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PubMed1996

Differential effects of intra-accumbens sulpiride on cocaine-induced locomotion and conditioned place preference.

The effects of intra-accumbens sulpiride on conditioned place preference and locomotion produced by i.v. cocaine were investigated. Every other day during conditioning, rats received infusions of sulpiride (0-0.4 microgram) into the nucleus accumbens (NAc) or caudate-putamen. Fifteen min later, they were placed into a distinct compartment and injected with saline or cocaine (4.2 mg/kg, i.v.). On the alternate days, rats received sham intracranial injections and were placed into a different compartment. Locomotion and stereotypies were assessed after the first and last injection, and conditioned place preference was assessed 24 hr after the last conditioning day. After behavioral testing, receptors occupied by sulpiride were quantified by injecting rats intracranially with their respective dose of sulpiride, followed by a systemic injection of the irreversible antagonist N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). Receptors protected from EEDQ induced inactivation by sulpiride were revealed on autoradiograms of sections labeled with 3H-sulpiride. Sulpiride did not alter cocaine-conditioned place preference or cocaine-induced stereotypies. However, the two lowest doses of intra-accumbens sulpiride attenuated cocaine-induced locomotion and occupied > 42% of the sulpiride binding sites in the NAc, and the highest dose completely reversed cocaine-induced locomotion and occupied > 96% of the sulpiride binding sites in the NAc. Intracaudate sulpiride also attenuated cocaine-induced locomotion without occupying a significant number of binding sites in the NAc. These findings suggest that D2-like receptors in the NAc and anterior medial caudate-putamen are involved in cocaine-induced locomotion, but not cocaine-conditioned place preference.

Animals↗
PubMed1996

pp60(c-src) is required for cell locomotion regulated by the hyaluronanreceptor RHAMM.

The tyrosine kinase pp60(c-src) has been implicated as a regulator of focal adhesion formation and cell spreading. Here we show that c-src also regulates cell motility and is a key component in the signaling pathway triggered by the motogenic hyaluronan receptor RHAMM, which has been shown to regulate focal adhesion turnover and to regulate ras. Fibroblasts derived from mice lacking src, (src (-/-)), have a random locomotion rate that is significantly slower than the corresponding wild-type fibroblasts. Cell locomotion in these mutant cells is restored by the expression of c-src containing a functional kinase domain, but not by the expression of a kinase-deficient src or by a truncated src containing only functional SH2 and SH3 domains. RHAMM is also required for the restoration of src (-/-) cell locomotion. Thus, the motility of cells expressing c-src is reduced to src (-/-) levels by anti-RHAMM blocking antibodies while the cell locomotion of src (-/-) fibroblasts remains unaffected by anti-RHAMM antibodies. We predict that src acts downstream of RHAMM in the regulation of motility, since the expression of a dominant negative src significantly inhibits RHAMM-dependent ras and serum regulated cell locomotion, the expression of v-src enhances cell motility in a RHAMM independent fashion, and there is a physical and functional assocation between src and RHAMM in ras-transformed cells. However, we suggest that RHAMM regulates focal adhesion turnover via additional src-independent mechanisms. Thus, v-src is unable to turnover focal adhesions in the absence of RHAMM. These results directly demonstrate for the first time a role for src in the regulation of cell locomotion and confirm a key and complex role for src in the regulation of the actin cycle.

Animals↗
PubMed2003

Dynamic plantar pressure distribution during terrestrial locomotion of bonobos (Pan paniscus).

We collected high-resolution plantar pressure distributions of seven bonobos during terrestrial bipedal and quadrupedal locomotion (N = 146). Functional foot length, degree of hallux abduction, and total contact time were determined, and plots, showing pressure as a function of time for six different foot regions, were generated. We also studied five adult humans for comparison (N = 13). Both locomotion types of the bonobo show a large variation in plantar pressure distributions, which could be due to the interference of instantaneous behavior with locomotion and differences in walking speed and body dimensions. The heel and the lateral midfoot typically touch down simultaneously at initial ground contact in bipedal and quadrupedal walking of bonobos, in contrast with the typical heel-strike of human bipedalism. The center of pressure follows a curved course during quadrupedalism, as a consequence of the medial weight transfer during mid-stance. Bipedal locomotion of bonobos is characterized by a more plantar positioning of the feet and by a shorter contact time than during quadrupedal walking, according to a smaller stride and step length at a higher frequency. We observed a varus position of the foot with an abducted hallux, which likely possesses an important sustaining and stabilizing function during terrestrial locomotion.

Animals↗
PubMed2005

Neuromusculoskeletal computer modeling and simulation of upright, straight-legged, bipedal locomotion of Australopithecus afarensis (A.L. 288-1).

The skeleton of Australopithecus afarensis (A.L. 288-1, better known as "Lucy") is by far the most complete record of locomotor morphology of early hominids currently available. Even though researchers agree that the postcranial skeleton of Lucy shows morphological features indicative of bipedality, only a few studies have investigated Lucy's bipedal locomotion itself. Lucy's energy expenditure during locomotion has been the topic of much speculation, but has not been investigated, except for several estimates derived from experimental data collected on other animals. To gain further insights into how Lucy may have walked, we generated a full three-dimensional (3D) reconstruction and forward-dynamic simulation of upright bipedal locomotion of this ancient human ancestor. Laser-scanned 3D bone geometries were combined with state-of-the-art neuromusculoskeletal modeling and simulation techniques from computational biomechanics. A detailed full 3D neuromusculoskeletal model was developed that encompassed all major bones, joints (10), and muscles (52) of the lower extremity. A model of muscle force and heat production was used to actuate the musculoskeletal system, and to estimate total energy expenditure during locomotion. Neural activation profiles for each of the 52 muscles that produced a single step of locomotion, while at the same time minimizing the energy consumed per meter traveled, were searched through numerical optimization. The numerical optimization resulted in smooth locomotor kinematics, and the predicted energy expenditure was appropriate for upright bipedal walking in an individual of Lucy's body size.

Animals↗
PubMed1988

Effect of posture and locomotion on energy expenditure.

Energy expenditure for human adults and infants and for dogs was measured in resting (supine or lateral) posture, in bipedal posture and locomotion, and in quadrupedal posture and locomotion. Variations in respiratory and heart rate and in body temperature were utilized in this comparative study. Oxygen consumption was also measured in human adults. In human adults, bipedal posture and locomotion were shown to be much less energy-consuming than corresponding quadrupedal posture and locomotion. The opposite was observed in adult dogs, where bipedalism was shown to be much more energy-consuming than quadrupedalism. In addition, this study demonstrated, for human adults in their natural erect posture, an energy expenditure barely higher than in supine or lateral resting posture, while the dogs in their natural quadrupedal stance, the energy expenditure is much higher than in their resting posture. With respect to energy, therefore, humans are more adapted to bipedalism than dogs to quadrupedalism. Human children, at the transitional stage between quadrupedalism and bipedalism, have high and almost equal requirements for all postures and locomotions. This demonstrates, in term of energy, their incomplete adaptation to erect behavior.

Adolescent↗
PubMed1996

Corticotropin-releasing factor enhances locomotion and medullary neuronal firing in an amphibian.

Corticotropin-releasing factor (CRF) administration has been shown to act centrally to enhance locomotion in rats and amphibians. In the present study we used an amphibian, the roughskin newt (Taricha granulosa), to characterize changes in medullary neuronal activity associated with CRF-induced walking and swimming in animals chronically implanted with fine-wire microelectrodes. Neuronal activity was recorded from the raphe and adjacent reticular region of the rostral medulla. Under baseline conditions most of the recorded neurons showed low to moderate amounts of neuronal activity during periods of immobility and pronounced increases in firing that were time-locked with episodes of walking. These neurons sometimes showed further increases in discharge during swimming. Injections of CRF but not saline into the lateral ventricle produced a rapidly appearing increase in walking and pronounced changes (mostly increases) in firing rates of the medullary neurons. CRF produced diverse changes in patterns of firing in different neurons, but for these neurons as a group, the effects of CRF showed a close temporal association with the onset and expression of the peptide's effect on locomotion. In neurons that were active exclusively during movement prior to CRF treatment, the post-CRF increase in firing was evident during episodes of walking; in other neurons that also were spontaneously active during immobility prior to CRF infusion, post-CRF activity changes were evident during immobility as well as during episodes of locomotion. Thus, a principal effect of CRF was to potentiate the level of neuronal firing in a population of medullary neurons with locomotor-related properties. Due to the route of administration CRF may have acted on multiple central nervous system sites to enhance locomotion, but the results are consistent with neurophysiological effects involving medullary locomotion-regulating neurons.

Animals↗
PubMed1992

Low-threshold, short-latency cutaneous reflexes during fictive locomotion in the "semi-chronic" spinal cat.

Low-threshold, short-latency cutaneous reflexes evoked in ipsilateral hindlimb motor nerves were examined during fictive locomotion. Locomotion in 11 anaemically decerebrated spinal animals (1-3 weeks after transection at T13-L1) was induced by administration of clonidine, L-dopa and nialamide; by administration of the latter two drugs only; or by exteroceptive stimulation in the absence of any drugs. The caudal and lateral cutaneous sural, caudal cutaneous femoral, saphenous and superficial peroneal nerves were stimulated at low threshold (1.5-3 T). Pooled results from all combinations of cutaneous nerves stimulated and muscle nerves recorded show that the initial response was excitatory in 40 of 50 triceps surae and 17 of 20 semitendinosus (St) electroneurograms (ENGs). These excitatory responses occurred at latencies that ranged from 5 to 15 ms and tended to be maximal during the motor nerve's active period in the step cycle (i.e. they were modulated in a phase-dependent manner). Only three inhibitory responses (9-12 ms earliest latency) were encountered in total: in two St ENGs of one animal and in one lateral gastrocnemius-soleus ENG of a different animal. In two animals a "second" excitatory response (15-25 ms latency) was sometimes recorded in triceps surae and St nerves and, interestingly, could be modulated out of phase with the early response. Weak short-latency excitatory reflexes were also found in contralateral St ENGs when examined. Finally, among medial gastrocnemius, lateral gastrocnemius and soleus nerves, excitatory responses due to stimulation of any particular cutaneous nerve tended to be modulated similarly but were of consistently different amplitude among the three. This finding, together with the general observation that excitatory reflexes produced by stimulation of a particular cutaneous nerve were modulated similarly in extensors (or flexors) of different animals, suggests that spinal circuits generating locomotion may indeed exert a stereotypic control over interneurons in specific cutaneous reflex pathways to motoneurons. The results are primarily discussed in terms of the existing evidence for short-latency excitatory cutaneous reflexes in extensors in a variety of locomotive and non-locomotive preparations.

Animals↗
PubMed1988

Excitability changes of ankle extensor group Ia and Ib fibers during fictive locomotion in the cat.

The present study examines the modulation of gastrocnemius-soleus (GS) monosynaptic reflexes as well as the intraspinal threshold changes of GS group I primary afferent terminals ending in the intermediate and motor nuclei during fictive locomotion in high decerebrate cats. The amplitude of the monosynaptic reflexes (MSR's) evoked in the medial gastrocnemius by stimulation of the lateral gastrocnemius nerve was increased during the extensor (E) phase, decreased during the flexion (F) phase of the step cycle and remained transiently increased after spontaneous episodes of fictive stepping. The intraspinal threshold of populations and of single group Ia GS afferent fibers ending in the motor pool, as well as of single Ia and Ib fibers ending in the intermediate nucleus, showed a sustained reduction during the episodes of fictive locomotion with superimposed cyclic changes in phase with the step cycle. During fictive walking and trotting the reduction of the intraspinal threshold of both Ia and Ib fiber terminals was maximal during the middle or late portion of the F-phase. During fictive gallop elicited by stimulation of the superficial peroneus nerve, the decrease in the intraspinal threshold of the Ia afferent fibers occurred however in phase with the activity of the GS motoneurons. During episodes of fictive locomotion slow, sustained negative DC potential shifts lasting tents of seconds, reflecting an increase in the extracellular potassium concentration were recorded at the base of the dorsal horn and in the intermediate nucleus. The present findings support the existence of tonic and phasic depolarization of the intraspinal terminals of GS group Ia and Ib primary afferents during spontaneous fictive locomotion. It is suggested that accumulation of potassium ions in the extracellular space contributes mainly to the sustained depolarization of group I fibers. The phasic depolarization would be mostly due to the activation of specific sets of interneurons and may, in the case of Ia fibers, contribute to the cyclic modulation of the MRS elicited during fictive locomotion.

Afferent Pathways↗
PubMed2003

Motor effects of GABA(A) antagonism in globus pallidus: studies of locomotion and tremulous jaw movements in rats.

RATIONALE: Although most rodent studies related to parkinsonian symptoms have focused on locomotion, tremulous jaw movements also have been used as a rodent model of tremor for investigating the circuitry of the basal ganglia. OBJECTIVE: There are multiple pathways involved in the generation of parkinsonian symptoms. The globus pallidus is a basal ganglia relay nucleus, and the present study was conducted to investigate the effect of pallidal GABA antagonism on locomotion and tremulous jaw movements. METHODS: Suppression of locomotion and induction of tremulous jaw movements were produced by repeated (i.e., 14 day) systemic administration of the dopamine D2 antagonist haloperidol, and by acute systemic injection of the muscarinic agonist pilocarpine. The GABA(A) antagonist bicuculline was injected into the globus pallidus, and its effects on locomotion in haloperidol- and pilocarpine-treated rats were assessed in the first group of experiments. In the second group of experiments, the effects of intrapallidal infusions of bicuculline on haloperidol- and pilocarpine-induced jaw movements were observed. RESULTS: Pallidal GABA antagonism stimulated locomotion when no other treatment was present, and also when animals were coadministered haloperidol or pilocarpine. Bicuculline suppressed haloperidol-induced jaw movements in a dose-related manner, and had no effect on pilocarpine-induced jaw movements. CONCLUSIONS: These results support the notion that there are distinct pathways conveying basal ganglia outflow and demonstrate that the striatopallidal pathway is involved in the generation of the haloperidol-induced tremulous jaw movements. These findings are consistent with some features of current models of basal ganglia function and may lead to an understanding of the specific mechanisms that generate parkinsonian symptoms.

Animals↗
PubMed2001

Time-dependent actions of D2 family agonist quinpirole on spontaneous behavior in the rat: dissociation between sniffing and locomotion.

RATIONALE: Dopamine agonists elevate locomotion, sniffing, grooming, and a number of other behaviors. However, the D2 family (D2/D3/D4) agonist quinpirole, across a wide dose range, produces a period of locomotor inhibition that precedes the drug's locomotor excitatory effects. OBJECTIVES: The present study asked whether the suppressive actions of quinpirole also extend to other aspects of spontaneous behavior, such as sniffing, rearing and grooming, or whether this suppression of locomotion occurs while the frequency of other behaviors is increased or unaffected. METHODS: Locomotion, sniffing, rearing and grooming were observed over a 150-min test session in rats treated with 0, 0.1, 0.5, 1.0, or 10.0 mg/kg quinpirole. RESULTS: At 0.1 mg/kg, quinpirole suppressed locomotion. Higher doses (0.5-10.0 mg/kg) produced locomotor suppression followed by locomotor excitation. During the period of locomotor suppression, quinpirole also reduced the frequency of rearing and grooming. However, animals under high doses (1 and 10 mg/kg) of quinpirole showed elevated sniffing during the period of locomotor, rear and groom suppression. CONCLUSIONS: These results demonstrate that the well-documented locomotor suppression that precedes quinpirole's excitatory locomotor actions occurs in the midst of active sniffing. These results suggest that the suppressive effects of quinpirole on locomotion do not reflect a state of general behavioral suppression.

Animals↗
PubMed2004

Obstacle avoidance during locomotion using haptic information in normally sighted humans.

The goal of the study was to examine the accuracy and precision of control of adaptive locomotion using haptic information in normally sighted humans before and after practice. Obstacle avoidance paradigm was used to study adaptive locomotion; individuals were required to approach and step over different sizes of obstacles placed in the travel path under three sensory conditions: full vision (FV); restricted lower visual field (RLVF) using blinders on custom glass frames; and no vision (NV) using haptic information only. In the NV condition, individuals were a given an appropriate-sized cane to guide their locomotion. Footfall patterns were recorded using the GAITRite system, and lead and trail limb trajectories were monitored using the OPTOTRAK system, which tracked infrared diodes placed on the toes and the cane. Approach step lengths were reduced for the haptic condition: this slowed the forward progression and allowed greater time for haptic exploration, which ranged from 2.5 to 4 s and consisted of horizontal cane movements (to detect the width and relative location of the obstacle) and vertical cane movements (to detect the height of the obstacle). Based on feed-forward and on-line sensory (under both vision and haptic conditions) information about location of the obstacle relative to the individual, variability of foot placement reduced as the individual came closer to the obstacle, as has been shown in the literature. The only difference was that the reduction in variability of foot placement under haptic condition occurred in the last step compared with earlier under vision. Considering that the obstacle is detected only when the cane comes in contact, as opposed to vision condition when it is visible earlier, this difference is understandable. Variability and magnitude of lead and trail limb elevation for the haptic condition was higher than the RLVF and FV conditions. In contrast, only the magnitude of lead and trail limb elevation was higher in the RLVF condition when compared with the FV condition. This suggests that it is the inability of the haptic sense to provide accurate information about obstacle characteristics compared with the visual system, and not simple caution that lead to higher limb elevation. In the haptic and RLVF condition when vision was unavailable for on-line monitoring of lead limb elevation, kinesthetic information from lead limb elevation was used to fine-tune trail limb elevation. Both the control of approach phase and limb elevation findings held up even after sufficient practice to learn haptic guidance of adaptive locomotion in the second experiment. These results provide a clear picture of the efficacy of the haptic sensory system to guide locomotion in a cluttered environment.

Adaptation, Psychological↗
PubMed1975

Coordination of movements of the kindlimbs and forelimbs in different forms of locomotion in normal and decerebrate cats.

The coupling of movements of the hindlimbs and forelimbs has been analysed in intact cats stepping overground and on a treadmill and during swimming, and in decerebrate cats stepping on a treadmill, immersed in water('swimming') and stepping suspended in the air. In the different preparations, and under different types of locomotion, two basic patterns of coupling have been observed. Both concern the hindlimb and forelimb of the same side of the body. The first pattern is found in the pacing gait where flexion of the forelimb precedes extension of the hindlimb, measured at the elbow and knee, respectively. The second pattern is typically found in the trot where flexion of the forelimb follows extension of the hindlimb. In decerebrate cats both patterns of coupling remain after bilateral deafferentation of the hindlimbs. In the alternate form of locomotion these patterns of coupling occurs symmetrically on both sides. In the rotatory and transverse gallop (examples of the in-phase form of locomotion) the coupling is asymmetrical: on one side it is comparable to pacing (forelimb flexion precedes hindlimb extension), and on the other side to trotting (forelimb flexion follows extension). These basic patterns of interlimb coordination simplify considerably the problem of neural control of the limbs in locomotion. Obersations of EMGs during the alternative forms of locomotion show that in the pacing type of coupling the extensor EMGs of forelimb and hindlimb overlap, with the hindlimb leading the forelimb by about 10% of a step cycle, while in the trotting type of coupling the forelimb flexor EMGs overlap the hindlimb extensor EMGs, the forelimb flexors leading the hindlimb extensors by about 10% of a step cycle. During acceleration the transition between the two forms of EMG occurs within one or two step cycles, and at some intermediate velocities the EMG coupling springs back and forth between the two different forms. These results further support the hypotesis of two basic forms of interlimb coupling in which long propriospinal pathways probably play a role.

Animals↗
PubMed1983

Modification of the initiation of locomotion in Hermissenda: behavioral analysis.

We have examined the effect of a conditioning procedure on various components of visually guided locomotion in Hermissenda. Temporally specific stimulation of the visual system and gravity detecting system (statocysts) with light and rotation produced long-term changes in locomotor behavior. We found that the latency to initiate locomotion in the presence of light was significantly increased for the conditioned group as compared to baseline pre-test latencies and groups that received random presentations of the conditioning stimuli. The variability in the time taken by animals to enter a central illuminated area as reported in earlier studies can be accounted for by the increase in the latency to initiate locomotion. The modifications of visually influenced locomotion exhibits stimulus (CS) specificity since locomotor behavior is not changed following conditioning in the absence of light. In addition, conditioned animals remained in the brightest part of the light gradient significantly less than pre-test measurements. Since this response (initiation of locomotion) can be studied in a semi-intact preparation, it should be possible to investigate how this example of learning generates changes in behavior.

Animals↗
PubMed1985

The role of putative excitatory amino acid neurotransmitters in the initiation of locomotion in the lamprey spinal cord. II. The effects of amino acid uptake inhibitors.

Fictive locomotion can be evoked in an in vitro preparation of the lamprey spinal cord by an activation of N-methyl-D-aspartate (NMDA) or kainate receptors. To obtain further knowledge of the putative transmitters underlying this activation the effects of L-glutamate and L-aspartate were examined. These endogenous amino acids exerted a distinctly different effect as compared to the synthetic amino acids (N-methyl-D,L-aspartate and kainate) previously tested. In a wide dose range L-glutamate and L-aspartate elicited fictive locomotion only when the bathing solution was rapidly circulated over the spinal cord surface. In the absence of fluid circulation the activity rapidly ceased. To test if this effect was due to an uptake of amino acids, two amino acid uptake inhibitors were administered. After exposure to p-chloromercuriphenylsulphonate (pCMS) or dihydrokainate (DHK), L-glutamate and L-aspartate elicited continuous fictive locomotion independently of whether the bathing fluid was circulated or not. This treatment also markedly lowered the threshold doses of L-glutamate and L-aspartate, while the effects of NMA and kainate were barely affected. Fictive locomotion induced by sensory stimulation of the tailfin was also prolonged by dihydrokainate. These findings suggest that a highly effective amino acid uptake system is present in the lamprey spinal cord and furthermore that it takes part in the inactivation of synaptically released acidic amino acid neurotransmitters, which are of importance for the initiation of locomotion.

Amino Acids↗
PubMed1987

Glutamate and picrotoxin injections into the preoptic basal forebrain initiate locomotion in the anesthetized rat.

This study determined the locomotor effects of glutamate and picrotoxin injections and electrical stimulation in the preoptic basal forebrain. Male rats, anesthetized with Nembutal, were held in a stereotaxic apparatus such that stepping rotated a wheel. Cathodal stimulation (0.5-ms pulses, 50-Hz frequency, 10-s train, less than 100 microA) was applied through a 30-gauge stainless-steel, insulated cannula to find locomotor sites. Glutamate (20 mM or 2 M) or picrotoxin (100 or 200 ng) were injected in volumes of 0.2 or 0.1 microliter of saline at a rate of 1 microliter/5 min. Electrical stimulation elicited locomotion (principally hindlimbs) in 32 sites which included the lateral and medial preoptic areas and the bed nucleus of the stria terminalis (BST). Stimulation in 23 sites, most in the BST and septal area, failed to produce locomotion. Stepping was elicited by glutamate and electrical stimulation in 15 sites. Glutamate was ineffective at 21 sites, at 6 of these sites electrical stimulation was effective. Longer bouts of locomotion were produced by 20 nM glutamate. Picrotoxin produced more intense and prolonged locomotion than glutamate. It was effective in 15 sites, at 12 of which electrical stimulation was also effective. At some ventral sites, picrotoxin-elicited stepping was continuous, at others it appeared in bursts of 5-20 s duration. At dorsal sites, the locomotor bursts were punctuated by episodes of pelvic flexion. Picrotoxin was ineffective at 12 sites, 7 of which were effective with electrical stimulation. These results indicate that activity of neurons in the preoptic basal forebrain can initiate locomotion.

Anesthesia↗
PubMed1988

Brainstem command systems for locomotion in the lamprey: localization of descending pathways in the spinal cord.

The lamprey brainstem contains a 'command system' which descends into the spinal cord to activate motor networks and initiate locomotion. In the present study, partial lesions were made in the rostral spinal cord in order to spare various tracts and determine which tracts carry the descending command signal to the spinal cord. Sparing the medial areas of the rostral spinal cord usually blocked both sensory-evoked and spontaneous locomotion, while sparing the lateral regions of the rostral spinal cord did not abolish voluntary locomotor activity. Either the ventrolateral or dorsolateral spinal tracts could support the initiation of locomotion. Brainstem structures rostral to the mesencephalon were not necessary for the initiation of locomotor behavior. The data indicate that the lateral spinal tracts contain a significant part of the descending command pathway for locomotion. In contrast, the medial spinal tracts were neither necessary nor usually sufficient to support locomotor behavior, suggesting that the larger reticulospinal Muller cells, which project in these tracts, do not contribute significantly to the initiation of locomotion.

Animals↗
PubMed1995

Theta-like rhythm in depth EEG activity of hypothalamic areas during spontaneous or electrically induced locomotion in the rat.

Spontaneous locomotion performed by an awake rat is accompanied by synchronized activity (a theta rhythm) of the hippocampus (Hipp). Locomotion can also be induced by electrical stimulation of various sites within the brain. The effectiveness of electrical stimulation of the subthalamic locomotor region (SLR) and posterior hypothalamus (PH) in inducing locomotor movements has previously shown that they are parts of the system controlling locomotion. Thus, it was of interest to determine whether their electrical activity was correlated with the motor behavior, as it is in the Hipp. The experiments done here on chronic animals with electrodes implanted into the Hipp and hypothalamus showed that rhythmic depth EEG activity (theta-like) similar to that found in the Hipp is present in motor-positive hypothalamic areas during spontaneous locomotion. In addition, our results showed that movements induced by stimulation of various hypothalamic sites are also accompanied by theta-like activity in the Hipp and some hypothalamic areas. Thus, our results support the idea that the well-known and anatomically established connections between the Hipp and hypothalamus are active during locomotion. These connections may constitute a part of the system involved in the control of the motor behavior.

Animals↗
PubMed1991

Afferent control of central pattern generators: experimental analysis of locomotion in the decerebrate cat.

Changes in the motor activity of the spinal locomotor generator evoked by tonic and phasic peripheral afferent signals during fictitious locomotion of both slow and fast rhythms were analysed in the cat. The tonic afferent inflow was conditioned by the position of the hindlimb. The phasic afferent signals were imitated by electrical stimulation of hindlimb nerves. The correlation between the kinematics of hindlimb locomotor movement and sensory inflow was investigated during actual locomotion. Reliable correlations between motor activity parameters during fictitious locomotion were revealed in cases of both slow and fast "locomotor" rhythms. The main difference between these cases was that correlations "duration-intensity" were positive in the first and negative in the second case. The functional role of "locomotor" pattern dependence on tonic sensory inflow consisted of providing stability for planting the hindlimb on the ground. For any investigated afferent input the phase moments in the "locomotor" cycle were found, in which an afferent signal caused no rearrangement in locomotor generator activity. These moments corresponded to the transitions between "flexion" and "extension" phases and to the bursts of integral afferent activity observed during real locomotion. The data obtained are compared with the results previously described for the scratching generator. The character of changes in "locomotor" activity in response to tonic and phasic sensory signals was similar to that of such changes in "scratching" rhythm in the case of fast "locomotion". Intensification of the "flexion" phase caused by phasic high-intensity stimulation of cutaneous afferents during low "locomotor" rhythm was changed to inhibition (such as observed during "scratching") when this rhythm was fast. It is concluded that the main regularities of peripheral afferent control for both the locomotor and scratching generators are the same. Moreover, these central pattern generators are just working regimes of a general spinal motor optimal control system containing the intrinsic model of limb movement dynamics. The consequences of this concept and ways of further research are discussed.

Animals↗