Motor imagery across ault life-span

INTRODUCTION: Mental motor imagery (M.I.) can be defined as a mental state during which real movements. are evoked without overt actions [1]. Although some evidence of an aged-related decline of this ability has been provided by behavioural experiments [2-3], the neurofunct1onal correlates of these changes have not been studied as yet. Here we describe a behavioural and fMRI study on the effects of aging on M.l. METHODS: 24 young (27±5.6 years) and 24 elderly subjects (60±4,6 years) performed two bloc -design tasks requiring actual and mental execut1on of f1nger tapping movements. Partecipants also underwent_ a behavioural menta! chronometry test to check for a poss1ble decline in action representation, by studying temporal si milarities between M.l. and execution. RESULTS: While in young partecipants, executed and imagined movement durations were highly correlated (p <.001), this was not the case for the elderly participants (p> .05) who lost the isochrony between overt and covert actions. The fMRI experiment showed hyperactivations of the old brain in bilatera! occipital areas and in the inferior temporal gyrus. Further hyperactivations were in the left fusiform gyrus, hippocampus, putamen and thalamus and in the right superior parietal gyrus and superior temporal gyrus. CONCLUSIONS: These observations suggest that the healthy elderly have decreased M.l. capacities and over­ recruit brain regions typical of other imaginative approaches, such as visual imagery, as a possible alternative strategy to deal with a task that they are no more able to solve with a motoric method. REFERENCES 1. Jeannerod, M. and V. Frak, Mental imaging of motor activity in humans. Curr Opin Neurobiol, 1999. 9(6): p. 735-9. 2. Skoura, X., et al., Mentally represented motor actions in normal aging. l. Age effects on the temporal features of overt and covert execution of actions. Behav Brain Res, 2005. 165(2): p. 229-39. 3. Mulder, T., et al., Motor imagery: the relation between age and imagery capacity. Hum Mov Sci, 2007. 26(2): p. 203-11.