Striatal dopamine release in reading and writing measured with [I-123]iodobenzamide and single photon emission computed tomography in right handed human subjects

Competition between endogenous dopamine and a radioligand for postsynaptic dopamine D-2 receptor binding was examined in two groups of eight subjects each who had to read or write off a text, respectively, and in a control gr oup. Single photon emission computed tomography (SPECT) and the ligand [I-1 23]iodobenzamide (IBZM) were used for in vivo imaging. Subjects commenced r eading or writing immediately before IBZM injection and continued for 30 mi n thereafter. SPECT images were acquired 60 min later. Striatum-to-parietal -cortex IBZM uptake ratios were lower in subjects who wrote off the text th an in controls indicating competition of IBZM and dopamine. There was no di fference between subjects who read the text and controls. Thus, dopamine re lease occurs as a consequence of the motoric activity involved in writing r ather than of cognitive functions necessary for reading the text. (C) 2000 Elsevier Science Ireland Ltd. Ail rights reserved.