PMID- 11068233
OWN - NLM
STAT- MEDLINE
DCOM- 20010111
LR  - 20190921
IS  - 1388-2457 (Print)
IS  - 1388-2457 (Linking)
VI  - 111
IP  - 11
DP  - 2000 Nov
TI  - Effects of a photic input on the human cortico-motoneuron connection.
PG  - 1981-9
AB  - OBJECTIVES: Disease manifestations such as photic cortical reflex myoclonus or 
      myoclonus due to intermittent light stimulation rely on a pathologic interaction 
      between non-structured visual inputs and the corticospinal system. We wanted to 
      assess the normal interaction, if any, between a prior photic input and the 
      output of the cortico-motoneuron connection. METHODS: In 9 consenting healthy 
      subjects we quantified the changes exerted by a sudden, unexpected bright light 
      flash on (i) the motor potentials (MEPs) evoked in the right first dorsal 
      interosseous muscle (FDI) by transcranial magnetic or electrical stimulation 
      (TMS/TES) of the primary motor cortex, (ii) the FDI F-waves and (iii) the soleus 
      H-wave. Separately, we measured the simple reaction times to the flash itself. 
      All determinations were repeated twice with an interval of 2-24 months. RESULTS: 
      When the flash preceded TMS by 55-70 ms, the MEP size was reduced, while at 
      interstimulus intervals (ISIs) of 90-130 ms it was enlarged. Statistical 
      significance (P<0.05) emerged at ISIs of 55, 70, 100, 105 and 120 ms. Conversely, 
      the MEP latency was prolonged at ISIs of 55-70 ms and shortened at ISIs of 90-130 
      ms (P<0.05 at ISIs of 55, 110 and 130 ms). Electrical MEPs were enhanced at an 
      ISI of 120 ms. The F-wave size showed a non-significant trend of enhancement at 
      ISIs of 90-130 ms. The soleus H-wave showed significant enlargement at ISIs of 
      90-130 ms (P<0.05 at ISIs of 100 and 105 ms). The minimum reaction time was on 
      average 120 ms. CONCLUSIONS: An unexpected photic input, to which no reaction is 
      planned, can cause an early inhibition of the responses to TMS. We think its 
      origin lies within the primary motor cortex, since it is not associated with 
      changes in spinal excitability or electrical MEPs. A later facilitation persists 
      using TES and has a temporal relationship with an enlargement of the soleus 
      H-wave. Thus, it likely results from activation of descending (possibly 
      reticulospinal) fibers that excite the spinal motor nucleus.
FAU - Cantello, R
AU  - Cantello R
AD  - Department of Medical Sciences, Section of Neurology, Universita del Piemonte 
      Orientale "Amedeo Avogadro", Novara, Italy. cantello@med.unipmn.it
FAU - Civardi, C
AU  - Civardi C
FAU - Cavalli, A
AU  - Cavalli A
FAU - Varrasi, C
AU  - Varrasi C
FAU - Vicentini, R
AU  - Vicentini R
LA  - eng
PT  - Journal Article
PL  - Netherlands
TA  - Clin Neurophysiol
JT  - Clinical neurophysiology : official journal of the International Federation of 
      Clinical Neurophysiology
JID - 100883319
SB  - IM
MH  - Adult
MH  - Brain/*physiology
MH  - Electric Stimulation
MH  - Evoked Potentials, Motor/*physiology
MH  - Female
MH  - Humans
MH  - Male
MH  - Muscles/physiology
MH  - *Photic Stimulation
MH  - Reaction Time/physiology
MH  - Reference Values
EDAT- 2000/11/09 11:00
MHDA- 2001/02/28 10:01
CRDT- 2000/11/09 11:00
PHST- 2000/11/09 11:00 [pubmed]
PHST- 2001/02/28 10:01 [medline]
PHST- 2000/11/09 11:00 [entrez]
AID - S1388-2457(00)00431-4 [pii]
AID - 10.1016/s1388-2457(00)00431-4 [doi]
PST - ppublish
SO  - Clin Neurophysiol. 2000 Nov;111(11):1981-9. doi: 10.1016/s1388-2457(00)00431-4.