人类工作记忆的某些神经影像研究

采用神经影像技术研究人类工作记忆的脑机理是目前一个十分活跃的研究领域。研究表明存在负责不同信息加工的工作记忆系统 ,如词语工作记忆、空间工作记忆等 ,其中词语工作记忆主要由大脑左半球参与 ,空间工作记忆主要由大脑右半球参与。前额叶在工作记忆中的作用相当复杂 ,包括对记忆信息的注意和抑制、管理、整合等功能。合理巧妙的实验设计、多种研究手段的综合应用必将使人类工作记忆的脑机理得到充分阐明。     

Reduced right hemisphere activation in severely abused violent offenders during a working memory task: An fMRI study

This study uses functional magnetic resonance imaging (fMRI) to address two important gaps in our knowledge of brain functioning and violence: (1) What are the brain correlates of adults in the community who have suffered severe physical abuse early in life and who go on to perpetrate serious violence in adulthood? (2) What characterizes those who experience severe physical abuse but who refrain from serious violence? Four groups of participants recruited from the community (controls, severe physical child abuse only, serious violence only, and severely abused, seriously violent offenders) underwent fMRI while performing a visual/verbal working memory task. Violent offenders who had suffered severe child abuse show reduced right hemisphere functioning, particularly in the right temporal cortex. Abused individuals who refrain from serious violence showed relatively lower left, but higher right, activation of the superior temporal gyrus. Abused individuals, irrespective of violence status, showed reduced cortical activation during the working memory task, especially in the left hemisphere. Brain deficits were independent of IQ, history of head injury, task performance, cognitive strategy, and mental activity during the control task. Findings constitute the first fMRI study of brain dysfunction in violent offenders, and indicate that initial right hemisphere dysfunction, when combined with the effects of severe early physical abuse, predisposes to serious violence but that relatively good right hemisphere functioning protects against violence in physically abused children. Aggr. Behav. 27:111–129, 2001. © 2001 Wiley‐Liss, Inc.     

Cognitive neuroimaging: cognitive science out of the armchair

Cognitive scientists were not quick to embrace the functional neuroimaging technologies that emerged during the late 20th century. In this new century, cognitive scientists continue to question, not unreasonably, the relevance of functional neuroimaging investigations that fail to address questions of interest to cognitive science. However, some ultra-cognitive scientists assert that these experiments can never be of relevance to the study of cognition. Their reasoning reflects an adherence to a functionalist philosophy that arbitrarily and purposefully distinguishes mental information-processing systems from brain or brain-like operations. This article addresses whether data from properly conducted functional neuroimaging studies can inform and subsequently constrain the assumptions of theoretical cognitive models. The article commences with a focus upon the functionalist philosophy espoused by the ultra-cognitive scientists, contrasting it with the materialist philosophy that motivates both cognitive neuroimaging investigations and connectionist modelling of cognitive systems. Connectionism and cognitive neuroimaging share many features, including an emphasis on unified cognitive and neural models of systems that combine localist and distributed representations. The utility of designing cognitive neuroimaging studies to test (primarily) connectionist models of cognitive phenomena is illustrated using data from functional magnetic resonance imaging (fMRI) investigations of language production and episodic memory.     

The Contribution of Neuroimaging to the Study of Language and Aphasia

New structural and functional imaging methods continue to be developed at a rapid pace. In the last 25 years, advanced imaging techniques have provided insights into how language is represented and processed in the brain and how it can be disrupted by damage to, or dysfunction of, various parts of the brain. Imaging studies have also yielded new information regarding how individuals recover language after stroke. We briefly review the strengths and weaknesses of the various radiological methods currently used to study language and aphasia.     

On aims and methods in the neuroimaging of derived relations

Ingenious and seemingly powerful technologies have been developed recently that enable the visualization in some detail of events in the brain concomitant upon the ongoing behavioral performance of a human participant. Measurement of such brain events offers at the very least a new set of dependent variables in relation to which the independent variables familiarly manipulated in the operant laboratory may be explored. Two related paradigms in which a start has been made in such research concern the derivation of novel or emergent relations from a baseline set of trained relations, and include the phenomenon of transitive inference (TI), observed in studies of stimulus equivalence (SE) and serial learning (SL) or seriation. This paper reviews some published and forthcoming neuroimaging studies of these and related phenomena, and considers how this line of research both demands and represents a welcome synthesis between types of question and levels of explanation in behavioral science that often have been seen as antithetical.     

BEHAVIOR ANALYSIS OF MOTION CONTROL FOR PEDIATRIC NEUROIMAGING

Magnetic resonance imaging is a promising technological advance used for research and diagnosis of disease. The procedure has no risks, except when uncooperative patients require sedation. Four normal children participated in simulated scans to study the effects of (a) antecedent changes in the imaging environment and (b) operant conditioning of movement inhibition. Changing the environment can decrease movement, but operant contingencies were necessary to decrease movement to a level that, in most cases, would allow the procedure to occur without sedation.     

AVERSIVE CONTROL: A SEPARATE DOMAIN?

Traditionally, aversive control has been viewed as a separate domain within behavior theory. Sometimes this separateness has been based upon a distinction between reinforcement and punishment, and sometimes upon a distinction between positive and negative reinforcement. The latter is regarded here as the more compelling basis, due to some inherent procedural asymmetries. An approach to the interpretation of negative reinforcement is presented, with indication of types of experiments that support it and that also point to promising directions for further work. However, most of the interpretive issues that arise here are relevant to positively reinforced behavior as well. These include: possible reformulation of the operant/respondent distinction; the place of emotional concepts in behavior analysis; the need for simultaneous, complementary analysis on differing time scales; the understanding of behavioral situations with rewarding or aversive properties that depend as much upon the contingencies that the situations involve as upon the primary rewarding or aversive stimuli that they include. Thus, an adequate understanding of this domain, which has been traditionally viewed as distinct, has implications for all domains of behavior-analytic theory.     

老年人声音诱发闪光错觉的大脑静息态低频振幅

声音诱发闪光错觉(sound-induced flash illusion, SiFI)是一种听觉占主导性的多感觉整合现象, 即当视觉闪光伴随不相等数量的听觉声音在100 ms内相继或同时呈现时, 个体会错觉性地知觉到视觉闪光的个数与听觉声音的数量相等。本研究分别将老年人群体和年轻人群体的声音诱发闪光错觉量(裂变错觉和融合错觉)与全脑的静息态低频振幅(amplitude of low-frequency fluctuation, ALFF)进行相关分析, 考察老年人群体声音诱发闪光错觉效应与大脑静息状态自发活动区域的关系。结果发现, 无论是裂变错觉还是融合错觉, 老年人声音诱发闪光错觉均增大。对于裂变错觉, 老年人的错觉量与内侧前额叶皮层的自发活动呈显著正相关; 对于融合错觉, 老年人的错觉量与额下回、额中回和颞下回的自发活动呈显著正相关, 与枕上回和舌回的自发活动呈现显著的负相关。结果表明, 老年人声音诱发闪光错觉量增大的原因与大脑中多个脑区的静息态自发活动存在关系。     

Neural localization of semantic context effects in electromagnetic and hemodynamic studies

Measures of electrical brain activity (event-related potentials, ERPs) have been useful in understanding language processing for several decades. Extant data suggest that the amplitude of the N400 component of the ERP is a general index of the ease or difficulty of retrieving stored conceptual knowledge associated with a word, which is dependent on both the stored representation itself, and the retrieval cues provided by the preceding context. Recordings from patients with brain damage, intracranial recordings, and magnetoencephalographic data implicate a (probably large portion of) the left temporal lobe as the largest source of the N400 semantic context effect, with a substantial but lesser contribution from the right temporal lobe. Event-related functional magnetic resonance (fMRI) studies using semantic context manipulations are dominated by observations of greater hemodynamic activity for incongruent sentence completions or semantically unrelated words than congruent or related words, consistent with the direction of the ERP effect. The locations of the hemodynamic effects show some variability across studies, but one commonly identified region is the left superior temporal gyrus, which is compatible with the electrophysiological results. A second commonly identified region in the fMRI studies is the left inferior frontal gyrus, which does not appear to make a substantial contribution to the N400 effect.     

Neural substrates of reduced walking activity after supratentorial stroke: A voxel-based lesion symptom mapping study

BackgroundMost stroke patients exhibit low levels of walking activity, a key component of secondary stroke prevention. The predictors of walking activity may be multifactorial and are thus far partially understood. We aimed to study the neuroanatomic correlates of low levels of daily walking activity following hemispheric stroke.MethodsIn this cross-sectional study, 33 community-dwelling stroke survivors (age: 63.9 ± 12.9 years; % female: 36.4%; NIHSS at admission: 3.3 ± 4.0) were prospectively recruited at least 3 months after a first ever, unilateral, supratentorial stroke confirmed by brain magnetic resonance imaging. Walking activity was measured by daily step counts (steps∙day⁻¹), recorded using an Actigraph GT3x+ triaxial accelerometer over 7 consecutive days. Voxel-based lesion-symptom mapping was performed to identify brain areas associated with walking activity following stroke.ResultsParticipants presented 4491.9 ± 2473.7 steps∙day⁻¹. Lower levels of walking activity were related to lesions of the posterior part of the putamen, of the posterior limb of the internal capsule and of the anterior part of the corona radiata. No cortical region was associated with walking activity.ConclusionsOur preliminary results identify subcortical neuroanatomical correlates for reduced walking activity following stroke. If confirmed, these results could serve as a rationale for the development of targeted rehabilitative strategy to improve mobility after stroke.