Recording eye movements in mice: a new approach to investigate the molecular basis of cerebellar control of motor learning and motor timing.

The vestibulocerebellum is involved in the control of compensatory eye movements. To investigate its role in learning and timing of motor behavior, we investigated compensatory eye movements in mice with the use of search coils. Wild-type mice showed the ability to increase the gain of their vestibulo-ocular reflex by visuovestibular training. This adaptation did not occur in lurcher mice, a natural mouse mutant that completely lacks Purkinje cells. During the optokinetic reflex the phase of the eye movements of lurcher mice in reference to the stimulus lagged behind that of wild-type littermates, whereas during the vestibulo-ocular reflex it led that of the wild-type mice. During combined optokinetic and vestibular stimulation, the phase of the lurcher mice lagged behind that of the wild-type mice at the low stimulus frequencies, whereas it led the phase of the wild-type mice at the high frequencies. In addition, the optokinetic response of the lurcher mice showed a significantly longer latency during constant-velocity step stimulation than that of the wild-type mice. We conclude that Purkinje cells are necessary for both learning and timing of compensatory eye movements in mice. The present description of gain adaptation and phase dynamics provides the basis for studies in which the molecular mechanisms of cerebellar control of compensatory eye movements are investigated with the use of genetically manipulated mice.

Heart volume determination with phase synchronization in normal subjects and postinfarct patients.

The authors investigated the influence of the systole-and-dyastole cycle upon the cardiac volume measured radiologically with ECG phase synchronization in prone subjects. Measurements were made in 30 healthy subjects and 27 patients with a history of myocardial infarction, all of them ambulatory. As expected, the mean cardiac volume relative to body surface was greater in postinfarct patients than in normal subjects to a high degree of statistical significance. Conversely, the differences between end-systolic and end-diastolic cardiac volumes fell short of statistical significance both in healthy subjects and in postinfarct patients. Accordingly, radiological measurements of cardiac volume without phase synchronization seem justified in the functional evaluation of postinfarct patients.