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Preliminary intravenous injection of thyrotropin-releasing hormone in a dose of 20 g/kg to cats with developing myocardial ischemia during stimulation of the cerebrocortical sensorimotor zone had a pronounced antiarrhythmic effect.
Experiments were performed to determine the action of the dentate output on neurons in the spinal cord mediated by pathways which do not involve the primary sensorimotor and premotor cortices. The dentate nucleus was electrically stimulated by stereotaxically placed electrodes in Rhesus monkeys whose contralateral sensorimotor and premotor cortices were ablated. The resultant changes in excitability of lumbar alpha motorneurons activated by Ia afferents from nerves innervating femoral, hamstring, gastrocnemius-soleus and peroneal muscles were measured by intracellular recordings and by determining the percent change in the amplitude of the monosynaptic reflex recorded from ventral roots. The effect of stimulation of the dentate nucleus on proprioceptive reflexes was determined by recording the changes in postsynaptic potentials evoked by selective stimulation of Ia and Ib afferent fibers. The results demonstrated that dentate nucleus exerts a significant action on the excitability of spinal neurons via pathways which do not include the sensorimotor and premotor cortices. Whether the dentate stimulus produced an increase or decrease in the excitability of these neurons was dependent upon the site within the dentate nucleus at which the stimulus was applied, demonstrating that, in the decorticate preparation, the output from this nucleus is quite heterogeneous. In addition, stimulation of the dentate nucleus in these monkeys did not affect the Ia reflex pathway but significantly changed the amplitude of the inhibitory postsynaptic potential evoked by Ib afferents in lumbar alpha motorneurons.
This functional magnetic resonance imaging study verified an antagonistic pattern in which a concomitant deactivation of ipsilateral primary sensorimotor (SM1) was coupled to the contralateral SM1 activation in healthy controls during unimanual hand grasping. Of note, dramatic reduction of ipsilateral SM1 deactivation (loss of antagonistic pattern) was observed during movement of intact hands by patients with unilateral brachial plexus injury. We propose that the disappearance of the antagonistic pattern of SM1 activities in the patients with brachial plexus injury reflects a reduction of interhemispheric inhibition, which may mirror an adaptive mechanism to functional status.
Long-term potentiation (LTP) of synaptic transmission is considered to be a neuronal model of learning. Recently, the probability of induction of associative LTP in layer V cells in sensorimotor neocortex was shown to be much higher in the awake cat than in the slice preparation. We hypothesised that the loss of extrinsic noradrenergic activity in the slice might account for this difference, particularly since a beta-adrenergic enhancement of field potentials has been seen in this preparation. We therefore bath-applied noradrenaline (NA) or the beta 1-adrenergic agonist, isoprenaline (ISO) to elucidate the cellular basis of the enhancement of field potentials, and to see if the drugs increased the probability of induction of associative LTP in slices. We found that NA and ISO produced a dose-dependent, reversible reduction of spike accommodation and an increase in excitability but had no effect on the depolarizing slope or peak amplitude of sub-threshold EPSPs, and that drug application did not increase the probability of induction of LTP. We conclude that: (1) the enhancement of field potentials and late components of EPSPs (7) can be explained by the known actions of beta-adrenergic drugs on membrane currents in layer V cells, and (2) the lower probability of induction of associative LTP in slices cf. the awake cat cannot be due solely to the loss of noradrenergic activity.
State of hunger is characterized by the presence of definite distribution of interimpulse intervals in the activity of sensorimotor cortical neurones (SMC) of rabbit. Mostly bi- and three-modal distribution of interimpulse intervals in the background activity in hungry animals changes in the process of elaboration of food-procuring habit. As the habit consolidates, the SMC neurones acquire the ability to forestalling actions. Peculiarities are revealed of organization of the SMC neurones impulse stream in response to the action of conditioned signal in the case of abolition or substitution of the reinforcement. Repeated substitutions of reinforcement cause the formation of activity of concordance in the moment of substitute "recognition" despite the absence of alimentary reinforcement.
Functional magnetic resonance imaging (fMRI) has found widespread clinical interest. Difficulties in clinical use of the fMRI technique arise, considering the lack of knowledge about activation task performance. This accounts especially for sensorimotor activation studies, in which performance of the sensorimotor activation task is-if at all-usually rated visually by subjective or semiquantitative methods (i.e., defining categories of performance such as neurological soft signs scales). Recently, instrumental methods for the measurement and analysis of motor performance have been developed. Pronation/supination (hand rotation) movement was shown to be an easily measurable and promising motor task. We have adapted a mechanic device (pronation/supination device, PSD) to monitor motor performance during the fMRI experiment. In a feasibility study, an investigation of fMRI activation strength dependence of sensorimotor cortices and supplementary motor area upon task frequency (25, 50, and 75 cycles/min) was carried out on 10 right-handed healthy volunteers. Furthermore, the authors report the observation of stimulus-induced activation changes in the cerebellum during pronation/supination movement.
1. Intracellular recording techniques were used to investigate the physiological and pharmacological properties of stimulus-induced excitatory postsynaptic potentials (EPSPs) recorded in regular-spiking cells located in layers II/III of rat sensorimotor cortical slices maintained in vitro. 2. Depending on the strength of the extracellular stimuli, a pure EPSP or an EPSP-inhibitory postsynaptic potential sequence was observed under perfusion with normal medium. The EPSPs displayed short latency of onset [2.4 +/- 0.7 (SD) ms] and were able to follow repetitive stimulation (tested less than or equal to 5 Hz). Variation of the membrane potential (Vm) revealed two types of voltage behavior for the short-latency EPSP. The first type decreased in amplitude with depolarization and increased in amplitude with hyperpolarization. In contrast, the second type behaved anomalously by increasing and decreasing in size after depolarization and hyperpolarization, respectively. 3. Several experimental procedures were carried out to investigate the mechanism underlying the anomalous voltage behavior of the EPSP. Results indicated that this type of Vm dependency could be mimicked by an intrinsic response evoked by a brief pulse of depolarizing current and could be abolished by N-(2,6-dimethylphenylcarbamoylmethyl)triethylammonium bromide (50 mM). Furthermore, the EPSP was not sensitive to the N-methyl-D-aspartate (NMDA) receptor antagonist 3-((+-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonate (CPP, 10 microM). Thus the anomalous voltage relationship of the neuronal membrane. 4. The involvement of non-NMDA receptors in excitatory synaptic transmission was investigated with their selective antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 1-10 microM). This drug greatly reduced or completely blocked the EPSP in a dose-dependent manner (1-10 microM). The IC50 for the CNQX effect was approximately 2 microM. In the presence of CNQX (10 microM) and glycine (10 microM), synaptic stimulation failed to elicit firing of action potential. However, a CPP-sensitive EPSP was observed. 5. When synaptic inhibition was reduced by low concentration of bicuculline methiodide (BMI, 1-2 microM), extracellular stimulation revealed late EPSPs (latency to onset: 10-30 ms) that were not discernible in normal medium. Similar to the short-latency EPSP, the Vm dependency displayed by this late EPSP could be modified by inward membrane rectifications. The late EPSP appeared to be polysynaptic in origin because 1) its latency of onset was long and variable and 2) it failed to follow repetitive stimuli delivered at a frequency that did not depress the short-latency EPSP.(ABSTRACT TRUNCATED AT 400 WORDS)
Spatially informative visual precues give rise to event-related potential asymmetries with higher negativities over the contralateral hemisphere. However the attribution of these potentials to sensorimotor areas is still unclear. The present magnetoencephalography study assessed movement preparation processes to auditory spatial precues. Event-related desynchronization (ERD) was measured to test the hypothesis that lateralized sounds would give rise to a fast, stimulus-driven activation of motor networks independent of the precued response side. The lateralized vowels /a/ and /e/ served as precues for either ipsi- or contralateral responses, respectively, which had to be executed when an imperative stimulus was presented 1 s after precue onset. Two separate experiments were conducted with either blocked or mixed presentation of ipsi- and contralateral precues. Beta ERD over sensorimotor regions representing the stimulus side was elicited by both types of precues approximately 200 ms after their onset. For contralateral precues, a switch of beta ERD to the response hemisphere took place approximately 400 ms after trial-onset, peaking prior to the imperative stimulus (approximately 800 ms post trial-onset). Signal subspace projection demonstrated a high topographical correspondence between the early precue-related ERD and the pattern immediately preceding the response, suggesting that both were generated in similar motor networks. Apparently lateralized sounds give rise to an early activation of contralateral motor networks independent of the precued response. This suggests strong associations between space processing and action preparation networks, with fast activations preceding a detailed cortical analysis of stimulus meaning.
On immobile rats it has been shown that subcuteneous injection of two different neuropeptides causes different distribution of activating, inhibiting and areactive cells resulting from microionoforetically administrated acetylcholine and noradrenaline without altering the mean frequency of the background unit activity sensorimotor cortical neurons. At the same time the alteration in the pattern of neurons impulse activity has been revealed, which acquires the character of packet activity with a specific packet length of 2-3, 4-6, 7-10 impulses. Depending on the injected neuropeptide reliable but almost contrary effects of the packet activity alterations have been observed. These effects have been suggested to result from the alteration of the chemoreactive properties of the neuron membranes and the corresponding reorganisations of interneuron attitudes.
Five patients with left striatocapsular infarction were studied twice with PET during auditory-cued right thumb-index tapping, around 2 months after stroke and again around 8 months after stroke. At PET1 and PET2, the ipsilesional primary sensorimotor (SM1) activation peak Talairach coordinates were compared to those from seven aged-matched healthy controls. At PET1, there was a significant posterior displacement of SM1 activation peak, which confirms a previous report and may represent unmasking/disinhibition of motor representations. Over time, there was no significant change in the coordinates, and no significant correlation between coordinate changes from PET1 to PET2 and concomitant motor recovery. The implications of posterior displacement of SM1 activation peak for recovery therefore remain elusive.
Neurohumoral disorders in mothers caused by brain injury, infection, hypoxia, and other pathological factors result in motor and psychoemotional disorders in children. Emotional behavior of 30-day-old offsprings of female rats with unilateral sensorimotor brain injury was studied in the "open field". Individual behavior was estimated (the probability of certain acts and significant transfers between them). Behavioral disorders in rat offsprings depended on the side (left of right) of mother's brain injury and "handedness". The right-side mother's injury turned to be more deleterious. Behavioral alterations were stronger in offsprings of ambidextral and left-handed females than in those born by right-handed males with the same sensorimotor injury.
Possible functional roles for glutamate that is detectable at low concentrations in the extracellular space of intact brain and brain slices have not been explored. To determine whether this endogenous glutamate acts on metabotropic glutamate receptors (mGluRs), we obtained whole cell recordings from layer V pyramidal neurons of rat sensorimotor cortical slices. Blockade of mGluRs with (+)-alpha-amino-4-carboxy-alpha-methyl-benzeacetic acid (MCPG, a general mGluR antagonist) increased the mean amplitude of spontaneous excitatory postsynaptic currents (sEPSCs), an effect attributable to a selective increase in the occurrence of large amplitude sEPSCs. 2S-2-amino-2-(1S,2S-2-carboxycyclopropyl-1-yl)-3-(xanth-9-yl)propanoic acid (LY341495, a group II antagonist) increased, but R(-)-1-amino-2,3-dihydro-1H-indene-1,5-dicarboxylic acid (AIDA) and (RS)-hexyl-HIBO (group I antagonists) decreased sEPSC amplitude, and (R,S)-alpha-cyclopropyl-4-phosphonophenylglycine (CPPG, a group III antagonist) did not change it. The change in sEPSCs elicited by MCPG, AIDA, and LY341495 was absent in tetrodotoxin, suggesting that it was action potential-dependent. The increase in sEPSCs persisted in GABA receptor antagonists, indicating that it was not due to effects on inhibitory interneurons. AIDA and (S)-3,5-dihydroxyphenylglycine (DHPG, a group I agonist) elicited positive and negative shifts in holding current, respectively. LY341495 and (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV, a group II agonist) elicited negative and positive shifts in holding current, respectively. The AIDA and LY341495 elicited currents persisted in TTX. Finally, in current clamp, LY341495 depolarized cells by approximately 2 mV and increased the number of action potentials to a given depolarizing current pulse. Thus ambient levels of glutamate tonically activate mGluRs and regulate cortical excitability.
We studied error-related processing using magnetoencephalography (MEG). Previous event-related potential studies have documented error negativity or error-related negativity after incorrect responses, with a suggested source in the anterior cingulate cortex or supplementary motor area. We compared activation elicited by correct and incorrect trials using auditory and visual choice-reaction time tasks. Source areas showing different activation patterns in correct and error conditions were mainly located in sensorimotor areas, both ipsi- and contralateral to the response, suggesting that activation of sensorimotor circuits accompanies error processing. Additional activation at various other locations suggests a distributed network of brain regions active during error-related processing. Activation specific to incorrect trials tended to occur later in MEG than EEG data, possibly indicating that EEG and MEG detect different neural networks involved in error-related processes.
Ten patients with Parkinson's disease were seen following bilateral or unilateral implantation of macroelectrodes into the subthalamic nucleus. Local field potentials (LFPs) were recorded from adjacent subthalamic nucleus macroelectrode (STNME) contacts simultaneously with EEG activity over the supplementary motor (Cz-FCz) and sensorimotor (C3/4-FC3/4) areas and EMG activity from the contralateral wrist extensors during isometric and phasic wrist movements. Significant coherence was seen between STNME LFPs and Cz-FCz, STNME LFPs and C3/4-FC3/4, and STNME LFPs and EMG over the range 7-45 Hz. EEG phase-led STNME LFPs by 24.4 ms (95% confidence interval 19.8 to 29.0 ms). EMG also led STNME LFPs, but time differences tended to cluster around one of two values: 6.3 ms (-0.7 to 13.3 ms) and 46.5 ms (26.2 to 66.8 ms). Recordings from the STNME contact that demonstrated the most consistent coherence with Cz-FCz in the 15-30 Hz band coincided with the contact which, when electrically stimulated at high frequencies, produced the most effective clinical response in eight out of nine (89%) subjects (P < 0.01). Oscillatory activity at 15-30 Hz may therefore prove of use in localizing the subthalamic nucleus target that provides the best clinical effect on stimulation. These results extend the hypothesis that coherent activity may be useful in binding together related activities in simultaneously active motor centres. The presence of coherence between EEG and STNME LFPs in both the beta and the gamma band (as opposed to only the beta band between EEG and cerebellar thalamus) suggests that there may be some relative frequency selectivity in the communication between different motor structures.
The survival of many animals hinges upon their ability to avoid collisions with other animals or objects, or to precisely control the timing of collisions. Optical expansion provides a compelling impression of object approach and in principle can provide the basis for judgments of time to collision (TTC) [1]. It has been demonstrated that pigeons [2] and houseflies [3] have neural systems that can initiate rapid coordinated actions on the basis of optical expansion. In the case of humans, the linkage between judgments of TTC and coordinated action has not been established at a cortical level. Using functional magnetic resonance imaging (fMRI), we identified superior-parietal and motor-cortex areas that are selectively active during perceptual TTC judgments, some of which are normally involved in producing reach-to-grasp responses. These activations could not be attributed to actual movement of participants. We demonstrate that networks involved in the computational problem of extracting TTC from expansion information have close correspondence with the sensorimotor systems that would be involved in preparing a timed motor response, such as catching a ball or avoiding collision.
OBJECTIVES: To investigate the physiologic mechanism of human electroencephalogram-electromyogram (EEG-EMG) coherence, the directed transfer function (DTF) based on a multivariate autoregressive (MVAR) model was computed. METHODS: Fifty-six channel EEG and EMG of the right abductor pollicis brevis muscle during a weak tonic contraction were recorded in 6 normal volunteers. The EEG over the left sensorimotor area and the rectified EMG were used to compute coherence and DTF. RESULTS: EEG-EMG coherence was observed at the peak frequency of 15-29 Hz (mean 18.5 Hz). The peak frequency of DTF from EEG to EMG was 12-27 Hz (mean 17.8 Hz). DTF from EEG to EMG was significantly larger than that from EMG to EEG at 19-30 and 45-50 Hz (P<0.05). CONCLUSIONS: The present findings suggest that the EEG-EMG coupling mechanism for the 19 Hz or higher frequency might differ from that for the lower frequency. Directional information flow from EEG to EMG in the former frequency range likely reflects the motor control command. The finding of the directional information flow from EEG to EMG within the gamma band indicates that 40 Hz EEG-EMG coherence is not specific to the muscle Piper rhythm which is seen only with strong contraction.
1. In order to ascertain whether both GABA(A) and GABA(B), or only GABA(B) receptors, directly modulate thermoregulation in conscious rabbits, GABA(A)/GABA(B) agonist and antagonist agents were injected intracerebroventricularly in conscious rabbits while monitoring changes in rectal temperature (RT), gross motor behaviour (GMB) and electrocorticogram (ECoG) power spectra (ps) from sensorimotor cortices. 2. GABA (48 micromol), nipecotic acid (50 nmol), THIP (60 nmol), muscimol (18 nmol) and baclofen (8 nmol) induced hypothermia (-deltaRTmax values of 1.70+/-0.1, 1.4+/-0.2, 1.0+/-0.4, 1.1+/-0.2 and 1.6+/-0.3 degrees C, respectively), accompanied by inhibition of GMB and ECoG synchronization. THIP increased ps at delta frequency band (1.1-3.3 Hz), while GABA, nipecotic acid, muscimol and baclofen did the same at both delta and (4.6-6.5 Hz) frequency bands. ECoG ps changes were concomitant or even preceded hypothermia. 3. Bicuculline (1.8 nmol) induced hyperthermia (deltaRTmax 1.2+/-0.5 degrees C) and slight excitation of GMB, while CGP35348 (1.2 micromol) did not affect RT nor GMB. Both compounds did not affect ECoG ps. 4. Bicuculline potentiated muscimol-induced hypothermia, inhibition of GMB and synchronization of ECoG, while CGP35348 fully antagonized these effects. 5. In conclusion, the present results, while confirming the prevailing role of GABA(B), also outline a direct involvement of GABA(A) receptors in the central mechanisms of thermoregulation. Ascending inhibition towards discrete cortical areas controlling muscular activity and thermogenesis may result from GABA receptor activation in neurones proximal to the ventricles, thus contributing to hypothermia, although hypothermia-induced reduction of neuronal activity of these cortical areas cannot be ruled out.
Previous neuroimaging studies have suggested that patients with schizophrenia fail to recruit appropriate focal patterns of cortical responses to cognitive tasks. We investigated whether patients with schizophrenia show a normal focal response to a simple motor task. Seven strongly right-handed patients with schizophrenia and seven strongly right-handed normal subjects performed motor tasks of increasing complexity. Patients were unable to recruit as focal a response even to a simple, automatic sequential finger movement task. They showed greater ipsilateral activation in the primary sensorimotor and lateral premotor regions and had a significantly lower laterality quotient than normal subjects. These phenomena increased with the complexity of the task. These results demonstrate a functional disturbance in the cortical motor circuitry of patients with schizophrenia.