Is learning something then still possible?
I love the questions that children have. Why isn’t the sun alive? What would happen if we had eyes also on the back of our head, like spiders? And, can we live without a brain?
Well, occasionally anencephalic children are born and they lack almost the entire brain. Few live longer than a few days after birth, but there is a case of an anencephalic infant having been kept alive for almost 3 years. And there is the famous legend of the 15th-century pirate Klaus Störtebeker, who was captured to be beheaded along with his crew. According to the legend, he struck a deal with the executioner that those men of his crew that he’d run past, after being decapitated, should get their freedom. And how many men did the headless Störtebeker then pass in order to save them: 11 according to the legend.
Apparently the trauma of decapitation stimulates some movement automatism in the limbs (but not allowing a person to run without a head!). However, chickens whose head has been severed are well known to flap their wings and run around aimlessly for some 10-30 seconds after the head is gone. And the reason for that simply is that the neurons responsible for reflexive hind and forelimb (leg and wing) movements are not located in the brain, but in the spinal cord. The knee jerk reflex in humans is a good example, but stepping on a nail or a hot piece of coal are others: having to think and then to send a command from the brain to withdraw your foot from the pain-causing stimulus takes time; the reflex arc works faster.
There are, however, cases of headless, i.e. brainless chickens that survived longer than just a few seconds and the most famous of all is one by the name of Mike. Mike lived for 18 months without a head and was fed by his owner with a dropper supplying milk and feed directly into Mike’s oesophagus. What allowed these famous headless chickens to survive is the so-called brainstem that contains locomotory and breathing centres and escaped the blade of the axe or knife that severed the head. You can imagine my shock when as a student I had to cut off the heads of beetles (which I did not enjoy) and 5 days, later looking into the wastepaper bin, saw my headless beetles still crawling around in it in circles! It made me feel real bad. But seeing headless chickens and beetles run around, the question arises, could they still learn something?
For that we have to visit my former Professor’s research. George Adrian Horridge trained large headless cockroaches and locusts in such a way that they would learn not to place a leg into a position where it would get a small electric shock. Over a period of about 30 minutes the test insect first received many shocks as it puts its leg down, but it progressively raised its leg longer with the result that fewer shocks were received. That is was not due to fatigue or nerve or muscular damage was proved by attaching a second animal in series with the first (the one trained). The second animal could not associate the shocks with the position of the leg. When after 40-45 minutes the two animals’ positions were swapped and, still connected with each other, now the second earlier untrained animal got shocked with regard to its leg position, only the first, the trained animal, lifted its leg more readily hoping to avoid the shocks. It is quite clear from these observations that in the absence of a brain, the ganglia of the ventral nerve cord are able to associate a position of the leg with a repeated punishment by electric shock. Would this have worked with the headless chicken? I guess it might have. But let’s better not do that experiment.
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2019.
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