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- Creators: Arizona State University
Description
Specific dendritic morphologies are a hallmark of neuronal identity, circuit assembly, and behaviorally relevant function. Despite the importance of dendrites in brain health and disease, the functional consequences of dendritic shape remain largely unknown. This dissertation addresses two fundamental and interrelated aspects of dendrite neurobiology. First, by utilizing the genetic power of Drosophila melanogaster, these studies assess the developmental mechanisms underlying single neuron morphology, and subsequently investigate the functional and behavioral consequences resulting from developmental irregularity. Significant insights into the molecular mechanisms that contribute to dendrite development come from studies of Down syndrome cell adhesion molecule (Dscam). While these findings have been garnered primarily from sensory neurons whose arbors innervate a two-dimensional plane, it is likely that the principles apply in three-dimensional central neurons that provide the structural substrate for synaptic input and neural circuit formation. As such, this dissertation supports the hypothesis that neuron type impacts the realization of Dscam function. In fact, in Drosophila motoneurons, Dscam serves a previously unknown cell-autonomous function in dendrite growth. Dscam manipulations produced a range of dendritic phenotypes with alteration in branch number and length. Subsequent experiments exploited the dendritic alterations produced by Dscam manipulations in order to correlate dendritic structure with the suggested function of these neurons. These data indicate that basic motoneuron function and behavior are maintained even in the absence of all adult dendrites within the same neuron. By contrast, dendrites are required for adjusting motoneuron responses to specific challenging behavioral requirements. Here, I establish a direct link between dendritic structure and neuronal function at the level of the single cell, thus defining the structural substrates necessary for conferring various aspects of functional motor output. Taken together, information gathered from these studies can inform the quest in deciphering how complex cell morphologies and networks form and are precisely linked to their function.
ContributorsHutchinson, Katie Marie (Author) / Duch, Carsten (Thesis advisor) / Neisewander, Janet (Thesis advisor) / Newfeld, Stuart (Committee member) / Smith, Brian (Committee member) / Orchinik, Miles (Committee member) / Arizona State University (Publisher)
Created2013
Description
The benefits of exercise have been recommended in typical and other special populations. However, the evidence for persons with Down syndrome (DS) is still limited. This study was aimed at investigating the impact of an acute bout of aerobic exercise intervention on motor performance, executive function and intrinsic motivation in adolescents and young adults with DS. Ten participants with DS were assigned to an exercise group, who walked on a incremental treadmill protocol for 20 minutes. The exercise intensity was achieved at 66% of their predicted maximum heart rate. Another ten participants with DS were assigned to an attentional control group, who watched a video for 20 minutes. Measures of fine manual dexterity (e.g., Purdue Pegboard test), manual force production (e.g., grip strength test), processing speed (e.g., visual choice reaction time test), verbal processing (e.g., verbal fluency test), attention shifting ability (e.g., The Dimensional Card sorting test), and inhibitory control (e.g., Knock and Tap test) were tested pre and post intervention. An intrinsic motivation scale (e.g., enjoyment and effort) was conducted after the intervention. First, results showed participants significantly improved their performance in manual force production and Knock and Tap Test after the exercise intervention. While it has been proposed that exercise increases arousal status, neurotransmitters, or cerebral vasculature, the exact mechanisms in persons with DS are still unknown. However, our results showed that after treadmill walking, motor and cognitive improvements can be found in individuals with DS, even in a single exercise session. In addition, participants reported higher scores in enjoyment after video viewing than exercise, which may a result from musical effect or too much emphasis on external rewards in their early participation in exercise. These may imply that participants had low intrinsic motivation to an active lifestyle. Further, scores in effort were significantly higher after exercise than video viewing, which indicated their capabilities to perceive their physical exertion. However, other motivational regulations (e.g., introjected and identified regulations) have shown the relationship with exercise behavior in this population. Thus, further study should consider divergent motivational factors in order to implement an effective exercise program.
ContributorsChen, Chih-Chia (Author) / Ringenbach, Shannon D.R. (Thesis advisor) / Crews, Debra (Committee member) / Kulinna, Pamela (Committee member) / Amazeen, Eric (Committee member) / Arizona State University (Publisher)
Created2013
Description
This study examines the effectiveness of two modes of exercise on self-efficacy (SE) in adolescents with Down syndrome (DS). Thirty-nine participants were randomly divided into a voluntary cycling group (VC) (i.e., self-selected cadence), an assisted cycling group (ACT) (i.e., at least 30% faster than self-selected cadence accomplished by a motor), or a no exercise group (NC). In each cycling intervention the participant completed 30 minute cycling sessions, three times per week for a total of eight weeks. Two subsets of the Physical Activity and Self Efficacy Survey were administered prior to cycling (i.e., pretest) and after the eight week intervention (i.e., post-test). The results were consistent with the hypothesis that self-efficacy would improve after ACT, however there was not improvement after the VC condition as hypothesized. It was also hypothesized that exercise perception would improve following the ACT intervention; execise perception showed a trend of improvement after ACT, but the data did not reach significance. Limitations include the wide variability of the DS population. This limitation is responsible for the variation in mental age seen in the intervention groups and could be responsible for the non-significance of the exercise perception data. To generalize our results for parents, therapists, teachers, etc., our recommendation is for persons with DS to participate in physical activity that is easy for them at first \u2014 a simplified sport or active game, assisted cycling, brisk walking \u2014 so that they have a positive experience with exercise. Showing individuals with DS that they can be proficient exercisers will likely improve their self-efficacy and motivate them to engage in more PA over time. In conclusion, eight weeks of moderate ACT exercise demonstrated a significant trend for improved self-efficacy in adolescents with DS.
ContributorsWallace, Kellie Carter (Author) / Ringenbach, Shannon (Thesis director) / Youngstedt, Shawn (Committee member) / Hoffner, Kristin (Committee member) / School of Nutrition and Health Promotion (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12
Description
Background: Down syndrome is the leading genetic cause of intellectual disabilities. Executive function is an area that people with Down syndrome have a diminished capacity compared to those in the general population. In recent years it has been determined that acute and chronic exercise has a small but positive effect on measures of executive function in typically developed individuals. The effect has been recorded separately in both aerobic, high-rate passive and resistance exercises in adolescents with DS but has not been compared between exercise types in adults with DS. Methods: A randomized crossover study was utilized to determine the effect of resistance exercise, assisted cycling therapy, and no exercise on executive function and enjoyment in adults with Down syndrome. Resistance Training (RT)- participants completed a total of 16- repetitions of approximately 75% of a 1-RM in the leg press, chest press, seated row, and latissimus pulldown. ACT- participants completed 30-minutes of cycling at 35% above voluntary (e.g., self-selected pace) rate. No-Training (NT)- participants spent 35-minutes playing board games. Cognitive assessments were recorded pre- and post- intervention. The Physical Activity Enjoyment Survey was collected post-intervention. Statistics: The cognitive measures and Physical Activity Self-efficacy scale were analyzed using the delta scores (pre-post) in a Linear mixed models analyais. The main effect of sequence (A, B, C) and intervention (RT, ACT, NT), and visit were assessed. Significance level was set with α=0.05. If any differences were detected, the Bonferroni post-hoc test was used to determine differences. Physical Activity Enjoyment Scale post scores were compared using a General Linear Model. Alpha was set at 0.05 with a Bonferroni post-hoc test to determine differences. A secondary analysis was conducted investigating the effect of participants that completed testing individually compared to those that completed the testing in a group setting. Results: There were no significant difference in the delta score of any of the measures. The secondary analysis also found no significant difference but showed a trend that those tested individually had opposite results than those tested in a group.
ContributorsArnold, Nathaniel (Author) / Ringenbach, Shannon (Thesis advisor) / Lee, Chong (Committee member) / Der Ananian, Cheryl (Committee member) / Holzapfel, Simon (Committee member) / Bosch, Pamela (Committee member) / Arizona State University (Publisher)
Created2021