Behavior is as much about environment as it is about cognition

Over at TalkingBrains, Greg Hickok points to a review on embodied cognition that has several neat examples of how distinct behavior arises just by placing an agent in the correct environment:

Robots with two sensors situated at 45 degree angles on the robot’s “head” and a simple program to avoid obstacles detected by the sensors will after a while tidy a room full of randomly distributed cubes into neat piles:

and

Female crickets need to find male crickets to breed with. Females prefer to breed with males who produce the loudest songs… Female crickets have a pair of eardrums, one on each front leg, which are connected to each other via a tube. It so happens that the eardrums connect to a small number of interneurons that control turning; female crickets always turn in the direction specified by the more active interneuron. Within a species of cricket, these interneurons have a typical activation decay rate. This means that their pattern of activation is maximized by sounds with a particular frequency. Male cricket songs are tuned to this frequency, and the net result is that, with no explicit computation or comparison required, the female cricket can orient toward the male of her own species producing the loudest song. The analysis of task resources indicates that the cricket solves the problem by having a particular body (eardrum configuration and interneuron connections) and by living in a particular environment (where male crickets have songs of particular frequencies).

(Emphasis added.)

This, of course, is a perfect example of why we need ethology in order to understand the nervous system – behaviors only make sense in the context of the ecology that they operate in!

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The straw that broke the camel’s back

One of the most interesting things in neuroscience is that we find again and again that the different nervous systems come up with the same solutions to related problems.  Take the ability to make a decision – something that is about as basic and fundamental as you get, while needing to be applied to all sorts of situations.  In monkeys deciding whether to look at or away from an object, if you track neurons in one area of the brain (LIP), you see that the activity fluctuates up and down until it gets to some threshold and the decision is made.

This principle extends beyond simple decisions to include what may seem to be more complex decisions such as the decision to fight or (at a later time) flee.  Although it may not be the first example to leap to mind, cricket fighting can give us plenty of insight into how this decision might be represented in the brain.  Cricket fights have been a popular past time in China for over a millenia (though imho beetle fighting is much more entertaining).  Crickets make for great subjects for scientific study: they’re small, don’t take a lot of resources, don’t complain too much, and have highly stereotyped behaviors which make quantifiable analysis simple.  When two male crickets meet, they will often fence with their antennae (pictured above), and as fights become more intense will move to engaging with their mandibles and eventually some pretty intense wrestling-like grappling.  The winner will then sing the loser off to prove his might.

All cricket fights are required to start with antennal fencing.  If their antennae are removed, the poor little guys will not fight.  They still recognize each other – they can still court – but there is no fighting.  Of course, not every cricket will want to fight every other cricket.  They have some sense of hierarchy, so a highly dominant cricket will be more likely to run off a highly submissive cricket.  And if a cricket is placed in a tiny little home, as soon as 2 minutes later they will be more likely to get aggressive in order to defend their home.  There’s something very anthropomorphic and sweet about that, I think.

Aggressiveness is represented in the brain through the neuromodulator octopamine, and this can have surprising side effects.  See, octopamine is the insect equivalent of neuroadrenaline and it is released by physical movements.  The fans of Chinese Cricket Fighting will already know this; it has long been suggested that if your cricket isn’t being aggressive enough for your taste you should just chuck the guy in the air.  And what do you know?  He’ll be more likely to put up a fight now.  Even better is it to make him fly for a while in a wind tunnel.  So we see that the representation of aggression can have surprising side effects.

The flip side of fight is flight, and a cricket needs to know when in a fight to switch to flight.  One can begin to determine how a cricket knows when to flee by mangling the cricket.  Sorry guys, that’s science for you.  You can blacken their eyes so they cannot see, lame their mandibles so that they cannot bight, and clip their claws so that they cannot tear, then mamed crickets to fight and see how they do.

Blinded crickets who fight crickets with mamed mandibles will win 98% of the time.  That’s quite a lot!  These blinded animals will not feel much of a physical blow from their opponents, and will not be receiving any visual social input either.  Remove either of these conditions – make a nonblinded cricket fight a lamed one, or a blinded cricket fight a healthy one – and the healthy one will probably win.  So how do these crickets know when to flee?  By the steady accumulation of visual and physical input.  Once enough of this input is received – possibly represented in the form of some hormone or peptide – it’s time to fly for the cricket!

It wouldn’t be surprising if something like this happened in humans, too.  We already have a proverb for it after all: the straw that broke the camel’s back.  Crickets will continue to fight after a serious injury, only to retreat seconds later for no apparent reason.  So too are humans known to accept plenty of punishment and grit out, only to have something small cause them to cry and give up when their threshold is reached.  This is one of the the fundamental lessons of decision neuroscience so far: discrete decisions are made when information has accumulated up to some threshold.  It’s just not always easy to tell what our thresholds are.

References

Stevenson PA, & Rillich J (2012). The decision to fight or flee – insights into underlying mechanism in crickets. Frontiers in neuroscience, 6 PMID: 22936896

Photo from