Cerebellar activation during leg withdrawal reflex conditioning: an fMRI study.
OBJECTIVE
The aim of the present study was to examine cerebellar areas related to conditioning of the nociceptive leg withdrawal reflex using event-related functional magnetic resonance imaging (fMRI). Because of the aversive nature of the unconditioned stimulus effects of accompanying fear conditioning were expected.


METHODS
In 20 healthy adult subjects leg withdrawal reflex conditioning was performed using a standard delay protocol during MR-scanning. Electromyographic recordings from the anterior tibial and biceps femoris muscles were used to quantify conditioned responses. Fear-related changes of heart rate were assessed.


RESULTS
In the group of all subjects a significant increase of cerebellar activation was found in the anterior and posterior vermis. In the group of subjects (n=9) who showed conditioned leg withdrawal responses cerebellar activation was more pronounced in parts of the anterior vermis, which correspond to the known leg representation. In the group of subjects (n=11) who did not develop conditioned responses cerebellar activation was more pronounced in the posterolateral hemispheres. Changes of heart rate, however, did not significantly differ between groups.


CONCLUSIONS
Results suggest that areas within the anterior vermis are involved in conditioning of the leg withdrawal response. The present results, however, do not allow to differentiate between motor performance, learning or timing-related processes. Areas in the posterior vermis and cerebellar hemispheres may be related to concomitant fear conditioning.


CONCLUSIONS
Results of the present event-related fMRI study suggest involvement of the human cerebellum in conditioning of the nociceptive leg withdrawal response.
Department of Neurology, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany.
Albena
A
Dimitrova
Florian P
FP
Kolb
Hans-Gerd
HG
Elles
Matthias
M
Maschke
Marcus
M
Gerwig
Elke
E
Gizewski
Dagmar
D
Timmann
D000328:Adult; D001245:Association Learning / Q000502:physiology; D002531:Cerebellum / Q000502:physiology*; D003213:Conditioning, Psychological / Q000502:physiology*; D004562:Electrocardiography; D004576:Electromyography; D005108:Extinction, Psychological / Q000502:physiology; D005260:Female; D006339:Heart Rate; D006801:Humans; D007866:Leg / Q000502:physiology*; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D009619:Nociceptors / Q000502:physiology; D012018:Reflex / Q000502:physiology*