Neuroscience and Neurobiology Commons^™

Effects Of Dip-Coated Films On The Properties Of Implantable Intracortical Microelectrodes, Salah Sommakia

Open Access Dissertations

The successful clinical use of implantable intracortical microelectrodes (ICMs) to treat certain types of deafness, blindness, and paralysis is limited by a reactive tissue response (RTR) of the brain. This RTR culminates in the formation of a tight glial scar and a loss of neuronal density around implanted ICMs, and is accompanied by a decrease in signal to noise ratio and an increase in impedance. While no comprehensive mechanistic understanding of the underlying biology is currently agreed upon in the field, a general consensus exists around a highly volatile acute RTR phase. During this acute phase, the electrical properties of …

Smooth Muscle-Specific Removal Of Brain-Derived Neurotrophic Factor Results In Increased Vagal Afferent Innervation To The Intestine And Increased Satiation In Mice, Jessica Erin Biddinger

Open Access Dissertations

Vagal afferents transmit signals regarding food-derived stimuli in the gastrointestinal (GI) tract to the brain. Vagal mechanoreceptors called intraganglionic laminar endings (IGLEs) innervate the smooth muscle wall of GI organs and detect stretch and tension to regulate GI reflexes and satiation. Brain-derived neurotrophic factor (BDNF) is expressed in the smooth muscle of developing GI organs when vagal afferents from the nodose ganglion begin to innervate the GI tract. Therefore, it was hypothesized BDNF is necessary for development of vagal afferents that innervate this tissue. Targeted smooth muscle-specific BDNF homozygous knockout (BDNF SM -/-) mice were generated and .vagal afferent innervation …

Effects Of Hearing Aid Amplification On Robust Neural Coding Of Speech, Jonathan Daniel Boley

Open Access Dissertations

Hearing aids are able to restore some hearing abilities for people with auditory impairments, but background noise remains a significant problem. Unfortunately, we know very little about how speech is encoded in the auditory system, particularly in impaired systems with prosthetic amplifiers. There is growing evidence that relative timing in the neural signals (known as spatiotemporal coding) is important for speech perception, but there is little research that relates spatiotemporal coding and hearing aid amplification.

This research uses a combination of computational modeling and physiological experiments to characterize how hearing aids affect vowel coding in noise at the level of …

Network Structure And Dynamics Of The Mental Workspace, Alexander Schlegel, Peter J. Kohler, Sergei V. Fogelson, Prescott Alexander

Dartmouth Scholarship

The conscious manipulation of mental representations is central to many creative and uniquely human abilities. How does the human brain mediate such flexible mental operations? Here, multivariate pattern analysis of functional MRI data reveals a widespread neural network that performs specific mental manipulations on the contents of visual imagery. Evolving patterns of neural activity within this mental workspace track the sequence of informational transformations carried out by these manipulations. The network switches between distinct connectivity profiles as representations are maintained or manipulated.

Differential Joint-Specific Corticospinal Tract Projections Within The Cervical Enlargement, Curtis O. Asante, John H. Martin

Publications and Research

The motor cortex represents muscle and joint control and projects to spinal cord interneurons and–in many primates, including humans–motoneurons, via the corticospinal tract (CST). To examine these spinal CST anatomical mechanisms, we determined if motor cortex sites controlling individual forelimb joints project differentially to distinct cervical spinal cord territories, defined regionally and by the locations of putative last-order interneurons that were transneuronally labeled by intramuscular injection of pseudorabies virus. Motor cortex joint-specific sites were identified using intracorticalmicrostimulation. CST segmental termination fields from joint-specific sites, determined using anterograde tracers, comprised a high density core of terminations that was consistent between animals …

Cholinergic Enhancement Of Brain Activation In Mild Cognitive Impairment During Episodic Memory Encoding, Shannon L. Risacher, Yang Wang, Heather A. Wishart, Laura A. Rabin, Laura A. Flashman, Brenna C. Mcdonald, John D. West, Robert B. Santulli, Andrew J. Saykin

Publications and Research

Objective: To determine the physiological impact of treatment with donepezil (Aricept) on neural circuitry supporting episodic memory encoding in patients with amnestic mild cognitive impairment (MCI) using functional magnetic resonance imaging (fMRI).

Methods: Eighteen patients with MCI and 20 age-matched healthy controls (HC) were scanned twice while performing an event-related verbal episodic encoding task. MCI participants were scanned before treatment and after approximately 3 months on donepezil; HCwere untreated but rescanned at the same interval.Voxel-level analyses assessed treatment effects on activation profiles in MCI patients relative to retest changes in non-treated HC. Changes in task-related connectivity in medial temporal circuitry …

Transient And Selective Suppression Of Neural Activity With Infrared Light, Michael W. Jenkins, Hui Lu, Jeffrey M. Mcmanus, Hillel J. Chiel

Faculty Scholarship

Analysis and control of neural circuitry requires the ability to selectively activate or inhibit neurons. Previous work showed that infrared laser light selectively excited neural activity in endogenous unmyelinated and myelinated axons. However, inhibition of neuronal firing with infrared light was only observed in limited cases, is not well understood and was not precisely controlled. Using an experimentally tractable unmyelinated preparation for detailed investigation and a myelinated preparation for validation, we report that it is possible to selectively and transiently inhibit electrically- initiated axonal activation, as well as to both block or enhance the propagation of action potentials of specific …

Myelin Basic Protein And Glial Fibrillary Acidic Protein Antibodies In Autism, Edward Stevenson, Dr. Erin Bigler

Journal of Undergraduate Research

Autism is a developmental disorder. There has been an increasing trend in the diagnosis of autism in the past 15 years. After years of research there is still little agreement as to the causes of autism. It has been hypothesized that autistics could be the result of the body’s immune system attacking the brain through cytotoxicity and antibody mediated responses.2 Studies between immune factors and autism have had some interesting results, yet due to the complexities of the central nervous system and immune system, solid conclusions have not been reached.

Title, Jordan Yorgason

Journal of Undergraduate Research

We had four main objectives when I applied for the mentoring grant: to measure locomotor habituation to an environment, acoustic prepulse/startle inhibition, memory with a morris land maze, and to present findings in a neuroscience journal and on a poster for a convention. The results are as follows:

Understanding Less Than Nothing: Children's Neural Response To Negative Numbers Shifts Across Age And Accuracy, Margaret M. Gullick, George Wolford

Dartmouth Scholarship

We examined the brain activity underlying the development of our understanding of negative numbers, which are amounts lacking direct physical counterparts. Children performed a paired comparison task with positive and negative numbers during an fMRI session. As previously shown in adults, both pre-instruction fifth-graders and post-instruction seventh-graders demonstrated typical behavioral and neural distance effects to negative numbers, where response times and parietal and frontal activity increased as comparison distance decreased. We then determined the factors impacting the distance effect in each age group. Behaviorally, the fifth-grader distance effect for negatives was significantly predicted only by positive comparison accuracy, indicating that …

Visual-Motor Development In South Indian School Children: Environmental Complexity’S Relationship With Cortical Development, Christine H. Walton

Journal of Undergraduate Research

Previous neurological studies have found the degree of environmental complexity influences the acquisition and development of motor skills in human infants as well as animal models. During a critical period in human development, which is believed to span the first 6-10 years for human visual-motor development, neurons grow and solidify appropriate connections. Signals sent from cell to cell are insulated by additional protective cells in a process called myelination. These postnatal cognitive developments are influenced by sensory input and experience. It appears that deprivation of appropriate stimuli in a subject’s surroundings at this time results in decreased cognitive development as …

The Flexible Fairness: Equality, Earned Entitlement, And Self-Interest, Chunliang Feng, Yi Luo, Ruolei Gu, Lucas S. Broster, Xueyi Shen, Tengxiang Tian, Yue-Jia Luo, Frank Krueger

Behavioral Science Faculty Publications

The current study explored whether earned entitlement modulated the perception of fairness in three experiments. A preliminary resource earning task was added before players decided how to allocate the resource they jointly earned. Participants' decision in allocation, their responses to equal or unequal offers, whether advantageous or disadvantageous, and subjective ratings of fairness were all assessed in the current study. Behavioral results revealed that participants proposed more generous offers and showed enhanced tolerance to disadvantageous unequal offers from others when they performed worse than their presumed "partners," while the reverse was true in the better-performance condition. The subjective ratings also …

The Effects Of Anesthesia On Midbrain Gaba Neurons, Stuart Layton, Dr. Scott Steffensen

Journal of Undergraduate Research

Consciousness has perplexed neuroscientists for decades. What is consciousness and how is it obstructed by anesthesia? Every year doctors expose thousands of people to general anesthesia. Anesthesia does several things, it prevents the perception of pain, renders a patient unconscious, inhibits the formation of memory, and paralyzes the subject; all of which as desired during a medical procedure. The mechanism by which anesthesia accomplishes these many tasks are unknown, including its ability to render a subject unconscious. The goal of this study was to study the effects of anesthesia on -aminobutyric acid (GABA) neurons in the ventral tegmental area (VTA) …

Non-Invasive Brain Stimulation Model For Clinical Addiction Treatment, Jordan Davies, Dr. Scott Steffensen

Journal of Undergraduate Research

The goal in my proposal was to study the effects of light stimulation in human brains on the action of the neurotransmitter dopamine (DA) within the nucleus accumbens (NAc), in order to determine its efficacy as a non-invasive method for inducing long-term potentiation of dopamine neurons, restoring homeostasis, and its possible use in clinical treatment for addiction. It was dependent upon research that was being done on mice in Dr. Steffensen’s lab to determine the optimum frequency and wavelength of light stimulation to bring baseline dopamine levels back up to normal. Unfortunately, there haven’t been any conclusive results that merit …

Unconscious Priming Requires Early Visual Cortex At Specific Temporal Phases Of Processing, Marjan Persuh, Tony Ro

Publications and Research

Although examples of unconscious shape priming have been well documented, whether such priming requires early visual cortex (V1/V2) has not been established. In the current study, we used TMS of V1/V2 at varying temporal intervals to suppress the visibility of preceding shape primes while the interval between primes and targets was kept constant. Our results show that, although conscious perception requires V1/V2, unconscious priming can occur without V1/V2 at an intermediate temporal interval but not at early (5–25 msec) or later (65–125 msec) stages of processing. Because the later time window of unconscious priming suppression has been proposed to interfere …

Sensory-Specific Appetition: Postingestive Detection Of Glucose Rapidly Promotes Continued Consumption Of A Recently Encountered Flavor, Kevin P. Myers, Marisa S. Taddeo, Emily K. Richards

Faculty Journal Articles

It is generally thought that macronutrients stimulate intake when sensed in the mouth (e.g., sweet taste) but as food enters the GI tract its effects become inhibitory, triggering satiation processes leading to meal termination. Here we report experiments extending recent work (see [1]) showing that under some circumstances nutrients sensed in the gut produce a positive feedback effect, immediately promoting continued intake. In one experiment, rats with intragastric (IG) catheters were accustomed to consuming novel flavors in saccharin daily while receiving water infused IG (5 ml/15 min). The very first time glucose (16% w/w) was infused IG instead of water, …

Low-Dose Alcohol Self-Administration In Freely-Moving Rats And Its Effect On The Firing Rate Of Ventral Tegmental Area Gaba Neurons, Stuart Thomas, Dr. Scott Steffensen

Journal of Undergraduate Research

Each year, more and more people become the slaves of addiction to narcotics, alcohol, and nicotine. These addictions destroy families and ruin lives. The brain’s chemistry is influenced by these drugs. This study aimed to evaluate how alcohol and other drugs affect the brain’s chemistry and identify potential avenues for therapy.

Modification Of Experimental Objective And Protocol To An Assessment Of The Effects Of Electroacupuncture On Vta Gaba Neurons In The Context Of Acute Alcohol, Christine H. Walton, Dr. Scott C. Steffensen

Journal of Undergraduate Research

Although my proposal for the ORCA grant involved the effects of nicotine on neurons in the VTA, preliminary data showed little to no promise and my mentor and I decided to go in a different direction.

Self-Regulatory Depletion Increases Emotional Reactivity In The Amygdala, Dylan D. Wagner, Todd F. Heatherton

Dartmouth Scholarship

The ability to self-regulate can become impaired when people are required to engage in successive acts of effortful self-control, even when self-control occurs in different domains. Here, we used functional neuroimaging to test whether engaging in effortful inhibition in the cognitive domain would lead to putative dysfunction in the emotional domain. Forty-eight participants viewed images of emotional scenes during functional magnetic resonance imaging in two sessions that were separated by a challenging attention control task that required effortful inhibition (depletion group) or not (control group). Compared to the control group, depleted participants showed increased activity in the left amygdala to …

Explorations Of Object And Location Memory Using Fmri, Andrew D. Passaro, L. Caitlin Elmore, Timothy M. Ellmore, Kenneth J. Leising, Andrew C. Papanicolaou, Anthony A. Wright

Publications and Research

Content-specific sub-systems of visual working memory (VWM) have been explored in many neuroimaging studies with inconsistent findings and procedures across experiments. The present study employed functional magnetic resonance imaging (fMRI) and a change detection task using a high number of trials and matched stimulus displays across object and location change (what vs. where) conditions. Furthermore, individual task periods were studied independently across conditions to identify differences corresponding to each task period. Importantly, this combination of task controls has not previously been described in the fMRI literature. Composite results revealed differential frontoparietal activation during each task period. A separation of object …

Effortless Awareness: Using Real Time Neurofeedback To Investigate Correlates Of Posterior Cingulate Cortex Activity In Meditators' Self-Report, Kathleen A. Garrison, Juan F. Santoyo, Jake H. Davis, Thomas A. Thomhill Iv, Catherine E. Kerr, Judson A. Brewer

Publications and Research

Neurophenomenological studies seek to utilize first-person self-report to elucidate cognitive processes related to physiological data. Grounded theory offers an approach to the qualitative analysis of self-report, whereby theoretical constructs are derived from empirical data. Here we used grounded theory methodology (GTM) to assess how the first-person experience of meditation relates to neural activity in a core region of the default mode network—the posterior cingulate cortex (PCC). We analyzed first-person data consisting of meditators' accounts of their subjective experience during runs of a real time fMRI neurofeedback study of meditation, and third-person data consisting of corresponding feedback graphs of PCC activity …

Enhanced Nicotine Self-Administration And Suppressed Dopaminergic Systems In A Rat Model Of Diabetes, Laura O'Dell

Selected Works Temporary Series

Patients with diabetes display a heightened propensity to use tobacco; however, it is unclear whether they experience enhanced rewarding effects of nicotine. Thus, this study examined the reinforcing effects of nicotine in a rodent model of diabetes involving administration of streptozotocin (STZ), a drug that is toxic to pancreatic insulin-producing cells. The first study compared STZ- and vehicle-treated rats that had 23-hour access to intravenous self-administration (IVSA) of nicotine or saline and concomitant access to food and water. In order to examine the contribution of dopamine to our behavioral effects, dopamine transporter (DAT), D1 and D2 receptor levels were compared …

Enhanced Nicotine Self-Administration And Suppressed Dopaminergic Systems In A Rat Model Of Diabetes, Laura O'Dell

Departmental Papers (Psych)

Patients with diabetes display a heightened propensity to use tobacco; however, it is unclear whether they experience enhanced rewarding effects of nicotine. Thus, this study examined the reinforcing effects of nicotine in a rodent model of diabetes involving administration of streptozotocin (STZ), a drug that is toxic to pancreatic insulin-producing cells. The first study compared STZ- and vehicle-treated rats that had 23-hour access to intravenous self-administration (IVSA) of nicotine or saline and concomitant access to food and water. In order to examine the contribution of dopamine to our behavioral effects, dopamine transporter (DAT), D1 and D2 receptor levels were compared …

Alternations Of Nmda And Gabab Receptor Function In Development: A Potential Animal Model Of Schizophrenia, Monica Bolton

UNLV Theses, Dissertations, Professional Papers, and Capstones

Schizophrenia is a debilitating mental disorder that affects up to 3% of the world population. The behavioral symptoms are categorized into positive and negative symptoms, which appear during late adolescence/early adulthood. Unfortunately, the underlying cellular and molecular mechanisms of the disease are poorly understood. Several hypotheses exist to explain mechanisms contributing to these behavioral alterations. One model proposes that a reduced function of the NMDA glutamate receptor on specific GABAergic interneurons may be responsible for deficits in schizophrenia. Post-mortem investigations provide evidence of reductions in both glutamate and GABA-related proteins in patients with schizophrenia. Further, GABAergic interneurons that are activated …

Network Dynamics Of Visual Naming, Christopher R. Conner

Dissertations and Theses (Open Access)

Recognition and naming of objects and actions are fundamental components of language. They involve several different systems working in coordination to accomplish a complex behavior. During visual naming, sensory and semantic processing are carried out by dedicated cortical substrates in the temporal and occipital lobes, while response selection and articulatory planning are handled by prefrontal cortex. Despite decades of research using lesion analysis, functional MRI and electro-encephalography, the precise dynamics involved remain unknown due to the inadequate spatio-temporal resolution of these methodologies. Of particular interest is the organization of semantic knowledge and the degree of serial and parallel organization of …

Prefrontal Cortical Microcircuits Bind Perception To Executive Control, Ioan Opris, Lucas Santos, Greg A. Gerhardt, Dong Song, Theodore W. Berger, Robert E. Hampson, Sam A. Deadwyler

Neuroscience Faculty Publications

During the perception-to-action cycle, our cerebral cortex mediates the interactions between the environment and the perceptual-executive systems of the brain. At the top of the executive hierarchy, prefrontal cortical microcircuits are assumed to bind perceptual and executive control information to guide goal-driven behavior. Here, we tested this hypothesis by comparing simultaneously recorded neuron firing in prefrontal cortical layers and the caudate-putamen of rhesus monkeys, trained in a spatial-versus-object, rule-based match-to-sample task. We found that during the perception and executive selection phases, cell firing in the localized prefrontal layers and caudate-putamen region exhibited similar location preferences on spatial-trials, but less on …

Smoothness Without Smoothing: Why Gaussian Naive Bayes Is Not Naive For Multi-Subject Searchlight Studies, Rajeev D.S Raizada, Yune-Sang Lee

Dartmouth Scholarship

Spatial smoothness is helpful when averaging fMRI signals across multiple subjects, as it allows different subjects' corresponding brain areas to be pooled together even if they are slightly misaligned. However, smoothing is usually not applied when performing multivoxel pattern-based analyses (MVPA), as it runs the risk of blurring away the information that fine-grained spatial patterns contain. It would therefore be desirable, if possible, to carry out pattern-based analyses which take unsmoothed data as their input but which produce smooth images as output. We show here that the Gaussian Naive Bayes (GNB) classifier does precisely this, when it is used in …

What Can The Organization Of The Brain’S Default Mode Network Tell Us About Self-Knowledge?, Joseph. M. Moran, William M. Kelley, Todd F. Heatherton

Dartmouth Scholarship

Understanding ourselves has been a fundamental topic for psychologists and philosophers alike. In this paper we review the evidence linking specific brain structures to self-reflection. The brain regions most associated with self-reflection are the posterior cingulate and medial prefrontal (mPFC) cortices, together known as the cortical midline structures (CMSs). We review evidence arguing that self-reflection is special in memory, while noting that these brain regions are often engaged when we think about others in our social worlds. Based on the CMSs’ patterns of connectivity and activity, we speculate about three possible interpretations of their role in supporting self-reflection that are …

Dna Homologous Recombination Factor Sfr1 Physically And Functionally Interacts With Estrogen Receptor Alpha, Benjamin Feng, David Singleton, Chun Guo, Amanda Gardner, Suresh Pakala, Rakesh Kumar, Elwood Jensen, Jinsong Zhang, Sohaib Khan

Peer Reviewed Articles

Estrogen receptor alpha (ERα), a ligand-dependent transcription factor, mediates the expression of its target genes by interacting with corepressors and coactivators. Since the first cloning of SRC1, more than 280 nuclear receptor cofactors have been identified, which orchestrate target gene transcription. Aberrant activity of ER or its accessory proteins results in a number of diseases including breast cancer. Here we identified SFR1, a protein involved in DNA homologous recombination, as a novel binding partner of ERα. Initially isolated in a yeast two-hybrid screen, the interaction of SFR1 and ERα was confirmed in vivo by immunoprecipitation and mammalian one-hybrid assays. SFR1 …

Decades-Long Social Memory In Bottlenose Dolphins, Jason N. Bruck

Faculty Publications

Long-term social memory is important, because it is an ecologically relevant test of cognitive capacity, it helps us understand which social relationships are remembered and it relates two seemingly disparate disciplines: cognition and sociality. For dolphins, long-term memory for conspecifics could help assess social threats as well as potential social or hunting alliances in a very fluid and complex fission-fusion social system, yet we have no idea how long dolphins can remember each other. Through a playback study conducted within a multi-institution dolphin breeding consortium (where animals are moved between different facilities), recognition of unfamiliar versus familiar signature whistles of …