TMS to the “occipital face area” affects recognition but not categorization of faces

The human cortical system for face perception is comprised of a network of connected regions including the middle fusiform gyrus (“fusiform face area” or FFA), the inferior occipital cortex (“occipital face area” or OFA), and the superior temporal sulcus. The traditional hierarchical feedforward model of visual processing suggests information flows from early visual cortex to the OFA for initial face feature analysis to higher order regions including the FFA for identity recognition. However, patient data suggest an alternative model. Patients with acquired prosopagnosia, an inability to visually recognize faces, have been documented with lesions to the OFA but who nevertheless show face-selective activation in the FFA. Moreover, their ability to categorize faces remains intact. This suggests that the FFA is not solely responsible for face recognition and the network is not strictly hierarchical, but may be organized in a reverse hierarchical fashion. We used transcranial magnetic stimulation (TMS) to temporarily disrupt processing in the OFA in neurologically-intact individuals and found participants’ ability to categorize intact versus scrambled faces was unaffected, however face identity discrimination was significantly impaired. This suggests that face categorization but not recognition can occur without the “earlier” OFA being online and indicates that “lower level” face category processing may be assumed by other intact face network regions such as the FFA. These results are consistent with the patient data and support a non-hierarchical, global-to-local model with re-entrant connections between the OFA and other face processing areas.     

数字加工与空间关系的研究进展

数学的产生和发展使数字和空间之问产生了紧密的联系,目前的实验已经表明了数字的大小与空间注意存在自动的联系。数字和空间的自动联系是由生物和文化因素共同作用的结果。通过总结数字和空间的脑成像研究,本文认为角回、顶内沟区域可能在数字和空间相互作用中发挥了重要的作用。     

传递性推理的ERP研究

以抽象的内容作为实验材料,测定15名大学生在完成三种不同类型的传递性推理任务和基线任务(记忆判断任务)时的事件相关电位(ERP),探讨传递性推理过程的脑内时程动态变化。研究发现,三种推理任务所诱发的波形基本一致,而推理任务与基线任务之间的ERP波形存在明显的差异。这说明对于传递性推理,被试可能是根据视觉的空间表征对信息进行加工的,结果进一步支持了心理模型理论。     

Hippocampus-dependent strategy choice predicts low levels of cell proliferation in the dentate gyrus

Neurogenesis continues to occur throughout life in the mammalian hippocampus. Previous research has suggested that the production of new neurons in the hippocampus during adulthood may be related to hippocampus-dependent learning and memory. However, the exact relationship between adult neurogenesis and learning and memory remains unclear. Here we investigated whether learning strategy selection is related to cell proliferation or to survival of new neurons in the hippocampus of adult male rats. We trained rats on alternating blocks of hippocampus-dependent (hidden platform) and hippocampus-independent (visible platform) versions of the Morris water task with the platform always in the same position. Following training, rats were given a probe session during which the platform was visible and in a novel location. Preferred strategy was determined by observing the initial swim path. Rats were classified as place strategy (hippocampus-dependent) users if they swam to the old platform location. Cue strategy (hippocampus-independent) users were classified as those rats that swam initially to the visible platform. Our results indicate that rats that preferentially used a place strategy had significantly lower cell proliferation than cue strategy users. However, there was no significant difference in cell survival or number of immature neurons between strategy user groups. These results suggest that low levels of cell proliferation in the dentate gyrus may be conducive or coincident with more efficient memory processing in the hippocampus.     

The right parahippocampal gyrus contributes to the formation and maintenance of bound information in working memory

Working memory is devoted to the temporary storage and on-line manipulation of information. Recently, an integrative system termed the episodic buffer has been proposed to integrate and hold information being entered or retrieved from episodic memory. Although the brain system supporting such an integrative buffer is still in debate, the medial temporal lobe appears to be a promising candidate for the maintenance of bound information. In the current work, binding was assessed by comparing two conditions in which participants had to retain three letters and three spatial locations presented either bound or separate. At the behavioral level, lower performance was found for bound information than for separate information. When contrasting the two conditions, activation in the right parahippocampal gyrus was greater for the encoding and maintenance of bound information. No activation was observed in the medial temporal lobe during the retrieval of bound information. Together, our results suggest that the parahippocampal gyrus may underlie the integrative and maintenance functions of the episodic buffer.     

Modulation of brain activity during phonological familiarization

We measured brain activity in 12 adults for the repetition of auditorily presented words and nonwords, before and after repeated exposure to their phonological form. The nonword phoneme combinations were either of high (HF) or low (LF) phonotactic frequency. After familiarization, we observed, for both word and nonword conditions, decreased activation in the left posterior superior temporal gyrus, in the bilateral temporal pole and middle temporal gyri. At the same time, interaction analysis showed that the magnitude of decrease of activity in bilateral posterior temporal lobe was significantly smaller for LF nonwords, relative to words and HF nonwords. Decrease of activity in this area also correlated with the size of behavioral familiarization effects for LF nonwords. The results show that the posterior superior temporal gyrus plays a fundamental role during phonological learning. Its relationship to sublexical and lexical phonological processing as well as to phonological short-term memory is discussed.