Models of learning based on the plastic properties of the "placing reaction" in cats]

A possibility of functional reorganization of initial sensorimotor connections of the forepaw has been shown on seven cats. The main initial relationships between the afferent tactile input and motor output for the ulnar joint of the cat forepaw are as follows: tactile stimulation of the dorsal surface of the paw produces a flexion in the ulnar joint ("placing reaction"), and that of the ventral surface, an extension of the paw in the ulnar joint ("magnetic reflex"); simultaneous tactile stimulation of the ventral surface of the paw blocks the "placing reaction" evoked by a touch of the dorsal side. Extinction was produced of the above unconditioned connections and elaboration of a new "cross" connection consisting in that tactile stimulation of the ventral side of the paw resulted in flexion in the ulnar joint.     

The activity of cat motor cortex neurons during performance of a conditoned response of placing the forepaw on a support]

The activity of 74 units of the cat precentral motor cortex was studied in the process of reaction of placing the forepaw on a support. It has been shown that the neurones controlling the flexion of the ulnar joint, the first phase of the reaction, receive an afferent tactile input primarily from the dorsal side of the paw, i.e. from region of the skin surface which is the receptive field of the reflex of placing the paw on the support. Learning the animals to lift the paw to the support in response to a touch of the ventral surface results in an increase of discharge frequency of the studied units in response to ventral stimulation similar to that recorded in response to the initially effective dorsal stimulation.     

The reactions of the cat motor cortex neurons to electrical stimulation of the base of the forebrain as a conditioned signal for the reflex of placing the forelimb on a support]

Electrical stimulation of the globus pallidus (500 ms, 300 Hz) in the area restricted by the stereotaxic coordinates AP 14-AP 16, L5-L8 at the level of the anterior commissura (HO) evoked food reactions in the form of mouth opening, chewing, and licking in the absence of food. There were no visible motor effects in the case of electrical stimulation of the subcommissural area (H-2-H-4) corresponding to the ventral pallidum and substantia innominata. The conditioned forepaw placing reaction was elaborated with the basal forebrain stimulation used as a conditioned stimulus. After conditioning, the short (3-5 pulses) conditioned basal forebrain stimulation evoked a prolonged (up to 500-1000 ms) activation of neurons in the motor cortex. This activation did not change in the absence of the movement, i.e., after acute extinction of the contralateral forepaw placing or transfer of placing reaction to the ipsilateral forepaw.     

The blockade of D1 dopamine receptors in cat motor cortex causing an increase in the latency of conditioned forelimb placing reaction

Cat were trained to place a forepaw on a support in response to touching the ventral surface of the forepaw as a conditioned stimulus. A selective D1 receptor antagonist SCH23390 was injected under pressure into the region of pericruciate cortex just anterior and lateral to the end of the cruciate sulcus. Electrical microstimulation of this region evoked the elbow flexion and shoulder withdrawal that constitute the initial lifting--withdrawal phase of the forepaw placing. In contrast to control saline, the injection of SCH23390 caused a gradual increase in the latency of conditioned placing so that to the end of experiment it was, on the average, 200 ms longer than its preinjection level. The results obtained show that the local D1 receptor blockade in cat motor cortex significantly increases the latency of the simple instrumental conditioned reflex.     

The neuronal reactions of the cat motor cortex to electrical stimulation of the ventral tegmental area as a conditioned signal for the reflex of placing the forelimb on a support]

Electrical stimulation (50-100 pulses, 100-500 Hz) of the ventral tegmental area (VTA) in the vicinity of the n. interpeduncularis in the frontal plane AP2-AP4, L1-L2 caused a cat to grab food placed near its mouth. The conditioned forepaw placing reaction was elaborated using food reinforcement and VTA stimulation as a conditioned stimulus. The conditioned reflex, being once established, was repeatedly performed without extinction in the course of up to 250 trials without food reinforcement. Short (5-10 pulses) conditioned VTA stimulation evoked a prolonged (up to 1000 ms or longer) activation of neurons of the motor cortex and caused a substitution of the inhibitory phase of response to stimulation of the parietal cortex in poststimulus interval in 50-200 ms for the late secondary excitatory response.     

Role of the motor area of the cortex in the performance of the postural escape reaction

It has been shown on three dogs that unilateral ablation of the cortical motor area temporally disturbs previously acquired and opposite to the innate postural escape reaction to electric stimulation of the contralateral forepaw by increasing its pressure on the support. After 3-4 months of repeated training, compensation is possible. Bilateral ablation of the motor cortex elicits stable and unreversible disturbance of the acquired reaction. In reorganization of postural coordinations, motor cortex functions are connected with the inhibition of innate coordinations preventing performance of the reaction.     

Imaging the spatio-temporal dynamics of supragranular activity in the rat somatosensory cortex in response to stimulation of the paws

We employed voltage-sensitive dye (VSD) imaging to investigate the spatio-temporal dynamics of the responses of the supragranular somatosensory cortex to stimulation of the four paws in urethane-anesthetized rats. We obtained the following main results. (1) Stimulation of the contralateral forepaw evoked VSD responses with greater amplitude and smaller latency than stimulation of the contralateral hindpaw, and ipsilateral VSD responses had a lower amplitude and greater latency than contralateral responses. (2) While the contralateral stimulation initially activated only one focus, the ipsilateral stimulation initially activated two foci: one focus was typically medial to the focus activated by contralateral stimulation and was stereotaxically localized in the motor cortex; the other focus was typically posterior to the focus activated by contralateral stimulation and was stereotaxically localized in the somatosensory cortex. (3) Forepaw and hindpaw somatosensory stimuli activated large areas of the sensorimotor cortex, well beyond the forepaw and hindpaw somatosensory areas of classical somatotopic maps, and forepaw stimuli activated larger cortical areas with greater activation velocity than hindpaw stimuli. (4) Stimulation of the forepaw and hindpaw evoked different cortical activation dynamics: forepaw responses displayed a clear medial directionality, whereas hindpaw responses were much more uniform in all directions. In conclusion, this work offers a complete spatio-temporal map of the supragranular VSD cortical activation in response to stimulation of the paws, showing important somatotopic differences between contralateral and ipsilateral maps as well as differences in the spatio-temporal activation dynamics in response to forepaw and hindpaw stimuli.     

Participation of the hippocampus in regulating a pathologic inactive motor reaction in dogs

A local pathological inert motor reaction, involving a forced flexion of the forepaw, was formed after simultaneous stimulation with NaCl solution of a part of the tongue brought out to the cheek and electrical stimulation of the forepaw. The reaction decreased (by 70 to 80%) after electrical stimulation of the dorsal hippocampus (beyond CA3). At the same time the animal's emotional stress diminished, as evidenced by the reduced heart rate and a reduced theta-rhythm in the hippocampus.     

研究报告: 大鼠感觉运动系统静息态脑网络研究

为了理解啮齿类动物的脑功能连接,本文利用9.4T fMRI获得轻度麻醉状态下大鼠静息状态及刺激激活的数据,通过互相关分析构建节点之间的相关系数矩阵并计算相应的网络参数．结果发现：给予前爪电刺激时,刺激对侧初级感觉皮层(S1)、丘脑(Tha)有较强的正激活,双侧尾状壳核(CPu)有较强的负激活．静息状态时大鼠感觉/运动皮层内部、丘脑内部的连接性较强,而感觉/运动皮层与丘脑之间的连接较弱,双侧感觉运动系统之间存在较强的同步低频振荡,感觉运动系统在静息态时的脑网络具有小世界属性．结果提示,啮齿类动物在大脑信息处理中的功能分离和整合可能与人类存在某些相似性,支持哺乳动物中枢神经系统的基本功能存在遗传保守性的观点．     

Transformation of the afferent tactile signal into a motor command in the cat motor cortex

Activity of 112 neurons of the precruciate motor cortex in cats was studied during a forelimb placing reaction to tactile stimulation of its distal parts. The latent period of response of the limb to tactile stimulation was: for flexors of the elbow (biceps brachii) 30–40 msec, for the earliest reponses of cortical motor neurons about 20 msec. The biceps response was observed 5–10 msec after the end of stimulation of the cortex with a series of pulses lasting 25 msec. Two types of excitatory responses of the neurons were identified: responses of sensory type observed to each tactile stimulation of the limb and independent of the presence or absence of motion, and responses of motor type, which developed parallel with the motor response of the limb and were not observed in the absence of motion. The minimal latent period of the responses of motor type was equal to the latent period of the sensory responses to tactile stimulation (20±10 msec). Stimulation of the cortex through the recording microelectrode at the site of derivation of unit activity, which increased during active flexion of the forelimb at the elbow (11 stimuli at intervals of 2.5 msec, current not exceeding 25 µA), in 70% of cases evoked an electrical response in the flexor muscle of the elbow.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 9, No. 2, pp. 115–123, March–April, 1977.     

The long-term potentiation of the late NMDA-dependent components of the responses of the cat motor cortex neurons to stimulation of the direct cortical input of area 5 in the parietal cortex]

Activity of neurons in the motor cortex was recorded in anesthetized cats with glass micropipettes filled with bicuculline solution (bicuculline methiodide, 10 mM in 1 M NaCl). Under these conditions, the minimal (near-threshold) electrical stimulation of the area 5 of the parietal cortex evoked the late neuronal discharges (in 30-200-ms poststimulus interval) in the motor cortex. Such discharges resembled the late NMDA-dependent discharges recorded in the motor cortex of awake cats in response to stimulation of the parietal cortex, which produced the preliminary elaborated conditioned forepaw placing. Under the same conditions, tetanic stimulation of the parietal cortex (100 Hz, 10-20s) led to the long-term potentiation of the late response, which manifested itself as response amplitude augmentation and latency shortening.     

Three-dimensional electrophysiological topography of the rat corticostriatal system

Projections from the cerebral cortex are the major afferents of the caudoputamen and probably determine the functions subserved by each region of the nucleus. The corticostriatal system has been mapped using cytological techniques which give little information on the physiological importance of projections from individual cortical areas. The objective of this study was to characterize the three-dimensional topography of the corticostriatal system in the rat and to determine the physiological significance of these projections using electrophysiological techniques. Eight functionally distinct areas of the cerebral cortex (prefrontal, primary motor, rostral and caudal primary somatosensory, hindlimb, auditory, occipital and primary visual) were stimulated while recording the multiple unit activity in seven dorsal and seven ventral areas of the caudoputamen. Each stimulation site produced a distinctive pattern of activation within the caudoputamen. There was also a large site-dependent variation in electrophysiological activation produced by each stimulation. The motor and somatosensory areas produced the most powerful overall activation. In addition, a number of trends were obvious. There was a rostrocaudal topographical relationship between the site of stimulation and the area of the caudoputamen activated. Furthermore, more caudally and medially placed stimulation sites produced greater dorsal activation of the caudoputamen relative to ventral.     

NMDA-dependent and NMDA-independent neuronal processes in the cat motor cortex,disinhibited by bicuculline,during forepaw placement conditioning

Neuronal activity associated with a conditioned forepaw placing reaction was recorded in the cat's motor cortex locally disinhibited by bicuculline spontaneously diffused from the recording pipette. Electrical stimulation of the parieral cortex (area 5) with 3-5 pulses was used as a conditioned stimulus. In both naive and trained cats, adding of APV (NMDA receptor blocker) led to disappearance of the late (30-120 ms) secondary excitatory responses from the pattern of the neuronal reaction to the parietal stimulation recorded in the motor cortex. At the same time, the APV administration did not change the excitatory reactions (recorded, predominantly, in the deep cortical layers) time-locked to the execution of the conditioned movement. The conditioning resulted in a statistically significant increase in the amplitude and duration of the late secondary responses as well as in a shortening of their latency. In some cases (after a long period of training), the late secondary responses to the conditioned stimulus transformed into paroxysmal epileptiform bursts. A hypothesis is discussed that the increase in synaptic strength of the backward horizontal collaterals of layer-II/III pyramidal neurons is responsible for the learning-related changes in the neuronal reactions in the disinhibited motor cortex.     

The participation of the cholinergic system of the rat sensorimotor cortex in regulating different types of movements

To study the role of the cholinergic system of the sensorimotor cortex in regulation of different manipulatory movements and locomotion of Wistar rats, the effects of injections of cholinergic drugs (a cholinergic agonist carbachol and an antagonist scopolamine) into the area of forepaw representation in the sensorimotor cortex on motor activity and performance of manipulatory movements (with prolonged and short pushing) were analyzed. The drugs were injected via special cannulae stereotaxically implanted into the cortex during surgery carried out under Nembutal anesthesia. Carbachol injections (0.03-3 micrograms in 1 microliter of physiologic solution) into the cortex resulted in a significant slowing down of both types of movements as well as an increase in locomotion in the open-field test. Injections of scopolamine (0.3-3 micrograms) into the same cortical area were accompanied by an increase in the number of fast manipulatory movements without significant changes in locomotor activity. The obtained evidence suggests that the cholinergic system of the sensorimotor cortex indifferent manners regulates the innate (locomotion) and acquired movements which require different periods of maintaining the muscle tone of the forepaw (short-time periods for the usual movements necessary for food taking from the narrow horizontal tube and prolonged periods for the learned slow movements with additional tactile and tonic components).     

Corticofugal influences on reticulospinal neurons of the gigantocellular nucleus in cats

It was shown by intracellular recording that stimulation of the motor cortex evokes E PS Ps and I PS Ps in reticulospinal neurons of the gigantocellular nucleus of the cat medulla. The E PS Ps appeared in 94.3% and the I PS Ps in 5.7% of neurons tested. Analysis of the presynaptic pathway showed that 77.4% of E PS Ps studied arose through monosynaptic, and 22.6% through polysynaptic corticoreticular connections. By their latent period, duration, and rise time up to a maximum the monosynaptic E PS Ps were divided into two groups: "fast" and "slow." It is postulated that "fast" E PS Ps are generated in reticulospinal neurons which are activated by fast-conducting fibers and "slow" E PS Ps by slowly conducting corticobulbar fibers. I PS Ps were recorded from reticulospinal neurons that also were inhibited by stimulation of the ventral columns of the spinal cord. The hypothesis is put forward that cortical motor signals in cats can be transmitted to the spinal cord via monosynaptic and polysynaptic connections of "fast" and "slow" pyramidal neurons with reticulospinal neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 3, pp. 250–257, May–June, 1976.     

Illusory sensation of movement induced by repetitive transcranial magnetic stimulation

Human movement sense relies on both somatosensory feedback and on knowledge of the motor commands used to produce the movement. We have induced a movement illusion using repetitive transcranial magnetic stimulation over primary motor cortex and dorsal premotor cortex in the absence of limb movement and its associated somatosensory feedback. Afferent and efferent neural signalling was abolished in the arm with ischemic nerve block, and in the leg with spinal nerve block. Movement sensation was assessed following trains of high-frequency repetitive transcranial magnetic stimulation applied over primary motor cortex, dorsal premotor cortex, and a control area (posterior parietal cortex). Magnetic stimulation over primary motor cortex and dorsal premotor cortex produced a movement sensation that was significantly greater than stimulation over the control region. Movement sensation after dorsal premotor cortex stimulation was less affected by sensory and motor deprivation than was primary motor cortex stimulation. We propose that repetitive transcranial magnetic stimulation over dorsal premotor cortex produces a corollary discharge that is perceived as movement.     

Conditioned reflex analysis of functional connections between the hippocampus and limbic system structures

Instrumental defensive conditioned reflex elaborated in dogs to stimulation of the dorsal and ventral hippocampus, also appeared, due to generalization, in response to stimulation of a number of limbic structures. Two types of changes in the generalization effects (estimated by parameters of motor conditioned reaction) were observed in the course of conditioned reflex stabilization: enhancement (in response to stimulation of the lateral hypothalamus, lateral nucleus of septum, limbic cortex) and weakening toward complete disappearance (in response to stimulation of the medial nucleus of amygdala and medial hypothalamus). Manifestation of the generalization phenomenon from the brain structures, which are not involved initially into conditioned activity, suggests the existence of close functional connections between these structures and the hippocampus.     

A stimulus-driven approach to object identity and location processing in the human brain

The primate visual system is considered to be segregated into ventral and dorsal streams specialized for processing object identity and location, respectively. We reexamined the dorsal/ventral model using a stimulus-driven approach to object identity and location processing. While looking at repeated presentations of a standard object at a standard location, subjects monitored for any infrequent "oddball" changes in object identity, location, or identity and location (conjunction). While the identity and location oddballs preferentially activated ventral and dorsal brain regions respectively, each oddball type activated both pathways. Furthermore, all oddball types recruited the lateral temporal cortex and the temporo-parietal junction. These findings suggest that a strict dorsal/ventral dual-stream model does not fully account for the perception of novel objects in space.     

Neural Basis of Limb Ownership in Individuals with Body Integrity Identity Disorder

Our body feels like it is ours. However, individuals with body integrity identity disorder (BIID) lack this feeling of ownership for distinct limbs and desire amputation of perfectly healthy body parts. This extremely rare condition provides us with an opportunity to study the neural basis underlying the feeling of limb ownership, since these individuals have a feeling of disownership for a limb in the absence of apparent brain damage. Here we directly compared brain activation between limbs that do and do not feel as part of the body using functional MRI during separate tactile stimulation and motor execution experiments. In comparison to matched controls, individuals with BIID showed heightened responsivity of a large somatosensory network including the parietal cortex and right insula during tactile stimulation, regardless of whether the stimulated leg felt owned or alienated. Importantly, activity in the ventral premotor cortex depended on the feeling of ownership and was reduced during stimulation of the alienated compared to the owned leg. In contrast, no significant differences between groups were observed during the performance of motor actions. These results suggest that altered somatosensory processing in the premotor cortex is associated with the feeling of disownership in BIID, which may be related to altered integration of somatosensory and proprioceptive information.     

Morphology of the Mechanosensory Lateral Line System in Elasmobranch Fishes: Ecological and Behavioral Considerations

The relationship between morphology of the mechanosensory lateral line system and behavior is essentially unknown in elasmobranch fishes. Gross anatomy and spatial distribution of different peripheral lateral line components were examined in several batoids (Raja eglanteria, Narcine brasiliensis, Gymnura micrura, and Dasyatis sabina) and a bonnethead shark, Sphyrna tiburo, and are interpreted to infer possible behavioral functions for superficial neuromasts, canals, and vesicles of Savi in these species. Narcine brasiliensis has canals on the dorsal surface with 1 pore per tubule branch, lacks a ventral canal system, and has 8–10 vesicles of Savi in bilateral rows on the dorsal rostrum and numerous vesicles ( = 65 ± 6 SD per side) on the ventral rostrum. Raja eglanteria has superficial neuromasts in bilateral rows along the dorsal body midline and tail, a pair anterior to each endolymphatic pore, and a row of 5–6 between the infraorbital canal and eye. Raja eglanteria also has dorsal canals with 1 pore per tubule branch, pored and non-pored canals on the ventral surface, and lacks a ventral subpleural loop. Gymnura micrura has a pored dorsal canal system with extensive branch patterns, a pored ventral hyomandibular canal, and non-pored canal sections around the mouth. Dasyatis sabina has more canal pores on the dorsal body surface, but more canal neuromasts and greater diameter canals on the ventral surface. Sphyrna tiburo has primarily pored canals on both the dorsal and ventral surfaces of the head, as well as the posterior lateral line canal along the lateral body surface. Based upon these morphological data, pored canals on the dorsal body and tail of elasmobranchs are best positioned to detect water movements across the body surface generated by currents, predators, conspecifics, or distortions in the animal's flow field while swimming. In addition, pored canals on the ventral surface likely also detect water movements generated by prey. Superficial neuromasts are protected from stimulation caused by forward swimming motion by their position at the base of papillar grooves, and may detect water flow produced by currents, prey, predators, or conspecifics. Ventral non-pored canals and vesicles of Savi, which are found in benthic batoids, likely function as tactile or vibration receptors that encode displacements of the skin surface caused by prey, the substrate, or conspecifics. This mechanotactile mechanism is supported by the presence of compliant canal walls, neuromasts that are enclosed in wide diameter canals, and the presence of hair cells in neuromasts that are polarized both parallel to and nearly perpendicular to the canal axis in D. sabina. The mechanotactile, schooling, and mechanosensory parallel processing hypotheses are proposed as future directions to address the relationships between morphology and physiology of the mechanosensory lateral line system and behavior in elasmobranch fishes.