Developmental shifts in fMRI activations during visuospatial relational reasoning

To investigate maturational plasticity of fluid cognition systems, functional brain imaging was undertaken in healthy 8-19 year old participants while completing visuospatial relational reasoning problems similar to Raven's matrices and current elementary grade math textbooks. Analyses revealed that visuospatial relational reasoning across this developmental age range recruited activations in the superior parietal cortices most prominently, the dorsolateral prefrontal, occipital-temporal, and premotor/supplementary cortices, the basal ganglia, and insula. There were comparable activity volumes in left and right hemispheres for nearly all of these regions. Regression analyses indicated increasing activity predominantly in the superior parietal lobes with developmental age. In contrast, multiple anterior neural systems showed significantly less activity with age, including dorsolateral and ventrolateral prefrontal, paracentral, and insula cortices bilaterally, basal ganglia, and particularly large clusters in the midline anterior cingulate/medial frontal cortex, left middle cingulate/supplementary motor cortex, left insula-putamen, and left caudate. Findings suggest that neuromaturational changes associated with visuospatial relational reasoning shift from a more widespread fronto-cingulate-striatal pattern in childhood to predominant parieto-frontal activation pattern in late adolescence.     

Contributions of volumetrics of the hippocampus and thalamus to verbal memory in temporal lobe epilepsy patients

Recent theories have posited that the hippocampus and thalamus serve distinct, yet related, roles in episodic memory. Whereas the hippocampus has been implicated in long-term memory encoding and storage, the thalamus, as a whole, has been implicated in the selection of items for subsequent encoding and the use of retrieval strategies. However, dissociating the memory impairment that occurs following thalamic injury as distinguished from that following hippocampal injury has proven difficult. This study examined relationships between MRI volumetric measures of the hippocampus and thalamus and their contributions to prose and rote verbal memory functioning in 18 patients with intractable temporal lobe epilepsy (TLE). Results revealed that bilateral hippocampal and thalamic volume independently predicted delayed prose verbal memory functioning. However, bilateral hippocampal, but not thalamic, volume predicted delayed rote verbal memory functioning. Follow-up analyses indicated that bilateral thalamic volume independently predicted immediate prose, but not immediate rote, verbal recall, whereas bilateral hippocampal volume was not associated with any of these immediate memory measures. These findings underscore the cognitive significance of thalamic atrophy in chronic TLE, demonstrating that hippocampal and thalamic volume make quantitatively, and perhaps qualitatively, distinct contributions to episodic memory functioning in TLE patients. They are also consistent with theories proposing that the hippocampus supports long-term memory encoding and storage, whereas the thalamus is implicated in the executive aspects of episodic memory.     

边界促进空间导航的认知神经机制

边界是指在人的视野中占据较大比例,且具有立体拓展平面的障碍物,对于人类和动物的空间导航行为具有极大的促进作用。认知发展研究发现儿童早期(1岁半～2岁)通过加工边界的空间几何结构实现物体定位,并且随着年龄的发展逐渐学会利用边界的高度信息(3.1岁～4.7岁)、长度信息(4～5岁)、视觉阻碍性信息(5岁)等完成空间导航。基于这些认知过程,神经影像学研究主要以成人为研究被试,发现大脑中的内侧颞叶和顶叶脑区在边界加工中有着不同功能作用。具体而言,边界的空间几何结构及构成要素(高度、长度和角度)体位置的学习和提取则由海马负责。但是,仍存在一些研究问题值得未来深入S探c讨i。e第n一c,e拓展深化边界促进与后顶叶之间的功能交互。第三,密切关注大脑对场地边界与场地中心编码的心理或神经表征的区别和联系。第四,重点考察阿尔兹海默症有关基因易感人群在基于边界导航的行为受损情况。最后,延伸探讨边界在长时记忆、时间知觉、视觉空间、社交网络等领域的影响机制。     

Factors affecting medial temporal lobe engagement for past and future episodic events: an ALE meta-analysis of neuroimaging studies

Remembering the past and envisioning the future are at the core of one's sense of identity. Neuroimaging studies investigating the neural substrates underlying past and future episodic events have been growing in number. However, the experimental paradigms used to select and elicit episodic events vary greatly, leading to disparate results, especially with respect to the laterality and antero-posterior localization of hippocampal and adjacent medial temporal activations (i.e., parahippocampal, entorhinal and perirhinal cortices, amygdala). Although a central concern in today's literature, the issue of hippocampal and medial temporal lobe laterality and antero-posterior segregation in past and future episodic events has not yet been addressed extensively. Using the activation likelihood estimation (ALE) procedure (Turkeltaub, Eden, Jones, & Zeffiro, 2002), we performed a meta-analysis of hippocampal and adjacent medial temporal coordinates extracted from neuroimaging studies examining past remembering and future envisioning. We questioned whether methodological choices could influence the laterality of activations, namely (1) the type of cue used (generic vs. specific), (2) the type of task performed (recognition vs. recall/imagine), (3) the nature of the information retrieved (episodic vs. "strictly" episodic events) and (4) the age of participants. We consider "strictly" episodic events as events which are not only spatio-temporally unique and personal like episodic events, but are also associated with contextual and phenomenological details. These four factors were compared two-by-two, generating eight whole-brain statistical maps. Results indicate that (1) specific cues tend to activate more the right anterior hippocampus compared to the use of generic cues, (2) recall/imagine tasks tend to recruit more the left posterior parahippocampal gyrus compared to recognition tasks, (3) (re/pre)experiencing strictly episodic events tends to activate more the bilateral posterior hippocampus compared to episodic events and (4) older subjects tend to activate more the right anterior hippocampus compared to younger subjects. Importantly, our results stress that strictly episodic events triggered by specific cues elicit greater left posterior hippocampal activation than episodic events triggered by specific cues. These findings suggest that such basic methodological choices have an impact on the conclusions reached regarding past and future (re/pre)experiencing and their neural substrates.     

Different types of working memory binding in epilepsy patients with unilateral anterior temporal lobectomy

The medial temporal lobe is an important structure for long-term memory formation, but its role in working memory is less clear. Recent studies have shown hippocampal involvement during working memory tasks requiring binding of information. It is yet unclear whether this is limited to tasks containing spatial features. The present study contrasted three binding conditions and one single-item condition in patients with unilateral anterior temporal lobectomy.A group of 43 patients with temporal lobectomy (23 left; 20 right) and 20 matched controls were examined with a working memory task assessing spatial relational binding (object–location), non-spatial relational binding (object–object), conjunctive binding (object–colour) and working memory for single items. We varied the delay period (3 or 6 s), as there is evidence showing that delay length may modulate working memory performance.The results indicate that performance was worse for patients than for controls in both relational binding conditions, whereas patients were unimpaired in conjunctive binding. Single-item memory was found to be marginally impaired, due to a deficit on long-delay trials only.In conclusion, working memory binding deficits are found in patients with unilateral anterior temporal lobectomy. The role of the medial temporal lobe in working memory is not limited to tasks containing spatial features. Rather, it seems to be involved in relational binding, but not in conjunctive binding. The medial temporal lobe gets involved when working memory capacity does not suffice, for example when relations have to be maintained or when the delay period is long.     

Age-Related Influences on Repetition Priming in the Verb Generation Task: Examining the Role of Response Competition

ABSTRACT

The identification-production framework suggests that aging is associated with a decline in production forms of repetition priming, particularly under test conditions that maximize response competition. The present study examined this prediction by testing young and healthy older adults in a single-encoding version of the verb generation task in which some items had one dominant verb response (low competition) or had no such dominant response (high competition). Further analyses examined whether priming and error rates were related to performance on neuropsychological tests purported to measure frontal lobe functioning. Priming was invariant across age groups and was not related to frontal lobe status in older adults, but frontal lobe status did predict task performance: low-frontal older adults made more errors than high-frontal older adults, particularly for high-competition items and items with high association strength. These results are not consistent with the identification-production framework, but are consistent with the conclusions that (a) aging is associated with invariance in the processes that support repetition priming in the verb generation task and (b) frontal lobe status in aging is related to verb generation performance.     

Influence of memory strategies on memory test performance: A study in healthy and pathological aging

ABSTRACT

The ability to generate memory strategies is a key factor in the performance of episodic memory tasks. Whether the ability to generate memory strategies exerts an influence in the performance of memory tests in the elderly population is still a matter of debate. Here we present results from an experimental memory task (Test of Memory Strategies, TMS), comprised of five lists of words starting from an incidental learning task, and four more lists which progressively gain in their external organization of the material, reducing the necessity of mobilizing complex memory strategies. TMS has been applied to four groups of elderly patients (amnestic Mild Cognitive Impairment – aMCI, multidomain (mMCI), and Vascular Cognitive Impairment – VCI and Depression) and a healthy aging group. In conditions with low organization of the material, the mMCI and VCI groups (both showing a greater executive function impairment) have shown lower performance. However, as the material was progressively organized, they improved their performance. The aMCI group showed similar performance to the control group at the lower level of external organization but did not improve performance in conditions with a high level of external organization. The mMCI and VCI groups showed lower performance on all TMS conditions compared with controls. Discriminant analysis revealed 90% sensitivity and specificity to differentiate between groups based on TMS conditions. These results indicate how executive functions influence performance on memory tasks in elderly subjects with different neuropsychological profiles.     

Intentional binding as a marker of agency across the lifespan

The feeling of control over actions and their external effects is known as Sense of Agency (SoAg). People usually have a distinctive SoAg for events caused by their own actions. However, if the agent is a child or an older person, this feeling of being responsible for the consequences of an action may differ from what an adult would feel. The idea would be that children and elderly may have a reduced SoAg since their frontal lobes are developing or have started to loose their efficiency. The aim of this study was to elucidate whether the SoAg changes across lifespan, using the Intentional Binding (i.e., the temporal attraction between a voluntary action and its sensory consequence) as implicit measure. Data show that children and elderly are characterized by a reduced SoAg as compared to adults. These findings provide a fundamental step in the characterization of SoAg dynamics throughout individuals’ lifetime.     

The two sides of the mental clock: the Imaginal HemiSpatial Effect in the healthy brain

When subjects are asked to compare the mental images of two analog clocks telling different times (the mental clock test), they are faster to process angles formed by hands located in the right than in the left half of the dial. In the present paper, we demonstrate that this Imaginal HemiSpatial Effect (IHSE) can be also observed in two modified versions of the mental clock test: in Experiment 1 subjects had to imagine the position occupied by two numbers within a clock face and to judge if the subtended angle was smaller or greater than 90 degrees , while in Experiment 2 subjects were asked to match two imagined positions on a clock face with two visually presented locations. The finding of the IHSE in these tasks suggested that it is a genuine phenomenon related to spatial imagery tasks, and is consistent with recent neuroimaging evidence that the left parietal lobe is mainly involved in the generation of spatial mental images.     

The persistence of erroneous familiarity in an epileptic male: challenging perceptual theories of déjà vu activation

We report the case of a 39-year-old, temporal lobe epileptic male, MH. Prior to complex partial seizure, experienced up to three times a day, MH often experiences an aura experienced as a persistent sensation of déjà vu. Data-driven theories of déjà vu formation suggest that partial familiarity for the perceived stimulus is responsible for the sensation. Consequently, diverting attention away from this stimulus should cause the sensation to dissipate. MH, whose sensations of déjà vu persist long enough for him to shift his perceptual focus a number of times during the experience, spontaneously reports that these shifts make no difference to the sensation experienced. This novel observation challenges data-driven theories of déjà vu formation which have been used to explain the occurrence of déjà vu in those with temporal lobe epilepsy and the general population. Clearly, in epilepsy, erratic neuronal firing is the likely contributor, and in this paper we postulate that such brain firing causes higher-order erroneous 'cognitive feelings'. We tentatively extend this account to the general population. Rather than being a reaction to familiar elements in perceptual stimuli, déjà vu is likely to be the result of a cognitive feeling borne of the erroneous activation of neural familiarity circuits such as the parahippocampal gyrus, persisting as long as this activation persists.