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Brain Synapse

Researchers develop device which can forget things like our brain

Scientists are trying to emulate the human brain since it is the ultimate computing machine. In this effort, the latest research has resulted in the development of a device which can also “forget” memories much like our brains. 

It is known as a second-order memristor. It mimics the synapse of a human brain in such a manner where it stores information but then loses it slowly when it is not accessed for a long time period. The device currently does not have a practical use but this could be a stepping stone to a unique kind of neurocomputer which can perform the same functions that a human brain does. The work appears in ACS Applied Materials and Interfaces

In an analogue neurocomputer, neurons and synapses can be replicated by the on-chip electronic components. This could help in amplifying computational speeds as well as decreasing the energy requirements of the computer. 

Presently the analogue neurocomputers are not feasible as researchers need to figure out how synaptic plasticity can be also implemented in electronics. This is the technique in which the active brain synapses become strong while the inactive ones get weak resulting in fading away of memories. 

Previously, memristors were produced by nanosized conductive bridges which decayed with the passing of time similar to how we forget some incidents. 

Anastasia Chouprik, a physicist from the Moscow Institute of Physics and Technology(MIPT), Russia said that in the first order memristor, the problem is that the device changes its behaviour with the passage of time resulting in its breakdown. The synaptic plasticity has been implemented in a robust manner this time which sustained the change in the state of the system for 100 billion times. 

A ferroelectric material, hafnium oxide was used along with electric polarisation which changes in response to an electric field. It is already used by Intel for manufacturing microchips. So it would be easier to introduce the memristors.

Researchers faced challenges in finding the proper thickness for the ferroelectric material. They found four nanometres to be the ideal thickness as a nanometre more or less would make it unsuitable for application. 

The forgetfulness is implemented through an imperfection as a result of which microprocessors based on hafnium are difficult to develop. The imperfection is the defect present at the interface between hafnium oxide and silicon which results in the decrease in the memristor conductivity. 

There is a long way to go as these memory cells have to be made more reliable and suitable enough to be integrated into flexible electronics. Another physicist, Vitalii Mikheev said that they would be studying the relation between several mechanisms through changing the memristor. There might be mechanisms other than ferroelectric effect which have to be studied.

Journal Reference: ACS Applied Materials and Interfaces

brain organoids in a petri dish

Researchers created lab grown brain that independently connected to spinal cord

There are many diseases wherein one needs a donor to donate an organ, it is very difficult to get donors these days and even if you get one, it should be a perfect match. However, there are various complications that are bound to happen during the transplant. Hence, scientists are finding alternate solutions to transplant and that is nothing but growing an organ artificially and then letting it grow in the body.

It is very difficult to grow something in a laboratory as there are many factors that one has to consider, right from is it getting the proper environment to producing and also giving it the proper nutrition it requires.

After a lot of research, scientists in UK have cultivated an artificial brain in a dish and the behaviour of the brain is similar to the brain developed in humans. Scientists say that the size of the brain grown in the laboratory is similar to the size of human fetal brain at 12 to 13 weeks during which the ‘brain organoid is not complex since it doesn’t have any thoughts, feelings or consciousness – but that doesn’t make it entirely inert. It is composed of two million organized neurons.

The scientists when placed this piece of brain next to a piece of mouses’ spinal cord and a piece of mouses’ muscle tissue, this pea-sized blob of human brain cells sent out long, probing tendrils to check out its new neighbours. After which, they spontaneously connected itself to nearby spinal cord and tissue. This was observed with the help of long term live microscopy.

These probings aren’t the only skills. This brain was also the first sample to initiate muscle movement. The researchers also noticed the visible and controlled muscle contraction.

Lab Grown Brain

An image of the cerebral organoids grown from stem cells by Cambridge researchers.
Photograph: MRC Laboratory of Molecular Biology

Madeline Lancaster neuroscientist from the Medical Research Council Laboratory of Molecular Biology told The Guardian, “We like to think of them as mini-brains on the move.”

The authors mentioned, “After 2-3 weeks in co-culture, dense axon tracts could be seen innervating the mouse spinal cord and synapses were visible between human projecting axons and neurons of the mouse spinal cord. Live imaging of the mouse muscle tissue revealed sporadic concerted muscle contractions with irregular periodicity.”

Today, most brain organoids are grown from human stem cells, which spontaneously organize themselves into the structures and layers needed for early brain development. The problem is, once this cluster gets to a certain size, the middle becomes deprived of nutrients and oxygen and it stops becoming useful. Therefore the researchers sliced up the organoids and placed them on a porous membrane, the researchers made sure that their mini-brains could simultaneously use the air above and absorb the nutrients below, staying healthy after a year in their dishes.

The authors are hopeful that the success of their new approach will allow us to model brain diseases in greater detail than ever before.

The authors write, “For instance, it opens the door to the study of neurodevelopmental conditions of the corpus callosum, neuronal circuit imbalances seen in epilepsy, and other defects where connectivity is thought to play a role, such as in autism and schizophrenia.”

Published Research: https://www.nature.com/articles/s41593-019-0350-2