TARDIVE-DYSKINESIA AND COUPLING CONSTRAINTS IN INTER-LIMB TREMOR

The coupling of inter-limb tremor in finger and arm postural tasks was examined in adult tardive dyskinetic, severely/profoundly mentally re tarded, tardive dyskinetic and severely/profoundly mentally retarded, and normal healthy subjects. In finger tremor, the index fingers were found to operate independently in the time and frequency domains for n ormal adults but there was a modest level of coupling in the time doma in in both tardive dyskinetic groups, Inter-limb coupling in the time and frequency domains was enhanced in arm tremor for all groups, with the effect stronger in the time domain for the tardive dyskinetic grou ps and in the frequency domain for the groups of normal intelligence. There was also a persistent phase lag in the coupling of the two limbs in both postural tasks for the tardive dyskinetic subjects. These dat a show that prolonged intake of neuroleptic medication constrains inte r-limb coupling even when the task demands do not explicitly require s uch a coordination strategy. The coupling effects are stronger in arm tremor which suggests that the mass of the effector system is also a f actor in constraining the coupling of inter-limb coordination.