Foundations of layer-specific fMRI and investigations of neurophysiological activity in the laminarized neocortex and olfactory bulb of animal models

Poplawsky, Alexander John,Fukuda, Mitsuhiro,Kim, Seong-Gi Elsevier 2019 NeuroImage Vol.199 No.-

<P><B>Abstract</B></P> <P>Laminar organization of neuronal circuits is a recurring feature of how the brain processes information. For instance, different layers compartmentalize different cell types, synaptic activities, and have unique intrinsic and extrinsic connections that serve as units for specialized signal processing. Functional MRI is an invaluable tool to investigate laminar processing in the <I>in vivo</I> human brain, but it measures neuronal activity indirectly by way of the hemodynamic response. Therefore, the accuracy of high-resolution laminar fMRI depends on how precisely it can measure localized microvascular changes nearest to the site of evoked activity. To determine the specificity of fMRI responses to the true neurophysiological responses across layers, the flexibility to invasive procedures in animal models has been necessary. In this review, we will examine different fMRI contrasts and their appropriate uses for layer-specific fMRI, and how localized laminar processing was examined in the neocortex and olfactory bulb. Through collective efforts, it was determined that microvessels, including capillaries, are regulated within single layers and that several endogenous and contrast-enhanced fMRI contrast mechanisms can separate these neural-specific vascular changes from the nonspecific, especially cerebral blood volume-weighted fMRI with intravenous contrast agent injection. We will also propose some open questions that are relevant for the successful implementation of layer-specific fMRI and its potential future directions to study laminar processing when combined with optogenetics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Reviewed layer-specific fMRI studies in animal models. </LI> <LI> Localization of BOLD and other fMRI contrasts to true site of neuronal activity. </LI> <LI> History of laminar studies in visual and somatosensory cortices and olfactory bulb. </LI> <LI> Future of laminar fMRI with targeted optogenetic stimulation. </LI> </UL> </P>

Layer-Specific fMRI Responses to Excitatory and Inhibitory Neuronal Activities in the Olfactory Bulb

Poplawsky, Alexander John,Fukuda, Mitsuhiro,Murphy, Matthew,Kim, Seong-Gi Society for Neuroscience 2015 The Journal of neuroscience Vol.35 No.46

<P>High-resolution functional magnetic resonance imaging (fMRI) detects localized neuronal activity via the hemodynamic response, but it is unclear whether it accurately identifies neuronal activity specific to individual layers. To address this issue, we preferentially evoked neuronal activity in superficial, middle, and deep layers of the rat olfactory bulb: the glomerular layer by odor (5% amyl acetate), the external plexiform layer by electrical stimulation of the lateral olfactory tract (LOT), and the granule cell layer by electrical stimulation of the anterior commissure (AC), respectively. Electrophysiology, laser-Doppler flowmetry of cerebral blood flow (CBF), and blood oxygenation level-dependent (BOLD) and cerebral blood volume-weighted (CBV) fMRI at 9.4 T were performed independently. We found that excitation of inhibitory granule cells by stimulating LOT and AC decreased the spontaneous multi-unit activities of excitatory mitral cells and subsequently increased CBF, CBV, and BOLD signals. Odor stimulation also increased the hemodynamic responses. Furthermore, the greatest CBV fMRI responses were discretely separated into the same layers as the evoked neuronal activities for all three stimuli, whereas BOLD was poorly localized with some exception to the poststimulus undershoot. In addition, the temporal dynamics of the fMRI responses varied depending on the stimulation pathway, even within the same layer. These results indicate that the vasculature is regulated within individual layers and CBV fMRI has a higher fidelity to the evoked neuronal activity compared with BOLD. Our findings are significant for understanding the neuronal origin and spatial specificity of hemodynamic responses, especially for the interpretation of laminar-resolution fMRI.</P><P><B>SIGNIFICANCE STATEMENT</B> Functional magnetic resonance imaging (fMRI) is a noninvasive, <I>in vivo</I> technique widely used to map function of the entire brain, including deep structures, in animals and humans. However, it measures neuronal activity indirectly by way of the vascular response. It is currently unclear how finely the hemodynamic response is regulated within single cortical layers and whether increased inhibitory neuronal activities affect fMRI signal changes. Both laminar specificity and the neural origins of fMRI are important to interpret functional maps properly, which we investigated by activating discrete rat olfactory bulb circuits.</P>

Improved spatial accuracy of functional maps in the rat olfactory bulb using supervised machine learning approach

Murphy, Matthew C.,Poplawsky, Alexander J.,Vazquez, Alberto L.,Chan, Kevin C.,Kim, Seong-Gi,Fukuda, Mitsuhiro Elsevier 2016 NeuroImage Vol.137 No.-

<P><B>Abstract</B></P> <P>Functional MRI (fMRI) is a popular and important tool for noninvasive mapping of neural activity. As fMRI measures the hemodynamic response, the resulting activation maps do not perfectly reflect the underlying neural activity. The purpose of this work was to design a data-driven model to improve the spatial accuracy of fMRI maps in the rat olfactory bulb. This system is an ideal choice for this investigation since the bulb circuit is well characterized, allowing for an accurate definition of activity patterns in order to train the model. We generated models for both cerebral blood volume weighted (CBVw) and blood oxygen level dependent (BOLD) fMRI data. The results indicate that the spatial accuracy of the activation maps is either significantly improved or at worst not significantly different when using the learned models compared to a conventional general linear model approach, particularly for BOLD images and activity patterns involving deep layers of the bulb. Furthermore, the activation maps computed by CBVw and BOLD data show increased agreement when using the learned models, lending more confidence to their accuracy. The models presented here could have an immediate impact on studies of the olfactory bulb, but perhaps more importantly, demonstrate the potential for similar flexible, data-driven models to improve the quality of activation maps calculated using fMRI data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We applied machine learning to compute activation maps in the rat olfactory bulb. </LI> <LI> Results from learned models were compared to results from general linear models. </LI> <LI> Spatial accuracy of activation maps was significantly improved with learned models. </LI> <LI> CBV and BOLD activation maps showed increased agreement using learned models. </LI> </UL> </P>

Optimum actuator placement for damping of vibrations using the Prestress–Accumulation Release control approach

Blazej Poplawski,Grzegorz Mikułowski,Dominik Pisarski,Rafał Wiszowaty,Łukasz Jankowski 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.24 No.1

This paper proposes a quantitative criterion for optimization of actuator placement for the Prestress–Accumulation Release (PAR) strategy of mitigation of vibrations. The PAR strategy is a recently developed semi-active control approach that relies on controlled redistribution of vibration energy into high-order modes, which are high-frequency and thus effectively dissipated by means of the natural mechanisms of material damping. The energy transfer is achieved by a controlled temporary removal of selected structural constraints. This paper considers a short-time decoupling of rotational degrees of freedom in a frame node so that the bending moments temporarily cease to be transferred between the involved beams. We propose and test a quantitative criterion for placement of such actuators. The criterion is based on local modal strain energy that can be released into high-order modes. The numerical time complexity is linear with respect to the number of actuators and potential placements, which facilitates quick analysis in case of large structures.

Technology Acceptance and Depressive Symptoms among Community-dwelling Older Adults

강석영,김정근,Antonina Poplawski 사단법인 한국융합기술연구학회 2022 아시아태평양융합연구교류논문지 Vol.8 No.12

Little is known about either older people’s perception and acceptance of new technology prior to actual technology usage or the impact technology acceptance has on their psychological well-being. This study aimed to explore the possible benefits of technology acceptance in reducing depression among older people residing in the community. This research project was a correlational study conducted in the northeastern United States. Data were collected from community-dwelling adults over 65 from October 2020 to March 2021. Out of 192 participants, 180 participants’ information was included for final analysis, with 12 cases excluded due to missing data, significant others completing surveys on the participant’s behalf as result of a disability or physical obstacle, or participants who we could not contact. The five-item Geriatric Depression Scale was employed to measure the level of depressive symptoms. Among the participants, 25 of them (13%) scored higher than 2, indicating the presence of depression. The correlates of the level of depression were: level of education, overall physical health, level of loneliness, perceived ease of technology use, attitude toward technology use, and intent to purchase new technology for older people. Findings indicate that a positive attitude toward technology use was inversely associated with depression levels. This shows how quality of life related to mental health will be improved by a change in attitude toward technology use. Participants were interested in learning to use new technology, and would like more opportunities to do so. Policy changes that increase lifelong learning options would help to make this happen.