with women suffering from borderline personality disorder. Social Cognitive and Affective Neuroscience 10(10): 1424–1428. doi: 10.1093/scan/nsv034