scholarly journals Two distinct profiles of fMRI and neurophysiological activity elicited by acetylcholine in visual cortex

2018 ◽  
Vol 115 (51) ◽  
pp. E12073-E12082 ◽  
Author(s):  
Daniel Zaldivar ◽  
Alexander Rauch ◽  
Nikos K. Logothetis ◽  
Jozien Goense
Keyword(s):  
Visual Cortex ◽  
Injection Site ◽  
Blood Oxygen Level Dependent ◽  
Local Injection ◽  
Electrode Arrays ◽  
Blood Oxygen Level ◽  
Neural Signals ◽  
Electrophysiological Recordings ◽  
High Gamma ◽  
Neurophysiological Activity

Cholinergic neuromodulation is involved in all aspects of sensory processing and is crucial for processes such as attention, learning and memory, etc. However, despite the known roles of acetylcholine (ACh), we still do not how to disentangle ACh contributions from sensory or task-evoked changes in functional magnetic resonance imaging (fMRI). Here, we investigated the effects of local injection of ACh on fMRI and neural signals in the primary visual cortex (V1) of anesthetized macaques by combining pharmaco-based MRI (phMRI) with electrophysiological recordings, using single electrodes and electrode arrays. We found that local injection of ACh elicited two distinct profiles of fMRI and neurophysiological activity, depending on the distance from the injector. Near the injection site, we observed an increase in the baseline blood oxygen-level-dependent (BOLD) and cerebral blood flow (CBF) responses, while their visual modulation decreased. In contrast, further from the injection site, we observed an increase in the visually induced BOLD and CBF modulation without changes in baseline. Neurophysiological recordings suggest that the spatial correspondence between fMRI responses and neural activity does not change in the gamma, high-gamma, and multiunit activity (MUA) bands. The results near the injection site suggest increased inhibitory drive and decreased metabolism, contrasting to the far region. These changes are thought to reflect the kinetics of ACh and its metabolism to choline.

Visual Cortex Alterations in Early and Late Blind Subjects During Tactile Perception

Perception ◽  
2021 ◽  
Vol 50 (3) ◽  
pp. 249-265
Author(s):  
A. Ankeeta ◽  
S. Senthil Kumaran ◽  
Rohit Saxena ◽  
Sada N. Dwivedi ◽  
Naranamangalam R. Jagannathan
Keyword(s):  
Visual Cortex ◽  
Children And Adolescents ◽  
Age Of Onset ◽  
Human Subjects ◽  
Functional Results ◽  
Blood Oxygen Level Dependent ◽  
Tactile Perception ◽  
Blood Oxygen Level ◽  
Sensory Motor ◽  
Post Hoc

Involvement of visual cortex varies during tactile perception tasks in early blind (EB) and late blind (LB) human subjects. This study explored differences in sensory motor networks associated with tactile task in EB and LB subjects and between children and adolescents. A total of 40 EB subjects, 40 LB subjects, and 30 sighted controls were recruited in two subgroups: children (6–12 years) and adolescents (13–19 years). Data were acquired using a 3T MR scanner. Analyses of blood oxygen level dependent (BOLD), functional connectivity (FC), correlation, and post hoc test for multiple comparisons were carried out. Difference in BOLD activity was observed in EB and LB groups in visual cortex during tactile perception, with increased FC of visual with dorsal attention and sensory motor networks in EB. EB adolescents exhibited increased connectivity with default mode and salience networks when compared with LB. Functional results correlated with duration of training, suggestive of better performance in EB. Alteration in sensory and visual networks in EB and LB correlated with duration of tactile training. Age of onset of blindness has an effect in cross-modal reorganization of visual cortex in EB and multimodal in LB in children and adolescents.

scholarly journals Neural correlates of the LSD experience revealed by multimodal neuroimaging

2016 ◽  
Vol 113 (17) ◽  
pp. 4853-4858 ◽  
Author(s):  
Robin L. Carhart-Harris ◽  
Suresh Muthukumaraswamy ◽  
Leor Roseman ◽  
Mendel Kaelen ◽  
Wouter Droog ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Processing ◽  
Brain Activity ◽  
Blood Oxygen Level Dependent ◽  
Retrosplenial Cortex ◽  
Alpha Power ◽  
Blood Oxygen Level ◽  
Psychedelic Drugs ◽  
Cortex Cérébral ◽  
Intrinsic Brain Activity

Lysergic acid diethylamide (LSD) is the prototypical psychedelic drug, but its effects on the human brain have never been studied before with modern neuroimaging. Here, three complementary neuroimaging techniques: arterial spin labeling (ASL), blood oxygen level-dependent (BOLD) measures, and magnetoencephalography (MEG), implemented during resting state conditions, revealed marked changes in brain activity after LSD that correlated strongly with its characteristic psychological effects. Increased visual cortex cerebral blood flow (CBF), decreased visual cortex alpha power, and a greatly expanded primary visual cortex (V1) functional connectivity profile correlated strongly with ratings of visual hallucinations, implying that intrinsic brain activity exerts greater influence on visual processing in the psychedelic state, thereby defining its hallucinatory quality. LSD’s marked effects on the visual cortex did not significantly correlate with the drug’s other characteristic effects on consciousness, however. Rather, decreased connectivity between the parahippocampus and retrosplenial cortex (RSC) correlated strongly with ratings of “ego-dissolution” and “altered meaning,” implying the importance of this particular circuit for the maintenance of “self” or “ego” and its processing of “meaning.” Strong relationships were also found between the different imaging metrics, enabling firmer inferences to be made about their functional significance. This uniquely comprehensive examination of the LSD state represents an important advance in scientific research with psychedelic drugs at a time of growing interest in their scientific and therapeutic value. The present results contribute important new insights into the characteristic hallucinatory and consciousness-altering properties of psychedelics that inform on how they can model certain pathological states and potentially treat others.

Retinotopic variations of the negative blood-oxygen-level dependent hemodynamic response function in human primary visual cortex

2021 ◽  
Vol 125 (4) ◽  
pp. 1045-1057 ◽  
Author(s):  
Natasha de la Rosa ◽  
David Ress ◽  
Amanda J. Taylor ◽  
Jung Hwan Kim
Keyword(s):  
Visual Cortex ◽  
Response Function ◽  
Complex Dynamics ◽  
Hemodynamic Response ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen ◽  
Oxygen Level ◽  
Hemodynamic Response Function ◽  
Blood Oxygen Level ◽  
Early Visual Cortex

We investigate dynamics of the negative hemodynamic response function (nHRF), the negative blood-oxygen-level-dependent (BOLD) response (NBR) evoked by a brief stimulus, in human early visual cortex. Here, we show that the nHRFs are not inverted versions of the corresponding pHRFs. The nHRF has complex dynamics that varied significantly with eccentricity. The results also show shift-invariant temporal linearity does not hold for the NBR.

scholarly journals Rewarding Feedback After Correct Visual Discriminations Has Both General and Specific Influences on Visual Cortex

2010 ◽  
Vol 104 (3) ◽  
pp. 1746-1757 ◽  
Author(s):  
R. S. Weil ◽  
N. Furl ◽  
C. C. Ruff ◽  
M. Symmonds ◽  
G. Flandin ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Stimuli ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen Level ◽  
Neural Basis ◽  
Correct Performance ◽  
Visual Events ◽  
Visual Areas ◽  
Improved Performance ◽  
Time Point

Reward can influence visual performance, but the neural basis of this effect remains poorly understood. Here we used functional magnetic resonance imaging to investigate how rewarding feedback affected activity in distinct areas of human visual cortex, separating rewarding feedback events after correct performance from preceding visual events. Participants discriminated oriented gratings in either hemifield, receiving auditory feedback at trial end that signaled financial reward after correct performance. Greater rewards improved performance for all but the most difficult trials. Rewarding feedback increased blood-oxygen-level-dependent (BOLD) signals in striatum and orbitofrontal cortex. It also increased BOLD signals in visual areas beyond retinotopic cortex, but not in primary visual cortex representing the judged stimuli. These modulations were seen at a time point in which no visual stimuli were presented or expected, demonstrating a novel type of activity change in visual cortex that cannot reflect modulation of response to incoming or anticipated visual stimuli. Rewarded trials led on the next trial to improved performance and enhanced visual activity contralateral to the judged stimulus, for retinotopic representations of the judged visual stimuli in V1. Our findings distinguish general effects in nonretinotopic visual cortex when receiving rewarding feedback after correct performance from consequences of reward for spatially specific responses in V1.

scholarly journals Distinct neurophysiological correlates of the fMRI BOLD signal in the hippocampus and neocortex

2021 ◽  
Author(s):  
Paul F. Hill ◽  
Sarah E. Seger ◽  
Hye Bin Yoo ◽  
Danielle R. King ◽  
Bradley C. Lega ◽  
...  
Keyword(s):  
Neural Activity ◽  
Blood Oxygen Level Dependent ◽  
Gamma Band ◽  
Bold Signal ◽  
Blood Oxygen Level ◽  
Indirect Measure ◽  
Neural Architecture ◽  
High Gamma ◽  
Gamma Band Activity ◽  
Band Activity

AbstractFunctional magnetic resonance imaging (fMRI) is among the foremost methods for mapping human brain function but provides only an indirect measure of underlying neural activity. Recent findings suggest that the neurophysiological correlates of the fMRI blood-oxygen-level-dependent (BOLD) signal might be regionally specific. We examined the neurophysiological correlates of the fMRI BOLD signal in the hippocampus and neocortex, where differences in neural architecture might result in a different relationship between the respective signals. Fifteen human neurosurgical patients (10 female, 5 male) implanted with depth electrodes performed a verbal free recall task while electrophysiological activity was recorded simultaneously from hippocampal and neocortical sites. The same patients subsequently performed a similar version of the task during a later fMRI session. Subsequent memory effects (SMEs) were computed for both imaging modalities as patterns of encoding-related brain activity predictive of later free recall. Linear mixed-effects modelling revealed that the relationship between BOLD and gamma-band SMEs was moderated by the lobar location of the recording site. BOLD and high gamma (70-150 Hz) SMEs positively covaried across much of the neocortex. This relationship was reversed in the hippocampus, where a negative correlation between BOLD and high gamma SMEs was evident. We also observed a negative relationship between BOLD and low gamma (30-70 Hz) SMEs in the medial temporal lobe more broadly. These results suggest that the neurophysiological correlates of the BOLD signal in the hippocampus differ from those observed in the neocortex.Significance StatementThe blood-oxygen-level-dependent (BOLD) signal forms the basis of fMRI but provides only an indirect measure of neural activity. Task-related modulation of BOLD signals are typically equated with changes in gamma-band activity; however, relevant empirical evidence comes largely from the neocortex. We examined neurophysiological correlates of the BOLD signal in the hippocampus, where the differing neural architecture might result in a different relationship between the respective signals. We identified a positive relationship between encoding-related changes in BOLD and gamma-band activity in frontal, temporal, and parietal cortex. This effect was reversed in the hippocampus, where BOLD and gamma-band effects negatively covaried. These results suggest regional variability in the transfer function between neural activity and the BOLD signal in the hippocampus and neocortex.

Radial Biases in the Processing of Motion and Motion-Defined Contours by Human Visual Cortex

2009 ◽  
Vol 102 (5) ◽  
pp. 2974-2981 ◽  
Author(s):  
Colin W. G. Clifford ◽  
Damien J. Mannion ◽  
J. Scott McDonald
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Human Subjects ◽  
Temporal Integration ◽  
Blood Oxygen Level Dependent ◽  
Orientation Tuning ◽  
Bold Signal ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Blood Oxygen Level

Luminance gratings reportedly produce a stronger functional magnetic resonance imaging (fMRI) blood oxygen level–dependent (BOLD) signal in those parts of the retinotopic cortical maps where they are oriented radially to the point of fixation. We sought to extend this finding by examining anisotropies in the response of cortical areas V1–V3 to motion-defined contour stimuli. fMRI at 3 Tesla was used to measure the BOLD signal in the visual cortex of six human subjects. Stimuli were composed of strips of spatial white noise texture presented in an annular window. The texture in alternate strips moved in opposite directions (left–right or up–down). The strips themselves were static and tilted 45° left or right from vertical. Comparison with maps of the visual field obtained from phase-encoded retinotopic analysis revealed systematic patterns of radial bias. For motion, a stronger response to horizontal was evident within V1 and along the borders between V2 and V3. For orientation, the response to leftward tilted contours was greater in left dorsal and right ventral V1–V3. Radial bias for the orientation of motion-defined contours analogous to that reported previously for luminance gratings could reflect cue-invariant processing or the operation of distinct mechanisms subject to similar anisotropies in orientation tuning. Radial bias for motion might be related to the phenomenon of “motion streaks,” whereby temporal integration by the visual system introduces oriented blur along the axis of motion. We speculate that the observed forms of radial bias reflect a common underlying anisotropy in the representation of spatiotemporal image structure across the visual field.

Dopaminergic neuromodulation has no detectable effect on visual-cue induced haemodynamic response function in the visual cortex: A double-blind, placebo-controlled functional magnetic resonance imaging study

2020 ◽  
Vol 35 (1) ◽  
pp. 100-102
Author(s):  
Andrei Manoliu ◽  
Ronald Sladky ◽  
Sigrid Scherpiet ◽  
Lutz Jäncke ◽  
Matthias Kirschner ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Visual Cortex ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Blood Oxygen Level Dependent ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Blood Oxygen Level ◽  
Double Blind ◽  
Visual Cue

The aim of this study was to investigate the effect of acute dopamine agonistic and antagonistic manipulation on the visual-cue induced blood oxygen level-dependent signal response in healthy volunteers. Seventeen healthy volunteers in a double-blind placebo-controlled cross-over design received either a dopamine antagonist, agonist or placebo and underwent functional magnetic resonance imaging. Using classical inference and Bayesian statistics, we found no effect of dopaminergic modulation on properties of visual-cue induced blood oxygen level-dependent signals in the visual cortex, particularly on distinct properties of the haemodynamic response function (amplitude, time-to-peak and width). Dopamine-related effects modulating the neurovascular coupling in the visual cortex might be negligible when measured via functional magnetic resonance imaging.

scholarly journals Non-linear frequency-dependence of neurovascular coupling in the cerebellar cortex implies vasodilation-vasoconstriction competition

2021 ◽  
Author(s):  
Giuseppe Gagliano ◽  
Anita Monteverdi ◽  
Stefano Casali ◽  
Umberto Laforenza ◽  
Claudia A.M. Gandini Wheeler-Kingshott ◽  
...  
Keyword(s):  
Frequency Dependence ◽  
Time Course ◽  
Mossy Fiber ◽  
Neurovascular Coupling ◽  
Blood Oxygen Level Dependent ◽  
Electrode Arrays ◽  
Blood Oxygen Level ◽  
Linear Frequency ◽  
Non Linear ◽  
Capillary Dynamics

Neurovascular coupling (NVC) is the process associating local cerebral blood flow (CBF) to neuronal activity (NA). Although NVC provides the basis for the blood-oxygen-level-dependent (BOLD) effect used in functional MRI (fMRI), the relationship between NVC and NA is still unclear. Since recent studies reported cerebellar non-linearities in BOLD signals during motor tasks execution, we investigated the NVC/NA relationship using a range of input frequencies in acute mouse cerebellar slices of vermis and hemisphere. The capillary diameter increased in response to mossy fiber activation in the 6-300Hz range, with a marked inflection around 50Hz (vermis) and 100Hz (hemisphere). The corresponding NA was recorded using high-density multi-electrode arrays and correlated to capillary dynamics through a computational model dissecting the main components of granular layer activity. Here, NVC is known to involve a balance between the NMDAR-NO pathway driving vasodilation and the mGluRs-20HETE pathway driving vasoconstriction. Simulations showed that the NMDAR-mediated component of NA was sufficient to explain the time-course of the capillary dilation but not its non-linear frequency-dependence, suggesting that the mGluRs-20HETE pathway plays a role at intermediate frequencies. These parallel control pathways imply a vasodilation-vasoconstriction competition hypothesis that could adapt local hemodynamics at the microscale bearing implications for fMRI signals interpretation.

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