From pages 27 to 30, David Shenk describes an experiment in which rats are tested in mazes to determine whether it is due to genetics that rats are "Maze-bright" or "Maze-dull". He describes how the results were more effected by the environment the rats grew up in (when not exposed to a normal, moderately stimulating environment) saying how "The truth was that these original 'genetic' differences hadn't really ever been purely genetic. Rather, they had been a function of each strain's GxE development within its original environment" (Shenk 30). The behaviors of the rats shows the effect on how the rats learn to better navigate these mazes and how the environment they grew up in has a large impact on their success. Describe the type of learning these rats are performing and how it is that the environment in which the rats were raised in affected the ways in which they learned. Use the descriptions of different learning methods in chapter 51 section 2 of Campbell to aid in your explanation.
-Kyle Nelson (kynels21@gmail.com)
Over the course of the rat gene-environment interaction experiment conducted by Cooper and Zubek in 1958, it was concluded that the environment in which the rats were raised was the decisive factor in the rats’ abilities to navigate the maze. While maze-bright rats outperformed maze-dull rats when raised under normal environments, both lineages of rats performed almost identically upon being raised under enriched and restricted environments. Such results indicate that upon being subjected to radical external stimuli (restricted and enriched), the environment played a larger role in determining maze intelligence than genetics, since “The more complex the trait [such as navigating a complex maze], the farther any one gene is from direct instruction” (26). As described in Shenk’s GxE model, while both genetics and the environment interact to determine the intelligence of an organism, more complicated behaviors have a greater correlation to the environment than to individual genes (and in the case of the mice, genetic composition as a whole). However, the drastically fewer number of errors made by maze-bright rats than maze-dull rats upon being raised in normal environments indicates that genes do have a notable impact on intelligence as well, since the genetic differences in their predecessors was the only significant distinction between the two lines of rats.
ReplyDeleteIn order to solve the mazes most efficiently, the rats relied more heavily upon the external stimuli of which they were raised rather than their genetic composition, as described above. The environmental conditions in which the rats were raised directly led to several behavioral adaptations that furthered the rats’ capabilities to solve the maze. Most likely, upon being subjected to enriched environments featuring stimulating and interactive tools, slightly complex spacing, and distinctive coloring, the rats were able to enhance their capability for spatial learning, which is “the establishment of a memory that reflects the environment’s spatial structure” (Campbell 1126). With an enhanced ability to both develop spatial relationships and establish cognitive maps within the maze, rats raised in an enriched environment would be subject to make fewer errors. In addition, the rats raised in enriched environments displayed high levels of cognition, the mental capability of displaying awareness, reasoning, recollection, and judgment. The mazes to which they were subjected to forced them to display high degrees of problem solving, the cognitive activity of progressing from one state to another upon being faced with obstructions. Thus, the potential for rats to develop strong cognition and problem solving capabilities is primarily linked to external stimuli, and only slightly to genetics.
A means of solving the mazes which possibly could be attributed to genetics is Theta Rhythm in the hippocampus, electrical oscillations transmitted from the hippocampus and other regions of the brain in several species of mammals, including rats. The relationship between Theta Rhythm and the ability for rats to track their own location was the subject of research in a study published in the journal Science in April 2011. The researchers proposed that the projection of these oscillations enabled the rats to develop spatial representations of the environment via a special type of neuron called a grid cell, secreted upon each oscillation of a Theta Rhythm. Despite lack of full understanding of the process, manipulation of Theta Rhythm via electrical pulses in a rat was proven to have negative effects on the ability to recall the location of prior events. As such, the extent to which Theta Rhythms can help induce spatial representations in a rat’s brain is a means that may be controlled via genetics and can possibly be a reason why maze-bright and maze-dull rats (enriched environment) differed slightly in capability to complete the maze and why maze-bright and maze-dull rats (normal environment) differed significantly in capability to complete the maze.
Nick Sotos (nsotos13@gmail.com)