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PubMed2002

Muscle spindle distribution, morphology, and density in longus colli and multifidus muscles of the cervical spine.

STUDY DESIGN: Tissue blocks comprising muscle and bone from C5 to C7 segments were harvested at autopsy from 16 individuals ranging in age from 4 to 77 years. The prevertebral longus colli and postvertebral multifidus muscle pairs from one side in each individual were randomly selected for this study of muscle spindles. OBJECTIVES: To determine muscle spindle distribution, morphology, and density for the longus colli and multifidus in caudal segments of the human cervical spine, and to assess whether changes are evident from infancy to old age. SUMMARY OF BACKGROUND DATA: Age-related changes to the osteoligamentous framework of the cervical spine have been well documented. Postural modification accompanies these structural alterations, but there have been limited attempts to document whether muscle sustains a comparable level of morphologic alteration. Previous studies have examined muscle spindles in the neck muscles of various animal models and in a variety of isolated human muscles. However, most of these studies incurred bias through sampling and methodologic assumptions. METHODS: The longus colli and multifidus were resected between C5 and C7, and between left and right pairs selected randomly for spindle analysis. These vertebral segments were selected deliberately because they form the apex of the cervical lordosis and the site at which the greatest age-related modification occurs. The tissue was processed in paraffin, sectioned, and then stained by Masson's trichrome. Spindle characteristics were examined using light microscopy and analyzed by unbiased stereologic methods. A one-sample paired t test was used to ascertain whether the differences in spindle density between the two muscles were statistically significant. RESULTS: The longus colli has a high density of muscle spindles, which appear clustered and concentrated anterolaterally, away from the vertebral body. The multifidus has a low density of muscle spindles, which are found predominantly as single units concentrated closely to the vertebral lamina. No change in spindle distribution, morphology, and density were observed with age. CONCLUSIONS: The current study examined spindle characteristics for an intrinsic neck muscle pair whose coactivation contributes to segmental stability of the cervical spine. The distribution and morphology of muscle spindles differ between the longus colli and the multifidus. In addition, these muscles have significant differences in terms of mean spindle density. Spindle characteristics represent one of many factors that govern proprioceptive regulation in skeletal muscle, and in neck muscles, the central connectivity of these receptors remains undefined. Therefore, although there are anatomic differences between the neck flexor and extensor, the functional implications of these differences are not clear. It is also of interest that spindle characteristics remain unchanged in these intrinsic muscles whose underlying segments are subject to age-related osteoligamentous changes.

Adolescent↗
PubMed2005

A randomized controlled trial on the efficacy of exercise for patients with chronic neck pain.

STUDY DESIGN: A randomized controlled trial with single-blind outcome assessments. OBJECTIVE: To evaluate the efficacy of a neck exercise program in patients with chronic neck pain. SUMMARY OF BACKGROUND DATA: The effect of exercise for patients with chronic neck pain has been investigated in a number of studies. The efficacy is, however, questionable. METHODS: A total of 145 patients were randomly allocated into an exercise (n = 67) and a nonexercise (control) group (n = 78). Patients in the control group were given infrared irradiation and neck care advice. In addition to infrared irradiation and advice, patients in the exercise group had undergone an exercise program with activation of the deep neck muscles and dynamic strengthening of the neck muscles for 6 weeks. Subjective pain and disability and isometric neck muscle strength were measured at baseline, 6 weeks, and 6 months. Analysis was by intention-to-treat. RESULTS: At week 6, the exercise group had a significantly better improvement in disability score (P = 0.03), subjective report of pain (P = 0.01), and in isometric neck muscle strength (P = 0.57-0.00) in most of the directions than the control group. However, significant differences between the two groups were found only in the subjective report of pain and patient satisfaction at the 6-month follow-up. CONCLUSIONS: At week 6, patients with chronic neck pain can benefit from the neck exercise program with significant improvement in disability, pain, and isometric neck muscle strength in different directions. However, the effect of exercise was less favorable at 6 months.

Adult↗
PubMedDate not supplied

Quantitative EMG in cervical dystonia.

Within the latest years botulinum toxin A (BT) applied locally in affected muscles has gained a superior position in the treatment of cervical dystonia. EMG is often used as a guidance for the injections, which has caused a need for better knowledge about the electromyographic changes in the muscles involved. In the present study we used the turns-amplitude analysis for the quantitative evaluation of the EMG of the sternocleidomastoid muscles and posterior neck muscles in 44 patients with cervical dystonia, not previously treated with BT. Twelve healthy subjects were examined for comparison. At rest 13 patients showed abnormal activity (defined as > 100 turns/s) in the sternocleidomastoid muscle contralateral to the involuntary head rotation (CS) and the ipsi- and contralateral posterior neck muscles (IPN and CPN): 12 patients had abnormal activity in CS and IPN, and seven patients had abnormal activity in all muscles, including the ipsilateral sternocleidomastoid muscle (IS). Other combinations were seen less often. The distribution of muscles with abnormal activity was not always obvious from the clinical examination. CPN and IS, i.e., apparently unaffected muscles, showed reduced EMG activity during attempted maximal voluntary contraction, indicating difficulties in activating all motor units.

Adult↗
PubMed1999

The dropped head sign in parkinsonism.

We describe seven patients who exhibited the dropped head sign in parkinsonism. These included six females and one male between the ages of 53 and 74. Three patients were clinically diagnosed as probable Parkinson's disease and four were diagnosed with probable multiple system atrophy. None had weakness in the posterior neck muscles or spasms in the anterior neck muscles. When the patients attempted to extend the head voluntarily or passively muscle contraction that was not seen in the dropped-head condition appeared. Surface electromyography of the neck indicated that the anterior neck muscles had rigidity. A gamma-block of the SCM muscles reduced the muscle activity when the head was elevated and improved the dropped-head condition slightly. These findings seem to indicate that the dropped head sign in parkinsonism could be associated with anterior neck muscle rigidity. Although the severity of the dropped head condition was affected by medication or by the clinical course in three patients, there was no clear relationship between the severity of the dropped head condition and the parkinsonism. We suspected that unbalanced muscle rigidity between the anterior and the posterior neck muscles could cause the dropped head sign.

Aged↗
PubMed1984

Action of neck accessory muscles on rib cage in dogs.

To investigate the action of the neck accessory muscles on the rib cage, we stimulated the sternocleidomastoid and the scalenus muscles separately in supine anesthetized dogs. Hooks screwed into the sternum and ribs were used to measure their axial displacements and the changes in anteroposterior (AP) and transverse (T) diameters of the rib cage. We found that the sternocleidomastoid and scalenus muscles, when they contract alone, cause a large axial displacement of the sternum and the ribs in a cephalad direction and expand the rib cage along both its AP and T diameters. Opening the abdomen increased the cephalad displacement of the ribs and the expansion of the lower rib cage, particularly along its T diameter, but reduced the increase in lung volume. These experiments indicate 1) that the action of the sternocleidomastoid and scalenus muscles on the rib cage is essentially the consequence of a rotation of the ribs' neck axes, resulting from the cephalad displacement of the ribs, and 2) that the fall in abdominal pressure, almost certainly by acting through the zone of apposition of the diaphragm to the rib cage, has a deflationary action on the lower rib cage, more markedly so on its lateral than its anterior wall. The experiments also suggest that the fall in abdominal pressure prevents the diaphragm from moving cephalad and aids the neck accessory muscles in inflating the lungs.

Abdomen↗
PubMed1987

Quantitative analysis of cervical musculature in rats: histochemical composition and motor pool organization. II. Deep dorsal muscles.

In this paper we characterize the architecture, histochemistry, spindle composition, and motor pool organization of rat dorsal neck muscles: splenius (SP), biventer cervicis (BC), and complexus (COM). We also consider whether individual rat neck muscles are innervated by more than one population of motor neurons as they are in turtles and cats and whether in these muscles motor neuron size scales with muscle fiber type. Dorsal neck muscles are divided by tendinous inscriptions into quasiserially arranged compartments. Each compartment is supplied by a separate peripheral nerve branch from C1-C5 dorsal rami; thus each dorsal neck muscle is innervated from multiple segments. Our histochemical data indicate that slow-twitch oxidative (SO) fibers are always the least numerous group, and fast fibers are split almost equally between fast oxidative glycolytic (FOG) and fast glycolytic (FG) types. There are significant cross-muscle differences in the relative frequency of each fiber type. Topographic analyses reveal a mosaic pattern of fiber types with no clear compartmentalization, and muscle spindle distribution is essentially homogeneous. Motor neurons supplying rat dorsal neck muscles are restricted to the ventral third of the ipsilateral ventral horn from lower medulla to C4. The SP motor pool is located dorsally in the ventral horn, and BC and COM motor pools form overlapping columns in the tip. There is little evidence that these muscles are supplied by more than one population of motor neurons, as reported in turtles and cats. To help assess these differing results, in two cats we infiltrated the C2 nerve to BC and COM; our results were similar to those previously reported in cats including the presence of contralateral motor neurons. Thus disparate results between rat and cat experiments may represent species differences in neck muscle innervation. In five experiments we made direct comparisons between the sizes of motor neurons that supply muscles with significantly different histochemical compositions. In each case there was a difference in mean soma size in the direction predicted by the muscles' histochemical profiles, thus suggesting that in these muscles motor neuron size may scale with muscle fiber type.

Adenosine Triphosphatases↗
PubMed2000

Integrated jaw and neck function in man. Studies of mandibular and head-neck movements during jaw opening-closing tasks.

This investigation was undertaken to test the hypothesis of a functional relationship between the human temporomandibular and craniocervical regions. Mandibular and head-neck movements were simultaneously recorded in healthy young adults using a wireless optoelectronic system for three dimensional movement recording. The subjects were seated in an upright position without head support and were instructed to perform maximal jaw opening-closing movements at fast and slow speed. As a basis, a study was undertaken to develop a method for recording and analysis of mandibular and head-neck movements during natural jaw function. A consistent finding was parallel and coordinated head-neck movements during both fast and slow jaw opening-closing movements. The head in general started to move simultaneously with or before the mandible at the initiation of jaw opening. Most often, the head attained maximum velocity after the mandible. A high degree of spatiotemporal consistency of mandibular and head-neck movement trajectories was found in successive recording sessions. The head movement amplitude and the temporal coordination between mandibular and head-neck movements were speed related but not the movement trajectory patterns. Examination of individuals suffering from temporomandibular disorders and whiplash associated disorders (WAD) showed, compared with healthy subjects, smaller amplitudes, a diverse pattern of temporal coordination but a similar high degree of spatiotemporal consistency for mandibular and head-neck movements. In conclusion, the results suggest the following: A functional linkage exists between the human temporomandibular and craniocervical regions. Head movements are an integral part of natural jaw opening-closing. "Functional jaw movements" comprise concomitant mandibular and head-neck movements which involve the temporomandibular, the atlanto-occipital and the cervical spine joints, caused by jointly activated jaw and neck muscles. Jaw and neck muscle actions are elicited and synchronised by neural commands in common for both the jaw and the neck motor systems. These commands are preprogrammed, particularly at fast speed. In the light of previous observations of concurrent jaw and head movements during foetal yawning, it is suggested that these motor programs are innate. Neural processes underlying integrated jaw and neck function are invariant both in short- and long-term perspectives. Integrated jaw and neck function seems to be crucial for maintaining optimal orientation of the gape in natural jaw function. Injury to the head-neck, leading to WAD may derange integrated jaw-neck motor control and compromise natural jaw function.

Adult↗
PubMed1996

Neck flexor muscle strength, efficiency, and relaxation times in normal subjects and subjects with unilateral neck pain and headache.

OBJECTIVE: To determine the test-retest reliability of a new method for measuring muscular strength, efficiency, and relaxation times of the neck flexor musculature of healthy adults, and to compare these neck flexor muscle properties in subjects who have unilateral neck pain and headache with those in controls. DESIGN: Subjects lay supine and isometrically flexed their necks against a force transducer attached to the back of a webbing and velcro helmet. Electromyograms (EMGs) were recorded from surface electrodes on the sternocleidomastoid (SCM) muscles. Two consecutive sessions of five contractions of varying levels of effort from minimal through moderate and maximal effort were analyzed. SETTING: Ambulatory referral center. PARTICIPANTS: Volunteer control subjects (n = 10, 3 men and 7 women) were recruited from hospital and university personnel. Volunteer neck pain subjects (n = 10, 3 men and 7 women) were recruited from a physiatric chronic pain practice and a hospital outpatient physical therapy practice. RESULTS: In the controls, the intraclass correlation coefficients (ICCs) for the first two maximum neck flexion contractions were; peak force ICC = .81; peak force/body weight ICC = .75; average force ICC = .75; force relaxation time ICC = .73; SCM EMG relaxation times: right ICC = .60 and left ICC = .67. Comparing sessions 1 and 2 the intraclass correlations for SCM efficiencies were right ICC = .58 and left ICC = .97. The peak force in controls (mean = 45.3 +/- 17.6N) was reduced by 50% in the neck pain subjects (mean = 22.4 +/- 13.1N) (p = .004). Similarly, peak force/body weight in the neck pain subjects (X = 0.3 +/- 0.2N/kg) was 46% of control (mean = 0.7 +/- 0.2N/kg) (p = .001), and average force in the neck pain subjects (X = 12.1 +/- 7.5N) was 43% of controls (mean = 28.5 +/- 11.0N) (p = .001). In two neck pain subjects. SCM, EMG and force relaxation times were abnormally long in both the affected and the unaffected SCM muscles, exceeding the control values by greater than 3 standard deviations. The difference between the right SCM efficiency of the control subjects (mean = 0.3 +/- 0.2N/ microV) and the affected SCM efficiency of the neck pain subjects (mean = 0.1 +/- 0.1 N/microV) approached the p < .05 criterion for significance (p = .055). CONCLUSION: The technique was found to be highly reliable for the measurement of neck flexor peak force, peak force/body weight, average force, and force relaxation time, and moderately reliable for the quantitation of SCM EMG relaxation times and SCM efficiency. All force values were significantly lower in the neck pain population compared with the controls. In the neck pain population, force and SCM EMG relaxation times, as well as efficiencies, suggested abnormalities. Neck pain subjects showed no significant differences in SCM EMG relaxation time or SCM efficiency between affected and unaffected SCM muscles.

Adult↗
PubMed2006

Dropped head in Parkinson's disease.

"A propensity to bend the trunk forward" and "the chin is now almost immovably bent down upon the sternum" were described by James Parkinson in patients with Parkinson's disease (PD). The term "dropped head" was first reported in "Gerlier disease" in Switzerland and 'kubisagari' in Japan and since then also reported in myositis, myopathy, myasthenia gravis, amyotrophic lateral sclerosis, neuropathy, and hypothyroidism. Disproportionate antecollis occurs in about half cases of multiple system atrophy (MSA) and is considered dystonic in nature. Dropped head is considered rare in PD, both in advanced and early stages of PD. However, it is known to progress subacutely over a period of several days. In my experience, dropped head is relatively common in PD. The mechanism of dropped head in PD is either dystonia of flexor neck muscles or weakness of extensor neck muscles. The response of dropped head to various anti-parkinsonian medications is rather inconsistent. Levodopa is reported to induce amelioration in some patients while dopamine agonists can cause deterioration. Muscle afferent block with lidocaine and ethanol is reported to be effective, while the effect of botulinum toxin injection into the affected muscles is limited. The effect of stereotaxic neurosurgery on dropped head is controversial. Early diagnosis and prompt treatment is necessary to prevent muscle damage associated with longterm overstretch of extensor neck muscles.

Female↗
PubMed1987

Torticollis following radiation therapy.

A patient with adenocarcinoma in the apical portion of the lung producing a Pancoast's syndrome developed torticollis a few months after receiving a course of radiation therapy (5,040 rad) to his upper chest and neck. We describe this case, in which local radiation fibrosis of the neck muscles and perhaps segmental demyelination of the 11th cranial nerve resulted in peripheral nervous system lesion causing torticollis.

Adenocarcinoma↗
PubMed1991

Distant effects of locally injected botulinum toxin: a double-blind study of single fiber EMG changes.

We used single fiber electromyography (SFEMG) to study 42 patients who had enrolled in a double-blind, placebo-controlled trial undertaken to assess the efficacy of botulinum toxin (BTX) injection of neck muscles to treat torticollis. SFEMG in a limb muscle was performed before treatment, 2, and 12 weeks after injection of placebo or BTX. Before treatment, the mean jitter was 26.8 microsec in patients who were to receive BTX, and 25.7 microsec in the placebo group. Two weeks after injection, mean jitter in the group receiving BTX was 43.6 microsec. In the placebo group, it was 26.5 microsec (P = less than .05). Twelve weeks after injection, mean jitter in the BTX group was 35.5; for the placebo group it was 24.5. Fiber density did not change in any patient during the study. There were no remote clinical effects of BTX. Injection of BTX into muscles affected with focal dystonia is a promising and safe treatment, but there are subclinical effects on uninjected muscles.

Adult↗
PubMed1980

Stimulation of the superior colliculus in the alert cat. I. Eye movements and neck EMG activity evoked when the head is restrained.

Electrical stimulation of the cat superior colliculus (SC), in conjunction with the accurate measurement of elicited eye movements and histologically verified electrode positions, has revealed a striking antero-posterior variation in collicular organization. Three zones could be defined in the SC on the basis of eye movement patterns and associated neck muscle EMG activity evoked from the deeper layers. The Anterior zone was coextensive with the central 25 degrees of the visual retinotopically coded map contained in the superficial layers. Saccades evoked from this zone were also retinotopically coded, and the latency of EMG activity depended on the position of the eye in the orbit. A similar observation applies to the entire monkey SC. The Intermediate zone was coextensive with the 25 degrees--70 degrees of visual projections. Saccades evoked from this region were "goal-directed" and were associated with invariant, short latency EMG responses. The Posterior zone was found in the extreme caudo-lateral portion of the SC. Eye movements evoked from this zone were centering saccades associated with constant latency EMG activity. The present results in conjunction with previously demonstrated antero-posterior variations in projections to the SC, suggest that the motor strategies controlling gaze shifts toward visual targets vary depending on the location of the target in the visual field.

Animals↗
PubMed1982

Dynamic properties of vestibular reflexes in the decerebrate cat.

Vestibulocollic (VCR) and vestibulo-ocular (VOR) reflexes were studied during angular rotation in the horizontal plane in precollicular decerebrate cats. Angular position was modulated by sinusoids or sums of sinusoids with frequencies ranging from 0.05 to 5 Hz. Reflex motor output was measured by recording electromyographic (EMG) activity of the lateral rectus and dorsal neck muscles and discharge of abducens motoneurons. Measured with respect to input angular acceleration VCR motor output displayed a second order lag at low frequencies, bringing mean EMG phase (-136 degrees) and gain slope (-35 dB/decade) close to those of an angular position signal at 0.2 Hz. At higher frequencies the lag was counteracted by a second order lead bringing mean phase (-52 degrees) and gain slope (-5.6 dB/decade) back close to those of an angular acceleration signal at 3 Hz. By contrast, mean phase (-113 degrees to -105 degrees) and gain slope (-21 to -28 dB/decade) of the VOR motor output remained close to those of an angular velocity signal across the entire frequency range. The data suggest that neural pathways producing the VCR receive selective input from "irregular type" horizontal semicircular canal afferents which provide one lag and one lead in the overall transfer function while the other lag and lead are produced by central pathways. Transection of the medial longitudinal fasciculus (MLF), which eliminates all of the most direct (three neuron) arcs of the horizontal VCR, did not cause any detectable change in the horizontal VCR at either low or high frequencies. Reductions in overall gain occurred in some cases but these could be attributed to damage to axons outside the MLF. Less direct pathways, probably including vestibuloreticulospinal pathways, are thus able to produce both the low-frequency, phase-lagging and high-frequency, phase-leading components of the horizontal VCR.

Afferent Pathways↗
PubMed1981

Simulation of head movement trajectories: model and fit to main sequence.

A sixth order nonlinear model for horizontal head rotations in humans is presented and investigated using experimental results on head movement trajectories and neck muscle EMG. The controller signals, structured in accordance with time optimal control theory, are parameterized, and controller signal parameter variations show a dominating influence on different aspects of the head movement trajectory. The model fits the common head acceleration types over a wide range of amplitudes, and also less common (dynamic overshoot) trajectories.

Electromyography↗
PubMed2002

Effects of synthetic progestagens on the mRNA expression of androgen receptor, progesterone receptor, oestrogen receptor alpha and beta, insulin-like growth factor-1 (IGF-1) and IGF-1 receptor in heifer tissues.

Synthetic progestagens like melengestrol acetate (MGA) are widely used for oestrus synchronization and for growth promotion in cattle production. The metabolic effects exceed its primary potency as a progestagen. It is speculated that MGA stimulates follicle development and thereby endogenous oestrogen production, but inhibits ovulation. To investigate the dose-dependent effects on mRNA expression levels, six heifers were fed for 8 weeks with different levels of MGA (0.5, 1.5, 5 mg) daily and two heifers served as controls. The expression of steroid receptor mRNA [androgen receptor (AR), progesterone receptor (PR), oestrogen receptor (ER) ERalpha and ERbeta], insulin-like growth factor-1 (IGF-1) and its receptor were quantified in liver, neck (m. splenius) and shoulder muscularity (m. deltoideus). Plasma concentrations of IGF-1 were quantified by radioimmunoassay. In treated animals the MGA plasma levels were elevated over the complete treatment period, corresponding to the MGA treatment concentrations. IGF-1 concentrations of control animals were at constant levels. Plasma levels for oestradiol (E2) and IGF-1 were increased in the low MGA treatment group. Overdosed MGA decreased progesterone (P4) and E2 levels. To quantify the IGF-1 and all receptor mRNA transcripts, sensitive and reliable real-time reverse transcription-polymerase chain reaction (RT-PCR) quantification methods were developed and validated in the LightCycler. A dose-dependent relationship between increasing MGA concentration and mRNA expression was observed in liver for AR and IGF-1 receptor, and in neck muscularity for IGF-1. ERalpha in liver and neck muscle showed a trend of increasing expression.

Animals↗
PubMed1979

Analysis of vestibulocollic reflexes by sinusoidal polarization of vestibular afferent fibers.

1. Canal vestibular-neck (vestibulocollic) reflexes have been studied in decerebrate cats by applying modulated polarizing current to individual ampullary nerves, usually the horizontal nerve. 2. Computer-generated stimuli sometimes consisted of sine or square waves at frequencies of 0.01--5 Hz. More often we used a compound wave form of nine superimposed sinusoids within an available frequency range of 0.009--6.11 Hz. The frequencies used were odd, relatively prime multiples of a base frequency selected to minimize distortion or interaction of responses. The response to each of the nine stimulating frequencies could be obtained in subsequent data analysis. 3. Responses to these stimuli were studied by recording the EMG of contralateral neck muscles and extracellular activity of second-order neurons. These neurons were identified by their monosynaptic responses to single-shock stimulation of ampullary nerves. 4. EMG was modulated sinusoidally. Below 0.1 Hz the response was variable, most likely due to differences in the preparations. In the frequency range of 0.1--0.4 Hz there was usually a phase lag, which decreased with incresing frequency and often reversed to a lead at 3 and 6 Hz. Gain decreased from the lowest frequencies, occasionally with an upturn at 3 or 6 Hz. 5. Second-order neuron firing was approximately in phase with the stimulus at the lowest frequencies. Phase advanced with increasing frequency to a lead of 30--50 degrees at 6 Hz. Gain generally increased with frequency. 6. By recording simultaneously from muscle and from second-order neurons, or by comparing the mean behavior of the two, it was possible to determine the central phase lag and gain of the vestibulocollic reflex. The lag was variable at low frequencies, had an average of 50 degrees at 0.18 Hz, and decreased to 20 degrees at 6 Hz. These results are comparable to those obtained by others using natural stimulation at frequencies of 1.0 Hz and below, and provide new information about the behavior of the central processer at higher frequencies. 7. The medial vestibulospinal tract (MVST), which contains the axons of crossed second-order vestibular neurons, was transected in six experiments. In agreement with previous workers there was no effect on phase at frequencies up to 0.4 Hz. There was also no selective effect of phase or gain at the higher frequencies. This shows that the disynaptic pathways in the MVST do not play any role that cannot be taken over by parallel pathways.

Animals↗
PubMedDate not supplied

[Relation between the defensive behavior of altricial nestlings and the parameters of an alarm signal. Neuroethologic approach].

The acoustic organization of the defensive behaviour was studied in Pied Flycatcher nestlings. Electrodes were chronically implanted into the field L and the neck muscles for auditory EPs and EMG recordings. A well developed defensive reaction which under natural conditions is elicited by species-specific alarm call, could be artificially provoked by monotonal 4.5-6 kHz bursts with repetition frequency of 4-0,8/s. The tone frequency was shown to be the critical acoustic parameter permitting the altricial nestlings to identify alarm vocalization and differentiate it from alimentary signals. The role of the burst repetition frequency is restricted to maintaining the tonic defensive activation in the course of the alarm signal presentation. Certain correlation was found between the time of regeneration of excitability in auditory structures and the burst repetition frequency in the species specific alarm signal.

Aggression↗