Hello to all of our loyal Cellfie fans out there! Today marks a pivotal day in the UK as our schools are due to reopen for the first time since Christmas. In order to mark this historical date, we have an amazing article from one of our dedicated monthly writers, Kaja. Thank you, Kaja, for your hard work to put this together. So, can the most simple organisms have the potential for deeper cognitive function?
A unique feature of organisms having a nervous system, including humans, is receiving and storing memories. They are the key to unlocking our past, the events that want or even don’t want to be remembered and returning to the memories we cherish. However, is that really the case? Perhaps even a simple single-celled slime mold can be quite smart and make memories and decisions?
First, let’s recap what the memory making process looks like in humans. Our environment is a major factor in helping us shape our memories - it supplies the oceans of sensory information that reaches our brain. The information is processed by the prefrontal cortex and its frontal, parietal, temporal and occipital lobes.
The sensory information reaches the short term memory, which has only limited capacity (around 7 pieces of information) and duration (maximum of 30 seconds), so we may not remember some things for too long. However, if we repeat them by maintenance rehearsal, the information can be passed onto long-term memory, which in turn has unlimited capacity and duration - we can recall some information even 50 years after we had learnt it (as in Bahrick’s study on face recognition).
The long term memory is divided into declarative memory (facts, data, events), which we can consciously recall and nondeclarative (procedural) memory, responsible for unconsciously remembering how to perform certain actions. Within the declarative memory we have the semantic memories which contain the knowledge we possess and it is a bit like our own private Wikipedia - so the very important fact of the exact name of the state where your favourite fried chicken restaurant chain originates from is located in the regions of the cortex beyond the hippocampus (the seahorse structure in the temporal lobe of your brain)!. Additionally, the declarative memory consists of episodic memories, which are related to our experiences of the past events. However, the brain being very complex, another structure called the amygdala throws in its two cents and adds the emotional value to our experiences. The nondeclarative (procedural) memory on the other hand comes in especially handy when we walk! At first, when we are babies, we have to be very careful about every single step, but over time we just do it without even realising that we no longer need constant conscious thinking about what angle to put our foot at to maintain the balance - the same principle relates to driving a car. The areas of the brain without which our motor skill learning would not be possible are the cerebellum at the back of our brain (responsible for coordination and control of movement), prefrontal cortex and basal ganglia (plays a big role in forming and tracking our habits).
Now let’s come back to the main topic of this article, which is whether forming new memories is possible without having a brain? Based on what you’ve just read it may see that it is highly unlikely. Where would these memories be received to, integrated, processed and stored? The answer lies in the Guinness Book World Record holder for the ‘largest cell on Earth’ - the Physarum polycephalum slime mold.
Researchers from the Max-Planck Institute for Dynamics and Self-Organization and the Technical University of Munich have found that the single celled organism’s way of forming memories was through the specific occurrences that happened to its extensive tube network. The tubes are used as a source of contraction that helps in the transport of nutrients and fluid through the slime mold. The change in the tubes happened especially during the microorganisms feeding process. The tubes in the tube-web of the organism changed their shape and pattern in response to the food source - they became thicker or thinner. This change in the pattern aided by a release of chemicals from the source of food (which caused the dilation of the tubes located nearest to it) was maintained quite a long time after the organism was fed and was found to help the organism remember where it had found the food recently. This led to an idea that it could be this reorganization that causes the organism to make clever decisions about its future actions e.g. regarding its movement to the next source of food - the mold may already be in a position to reach it faster, by directing the movement of fluid specifically and by the food source being closer to the already widened tubes.
All in all, every organism, whether having a central nervous system or not, will master the ability to make a way of obtaining more food. Just joking. Even the simplest organism, such as the amoeba-like single cell can make smart decisions - in this case by using the chemical signals from the food source and manipulating the pattern of the tube network inside them. However, just as in the case of humans, whose memories will not be remembered unless they undergo maintenance rehearsal, the mold’s memories may also disappear if some of the tubes grow smaller and smaller and the organism hunts for more food sources. However, the researchers have said that this finding, although may seem simple at first sight, could be a way of understanding the behaviour of other similar organisms and be the help in creating machines able to move through various environments, all while remembering their way around.
Sources:
- Psychology textbook
- ‘Brain Facts’
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