[not in handout, see intranet]

Dimitrova, A., Kolb, F. P., Elles, H.-G., Maschke, M., Gerwig, M., Gizewski, E., & Timmann, D. Cerebellar activation during leg withdrawal reflex conditioning: an fMRI study. Clinical Neurophysiology, In Press, Corrected Proof Available online 2 February 2004 gif(ATHENS username and password need if outside the College and not using the VPN)  

Some brief notes and extracts are listed below.

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Fig. 1. Mean percentage CR-incidence±standard error (SE) per block of 10 paired trials: in the group of 9 subjects who developed conditioned leg withdrawal responses in the acquisition phase (CR group; black squares), and in the group of 11 subjects who did not develop conditioned responses (noCR group; open squares). Incision indicates the beginning of MR-scanning in block 6.

5. Conclusions

The present results support previous findings of involvement of the human cerebellum in conditioning of the nociceptive leg withdrawal response. Although results need to be confirmed in future studies, areas within the anterior vermis (lobules III/IV) appear to be involved in conditioning of the specific aversive reaction. Areas in the posterior vermis and posterolateral cerebellar hemisphere may be related to concomitant fear conditioning.

Abstract

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.

Significance: Results of the present event-related fMRI study suggest involvement of the human cerebellum in conditioning of the nociceptive leg withdrawal response.