Mento Giovanni, Scerif Gaia, Granziol Umberto, Franzoi Malida, Lanfranchi Silvia
Department of General Psychology, University of Padova, Padova, Italy.
Padua Neuroscience Center (PNC), University of Padova, Padova, Italy.
Front Psychol. 2020 Mar 6;11:369. doi: 10.3389/fpsyg.2020.00369. eCollection 2020.
One of the most important sources of predictability that human beings can exploit to create an internal representation of the external environment is the ability to implicitly build up subjective statistics of events' temporal structure and, consequently, use this knowledge to prepare for future actions. Stimulus expectancy can be subjectively shaped by hierarchically nested sources of prediction, capitalizing on either local or global probabilistic rules. In order to better understand the nature of local-global proactive motor control in Down Syndrome, in the present study a group of participants with Down Syndrome (DS group; = 28; mean age 29.5 ± 13 years; range 10-54) and a group of typically developing participants matched by either gender or mental age (TD-MA group; = 28; 5.6 ± 1 years; range 4-8) were administered a novel motor preparation task, defined as the Dynamic Temporal Prediction (DTP) task. In the DTP, the temporal preparation to imperative stimuli is implicitly shaped by the local increase of expectancy. This is manipulated trial-by-trial as a function of the preparatory foreperiod interval (Stimulus-Onset Asynchrony or SOA). In addition, temporal preparation can be also implicitly adjusted as a function of global predictive context, so that a block-wise SOA-distribution bias toward a given preparatory interval might determine a high-order source of expectancy, with functional consequences on proactive motor control adjustment. Results showed that in both groups motor preparation was biased by temporal expectancy when this was locally manipulated within-trials. By contrast, only the TD-MA group was sensitive to global rule changes: only in this cohort was behavioral performance overall impacted by the SOA probabilistic distribution manipulated between-blocks. The evidence of a local-global dissociation in DS suggests that the use of flexible cognitive mechanisms to implicitly extract high-order probabilistic rules in order to build-up an internal model of the temporal properties of events is disrupted in this developmental disorder. Moreover, since the content of the information to be processed in the DTP task was neither verbal nor spatial, we suggest that atypical global processing in Down Syndrome is a domain-general rather than specific aspect characterizing the cognitive profile of this population.
人类可利用的最重要的可预测性来源之一，是能够隐式地建立事件时间结构的主观统计数据，并因此利用这些知识为未来行动做准备。刺激预期可以通过分层嵌套的预测源进行主观塑造，利用局部或全局概率规则。为了更好地理解唐氏综合征中局部 - 全局主动运动控制的本质，在本研究中，一组唐氏综合征患者（DS组；n = 28；平均年龄29.5 ± 13岁；范围10 - 54岁）和一组按性别或心理年龄匹配的典型发育参与者（TD - MA组；n = 28；5.6 ± 1岁；范围4 - 8岁）接受了一项新颖的运动准备任务，即动态时间预测（DTP）任务。在DTP中，对命令刺激的时间准备通过预期的局部增加而隐式塑造。这在每次试验中作为预备前间隔（刺激起始异步或SOA）的函数进行操纵。此外，时间准备也可以根据全局预测情境进行隐式调整，因此朝着给定预备间隔的逐块SOA分布偏差可能决定一个高阶预期源，对主动运动控制调整产生功能影响。结果表明，当在试验内局部操纵时间预期时，两组的运动准备都受到时间预期的影响。相比之下，只有TD - MA组对全局规则变化敏感：只有在这个队列中，行为表现总体上受到块间操纵的SOA概率分布的影响。唐氏综合征中局部 - 全局分离的证据表明，在这种发育障碍中，利用灵活的认知机制隐式提取高阶概率规则以建立事件时间属性的内部模型的能力受到破坏。此外，由于DTP任务中要处理的信息内容既不是语言的也不是空间的，我们认为唐氏综合征中不典型的全局处理是该人群认知特征的一个领域通用而非特定方面。
