scholarly journals Persistent activity in a cortical-to-subcortical circuit: bridging the temporal gap in trace eyelid conditioning

2012 ◽  
Vol 107 (1) ◽  
pp. 50-64 ◽  
Author(s):  
Jennifer J. Siegel ◽  
Brian Kalmbach ◽  
Raymond A. Chitwood ◽  
Michael D. Mauk
Keyword(s):  
Eyelid Conditioning ◽  
Mossy Fiber ◽  
Trace Conditioning ◽  
Brain Structures ◽  
Learning Activity ◽  
Persistent Activity ◽  
Trace Interval ◽  
Cerebellar Learning ◽  
Response Expression

We have addressed the source and nature of the persistent neural activity that bridges the stimulus-free gap between the conditioned stimulus (CS) and unconditioned stimulus (US) during trace eyelid conditioning. Previous work has demonstrated that this persistent activity is necessary for trace eyelid conditioning: CS-elicited activity in mossy fiber inputs to the cerebellum does not extend into the stimulus-free trace interval, which precludes the cerebellar learning that mediates conditioned response expression. In behaving rabbits we used in vivo recordings from a region of medial prefrontal cortex (mPFC) that is necessary for trace eyelid conditioning to test the hypothesis that neurons there generate activity that persists beyond CS offset. These recordings revealed two patterns of activity during the trace interval that would enable cerebellar learning. Activity in some cells began during the tone CS and persisted to overlap with the US, whereas in other cells, activity began during the stimulus-free trace interval. Injection of anterograde tracers into this same region of mPFC revealed dense labeling in the pontine nuclei, where recordings also revealed tone-evoked persistent activity during trace conditioning. These data suggest a corticopontine pathway that provides an input to the cerebellum during trace conditioning trials that bridges the temporal gap between the CS and US to engage cerebellar learning. As such, trace eyelid conditioning represents a well-characterized and experimentally tractable system that can facilitate mechanistic analyses of cortical persistent activity and how it is used by downstream brain structures to influence behavior.

scholarly journals Temporal Patterns of Inputs to Cerebellum Necessary and Sufficient for Trace Eyelid Conditioning

2010 ◽  
Vol 104 (2) ◽  
pp. 627-640 ◽  
Author(s):  
Brian E. Kalmbach ◽  
Tatsuya Ohyama ◽  
Michael D. Mauk
Keyword(s):  
Eyelid Conditioning ◽  
Granule Cells ◽  
Mossy Fiber ◽  
Mossy Fibers ◽  
Trace Conditioning ◽  
Trace Interval ◽  
The Us ◽  
Conditioned Responses ◽  
Necessary And Sufficient ◽  
Stimulation Of

Trace eyelid conditioning is a form of associative learning that requires several forebrain structures and cerebellum. Previous work suggests that at least two conditioned stimulus (CS)-driven signals are available to the cerebellum via mossy fiber inputs during trace conditioning: one driven by and terminating with the tone and a second driven by medial prefrontal cortex (mPFC) that persists through the stimulus-free trace interval to overlap in time with the unconditioned stimulus (US). We used electric stimulation of mossy fibers to determine whether this pattern of dual inputs is necessary and sufficient for cerebellar learning to express normal trace eyelid responses. We find that presenting the cerebellum with one input that mimics persistent activity observed in mPFC and the lateral pontine nuclei during trace eyelid conditioning and another that mimics tone-elicited mossy fiber activity is sufficient to produce responses whose properties quantitatively match trace eyelid responses using a tone. Probe trials with each input delivered separately provide evidence that the cerebellum learns to respond to the mPFC-like input (that overlaps with the US) and learns to suppress responding to the tone-like input (that does not). This contributes to precisely timed responses and the well-documented influence of tone offset on the timing of trace responses. Computer simulations suggest that the underlying cerebellar mechanisms involve activation of different subsets of granule cells during the tone and during the stimulus-free trace interval. These results indicate that tone-driven and mPFC-like inputs are necessary and sufficient for the cerebellum to learn well-timed trace conditioned responses.

The Reaction of Brain Structures with OsO4-Zinc-Iodide Stain

1971 ◽  
Vol 29 ◽  
pp. 272-273
Author(s):  
Werner J. Niklowitz
Keyword(s):  
Electron Microscope ◽  
Structural Changes ◽  
Mossy Fiber ◽  
Toxic Metal ◽  
Staining Technique ◽  
Brain Structures ◽  
Oxidase Inhibitor ◽  
Fiber Layer ◽  
Hippocampal Tissue ◽  
Zinc Iodide

After intoxication of rabbits with certain substances such as convulsant agents (3-acetylpyridine), centrally acting drugs (reserpine), or toxic metal compounds (tetraethyl lead) a significant observation by phase microscope is the loss of contrast of the hippocampal mossy fiber layer. It has been suggested that this alteration, as well as changes seen with the electron microscope in the hippocampal mossy fiber boutons, may be related to a loss of neurotransmitters. The purpose of these experiments was to apply the OsO4-zinc-iodide staining technique to the study of these structural changes since it has been suggested that OsO4-zinc-iodide stain reacts with neurotransmitters (acetylcholine, catecholamines).Domestic New Zealand rabbits (2.5 to 3 kg) were used. Hippocampal tissue was removed from normal and experimental animals treated with 3-acetylpyridine (antimetabolite of nicotinamide), reserpine (anti- hypertensive/tranquilizer), or iproniazid (antidepressant/monamine oxidase inhibitor). After fixation in glutaraldehyde hippocampal tissue was treated with OsO4-zinc-iodide stain and further processed for phase and electron microscope studies.

scholarly journals Whole-brain 3D MR fingerprinting brain imaging: clinical validation and feasibility to patients with meningioma

2021 ◽  
Author(s):  
Thomaz R. Mostardeiro ◽  
Ananya Panda ◽  
Robert J. Witte ◽  
Norbert G. Campeau ◽  
Kiaran P. McGee ◽  
...  
Keyword(s):  
White Matter ◽  
Statistical Significance ◽  
Relaxation Times ◽  
Brain Structures ◽  
Centrum Semiovale ◽  
In Vivo Evaluation ◽  
Whole Brain ◽  
Mean Values ◽  
Caudate Head

Abstract Purpose MR fingerprinting (MRF) is a MR technique that allows assessment of tissue relaxation times. The purpose of this study is to evaluate the clinical application of this technique in patients with meningioma. Materials and methods A whole-brain 3D isotropic 1mm3 acquisition under a 3.0T field strength was used to obtain MRF T1 and T2-based relaxometry values in 4:38 s. The accuracy of values was quantified by scanning a quantitative MR relaxometry phantom. In vivo evaluation was performed by applying the sequence to 20 subjects with 25 meningiomas. Regions of interest included the meningioma, caudate head, centrum semiovale, contralateral white matter and thalamus. For both phantom and subjects, mean values of both T1 and T2 estimates were obtained. Statistical significance of differences in mean values between the meningioma and other brain structures was tested using a Friedman’s ANOVA test. Results MR fingerprinting phantom data demonstrated a linear relationship between measured and reference relaxometry estimates for both T1 (r2 = 0.99) and T2 (r2 = 0.97). MRF T1 relaxation times were longer in meningioma (mean ± SD 1429 ± 202 ms) compared to thalamus (mean ± SD 1054 ± 58 ms; p = 0.004), centrum semiovale (mean ± SD 825 ± 42 ms; p < 0.001) and contralateral white matter (mean ± SD 799 ± 40 ms; p < 0.001). MRF T2 relaxation times were longer for meningioma (mean ± SD 69 ± 27 ms) as compared to thalamus (mean ± SD 27 ± 3 ms; p < 0.001), caudate head (mean ± SD 39 ± 5 ms; p < 0.001) and contralateral white matter (mean ± SD 35 ± 4 ms; p < 0.001) Conclusions Phantom measurements indicate that the proposed 3D-MRF sequence relaxometry estimations are valid and reproducible. For in vivo, entire brain coverage was obtained in clinically feasible time and allows quantitative assessment of meningioma in clinical practice.

scholarly journals The role of cochlear implant positioning on MR imaging quality: a preclinical in vivo study with a novel implant magnet system

2021 ◽  
Author(s):  
Pietro Canzi ◽  
Marianna Magnetto ◽  
Anna Simoncelli ◽  
Marco Manfrin ◽  
Federico Aprile ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Cochlear Implant ◽  
Occipital Lobe ◽  
Brain Structures ◽  
Magnet System ◽  
High Positive Correlation ◽  
Imaging Quality ◽  
Signal Void ◽  
Mri Surveillance

Abstract Purposes To investigate the effects for Ultra 3D cochlear implant (CI) positioning on MR imaging quality, looking at a comprehensive description of intracranial structures in cases of unilateral and bilateral CI placement. Methods Four CI angular positions (90°, 120°, 135° and 160°) at 9 cm distance from the outer-ear canal were explored. The 1.5 T MRI assessment included our institutional protocol for the investigation of brain pathologies without gadolinium application. Three investigators (two experienced neuroradiologists and one experienced otoneurosurgeon) independently evaluated the MR findings. A 4-point scale was adopted to describe 14 intracranial structures and to determine which CI positioning allowed the best image quality score and how bilateral CI placement modified MRI scan visibility. Results A high positive correlation was found between the three blinded observers. Structures situated contralateral from the CI showed high-quality values in all four placements. Structures situated ipsilaterally provided results suitable for diagnostic purposes for at least one position. At 90°, artifacts mainly involved brain structures located cranially and anteriorly (e.g., temporal lobe); on the contrary, at 160°, artifacts mostly influenced the posterior fossa structures (e.g., occipital lobe). For the bilateral CI condition, MR imaging examination revealed additional artifacts involving all structures located close to either CI, where there was a signal void/distortion area. Conclusions Suitable unilateral CI positioning can allow the visualization of intracranial structures with sufficient visibility for diagnostic purposes. Bilateral CI positioning significantly deteriorates the anatomical visibility. CI positioning might play a crucial role for patients who need post-operative MRI surveillance.

Eyeblink conditioning contingent on hippocampal theta enhances hippocampal and medial prefrontal responses

2011 ◽  
Vol 105 (5) ◽  
pp. 2213-2224 ◽  
Author(s):  
Ryan D. Darling ◽  
Kanako Takatsuki ◽  
Amy L. Griffin ◽  
Stephen D. Berry
Keyword(s):  
Neural Activity ◽  
Theta Rhythm ◽  
Eyeblink Conditioning ◽  
Trace Conditioning ◽  
Distributed Network ◽  
Field Potentials ◽  
Trace Interval ◽  
Behavioral Learning ◽  
Paired Group ◽  
Hippocampal Theta

Trace eyeblink classical conditioning (tEBCC) can be accelerated by making training trials contingent on the naturally generated hippocampal 3- to 7-Hz theta rhythm. However, it is not well-understood how the presence (or absence) of theta affects stimulus-driven changes within the hippocampus and how it correlates with patterns of neural activity in other essential trace conditioning structures, such as the medial prefrontal cortex (mPFC). In the present study, a brain-computer interface delivered paired or unpaired conditioning trials to rabbits during the explicit presence (T+) or absence (T−) of theta, yielding significantly faster behavioral learning in the T+-paired group. The stimulus-elicited hippocampal unit responses were larger and more rhythmic in the T+-paired group. This facilitation of unit responses was complemented by differences in the hippocampal local field potentials (LFP), with the T+-paired group demonstrating more coherent stimulus-evoked theta than T−-paired animals and both unpaired groups. mPFC unit responses in the rapid learning T+-paired group displayed a clear inhibitory/excitatory sequential pattern of response to the tone that was not seen in any other group. Furthermore, sustained mPFC unit excitation continued through the trace interval in T+animals but not in T−animals. Thus theta-contingent training is accompanied by 1) acceleration in behavioral learning, 2) enhancement of the hippocampal unit and LFP responses, and 3) enhancement of mPFC unit responses. Together, these data provide evidence that pretrial hippocampal state is related to enhanced neural activity in critical structures of the distributed network supporting the acquisition of tEBCC.

IgG modulation in male mice with reproductive failure after prenatal inflammation

Reproduction ◽  
2021 ◽  
Author(s):  
Marina Izvolskaia ◽  
Vasilina Ignatiuk ◽  
Ayshat Ismailova ◽  
Viktoria Sharova ◽  
Liudmila Zakharova
Keyword(s):  
Positive Impact ◽  
Brain Structures ◽  
Peritoneal Macrophages ◽  
The Body ◽  
Male Rats ◽  
Male Mice ◽  
Prenatal Inflammation ◽  
Exposure In Vivo

Sexual performance in adult male rats is highly sensitive to prenatal stress which can affect the functionality of the reproductive system and various brain structures involved in modulating sexual behavior. The immunomodulatory effect of mouse IgG on reproductive maturity in male offspring after LPS exposure in vivo and in vitro was studied. Prenatal IgG injection (20 µg / mouse) had a positive impact on the puberty of male mice whose mothers were exposed to LPS (100 µg / kg) on the 12th day of pregnancy. The number of Sertoli cells were increased, whereas the body weight and the number of symplastic spermatids were decreased in offspring as compared to LPS-treated animals. Besides, IgG had a positive effect on altered hormone levels: reduced estradiol level on the 5th and 14th postnatal days and increased testosterone level on the 30th postnatal day in blood that led to an increased number of mounting attempts in sexually mature males. The cAMP-dependent pathway may be involved in the regulation of the LPS-induced inflammation. IgG reduced the increased level of cAMP in mouse peritoneal macrophages activated by LPS in vitro. IgG is able to modulate inflammation processes, but its exposure time is important.

scholarly journals Cerebellar implementation of movement sequences through feedback

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Andrei Khilkevich ◽  
Juan Zambrano ◽  
Molly-Marie Richards ◽  
Michael Dean Mauk
Keyword(s):  
Purkinje Cells ◽  
Cerebellar Cortex ◽  
General Framework ◽  
Eyelid Conditioning ◽  
Mossy Fibers ◽  
Learning Processes ◽  
Single Component ◽  
Associate Learning ◽  
Stimulation Of

Most movements are not unitary, but are comprised of sequences. Although patients with cerebellar pathology display severe deficits in the execution and learning of sequences (Doyon et al., 1997; Shin and Ivry, 2003), most of our understanding of cerebellar mechanisms has come from analyses of single component movements. Eyelid conditioning is a cerebellar-mediated behavior that provides the ability to control and restrict inputs to the cerebellum through stimulation of mossy fibers. We utilized this advantage to test directly how the cerebellum can learn a sequence of inter-connected movement components in rabbits. We show that the feedback signals from one component are sufficient to serve as a cue for the next component in the sequence. In vivo recordings from Purkinje cells demonstrated that all components of the sequence were encoded similarly by cerebellar cortex. These results provide a simple yet general framework for how the cerebellum can use simple associate learning processes to chain together a sequence of appropriately timed responses.

In Vivo Atlas of Deep Brain Structures

2002 ◽  
Author(s):  
Sebastiano Lucerna ◽  
Francesco M. Salpietro ◽  
Concetta Alafaci ◽  
Francesco Tomasello
Keyword(s):  
Brain Structures ◽  
Deep Brain
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