Using a new imaging technique called Arc catFISH, researchers from the University of Washington have visualized individual neurons in the amygdalas of rat brains that are activated when the animals are given an associative learning task.
Associative, or Pavlovian, conditioning is a fundamental form of learning throughout the animal kingdom and is a widely researched model for studying plasticity, or how the circuits in the brain can change as a result of experience, said Ilene Bernstein, senior author of a new study and a UW professor of psychology.
… In the study thirsty rats were allowed to drink the saccharine solution for five minutes. After 25 minutes they were injected with lithium chloride which caused nausea and then five minutes later they were killed. Slices of the animals brain were examined under a microscope. The imaging technique showed that some neurons were activated by the saccharine or the conditioned stimulus and others were activated by the lithium chloride or the unconditioned stimulus. In addition a small number of neurons were activated by both stimuli. “We believe that within any given learning trial the number of neurons activated by both conditioned and unconditioned stimuli is likely to be very sparse ” said Bernstein. “In the area we looked at only about 4 percent of about 300 neurons show this response.” In a follow-up experiment the researchers reversed the order of the stimuli – giving the injection first and the saccharine later. Reversing the order of stimuli is a procedure known to be ineffective in producing learning. Under these conditions and although animals were exposed to identical stimuli convergent neurons were not activated. Bernstein and her colleagues also proposed a model that associative learning takes place when a conditioned stimulus is followed by an unconditioned stimulus triggering convergent neurons. To further explore this model they plan to use the imaging technique and fear learning.
Could someone explain to me how what was learned here was worth tormenting and then killing rats? What about a PET scan?