Monthly Archives: November 2018

Week 12.11 – 18.11

This week started with the weekly quizz. This time it was the turn for the Wiring the Brain chapter in the book, where we could learn about how the brain comes to be what it is in its adult stage. From its synapses to its macroscopical structure, what lies behind the genesis of our most important organ ? That’s what we attempted to understand in this lecture.

We started by going through all the precursor cells and the paths and transformations they go through to achieve their final destination and structure. Soon enough, we concluded how the brain grows inside out, just like one of the questions on the quiz wondered on. It is said so precisely because the neutrons migrate from the inner part of the cortex to more superficial cortical layers, past already formed ones. We went through how each neuron grows until it reaches its target cell, aided by either chemoattractors or chemorepulsors.

Specifically in this topic it was very interesting to understand how scientists got their hands on this kind of information and perfected their theories throughout the years. Most studies were obviously made on animals, namely mice and frogs. This made me wonder a bit about animal experimenting. Of course most of neuroscience is based on it, and the authors of the book for this course do provide a good justification for its use in one of the initial chapters of the book. But how far can we go in the name of science ? Maybe for now that we know so little about the mysterious workings of our brain we are not comfortable experimenting with humans yet. But hopefully at some point we will be able to leave animal experimenting in the past and move to other methods of researching.

Synaptic rearrangement and elimination were extensively discussed along with the mechanisms behind ocular dominance shift or at least the theories surrounding it. It was widely interesting to finally learn that critical periods for human capacity plasticity really is a real studied and confirmed thing instead of simply a theory we tell ourselves to excuse our less capable selfs of learning new things as we grow older. Certainly a lot of research is still to be done in those fields.

The following day we went on our second excursion on this course. This one sparked our interest and curiosity much more than the first one we must say. This excursion was to the sooma medical company. None of us knew anything about it so we went with o expectations.

Our first impression was quite positive since the atmosphere of the company is super modern and has a little scent of innovation in the air. Was we sat down, one member of the company promptly introduced us to their main activities and devices. The product they offer is tDCS self-neurostimulator. They have been developing it and testing it for a few years now and have gotten groundbreaking results. The main advantage is that it is very easy to self administer, there is simply one button on it. It also has automated safety features to ensure the patient’s comfort.

So far they are only making it available for medical professionals instead of providing treatment themselves. It supports double-blind condition and can be configured for multiple study protocols.

Sooma is in fact the world leader in home-based neuromodulation at the moment. In the studies they carried out, the majority of patients experienced a marked improvement as a result of the Sooma Depression Therapy. The average improvement rate was 49%. This is quite impressive comparing to other existent solutions for depression. More specifically, 86% of the patients achieved partial response, the response rate was 59%, and the remission rate was 18%. This sounded very promising. Let’s see how this values evolve as it is increasingly used.

Depression is unfortunately an issue very much worth debating given its high prevalence in nowadays population, specially in younger age groups. If this turns out to be a reliable method, even to add to the already used ones including medication, it could make a difference in a lot of lives for the better and that should really always be researchers main aim at every point.

Week 05.11 – 11.11

This week we discussed about the Motor System – which are chapter 13 (Spinal Control of Movement) and 14 (Brain Control of Movement) of the book Neurocience: Exploring the Brain. Not without going back to chapter 10 (The Central Visual System) to explain something that had been left unsaid.

The motor system consists of all our muscles and the neurons that control them. The spinal cord contains specific motor “programs” for generating coordinated movements, being these programs accessed, executed and modified by descending commands from the brain. Motor control can be divided in two parts: the spinal cord’s command and control of coordinated muscle contractions and the brain’s command and control of the motor programs in the spinal cord.

The cells of skeletal muscle – which constitutes the bulk of the muscle mass of the body and function to move bones around joints, for example –, muscle fibers, are each innervated by a single axon. The ventral horn of the spinal cord contains lower motor neurons, that innervate these skeletal muscle fibers, and which are divided into two categories: alpha motor neurons and gamma motor neurons. The first ones trigger, directly, the generation of force by muscles. Muscle contraction results from the individual and combined action of motor units – which are an alpha motor neuron and all the muscle fibers it innervates.

If alpha motor neurons excite skeletal muscles, we need to understand what regulates motor neurons in order to understand the control of muscles. An interesting experiment to understand more about the innervation and the types of motor units (slow and fast) is one where you force slow motor units to innervate a fast muscle. What happens to the muscle? It will switch to assume slow properties; the types of proteins expressed by the muscle were altered by the new innervation.

The spinal cord contains an intricate network of circuits for the control of movement; it is far more than just a conduit for somatic sensory and motor information.

In this part of the lecture, we learned about movement and its spinal control from different points of view (biochemistry, genetics, biophysics, behaviour, etc.). And this knowledge, derived from every approach, made us achieve the most complete understanding of the topic, leaving us still with some questions that should be answered in the next part of the lecture.

How does the brain influence the activity of the spinal cord? First, it communicates with the spinal cord through axons that descend from the brain along two major groups of pathways: lateral pathways (2 tracts) – controlling voluntary movements of the distal musculature – and ventromedial pathways (4 tracts) – controlling postural muscles.

Several experiments were made on monkeys to prove the relation with the pathways and muscles, among other things. Next, this week we leave an interesting note on behavioural neurophysiology, taken from the book that we are following in this course.

Bear, Connors, Paradiso: Neuroscience: Exploring the Brain, 4th edition, Lippincott, Williams & Wilkins, 2015, 495.

Week 29.10 – 04.11

Lecture 29.10

The topic of this week lecture was the human auditory system and the vestibular system. The systems have different functions, one is to hear the sounds surrounding and the other is to be able to keep balance. Their respective functions are not the same but yet some similarities can be found in their mechanism.

First, we explored the structure of the human’s ear. It is composed of three parts: the outer ear, the middle ear and the inner ear. Each part has some unique features and characteristics. The pinna and the auditory canal form the outer ear, their task is to collect the sounds from the surrounding environment and lead them into the ear so that they can be analyzed. We learned later on that the structure of the pinna plays an important role in the evaluation of the location of a sound in the vertical plane. The shape allows the ear to receive two different sounds, a direct and a reflected one.

Then the middle ear, composed of the ossicles and the tympanic membrane, was studied. It is quiet impressive to think that these very little bones can totally change the way we hear and that they are a necessity in the human ear.  They have two major roles to play. The first is to amplify the sound force up to 20-fold amplification. The second is the attenuation reflex; it is a system that includes the contraction of muscles attached to the ossicles in case of a loud noise. This provides the human ear with a good protection against loud sounds that could damage the inner ear. The two roles combine to provide a great capability to the human’s ear.

Finally the inner ear, the cochlea, was inspected. It is a very important step in the auditory pathway. In the cochlea, the sounds signals are analyzed with the help of the hair cells. A quiet complex system of potassium pumps allows determining the movement of the basilar membrane, which characterize the sounds. The informations collected are then send to neurons to be translated.

The experiment described in the lecture shows that there is a relation between the nature of the sounds and the location they are processed in the brain. It is interesting because it shows that we already have an idea of the sounds before actually analyzing it. It allows the neurons to be more specific and therefore to ear better.