Psychology lab. Psychology Research Paper. Assignment

T’maze study
B00658803
Binghamton University
Abstract
The study looked at the relative effect of scopolamine and donezepil on rat memory, indicated by the prevalence of spontaneous alternation in T-maze trials. Extant research has demonstrated a link between the degeneration of cholinergic neurons and a decrease in acetylcholine, which has been tied to the effectiveness of memory in early Alzheimer’s patients. By comparing the effect of these drugs on spontaneous alternation across three trials (including a saline placebo), the researchers were able to reproduce earlier results about the relative effect of each drug. Secondary analysis was also conducted in order to determine the effect (if any) the sex of the subjects had of the drugs’ effectiveness. 
“Memory” actually refers to multiple related (but distinct) functions of the brain and developing effective treatments for memory-related illnesses such as Alzheimer’s disease means teasing out the way different structures in the brain are related to different memory functions (Haynes IV, Frith, Sng, & Loprinzi, 2019). Episodic memories, which are memories of specific events stored in long-term memory, are known to be tied to the medial temporal lobe system. Implicit memory tied to motor skills and repetition-often known colloquially as “muscle memory”-is dependent on the striatum and basal ganglia (Loprinzi, Blough, Crawford, Ryu, Zou, & Li, 2019). Short-term memory is based in the frontal lobe and is memory that is only held in the mind actively before being lost. Humans use all of these different kinds of memory in conjunction on a daily basis, but Alzheimer’s disease hinders both short-term and episodic memory (Rugg & Vilberg, 2013; Yonelinas, Ranganath, Ekstrom, & Wiltgen, 2019). The early stages of the disease disrupt short-term memory, leading to confusion and people struggling to complete complex tasks, and as it progresses people can begin to lose their longer-term memory and recollections of specific events.
Previous studies also show that spatial memory is impaired in AD, as established through memory for scenes and learning tasks (Bird, Chan, Hartley, Pijnenburg, Rossor, & Burgess, 2010). AD results in impairment of both egocentric and allocentric spatial memory, and one of the studies found out that AD subjects are more impaired when an allocentric wayfinding strategy is used than when an egocentric one is used, probably due to the retrosplenial cortex being damaged Pengas, Patterson, Arnold, Bird, Burgess, & Nestor, 2010. Further, structure-function studies show there is a relationship between the performance of spatial memory and hippocampal volumes, and AD and MCI patients having a positive correlation (Moodley, Minati, Contarino, Prioni, Wood, Cooper, & Chan, 2015). Therefore, spatial memory is negatively affected by Alzeheimer’s since it causes shrinking of the brain.
Recent research used magnetic resonance imaging (MRI) to examine the relationship between Alzheimer’s effects on particular anatomy of the brain and the chemical changes these effects produce(Schmitz et al, 2018). Specifically, building on evidence that the cholinergic neurons of the basal forebrain are particularly susceptible to the early effects of Alzheimer’s, the researchers demonstrated not only that these neurons do indeed experience severe damage as Alzheimer’s progresses, but that this damage correlated with a decrease in acetylcholine across the brain. According to Paula and RareЕџ (2014), acetylcohline was already known to be an important neurotransmitter, tied to both the proper functioning of muscles and the rest cycles of the body’s organs.
A study in 2015 using rats in a T-maze spontaneous alternation test demonstrated that acetylcholine is also tied to memory (Newman & Gold, 2015). “Spontaneous alternation” is a term to describe behavior observed in rats (and other animals, including humans) that consists of recalling an earlier choice in order to choose the alternative when given a second opportunity (Deacon & Rawlins, 2006). When placed in a T-maze and encouraged to forage for food, a rat will remember which arm of the T it has previously searched and choose the alternative if possible. The researchers found that injecting the rats with scopolamine, which blocks acetylcholine receptors (Newman & Gold, 2015, p. 928), decreased their spontaneous alternation, demonstrating the importance of acetylcholine in spatial memory. These discoveries help lead to the development of drugs for treating early Alzheimer’s – including rivastigmine, galantamine, and donezepil – that bind to the enzyme acetylcholinesterase and block it from turning acetylcholine into inactive choline.
However, because these drugs only treat the acetylcholine deficiency produced as a result of basal forebrain degeneration and not the degeneration itself, they can only improve the memory of people experiencing early Alzheimer’s and not stop the progression of the disease itself. This indicates that further research is needed into the relationship between acetylcholine and Alzheimer’s disease. This study combined the insights of Newman and Gold alongside Schmitz et al’s investigation into the degeneration of cholinergic neurons of the basal forebrain to examine the comparative effects of drugs that increase or decrease the amount of acetylcholine in rat brains by testing their spontaneous alternation in a cross-shaped T-maze, with the expectation that the experiment should support the findings of existing research.
The rationale for this study is based in the need for the robust replication of experimental results, so the experiment examined the effects of both scopolamine (an acetylcholine antagonist) and donezepil, a common drug for the treatment of acetylcholine deficiency in early Alzheimer’s patients in the same population of rats. Considering both variables in one experiment had the benefit of checking previous work for reproducibility while allowing researchers to directly compare the effects of bo...