Week 12

Our last week of this course contains of an exercise lab for EEG measurements in Aalto Behavioural Laboratory. Therefore the course was split into two groups with around 20 people. For the measurements of brain activities one volunteer was needed.

Like the CBRU, the Laboratory of Aalto also consists of 2 rooms. One shielded room for the measurements and another room with the displays for monitoring. The EEG cap contains in total of 34 electrodes, which includes one ground electrode and another one for reference.

The first step was the preparation of the subject. For the right choice of the EEG cap size, the circumference of the head and the distance from the forehead to the beginning of the neck was measured. After the EEG cap was placed on the subject’s head, the hair at the contact spots of the electrodes was pushed aside. Therefore a syringe filled with conductive gel was used and the conductive gel applied afterwards. This procedure was repeated until all the electrodes lit up green. However, the gel should be used carefully. If too much gel is added, a connection between electrodes can be generated. The brain activity was measured while the subject looked on a screen. If the display showed a green square he/she had to press a button, also when he/she heard a sound. The measurements took about 15 minutes. Afterwards the measured data for all electrodes for the two different conditions can be analysed.

Posted by Salome-Thamar Werner

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Week 11

This week’s course plan consisted of an excursion to Aalto Neuroimaging Infrastructure instead of the typical lecture. In this excursion, students were exposed to workings in fMRI (functional Magnetic Resonance Imaging), MEG (Magnetoencephalography), nTMS (navigated Transcranial Magnetic Stimulation), as well as a visit to ABL (Aalto Behavioral Laboratory). The visit allowed us to see in practice what Aalto researchers are working on, and how these imaging techniques can be utilized on the topics we’re studying during this course.
This week’s exercise session consisted of the discussion/answers of some previous quizzes that hadn’t been discussed yet, as well as the assigned exercise on the motor system. On this topic, we know that motor control can be dived into spinal control movement and muscle contraction, and brain movement, both the themes of the exercise’s essays. Motor neurons can be of the upper or lower type, upper delivering signals to the spinal cord, and lower innervating the somatic muscles. Within lower motor neurons, the classification can then branch into alpha motor neurons, responsible for muscle contraction, and gamma motor neurons, responsible for the input of the muscle spindle. The connection between upper and lower motor neurons is mainly achieved through the transmission of glutamate.

Posted by Ana Catarina Baptista De Sousa

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Week 10

The quiz for before this week’s lecture was about the topic of attention. Usually the quiz topic and the lecture are the same. There was an accidental mismatch regarding the topic this week. This lead to a special agreement regarding the exam: We can now choose which question/ topic of the two we want to answer.

The topic of the lecture of the course was about the mental illness. The human behaviour is influenced by two mutually interacting factors: heredity and environment. Because each individual has its own DNA code the brain, like the fingerprint, is different from all others. The other fact deals with personal experience, like trauma and disease. In Europe the highest costs of all disorders are generated by mood disorders. Depression is the leading cause of disability and of the leading factor for suicide worldwide. Because mental illness disrupt aspects of cognition, emotion and behaviour, they affect the learning and working ability of a person. Therefore a right therapy and care are important.

Anxiety disorders are based on fearing experience. Fear is an automatic fight-or-flight response and is also learned. Fear causes palpitations, sweating, trembling, shortness of breath etc. For example chronic stress leads to continuously elevated cortisol which leads in the death of hippocampal cells.

Posted by Salome-Thamar Werner

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week 9

In this week’s excursion, we visited the Cognitive Brain Research Unit (CBRU), at the University of Helsinki. The research center deals with human auditory and crossmodal cognition, as well as their impairments and plasticity. The main research fields are human language, music processes and the development of auditory functions. In the neurological field the EGG is a commen method for measuring the electrical activity of the human brain. The EGG measures voltage fluctuations on the scalp.

The excursion includes a visiting of a laboratory as well as a presentation about the current research projects. The laboratories basically consist of two rooms.The first room includes all the tools which are used for the measurments as well as the computer and display for monitoring and recording. Here the test person gets prepared for the measurement. Therefor an EEG cap is put on the test person head, which contains connections for the electrodes. A gel serves as a link between the electrode and the scalp. The second room is shielded and used for the mesurements. It’s a room without any other electronical devices to avoid interfering frequencies by electricity (artefacts). Essentially, the test person itself is the most susceptible to interference, for example through blinking, rapid head movements etc. For some measurments the test persons have to watch a silent movie while around five different sounds (like clicks or beeps) got replayed. For a good analysis each sound has to be repeated around 100 times.

Posted by Mona Hartmann

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Week 8

In this week’s excursion we visited Nexstim, which is a company that sells transcranial magnetic stimulation devices. Transcranial magnetic stimulation is used to treat depression but also for pre surgical mapping. Pre surgical mapping helps planning surgeries as well as makes them safer, because it I possible to determine the functions to the respective brain area. Previously we knew what the brain looked like and what functions it has. However it has been unknown for a long time which brain area corresponds to which function. The representative of Nexstim compared it to a city map, where we know what buildings exist, for example a post office, but not where they are. Invasive electro-stimulation first enabled the linking. TMS is another way with the huge benefit of being non-invasive. What characterises Nextstim in comparison with other TMS manufacturers is there accuracy and precision. They are so far the only device on the market which is licensed for surgery not only in Europe but also in the United States of America.

The presentation also included a demonstration on a subject. Therefore MR images that were previously acquired were opened in the software. The dominant landmarks, such as nose and ears along with other points of the head were registered with a pointer and a reference on the subjects head. This enabled matching the head with the MRI with an accuracy of 1.5 mm. EMG-electrodes have been fitted on the thumb (APB) and the lower arm (EDC). When stimulating the contralateral motor cortex, it not only allowed us to see signals in both muscles, but also see a difference in latency.

The excursion was very educative and it was nice to get to know the company Nexstim with their TMS devices.

Posted by Salome-Thamar Werner

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Week 6

This week’s lecture focused on “Chemical Control of the Brain and Behaviour”.
We started off by taking the quiz related to the topic and proceeded to quickly revise what we had learned so far about neurotransmission. This included, for example: the definition of neurotransmitter; glutamate’s function, receptors and toxicity (as well as GABA’s); how does the synapse mediated acetylcholine work, and what is the influence of serotonin on a person’s mood.
We then carried on to talk about the acetylcholinergic pathways, one of the “diffuse bran systems”. It was taught that Ach cell death is related to Alzheimer’s disease, and also that some acetylcholinergic neurons are involved in sensory learning.
Catecholaminergic neurons were also a topic of discussion, as they are neurons that contain dopamine or noradrenaline, and are related to Parkinson’s disease. Following the theme, we learned that the noradrenaline pathway is also another one of the diffuse brain systems. This pathway is related to the intensification of stimuli, as well as to a person’s mood and, therefore, clinical depression. On the other hand, dopamine pathways are involved in, for example, learning, reward system, and motivation.
The serotonin system consists of several pathways working together, as, once again, one of the diffuse bran systems. Serotonin is sensory processing, as well as emotional processing. Some evidence claims low levels of serotonin point towards depression and fatigue.
Finally, the hypothalamus and pituitary and their roles in using hormones as neuromodulators; oxytocin’ and vasopressin’s function; and the mechanics of the stress response were some of the other topics covered in the lecture.
There was no exercise session this week, and for the next lecture, we are meant to read chapter 11 (Auditory System).

Posted by Ana Catarina Baptista De Sousa

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Week 5

This week’s lecture was about neurotransmitter. With different videos the teacher tried to make it easier to understand the process of the post-synaptic ion-channels opening due to the transmitter docking to the receptors. A transmitter docking to a receptor causes a change in form, which leads to an opening of the ion-channel and subsequently to a change in voltage.

The exercise this week was one of a very different kind. Instead of the lecture hall, we meet in a room with computers. We were running a reaction time experiment with visual and aural stimuli. Both of the stimuli where presented in a block of 10 stimuli with random time in between each stimuli. The sequence of visual and aural stimuli was random as well. The reaction time was measured for the stimuli presentation until a keyboard event occurred. When later on analysing the data we have to consider a delay for audio as well as the monitor. However the delay is constant for the same stimuli, since all trials where conducted on the same computer, and can therefore be neglected, whenever the difference between different stimuli is looked at. In order to get some data to compare and average, the experiment has been run several times in a row. Possible changes to achieve a difference in the reaction time can be such as colouring the whole screen instead of a square in the middle or changing the frequency of the aural stimuli. However when conducted right after each other there could be a training effect transferred to the following experiment. It is therefore recommended to do the same amount of trials for each experiment, but to have a longer period of time between the different experiments.

Posted by Salome-Thamar Werner

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week 4

In this weekly lecture we learned more about sensory perception and processing of the taste, smell and visualisation. Some facts of the learned were written down here. The sense of taste as well as the sense of smell are addressed by chemical stimuli. Some sensory systems have a single basic type of receptor cell that uses one transduction mechanism (e.g., the auditory system). However, taste transduction involves several different processes and each basic taste (like salt, sour, better, sweet and umami) uses one or more of these mechanisms (like direct pass through ion channels or block ion channels etc.).The olfactory sensory system is constructed different, each receptor cell expresses a single olfactory receptor protein and the different cells are randomly scattered in a region. Each cell responds to many different odors, but with differing preferences.

The dioptric apparatus of the eye produces a side-inverted image on the retina that is upside down. The light stimuli are registered by the sensory cells of the retina, the rods (brightness) and cones (colour vision). Thereby the rods are located in the peripheral area of the retina and the cones in the central retina. In addition, visual perception includes spatial perception and object recognition.

For the next lecture, we are meant to read chapters 6 with focus on the neurotransmitters.

Posted by Mona Hartmann

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Week 3

This week’s lecture focused on synaptic transmission.

We started the lecture by taking the quiz on the corresponding chapters and then proceeded to learn how the action potential in axons work, through quite visual slides. One aspect of neurotransmission taught to us was the chemical synapse, in which neuron-type specific transmitters bind to membrane receptors causing ionic currents through the channels. Furthermore, electrical synapses were introduced as well. In this type of synapse, gap junctions between the pre- and post-synaptic neuron allow current to flow passively through channels, changing the post-synaptic membrane potential. Chemical and electrical synapses differ primarily in that there is no intercellular continuity in chemical synapses, thus the flow between the two neurons isn’t direct.

The exercise class was more “light-weight” compared to the lecture, as we learned more about the anatomy of the human brain by making a brain out of putty. This type of class was very interesting as it allowed us to learn through physical interaction with the material and have a better visual understanding of the concepts that were being taught to us.

For the next class, we are meant to read chapters 8 to 10, which focus on the chemical senses and on the visual system.

Posted by Ana Catarina Baptista De Sousa

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Getting started

We are three Erasmus students from Germany and Portugal studying Medical Engineering and Biomedical Engineering. We therefore still have to get used to the system, hence why this week’s blog post is our first. We are taking the course ‘Structure and operation of the human brain’ and we want to document our learning progress in this blog. Reflecting the lectures as we write our posts will hopefully help us in learning more effectively early on.

The first lecture was on the structure of neurons, but since we already had the second one, well will focus on that.
We discussed the structure of the membrane with the in-built ion channels. The electrical voltage inside and outside the cell are due to a difference in concentrate of Na+, K+, Ca2+ and Cl. Active ion pumps and passive ion channels keep up the voltage at about -70 mV, which we call resting potential. Whenever there is a stimulus, which exceeds the threshold, an action potential is evoked. Exceeding the threshold means that the voltage decreases to a certain degree or more. This happens by an opening of sodium channels, which results in Na+ flowing into the cell. An action potential is subdivided into a rising phase, an overshoot, a falling phase and an undershoot. Only after going through all the phases a new action potential can be evoked. To speed up the process of forwarding the signal, an insulating material, called myelin sheets, covers the axon. The signal now jumps from Ranvier node to the next, which are non-covered spots in between the myelin sheets.

The questions for the first exercise were varied in type which will allow us to consolidate what we learnt from reading the book in a more efficient way. The exercise session provided a good opportunity to clarify any doubts we had.

In order to prepare ourselves for the next lesson, we are reading two chapters of the book ‘Neuroscience – Exploring the brain’ by Bear. This will explain more about the action potential and the synaptic transmission.

Posted by Salome-Thamar Werner

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