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PubMed1995

Super-early iodine-123-iodoamphetamine SPECT imaging of human primary motor cortex.

UNLABELLED: This study was designed to visualize the motor function area related to finger movements in normal human brain using super-early (first 640 sec of acquisition) [123l]iodoamphetamine ([123I]IMP) SPECT. METHODS: Seven healthy male volunteers performed paired, isolated baseline and task sessions. The task was a right thumb-to-fingers opposition task, which was loaded for the initial 11 min of the session. A high-performance, four-head SPECT camera was used. At each session, administration of 222 MBq [123I]IMP was followed by 16 serial 160-sec dynamic SPECT acquisitions. To obtain matched brain anatomical images, MRI was also performed using the same slice formation as in the SPECT study. After image reconstruction, ROIs were set on bilateral sensorimotor hand areas (SMHA), the supplementary motor area (SMA), the frontal, temporal and occipital lobes and the cerebellar hemispheres. The percent increase of ROI activity (%INC) in the task session compared with that in the baseline session was calculated in each ROI after normalization to the global brain radioactivity. RESULTS: There was significant activation of the left SMHA by the task, the amplitude of which was maximal in the initial phase of dynamic images (the super-early phase). This area was located in the left peri-central area identified on the analogous slice in the MR image. The left SMHA showed gradual and statistically significant decrease of %INC during the three phases. CONCLUSION: Super-early [123I]IMP may be used to identify the primary motor cortex and to evaluate its function in some pathological conditions.

Adult↗
PubMed1976

[Neuron activities of the motor cortex during conditioned eye blink reflex in rabbits (author's transl)].

Effects of the tone (CS) on neurons of the motor cortex were investigated in naive, pseudoconditioned, and conditioned rabbits. Conditioning to eye blink reflex was made by a combination of CS and air puff (US). Effects of electrical stimulation of the subcortical structures were also observed on the cortical neurons associated with the conditioned reflex. The results were as follows. (1) Proportion of neurons which significantly increased the firing rate in response to the CS, type E, was higher in the conditioned group than in other two groups. On the other hand, no group difference was found in the proportion of neurons which significantly decreased the firing rate to the stimulus, type I. (2) Most of the type E neurons in the conditioned rabbits began to fire at latencies of about 50 to 100 msec after the CS, preceding about 200 msec to the appearance of the peripheral conditioned responses (EMG). (3) Most of the type E neurons in the conditioned animals were more easily affected by stimulation of the medial geniculate body and the brain stem reticular formation. Based on the results mentioned above, it is concluded that in the rabbits conditioned to the eye blink reflex, excitability of neurons in the motor cortex is enhanced by the tone (CS), and by electrical stimulation to the medial geniculate body and the brain stem reticular formation.

Action Potentials↗
PubMedDate not supplied

[Role of different projection areas of the motor cortex in reorganization of the innate head-forelimb coordination in dogs].

Dogs were trained to perform the forelimb tonic flexion in order to lift a cup with meat from a bottom of the foodwell and hold it during eating with the head bent down to the cup. It is known that conditioning of the instrumental reaction is based on reorganization of the innate head-forelimb coordination into the opposite one. In untrained dogs, the forelimb flexion is accompanied by the anticipatory lifting of the head bent down to the foodwell. The following lowering of the head leads to an extension of the flexed forelimb. Tonic forelimb flexion is possible if the head is in the up position. Simultaneous holding of the flexed forelimb and lowered head providing food reinforcement is achieved only by learning. It was shown earlier that the lesion of the motor cortex contralateral to the "working" forelimb led to a prolonged disturbance of the elaborated coordination and reappearance of the innate coordination. In the present work we studied the influence of local lesions of the projection areas in the motor cortex, such as a "working" forelimb area, bilateral representation of the neck, and the medial part of the motor cortex, on the learned instrumental feeding reaction. It was found that only the lesion of the forelimb but not neck projection led to a disturbance of the learned head-forelimb movement coordination.

Animals↗
PubMedDate not supplied

[Motor cortex stimulation in the central pain syndrome].

We present a case of a 45-year-old male, treated with motor cortex stimulation (MCS). The procedure was performed in order to decrease symptoms of the central pain syndrome (CPS), which developed seven years earlier, after a left-side, cerebellum and brainstem ischemic stroke. The syndrome is defined as pain due to primary damage or dysfunction of the central nervous system. The pain was not sensitive to pharmacological and previous surgical interventions. During four months of follow-up after surgery with the use of MCS, 20% reduction of pain (Visual Analog Scale), withdrawal of narcotic and decrease of non-narcotic medications, ability to introduce rehabilitation and improvement of sleep were observed. No side effects were noticed. The procedure of electrode implantation to motor cortex is a relatively new treatment option in refractory central and neuropathic pain syndromes. The number of described procedures does not exceed 500 worldwide. The presented case is to our knowledge the first procedure of its type in Poland, giving hope to CPS patients, whose symptoms are otherwise difficult to treat.

Cerebral Infarction↗
PubMed2006

Anodal vs cathodal stimulation of motor cortex: a modeling study.

OBJECTIVE: To explore the effects of electrical stimulation performed by an anode, a cathode or a bipole positioned over the motor cortex for chronic pain management. METHODS: A realistic 3D volume conductor model of the human precentral gyrus (motor cortex) was used to calculate the stimulus-induced electrical field. The subsequent response of neural elements in the precentral gyrus and in the anterior wall and lip of the central sulcus was simulated using compartmental neuron models including the axon, soma and dendritic trunk. RESULTS: While neural elements perpendicular to the electrode surface are preferentially excited by anodal stimulation, cathodal stimulation excites those with a direction component parallel to its surface. When stimulating bipolarly, the excitation of neural elements parallel to the bipole axis is additionally facilitated. The polarity of the contact over the precentral gyrus determines the predominant response. Inclusion of the soma-dendritic model generally reduces the excitation threshold as compared to simple axon model. CONCLUSIONS: Electrode polarity and electrode position over the precentral gyrus and central sulcus have a large and distinct influence on the response of cortical neural elements to stimuli. SIGNIFICANCE: Modeling studies like this can help to identify the effects of electrical stimulation on cortical neural tissue, elucidate mechanisms of action and ultimately to optimize the therapy.

Axons↗
PubMed2004

Mapping from motor cortex to biceps and triceps altered by elbow angle.

This experiment used cortical microstimulation to probe the mapping from primary motor cortex to the biceps and triceps muscles of the arm in monkeys. The mapping appeared to change depending on the angle at which the elbow was fixed. For sites in the dorsal part of the arm and hand representation, the effects of stimulation were consistent with initiating a movement of the elbow to an extended angle. Stimulation evoked more triceps activity than biceps activity, and this difference was largest when the elbow was fixed in a flexed angle. For sites in the ventral part of the arm and hand representation, stimulation had the opposite effect, consistent with initiating a movement of the elbow to a flexed angle. For these sites, stimulation evoked more biceps activity than triceps activity, and the difference was largest when the elbow was fixed in an extended angle. For sites located in intermediate positions, stimulation evoked an intermediate effect consistent with initiating a movement of the elbow to a middle, partially flexed angle. For these sites, when the elbow was fixed at a flexed angle, the evoked activity was largest in the triceps, and when the elbow was fixed at an extended angle, the evoked activity was largest in the biceps. These effects were obtained with 400-ms-long trains of biphasic pulses presented at 200 Hz and 30 microA. They were also obtained by averaging the effects of individual, 30-microA pulses presented at 15 Hz. How this stimulation-evoked topography relates to the normal function of motor cortex is not yet clear. One hypothesis is that these results reflect a cortical map of desired joint angle.

Animals↗
PubMed1964

POSTSYNAPTIC POTENTIALS AND SPIKE PATTERNS DURING AUGMENTING RESPONSES IN CAT'S MOTOR CORTEX.

Intracellular recordings and electroencephalograms were obtained from neurons of the motor cortex during augmnenting responses elicited by repetitive stimulation of its specific thalamic nucleus. The postsynaptic potentials during fully developed augmenting responses consistedf two depolarizing waves with two separate groups of spike dicharges of different latencies, the bases of the spikes, the so-called "firing-levels," sometimes shifting. This supports the concept that the postsynaptic potentials accompanying the augmentintg response consist of a primary response and a response of recruiting character.

Cats↗
PubMed2003

Peripheral nerve injury influences the disinhibition induced by focal ischaemia in the rat motor cortex.

Photothrombotic lesions were produced in the rat primary motor cortex, and the brain excitability was assessed in a paired-pulse stimulation protocol by transcranial recording, in parallel at 16 points of the frontal cortex, including the insulted and the surrounding areas. The cortical lesion reduced the inhibition in the extended frontal cortex, with a delay of a few minutes. Unilateral facial nerve transection, however, accelerated the widespread disinhibition. Although the mechanism is not clear in detail, both peripheral and central injury-induced disinhibition may have a significant impact on the recovery of the function.

Animals↗
PubMed1996

Mental transformations in the motor cortex.

The behavioral and neural correlates of processing of motor directional information are described for two visuomotor tasks: mental rotation and context-recall. Psychological studies with human subjects suggested that these two tasks involve different time-consuming processes of directional information. Analyses of the activity of single cells and neuronal populations in the motor cortex of behaving monkeys performing in the same tasks provided direct insight into the neural mechanisms involved and confirmed their different nature. In the mental rotation task the patterns of neuronal activity revealed a rotation of the intended direction of movement. In contrast, in the context-recall task the patterns of neural activity identified a switching process of the intended direction of movement.

Cues↗
PubMed1999

Central regulation of motor cortex neuronal responses to forelimb nerve inputs during precision walking in the cat.

1. The responses of neurones in forelimb motor cortex to impulse volleys evoked by single pulse electrical stimulation (at 1.5 or 2 times the threshold for most excitable nerve fibres) of the superficial radial (SR) and ulnar (UL) nerves of the contralateral forelimb were studied in awake cats both resting quietly and walking on a horizontal ladder. Nerve volley amplitude was monitored by recording the compound action potential elicited by the stimulus. 2. In the resting animal 34/82 (41%) cells yielded statistically significant responses to SR stimulation, and 20/72 (28%) responded to UL stimulation. Some responses were confined to or began with an increase in firing probability ('excitatory' responses) and others with a decrease in firing ('inhibitory' responses), typically including a brief interruption of the spike train (zero rate). Cells responding to both nerves usually yielded responses similar in type. Most (78%) response onset latencies were less than 30 ms. Responses involved the addition or subtraction of from 3.4 to 0.1 impulses stimulus-1 (most <1 impulse stimulus-1). The distribution of response sizes was continuous down to the smallest values, i.e. there was no 'gap' which would represent a clear separation into 'responsive' and 'unresponsive' categories. Responses were commonest in the lateral part of the pericruciate cortex, and commoner among pyramidal tract neurones (PTNs) than non-PTNs. 3. During ladder walking most cells generated a rhythmic step-related discharge; in assessing the size of responses to nerve stimulation (20 studied, from 13 cells) this activity was first subtracted. Response onset latencies (90% <30 ms) and durations showed little or no change. Although most cells were overall more active than during rest both 'excitatory' and 'inhibitory' responses in both PTNs and non-PTNs were often markedly reduced in large parts of the step cycle; over some (usually brief) parts responses approached or exceeded their size during rest, i.e. response size was step phase dependent. Such variations occurred without parallel change in the nerve compound action potential, nor were they correlated with the level of background firing at the time that the response was evoked. When responses to both nerves were studied in the same neurone they differed in their patterns of phase dependence. 4. The findings are interpreted as evidence for central mechanisms that, during 'skilled', cortically controlled walking, powerfully regulate the excitability of the somatic afferent paths from forelimb mechanoreceptors (including low threshold cutaneous receptors) to motor cortex. Retention (or enhancement) of responsiveness often occurred (especially for ulnar nerve) around footfall, perhaps reflecting a behavioural requirement for sensory input signalling the quality of the contact established with the restricted surface available for support.

Animals↗
PubMed1985

A reappraisal of rat motor cortex organization by intracortical microstimulation.

The organization of the motor cortex was reinvestigated with intracortical microstimulation, in light-anaesthetized (ketamine) rats. A posterolateral (PL) vibrissae area was found in addition to the rostral one, and blinks of the contralateral eyelids were elicited from a part of this PL area. Several cortical representations such as neck or tail were largely overlapping with neighbouring areas. Vegetative effects (mainly myosis and swallowing) were obtained from a medial cortical strip. Within the PL vibrissae area, a topical arrangement related to the vibrissal rows was observed, whereas in the leg areas, no individual representation of muscles could be evidenced. These results are compared with the maps previously published, and discussed in terms of specificity, musculotopy and overlapping of motor areas.

Animals↗
PubMed2004

Image-guided motor cortex stimulation in patients with central pain.

According to recent clinical data, motor cortex stimulation (MCS) is an alternative treatment for central pain syndromes. We present our minimally invasive technique of image guidance for the placement of the motor cortex-stimulating electrode and assess the clinical usefulness of both neuronavigation and vacuum headrest. Five patients suffering from central pain underwent MCS with the guidance of a frameless stereotactic system (BrainLab AG, Munich, Germany). The neuronavigation was used for identification of the precentral gyrus and accurate planning of the single burr hole. The exact location was reconfirmed by an intraoperative stimulation test. Postoperative clinical and neuroradiological evaluations were performed in each patient. The navigation system worked properly in all 5 neurosurgical cases. Determination of the placement of stimulating electrode was possible in every case. All patients obtained postoperative pain relief. No surgical complication occurred, and the postoperative course was uneventful in all patients. This preliminary experience may confirm image guidance as a useful tool for the surgery of MCS. Additionally, minimal and safe exposure can be achieved using a single burr hole and vacuum headrest.

Aged↗
PubMed1982

Amphetamine, haloperidol, and experience interact to affect rate of recovery after motor cortex injury.

Rats subjected to unilateral ablation of the motor cortex and placed on a narrow beam displayed transient contralateral paresis. An immediate and enduring acceleration of recovery was produced by a single dose of d-amphetamine given 24 hours after injury. This effect was blocked by haloperidol or by restraining the animals for 8 hours beginning immediately after amphetamine administration. A single dose of haloperidol given 24 hours after injury markedly slowed recovery. This effect was also blocked by restraining the animals.

Animals↗
PubMedDate not supplied

[The mechanisms of the formation of neuronal reactions in the cat motor cortex related to the initiation of a conditioned reflex of the placing of a limb on a support: hypothesis].

Excitatory reactions of the motor cortex neurons during initiation of the conditioned placing are supposed to be based on NMDA receptor activation. The conditions needed for the NMDA receptor-driven channels to be opened by glutamate (mainly, postsynaptic hyperpolarization neutralization), are provided by the conditioned "arousal reaction" through the augmentation of cholinergic/noradrenergic bombardment of the motor cortex neurons.

Animals↗
PubMed1991

Isoflurane-induced attenuation of motor evoked potentials caused by electrical motor cortex stimulation during surgery.

Dysfunction of spinal motor conduction during surgical procedures may not be reflected by changes in somatosensory evoked potential waveforms. A method of monitoring that allows direct and continuous assessment of motor function within the central nervous system during surgery would be useful. This paper describes one such method utilizing noninvasive electric cortical stimulation to evoke muscle activity (the motor evoked potential, or MEP) during surgery. The effect of isoflurane (superimposed on a baseline of N2O/narcotic anesthesia) on MEP's in response to cortical stimulation is specifically examined. Eight patients undergoing elective neurosurgical operations were included in the study. All patients received a background of general anesthesia and partial nondepolarizing neuromuscular blockade. The motor cortex was stimulated electrically via self-adhesive scalp electrodes. Electromyographic responses from multiple muscles were measured with subdermal electroencephalograph-type needle electrodes. Motor responses to stimulation were continually recorded on magnetic tape for off-line analysis. Once closing of the surgical incision was begun, a series of four to five stimuli of constant magnitude were applied to obtain "baseline" MEP responses. Patients were then ventilated with isoflurane for up to 8 minutes, during which time stimuli were continued every 15 to 20 seconds. Comparison was made of MEP responses for trials before, 1 minute after, and 5 minutes after the addition of isoflurane. All patients demonstrated reproducible motor responses to cortical stimulation during surgery. Addition of isoflurane [isoflurane)exp, less than or equal to 0.5%) to pre-existing anesthesia caused marked attenuation of MEP amplitudes in all patients within 5 minutes of its application, without affecting neuromuscular transmission as judged by direct peripheral nerve stimulation. It is concluded that: 1) monitoring motor system integrity and function with electric transcranial cortical stimulation during surgery is feasible when utilizing an N2O/narcotic anesthetic protocol; and 2) the quality of data obtained will likely suffer with the addition of isoflurane.

Adult↗
PubMed2006

Pregabalin exerts oppositional effects on different inhibitory circuits in human motor cortex: a double-blind, placebo-controlled transcranial magnetic stimulation study.

PURPOSE: To explore acute effects of pregabalin (PGB) on human motor cortex excitability with transcranial magnetic stimulation (TMS). METHODS: PGB, 600 mg/day, was orally administered in 19 healthy subjects twice daily in a randomized, double-blind, placebo-controlled crossover design. Several measures of motor cortex excitability were tested with single- and paired-pulse TMS. RESULTS: Mean short-interval intracortical inhibition (SICI) was reduced after PGB (74 +/- 7% of unconditioned response) compared with placebo (60 +/- 6% of unconditioned response). In contrast, mean long-interval intracortical inhibition (LICI) was increased by PGB (26 +/- 4% of unconditioned response) compared with placebo (45 +/- 8% of unconditioned response), and mean cortical silent period (CSP) showed an increase from 139 +/- 8 ms or 145 +/- 8 ms after placebo to 162 +/- 7 ms or 161 +/- 10 ms after PGB. Motor thresholds, intracortical facilitation, and corticospinal excitability were unaffected. CONCLUSIONS: The observed excitability changes with oppositional effects on SICI and LICI or CSP suggest gamma-aminobutyric acid (GABA)B-receptor activation. They are markedly distinct from those induced by gabapentin, although both PGB and gabapentin are thought to mediate their function by binding to the alpha2-delta subunit of voltage-gated calcium channels. Conversely, the TMS profile of PGB shows striking similarities with the pattern evoked by the GABA-reuptake inhibitor tiagabine.

Adult↗