Showing 11 - 20 of 116 Items
Combining behavior and EEG to study the effects of mindfulness meditation on episodic memory
Date: 2020-05-01
Creator: Erika Nyhus, William A. Engel, Tomas Donatelli Pitfield, Isabella M.W. Vakkur
Access: Open access
- Although there has been recent interest in how mindfulness meditation can affect episodic memory as well as brain structure and function, no study has examined the behavioral and neural effects of mindfulness meditation on episodic memory. Here we present a protocol that combines mindfulness meditation training, an episodic memory task, and EEG to examine how mindfulness meditation changes behavioral performance and the neural correlates of episodic memory. Subjects in a mindfulness meditation experimental group were compared to a waitlist control group. Subjects in the mindfulness meditation experimental group spent four weeks training and practicing mindfulness meditation. Mindfulness was measured before and after training using the Five Facet Mindfulness Questionnaire (FFMQ). Episodic memory was measured before and after training using a source recognition task. During the retrieval phase of the source recognition task, EEG was recorded. The results showed that mindfulness, source recognition behavioral performance, and EEG theta power in right frontal and left parietal channels increased following mindfulness meditation training. In addition, increases in mindfulness correlated with increases in theta power in right frontal channels. Therefore, results obtained from combining mindfulness meditation training, an episodic memory task, and EEG reveal the behavioral and neural effects of mindfulness meditation on episodic memory.
Increases in Theta Oscillatory Activity During Episodic Memory Retrieval Following Mindfulness Meditation Training
Date: 2019-09-04
Creator: Erika Nyhus, William Andrew Engel, Tomas Donatelli Pitfield, Isabella Marie Wang Vakkur
Access: Open access
- Mindfulness meditation has been shown to improve episodic memory and increase theta oscillations which are known to play a role in episodic memory retrieval. The present study examined the effect of mindfulness meditation on episodic memory retrieval and theta oscillations. Using a longitudinal design, subjects in the mindfulness meditation experimental group who underwent 4 weeks of mindfulness meditation training and practice were compared to a waitlist control group. During the pre-training and post-training experimental sessions, subjects completed the Five Facet Mindfulness Questionnaire (FFMQ) and studied adjectives and either imagined a scene (Place Task) or judged its pleasantness (Pleasant Task). During the recognition test, subjects decided which task was performed with each word (“Old Place Task” or “Old Pleasant Task”) or “New.” FFMQ scores and source discrimination were greater post-training than pre-training in the mindfulness meditation experimental group. Electroencephalography (EEG) results revealed that for the mindfulness meditation experimental group theta power was greater post-training than pre-training in right frontal and left parietal channels and changes in FFMQ scores correlated with changes in theta oscillations in right frontal channels (n = 20). The present results suggest that mindfulness meditation increases source memory retrieval and theta oscillations in a fronto-parietal network.
Genome-wide single-nucleotide polymorphism map for Candida albicans
Date: 2004-06-01
Creator: Anja Forche, P. T. Magee, B. B. Magee, Georgiana May
Access: Open access
- Single-nucleotide polymorphisms (SNPs) are essential tools for studying a variety of organismal properties and processes, such as recombination, chromosomal dynamics, and genome rearrangement. This paper describes the development of a genome-wide SNP map for Candida albicans to study mitotic recombination and chromosome loss. C. albicans is a diploid yeast which propagates primarily by clonal mitotic division. It is the leading fungal pathogen that causes infections in humans, ranging from mild superficial lesions in healthy individuals to severe, life-threatening diseases in patients with suppressed immune systems. The SNP map contains 150 marker sequences comprising 561 SNPs and 9 insertions-deletions. Of the 561 SNPs, 437 were transition events while 126 were transversion events, yielding a transition-to-transversion ratio of 3:1, as expected for a neutral accumulation of mutations. The average SNP frequency for our data set was 1 SNP per 83 bp. The map has one marker placed every 111 kb, on average, across the 16-Mb genome. For marker sequences located partially or completely within coding regions, most contained one or more nonsynonymous substitutions. Using the SNP markers, we identified a loss of heterozygosity over large chromosomal fragments in strains of C. albicans that are frequently used for gene manipulation experiments. The SNP map will be useful for understanding the role of heterozygosity and genome rearrangement in the response of C. albicans to host environments.
The parasexual cycle in Candida albicans provides an alternative pathway to meiosis for the formation of recombinant strains
Date: 2008-05-01
Creator: Anja Forche, Kevin Alby, Dana Schaefer, Alexander D. Johnson, Judith, Berman, Richard J. Bennett
Access: Open access
- Candida albicans has an elaborate, yet efficient, mating system that promotes conjugation between diploid a and α strains. The product of mating is a tetraploid a/α cell that must undergo a reductional division to return to the diploid state. Despite the presence of several "meiosis-specific" genes in the C. albicans genome, a meiotic program has not been observed. Instead, tetraploid products of mating can be induced to undergo efficient, random chromosome loss, often producing strains that are diploid, or close to diploid, in ploidy. Using SNP and comparative genome hybridization arrays we have now analyzed the genotypes of products from the C. albicans parasexual cycle. We show that the parasexual cycle generates progeny strains with shuffled combinations of the eight C. albicans chromosomes. In addition, several isolates had undergone extensive genetic recombination between homologous chromosomes, including multiple gene conversion events. Progeny strains exhibited altered colony morphologies on laboratory media, demonstrating that the parasexual cycle generates phenotypic variants of C. albicans. In several fungi, including Saccharomyces cerevisiae and Schizosaccharomyces pombe, the conserved Spo11 protein is integral to meiotic recombination, where it is required for the formation of DNA double-strand breaks. We show that deletion of SPO11 prevented genetic recombination between homologous chromosomes during the C. albicans parasexual cycle. These findings suggest that at least one meiosis-specific gene has been re-programmed to mediate genetic recombination during the alternative parasexual life cycle of C. albicans. We discuss, in light of the long association of C. albicans with warm-blooded animals, the potential advantages of a parasexual cycle over a conventional sexual cycle. © 2008 Forche et al.
An information theoretical approach to task-switching: Evidence from cognitive brain potentials in humans
Date: 2008-03-28
Creator: Francisco Barceló, José A. Periáñez, Erika Nyhus
Access: Open access
- This study aimed to clarify the neural substrates of behavioral switch and restart costs in intermittently instructed task-switching paradigms. Event-related potentials (ERPs) were recorded while participants were intermittently cued to switch or repeat their categorization rule (Switch task), or else they performed two perceptually identical control conditions (NoGo and Oddball). The three tasks involved different task-sets with distinct stimulus-response associations in each, but identical visual stimulation, consisting of frequent colored shapes (p = 0.9) and randomly interspersed infrequent black shapes (p = 0.1; '+' and 'x' symbols). Behavioral restart costs were observed in the first target responses following all black shapes in the Switch and NoGo tasks - but not in the Oddball task - and corresponded with enhanced fronto-centrally distributed early cue-locked P3 activity (peak latency 325-375 ms post-cue onset at the vertex). In turn, behavioral switch costs were associated with larger late cue-locked P3 amplitudes in the Switch task only (peak latency 400-450 ms post-cue onset at mid-parietal sites). Together with our information theoretical estimations, ERP results suggested that restart and switch costs indexed two neural mechanisms related to the preparatory resolution of uncertainty: (1) the intermittent re-activation of task-set information, and (2) the updating of stimulus-response mappings within an active task set, as indexed by early and late cue-locked P3 activations, respectively. In contrast, target-locked P3 activations reflected a functionally distinct mechanism related to the implementation of task-set information. We conclude that task-switching costs consist of both switch-specific and switch-unspecific processes during the preparation and execution stages of task performance. © 2008 Barceló, Periáñez and Nyhus.
Characterizing Toll Receptors in the Mediterranean Cricket Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2025-06-01
Date: 2022-01-01
Creator: Warsameh Bulhan
Access: Access restricted to the Bowdoin Community
Rhythmic behaviors: Understanding neuromodulation at the neuromuscular level
Date: 2023-01-01
Creator: Kenneth Garcia
Access: Open access
- Neuromodulation allows for the flexibility of neural circuit dynamics and the outputs they produce. Studies of the stomatogastric nervous system (STNS) have expanded our knowledge on the actions of neuromodulators, small molecules that most often activate G-protein coupled receptors and reconfigure circuit activity and composition. In these systems, modulation has been found to occur at every level, from sensory-motor coupling to neuromuscular transmission (Harris-Warrick and Marder 1991). Neuromodulators have complex effects on motor output; they can alter the firing of individual neurons while also modulating muscle properties, neuromuscular transmission, and sensory neuron response to muscle activity (Fort et al. 2004). We investigated this further by recording the motor output produced by the gastric mill rhythm of the lobster STNS under neuromodulator conditions. How is this neuromuscular system as a whole modulated to produce motor flexibility? We hypothesized that these neuromodulators act on individual receptors of component neurons of central pattern generator (CPG)-effector system themselves and at the periphery, coordinately altering muscle contraction by altering all levels of the crustacean neuromuscular system. Application of NRNFLRFamide, RPCH, oxotremorine, and proctolin to the gastric mill 4 (gm4) muscles of the Cancer crab showed that neuromodulators that have been found to have variable, yet significant effects on the activity of the neurons of the STNS directly alter the activity of the gm4 muscles as well, suggesting that coordination of peripheral actions and direct neuronal modulation regulates patterned motor output.
The Impact of Toll 6-1 Function on the Maintenance and Plasticity of the Gryllus bimaculatus Auditory System Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2028-06-01
Date: 2023-01-01
Creator: Jada Scotland
Access: Access restricted to the Bowdoin Community
Characterizing the Roles of Toll7 in the Gryllus Bimaculatus Peripheral Nervous System Development
Date: 2023-01-01
Creator: Rowland Luo
Access: Open access
- The study of neuronal development could provide foundational information on neurogenesis and neuroplasticity. The small size and relatively simple nervous system of Orthoptera make them ideal models for neurodevelopmental studies. The peripheral nervous system development is an intricate and precise process that each sensory neurons are able to reach their central nervous system partners in a relatively short amount of time. Although the peripheral nervous system in limb buds and their genetic regulations are well understood in grasshopper embryos, few studies have explored the developing nervous system in a cricket model. Therefore, the first goal of the current experiment is to characterize the normal peripheral nervous system development in cricket embryos. Previous studies in Drosophila have suggested Toll6 and Toll7 receptors could serve as important targets for the neurotrophic-like factors Spaetzle2 and 5. Malfunctioning neurotrophic pathways could lead to abnormal nervous system development. Therefore, the second goal of the current study is to explore the roles of Toll7 in the development of the cricket peripheral nervous system. Immunohistochemical staining using anti-horseradish peroxidase (Anti-HRP) was used to illustrate crickets' embryonic developing peripheral nervous system in the limb buds from developmental stage 7.0 to 11.0. Cricket eggs were injected with Toll7 double stranded RNA (dsRNA) and rhodamine dye to suppress the Toll7 mRNA level. The control eggs were injected with GFP dsRNA and rhodamine dye. The peripheral nervous system development in cricket embryos is largely homologous to that observed in grasshopper embryos. All later-emerged sensory neurons followed the pathway established by the first pioneer neuron Ti1. Ti1 made stereotypical turns following the steering signals on epithelial and guidepost cell surfaces and eventually fasciculate with lateral motor axons from the central nervous system. When examining the peripheral nervous system development with Toll7 knockdown, a decrease in limb bud volume was observed at stage 7.7 and stage 8.0, suggesting Toll7’s potential roles in aiding cell-cell intercalation processes in Orthoptera embryos. Furthermore, a delay in Ti1 pioneer neuron development was observed with Toll7 knockdown at early developmental stages, providing evidence for Toll-Spaetzle pathway’s neurotrophic-like functions. The results of the current experiment provide the first description of the peripheral nervous system development in the cricket limb buds and further evidence of Toll-Spaetzle pathway’s neurotrophic properties.
Co-modulation of the Pyloric Circuit in the Stomatogastric Nervous System of the
Cancer Borealis
Date: 2025-01-01
Creator: Margaret Broaddus
Access: Open access
- ABSTRACT CHAPTER I: All nervous systems are influenced by circulating hormones, which can modulate neural circuits to produce different outputs from the same set of neurons. Invertebrate models, particularly crustaceans, serve as excellent models for studying neuromodulation because they contain neural circuits that continue to generate fictive activity when dissected out of the animal. The stomatogastric nervous system (STNS) of the Jonah Crab (Cancer borealis) has long been used to study neuromodulation due to its well-characterized circuits. Even in such a compact neural network, little is known about how these circuits are modulated, and this remains a question in all animals, particularly in humans. Here we investigated the modulation of the pyloric circuit by applying bulk hemolymph to the dissected STNS preparation. The hemolymph contains all of the circulating modulators, some of which have known effects on the pyloric rhythm (though many are still unknown). Interestingly, when hemolymph is applied to the isolated STNS, the pyloric rhythm is suppressed. This is surprising given that in vivo the STNS is continually exposed to hemolymph (the STG is situated within an artery, and thus, exposed to circulating hemolymph) and the pyloric rhythm is constitutively active. Therefore, I hypothesized that there are synaptically released neurotransmitters that excite the pyloric rhythm. To test this hypothesis, we applied three different excitatory modulators – proctolin, serotonin, and oxotremorine – separately in the presence of hemolymph. I found that proctolin and oxotremorine restore the pyloric rhythm in the presence of hemolymph. However, serotonin did not consistently overcome the inhibition of hemolymph. ABSTRACT CHAPTER II: A plethora of work has begun to identify how endogenous neural and hormonal modulators interact to influence the pyloric network. Here we examined the modulation of the stomatogastric nervous system (STNS) via two excitatory endogenous modulators CabTRP Ia and corazonin. CabTRP Ia and corazonin both excite the pyloric rhythm, but in distinct ways. Preliminary data by Nusbaum and Christie from 2003 suggested that an initial corazonin application gated a stronger response to subsequent CabTRP Ia when compared the inverse application of these neuromodulators. We sought to validate this gating phenomenon, but found no significant difference between the effects of the first and second applications of CabTRP Ia. Given that these animals are wild caught and surviving in a changing oceanic environment, it is possible that this modulatory effect in the Jonah Crab has changed over the last few decades due to environmentally driven shifts in receptor expression and channel conductances.