Alma mía


Alma mía sola, siempre sola
Sin que nadie comprenda tu sufrimiento
Tu horrible padecer
Fingiendo una existencia siempre llena
De dicha y de placer
De dicha y de placer
Si yo encontrara un alma como la mía
Cuantas cosas secretas le contaría
Un alma que al mirarme, sin decir nada
Me lo dijese todo con la mirada
Un alma que embriagase con suave aliento
Que al besarme sintiera lo que yo siento
Y a veces me pregunto qué pasaría
Si yo encontrara un alma como la mía
Un alma que al mirarme, sin decir nada
Me lo dijese todo con la mirada
Un alma que embriagase con suave aliento
Que al besarme sintiera lo que yo siento
Y a veces me pregunto qué pasaría
Si yo encontrara un alma
Si yo encontrara un alma como la mía, oh oh
Compositor: Maria Grever
Intérprete:    Natalia Lafourcade

Neurogenesis, the endless puzzle of neuroscience.

When I was a child, my grandma used to tell me that I shouldn’t hit my head when playing because I would kill my neurons and, she would add, we are born with all the neurons that we need. No more neurons are produced as we get older.

Fifteen years later, in my introductory neuroscience course, we learned about the concept of neurogenesis. Neurogenesis is the process of generating new neurons. We learned about the research that challenged the major dogma in neuroscience: no new neurons are produced in the adult brain. This dogma was held by three main factors:

  1. Clinical evidence: adult patients suffering from brain injury do not easily recover.
  2. Networks: how can newborn neurons integrate into the already existing networks of the brain? How can neurons integrate without disturbing the already established information in our brain?
  3. Stem-cells: the importance of pluripotent cells (cells that can differentiate into many other types of cells) had not been recognized yet.


Fernando Nottebohm, an Argentinian neuroscientist working at Rockefeller University, is considered as the first one who provided definitive evidence that there are newborn neurons in the adult vertebrate brain. Since then, scientists have used similar methods to study neurogenesis.  The basic principle is that, because all cells come from other cells and any cell going through division needs to make a copy of its DNA, we can use an analog of thymidine to identify newborn cells. You can think of thymidine as a lego piece that is incorporated into the DNA of replicating cells. Cells can’t differentiate between real thymidine and thymidine analogs (e.g., BrdU), so they incorporate this thymidine analog,  which we can later visualize using antibodies. An important note is that BrdU and any other thymidine analogs allow us to make conclusions about newborn cells, but they do not say anything about the type of cell they are.

In order to identify newborn neurons, scientists add a second type of labeling for neural markers. Mature neurons express proteins that make them neurons instead of, for example, skin cells or glial cells (also found in the brain). Some of these markers are NeuN and calbindin. Therefore, if we find neurons in brain tissue labeled for both BrdU and a neural marker, we can conclude that these are newborn neurons!

Neurogenesis in the adult human hippocampus was first reported by Eriksson and colleagues back in 1998. In their experiment, they studied brain samples from patients who died from cancer and who were previously injected with BrdU (to keep track of their tumor growth). They found newborn cells that expressed neural markers in the hippocampus, a brain region involved in learning and memory.

Last week, however, Sorrells and colleagues reported that “Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults”. In the NPR, they released a podcast called “Sorry, Adults, No New Neurons For Your Aging Brains”. Apparently, we are back to adopting my grandma’s thinking, but after reading the paper, I ended up believing Professor Beltz’s explanation. She studies neurogenesis in crayfish and they discovered that the immune system provides the neural precursors needed to have neurogenesis. In Sorells and colleagues’ paper, they were actually looking at the neural precursors, not at the newborn neurons (at least in the experiment with humans). They couldn’t find a “defined population of progenitor cells […] in the subgranular zone [a region in the hippocampus] during human fetal or postnatal development”. Therefore, they concluded that neurogenesis is not happening in the adult brain because there are not neural precursors in the brain.

However, as Professor Beltz proposes, there might be an extrinsic source of neural precursors: the immune system. Some experiments studying women who received a bone marrow transplant from men support this hypothesis because Y-chromosome-containing neurons were found in their brain! Of course, there are people who think that these results might come from a problem with a leaky brain blood barrier of patients (the brain blood barrier protects the brain and does not let in many extrinsic cells/molecules). Others believe that the neural proteins found in these cells are the product of fusion instead of being produced by transdifferentiation (going from a type of cell to another one). Transdifferentiation is a conflictive idea because neural tissue emerges from a type of tissue (ectoderm) that is different from the tissue that produces cells from the immune system (mesoderm).

I am starting to get very technical and it’s 1:28 am, so I just want to finish this by saying that we might still live in dogma. There are tons of papers out there showing that neurogenesis occurs and that we might be looking at the wrong place looking for the wrong thing because we won’t change the dogma in science. Cells from the immune system might be the precursors of neurons in our brain!


Tormento mío

Desde que te marchaste,
toda sonrisa es un esbozo
todo recuerdo es un martirio
todo deseo es un capricho.

Desde que me fui,
algo mío se perdió,
algo tuyo se encontró,
algo nuestro se fugó.

Éramos uno.
Ahora somos ninguno.

El sueño eterno no llega
Y sigues siendo fantasía
O quizá una pesadilla.

Duerme tranquilo,
Pues me conformo
Con ser un fantasma.

Tan tuyo
Como tú eres mío.
Tormento mío.

A commentary on Bach speaks: a cortical “language-network” serves the processing of music.

From Course 9.71

A commentary on Bach speaks: a cortical “language-network” serves the processing of music.

Koelsch and colleagues (2002), aimed to investigate the neural correlates of music in this paper. Particularly, they wanted to test whether the cortical network comprising music processing overlaps with the regions involved in language processing. They stated that some temporal and frontal single areas related to language had been found to be involved in music processing, but only for “one-part stimuli” (melodies). The network comprising the areas of both Broca and Wernicke had not been found to be related to music processing yet. Koelsch and colleagues speculated that the use of one-part stimuli in previous experiments was the reason why these areas were not shown to be active in music processing. Therefore, they decided to use multipart stimuli (chords) in a fMRI study to investigate the neural correlates of music with respect to the known “language network” in the human brain.

Koelsch et al (2002) designed four experimental conditions using chord-sequences: in key, clusters, modulations, and deviant instruments. They based their conditions on the principles of Western tonal music (major-minor tonal system). Therefore, the in-key condition was simply a sequence of chords in a major key, the cluster condition was a dissonant tone-cluster, the modulation condition was a sequence of chords in the minor key, and the deviant instruments were major chords played by an instrument other than piano. The subjects, ten non-musicians, were instructed to detect deviant instruments and clusters by pressing a right button when no cluster had occurred since the last response and by pressing a left button for deviant instruments. The researchers designed the experiment in this way to focus the attention of the participants on the tone and the harmonic aspects of the stimuli. In addition, no motor response was present in the detection of clusters and the task-irrelevant modulations were investigated as well.

The analysis of the fMRI-data in this study revealed that the clusters, deviant instruments, and modulations activated a very similar broad neuronal network when compared to in-key blocks. The authors discussed that the regions in this cortical network are also well known to be involved in the processing of language. This result, in combination with some previous studies, led Koelsch and colleagues to conclude that the cortical language network was less domain-specific as previously believed.

The first shortcoming that I noticed in this conclusion is that assuming a correct fMRI-data analysis, there is not enough evidence to say that this “neural activation overlap” means that both language and music processing share the same network. For instance, two physically distinguishable networks of neurons could be spread across very similar regions in the brain without necessarily being the same ensemble. Alternatively, there could be neurons acting as integration centers in these regions for both language and music networks. However, this does not mean that the language network serves to process music.

Moreover, even when the idea of having one network for music and language processing seems reasonable in terms of a system for acoustical analysis of tones, their explanation of musical semantics for the activation of Wernicke’s area in cluster, modulating, and deviant-instrument sequences seems weak. This is because the fluctuations of chords and instruments do not have a predetermined meaning as signifiers in a language do. Similarly, Koelsch and colleagues concluded that the activation of BA 44 was a result of the syntactic processing of dissonant and minor chords. It is true that there are rules in the construction of melodies in western music, but deviant instruments also elicited areas of music-syntactic processing, which makes this a weak argument as well.

With respect to the group analysis of the fMRI data, a one-sample t-test across the contrast images of all subjects was performed. The problem in this type of analysis is that averaging across participants, whose anatomy is not exactly the same, blurs brain activations and can generate a false overlap of closely adjacent responses that do not actually overlap. A better approach, in this case, would be the determination of regions of interest in each individual and then comparing the brains of the subjects. Furthermore, a multi-voxel pattern analysis would be helpful to identify the arrangements of neural activation for language and music in overlapping regions, supporting the idea that there are distinct or similar networks for these two domains.

Another weakness of the analysis in this study is that they did not obtain their own comparative data for language. I think that they should have included tasks analogous to syntax and semantics in language, which is what they were trying to test in music processing, even if such comparisons are debatable. Finally, I think that it would have been better to test their hypothesis of shared networks for music and language by developing an easier task. For instance, the speech-to-song illusion would have been a good start because the stimulus is the same, but the perception changes over time. This task could have also prevented differences in neural response driven by acoustic differences, as it is the case in many of these music-speech studies.



Koelsch, S., Gunter, T.C., v Cramon, D.Y., Zysset, S., Lohmann, G., and Friederici, A.D. (2002). Bach speaks: a cortical “language-network” serves the processing of music. Neuroimage 17, 956-966.

Peretz, I., Vuvan, D., Lagrois, M.E., and Armony, J.L. (2015). Neural overlap in processing music and speech. Philos Trans R Soc Lond B Biol Sci 370, 20140090.

Tierney, A., Dick, F., Deutsch, D., and Sereno, M. (2013). Speech versus song: multiple pitch-sensitive areas revealed by a naturally occurring musical illusion. Cereb Cortex 23, 249-254.


The right to stay at Home. Why am I against immigration to America?

The following article is my opinion. I do not endorse violence or discrimination against immigrants, but I rather support a movement of integration and improvement of global communities that will allow people to have a good life where they were born and raised. Humans should have the right to live a good life in their respective countries!


Every time I voice my opinion against the phenomenon of immigration to America, people think I am some sort of intolerant conservative or that I simply lack fundamental moral values (e.g., compassion or respect for others’ freedom). If you knew me at a personal level, you might even think that I am a hypocrite because more than one of my family members has permanently moved to America. You might even argue that I have spent a quarter of my life studying in the States and that I have no right to oppose anyone coming to this country. From my perspective, all of these points just further support my conviction, so please, let me explain to you why I think the way I think about this issue.

Essentially, I am against immigration to the United States of America because, in most cases (including my family situation), immigration occurs out of need. Nowadays, people move to America not exactly because of the American dream, but rather because of the world’s nightmare: war, poverty, insecurity, persecution, lack of infrastructure (universities/education, hospitals/healthcare), and the list goes on and on. My question is, why can’t we offer a good life to people where they are at? Why do they have to move? Why can’t we help them improve their countries instead of taking their human capital to America? Why can’t I study a PhD in systems neuroscience in my local university? Why can’t my mother receive medical treatment at our local hospital? From the Guatemalan man who works in the cafeteria to the Iranian professor at MIT, why can’t we all make our dreams come true in our respective countries?

If I told Americans that they have to move to Switzerland in order to educate themselves, to have an adequate healthcare, to feel safe. If I told them that the only place where they can have a good pay, their dream house, and their dream job is somewhere across the Atlantic, they would think I am crazy. But this is a reality for many people in the world! Do you want a good education? Go to America/Europe/a more developed country! Do you want money/comfort? Go to America/Europe/a more developed country! Do you want to get an acceptable treatment for  X strange disease? Go to America (and you better have money to pay for it)! Do you want to feel safe compared to the violence you have experienced before? Go to America! Are you gay but homosexuality is a crime in your country? Go to America!

Alas, this is the prerogative of the developed world.

But I don’t agree.

Immigration to the developed world is nothing but unsustainable assistencialism. We don’t teach people how to fish, but we rather throw some fish to a few of them while there are many left with hunger, desperation, anger, and pain. I won’t be part of this vicious cycle. I came here to learn how to fish. That’s it. I don’t want your money, your comfort, your glory. I’ll be back home soon and I’ll teach my people how to fish. If they want to go, if they want to explore the world, that is fine. But they should always have the option (and hopefully the desire) of coming back. This is their home and they have the right to stay home.