Scientists discover single cell creatures can learn new behaviours despite having no nervous system

It was previously thought that learning behaviours only applied to animals with complex brain and nervous systems, but a new study has proven that this may also occur in individual cells.

As a result, this new evidence may change how we perceive life itself...

The new research published on November 19 in Current Biology has found evidence of habituation - which can be defined as a type of learning whereby you get so used to something in your environment that you stop noticing it, like noise or sound for example - within single-cell creatures such as ciliates and amoebae.

Researchers at the Centre for Genomic Regulation (CRG) in Barcelona and Harvard Medical School in Boston used computational modelling to see how molecular networks inside ciliate and mammalian cells reacted to various sequences of stimulation.

Previously, studies on this topic matter have been controversial with the first being single-celled ciliate Stentor roeselii experiments in the 20th century that were disregarded back then. This theory was further explored in the 70s and 80s when signs of habituation in other ciliates were found.

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“These creatures are so different from animals with brains. To learn would mean they use internal molecular networks that somehow perform functions similar to those carried out by networks of neurons in brains. Nobody knows how they are able to do this, so we thought it is a question that needed to be explored,” said Rosa Martinez, co-author of the study and researcher at the Centre for Genomic Regulation (CRG) in Barcelona.

Mathematical equations were used to understand the cell's language and reactions and this method meant that experts could further understand how molecular interactions inside cells changed when repeatedly exposed to the same stimulus.

There was a specific focus on negative feedback loops and incoherent feedforward loops - in simple terms, the first is comparable to a thermostat shutting off a heater when a room reaches a certain temperature, while the other is like a motion-activated light with a timer.

Between these two molecular circuits, the cells use at least both in response to a stimulus and therefore echo signs of habituation which is typically found in complex brain and nervous systems.

Though not all reactions happen at the same time, these vary in what scientists call "timescale separation" which Dr. Martinez reckons "could be a type of ‘memory’ at the cellular level, enabling cells to both react immediately and influence a future response".

So what does this new information mean?

The findings suggest that single cells can remember things and so this understanding can be applied and possibly explain why bacteria can become resistant to antibiotics.

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