The Scarecrow in The Wizard of Oz managed very well without a brain – and he was not the only one. The amoeba – a single-celled organism that has the ability to alter its shape and swims about freely – also has no brain. But a multi-disciplinary group of international researchers that includes Israelis has shown for the first time that even one-celled organisms such as amoebae can exhibit a conditioned response, remembering a pathway to food for up to 90 minutes.

Ivan Pavlov, the Russian physiologist who spent many years experimenting on conditioning animals and died in 1936, worked with dogs. He showed that higher-order organisms could be trained to respond to a stimulus rather than the actual thing – in his case, a bell instead of food. 

The most basic type of associative learning is the classical conditioning developed by the Nobel Prize Laureate Ivan Pavlov, who established the first systematic study of the fundamental principles of associative memory.” In his studies, after an appropriate conditioning, dogs deprived of food started to salivate simply by hearing a bell ring and not from seeing or smelling food. 

However, new experiments conducted by an Israeli brain scientist and a Spanish mathematician, cancer researcher and pathologist show that even one-celled organisms exhibit conditioned responses. They proved that even without a brain, amoeba were shown to be “intelligent” enough to be conditioned. 

This discovery opens a pathway towards understanding cell adaptation in a variety of important biological processes such as fetus development, the spread of cancer and in how we learn and remember. 

Their results were recently published in the prestigious journal Nature Communications

Dr. Shira Knafo of Ben-Gurion University of the Negev’s department of physiology and cell Biology and the National Institute for Biotechnology in the Negev  (NIBN) in Beersheba worked with Dr. Ildefonso De la Fuente of the CEBAS-CSIC Institute and the Department of Mathematics, Faculty of Science and Technology, University of the Basque Country, Dr. María Dolores Boyano of the Department of Cell Biology and Histology, Faculty of Medicine and Nursing, University of the Basque Country, 

They and their colleagues showed that amoebae will retrace a pathway to food even in the absence of food for anywhere from 20 minutes to 90 minutes. And this was while lacking a brain. Knafo and her colleagues believe instead of a brain, the memories are encoded temporarily onto a complex network of proteins.

In their experiments, the researchers put amoebae proteus on a slide with an electric current running through it. The amoebae are naturally drawn to the side with the negative current. But if food is put on the positive side, the amoebae will make their way there. More interestingly, even if the food is taken away, the amoebae will still gravitate towards the positive side for a certain amount of time. The researchers discovered a similar finding in the related species Metamoeba leningradensis.

Associative memory, the authors explained. is the main type of learning by which complex organisms endowed with evolved nervous systems respond efficiently to certain environmental stimuli. It has been found in different multicellular species, from cephalopods to humans, but never in individual cells. 

They found that amoebae are capable of linking two independent past events and move towards their target for an average of 44 minutes. One of the most remarkable accomplishments in the field of neuroscience is the description of essential principles that define the basic forms of associative memory for learning, they wrote.

“This fundamental cognitive property occurs through complex biological mechanisms by which the connection between two previously unrelated stimuli, or a behavior and a stimulus, is learned; when such process takes place, it is assumed that the association of these stimuli is stored in a memory system. For centuries, different thinkers have shaped a very plentiful and venerable history of research on basic learning processes. The combined work of philosophers, naturalists, physiologists, and life scientists has set the baseline upon which the modern learning theory currently stands. 

The NIBN, is a unique, one of a kind, research institute located within Ben-Gurion University, with a mission is to conduct multi-disciplinary, applied and innovative research guided by a biotechnological vision and to lead the commercialization of novel technologies developed by its researchers. NIBN focuses on cancer, infectious diseases, autoimmune and metabolic diseases, human genetic disorders, neurodegenerative diseases, and applied biotechnology. NIBN has 24 leading researchers, all Ben-Gurion Univerfsity faculty members, nearly 175 graduate students including post-doctoral fellows and some 40 technical and administrative staff. The NIBN holds a patent portfolio of around 50 patent families, and NIBN members have published over 800 articles in leading scientific journals. 

Source: Israel in the News