Isabel N Christie^1,2, Jack A Wells², Nephtali Marina¹, Sergey Kasparov³, Alexander V Gourine¹, and Mark F Lythgoe^2
1Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom, ²UCL Centre for Advanced Biomedical Imaging, Division of Medicine and Institute of Child Health, University College London, London, United Kingdom, ³School of Physiology and Pharmacology, University of Bristol (IC and JW joint first authors, SK,AG,ML joint senior authors)

This study documents marked non-specific effects of light delivered to the cortex with fMRI. With regard to opMRI such artefacts could confound genuine optogenetically induced hemodynamic changes. Functional MRI responses can be observed using established light delivery protocols, which has profound implications for the design and interpretation of combined optogenetic and MRI experiments.

Milan Scheidegger¹, Simone Grimm², Martin Walter³, Heinz Boeker², Peter Boesiger¹, Erich Seifritz², and Anke Henning^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, ²Clinic of Affective Disorders and General Psychiatry, University Hospital of Psychiatry Zurich, Zurich, Switzerland, ³Department of Psychiatry, Otto-von-Guericke University, Magdeburg, Germany

Many neuroimaging findings are compatible with the hypothesis that limbic hyperactivity during evaluation of emotional stimuli, combined with prefrontal hypoactivity, might cause negative emotional biases in patients suffering from major depressive disorder (MDD) and that this imbalance can be reversed by antidepressant drug treatment. Our findings show that in healthy subjects an antidepressant intravenous dose of ketamine reduces limbic reactivity in the amygdalo-hippocampal complex during an emotional processing task, which is in support of the hypothesis that pharmacologically modulating limbic neurocircuits might be an important therapeutic strategy to restore parts of the disrupted neurobehavioural homeostasis in MDD.

Xi Chen*¹, Hong Gu*¹, and Yihong Yang^1
1Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, United States

We have found negative correlation between the GABA concentration and correlation strength of BOLD signals at rest in primary visual cortex in this study and both of these resting neurotransmitter and hemodynamic indices predict the amplitude of evoked BOLD responses to visual stimuli. A mediation analysis shows that functional connectivity strength acts as a mediator in the relationship of the GABA concentration vesus task activation prediction.

Yen-Yu Ian Shih¹, Yash Vardhan Tiwari¹, William E Rogers¹, and Timothy Q Duong^1
1Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States

This study demonstrates thalamocortical connectivity by direct stimulating the ventral posterior medial thalamus in rats. Our results indicate that the barrel cortex is reliably activated and the BOLD responses exhibit frequency and amplitude-dependent properties. Cortical spreading depolarization occasionally occurred, initiating in the barrel cortex and propagating toward the midline, anterior, and posterior part of the cortex within the same hemisphere. DBS-fMRI has potential to explore/validate functional connectivity in the brain and monitor functional plasticity changes in a specific neuroanatomical pathway in vivo.

Matthew M. Cheung^1,2, Condon Lau^1,2, Joe S. Cheng^1,2, Iris Y. Zhou^1,2, Kevin C. Chan^1,3, Jevin W. Zhang^1,2, and Ed X. Wu^1,2
1Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China, ³Center for the Neural Basis of Cognition, University of Pittsburgh and Carnegie Mellon University, Pittsburgh, PA, United States

In this study, tonotopic changes in normal animals with increased sound pressure level (SPL) and in animals injured by post-natal noise exposure (NE) were investigated using a novel fMRI paradigm that integrates distortion-free MRI and continuous frequency sweeping. Our results demonstrated the capability of this proposed novel auditory fMRI paradigm to study subtle shift and alteration in the tonotopy. This technique can potentially characterize the auditory neuronal response and facilitate investigation of auditory information processing in cortical and subcortical structures.

Xin Yu¹, Stephen Dodd¹, and Alan Koretsky^1
1NINDS, NIH, Bethesda, MD, United States

Despite extensive studies of intracortical plasticity due to sensory deprivation or overuse, the effect of callosal inputs from the opposite hemisphere on cortical reorganization is seldom studied. Here, we studied the effect of transcallosal functional changes from the normal barrel cortex (BC) to the deprived BC on the takeover of the deprived BC by adjacent forepaw somatosensory cortex (FP-S1). Functional MRI at 300um isotropic resolution detected FP-S1expansion toward the deprived BC only if the callosal inputs from the normal BC were removed by ablation of this cortex. This result indicates a specific role played by transcallosal plasticity for functional recovery.

Basavaraju G Sanganahalli¹, Peter Herman¹, Douglas L Rothman^1,2, Hal Blumenfeld³, and Fahmeed Hyder^1,2
1Diagnostic Radiology, Yale University, New haven, CT, United States, ²Biomedical Engineering, Yale University, ³Neurology, Yale University, New Haven

Peripheral electrical stimulation (2mA, 0.3ms, variable frequencies 1-48Hz) of the rat forepaw evoked a positive BOLD signal change in the contralateral cortical (S1_FL) and ventral posterior nucleus (VPL) of thalamus under different anesthetics (Isoflurane, Domitor and α-chloralose). The BOLD responses were correlated with neural activities. However both fMRI and neuronal responses exhibited a different frequency tuning curve for each anesthetic in the (S1_FL), while the same linear frequency response in VPL was elicited in all anesthetic conditions. These results suggest that subcortical structure is less influenced by anesthesia, while in the cortex the deeper anesthesia augments the process of adaptation.

Han Yuan¹, Vadim Zotev¹, Raquel Phillips¹, Wayne Drevets¹, and Jerzy Bodurka^1
1Laureate Institute for Brain Research, Tulsa, OK, United States

We developed a novel, fully data-driven approach to the analysis of EEG microstates, and applied this approach to investigate EEG microstates as electrophysiological correlates for BOLD resting state networks (RSNs) using simultaneous EEG and fMRI recordings. Thirteen main microstates were identified at the group level and the time courses of these microstates were compared to the whole-brain BOLD signal. Our results have revealed for the first time EEG microstate-associated networks that correspond to a wide range of RSNs, including visual, sensorimotor, auditory, attention, frontal, ventral stream and default mode networks.

Robert Trampel¹, Pierre-Louis Bazin¹, Andreas Schäfer¹, Robin Martin Heidemann¹, Dimo Ivanov¹, Gabriele Lohmann¹, Stefan Geyer¹, and Robert Turner^1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

The time course of the BOLD response to a specific task differs across brain areas, giving rise to localized activations. Recent progress in ultra-high resolution fMRI makes it possible additionally to compare the BOLD signal at different cortical depths, giving a more detailed picture of the functional fingerprint of any particular cortical area. We performed fMRI at 7 Tesla with sub-millimeter resolution during imagined and actual finger tapping. The relative BOLD signal time course was observed to vary not only across sensorimotor cortical areas but also between cortical depths within each area.