Psychobiological evidence of the stress resilience fostering properties of a cosmetic routine.

Everyday life psychosocial stressors contribute to poor health and disease vulnerabilty. Means alternative to pharmacotherapy that are able to foster stress resilience are more and more under the magnifying glass of biomedical research. The aim of this study was to test stress resilience fostering properties of the self-administration of a cosmetic product enriched with essential oils. On day 0, fourty women, 25-50 years old, self-administered both the enriched cosmetic product (ECP) and a placebo one (PCP). Then, women were randomized for daily self-administration (from day 1 to 28) of either ECP (n = 20) or PCP (n = 20). On day 29, subjects underwent a psychosocial stress test (PST). Autonomic (heart rate and its variability) and neuroendocrine (salivary cortisol) parameters were assessed both on day 0 and 29. All subjects filled a number of psychological questionnaires in order to quantify anxiety, perceived stress, and mood profile, and were videorecorded during PST for non-verbal behavior evaluation. A single application of ECP produced an acute potentiation of cardiac parasympathetic modulation, which was not observed when placebo was used. Prolonged self-administration of ECP induced: (i) a dampening of the cortisol rise produced by PST, (ii) a reduction of state anxiety, (iii) a favorable change in mood profile, and (iv) a reduction of non-verbal behavior patterns that signal anxiety, motivational conflict and avoidance. In conclusion, this study suggests that the self-administration of a cosmetic cream enriched with essential oils should be considered as a stress resilience fostering strategy due to its favorable physiological, neuroendocrine and psychological effects.

The cerebellum monitors errors and entrains executive networks.

Frontal midline θ (Fmθ) activity occurs in medial prefrontal cortices (mPFC), when expected and actual outcomes conflict. Cerebellar forward models could inform the mPFC about this mismatch. To verify this hypothesis we correlated the mPFC activation during a visuomotor tracking task (VM) with performance accuracy, in control and cerebellum-lesioned participants. Additionally, purely visual (V), motor (M) and a motor plus visual tasks (V + M) were performed. An Independent Component, with a mid-frontal topography scalp map and equivalent dipole location in the dorsal anterior cingulate cortex accounted for Fmθ. In control participants Fmθ power increased during VM, when the error level crossed a threshold, but not during V + M, M and V. This increase scaled with tracking error. Fmθ power failed to increase during VM in cerebellar participants, even at highest tracking errors. Thus, in control participants, activation of mPFC is induced when a continuous monitoring effort for online error detection is required. The presence of a threshold error for enhancing Fmθ, suggests the switch from an automatic to an executive tracking control, which recruits the mPFC. Given that the cerebellum stores forward models, the absence of Fmθ increases during tracking errors in cerebellar participants indicates that cerebellum is necessary for supplying the mPFC with prediction error-related information. This occurs when automatic control falters, and a deliberate correction mechanism needs to be triggered. Further studies are needed to verify if this alerting function also occurs in the context of the other cognitive and non-cognitive functions in which the cerebellum is involved.

A new technique to investigate vestibulo-spinal reflexes.

Vestibulospinal reflexes can be elicited in humans by low amplitudes direct (galvanic) currents lasting tens of milliseconds and applied across the two mastoids bones, which can be delivered by particular stimulators. The stimulus induces a perception of body sway and a postural response appropriate to counteract the perceived sway. Both the direction of the perceived and induced body sway are modulated by the orientation of the head with respect to the body. This phenomenon is due to the fact that integration of vestibular and neck signals allows to correctly infer the direction of body sway from the labyrinthine input, which is instead related to direction of head motion. The modulation of stimulus-elicited body sway by neck rotation could be utilised for testing the effectiveness of neck proprioceptive signals in modifying the reference frame for labyrinthine signals from the head to the body. In the present experiments we showed that labyrinthine stimulation can be performed also by using train of pulses of 1 msec duration, which can be delivered by virtually all stimulators allowed for human use. Moreover, we developed a simple technique for visualising the time course of the changes in the direction of the postural response, based on the evaluation of the velocity vector of subject's centre of pressure. This method could be exploited in order to the test the efficacy of neck proprioceptive information in modifying the reference frame for processing vestibular signals in both physiological and pathological condition.

Transjugular Intrahepatic Portosystemic Shunt and Laparoscopic Colorectal Resection: the ideal minimally-invasive management for the treatment of colorectal cancer in severe cirrhotic patients. A case report and literature review.

Surgical interventions on gastrointestinal tract are often not well tolerated by patients with cirrhosis and severe portal hypertension, impairing their prognosis if suffering from malignant disease. Combining the benefits of two minimally invasive techniques such as Transjugular intrahepatic portosystemic shunt (TIPS) and Laparoscopic Colorectal Resection (LCR), the complications related to surgical intervention might be reduced and thus, it allows patients with liver disease, to undergo a curative intervention. One patient with cirrhosis and portal hypertension diagnosed with a rectal cancer underwent a meticulous preoperative preparation through placement of TIPS before laparoscopic surgery. TIPS placement was performed without intraprocedure complications. The patient was successfully operated by laparoscopic technique 36 days after TIPS placement without intraoperative bleeding or postoperative complications. Our experience, despite being based on one case, allows us to conclude that decompression of portal system by TIPS, already used in open surgery, may be applicable as a preoperative laparoscopic procedure with equally satisfactory results.

Influence of obesity-susceptibility loci (MC4R and INSIG2) on the outcome of weight loss and amelioration of co-morbidity in obese patients treated by a gastric-bypass.

BACKGROUND: Genome-wide association and linkage studies have identified multiple susceptibility loci for obesity. OBJECTIVE: We hypothesized that such loci may affect weight loss and comorbidity amelioration outcomes following a gastric-bypass. DESIGN: A total of 200 obese patients who underwent a gastric bypass surgery were genotyped for single-nucleotide polymorphisms (SNPs) in insulin induced gene 2 (INSIG2) and melanocortin 4 receptor (MC4R) obesity genes. RESULTS: After a follow-up of 18 month, the patients (192) data of weight excess loss (72%) and co-morbidities (Hypertension -62- and Diabetes -39-) were analyzed and compared. 26 Patients with SNP were found (9 MC4R and 17 INSIG2). No significant differences in weight excess loss and amelioration of comorbidities were revealed. CONCLUSIONS: The data suggest no influence of weight excess loss and amelioration of co-morbidities after gastric-bypass by genetic susceptibility.

Can imagery become reality?

Previous studies showed that highly hypnotizable persons imagining a specific sensory context behave according to the corresponding real stimulation and perceive their behaviour as involuntary. The aim of the study was to confirm the hypothesis of a translation of sensory imagery into real perception and, thus, of a true involuntary response. We studied the imagery-induced modulation of the vestibulospinal (VS) reflex earlier component in highly (Highs) and low hypnotizable subjects (Lows), as it is not affected by voluntary control, its amplitude depends on the stimulus intensity, and the plane of body sway depends on the position of the head with respect to the trunk. Results showed that the effects of the "obstructive" imagery of anaesthesia are different from those elicited by the "constructive" imagery of head rotation. Indeed, both Highs and Lows having their face forward and reporting high vividness of imagery experienced anaesthesia and reduced their VS reflex amplitude in the frontal plane, while only Highs changed the plane of body sway according to the imagined head rotation that is from the frontal to the sagittal one. These effects cannot be voluntary and should be attributed to translation of sensory imagery into the corresponding real perception.

Modulation of the postural effects of cognitive load by hypnotizability.

Aim of the experiment was to study whether cognitive load affects postural control more in low (Lows) than in highly hypnotizable (Highs) subjects due to the latter's greater attentional abilities. Standing Highs and Lows underwent an experimental session (closed eyes) consisting of a basal condition and of mental computation in an easy (stable support) and a difficult (unstable support) postural condition. Variability [standard deviation (SD)] and complexity [sample entropy (SampEn)] of the movement of the centre of pressure (CoP), its mean velocity (Velocity), the area swept by the CoP (Area) and the ratio between the CoP trajectory length and area [length for surface (LFS)] were measured. Few hypnotizability-related differences were detected (reduction in the Highs' SD and increases in the Lows' LFS in the difficult postural condition). Thus, the hypnotizability-related postural differences observed in previous studies during sensory alteration could not be accounted mainly by attentional abilities.

Hypnotizability-dependent modulation of postural control: effects of alteration of the visual and leg proprioceptive inputs.

The aim of the experiment was to investigate whether the peculiar attentional/imagery abilities associated with susceptibility to hypnosis might make postural control in highly hypnotizable subjects (Highs) that are less vulnerable to sensory alteration than in individuals with low hypnotic susceptibility (Lows). The movement of the centre of pression (CoP) was monitored in Highs and Lows during alteration of the visual and leg proprioceptive input. The two groups responded differently to eyes closure and to an unstable support and the CoP movement was generally larger and faster in Highs. The stabilogram diffusion analysis indicated a different set point in Highs and Lows and suggested that the former are more independent of specific sensory information than the latter, likely due to different abilities in sensory re-weighting and/or peculiar internal models of postural control. The results are discussed within the general perspective of high pervasiveness of the hypnotizability trait, which modulates cognitive, autonomic and somatic functions.

Responses of Purkinje-cells of the cerebellar anterior vermis to stimulation of vestibular and somatosensory receptors.

In decerebrate cats, sinusoidal rotation of the forepaw around the wrist modifies the activity of the ipsilateral forelimb extensor triceps brachii (TB) and leads to plastic changes of adaptive nature in the gain of vestibulospinal (VS) reflexes (VSRs). Both effects are depressed by functional inactivation of the cerebellar anterior vermis, which also decreases the gain of VSRs. In order to better understand the mechanisms of these phenomena, the simple spike activity of Purkinje (P-) cells was recorded from the vermal cortex of the cerebellar anterior lobe during individual and/or combined stimulation of somatosensory wrist, neck and vestibular receptors. About one third of the recorded units were affected by sinusoidal rotation of the ipsilateral forepaw around the wrist axis (0.16 Hz, +/-10 degrees ). Most of these neurons ( approximately 60%) increased their activity during ventral flexion of the wrist and decreased it during the oppositely directed movement, with an average phase lag of -141 degrees with respect to the position of maximal dorsiflexion. The remaining cells ( approximately 40%) were excited during dorsiflexion of the wrist, with an average phase lead of 59 degrees with respect to the extreme dorsal flexion. Both populations showed comparable response gains, with an average value of 0.42+/-0.52, S.D., imp/s/deg. About half of the recorded units were also tested during sinusoidal roll tilt of the animal around the longitudinal axis (0.16 Hz, +/-10 degrees ), leading to stimulation of labyrinthine receptors. When both stimuli were applied simultaneously, the responses to combined stimulation usually corresponded to the sum of individual responses. While the phase distribution of somatosensory responses was clearly bimodal, vestibular responses showed phase angle values uniformly scattered between +/-180 degrees and 0 degrees , so that, during combined stimulation, each neuron could be maximally activated by coupling the two stimuli with a particular phase relation. Finally, a proportion of the recorded neurons was also tested during sinusoidal rotation of the body around its longitudinal axis, with the head fixed in space, leading to stimulation of neck receptors. The proportion of neurons affected by individual stimulation of vestibular or neck receptors (81% and 72%, respectively) was larger than that of wrist-driven neurons. Convergence of signals from vestibular, somatosensory wrist and neck receptors was found in 18% of the neurons analyzed. In conclusion, the results of this study show that somatosensory signals from the forelimb: i) modulate the activity of a sizeable proportion of neurons located within the cerebellar anterior vermis and ii) interact widely with labyrinthine and neck signals at this level. Moreover, iii) this corticocerebellar region is largely dominated by vestibular and neck signals that may be utilized to build up a neuronal representation of the position of body in space. These findings suggest that: 1) the modulation of TB activity induced by rotation of the ipsilateral wrist may at least partially depend upon the simultaneous changes in P-cell activity and 2) the interaction of vestibular and somatosensory wrist signals at P-cell level may represent the substrate of the plastic changes that affect the VSR when animal tilt and wrist rotation are driven together. A preliminary report of these data has been presented [ Responses of cerebellar Purkinje cells to forepaw rotation in decerebrate cat. Pflügers Arch 440:R31].

Effects of bicuculline application on the somatosensory responses of secondary vestibular neurons.

Limb somatosensory signals modify the discharge of vestibular neurons and elicit postural reflexes, which stabilize the body position. The aim of this study was to investigate the contribution of the γ-amino-butyric-acid (GABA) to the responsiveness of vestibular neurons to somatosensory inputs. The activity of 128 vestibular units was recorded in anesthetized rats in resting conditions and during sinusoidal foreleg rotation around the elbow or shoulder joints (0.026-0.625Hz, 45° peak amplitude). None of the recorded units was influenced by elbow rotation, while 40% of them responded to shoulder rotation. The selective GABAA antagonist receptor, bicuculline methiodine (BIC), was applied by microiontophoresis on single vestibular neurons and the changes in their activity at rest and during somatosensory stimulation was studied. In about half of cells the resting activity increased after the BIC application: 75% of these neurons showed also an increased response to somatosensory inputs whereas 17% exhibited a decrease. Changes in responsiveness in both directions were detected also in the units whose resting activity was not influenced by BIC. These data suggest that the responses of vestibular neurons to somatosensory inputs are modulated by GABA through a tonic release, which modifies the membrane response to the synaptic current. It is also possible that a phasic release of GABA occurs during foreleg rotation, shaping the stimulus-elicited current passing through the membrane. If this is the case, the changes in the relative position of body segments would modify the GABA release inducing changes in the vestibular reflexes and in learning processes that modify their spatio-temporal development.

[Endovascular versus conventional vascular surgery--old-fashioned thinking? Part 2: carotid artery stenosis and peripheral arterial occlusive disease]. / Endovaskuläre vs. konventionelle Gefäßchirurgie--antiquiertes Denken? Teil 2: Karotisstenose und periphere arterielle Verschlusskrankheit.

Endovascular therapy has widely replaced conventional open vascular surgical reconstruction. For this reason, both techniques were widely considered to be competing approaches. Evidence-based data from randomized prospective trials, meta-analyses and clinical registries, however, demonstrated that both techniques should be used to complement each other. It became increasingly more evident that the use of either procedure depends on the underlying disease and the anatomical conditions, whereby a combination of both (hybrid approach) may be the preferred option in certain situations. This review focuses on the treatment of patients with carotid artery stenosis, intermittent claudication, critical limb ischemia and acute limb ischemia.

[Endovascular versus conventional vascular surgery - old-fashioned thinking? Part 1: interventions on the aorta]. / Endovaskuläre vs. konventionelle Gefäßchirurgie - antiquiertes Denken? Teil 1: Eingriffe an der Aorta.

Endovascular therapy has widely replaced conventional open vascular surgical reconstruction. For this reason both techniques were widely considered to be competing approaches. Evidence-based data from randomized prospective trials, meta-analyses and clinical registries, however, demonstrated that both techniques should be used to complement each other. It became increasingly more evident that the use of either procedure depends on the underlying disease and the anatomical conditions, whereby a combination of both (hybrid approach) may be the preferred option in certain situations. This review focuses on the treatment of complicated acute type B aortic dissection, descending thoracic aortic aneurysms, thoracoabdominal aortic aneurysms as well as asymptomatic and ruptured abdominal aortic aneurysms.

Adaptive modification of the cats vestibulospinal reflex during sustained and combined roll tilt of the whole animal and forepaw rotation: cerebellar mechanisms.

In decerebrate cats, the electromyogram (EMG) activity of the forelimb extensor triceps brachii (TB) increases during side-down roll tilt of the whole animal (vestibulospinal reflex, VSR) at about 0.15 Hz. (+/-10 degrees ), while decreases during side up tilt. On the other hand, the TB activity increases during dorsal flexion of the ipsilateral forepaw (0.15 Hz, +/-5 degrees-10 degrees ), but decreases during ventral flexion. In six experiments, these stimuli were synergistically associated (side-down tilt coincided with dorsal flexion of the forepaw), so that the EMG modulation of the TB activity was greater than that induced by the individual stimuli. During a 3-h period of this sustained stimulation, the amplitude of the pure VSR progressively increased to reach the maximum value at the end of the third hour and persisted unmodified during the post-adaptation period (1 h). In three experiments, animal tilt and forepaw rotation were antagonistically associated (side-down tilt coincided with ventral flexion of the forepaw). In these instances the VSR gain remained on the average stable, but, at the end of the 3-h period of combined stimulation, a proportion of TB responses to animal tilt showed a phase reversal. In a digitigrade animal like the cat, a dorsal flexion of the wrist is associated with a decrease in limb length and would occur when the extensor tone is not appropriate to support body weight; we propose, therefore, that somatosensory volleys elicited by wrist rotation modify the gain of VSR so as to maintain postural stability. Inactivation, on the side of muscle recording, of the corticocerebellar region which projects to the lateral vestibular nucleus of Deiters, by local microinjection of the GABA-A agonist muscimol (0.5 microl at 16 microg/microl), decreased the already adapted gain of VSR. In conclusion, the results of this study suggest that somatosensory reafferent inputs to the cerebellar vermis are used to plastically modify the gain of VSR, when external forces produce changes in the final posture of the foot during animal tilt.

Spatiotemporal response properties of cerebellar Purkinje cells to animal displacement: a population analysis.

The hypothesis that corticocerebellar units projecting to vestibulospinal neurons contribute to the spatiotemporal response characteristics of forelimb extensors to animal displacement was tested in decerebrate cats in which the activity of Purkinje cells and unidentified cells located in the cerebellar anterior vermis was recorded during wobble of the whole animal. This stimulus imposed to the animal a tilt of fixed amplitude (5 degrees) with a direction moving at a constant angular velocity (56.2 degrees/s), both in the clockwise and counterclockwise directions over the horizontal plane. Eighty-three percent (143/173) of Purkinje cells and 81% (42/52) of unidentified cells responded to clockwise and/or counterclockwise rotations. In particular, 116/143 Purkinje cells (81%) and 32/42 unidentified cells (76%) responded to both clockwise and counterclockwise rotations (bidirectional units), while 27/143 Purkinje cells (19%) and 10/42 unidentified cells (24%) responded to wobble in one direction only (unidirectional units). For the bidirectional units, the direction of maximum sensitivity to tilt (Smax) was identified. Among these units, 24% of the Purkinje cells and 26% of the unidentified cells displayed an equal amplitude of modulation during clockwise and counterclockwise rotations, indicating a cosine-tuned behavior. For this unit type, the temporal phase of the response to a given direction of tilt should remain constant, while the sensitivity would be maximal along the Smax direction, declining with the cosine of the angle between Smax and the tilt direction. The remaining bidirectional units, i.e. 57% of the Purkinje cells and 50% of the unidentified cells displayed unequal amplitudes of modulation during clockwise and counterclockwise rotations. For these neurons, a non-zero sensitivity along the null direction is expected, with a response phase varying as a function of stimulus direction. As to the unidirectional units, their responses to wobble in one direction predict equal sensitivities along any tilt direction in the horizontal plane and a response phase that changes linearly with the stimulus direction. By comparing these data with those obtained previously during selective stimulation of macular receptors by a 5 degrees off-vertical axis rotation, it appeared that the directions of maximum sensitivity to tilt were distributed over the whole horizontal plane of stimulation, in both conditions. However, co-stimulation of macular and canal receptors during wobble decreased the proportion of unidirectional units, while that of the bidirectional, namely broadly tuned units, increased. In addition, while the average gain of the Smax vector of the bidirectional units was comparable, the temporal phase of this vector tended to show a more prominent phase leading behavior during wobble with respect to off-vertical axis rotation. The possibility that the tested neurons formed a population which coded the direction of head tilt in space was also investigated using a modified version of the classical population vector analysis. It was shown that for each selected time in the tilt cycle the direction of the population vector closely corresponded to that of the head tilt, while its amplitude was related to that of the stimulus. We conclude that the broad distribution of the response vector orientation of units located in the cerebellar anterior vermis represents an appropriate substrate for the cerebellar control of vestibulospinal reflexes involving extensor muscles during a variety of head tilts. In view of their efferent projections to the vestibular and fastigial nuclei, the cerebellar anterior vermis may provide a framework for the spatial coding of vestibular inputs, giving equal emphasis to both side-to-side and fore-aft stability.

Spatiotemporal response properties of cerebellar Purkinje cells to neck displacement.

The activity of 184 Purkinje cells and 58 unidentified neurons located within the cerebellar anterior vermis was recorded in decerebrate cats during wobble of the body under a fixed head. This stimulus induced a neck displacement of constant amplitude (2.5 degrees) whose direction rotated at the constant velocity of 56.2 degrees/s on the horizontal plane, both in the clockwise and counterclockwise directions. It was then possible to evaluate the spatiotemporal characteristics of unit responses to neck displacement in the vertical planes; 131 of 184 Purkinje cells (71%) and 35 of 58 unidentified cells (60%) responded to clockwise and/or counterclockwise rotations. In particular, among the responsive units, 44% of the Purkinje cells and 37% of the unidentified cells showed an equal amplitude modulation during clockwise and counterclockwise rotations. These units are expected to show a maximal response sensitivity for neck displacement in a preferred direction, a null response for perpendicularly oriented stimuli and a constant temporal phase (narrowly tuned neurons). In 28% of the Purkinje cells and 40% of the unidentified cells, responses of different amplitudes were observed during clockwise and counterclockwise rotations. These neurons should display a preferred direction of response to neck displacement, lack of null response directions and a temporal phase changing with the stimulus direction (broadly tuned neurons). Finally, 27% of the Purkinje cells and 23% of the unidentified cells responded only to wobble in the clockwise or counterclockwise direction (unidirectional units). This behavior predicts equal sensitivities for all the directions of neck displacement and a response phase changing linearly with the direction of neck displacement. A maximal sensitivity vector (Smax), aligned with the preferred direction of the neuron, was evaluated for the bidirectional narrowly tuned and broadly tuned units. Its amplitude and temporal phase corresponded to the response characteristics expected for stimuli in the preferred direction of the cell. Smax directions were distributed over the horizontal plane. Most of them, however, were closer to the pitch than to the roll axis and pointed towards the animal's tail. Among pitch-related Purkinje cells, the temporal phase of Smax was small with a predominance of phase lags; phase leads of rather large amplitude were usually observed for roll-related Purkinje cells. The possibility that the recorded population of units coded the direction of neck displacement was tested by assuming that each cell gave a vectorial contribution related to its response properties and that the vectorial sum of such contributions represented the outcome of the population code. Dynamic body-to-head displacements in four different directions were simulated and for each direction 12 population vectors were evaluated at regular intervals of the stimulus cycle. The direction of the population vector was related to that of the stimulus, but the correspondence was close only for the pitch direction. Moreover, the amplitude of the population vector depended upon the direction of the stimulus, being larger for pitch than for roll displacements. Due to the efferent connections of the explored cerebellar region, the neuronal signals generated by the Purkinje cell population are probably transferred to the spinal cord, where they may differentially affect the amplitude and the spatial properties of the neck reflexes according to the direction of neck displacement.

Neck input modifies the reference frame for coding labyrinthine signals in the cerebellar vermis: a cellular analysis.

The activity of 68 neurons, mainly Purkinje cells, was recorded from the cerebellar anterior vermis of decerebrate cats during wobble of the whole animal (at 0.156 Hz, 5 degrees), a mixture of tilt and rotation, leading to stimulation of labyrinth receptors. Most of the neurons (65/68) were affected by both clockwise and counterclockwise rotations. Twenty-four units showing responses of comparable amplitude to these stimuli (narrowly tuned cells) were represented by a single vector (Smax), whose preferred direction corresponded to the direction of stimulation giving rise to the maximal response. The remaining 41 units, however, showed different amplitude responses to these rotations (broadly tuned cells) and were characterized by two spatially and temporally orthogonal vectors (Smax and Smin), suggesting that labyrinthine signals with different spatial and temporal properties converged on these cells. All these units were tested while the body was aligned with the head (control position), as well as after static displacement of the body under a fixed head by 15 degrees and/or 30 degrees around a vertical axis passing through C1-C2, thus leading to stimulation of neck receptors. The orientation component of the response vector of the Purkinje cells to vestibular stimulation changed following body-to-head displacement. Moreover, the amplitude of vector rotation corresponded, on the average, to that of body rotation. Changes in temporal phase, gain and tuning ratio of the responses were also observed. We propose that information from neck receptors regulates the convergence of labyrinthine signals with different spatial and temporal properties on corticocerebellar units. Due to their strict relationship with the motor system, these units may give rise to appropriate responses in the limb musculature, by modifying the spatial organization of the vestibulospinal reflexes according to the requirements of body stability. The cerebellar vermis may thus represent an important structure, where frames of reference can be altered to account for changes in position of trunk, head and neck.

Convergence and interaction of neck and macular vestibular inputs on reticulospinal neurons.

Extracellular recordings were obtained in decerebrate cats from neurons located in the inhibitory area of the medullary reticular formation, namely in the medial aspects of the nucleus reticularis gigantocellularis, magnocellularis and ventralis. Of 127 medullary reticular units examined, 77 were reticulospinal neurons antidromically identified following stimulation of the spinal cord at T12-L1; the remaining 50 neurons were not activated antidromically. Unit firing rate was analyzed under separate stimulation of macular vestibular, neck, or combined receptors by using sinusoidal rotations about the longitudinal axis at 0.026 Hz, 10 peak amplitude. Among the 127 reticular units, 84 (66.1%) responded with a periodic modulation of their firing rate to roll tilt of the animal and 93 (73.2%) responded to neck rotation. Convergence of macular and neck inputs was found in 71/127 (55.9%) reticular neurons; in these units, the gain as well as the sensitivity of the first harmonic of response corresponded on the average to 0.49 +/- 0.41, SD imp/s/deg and 5.10 +/- 4.27, SD %/deg for the neck responses and to 0.40 +/- 0.39, SD imp/s/deg and 3.90 +/- 3.80, SD %/deg for the macular responses, respectively. Most of the convergent reticular units were maximally excited by the direction of stimulus orientation, the first hormonic or responses showing an average phase lead of about +42.7 with respect to neck position and +24.9 with respect to animal position. Two populations of convergent neurons were observed. The first group of units (58/71, i.e. 81.7%) showed reciprocal ("out of phase") responses to the two inputs in that they were mainly excited during side-down neck rotation, but inhibited during side-down animal tilt. The remaining group of units (13/71, i.e. 18.3%) showed parallel ("in phase") responses to the two inputs and they were mainly excited by side-down neck rotation and animal tilt. The response characteristics of medullary reticular neurons to the combined neck and macular inputs, elicited during head rotation, closely corresponded to those predicted by a vectorial summation of the individual neck and macular responses. In particular, "out of phase" units displayed small amplitudes and large phase leads of the responses with respect to head position, when both types of receptors were costimulated. In contrast, "in phase" units displayed large amplitude and small phase leads during head rotation.(ABSTRACT TRUNCATED AT 400 WORDS)

Responses of medullary reticulospinal neurons to sinusoidal rotation of neck in the decerebrate cat.

The electrical activity of 132 neurons located in the inhibitory area of the medullary reticular formation, namely, in the medial aspects of the nucleus reticularis gigantocellularis, magnocellularis and ventralis has been recorded in precollicular decerebrate cats during sinusoidal displacement of the neck. This was achieved by rotation of the body about the longitudinal axis of the animal, while maintaining the head stationary. In particular, 85 neurons were activated antidromically by stimulation of the spinal cord at T12 and L1, the remaining 47 units were not activated antidromically. Among these reticular neurons tested, 66 out of 85 (i.e. 77.6%) of the neurons that were, and 31 out of 47 (i.e. 66.0%) of the neurons that were not antidromically activated responded to slow neck rotation at the frequency of 0.026 Hz and at the peak amplitude of displacement of 10 degrees. The units influenced by neck rotation showed a periodic modulation of the firing rate in response to sinusoidal stimulation of neck receptors. In particular, 70 of 97 units (i.e. 72.2%) were excited during side-down neck rotation and depressed during side-up rotation, while 19 of 97 units (i.e. 19.6%) showed the opposite pattern. In both instances, the peak of the responses occurred with an average phase lead of +41 degrees for the extreme side-up or side-down neck displacement. The remaining 8 units (i.e. 8.2%) showed a prominent phase shift of the peak of their response relative to neck position. The proportion of units excited during side-down neck rotation were almost equally distributed throughout the whole rostro-caudal extent of the reticular structures explored. Responses to neck rotation were detectable at 0.25 degrees of peak displacement. The gain (imp./s/deg.) and the sensitivity (%/deg., i.e. percentage change of the mean firing rate per degree of displacement) in responses of reticulospinal neurons decreased by increasing the peak amplitude of neck rotation from 1 to 10 degrees at a frequency of 0.026 Hz. Therefore, the system did not behave linearly with respect to amplitude of stimulation. By increasing the frequency of stimulation from 0.008 to 0.32 Hz at the fixed amplitude of 10 degrees, the gain, sensitivity and phase lead of responses increased for frequencies of neck rotation above 0.051 Hz. Reticulospinal neurons may thus monitor changes in neck position as well as in velocity of neck rotation. Responses of reticulospinal neurons to neck rotation are discussed in relation to the responses to the same stimulus recently described of vestibulospinal neurons originating from the lateral vestibular nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Responses of locus coeruleus and subcoeruleus neurons to sinusoidal neck rotation in decerebrate cat.

The electrical activity of 99 neurons located in the locus coeruleus-complex, namely in the dorsal (n = 26) and the ventral part of the locus coeruleus (n = 46) as well as the locus subcoeruleus (n = 27), has been recorded in precollicular decerebrate cats during sinusoidal displacement of the neck. This was achieved by rotation of the body about the longitudinal axis of the animal, while maintaining the head stationary. A proportion of these neurons showed some of the main physiological characteristics attributed to the noradrenergic locus coeruleus neurons, i.e. (i) a slow and regular resting discharge, and (ii) a typical biphasic response to fore and hindpaw compression consisting of short bursts of impulses followed by a period of quiescence, due at least in part to recurrent or lateral inhibition of the corresponding neurons. Moreover, 14 out of the 99 neurons were activated antidromically by stimulation of the spinal cord at T12 and L1, thus being considered as coeruleo- or subcoeruleospinal neurons. Among these locus coeruleus-complex neurons tested, 73 out of 99 (i.e. 73.7%) responded to neck rotation at the standard frequency of 0.15 Hz and at the peak amplitude of displacement of 10 degrees. In particular 40 of 73 units (i.e. 54.8%) were excited during side-down neck rotation and depressed during side-up rotation, while 18 of 73 units (i.e. 24.7%) showed the opposite pattern. In both instances the peak of the responses occurred with an average phase lead of +34.2 degrees for the extreme side-down or side-up neck displacement; however, the response gain (impulses/s per deg) was on the average more than two-fold higher in the former than in the latter group of units. The remaining 15 units (i.e. 20.5%) showed phase angle values which were intermediate between those of the two main populations. As to the coeruleo or subcoeruleospinal neurons, 11 of 14 units (78.6%) responded to the neck input, the majority (nine of 11 units, i.e. 81.8%) being excited during side-down neck rotation. Within the explored region, the proportion of responsive units was higher in the locus subcoeruleus (85.2%) than in the locus coeruleus, both dorsal and ventral (69.4%). Moreover, units located in the former structure showed on the average a response gain higher than that found in the latter structures. Similar results were also obtained from the population of locus subcoeruleus-complex neurons which fired at a low rate (less than or equal to 5.0 impulses/s).(ABSTRACT TRUNCATED AT 400 WORDS)

Responses of locus coeruleus and subcoeruleus neurons to sinusoidal stimulation of labyrinth receptors.

In precollicular decerebrate cats the electrical activity of 141 individual neurons located in the locus coeruleus-complex, i.e. in the dorsal (n = 41) and ventral parts (n = 67) as well as in the locus subcoeruleus (n = 33), was recorded during sinusoidal tilt about the longitudinal axis of the whole animal, leading to stimulation of labyrinth receptors. Some of these neurons showed physiological characteristics attributed to the norepinephrine-containing locus coeruleus neurons, namely, (i) a slow and regular resting discharge, and (ii) a typical biphasic response to fore- and hindpaw compression consisting of short impulse bursts followed by a silent period, which has been attributed to recurrent and/or lateral inhibition of the norepinephrine-containing neurons. Furthermore, 16 out of the 141 neurons were activated antidromically by stimulation of the spinal cord at T12 and L1, thus being considered coeruleospinal or subcoeruleospinal neurons. A large number of tested neurons (80 out of 141, i.e. 56.7%) responded to animal rotation at the standard frequency of 0.15 Hz and at the peak amplitude of 10 degrees. However, the proportion of responsive neurons was higher in the locus subcoeruleus (72.7%) and the dorsal locus coeruleus (61.0%) than in the ventral locus coeruleus (46.3%). A periodic modulation of firing rate of the units was observed during the sinusoidal stimulus. In particular, 45 out of the 80 units (i.e. 56.2%) were excited during side-up and depressed during side-down tilt (beta-responses), whereas 20 of 80 units (i.e. 25.0%) showed the opposite behavior (alpha-responses). In both instances, the response peak occurred with an average phase lead of about + 18 degrees, with respect to the extreme side-up or side-down position of the animal; however, the response gain (imp./s per deg) was, on average, more than two-fold higher in the former than in the latter group. The remaining 15 units (i.e. 18.7%) showed a prominent phase shift of this response peak with respect to animal position. Similar results were obtained from the subpopulation of locus coeruleus-complex neurons which fired at a low rate (less than 5.0 imp./s), as well as for the antidromically identified coeruleospinal neurons. The response gain of locus coeruleus-complex neurons, including the coeruleospinal neurons, did not change when the peak amplitude of tilt was increased from 5 degrees to 20 degrees at the fixed frequency of 0.15 Hz. This indicates that the system was relatively linear with respect to the amplitude of displacement.(ABSTRACT TRUNCATED AT 400 WORDS)