School of Psychology, Bangor University, Bangor, UK.
Brain Imaging Center, Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, USA; Department of Child and Adolescent Psychiatry, Psychotherapy and Psychosomatics, University of Freiburg, Freiburg, Germany.
Neuroimage. 2019 Jan 15;185:208-221. doi: 10.1016/j.neuroimage.2018.10.039. Epub 2018 Oct 17.
The current study investigates a new neurobiological model of human hand choice: The Posterior Parietal Interhemispheric Competition (PPIC) model. The model specifies that neural populations in bilateral posterior intraparietal and superior parietal cortex (pIP-SPC) encode actions in hand-specific terms, and compete for selection across and within hemispheres. Actions with both hands are encoded bilaterally, but the contralateral hand is overrepresented. We use a novel fMRI paradigm to test the PPIC model. Participants reach to visible targets while in the scanner, and conditions involving free choice of which hand to use (Choice) are compared with when hand-use is instructed. Consistent with the PPIC model, bilateral pIP-SPC is preferentially responsive for the Choice condition, and for actions made with the contralateral hand. In the right pIP-SPC, these effects include anterior intraparietal and superior parieto-occipital cortex. Left dorsal premotor cortex, and an area in the right lateral occipitotemporal cortex show the same response pattern, while the left inferior parietal lobule is preferentially responsive for the Choice condition and when using the ipsilateral hand. Behaviourally, hand choice is biased by target location - for targets near the left/right edges of the display, the hand in ipsilateral hemispace is favoured. Moreover, consistent with a competitive process, response times are prolonged for choices to more ambiguous targets, where hand choice is relatively unbiased, and fMRI responses in bilateral pIP-SPC parallel this pattern. Our data provide support for the PPIC model, and reveal a selective network of brain areas involved in free hand choice, including bilateral posterior parietal cortex, left-lateralized inferior parietal and dorsal premotor cortices, and the right lateral occipitotemporal cortex.
双侧顶间竞争（PPIC）模型。该模型指定双侧顶内和上顶叶皮层（pIP-SPC）中的神经群体以手部特定的术语编码动作，并在半球间和半球内竞争选择。双手动作均被双侧编码，但对侧手被过度代表。我们使用一种新的 fMRI 范式来测试 PPIC 模型。参与者在扫描过程中伸手去够可见的目标，并且比较了自由选择使用哪只手的条件（Choice）与指示使用手的条件。与 PPIC 模型一致，双侧 pIP-SPC 对 Choice 条件和对侧手的动作有优先反应。在右 pIP-SPC 中，这些效应包括前顶内和上顶枕叶皮质。左背侧运动前皮质和右侧外侧枕颞皮质的一个区域显示出相同的反应模式，而左侧下顶叶小叶则对 Choice 条件和同侧手的使用有优先反应。行为上，手的选择受到目标位置的影响 - 对于靠近显示器左右边缘的目标，同侧半空间的手更受青睐。此外，与竞争过程一致，对更模糊目标的选择反应时间延长，此时手的选择相对无偏差，双侧 pIP-SPC 的 fMRI 反应与该模式一致。我们的数据支持 PPIC 模型，并揭示了一个涉及自由手选择的大脑区域的选择性网络，包括双侧顶后皮质、左侧下顶叶和背侧运动前皮质以及右侧外侧枕颞皮质。
