Hybrid head cap for mouse brain studies

Abstract. In this thesis, I present a hybrid head cap in combination with non-invasive multi-channel Electroencephalogram (EEG) and Near-Infrared Spectroscopy (NIRS) to measure brainwaves on mice’s scalps. Laboratory animal research provides insights into multiple potential applications involving humans and other animals. An experimental framework that targets laboratory animals can lead to useful transnational research if it strongly reflects the actual application environment. The non-invasive head cap with three electrodes for EEG and two optodes for NIRS is suggested to measure brainwaves throughout the laboratory mice’s entire brain region without surgical procedures. The suggested hybrid head cap aims to ensure stability in vivo monitoring for mouse brain in a non-invasive way, similarly as the monitoring is performed for the human brain. The experimental part of the work to study the quality of the gathered EEG and fNIRS signals, and usability validation of the head cap, however, was not completed in the planned time frame of the thesis work

Evaluating feasibility of functional near-infrared spectroscopy in dolphins

SIGNIFICANCE: Using functional near-infrared spectroscopy (fNIRS) in bottlenose dolphins (Tursiops truncatus) could help to understand how echolocating animals perceive their environment and how they focus on specific auditory objects, such as fish, in noisy marine settings. AIM: To test the feasibility of near-infrared spectroscopy (NIRS) in medium-sized marine mammals, such as dolphins, we modeled the light propagation with computational tools to determine the wavelengths, optode locations, and separation distances that maximize sensitivity to brain tissue. APPROACH: Using frequency-domain NIRS, we measured the absorption and reduced scattering coefficient of dolphin sculp. We assigned muscle, bone, and brain optical properties from the literature and modeled light propagation in a spatially accurate and biologically relevant model of a dolphin head, using finite-element modeling. We assessed tissue sensitivities for a range of wavelengths (600 to 1700 nm), source-detector distances (50 to 120 mm), and animal sizes (juvenile model 25% smaller than adult). RESULTS: We found that the wavelengths most suitable for imaging the brain fell into two ranges: 700 to 900 nm and 1100 to 1150 nm. The optimal location for brain sensing positioned the center point between source and detector 30 to 50 mm caudal of the blowhole and at an angle 45 deg to 90 deg lateral off the midsagittal plane. Brain tissue sensitivity comparable to human measurements appears achievable only for smaller animals, such as juvenile bottlenose dolphins or smaller species of cetaceans, such as porpoises, or with source-detector separations ≫100  mm in adult dolphins. CONCLUSIONS: Brain measurements in juvenile or subadult dolphins, or smaller dolphin species, may be possible using specialized fNIRS devices that support optode separations of >100  mm. We speculate that many measurement repetitions will be required to overcome hemodynamic signals originating predominantly from the muscle layer above the skull. NIRS measurements of muscle tissue are feasible today with source-detector separations of 50 mm, or even less.Publisher PDFPeer reviewe

Optical imaging and spectroscopy for the study of the human brain: status report

This report is the second part of a comprehensive two-part series aimed at reviewing an extensive and diverse toolkit of novel methods to explore brain health and function. While the first report focused on neurophotonic tools mostly applicable to animal studies, here, we highlight optical spectroscopy and imaging methods relevant to noninvasive human brain studies. We outline current state-of-the-art technologies and software advances, explore the most recent impact of these technologies on neuroscience and clinical applications, identify the areas where innovation is needed, and provide an outlook for the future directions

Optical imaging and spectroscopy for the study of the human brain: status report.

This report is the second part of a comprehensive two-part series aimed at reviewing an extensive and diverse toolkit of novel methods to explore brain health and function. While the first report focused on neurophotonic tools mostly applicable to animal studies, here, we highlight optical spectroscopy and imaging methods relevant to noninvasive human brain studies. We outline current state-of-the-art technologies and software advances, explore the most recent impact of these technologies on neuroscience and clinical applications, identify the areas where innovation is needed, and provide an outlook for the future directions

The Cognitive Neuroscience Toolkit for the Neuroeconomist: A Functional Overview

This article provides the beginning neuroeconomist with an introductory overview to the different methods used in human neuroscience. It describes basic strengths and weaknesses of each technique, points to examples of how each technique has been used in neuroeconomic studies, and provides key tutorial references that contain more detailed information. In addition to this overview, the article presents a framework that organizes human neuroscience methods functionally, according to whether they provide tests of the association between brain activity and cognition or behavior, or whether they test the necessity or the sufficiency of brain activity for cognition and behavior. This framework demonstrates the utility of a multimethod research approach, because converging evidence from tests of association, necessity, and sufficiency provides the strongest inference regarding brain–behavior relationships. Set against this goal of converging evidence, human neuroscience studies in neuroeconomics currently rely far too heavily on methods that test association, most notably functional magnetic resonance imaging (MRI)

Optical imaging and spectroscopy for the study of the human brain: status report

This report is the second part of a comprehensive two-part series aimed at reviewing an extensive and diverse toolkit of novel methods to explore brain health and function. While the first report focused on neurophotonic tools mostly applicable to animal studies, here, we highlight optical spectroscopy and imaging methods relevant to noninvasive human brain studies. We outline current state-of-the-art technologies and software advances, explore the most recent impact of these technologies on neuroscience and clinical applications, identify the areas where innovation is needed, and provide an outlook for the future directions. Keywords: DCS; NIRS; diffuse optics; functional neuroscience; optical imaging; optical spectroscop

Stimulating vision: measuring and modelling transcranial direct current stimulation of the visual cortex

Transcranial direct current stimulation (tDCS) has enjoyed something of a renaissance in neuroscientific research, however, this has not been accompanied by a commensurate increase in our understanding of its neurobiological mechanisms. At present, there remains a large explanatory gap between the stimulation effects on cells in in vivo or in vitro studies and the wide variety of behavioural findings in human studies. Consequently, tDCS research is currently confronted with a wide variety of conceptual and methodological challenges that have hampered the development of mature rationales for its use in healthy and clinical populations. This thesis aimed to address some of these challenges by combining data from behavioural and neuroimaging experiments with findings from individualised models of tDCS-induced electric fields. Experiments focused on the visual system, using relatively simple paradigms based on pattern-reversing checkerboards and the detection of achromatic dot stimuli to investigate stimulation effects on visual processing, The role of inter-individual variability – both in baseline sensory performance and in head anatomy – received particular attention in the design of studies. In the second chapter of the thesis, the question of suitable current waveforms for doubleblind, sham-controlled tDCS studies is discussed. The third chapter investigates the role of electrode montage in eliciting tDCS effects on contrast detection at central and peripheral visual field locations. In Chapters 4 and 5, inter-individual differences in anatomy are quantified using computational modelling of electric fields and neuroimaging methods. Work presented in Chapter 6 explores the feasibility of acquiring concurrent tDCS-NIRS-MEG data. Together, results from these studies suggest that the large parameter space for designing and interpreting human tDCS experiments calls for a broad range of methodological advances in future tDCS research

Assessment of sensation seeking personality type using behavioral and functional neuroimaging measures

2020 Fall.Includes bibliographical references.Sensation seeking personality type, in which an individual has the propensity to engage in risky behaviors while searching for an optimal level of stimulation, is associated with a variety of negative health outcomes, such as higher rates of substance misuse, gambling, and self-harm. It is important to develop methods to identify those at higher risk of engaging in such health risk behaviors. Historically, sensation seeking has been primarily measured using self-report surveys. Providing additional measures of sensation seeking, such as through behavioral assessment or biomarkers, would aid our measurement of the sensation seeking personality type. The present work sought to create a new behavioral measure of sensation seeking personality type, the Sensation Seeking Dot Probe Task (SSDP), that measures an individual's attentional bias towards sensation seeking imagery. Further, the SSDP task was combined with functional Near Infrared Spectroscopy, which utilizes the spectral differences of hemoglobin in the brain to measure neural activity, to identify neural correlates of attention to sensation seeking imagery and relate them to the Sensation Seeking Personality Type scale. I hypothesized that the SSDP would be as effective in identifying sensation seeking as the self-report scale, and that attention to sensation seeking images would correlate with changes in neural activity in the prefrontal cortex and orbitofrontal cortex (regions associated with executive control and decision making) that would be greater in high sensation seeking individuals. While the SSDP did not find significant differences in accuracy or reaction time, the typical measures used in attentional bias dot-probe tasks, there was a significant difference in selection of sensation seeking imagery when paired with neutral control imagery. There were also significantly different changes in activity during sensation seeking congruent tasks in areas of the lateral prefrontal cortex for high sensation seeking individuals. These results suggest functional and behavioral differences measurable in high sensation seekers, and future tasks can use these findings to lead to a greater understanding of the personality type