Does cross‐frequency phase coupling of oscillatory brain activity contribute to a better understanding of visual working memory?

Nesting of fast rhythmical brain activity (gamma) into slower brain waves (theta) has frequently been suggested as a core mechanism of multi‐item working memory (WM) retention. It provides a better understanding of WM capacity limitations, and, as we discuss in this review article, it can lead to applications for modulating memory capacity. However, could cross‐frequency coupling of brain oscillations also constructively contribute to a better understanding of the neuronal signatures of working memory compatible with theoretical approaches that assume flexible capacity limits? Could a theta‐gamma code also be considered as a neural mechanism of flexible sharing of cognitive resources between memory representations in multi‐item WM? Here, we propose potential variants of theta‐gamma coupling that could explain WM retention beyond a fixed memory capacity limit of a few visual items. Moreover, we suggest how to empirically test these predictions in the future.     

How infant-directed actions enhance infants’ attention,learning, and exploration: Evidence from EEG and computational modeling

When teaching infants new actions, parents tend to modify their movements. Infants prefer these infant-directed actions (IDAs) over adult-directed actions and learn well from them. Yet, it remains unclear how parents’ action modulations capture infants’ attention. Typically, making movements larger than usual is thought to draw attention. Recent findings, however, suggest that parents might exploit movement variability to highlight actions. We hypothesized that variability in movement amplitude rather than higher amplitude is capturing infants’ attention during IDAs. Using EEG, we measured 15-month-olds’ brain activity while they were observing action demonstrations with normal, high, or variable amplitude movements. Infants’ theta power (4–5 Hz) in fronto-central channels was compared between conditions. Frontal theta was significantly higher, indicating stronger attentional engagement, in the variable compared to the other conditions. Computational modelling showed that infants’ frontal theta power was predicted best by how surprising each movement was. Thus, surprise induced by variability in movements rather than large movements alone engages infants’ attention during IDAs. Infants with higher theta power for variable movements were more likely to perform actions successfully and to explore objects novel in the context of the given goal. This highlights the brain mechanisms by which IDAs enhance infants’ attention, learning, and exploration.     

注意过程中的行为振荡现象

行为振荡是个体心理加工过程的周期性动态变化在行为上的表现。通过高时间分辨率的行为采样方法, 行为振荡研究为探索视觉注意的时间动态结构提供了一个新的视角。各种不同的注意任务中都发现存在行为振荡现象。大量行为振荡证据表明, 注意过程存在两种主要的节律成分：反映注意抑制的α节律(8~13 Hz)和反映注意转移的θ节律(4~8 Hz)。这些结果有助于揭示注意的时间动态结构, 也为序列搜索理论和平行搜索理论之间的争论提供了新的分析思路。行为振荡的节律特征会受到一些潜在因素(如任务难度、线索有效性)的影响。行为振荡和神经振荡在某些任务中表现出相同的节律成分, 提示两者涉及了相似的心理过程。后续研究应进一步关注各种不同的注意控制过程以及多模态交互任务, 深入探索其行为振荡特点, 以更好地揭示注意的动态加工过程。     

寻找自我：自我相关物主代词的编码与theta节律的活动*

之前的相关研究表明相位锁定的脑电活动调节自我相关物主代词的认知加工。然而,非相位锁定的神经震荡是否参与自我相关物主代词的加工目前还不清楚。为了考察非相位锁定的神经震荡在自我相关物主代词加工中的功能性意义,我们要求被试完成一个标准/偏差刺激辨别任务,同时记录其脑电活动。小波分析的结果发现相对于非自我相关物主代词“他的”,自我相关物主代词“我的”引发了更大的 theta 频带(4~8 Hz)能量活动,这表明 theta 波的活动对自我相关信息加工中脑的大范围神经同步形成的功能性神经网络起着一个很重要的作用。     

情绪诱发视盲任务中的情绪注意控制机制：来自脑电ERP和时频分析的证据

采用脑电时频分析技术,对情绪诱发视盲任务中的情绪控制机制进行了分析。实验设置负性图片、中性图片及填充图片三种干扰刺激条件,关注被试正确完成目标识别时的干扰刺激加工过程。实验结果发现,负性与中性干扰刺激在注意加工阶段均较控制性的填充图片条件诱发前额中央分布的theta同步化效应,而且负性刺激所诱发的此效应又较中性情绪刺激更多分布在左侧前额和颞枕部。实验结果表明：（1）情绪诱发视盲任务下被试确实存在对于情绪干扰刺激的自上而下控制;（2）相比中性干扰刺激,负性干扰刺激在EIB中的情绪注意控制机制不仅包括前人所发现的后部颞枕区对刺激识别的注意控制,而且包括前额叶参与下的负性情绪控制。     

Validity and reliability of electroencephalographic frontal alpha asymmetry and frontal midline theta as biomarkers for depression

Electroencephalographic (EEG) frontal alpha asymmetry (FAA) and frontal midline (FM) theta have been suggested as biomarkers for depression and anxiety, but have mostly been assessed in small and non‐clinical studies. In a clinical sample of 79 adults with depression (ICD‐10: F32), resting EEG and scales of depression (MADRS) and anxiety (HADS‐A) were measured at intake and after 3 months. FAA and FM theta values were referenced to a normative population database. Internal consistency, test‐retest reliability, and correlations with psychiatric tests were examined. Reliability was sufficient. However, FAA and FM theta values were close to the general population, and correlations with psychiatric tests were mostly small and non‐significant, with the exception of FAA on F7–F8 z‐scores and HADS‐A. We conclude that the validity of FAA and FM theta and therefore their potential as biomarkers for depression and anxiety remain unclear.     

Brain electrical activity from encoding to retrieval while maintaining and manipulating information in working memory

ABSTRACT

Differences between working memory maintenance (Mt) and manipulation (Mp) have been studied, mostly in the absence of stimuli (delay period); encoding and retrieval phases have been less explored. The present study assessed differences between Mt and Mp, by means of event-related potentials (ERPs) and event-related synchronisation (ERS) and desynchronisation (ERD) for theta, alpha and beta bands at: encoding, delay period and retrieval; using a delayed-match to sample task (DMST). Twenty-six young volunteers solved two DMST conditions (one for Mt and one for Mp). Higher behavioural accuracy for Mt than for Mp was observed. At encoding, higher amplitude for Mt at posterior regions to N1, P2 and P3 components were observed. In the delay period, differences in ERP components and frontal theta ERD were observed. Meanwhile, at retrieval, P3 amplitude and latency, as well as the theta band were modulated by both process (Mt or Mp) and type of trial (target or non-target stimuli). These findings mainly suggest different attentional implications at encoding, differences at the delay period related with task difficulty, and differential retrieval for Mt or Mp dependent on the process which the information comes from, suggesting that Mt and Mp differ at the very beginning of the processing.     

Event-related EEG oscillations to semantically unrelated words in normal and learning disabled children

Learning disabilities (LD) are one of the most frequent problems for elementary school-aged children. In this paper, event-related EEG oscillations to semantically related and unrelated pairs of words were studied in a group of 18 children with LD not otherwise specified (LD-NOS) and in 16 children with normal academic achievement. We propose that EEG oscillations may be different in LD NOS children versus normal control children that may explain some of the deficits observed in the LD-NOS group. The EEGs were recorded using the 10/20 system. EEG segments were edited by visual inspection 1000ms before and after the stimulus, and only correct responses were considered in the analysis. Time-frequency (1-50Hz) topographic maps were obtained for the increases and decreases of power after the event with respect to the pre-stimulus average values. Significant differences between groups were observed in the behavioral responses. LD-NOS children show less number of correct responses and more omissions and false alarms than the control group. The event-induced EEG responses showed significant differences between groups. The control group showed greater power increases in the frequencies 1-6Hz than the LD-NOS group from 300 to 700ms. These differences were mainly observed in frontal regions, both to related and non-related words. This was interpreted as a deficit in attention, both to internal and external events, deficits in activation of working memory and deficits in encoding and memory retrieval in the LD-NOS children. Differences between groups were also observed in the suppression of alpha and beta rhythms in the occipital regions to related words in frequencies between 8 and 17Hz from 450 to 750ms. LD-NOS children showed shorter durations of the decreases in power than the control group. These results suggest also deficits in attention and memory retrieval. It may be concluded that LD-NOS children showed physiological differences from normal children that may explain their cognitive deficiencies.     

The Neural Basis of Selective Attention: Cortical Sources and Targets of Attentional Modulation

ABSTRACT— Selective attention is an intrinsic component of perceptual representation in a visual system that is hierarchically organized. Modulatory signals originate in brain regions that represent behavioral goals; these signals specify which perceptual objects are to be represented by sensory neurons that are subject to contextual modulation. Attention can be deployed to spatial locations, features, or objects, and corresponding modulatory signals must be targeted within these domains. Open questions include how nonspatial perceptual domains are modulated by attention and how abstract goals are transformed into targeted modulatory signals.     

A further note on freeman's measure of association

This note extends and elaborates Hubert's attempt to provide an interpretation of Freeman's measure of association,. The measure is used in a a contingency table when observations are ordered on one variable and unordered on the other. No attempt is made explore the distribution of.