The Experts below are selected from a list of 876 Experts worldwide ranked by ideXlab platform

Shigeyoshi Saito - One of the best experts on this subject based on the ideXlab platform.

  • quantitative t1 t2 and t2 mapping and semi quantitative neuromelanin sensitive magnetic resonance imaging of the human Midbrain
    PLOS ONE, 2016
    Co-Authors: Takashi Hashido, Shigeyoshi Saito
    Abstract:

    Purpose Neuromelanin is a dark pigment granule present within certain catecholamine neurons of the human brain. Here, we aimed to clarify the relationship between contrast of neuromelanin-sensitive magnetic resonance imaging (MRI) and MR relaxation times using T1, T2, and T2* mapping of the lower Midbrain. Methods The subjects were 14 healthy volunteers (11 men and 3 women, mean age 29.9 ± 6.9 years). Neuromelanin-sensitive MRI was acquired using an optimized T1-weighted two-dimensional (2D)-turbo spin-echo sequence. To quantitatively evaluate the relaxation time, 2D-image data for the T1, T2, and T2* maps were also acquired. The regions of interest (substantia nigra pars compacta [SNc], superior cerebellar peduncles [SCP], cerebral peduncles [CP], and Midbrain Tegmentum [MT]) were manually drawn on neuromelanin-sensitive MRI to measure the contrast ratio (CR) and on relaxation maps to measure the relaxation times. Results The CR in the SNc was significantly higher than the CRs in the SCP and CP. Compared to the SCP and CP, the SNc had significantly higher T1 relaxation times. Moreover, the SNc had significantly lower T2 and T2* relaxation times than the other three regions (SCP, CP, and MT). Correlation analyses showed no significant correlations between the CRs in the SNc, SCP, and CP and each relaxation time. Conclusions We demonstrated the relationship between the CR of neuromelanin-sensitive MRI and the relaxation times of quantitative maps of the human Midbrain.

Susan D Motts - One of the best experts on this subject based on the ideXlab platform.

  • cholinergic and non cholinergic projections from the pedunculopontine and laterodorsal tegmental nuclei to the medial geniculate body in guinea pigs
    Frontiers in Neuroanatomy, 2010
    Co-Authors: Brett R Schofield, Susan D Motts
    Abstract:

    The Midbrain Tegmentum is the source of cholinergic innervation of the thalamus and has been associated with arousal and control of the sleep/wake cycle. In general, the innervation arises bilaterally from the pedunculopontine tegmental nucleus (PPT) and the laterodorsal tegmental nucleus (LDT). While this pattern has been observed for many thalamic nuclei, a projection from the LDT to the medial geniculate body (MG) has been questioned in some species. We combined retrograde tracing with immunohistochemistry for choline acetyltransferase (ChAT) to identify cholinergic projections from the brainstem to the MG in guinea pigs. Double-labeled cells (retrograde and immunoreactive for ChAT) were found in both the PPT (74%) and the LDT (26%). In both nuclei, double-labeled cells were more numerous on the ipsilateral side. About half of the retrogradely labeled cells were immunonegative, suggesting they are non-cholinergic. The distribution of these immunonegative cells was similar to that of the immunopositive ones: more were in the PPT than the LDT and more were on the ipsilateral than the contralateral side. The results indicate that both the PPT and the LDT project to the MG, and suggest that both cholinergic and non-cholinergic cells contribute substantially to these projections.

  • projections from auditory cortex to cholinergic cells in the Midbrain Tegmentum of guinea pigs
    Brain Research Bulletin, 2009
    Co-Authors: Brett R Schofield, Susan D Motts
    Abstract:

    Anterograde and retrograde tracing techniques were used to characterize projections from the auditory cortex to the pedunculopontine and laterodorsal tegmental nuclei (PPT and LDT, respectively) in the Midbrain Tegmentum in guinea pigs. For anterograde tracing, tetramethylrhodamine dextran (FluoroRuby) was injected at several sites within auditory cortex. After sufficient time for transport, the brain was processed for immunohistochemistry with anti-choline acetyltransferase to reveal presumptive cholinergic cells. Anterogradely labeled axons were observed ipsilaterally and, in smaller numbers, contralaterally, in both the pedunculopontine and laterodorsal tegmental nuclei. In all four nuclei, tracer-labeled boutons appeared to contact immunolabeled (i.e., cholinergic) cells. The contacts occurred on cell bodies and dendrites. The results were similar following injections that spread across multiple auditory cortical areas or injections that were within primary auditory cortex. In order to confirm the anterograde results, in a second series of experiments, retrograde tracers were deposited in the pedunculopontine tegmental nucleus. These injections labeled layer V pyramidal cells in the auditory cortex. The results suggest an excitatory projection from primary auditory cortex bilaterally to cholinergic cells in the Midbrain Tegmentum. Such a pathway could allow auditory cortex to activate brainstem cholinergic circuits, possibly including the cholinergic pathways associated with arousal and gating of acoustic stimuli.

Eelco F M Wijdicks - One of the best experts on this subject based on the ideXlab platform.

  • the ascending reticular activating system
    Neurocritical Care, 2019
    Co-Authors: Eelco F M Wijdicks
    Abstract:

    Discovery of the ascending reticular activating system (ARAS) can be attributed to work done in research neuroscientist Horace Magoun’s laboratory. Before this finding, most scientists would focus on the diencephalon (and anterior Midbrain) but not more caudally. Stimulation of the medial bulbar reticular formation in the pontine and Midbrain Tegmentum resulted disappearance of synchronized discharge and low-voltage fast activity. The effects were mediated by a thalamic projection system. This finding was a dramatic departure from the early philosophers’ ascription of the awake soul to the ventricles (Galen), lumbosacral cord (Plato), pineal gland (Descartes), and even from more modern nineteenth- and twentieth-century hypotheses that the corpus striatum or periaqueductal gray matter housed the “seat of awareness.” Magoun and his collaborators closed in on its true location in the cephalic brainstem—clinicians and neuropathologists would soon follow.

Brett R Schofield - One of the best experts on this subject based on the ideXlab platform.

  • cholinergic and non cholinergic projections from the pedunculopontine and laterodorsal tegmental nuclei to the medial geniculate body in guinea pigs
    Frontiers in Neuroanatomy, 2010
    Co-Authors: Brett R Schofield, Susan D Motts
    Abstract:

    The Midbrain Tegmentum is the source of cholinergic innervation of the thalamus and has been associated with arousal and control of the sleep/wake cycle. In general, the innervation arises bilaterally from the pedunculopontine tegmental nucleus (PPT) and the laterodorsal tegmental nucleus (LDT). While this pattern has been observed for many thalamic nuclei, a projection from the LDT to the medial geniculate body (MG) has been questioned in some species. We combined retrograde tracing with immunohistochemistry for choline acetyltransferase (ChAT) to identify cholinergic projections from the brainstem to the MG in guinea pigs. Double-labeled cells (retrograde and immunoreactive for ChAT) were found in both the PPT (74%) and the LDT (26%). In both nuclei, double-labeled cells were more numerous on the ipsilateral side. About half of the retrogradely labeled cells were immunonegative, suggesting they are non-cholinergic. The distribution of these immunonegative cells was similar to that of the immunopositive ones: more were in the PPT than the LDT and more were on the ipsilateral than the contralateral side. The results indicate that both the PPT and the LDT project to the MG, and suggest that both cholinergic and non-cholinergic cells contribute substantially to these projections.

  • projections from auditory cortex to cholinergic cells in the Midbrain Tegmentum of guinea pigs
    Brain Research Bulletin, 2009
    Co-Authors: Brett R Schofield, Susan D Motts
    Abstract:

    Anterograde and retrograde tracing techniques were used to characterize projections from the auditory cortex to the pedunculopontine and laterodorsal tegmental nuclei (PPT and LDT, respectively) in the Midbrain Tegmentum in guinea pigs. For anterograde tracing, tetramethylrhodamine dextran (FluoroRuby) was injected at several sites within auditory cortex. After sufficient time for transport, the brain was processed for immunohistochemistry with anti-choline acetyltransferase to reveal presumptive cholinergic cells. Anterogradely labeled axons were observed ipsilaterally and, in smaller numbers, contralaterally, in both the pedunculopontine and laterodorsal tegmental nuclei. In all four nuclei, tracer-labeled boutons appeared to contact immunolabeled (i.e., cholinergic) cells. The contacts occurred on cell bodies and dendrites. The results were similar following injections that spread across multiple auditory cortical areas or injections that were within primary auditory cortex. In order to confirm the anterograde results, in a second series of experiments, retrograde tracers were deposited in the pedunculopontine tegmental nucleus. These injections labeled layer V pyramidal cells in the auditory cortex. The results suggest an excitatory projection from primary auditory cortex bilaterally to cholinergic cells in the Midbrain Tegmentum. Such a pathway could allow auditory cortex to activate brainstem cholinergic circuits, possibly including the cholinergic pathways associated with arousal and gating of acoustic stimuli.

Takashi Hashido - One of the best experts on this subject based on the ideXlab platform.

  • quantitative t1 t2 and t2 mapping and semi quantitative neuromelanin sensitive magnetic resonance imaging of the human Midbrain
    PLOS ONE, 2016
    Co-Authors: Takashi Hashido, Shigeyoshi Saito
    Abstract:

    Purpose Neuromelanin is a dark pigment granule present within certain catecholamine neurons of the human brain. Here, we aimed to clarify the relationship between contrast of neuromelanin-sensitive magnetic resonance imaging (MRI) and MR relaxation times using T1, T2, and T2* mapping of the lower Midbrain. Methods The subjects were 14 healthy volunteers (11 men and 3 women, mean age 29.9 ± 6.9 years). Neuromelanin-sensitive MRI was acquired using an optimized T1-weighted two-dimensional (2D)-turbo spin-echo sequence. To quantitatively evaluate the relaxation time, 2D-image data for the T1, T2, and T2* maps were also acquired. The regions of interest (substantia nigra pars compacta [SNc], superior cerebellar peduncles [SCP], cerebral peduncles [CP], and Midbrain Tegmentum [MT]) were manually drawn on neuromelanin-sensitive MRI to measure the contrast ratio (CR) and on relaxation maps to measure the relaxation times. Results The CR in the SNc was significantly higher than the CRs in the SCP and CP. Compared to the SCP and CP, the SNc had significantly higher T1 relaxation times. Moreover, the SNc had significantly lower T2 and T2* relaxation times than the other three regions (SCP, CP, and MT). Correlation analyses showed no significant correlations between the CRs in the SNc, SCP, and CP and each relaxation time. Conclusions We demonstrated the relationship between the CR of neuromelanin-sensitive MRI and the relaxation times of quantitative maps of the human Midbrain.