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FINAL DRAFT

Allen 1 In the biological world, instinct is a phenomenon that causes organisms to exhibit certain behaviors without having learned or experienced them. These innate behaviors are caused by a complex variety of factors including genes, neural pathways, the limbic system, chemicals, and the environment. Over time, instincts have evolved to fit the needs of different organisms. Because instinct can be a genetic factor, innate behaviors are heritable as well as an evolutional aspect of an organism’s history (Axel, et al 1984). Genes are able to affect innate behavior through the specification of how the limbic system and neural pathways are set up. These genes also are involved with instincts because of the relationship that genes have with various chemicals or hormones that are released into organisms (Verplanck, et al 1955). These chemicals can have a more direct effect on neural pathways (Sokolowski, et al 2012). Having a focus on the genetic portion of innate behavior is also having a focus on microevolution. Another entity is macroevolution, which provides more of a big picture. In a more broad sense, natural selection is the mechanism of evolution that instinct is often affected by. There are various examples of instinct in the natural world that demonstrate either microevolution or macroevolution. Innate behavior has been studied for long periods time, papers were published as early as the 1930s on the topic of innate circuitry. It was originally thought that innate behavior originated only from the subcortical regions of the brain. An early paper published by Frank Beach in 1937 examined maternal behavior in mice, and the ability of the mother to adapt to various environments that challenged the well being of her offspring. Beach’s experiments tied this innate behavior to the cerebral cortex and the Allen 2 cerebrum, showing that more brain parts are involved in these complex behaviors. Maternal instincts were more complex than the scientific community originally thought (Beach, et al 1937). Though this journal was published 77 years ago, it shows some of the early ideas that the scientific community had about this field. About twenty years later, Julian Jaynes was studying imprinting--an innate behavior in which a young organism recognizes another organism or object as a parent or trusted entity. Imprinting is a complex response that involves visual, auditory, and olfactory cues in the environment surrounding an organism. In some cases, imprinting attaches an offspring to its parent, which is a reproductive benefit to offspring survival (Jaynes, et al 1957). If an offspring has attachment to a parent, it is more likely to stay nearby under parental protection. Attached offspring are also more likely to learn from a parental figure when interacting that closely. Reproductive benefits are a driving force behind natural selection. Environment is an important factor in how innate behavior has evolved. A hypothesis of Michael McCollough, a positive psychologist, explains that environment plays a key role in human behaviors such as forgiveness and revenge. This hypothesis theorizes that various social environments cause either forgiveness or revenge to be prevalent. McCollough relates his theory to game theory (McCollough 2010). In a tit-for-tat strategy, cooperation and retaliation are comparable to forgiveness and revenge. The choice between the two can be beneficial or detrimental depending on what the partner organism chooses. Though this psychological example of game theory does not have as directly measurable results, it provides and interesting theory of unique thought. From a Allen 3 more biological standpoint, the limbic system is the main control area for response to certain stimuli, which includes a variety of instinctual behavior. The limbic system processes external stimuli related to emotions, social activity, and motivation, which propagates a behavioral response. Some behaviors include maternal care, aggression, defense, and social hierarchy. These behaviors are influenced by sensory input—sight, sound, touch, and smell. The limbic system is comprised of a complex circuitry for innate behaviors. Katie Sokolowski studies the limbic system in relation to innate behavior in rats. Her publication explains that there are a variety of anatomical landmarks in this circuit, which include the olfactory system, olfactory cortex, amygdala, bed nucleus of stria terminalis (BNST), and hypothalamus. The olfactory system starts the circuit and detects specific chemicals that are related to innate behaviors. Two different organs in the nose, the vomeronasal organ and the main olfactory epithelium sense these chemicals and release information to the accessory and main olfactory bulbs, which process the signal. The signal can then synapse to the olfactory cortex and amygdala, which can then send the signal to the hypothalamus. The hypothalamus is where fight or flight responses originate (Sokolowski, et al 2012). This general innate circuitry in rats is evolved and developed to be extremely specific and beneficial. Within this circuit, there are various places where evolution could have taken place, or could take place in the future. For example, many rodents have receptors in the vomeronasal organ that are explicitly for predator stimuli that specifically relate to that individual species of rodent. The reception of a predatory stimulus usually creates a Allen 4 response of defense or fear (Sokolowski, et al 2012). Mating in rats follows a similar mechanism. The vomeronasal organ and the main olfactory epithelium, together called the olfactory system, detect pheromones from the opposite sex. These signals are then sent to the medial amygdala, which disperses the signal to a variety of brain parts. The pathways involved with innate circuitry are extremely specialized and specific (Sokolowski, et al 2012). Various organs and sensory receptors are involved in this complex process, and this is only in rats. These pathways are intricate and have many parts. Scientists are starting to understand what genes are necessary to normally functioning circuits, as well as understanding how pheromones and chemicals can shape these systems. Instinctual pathways are affected by both environment and genetics, therefore including approaches of macroevolution and microevolution. Chemical triggers play a main role in instinctual behaviors in many organisms. Many insects go through a sequence of ecdysis, in which the old cuticle is shed after molting occurs. This process is stimulated by ecdysis-triggering hormone, or ETH, which flows through the blood to stimulate the central nervous system. For effects to occur, the ecdysis-triggering hormone must meet an ETH receptor. These receptors express a variety of neuropeptides when activated, which causes ecdysis to continue (Kim, et al 2006). There are a huge variety of hormones in many organisms and a huge variety of organisms that exhibit innate behaviors. These hormones have evolved to have an extremely specific purpose in each individual species. Allen 5 Scientists have been able to pinpoint specific genes that are tied to certain innate behaviors. A team of scientists from Duke University was able to isolate a gene linked to sodium appetite in humans, specifically a receptor called D1(5) on the DARP-32-ARC neuron. Sodium appetite is an innate behavior that allowed human ancestors to have success in stress response, reproduction, and nutrition. This trait was selected for because it is extremely valuable to survival. Examining the molecular structure of the innate circuitry is valuable in researching evolutionary history as well as understanding instinctual behaviors (Liedtke, et al 2011). Instinct is a phenomenon that can be investigated from a multitude of angles: genetics, limbic system, nervous pathways, and environment. There are levels of insticts from molecular to groups of individuals that can be studied as well. Extremely specialized systems have evolved to create individuals who exhibit behaviors without learning them. Innate behavior is an important and interesting aspect of the biological world that people come into contact with every day.

References Axel, R., and RH Scheller. 1984. How Genes Control an Innate Behavior. Scientific 	American 3.250: 54-62. Beach, F. A., Jr. 1937. The neural basis of innate behavior. I. Effects of cortical lesions 	upon the maternal behavior pattern in the rat. Journal of comparative 	psychology p. 393. Jaynes, Julian. 1957. Imprinting: The interaction of learned and innate behavior: II. The critical period. Journal of comparative & physiological psychology 	0021-50 (1), p. 6. Kim, Young-Joon. 2006. A Command Chemical Triggers an Innate Behavior by 	Sequential Activation of Multiple Peptidergic Ensembles. Current biology 	096016 (14), p. 1395. McCullough, Michael. 2010. Beyond revenge: the evolution of the forgiveness 	instinct. The Journal of Positive Psychology. p. 97-100. Sokolowski, Katie 2012. Wired for behaviors: from development to function of 	innate limbic system circuitry. Frontiers in molecular neuroscience 1662, p. 55. Verplanck, William S. 1955. SINCE LEARNED BEHAVIOR IS INNATE, AND VICE 		VERSA, WHAT NOW?. Psychological review 0033 (2), p. 139. Wolfgang B. Liedtke, Michael J. McKinley, Lesley L. Walker, Hao Zhang, Andreas R. Pfenning, John Drago, Sarah J. Hochendoner, Donald L. Hilton, Andrew J. Lawrence, and Derek A. Denton. 2011. Relation of addiction genes to hypothalamic gene changes subserving genesis and gratification of a classic instinct, sodium appetite. 108 (30) 12509-12514.

Annotated Bibliography (9/15/2014)

Axel, R., and RH Scheller. "How Genes Control an Innate Behavior." Scientific American 3.250 (1984): 54-62. --This article focuses on the genes related to innate behavior. Snails were the focus of the research done, due to their simple central nervous systems. The gene that is correlated with Egg Laying Hormone in snails was isolated using a series of techniques, and it was studied to find out its amino acid sequence and peptide association. The researchers tied these neuropeptides to behaviors, and explains how the variance in neuropeptides allows them to affect various behaviors.

Beach, F. A., Jr. (1937). "The neural basis of innate behavior. I. Effects of cortical lesions upon the maternal behavior pattern in the rat.". Journal of comparative psychology (1921) (0093-4127), 24 (3), p. 393. --This article studies the pattern of maternal behavior and how it is affected by cortical lesions on the cerebrum. The results showed that impairment of the cerebrum affected the patterns of this behavior.

Jaynes, Julian (1957). "Imprinting: The interaction of learned and innate behavior: II. The critical period.". Journal of comparative & physiological psychology (0021-9940), 50 (1), p. 6. --This article discusses the critical period in which a bird experiences neonate imprinting, and at what age this phenomena occurs.

Kim, Young-Joon (07/2006). "A Command Chemical Triggers an Innate Behavior by Sequential Activation of Multiple Peptidergic Ensembles". Current biology (0960-9822), 16 (14), p. 1395. --This article explains the innate behavior of ecdysis in insects, and how ecdysis triggering hormone (ETH) activates this innate behavior. It also identifies the roles of neurons and neuropeptides in the

Sokolowski, Katie (2012). "Wired for behaviors: from development to function of innate limbic system circuitry". Frontiers in molecular neuroscience (1662-5099), 5, p. 55. --This article explains the brain parts involved in innate circuitry. The structures include the main and accessory olfactory system, olfactory/piriform cortex, amygdala, bed nucleus of stria terminalis (BNST) and hypothalamus. Many innate behaviors are named, such as fear, rewards, aversion, attraction, and preference. Sokolowski discusses the pathway of a response in detail, outlining the functions of each organ. The article also outlines various innate behaviors and the neurological reactions and responses to each one.

Verplanck, William S. (1955). "SINCE LEARNED BEHAVIOR IS INNATE, AND VICE VERSA, WHAT NOW?". Psychological review (0033-295X), 62 (2), p. 139. --This article discusses ethology--the science of behavior. It also examines innate vs acquired behavior.

PROJECT PART 2:

https://en.wikipedia.org/wiki/Instinct

Instinct

3 ways the article could be improved:

1. The article could add more depth to the brain pathway involved in an instinctual response. 2. The article could use more scientific examples of instinctual maturation in the section "Maturational Instincts". 3. The article could add more examples of studies to the "History: In Biology" section.

In rats, it has been observed that innate responses are related to specific chemicals, and these chemicals are detected by two organs located in the nose: the vomeronasal organ (VNO) and the main olfactory epithelium (MOE). [2]

Sokolowski, Katie (2012). "Wired for behaviors: from development to function of innate limbic system circuitry". Frontiers in molecular neuroscience (1662-5099), 5, p. 55.