Stimulation Of Pontine Reticular Formation Research Articles

Prefrontal-hippocampal coupling by theta rhythm and by 2-5Hz oscillation in the delta band: The role of the nucleus reuniens of the thalamus.

Rhythmic synchronizations of hippocampus (HC) and prefrontal cortex (PFC) at theta frequencies (4-8Hz) are thought to mediate key cognitive functions, and disruptions of HC-PFC coupling were implicated in psychiatric diseases. Theta coupling is thought to represent a HC-to-PFC drive transmitted via the well-described unidirectional HC projection to PFC. In comparison, communication in the PFC-to-HC direction is less understood, partly because no known direct anatomical connection exists. Two recent findings, i.e., reciprocal projections between the thalamic nucleus reuniens (nRE) with both PFC and HC and a unique 2-5Hz rhythm reported in the PFC, indicate, however, that a second low-frequency oscillation may provide a synchronizing signal from PFC to HC via nRE. Thus, in this study, we recorded local field potentials in the PFC, HC, and nRE to investigate the role of nRE in PFC-HC coupling established by the two low-frequency oscillations. Using urethane-anesthetized rats and stimulation of pontine reticular formation to experimentally control the parameters of both forebrain rhythms, we found that theta and 2-5Hz rhythm were dominant in HC and PFC, respectively, but were present and correlated in all three signals. Removal of nRE influence, either statistically (by partialization of PFC-HC correlation when controlling for the nRE signal) or pharmacologically (by lidocaine microinjection in nRE), resulted in decreased coherence between the PFC and HC 2-5-Hz oscillations, but had minimal effect on theta coupling. This study proposes a novel thalamo-cortical network by which PFC-to-HC coupling occurs via a 2-5Hz oscillation and is mediated through the nRe.

Overactive Bladder and Pontine Reticular Formation

Background: The etiology of overactive bladder (OAB) remains unclear. Observed neurogenic factors in the literature are limited to suprapontine or spinal pathologies. The blink reflex is a useful tool in the evaluation of brainstem functions. Blink reflex latency times were evaluated in order to reveal pathology in the brainstem. Methods: A total of 60 women, 30 patients with idiopathic OAB and 30 healthy controls, were enrolled in the study. Blink reflex latency times were analyzed by electrical stimulation of the supraorbital nerve. Two responses in the orbicularis oculi muscle, early ipsilateral response (R1) and late bilateral response (R2) latency times, were recorded. Results: Mean ages of the patients and controls were 51.9 ± 5.3 and 49.2 ± 6.2 years, respectively. R2 latency times were significantly higher in patients than in controls. However, R1 latency times were similar between the two groups. Conclusions: The results of the study suggest a significant relation between late blink latency times and OAB. An oligosynaptic path via the trigeminal nuclei is responsible for R1; however, R2 response is relayed through the reticular formation. Stimulation of pontine reticular formation inhibits micturition contraction. In some patients, idiopathic OAB may result from reticular formation-originated pathology. Additional studies on other reticular formation-mediated reflexes are needed to reveal possible dysfunction of reticular formation.

Coordination of eye and head components of movements evoked by stimulation of the paramedian pontine reticular formation

Constant frequency microstimulation of the paramedian pontine reticular formation (PPRF) in head-restrained monkeys evokes a constant velocity eye movement. Since the PPRF receives significant projections from structures that control coordinated eye-head movements, we asked whether stimulation of the pontine reticular formation in the head-unrestrained animal generates a combined eye-head movement or only an eye movement. Microstimulation of most sites yielded a constant-velocity gaze shift executed as a coordinated eye-head movement, although eye-only movements were evoked from some sites. The eye and head contributions to the stimulation-evoked movements varied across stimulation sites and were drastically different from the lawful relationship observed for visually-guided gaze shifts. These results indicate that the microstimulation activated elements that issued movement commands to the extraocular and, for most sites, neck motoneurons. In addition, the stimulation-evoked changes in gaze were similar in the head-restrained and head-unrestrained conditions despite the assortment of eye and head contributions, suggesting that the vestibulo-ocular reflex (VOR) gain must be near unity during the coordinated eye-head movements evoked by stimulation of the PPRF. These findings contrast the attenuation of VOR gain associated with visually-guided gaze shifts and suggest that the vestibulo-ocular pathway processes volitional and PPRF stimulation-evoked gaze shifts differently.

Projections of vertical eye movement-related and head rotation-related neurons in the medial mesodiencephalic junction to pontine reticular formation in cat

Spikes of single neurons related to vertical eye movements and vertical head rotation were recorded extracellularly in the medial mesodiencephalic junction (MDJ) of chronically prepared alert cats, and their antidromic responses to stimulation of the pontine reticular formation (PRF) were studied. Among the vertical eye movement-related neurons, augmenting neurons (ANs) and tonic neurons (TNs) were activated antidromically from the lateral PRF. Stimulation of the midline PRF activated antidromically mainly ANs, long-lead burst neurons (LLBNs) and upward medium-lead burst neurons (MLBNs). The head rotation-related neurons were antidromically activated from the lateral PRF but not from the midline PRF. These results suggest that some MDJ neurons related to vertical eye movements or head rotation directly project to the paramedian PRF.

Effects of stimulation of pontine and bulbar reticular formation upon spinal motoneurons of the cat.

1. Pontine and bulbar reticular formation (RF) and Deiters' nucleus were stimulated stereotaxically with brief electric stimuli (2-3msec.) and their effects. on the intracellular potential of lumbar alpha motoneurons as wall as on the size of monosynaptic reflex were studied in the cat. Secondary effects through. the gamma efferents-muscle spindle loop were eliminated.2. Stimulation of pontine RF, especially its rostral part, produced a marked inhibition of extensor monosynaptic reflex at a latency of 15-20msec. and a slight facilitation of flexor monosynaptic reflex at a latency of about 10msec.3. Stimulation of Deiters' nucleus was facilitatory to extensor monosynaptic reflex. The facilitation appeared in two separate phases, the one set up at a latency of less than 10msec. with relatively short and simple time course and the other at a latency of 15-20msec. with a longer duration.4. The effect of stimulation of the bulbar RF varied extensively with a, slight change in the electrode position. The most prevalent effect was facilitatory to extensor monosynaptic reflex, which in some cases resembled that of Deiters' nucleus in its time course.5. Generally speaking, changes by stimulation of intracellular potential of spinal motoneurons reflected the influences elicitable from the same site upon the size of monosynaptic reflex. Facilitatory or inhibitory influence upon the reflex size could mostly be accounted for by the potential change of the motoneuron membrane which was most likely due to EPSP's and IPSP's.6. Single spinal motoneurons fired from different levels of depolarization, when the rate of rise of depolarizing PSP's was different according to the stimulated site in the brain stem.7. The effect of repetitive stimulation of the RF on the membrane potential. of single spinal motoneurons could be illustrated in general as a summated. effect of single stimulation of the same site.8. Tonic suprasegmental influences and their modification by reticular stimulation were visualized as maintained discharges of descending tract fibers and. spinal interneurons.9. A hypothetical accout for the decerebrate rigidity was put forward based on the present findings.