Haeger Alexa, Pouzat Christophe, Luecken Volker, N'Diaye Karim, Elger Christian, Kennerknecht Ingo, Axmacher Nikolai, Dinkelacker Vera
JARA-BRAIN, Jülich, Germany.
Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine (INM-11), Jülich, Germany.
Front Behav Neurosci. 2021 Nov 18;15:744466. doi: 10.3389/fnbeh.2021.744466. eCollection 2021.
Face expertise is a pivotal social skill. Developmental prosopagnosia (DP), i.e., the inability to recognize faces without a history of brain damage, affects about 2% of the general population, and is a renowned model system of the face-processing network. Within this network, the right Fusiform Face Area (FFA), is particularly involved in face identity processing and may therefore be a key element in DP. Neural representations within the FFA have been examined with Representational Similarity Analysis (RSA), a data-analytical framework in which multi-unit measures of brain activity are assessed with correlation analysis. Our study intended to scrutinize modifications of FFA-activation during face encoding and maintenance based on RSA. Thirteen participants with DP (23-70 years) and 12 healthy control subjects (19-62 years) participated in a functional MRI study, including morphological MRI, a functional FFA-localizer and a modified Sternberg paradigm probing face memory encoding and maintenance. Memory maintenance of one, two, or four faces represented low, medium, and high memory load. We examined conventional activation differences in response to working memory load and applied RSA to compute individual correlation-matrices on the voxel level. Group correlation-matrices were compared via Donsker's random walk analysis. On the functional level, increased memory load entailed both a higher absolute FFA-activation level and a higher degree of correlation between activated voxels. Both aspects were deficient in DP. Interestingly, control participants showed a homogeneous degree of correlation for successful trials during the experiment. In DP-participants, correlation levels between FFA-voxels were significantly lower and were less sustained during the experiment. In behavioral terms, DP-participants performed poorer and had longer reaction times in relation to DP-severity. Furthermore, correlation levels were negatively correlated with reaction times for the most demanding high load condition. We suggest that participants with DP fail to generate robust and maintained neural representations in the FFA during face encoding and maintenance, in line with poorer task performance and prolonged reaction times. In DP, alterations of neural coding in the FFA might therefore explain curtailing in working memory and contribute to impaired long-term memory and mental imagery.
面部识别能力是一项关键的社交技能。发育性面孔失认症（DP），即没有脑损伤病史却无法识别面孔的情况，影响着约2%的普通人群，是面孔处理网络的一个著名模型系统。在这个网络中，右侧梭状面孔区（FFA）尤其参与面孔身份识别处理，因此可能是DP中的一个关键要素。FFA内的神经表征已通过表征相似性分析（RSA）进行研究，RSA是一种数据分析框架，其中通过相关分析评估大脑活动的多单元测量值。我们的研究旨在基于RSA仔细研究面孔编码和维持过程中FFA激活的变化。13名患有DP的参与者（23至70岁）和12名健康对照者（19至62岁）参与了一项功能磁共振成像研究，包括形态学磁共振成像、功能性FFA定位以及一个经过修改的斯特恩伯格范式，用于探究面孔记忆编码和维持。对一张、两张或四张面孔的记忆维持分别代表低、中、高记忆负荷。我们研究了对工作记忆负荷的常规激活差异，并应用RSA在体素水平计算个体相关矩阵。通过唐斯克随机游走分析比较组相关矩阵。在功能层面，记忆负荷增加既带来了更高的绝对FFA激活水平，也带来了激活体素之间更高的相关程度。这两个方面在DP患者中都存在缺陷。有趣的是，对照参与者在实验期间成功试验的相关程度较为一致。在DP参与者中，FFA体素之间的相关水平显著更低，并且在实验过程中维持时间更短。在行为方面，DP参与者的表现更差，且反应时间与DP严重程度相关更长。此外，在要求最高的高负荷条件下，相关水平与反应时间呈负相关。我们认为，患有DP的参与者在面孔编码和维持过程中未能在FFA中生成强大且持续的神经表征，这与较差的任务表现和较长的反应时间一致。因此，在DP中，FFA内神经编码的改变可能解释工作记忆的缩减，并导致长期记忆和心理意象受损。
