Activity in the pontine reticular nuclei scales with handgrip force in humans

The neural pathways that contribute to force production in humans are currently poorly understood, as the relative roles of the corticospinal tract and brainstem pathways, such as the reticulospinal tract (RST), vary substantially across species. Using functional magnetic resonance imaging (fMRI), we aimed to measure activation in the pontine reticular nuclei (PRN) during different submaximal handgrip contractions to determine the potential role of the PRN in force modulation. Thirteen neurologically intact participants (age: 28 ± 6 yr) performed unilateral handgrip contractions at 25%, 50%, 75% of maximum voluntary contraction during brain scans. We quantified the magnitude of PRN activation from the contralateral and ipsilateral sides during each of the three contraction intensities. A repeated-measures ANOVA demonstrated a significant main effect of force (P = 0.012, [Formula: see text] = 0.307) for PRN activation, independent of side (i.e., activation increased with force for both contralateral and ipsilateral nuclei). Further analyses of these data involved calculating the linear slope between the magnitude of activation and handgrip force for each region of interest (ROI) at the individual-level. One-sample t tests on the slopes revealed significant group-level scaling for the PRN bilaterally, but only the ipsilateral PRN remained significant after correcting for multiple comparisons. We show evidence of task-dependent activation in the PRN that was positively related to handgrip force. These data build on a growing body of literature that highlights the RST as a functionally relevant motor pathway for force modulation in humans.NEW & NOTEWORTHY In this study, we used a task-based functional magnetic resonance imaging (fMRI) paradigm to show that activity in the pontine reticular nuclei scales linearly with increasing force during a handgrip task. These findings directly support recently proposed hypotheses that the reticulospinal tract may play an important role in modulating force production in humans.

Change of ascending reticular activating system with recovery from vegetative state to minimally conscious state in a stroke patient

RATIONALE

We report on a stroke patient who showed change of the ascending reticular activating system (ARAS) concurrent with recovery from a vegetative state (VS) to a minimally conscious state (MCS), which was demonstrated on diffusion tensor tractography (DTT).

PATIENT CONCERNS

A 59-year-old male patient underwent CT-guided stereotactic drainage 3 times for management of intracerebral hemorrhage and intraventricular hemorrhage.

DIAGNOSIS

After 4 months from onset, when starting rehabilitation, the patient showed impaired consciousness, with a Glasgow Coma Scale (GCS) score of 6 and a Coma Recovery Scale-Revised score of 2. At 10 months after onset, his GCS score had recovered to 11 with a GRS-R score of 20, and he was able to perform rock-scissors-paper using his right hand according to verbal command.

INTERVENTIONS

On 10-month DTT, marked increased neural connectivity of the thalamic intralaminar nucleus (ILN) to the cerebral cortex was observed in both prefrontal cortexes and the right thalamus compared with 4-month DTT. However, no significant change was observed in the lower dorsal ARAS between the pontine reticular formation (PRF) and the thalamic ILN. In addition, the reconstructed lower ventral ARAS between the PRF and hypothalamus had disappeared in both hemispheres on 10-month DTT.

OUTCOMES

Change of the ARAS was demonstrated in a stroke patient who showed recovery from a VS to an MCS.

LESSONS

It appeared that the prefrontal cortex and thalamus, which showed increased neural connectivity, contributed to recovery from a VS to an MCS in this patient.

[EFFECTS OF ELECTRICAL STIMULATION OF NUCLEUS RETICULARIS PONTIS ORALIS ON THE SLEEP-WAKING STATES IN KRUSHINSKII-MOLODKINA STRAIN RATS]

The effects of electrical stimulation of nucleus reticularis pontis oralis on the behavior and brain electrical activity during all phases of the sleep-waking cycle was studied in Krushinskii-Molodkina strain rats, which have an inherited predisposition to audiogenic seizures. Electrical stimulation with 7 Hz frequency in the deep stage of slow-wave sleep cause appearance the fast-wave sleep. Similar stimulation during fast-wave sleep periods did not effects on the electrographic patterns and EEG spectral characteristics of hippocampus, visual, auditory and somatocnen nrnrenc nf the cnrtey ThPe sfimul1stinns did nnt break a fast-wave sleenhut increased almost twice due the duration of these sleep episodes. After electrical stimulation by same frequency during the wakeftlness and superficial slow-wave sleep states, the patterns and spectral characteristics of brain electrical activity in rats showed no significant changes as compared with controls. The results of this study indicate that the state of the animals sleep-waking cycle at the time of stimulation is a critical variable that influences the responses which are induced by electrical stimulation of the nucleus reticularis pontis oralis.

Projections from the oral pontine reticular nucleus to the spinal cord of the mouse

The present study investigated projections of the mouse oral pontine reticular nucleus (PnO) to the spinal cord by (a) injecting a retrograde tracer fluoro-gold (FG) to the lumbar cord and (b) an anterograde tracer biotinylated dextran amine (BDA) to PnO. We found that PnO projects to the entire spinal cord with an ipsilateral predominance. PnO fibers mainly travel in the ipsilateral ventral funiculus in the entire cord, terminating in laminae 7-10 with a lower density of fibers and boutons in lower segments. A small number of fibers travel in the contralateral ventral funiculus in the cervical cord with a similar terminating pattern to the ipsilateral counterpart. The present study is the first demonstration of PnO fiber terminals in the mouse spinal cord. This pathway might be responsible for muscle atonia during REM sleep, but needs physiological research to confirm this.