6.2 Short Term Memory

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Из курса от партнера Tel Aviv University

Understanding Plants - Part I: What a Plant Knows

502 оценки

Tel Aviv University

Understanding Plants - Part I: What a Plant Knows

502 оценки

For centuries we have collectively marveled at plant diversity and form—from Charles Darwin’s early fascination with stems and flowers to Seymour Krelborn’s distorted doting in Little Shop of Horrors. This course intends to present an intriguing and scientifically valid look at how plants themselves experience the world—from the colors they see to the sensations they feel. Highlighting the latest research in genetics and more, we will delve into the inner lives of plants and draw parallels with the human senses to reveal that we have much more in common with sunflowers and oak trees than we may realize. We’ll learn how plants know up from down, how they know when a neighbor has been infested by a group of hungry beetles, and whether they appreciate the music you’ve been playing for them or if they’re just deaf to the sounds around them. We’ll explore definitions of memory and consciousness as they relate to plants in asking whether we can say that plants might even be aware of their surroundings. This highly interdisciplinary course meshes historical studies with cutting edge modern research and will be relevant to all humans who seek their place in nature. This class has three main goals: 1. To introduce you to basic plant biology by exploring plant senses (sight, smell, hearing, touch, taste, balance). 2. To introduce you to biological research and the scientific method. 3. To get the student to question life in general and what defines us as humans. Once you've taken this course, if you are interested in a more in-depth study of plants, check out my follow-up course, Fundamentals of Plant Biology (https://www.coursera.org/learn/plant-biology/home/welcome). In order to receive academic credit for this course you must successfully pass the academic exam on campus. For information on how to register for the academic exam – https://tauonline.tau.ac.il/registration Additionally, you can apply to certain degrees using the grades you received on the courses. Read more on this here – https://go.tau.ac.il/b.a/mooc-acceptance Teachers interested in teaching this course in their class rooms are invited to explore our Academic High school program here – https://tauonline.tau.ac.il/online-highschool

Из урока

What a Plant Remembers?

This week we move beyond survey of a plant's sensory systems, and explore how plants retain, store and recall sensory information. In other words, we ask the questions, What do plants remember? We'll try to define what we mean by "memory" and briefly review different types of human memory. The we'll look at the short-term memory found in the Venus fly trap, and the long term morphogenic memory first described 50 years ago by the Czech scientist Rudolf Dostal. We'll have a guest lecture from Prof. Nir Ohad about epigenetics and the long-term memory of winter, and even the role of epigenetics in trans-generational memory.

6.1 What a Plant Remembers?5:55

6.2 Short Term Memory5:31

6.3 Long Term Memory 15:59

6.4 Long Term Memory 2 (with Prof. Nir Ohad)10:07

6.5 Epigenetic Heredity1:56

6.6 Intelligent Memory?3:03

Познакомьтесь с преподавателями

Professor Daniel Chamovitz, Ph.D.
Dean, George S. Wise Faculty of Life Sciences
Director, Manna Center for Plant Biosciences

Let's go back to plants, because that's what we're mainly interested in.

If we analyze these different types of memories

in plant processes, in coding, storage, and retrieval.

So I want to start with short term memory.

Can we define short term memory in plants?

And our example here is the Venus flytrap,

which we learned about in a previous lecture.

So let's review, again, this movie which we've already seen,

which shows how the Venus flytrap waits until its prey has gotten into the middle.

And then closes on it.

Okay, just a quick review to remind you what we learned earlier,

what we saw was that the prey has to touch two hairs.

It will touch the first hair and then, if within

twenty seconds a second hair is touched, the trap will close.

If it was more than 20 seconds, the

trap has forgotten this information and remains open.

So at a very basic level this is a clear

example of short term memory.

A memory that lasts a number of seconds and then is forgotten.

So, what is the mechanism by which

the Venus flytrap encodes this short term memory?

Well the simple answer is in the electric charge that we learned

about, about, that we learned about

in understanding the mechanism of the cloning.

And interestingly, this electric charge, the electric information,

is similiar to the workings of our brain. Again, to review, what do we have?

In the first touch, we get a depolarization, a change in

electric charge across the membranes, and a release of the calcium ions.

And again, I remind you, that the release of calcium ions in response

to the depolarization is very similar to

what happens in neural communication in humans.

When you get the second touch,

you're getting a second depolarization and a release of more calcium ions.

And here's where we come into the memory.

If the accumulative charge, the first charge, plus the second charge, and the

total calcium concentration passes a threshold, then the trap closes.

If it doesn't pass this threshold, it remains open.

So where does the short term memory come in?

Well, after the first depolarization you get an

increase in charge which rather quickly dissipates over time.

If it has dropped enough, which after 20 seconds, so that when the

second charge comes, we don't reach the

threshold, then you don't have the response.

You don't have the memory.

The short-term memory is in if there is enough charge

in order to let that the second depolarization reach the threshold.

If the two charge is within 20 seconds you pass the threshold.

After 20 seconds you don't pass the threshold

you've lost, the plant has lost the information.

This model was reinforced by experiments that were carried

out in the laboratory of Alexander Volkov around 2008.

And in his experiments, rather than manually stimulating

the hairs, he stimulated the trap directly with an electric shock, with electrodes.

If he gave one large electric shock, which went over

a particular threshold, then he could get it to close.

If he gave one small shock, the trap wouldn't close.

But if he gave many small shocks, eventually the trap would close.

And then there was always the question of

whether the total electric potential went over a threshold.

It could be one large one, or several small ones, and in the end it would close.

So we can see here a sort of, a type of flowchart for

a plant to decide, for the Venus flytrap to decide, whether to close.

We start with an open trap. The trap now waits for a stimulation.

It's waiting for the mechanical stimulation by the prey.

After the first stimulation, the first hair

is touched, you're getting a receptor potential.

The receptor potential's leading to an action potential.

And then this leads to the beginning of the

electrical memory, which is stored as an electrical charge.

Now this charge starts going down. Now we go to the right here of the chart.

And you're getting the second stimulation.

The second stimulation of the hair causes the exact same thing.

You're getting an action potential which adds to the electrical memory.

If this electrical memory now has passed the threshold, then you're getting

the electrical memory through the, the

electrical signal throughout the entire trap.

This will cause a number of processes

which will enable the trap eventually to close.

If the second stimulation occurred late, after 20 seconds, the electrical

memory threshold was not reached and then the trap will remain open.

So what we've seen here is a clear

electrical mechanism which allows plants to have short-term memory.

And again, I want to note that this is a little bit hand-waving, but our brain also

works through electrical potentials, and that's one of

the mechanisms that's involved also in human short-term memory.

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