In my last post we explored the concept of epigenetics, and the idea of stressors leading to memories passed from one generation to the next not only in animals but plants as well. We saw that plants have the ability to store and recall biological information, but this information is different from the emotion filled memories that we recall daily. Yet, these plant behaviors can be considered basic, or remedial, forms of memory.
Mechanisms of plant memory, like epigenetics and electrochemical changes, are also factors in human memory. The neural connections in our brains are the seat of memory as we have come to understand it. Plant scientists have discovered that plants contain proteins known in humans and other animals as neuroreceptors. One good example of a neuroreceptor is the glutamate receptor. Glutamate receptors in the brain are very important for neural communication, memory formation, and learning. A number of neuroactive drugs specifically target glutamate receptors. At New York University, a group of scientists discovered that plants contain glutamate receptors, but at this point they do not fully understand what these glutamate receptors do in plants. But work carried out by Jose Feijo, in Portugal, has shown that these receptors in plants function in cell-to cell signaling in much the same way that human neurons communicate with each other. Does this beg us to consider similarities in human brain functioning and plant physiology?
Plant memory, like our human immune system memory, is not considered semantic or episodic. But rather it is considered procedural memory, meaning memory of how to do things, and these memories depend on the ability to sense external stimulation. There are three levels of memory associated with increasing levels of consciousness:
There is procedural memory which is associated with anoetic consciousness – not subject to conscious attention; having an indefinite, relatively passive, conscious being; having no awareness of recollection or remembering when performing a certain task. For an interesting discussion on anoetic consciousness in episodic memory see http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3879583/
Semantic memory which is associated with noetic consciousness – the ability to be aware of our inner and outer world through semantic memory. Noetic consciousness is “knowing,” having introspective awareness of the internal and external world. Through semantic memory we can think about the world, and know that we are doing so.
And lastly, episodic memory associated with autonoetic consciousness – “self knowing” and self awareness. Through episodic memory we are aware of our own identity and exsistence in subjective time that extends from the past through the present into the future.
The lowest level of consciousness, anoetic consciousness, characteristic of procedural memory refers to the ability of organisms to sense and react to external and internal stimulation, which all plants and simple animals are capable of.
Dr. William Lauder Lindsay, both a physician and botanist, wrote in 1876: “It appears to me that certain attributes of mind, as it occurs in Man, are common in Plants.” And, Anthony Trewavas, a plant physiologist based at the University of Edinburgh, Scotland points out that while humans are clearly more intelligent than other animals, it is unlikely that intelligence as a biological property originated only in Homo sapiens. He sees intelligence as a biological characteristic no different from body shape, or respiration, all of which evolved through natural selection of characteristics found in earlier organisms.
This leads me, and I hope you the reader, to consider the next question: If plants exhibit different types of memory and have a form of consciousness, should they be considered intelligent?
What do you think?