Behavioral Biology (1981)

[Music] thank you [Music] thank you [Music] in a sunny Little Pond long before plants and animals appeared life was thriving ancient sediments the remains of ponds and shallow Seas contain micro fossils of cells not unlike the cells found living in such places today in this sense most any puddle is a time capsule a place to examine the elemental biological processes of life including the most amazing process of all Behavior [Music] even bacteria the simplest cells contain a behavioral program [Music] scale of single cell life paramecium an elaborate cell with a somewhat wider range of Behavioral responses located in its bluish nucleus are the genes that ultimately determine its Behavior but what exactly does a paramecium do in the field of the microscope they seem to spend their energy just zipping around perhaps if we look at them in a more natural environment paramecium is a bacteria eater and the best hunting is in the micro jungles of rotting vegetation in this case a leaf [Music] there is plenty of food here but in order to live in this kind of habitat paramecium must overcome a hazard getting trapped the question is has paramecium inherited a behavioral program for escape [Music] comes into a fiber every time the same bump back up turn and proceed until it runs into another obstacle if an opening exists this response will eventually allow paramecium to escape a neat trick for a single cell but behavioral biologists want to know more [Music] probe the internal mechanisms that control the behavior and ultimately find out how Behavior patterns evolve for example a crystal of salt produces a lethal environmental hazard as the concentrated salt solution spreads nearly all of the paramecia respond to fail is to die natural selection is at work weeding out genes that produce faulty Behavior the basis of behavior lies in the genes this means that behavior like other inherited traits is subject to evolution this fundamental concept is easy to understand in single-celled life but what about multicellular animals The evolutionary stepping stone between single cells and multicellular organisms is thought to be colonies of cells like these but even cells that simply cluster together face a problem not found in single cells coordination in colonies of cells like volvox there must be teamwork so that the colony as a whole can respond to its environment [Music] for example using a nicely coordinated rolling motion volvox swims away from intense light in this way avoiding heat and ultraviolet radiation that would harm its delicate cells [Music] any further advances in coordinated Behavior depended upon the development of a communication system a system based on a cell that was able to conduct electrical impulses the nerve cell or neuron basic unit of the nervous system of animals as an animal develops from a fertilized egg some cells in the embryo become destined to form nerve tissue including a tangled mass of nerve cells a brain in this amazing organ the individual inherits the wiring diagram for the behavior of its species take this plainly colored male fish somewhere in its brain are instructions for all kinds of social interactions for example how to deal with a rival male entering its territory [Music] living in separate tanks our fish have never seen each other how will they behave during their very first visual encounter the amazing thing is that each fish behaves in exactly the same way putting up a fierce display flaring its Gill covers and turning on its brilliant fighting colors [Music] such Behavior patterns are somehow stored in the animal's brain all ready to go the first time they are needed but how this is one of the toughest questions in behavioral biology for the brain of a vertebrate animal is an incredibly complex structure consisting of Untold millions of nerve cells linked together in a maze of Tangled circuits to make a start at probing the connection between brain and behavior biologists needed an animal with a much simpler brain mollusks are such animals particularly the slowly moving marine animals known as sea slugs this one named tritonia comes from the sea floor along the Washington coast and it has proven to be a most useful experimental animal in the early 1970s Dr Dennis Willows working at the University of Washington marine biology laboratory at Friday Harbor began a systematic search of tritonia's brain a search for the brain cells that program Its Behavior the brain of this mollusk is at the bottom of the opening four brownish loaves of nerve tissue Willows found that each lobe was composed of relatively few but exceedingly large brain cells most important individual cells could be identified by spots of pigment the same identifiable brain cells in exactly the same positions were found in each tritonia he dissected this in itself was an exciting Discovery could this simplified brain with its giant cells be the key to tracing out the brain cell circuits involved in the behavior pattern but what Behavior what do sea slugs do for one thing they have a characteristic Escape reaction triggered by contact with a kind of predatory starfish found in their home Waters [Music] the behavior pattern appears to be a fairly simple one when touched by a starfish's tube feet the sea slug pulls in its sensory equipment bends away and begins a series of flexing motions that produce a crude sort of swimming not very graceful perhaps but effective for avoiding capture by the starfish [Music] there seemed to be two distinct movements in the swimming reaction a down Flex and a back Flex could the wiring diagram responsible for these flexing motions be found somewhere in tritonia's tiny brain could it be traced to individual cells the problem was to hold the brain firmly enough to probe its cells while allowing the animal to exhibit Its Behavior [Music] together Willow's idea was to isolate and stabilize the four brain lobes without destroying their connections to nerves entering and leaving to do this he devised an adjustable brain platform that could be slipped underneath the brain once pinned to the wax covered platform by its surrounding tissue the brain became relatively immobile regardless of what the freely suspended animal might do under these conditions experimental animals remained active for many hours and Willows began working out the techniques for monitoring electrical activities going on inside of individual brain cells if he succeeded it would be the first time anyone had listened to internal Communications among identifiable brain cells while at the same time watching the behavior of an intact animal the probing utilized a hollow electrode filled with conductive solution and tapered to a point so fine that the actual tip was invisible under the microscope carefully probing with the ultra microscopic tip Willows began listening in on the signals being received by individual cells in tritonia's brain a strong signal he just stroked the animal's skin [Music] here it is again stroke [Music] stroke pinch that got the cell's attention by this method Willows could trace input wiring finding which brain cells were connected to which parts of the body he also used his micro probes to monitor brain cell output nerve impulses generated from within a brain cell if he excited the cell by feeding it a pulse of electrical energy there was a short burst of impulses causing the animal to make a small flexing motion again stimulate the cell it responds with three quick impulses and the sea slug flexes Willows concluded that the cell being probed played a role in the down Flex part of the swimming Behavior at the touch of a starfish anywhere on its body the down Flex cell puts out an intense burst of signals then it's quiet then another burst each causing the down Flex muscles to contract [Music] while the downflex neuron is quiet up Flex neurons are firing and if the animal were not restrained it would certainly swim away down Flex neurons fire up Flex neurons fire down Flex up Flex here is the swimming part of tritonia's Escape reaction tied to two groups of brain cells but how is this cycle of brain cell activity initiated by the lightest Touch of a predatory starfish two of Willow's colleagues Dr Paul Taggart and Dr Peter getting located a cell in the animal's brain that when stimulated elicited the entire fully coordinated Escape Behavior oh [Music] they called it a trigger cell for swimming now for the first time a behavior pattern could be understood in terms of brain cell circuitry when Touched By An exploring starfish receptors in tritonia's skin chemically recognize the stimulus and generate an Impulse that travels to the trigger cell responding the trigger neuron fires a short burst of impulses to the brain cells that control the flexing motions once started the flex cells continue firing for a number of Cycles carrying tritonia to safety this behavior is the direct result of Gene controlled nerve cell circuitry all ready to go the first time it's needed for survival in these animals with accessible brains we have caught just a glimpse of the mechanisms that underlie Behavior and now we wonder can Behavior patterns in more complex animals also be understood in terms of nerve cell circuits is the idea of behavior based on a fixed wiring diagram compatible with learning which can produce changes in Behavior a new frontier of biology has been opened behavioral biology through its discoveries and Concepts we may eventually understand a most amazing life process the process of behaving [Music] thank you foreign [Music]