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Biomedical subjects

M Inghilleri

Publications and source records attributed to M Inghilleri.

At least 73 records · Page 4Linked to original sources
PubMed1991

Corticospinal potentials after electrical and magnetic stimulation in man.

The present report deals with our study of the descending volley evoked by both electrical and magnetic transcranial stimulation in man. We discuss the differences of these two techniques specifically as regards the latency and amplitude of evoked potentials. In both cases, electrodes were placed either in the epidural space or directly on the spinal cord. Following electrical stimulation, the descending volley consisted of an early wave which appeared at low stimulation intensity and increased in amplitude and decreased in latency when the strength of the stimulus was increased. At high stimulation intensities the early wave was followed by later waves which travel at the same speed as the initial wave. By delivering paired cortical stimuli, the early wave evoked by the test stimuli is present at 1-msec interval and progressively recovered with longer intervals. The recovery cycle of the later waves is also extremely short. Following magnetic stimulation, the descending volley also consisted of an initial wave followed by later waves. The initial wave has a slightly longer latency, a higher threshold and a smaller amplitude than the early wave evoked by electrical stimulation. The results are discussed with reference to the D and I waves recorded from the pyramidal tract in animals.

Adult↗
PubMed1990

Corticobulbar projections to upper and lower facial motoneurons. A study by magnetic transcranial stimulation in man.

To investigate the human corticofacial projections, we recorded the compound motor potentials and single motor unit potentials evoked by magnetic transcranial stimulation, in the frontalis and lower facial muscles of healthy subjects. Potentials secondary to activation of the corticobulbar tract were contralateral in lower and bilateral in upper facial muscles. Even though the latency of responses was longer than would be expected for direct cortico-motoneuronal connections, these cannot be excluded either for lower or upper facial motoneurons.

Adult↗
PubMed1990

Descending volley after electrical and magnetic transcranial stimulation in man.

The descending volley evoked by electrical and magnetic transcranial stimulation was recorded with spinal electrodes in 3 subjects undergoing spinal surgery. The descending volley evoked by electrical stimulation, as previously described, was composed by a short-latency initial wave followed by later waves. In two subjects magnetic stimulation evoked an initial wave of slightly longer latency (0.2-0.3 ms), smaller amplitude and higher threshold than the initial wave evoked by electrical stimulation. In these two subjects, magnetic stimuli probably activated the pyramidal axons directly. In the third subject the initial wave evoked by magnetic stimulation had a latency of 1.4 ms longer and a considerably smaller amplitude than that evoked by electrical stimulation. In this case magnetic stimulation may activate the pyramidal axons indirectly.

Action Potentials↗
PubMed1989

The masseter inhibitory reflex is evoked by innocuous stimuli and mediated by A beta afferent fibres.

Mechanical or electrical stimulations in the area of the mouth evoke two phases of inhibition in the masseter muscle (early and late inhibitory reflex, also called masseter silent periods). The question whether the afferents of the human masseter inhibitory reflex are nociceptive or non-nociceptive has not yet been settled. We showed that an innocuous stimulus, such as a fine jet of saline directed to the lips of healthy humans, evokes an early and a late masseter inhibitory reflex, similar to those following electrical stimulation. We measured the efferent and afferent delay of the masseter early inhibitory reflex in patients submitted to intracranial stimulation of the motor and sensory trigeminal root, and found that the reflex afferents belong to the intermediately-fast conducting fibre group.

Afferent Pathways↗
PubMed1989

Functional organization of the trigeminal motor system in man. A neurophysiological study.

Transcranial stimulation (TCS) in intact human subjects was used to investigate the corticobulbar projections and the functional organization of the trigeminal motor system. Both electrical (with the anode overlying the face area of the motor cortex) and magnetic TCS (with the coil at the vertex) excite the upper motoneurons projecting to the trigeminal motor nucleus, evoking motor potentials (C-MEPs) in the jaw-closing and suprahyoid muscles, but only during voluntary contraction. At least 30% of jaw-closing motoneurons are reached by direct fast-conducting corticobulbar fibres; these projections are mainly crossed. Suprahyoid motoneurons are also reached by fast-conducting corticobulbar fibres; these projections are probably bilateral. In the masseter, electrical TCS also evokes an ipsilateral motor response (R-MEP), followed by a later wave (U), and bilateral inhibitory periods. The R-MEP is secondary to excitation of the motor trigeminal root; the U wave probably results from the simultaneous excitation of Ia afferents in the root and ipsilaterally projecting corticofugal fibres; the inhibitory periods are largely due to activation of exteroceptive afferents in the root. Magnetic TCS, avoiding spread of current to the trigeminal root, evokes C-MEPs but not R-MEPs or U waves. The masseter inhibitory period after magnetic TCS may be due to excitation of corticofugal inhibitory fibres and to mechanical activation of Golgi tendon organs.

Adolescent↗
PubMed1989

Corticospinal potentials after transcranial stimulation in humans.

The descending volley evoked in humans by transcranial electrical stimulation of the scalp was recorded with epidural and spinal electrodes. It consisted of an early wave, which increased in amplitude and decreased in latency when the strength of the stimulus was increased. The mean conduction velocity of the early wave was 66, SD 2.5 m/s. At high stimulus intensity this wave was followed by later and smaller waves, which travel at the same speed as the initial potential. The recovery cycle of the descending volley was studied by delivering paired cortical stimuli at time intervals ranging from 0.5 to 10 ms. The early wave evoked by the test stimulus recovered to about 50% at a 1 ms interval and to 100% at a 3.5 ms interval. The later waves could not be tested at short time intervals but with time intervals longer than 3.5 ms they recovered to 100%. It is suggested that the initial and later waves after scalp stimulation are equivalent to the D and I waves seen in animal experiments.

Adult↗
PubMed1988

Stimulation of motor tracts in multiple sclerosis.

Percutaneous electrical stimulation of the motor cortex was used to evaluate corticospinal conduction to upper-limb motoneurons in 29 patients with multiple sclerosis. Central motor conduction abnormalities were correlated with clinical signs and somatosensory evoked potentials. Muscle responses to cortical stimulation were altered in 20 patients. The most common abnormality was increased central motor conduction time; in two cases the responses to cortical stimulation were absent. Abnormalities were also present in patients with no clinical evidence of corticomotoneuron deficit. Alterations of muscle responses and of somatosensory evoked potentials were usually correlated, but may appear independently. Both testing methods are useful in the study of patients with multiple sclerosis.

Adult↗
PubMed1987

The 'foramen ovale electrode': a safe tool to study temporal lobe epilepsy.

Following the description by Wieser et al. (1985) of the use of a foramen ovale electrode to record from mesial temporal structures the authors describe an alternative electrode equipped with radial tines to make it self-retaining. A helical section provides flexibility along the electrode's longitudinal axis preventing displacement of the tip during jaw movements. Clinical and detailed neurophysiological examinations failed to demonstrate any evidence of motor or sensory trigeminal nerve dysfunction and no complications were encountered.

Electrodes, Implanted↗
PubMed1987

Intracranial stimulation of the trigeminal nerve in man. III. Sensory potentials.

Percutaneous electrical stimulation of the trigeminal root was performed in 18 subjects undergoing surgery for idiopathic trigeminal neuralgia or implantation of electrodes into Meckel's cave for recording of limbic epileptic activity. All subjects had normal trigeminal reflexes and evoked potentials. Sensory action potentials were recorded antidromically from the supraorbital (V1), infraorbital (V2) and mental (V3) nerves. In the awake subject, sensory potentials were usually followed by myogenic artifacts due to direct activation of masticatory muscles or reflex activation of facial muscles. In the anaesthetised and curarised subject, sensory potentials from the three nerves showed 1.4-2.2 ms onset latency, 1.9-2.7 ms peak latency and 17-29 microV amplitude. Sensory conduction velocity was computed at the onset latency (maximum CV) and at the peak latency (peak CV). On average, maximum and peak CV were 52 and 39 m/s for V1, 54 and 42 m/s for V2 and 54 and 44 m/s for V3. There was no apparent difference in CV between subjects with trigeminal neuralgia and those with epilepsy. A significant inverse correlation was found between CV and age, the overall maximum CV declining from 59 m/s (16 years) to 49 m/s (73 years). This range of CV is compatible both with histometric data and previous electrophysiological findings on trigeminal nerve conduction. Intraoperative intracranial stimulation is also proposed as a method of monitoring trigeminal function under general anaesthesia.

Action Potentials↗
PubMed1987

Stimulation of motor tracts in motor neuron disease.

The muscle responses evoked by cortical and cervical stimulation in 11 patients with motor neuron disease were studied. The muscle potential in the abductor pollicis brevis, evoked by median nerve stimulation and the somatosensory potential evoked by wrist stimulation were also studied. In eight of 11 patients there was absence or increased central delay of the responses evoked by cortical stimulation. In four patients muscle responses on cervical stimulation and muscle action potentials on median nerve stimulation were also altered, indicating peripheral abnormalities. Somatosensory responses evoked by wrist stimulation were normal. Electrophysiological techniques are helpful in estimating the site of motor involvement in motor neuron disease.

Action Potentials↗
PubMed1987

Cortical and cervical stimulation after hemispheric infarction.

Cortical and cervical stimulation has been performed in 20 patients with hemiparesis or hemiplegia due to hemispheric infarction and in 20 control subjects. The motor action potentials (MAPs) were recorded from biceps and thenar muscles. MAPs evoked by stimulation of the undamaged hemisphere were normal in 18 out of 20 patients and in two there was a slight increase of central conduction time (CCT). The stimulation of the motor cortex of the damaged hemisphere did not evoke any response in 15 patients; in two the MAPs were absent in one muscle and in the remaining three were delayed in one or both muscles. Cervical MAPs were normal in 18 patients and delayed in the thenar muscle in two patients.

Action Potentials↗
PubMed1987

Neurophysiologic assessment of trigeminal function after surgery for trigeminal neuralgia.

To assess the function of the three trigeminal divisions, we studied corneal reflex, early and late blink reflexes, early and late masseter silent periods, and jaw jerk in normal subjects and in 35 patients submitted to surgery for trigeminal neuralgia. The corneal reflex was most sensitive to thermocoagulation and the jaw jerk to microcompression; the other reflexes showed an intermediate behavior, depending on afferent fiber size. Trigeminal function was less impaired after microcompression and recovered earlier than after thermocoagulation.

Adult↗
PubMed1984

Recovery cycle of the masseter inhibitory reflex in man.

The masseter inhibitory reflex from stimulation of the mental nerve has been recorded electromyographically in 10 healthy subjects. The recovery cycle of the two silent periods interrupting the tonic contraction of the masseter muscles have been studied with the paired shock technique. There was a clear dissociation between the recovery of early and late inhibition, the latter being far more affected by a preceding impulse. It is concluded that the two silent periods are mediated by separate neural nets. The differences with the recovery curves of the two components of the blink reflex are discussed.

Adult↗