Neural Connections

Neural Connections

Neurons are the key element of neuroscience study.

At the end of the 19th century, Santiago Ramón y Cajal established, for the first time, that neurons are individual elements of the nervous system; he suggested that they act as units that communicate with one another by meshing a network of connections.

Neurons are the structural, functional units of the nervous system. These cells receive stimuli from the environment, turn them into nervous stimuli and transmit them between neurons. Or they transfer them to a muscle neuron that will trigger a response. Thanks to research in neuroscience, we have a complete understanding of neurons. We know their morphology and that they have a core, dendrites and an axon; we know how they communicate with one another.

We also know how nerve signals are transmitted from one neuron to another; we know that some neurons are specialized in the visual system and others in the auditory system. Some help us remember things, and some help us recognize faces. We have also learned that there are no specific anatomical regions for all these systems. Instead, neural networks are reinforced with every new connection.

Thanks to new imaging technologies, we have found the human connectome, one of the current projects that significantly furthers our knowledge about neural connections.

The connectome is a map that models the brain and its activity as a connected network, depicting every brain connection. It can show:

  • Individual connections between each neuron and synapsis.
  • Connections among axons (cell populations).
  • Activity in brain regions. Currently, expert Alex Fornito’s team works on this as applied to human beings.

The development of the connectome ensures greater knowledge about the functioning of the brain and neural connections. It enables us to gain more knowledge about our brain activity, and it therefore allows us to better detect and treat the potential dysfunctions (disorders) and improve brain efficiency and performance.

Now, we will analyze some specific examples of the study of brain connections that were shown during our FTF discussion:

Connection Patterns

By studying neural connections, we can learn more about how different parts of the brain communicate with each other and detect connection patterns. We can observe, for example, which brain circuits perform specific functions or which ones are affected in people with disorders.

The Blue Brain project works on comprehensively modeling these connections in an attempt to decode and study brain structures in detail. The project integrates thousands of data points to digitally reconstruct neural circuits and brain structures. They are developing a digital map that recreates, as accurately as possible, neural paths in human brains and how they activate.
Then, it introduces electrophysiological and synaptic attributes to build a model of the circuits that shows aspects such as the slow oscillation of neural networks, an intrinsic property of brain cortex. These oscillations appear especially during sleep stages. They are neural activity waves that go from one point of the cortex to another every one to four seconds. The digital model designed by the Blue Brain project integrates this low frequency oscillation leveraging only on data.

The best way to understand these waves is as the transition from wakefulness into sleep, which is a process that involves significant changes in brain activity and its connections. While we sleep, our neural circuits are hyperexcited, and while we are awake, their excitability is normal, most of the time. As Sean Hill explains, wakefulness and sleep stages are not completely binary. This means that when you sleep, your brain isn’t necessarily asleep and when you’re awake, your brain isn’t necessarily awake.
This observation allowed us to learn that there is a dramatic difference between the connectivity of the brain when we are asleep and when we are awake. Currently, one of the most widely supported processes that explains this is the synaptic homeostasis hypothesis, which suggests that sleeping at night is the price we pay for the brain plasticity that we use during the day.

By knowing the connection patterns between neurons, which vary depending on the functions or activities they perform, we can learn about different brain states, determine how connection patterns or excitability modes relate and predict potential dysfunctions or disorders.

Concept Neurons

Neuroscience also focuses on gaining knowledge about what types of neurons there are and how they work.

Click here to learn more about neurons:

Neurons are specific cells of the nervous system that can transmit nervous stimuli to other cells. There are several types of neurons, depending on:

– their shape and size: polyhedral, fusiform, star-shaped, spherical and pyramid-shaped.

– their function: motor (related to movement and muscle coordination), sensory (related to the perception of external stimuli outside the body) or interneuron (which connect different types of neurons, creating neural networks).

– their polarity, the number of electric terminals they have and their arrangement; there are different types.

In the Future Trends Forum, we talked about the main advances in the discovery of new types of neurons and their behaviors. The main finding that we can use as an example are Rodrigo Quian’s concept cells or Jennifer Aniston cells.

For 15 years, Rodrigo Quian has observed the behavior of both individual neurons and groups of neurons in patients with epilepsy that received intracranial electrode implants to fight the disorder. He showed photographs to the patients and realized that there is a group of neurons that only respond to pictures of Jennifer Aniston. He discovered there are neurons in the brain that only respond to concepts, regardless of the context. They respond to the idea of Jennifer Aniston, not to specific pictures of her. These neurons have been named “concept cells.” They are found in the hippocampus, the brain region where memory is located, and are only present in humans. This finding promotes the hypothesis that these neurons might be the basis for human intelligence.

Brain Imaging Techniques

All neuroscience findings bring us closer and closer to a better understanding of how the brain works on a cellular level. This is possible thanks to technological developments that enable us to observe this organ at different scales and with various techniques. Naturally, the more sophisticated the imaging methods are, the more rigorous, detailed and valuable the information will be.
Currently, there are many neuroimaging modalities, such as magnetic resonance, magnetoencephalography or electroencephalography. There also more detailed techniques, such as the optical coherence tomography or the transcranial direct-current stimulation. Overall, we can place them in two categories: neuroimaging techniques that study structural and anatomical features and imaging modalities that study functional aspects.

We currently use all these techniques for clinical diagnosis and research, but neuroimaging techniques can be useful for many other areas as well, such as ageing and neurorehabilitation or childhood learning. They can even be applied to fields like artificial intelligence, computational neuroscience, materials science, hardware engineering, biomedical engineering and biotechnology.

In spite of everything that current neuroimaging techniques can achieve, developing new tools is an ongoing process that faces several ethical, legal and privacy challenges, which should be addressed as these new techniques and their applications are developed.

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