Instrumental Conditioned Reflex Research Articles

The effect of acoustic shielding of the region of a dolphin's mental foramina on its hearing sensitivity

The effect of acoustic shielding of the mental foramina of a bottlenose dolphin (Tursiops truncatus) on its auditory thresholds has been experimentally studied using the method of instrumental conditioned reflexes with food reinforcement. The detection thresholds of short broadband acoustic pulses deteriorated significantly (by 30–50dB) under conditions of acoustic shielding in the region of the mental foramina over the whole frequency band of the dolphin's hearing. Therefore, the mental foramina of its lower jaw take part in receiving and conducting the sounds into the mandibular fat in the entire frequency range of the dolphin's hearing. The obtained results give an experimental proof for the assumption that the morphological structures of the lower jaw play a role of the peripheral part of a dolphin's hearing. Now there are grounds to assume that Odontoceti have the similar peripheral part of their hearing. This assumption is based on the similarity of their morphology.

Bacterial melanin promotes recovery after sciatic nerve injury in rats.

Bacterial melanin, obtained from the mutant strain of Bacillus Thuringiensis, has been shown to promote recovery after central nervous system injury. It is hypothesized, in this study, that bacterial melanin can promote structural and functional recovery after peripheral nerve injury. Rats subjected to sciatic nerve transection were intramuscularly administered bacterial melanin. The sciatic nerve transected rats that did not receive intramuscular administration of bacterial melanin served as controls. Behavior tests showed that compared to control rats, the time taken for instrumental conditioned reflex recovery was significantly shorter and the ability to keep the balance on the rotating bar was significantly better in bacterial melanin-treated rats. Histomorphological tests showed that bacterial melanin promoted axon regeneration after sciatic nerve injury. These findings suggest that bacterial melanin exhibits neuroprotective effects on injured sciatic nerve, contributes to limb motor function recovery, and therefore can be used for rehabilitation treatment of peripheral nerve injury.

Initial training facilitates posttraumatic motor recovery in rats after pyramidal tract lesion and in conditions of induced regeneration

Training induces plastic changes within the normal and injured brain. Experiments were performed on 48 albino rats. Part of the experimental animals were initially trained to a balancing instrumental conditioned reflex (ICR). Unilateral bulbar pyramidotomy performed in all rats caused contralateral hemiparesis. To make the study results more reliable, recovery of motor skills was evaluated also in conditions of stimulated regeneration. The obtained results indicate that preoperative training in rats contributes to the accelerated recovery of learned motor skills.

Effects of Bacterial Melanin on Movement, Posture, and Skilled Balancing Deficits After Unilateral Destruction of Substantia Nigra Pars Compacta in Rats

ABSTRACT Sixteen adult male rats were initially trained to an instrumental conditioned reflex (ICR) and subjected to unilateral destruction of substantia nigra pars compacta. Part of the animals was injected with bacterial melanin solution on the next day of destruction. The other 8 rats served as the control group. Recovery rates for ICR and dynamics of paralyzed hindlimb movements were studied in both groups. Conditioned reflex and contralateral to lesion hindlimb movements recovered faster in rats injected with bacterial melanin after the destruction.

Effects of bacterial melanin on motor recovery and regeneration after unilateral destruction of Substantia Nigra pars compacta in rats

We examined the potential neuroprotective action of bacterial melanin (BM) in rats after unilateral destruction of Substantia Nigra pars compacta (SNc) dopaminergic neurons. 24 rats were initially trained to an instrumental conditioned reflex (ICR) and then subjected to unilateral electrolytic destruction of SNc. Unilateral deficit in balancing hindlimb movements was observed in all rats after the destruction. On the next day after the destruction part of the animals (n=12) was intramuscularly injected with BM solution at the concentration 6mg/ml (0.17g/kg). The other 12 operated rats served as a control group. On the second day after the operation the testing of instrumental conditioned reflex was resumed in both groups.Comparison of recovery periods for the ICR in both groups showed that recovery of the reflex and balancing hindlimb movements in melanin treated rats took place in three postoperative testing days, whereas in control group the recovery was not complete after 23 testing days. Electrophysiological study was conducted in 12 intact rats to show the effects of BM on the activity of SNc neurons. The firing rate of neurons was significantly increased by the BM injection.Morpho-histochemical study of brain sections was conducted after the completion of behavioral experiments. In melanin injected rats the study revealed absence of destruction or electrode trace in Substantia Nigra pars compacta of melanin injected rats. BM stimulates regeneration and microcirculation in SNc. Increased electrical activity of SN neurons and regenerative efforts induced by BM accelerate motor recovery after unilateral SNc destruction.

Bacterial Melanin Favors Regeneration after Motor Tract and Peripheral Nerve Damage

Experiments were performed on 48 albino rats. All experimental animals were initially trained to a balancing instrumental conditioned reflex (ICR). Unilateral bulbar pyramidotomy performed in 24 rats caused contralateral hemiparesis. On the next day following the operation 12 rats (first group) were injected intramuscularly with bacterial melanin (BM) solution. Recovery periods of ICR and paralyzed hindlimb movements were registered for melanin injected rats ( n = 12) and for operated rats, not treated with melanin ( n = 12, second group). In rats injected with bacterial melanin the posttraumatic recovery is shorter than in animals not treated with melanin. Morphohistochemical examination was carried out to confirm the results of behavioral and electrophysiological experiments. Medulla slices were prepared to trace the regeneration of nerve fibers. Examination of transection area revealed that bacterial melanin increases vascularization, dilates the capillaries in nervous tissue and stimulates the process of sprouting. Ischiadic nerve transection was performed in third and fourth groups of rats (12 rats in each group). Third group animals were injected with BM on the next day of surgery. ICR was used to assess the recovery of movements after nerve damage. Method for Ca 2+ -dependent acidic phosphatase activity measurement was used to examine sections of nerve fibers and to trace the recovery of the nerve and limb movements after its injury. Acceleration of the instrumental conditioned reflex recovery and data from morphohistochemical study showed that bacterial melanin has neuroprotective action and facilitates recovery of limb movements after peripheral nerve or motor tract lesions.

Neuroprotective action of bacterial melanin in rats after corticospinal tract lesions

Experiments were performed on 48 albino rats. Part of the experimental animals were initially trained to a balancing instrumental conditioned reflex (ICR). Unilateral bulbar pyramidotomy performed in all rats caused contralateral hemiparesis. On the next day following the operation 24 rats were injected intramuscularly with bacterial melanin solution. 12 of these rats were initially trained to ICR. Recovery periods of ICR and paralyzed hindlimb movements were registered for melanin injected rats (n=24) and for operated rats, not treated with melanin (n=24). In rats injected with bacterial melanin the posttraumatic recovery is shorter than in animals not treated with melanin. The fastest and complete recovery was registered in rats initially trained to ICR and injected after the operation with bacterial melanin. Electrophysiological experiments were performed in transected animals treated with melanin, transected animals without melanin treatment and intact animals. Spiking activity of motoneurons was registered in lumbar motoneurons of rats in response to high frequency stimulation above the corticospinal tract transection. Spiking activity was very similar in motoneurons of melanin injected and intact or non operated animals. In animals, not dosed with bacterial melanin after the operation, areactivity or no change in firing rate was registered in response to stimulus. Stimulation of the corticospinal tract of melanin injected rats produced potentiation of the motoneuronal firing rate and is an evidence of regeneration in corticospinal tract. Similarity in spiking activity of intact and melanin injected rats shows the recovery of conductance in pyramidal tract. Morphohistochemical examination was carried out to confirm the results of behavioral and electrophysiological experiments. Medulla slices were prepared to trace the regeneration of nerve fibers. Examination of transection area revealed that bacterial melanin increases vascularization, dilates the capillaries in nervous tissue and stimulates the process of sprouting.

Role of Acetylcholine in the Modulation of Activity of Neocortical Neurons in Awake Animals Performing an Instrumental Conditioned Reflex

We studied modulatory effects of the cholinergic system on the activity of sensorimotor cortex neurons related to realization of an instrumental conditioned placing reflex. Experiments were carried out on awake cats; multibarrel glass microelectrodes were used for extracellular recording of impulse activity of neurons in the sensorimotor cortex and iontophoretic application of synaptically active agents within the recording region. The background and reflex-related activity was recorded in the course of realization of conditioned movements, and then changes of spiking induced by applications of the testing substances were examined. Applications of acetylcholine and carbachol resulted in increases in the intensity of impulse reactions of neocortical neurons evoked by presentation of an acoustic signal and in simultaneous shortening of the response latencies. An agonist of muscarinic receptors, pylocarpine, exerted a similar effect on the evoked activity of sensorimotor cortex neurons. Blockers of muscarinic receptors, atropine and scopolamine, vice versa, sharply suppressed impulse reactions of cortical neurons to afferent stimulation and simultaneously increased latencies of these responses. Applications of an agonist of nicotinic receptors, nicotine, was accompanied by suppression of impulse neuronal responses, an increase in the latency of spike reactions to presentation of a sound signal, and a corresponding increase in the latency of a conditioned motor reaction. In contrast, application of an antagonist of nicotinic receptors, tubocurarine, significantly intensified neuronal spike responses and shortened their latency. The mechanisms underlying the effects of antagonists of membrane muscarinic and nicotinic cholinoreceptors and the role of activation of these receptors in the modulation of activity of pyramidal and non-pyramidal neocortical neurons related to realization of the instrumental motor reflex are discussed.

Recovery of instrumental conditioned reflexes in rats after pyramidotomy and action of bacterial melanin

Unilateral pyramidotomy at the bulbar level performed after preliminary elaboration of instrumental conditional reflex (ICR) and without its elaboration caused hemiparesis of extremities in rats. Next day after this operation a half of the operated animals both with elaborated ICE and without its elaboration was injected intramuscularly with bacterial melanin solution (170 mg/kg). Comparison of terms of recovery of ICR and of a balancing movement of the paralyzed hindleg in the operated rats without administration of melanin and with its injection showed that in the "melanin" animals the time of posttraumatic rehabilitation was much shorter and recovery of movement occurred faster and more completely. It has been found that the difference in terms of recovery of rat motor functions in this case is due to the protector action of bacterial melanin.

Jerzy Konorski on brain associations.

Jerzy Konorski (1903-1973) exerted a vital influence on the development of physiological psychology and neurobiology. Konorski and his friend and collaborator, Stefan Miller, distinguished instrumental conditioned reflexes as a separate type of acquired behavior, different from classical (Pavlovian) conditioned reflexes. In a series of pioneering studies Konorski demonstrated basic differences between the two types of conditioned reflexes. After the Second World War, he reinterpreted the results of research on conditioned reflexes on the basis of the mechanisms of Sherringtonian neurophysiology and introduced the term plasticity of the nervous system. His work, "Conditioned reflexes and neuron organization", published in 1948, signaled Konorski's place as one of the founders of contemporary neuroscience. He contributed significantly to the understanding of complex interactions of various classes of behaviors: innate and acquired, those driven by opposite motivations, and those elicited by cues signaling different contingencies. In his book "Integrative activity of the brain" (1967), Konorski analyzed the brain as a complex system directing the functioning of the organism as a whole.

Dopamine modulation of glutamate metabotropic receptors in conditioned reaction of sensory motor cortex neurons of the cat

The dopamine modulation of microiontophoretic application of antagonists of glutamate metabotropic synaptic transmission was studied in the sensory motor cortex of awake cats during instrumental conditioned reflex. The substances depressed the background and intensity of evoked impulse activity of pyramidal neurons of the sensory-motor cortex and provoked significant increases in the latency of impulse reaction and corresponding conditioned movements of animals. Simultaneous application of the antagonists and dopamine (DA) eliminated their depression of the background and evoked activity of neurons and decreased the latency of the impulse reactions and movements. Similar qualitative effects were observed in experiments with simultaneous application of biccuculine and (RS)-alpha-methyl-4-carboxyphenylglycine. It is supposed that the DA modulation in the brain consists in stabilizing the background and evoked activity of cortical neurons during reduced intensity of metabotropic glutamatergic synaptic transmission. Such modulation can be important when considering some pathological disorders of glutamatergic transmission.

Reversal of visual discrimination and visual acute extinction in cats with poor or limited early visual experience.

Transformation of visual instrumental conditioned reflexes rewarded with food was compared in cats binocularly deprived of pattern vision in the early period of life (BD cats), control cats reared also in the laboratory but with open eyes (C cats) and cats reared in normal environment (N cats). In Expt. I the cats were given 4 sequential reversal trainings of cross vs. disc discrimination and in Expt. II a response to a gate marked with a cross or a disc was submitted to 4 sequential acute extinctions and restorations. The results show that both visual deprivation and rearing in monotonous laboratory environment moderately affect transformation of associations between visual stimuli and hunger drive and instrumental responses. However, in BD cats transformation learning is less impaired than previously studied visual discrimination learning.

Superconsolidated conditioned reflex--a highly adaptive system of behavior.

Superconsolidated (2500-3000 combinations), long-trained (two to three years), specialized (per I.P. Pavlov), instrumental alimentary conditioned reflexes were investigated in cats. It was demonstrated that such conditioned reflexes are unusually rapidly extinguished, despite the classical notion of extinction, according to which the more consolidated the conditioned reflex the more difficult it is and the longer it takes to extinguish it. Thus, in the very first experiment, stable extinction of the conditioned reflex commenced after two to seven (in different animals) presentations of the conditional stimulus without reinforcement, and 15-20 "zeros" in a row in relation to the conditioned reaction could be obtained. The rate of extinction essentially did not depend on the individual features of the animals or the level of alimentary motivation. The data obtained make it possible to set such reflexes apart in a special new category of conditioned reflexes, which apparently have a different neurophysiological and structural control base than the "younger" conditioned reflexes commonly studied in the laboratory.

Food-procuring behavior of rats under the conditions of chronic activation and blockade of the neostriatal dopaminergic system.

Using the technique of intracerebral microinjections, the features of food-procuring behavior (the realization of a situational instrumental conditioned reflex in a Skinner box) were investigated in rats in experiments under the conditions of a pharmacological influence on the dopaminergic system of the neostriatum. Amphetamine in a dose of 15 and 45 micrograms and haloperidol in a dose of 5 mg were injected daily over the course of three weeks bilaterally into the rostral division of the neostriatum. A amphetamine dose of 15 micrograms was ineffective, but a increase in motor hyperactivity, a behavioral stereotypy, and a substantial acceleration of food-procuring movements were observed against the background of the injection of 45 micrograms of amphetamine. Stimulation of the dopaminergic system of the neostriatum qualitatively altered the behavioral strategy in animals with an initially low level of realization of the reflex; this fostered a stable activation of the instrumental skill enduring even after the cessation of the microinjections. Chronic blockade of dopamine receptors by haloperidol induced the reverse effect.

Characteristics of the influences of the centrum medianum of the thalamus on the neuronal activity of the caudate nucleus.

The specific character of the relationship of the baseline cellular activity of the caudate nucleus to the features of the impulse activity of the centrum medianum of the thalamus has been identified in chronic microelectrode experiments. Reciprocal changes in the bioelectrical activity were recorded in the first group of cells, with a low action potential repetition frequency, while unidirectional changes with reorganizations in the intralaminar nucleus were recorded in the second. The activation of the cells of the centrum medianum of the thalamus was accompanied during the formation of an instrumental conditioned defense reflex by the formation of a pattern of impulse activity in neurons of the neostriatum which coincided in sign with the reorganizations which were characteristic during the investigation of the baseline activity. It is hypothesized that the features of the internal structure of the caudate nucleus underlie such a relationship.

Intralimbic evoked potentials during the formation of an alimentary conditioned reflex in response to the electrostimulation of the hippocampus of dogs.

Instrumental alimentary conditioned reflexes (CR) in response to the electrostimulation of the hippocampus were developed in experiments on dogs with electrodes implanted in various divisions of the hippocampus, the amygdala, the septum, and the hypothalamus. During their development the evoked potentials (EP) were investigated in the hippocampus itself and in other limbic structures, as well as in the hippocampus during the testing of the latter for the purpose of verifying generalization. The formation and extinction of the CR was accompanied by changes in the amplitude-temporal characteristics primarily of late components of the EP picked up from the lateral hypothalamus and the amygdaloid complex in response to the hippocampal electrostimulation. During the carrying out of this stimulation of signal functions (pedal pressing to obtain food), the average amplitude of the trace positivity and of the late negative wave were found to be lower than by the end of extinction in the presence of ineffectiveness of the signal. The average amplitudes of the late components of the hippocampal EP which arose in response to electrostimulation of the amygdala were lower in those tests in which the instrumental movement appeared when the generalization of the CR was tested.

Role of the basal ganglia in the reproduction of instrumental reactions developed in response to electrostimulation of the hippocampus

A defensive instrumental conditioned reflex (CR) successively to light flashes and to electrostimulation of the dorsal hippocampus (DH) and the caudate nucleus (CN) was developed in dogs with electrodes implanted in the brain. The contralateral of the DH, CN, the accumbent nucleus (AN) and the globus pallidus (GP) were tested for reproducibility of the instrumental movement. In a second series, the percent of evoked movements was compared with the EP arising in response to signal and test stimulation. The degree of participation of the tested structures in the motivational, signal, and executive components of the CR was elucidated. In the first series the movements were practically not reproduced. In the second series, in the presence of connections from the signal to the tested structures, they were elicited only by stimulation of the AN (15%). In the same series, given bilateral connections, movements in response to the stimulation of the basal ganglia occurred somewhat more frequently (up to 28%). The stimulation of the contralateral DH elicited movements in 75-100% of cases. When stimulation of the CN became a signal, the stimulation of the AN and the GP was accompanied in 40-100% of cases by movement. Thus, the AN participates to a minimal degree in the executive component of the CR. Participation of the basal ganglia in the signal component of the CR was greatest in the third series, which indicates that intrasystemic generalization is more effective than intersystemic.

Neuronal spike response produced in the feline thalamic reticular nucleus by instrumental conditioned reflex

Spike response was investigated in 156 units of the thalamic reticular nucleus (RN) during performance of the instrumental feeding reflex of lever-pressing. This response consisted of lead and lag phases. Latency of the lead phase of response varied between 10 and 100 msec and total duration of response between 50 and 250 msec; minimum latency of the lag phase: 100–300 msec. Initial response to a conditioning clicking sound was found in 27 units, of which 26 showed excitation and the remaining single unit an inhibitory-excitatory pattern. The lag stage of response associated with performance of conditioned lever-pressing was found in 134 neurons, of which 115 showed an excitatory pattern, 19 displayed inhibition and the remaining 22 units failed to respond. The lag phase of response preceded the onset of conditioned reflex movement (CRM) in 30 neurons. A total of 118 neurons responded between the onset of CRM and the point of lever-pressing. It was concluded that the RN plays a part in perception of the conditioned signal as well as producing and controlling performance of CRM.

Cortical multineuronal activity in dogs with defensive instrumental conditioned reflex

For the first time in dogs with semi-microelectrodes chronically implanted in the motor and somatosensory region of the cortex, background multineuronal activity (MNA) was recorded over the long term followed by an amplitudinal discrimination from the MNA of impulse series presumably belonging to cells of large, medium, and small size was performed. The presence of close synergistic functional connections, particularly significant during the avoidance conditioned reflex and its extinction, was established by determining the correlation coefficient (CC) between the impulse flows of these neurons. In trained animals the highest CC values were observed between neurons with a small and medium spike amplitude. The network properties of identified neurons were studied by constructing histograms of cross interval relationships. The connections established were of primarily a unilateral, excitatory character.

Neuronal responses in the cat substantia innominata during instrumental conditioned reflex

Neuronal spike activity in the substantia innominata was investigated when establishing the instrumental conditioned reflex of lever-pressing with food reinforcement during chronic experiments on cats. Spike activity changed in 44.3% of neurons during this process; 24.3% responded directly to conditioned acoustic stimulation. Reactions associated with conditioned reflex movement were less pronounced. Response of peak intensity and duration was observed during food reinforcement, when the reaction occasionally occurred 500 msec in advance of the reinforcement provided. Involvement of cholinergic substantia innominata neurons in reinforcement is thought to be responsible for the persistence of residual effects in neocortical neurons.