PubMed Health⌕ Search

Biomedical subjects

E Favale

Publications and source records attributed to E Favale.

At least 73 records · Page 4Linked to original sources
PubMed1981

Conducted and segmental components of the somatosensory cervical response.

Cervical responses evoked by stimulation of the median nerve have been concurrently recorded from C7--Fz and C7--Sn (suprasternal notch). The existence of two different waveforms (RI and RII) has been confirmed. RI (from C7--Fz) consists of four negative peaks (N9, N11, N13, N14) followed by a large positive deflection (P16). RII (from C7--Sn) is characterised by an early positive--negative spike (P1--N1a) followed by a slow negative--positive wave (N1b--P2). The study of the most relevant parameters (polarity, latency and refractory period) of each component of RI and RII did not indicate whether the generators underlying RI differ from those responsible for RII. However, stimulation of the lower limb, which does not involve segmental events at cervical level, showed a clearcut difference: no response was recorded from C7--Sn, while evoked activity equivalent to RI was obtained from C7--Fz. Therefore it is suggested that RII is entirely generated by segmentally evoked potentials while RI is mainly due to conducted potentials.

Adult↗
PubMed1980

Conduction time of the lemniscal pathway in males and females.

The central conduction time of the lemniscal pathway is not statistically different in the two sexes, while the peak latencies of both S13 and N20 components are significantly longer in males than in females. However, multivariate analysis of covariance of data showed that such a result is not related to sex, but to the difference in height between the two sexes.

Adult↗
PubMed1980

The effect of hand muscle vibration on the somatosensory evoked potential in man: an interaction between lemniscal and spinocerebellar inputs?

The effect of hand muscle mechanical vibration on the somatosensory potential (SEP) evoked by median nerve stimulation, was investigated in 10 healthy subjects. A marked decrease in the amplitude of the N17, N20 and P25 components of the cerebral SEP was observed, while the S11 and S13 components of the cervical response did not change. The amplitude reduction of the SEP components was larger when low frequency vibration was used. Recordings performed after cooling the hand further suggest that the reduction of the amplitude of the SEP components induced by vibration is likely to depend on activation of muscle receptors. These findings could reflect an interaction between limniscal and spino-cerebellar inputs, possibly occurring at the thalamo-cortical levels, a concept compatible with the hypothesis that muscle spindle afferents do contribute to kinaesthesia or position-sense.

Adult↗
PubMed1979

Visual reaction time as a function of locus, area, and complexity of stimulus.

Reaction time (RT) of normal subjects to square-wave gratings of two different frequencies were related to locus of presentation, area, and stimulus complexity. Each frequency was presented to either side of the horizontal meridian (half size stimulus) or both sides stimultaneously (full size stimulus). The two different frequencies were also flashed simultaneously to both hemifields (compound stimulus). Stimulus position affected RT with the 1 c/deg stimulus, RT being faster for the lower hemifield. With presentation on both sides of the horizontal median simultaneously or of the two spatial frequencies, the resulting RT was equal to that of the faster component. Implications of the results for the functional organization of the visual system are discussed.

Female↗
PubMed1979

[Further research on the functional asymmetry between the superior and inferior visual hemifields: analysis of the reaction time to simultaneous stimulation of the two hemi-fields].

It has been previously reported that presentation of square-wave gratings to either side of the horizontal meridian of the visual field gives rise to different Simple Reaction Times (RTs), depending upon the spatial frequency of the stimuli. Specifically, for 1 c/deg stimulus RT is faster in the lower hemefield, whereas the reverse is true for 3 c/deg pattern, RT being faster in the upper visual field. In the reported experiment, RT to simultaneous presentation of either the same (alternatively 1 c/deg or 3 c/deg) or different (i.e. 1 c/deg and 3 c/deg combined) spatial frequencies to both hemifields was analyzed. The data show that whenever the two half components correspond to different RTs, the resulting RT equates that of the faster component. Conversely, when the two components give rise to identical RTs, the resulting RT does not differ from the value obtained with each half stimulus. Implications of this result for the functional organization of the visual system are discussed.

Adult↗
PubMed1979

[Further observations on the "primary" somesthetic response in man. Preliminary results].

In six normal subjects cerebral somatosensory potentials evoked by median nerve stimulation at the wrist have been recorded in order to assess whether N20 and P25 components can be related to a single generator dipole. It was found that, at variance with the current literature, such components are due to separate generator dipoles, possibly related to the activity of different cortical structures. Moreover an additional component, chronologically occurring between N20 and P25, was consistently observed.

Electric Stimulation↗
PubMed1979

Ortho-antidromic latency fitting and identification of antidromically activated CNS long-axoned neurones.

The intrinsic errors of the collision test were evaluated in extracellular recordings of cat's pyramidal tract (PT)-units. A modified collision technique by means of paired and suitably timed PT-stimuli allowed the demonstration of the ortho-antidromic latency fitting. This method could represent an important counterproof to the true antidromic activation of CNS long-aconed neurons.

Action Potentials↗
PubMed1979

Tonic vibration reflex in Holmes-Adie syndrome: an electrophysiological study.

The pathophysiological mechanisms underlying benign areflexia were studied in six patients with Holmes-Adie syndrome. No impairment of sensory conduction velocity of sural nerve was found. A normal tonic vibration reflex was obtained in all patients. H reflex was absent in five patients, but responses like F waves were recorded in three subjects. These findings suggest that muscle spindles are not affected and that spinal motoneurone excitability is normal.

Adie Syndrome↗
PubMed1979

[Neuro-ophthalmological problems: the diagnostic value of contrast sensitivity].

The evaluation of the individual contrast sensitivity function may prove useful in cases affected by lesions of the optic pathways, even when the usual neuro-ophthalmological tests (i.e. visual acuity, visual field examination) are normal. The contrast sensitivity function represents an alternative method to assess the power of spatial resolution of the visual system: in particular, it enables to measure the sensitivity at high, medium and low ranges of spatial frequencies, this being unique to such a procedure. The possible physiological mechanisms underlying the contrast sensitivity function as well as its pathological changes are reviewed.

Form Perception↗
PubMed1978

Spinal components of the cerebral somatosensory evoked response in normal man: the "S wave".

Responses evoked over the scalp and the neck by median nerve (or finger I) stimulation were concurrently recorded in 10 subjects. It was found that the first component of the cortical SEP consists of a small amplitude polyphasic wave (S wave) which could be recorded bilaterally upon unilateral stimulation. The polarity of the S wave varied according to the reference electrode position, at variance with the P15 component which remained constantly positive. It is therefore correct to assume that different generators are responsible for these two potentials. The synchrony between the S wave and the cervical response, which is largely spinal in origin, as well as some pertinent experimental data, suggest that the S wave is a far field reflection of activity generated mainly in the cervical dorsal columns. These findings might be relevant to the diagnosis of neurological disorders.

Adult↗
PubMed1978

New subcortical components of the cerebral somatosensory evoked potential in man.

Two new components of the human SEP upon stimulation of the contralateral median nerve at the wrist have been identified. Such components have been called N16 and N17, according to their polarity and latency. N16 and N17, as well as the N14-P15 complex, are generated by separate subcortical dipoles. Particularly, they are supposed to be far-field reflections of the activity of the dorsal columns nuclei or the medial lemniscus (N14-P15), the thalamus (N16) and the thalamo-cortical radiation (N17). Moreover, it has been established that N14 is the very first intracranial component of the human SEP, the main peak of S wave and the preceding ones being extracranial in origin. A new classification of SEP intracranial components including early (N14 through N17), intermediate (N20 through P30) and late events is proposed.

Adult↗