Abstract
Electrical stimulation over muscle tendons produces a transient suppression of voluntary EMG activity; its onset latency is ~55 ms in the forearm extensor muscles. This phenomenon has been attributed to the activation of a polysynaptic inhibitory pathway originating from Ib afferent fibres. To clarify its origin we conducted several experiments in 10 normal healthy subjects. The EMG silence after tendon stimulation appeared at relatively high stimulus intensities (> 50 mA); conditioning cutaneous stimulation left it unchanged, and the inhibition had a short recovery cycle (50 ms). Tendon stimulation still evoked EMG suppression during an ischaemic block of fast-conducting afferents. The motor potentials evoked by transcranial magnetic stimulation of the motor cortex during the EMG silence remained almost unchanged, whereas the H reflex was strongly inhibited. Hence we conclude that tendon stimulation activities slow-conducting tendon afferents, possibly group III fibres, connected not through a polysynaptic pathway origination from Ib afferents but through an oligo- or disynaptic inhibitory circuit. The EMG suppression after tendon stimulation probably represents a dysfacilitation of the α-motor neurons due to presynaptic inhibition of Ia fibres produced by tendon afferent input to the spinal cord.
| Original language | English |
|---|---|
| Pages (from-to) | 373-380 |
| Number of pages | 8 |
| Journal | Brain |
| Volume | 121 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - Feb 1998 |
Fingerprint
Keywords
- Group III afferents
- Ia afferents
- Muscle tendon
- Presynaptic inhibition
- Silent period
ASJC Scopus subject areas
- Neuroscience(all)
Cite this
Electrical stimulation over muscle tendons in humans. Evidence favouring presynaptic inhibition of Ia fibres due to the activation of group III tendon afferents. / Priori, Alberto; Berardelli, Alfredo; Inghilleri, Maurizio; Pedace, Francesca; Giovannelli, Morena; Manfredi, Mario.
In: Brain, Vol. 121, No. 2, 02.1998, p. 373-380.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Electrical stimulation over muscle tendons in humans. Evidence favouring presynaptic inhibition of Ia fibres due to the activation of group III tendon afferents
AU - Priori, Alberto
AU - Berardelli, Alfredo
AU - Inghilleri, Maurizio
AU - Pedace, Francesca
AU - Giovannelli, Morena
AU - Manfredi, Mario
PY - 1998/2
Y1 - 1998/2
N2 - Electrical stimulation over muscle tendons produces a transient suppression of voluntary EMG activity; its onset latency is ~55 ms in the forearm extensor muscles. This phenomenon has been attributed to the activation of a polysynaptic inhibitory pathway originating from Ib afferent fibres. To clarify its origin we conducted several experiments in 10 normal healthy subjects. The EMG silence after tendon stimulation appeared at relatively high stimulus intensities (> 50 mA); conditioning cutaneous stimulation left it unchanged, and the inhibition had a short recovery cycle (50 ms). Tendon stimulation still evoked EMG suppression during an ischaemic block of fast-conducting afferents. The motor potentials evoked by transcranial magnetic stimulation of the motor cortex during the EMG silence remained almost unchanged, whereas the H reflex was strongly inhibited. Hence we conclude that tendon stimulation activities slow-conducting tendon afferents, possibly group III fibres, connected not through a polysynaptic pathway origination from Ib afferents but through an oligo- or disynaptic inhibitory circuit. The EMG suppression after tendon stimulation probably represents a dysfacilitation of the α-motor neurons due to presynaptic inhibition of Ia fibres produced by tendon afferent input to the spinal cord.
AB - Electrical stimulation over muscle tendons produces a transient suppression of voluntary EMG activity; its onset latency is ~55 ms in the forearm extensor muscles. This phenomenon has been attributed to the activation of a polysynaptic inhibitory pathway originating from Ib afferent fibres. To clarify its origin we conducted several experiments in 10 normal healthy subjects. The EMG silence after tendon stimulation appeared at relatively high stimulus intensities (> 50 mA); conditioning cutaneous stimulation left it unchanged, and the inhibition had a short recovery cycle (50 ms). Tendon stimulation still evoked EMG suppression during an ischaemic block of fast-conducting afferents. The motor potentials evoked by transcranial magnetic stimulation of the motor cortex during the EMG silence remained almost unchanged, whereas the H reflex was strongly inhibited. Hence we conclude that tendon stimulation activities slow-conducting tendon afferents, possibly group III fibres, connected not through a polysynaptic pathway origination from Ib afferents but through an oligo- or disynaptic inhibitory circuit. The EMG suppression after tendon stimulation probably represents a dysfacilitation of the α-motor neurons due to presynaptic inhibition of Ia fibres produced by tendon afferent input to the spinal cord.
KW - Group III afferents
KW - Ia afferents
KW - Muscle tendon
KW - Presynaptic inhibition
KW - Silent period
UR - http://www.scopus.com/inward/record.url?scp=0031882884&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031882884&partnerID=8YFLogxK
U2 - 10.1093/brain/121.2.373
DO - 10.1093/brain/121.2.373
M3 - Article
C2 - 9549512
AN - SCOPUS:0031882884
VL - 121
SP - 373
EP - 380
JO - Brain
JF - Brain
SN - 0006-8950
IS - 2
ER -