Cognitive Brain Research最新文献

The ability to identify and respond to significant events in the environment is a vital aspect of human cognition and yet is poorly understood as a dynamic neural process. While the response to a contextually-relevant stimulus involves a number of complimentary processes, including selective attention and neural binding, it is also subject to modulation by factors like arousal, age and sex. Adopting an integrative approach, we investigated contextual processing (as indexed by P3b and Gamma phase synchrony) in 120 healthy subjects performing an auditory oddball task while controlling for these other modulating factors. Results suggest a relationship between P3b and Gamma-2 synchrony in posterior regions only, with phasic anterior processing seemingly unrelated to that in posterior regions. However, only the P3b was significantly correlated to central and autonomic arousal. Further, while age and sex were associated with variation in individual measures, they did not strongly affect the relationship between the measures. We concluded that, in simple contextual processing, global and local elements of target stimuli are processed in parallel with little variation being shown between the sexes or resulting from increasing age.

Game theory provides a solution to the problem of finding a set of optimal decision-making strategies in a group. However, people seldom play such optimal strategies and adjust their strategies based on their experience. Accordingly, many theories postulate a set of variables related to the probabilities of choosing various strategies and describe how such variables are dynamically updated. In reinforcement learning, these value functions are updated based on the outcome of the player's choice, whereas belief learning allows the value functions of all available choices to be updated according to the choices of other players. We investigated the nature of learning process in monkeys playing a competitive game with ternary choices, using a rock–paper–scissors game. During the baseline condition in which the computer selected its targets randomly, each animal displayed biases towards some targets. When the computer exploited the pattern of animal's choice sequence but not its reward history, the animal's choice was still systematically biased by the previous choice of the computer. This bias was reduced when the computer exploited both the choice and reward histories of the animal. Compared to simple models of reinforcement learning or belief learning, these adaptive processes were better described by a model that incorporated the features of both models. These results suggest that stochastic decision-making strategies in primates during social interactions might be adjusted according to both actual and hypothetical payoffs.

This study shows that the exact spatial location of a distractor can have a modulatory influence on saccade trajectories. Distractors close to the target evoke saccade trajectories that are directed towards the distractor, while distractors close to fixation result in saccades that are directed away from the distractor. This finding questions the idea that target positions are coarsely coded in the superior colliculus.

We present two ERP experiments examining the resolution of language processing conflicts involving the multidimensional linguistic feature case, which determines processing in both syntactic and interpretive respects. Ungrammatical German structures with two identically case-marked arguments (double subject or double object constructions) were tested. In earlier studies, double subject constructions have been shown to elicit a biphasic pattern consisting of an N400 effect (a marker of thematic integration problems) followed by a P600 effect (a marker of syntactic ill-formedness). Here, we compare double nominative (subject case) constructions with double datives (indirect object case; Experiment 1) and double accusatives (direct object case; Experiment 2). All types of double case ungrammaticalities elicited a biphasic N400–P600 response. However, double datives differed from double nominatives in that they elicited a larger P600, suggesting that the ill-formedness is more salient in structures with two dative arguments. Double accusatives, by contrast, elicited a stronger N400 in comparison to double nominatives, suggesting that they induce more severe semantic–thematic integration problems. The results demonstrate that the human language comprehension system is sensitive to fine grained linguistic distinctions between different cases and utilizes these in its attempts to solve processing conflicts.

An EEG coherence study was performed with a twofold objective: first, to scrutinize the theoretical concept of “cortical efficiency” in connection with second language (L2) acquisition and, second, to detect cooperations between cortical areas in specific frequency bands indicative for highly proficient L2 processing. Two groups differing only in their level of L2 proficiency were contrasted during presentation of natural language videos in English (L2) and German (native language, L1), with explorative coherence analysis in 6 frequency bands (0.5–31.5 Hz). The coherence brain maps revealed more pronounced and widespread increases in coherences in the α1-band (8–10 Hz) in low-proficiency than in the high-proficiency L2 speakers. Surprisingly, this difference was obtained also during L1 processing and corroborated for both languages by multivariate permutation tests. These tests revealed additional differences between the low- and the high-proficiency group also for coherences within the β1- (13–18 Hz) and the β2-band (18.5–31.5 Hz), again during L2 and L1 processing. Since the same group differences were observed during L1 and L2 processing, our high-proficiency group might have profited from a more generic advantage in language or text processing strategy. This strategic advantage was most evident at α1 frequencies, possibly related to a specific way of processing internal mental states (top-down processing).

Previous studies have found that the P2 component of the auditory event-related potential (ERP) increases after speech discrimination training. We compared electrophysiological and behavioral outcomes of individuals undergoing speech discrimination training (N = 8) with an untrained control group (N = 9). Significant improvements on the behavioral speech discrimination task were found only in the trained group; however, there were similar increases in P2 amplitude in both groups. Simple exposure to repeated instances of a speech sound during the ERP recording seems sufficient lead to enhancement of P2. This interpretation was bolstered by the finding of significant change in P2 during the first and second halves of the initial ERP recording, when listeners were not required to make any discriminative response. However, the largest change in P2 occurred between rather than within recording sessions, suggesting that the effects of exposure to a speech stimulus on ERPs may have a slow time-course and are most evident after a delay. Our data challenge the view that increased P2 amplitude reflects enhanced perceptual discrimination by auditory cortex.

We suggest a united concept of consciousness and emotion, based on the systemic cognitive neuroscience perspective regarding organisms as active and goal-directed. We criticize the idea that consciousness and emotion are psychological phenomena having quite different neurophysiological mechanisms. We argue that both characterize a unified systemic organization of behavior, but at different levels. All systems act to achieve intended behavioral results in interaction with their environment. Differentiation of this interaction increases during individual development. Any behavioral act is a simultaneous realization of systems ranking from the least to the most differentiated. We argue that consciousness and emotion are dynamic systemic characteristics that are prominent at the most and least differentiated systemic levels, correspondingly. These levels are created during development. Our theory is based on both theoretical and empirical research and provides a solid framework for experimental work.

Working memory is thought to involve separate modality-specific storage systems. Interactions between these storage systems were investigated using a novel cross-modal 2-back paradigm. 2-back, 1-back and target items were presented either visually as a verbalizable linedrawing or auditorily as a digitized spoken word. ERPs for auditory targets were primarily modulated by the presentation modality of the 2-back item, whereas ERPs for visual targets were largely modulated by presentation modality of the 1-back item. Results indicate that verbalizable pictures are only partially transformed into a phonological code for rehearsal in working memory. Furthermore, results support the idea of a more stable and persistent auditory short-term store as opposed to a more transiently activated visual store for verbalizable material.

We examined whether monitoring asynchronous audiovisual speech induces a general temporal recalibration of auditory and visual sensory processing. Participants monitored a videotape featuring a speaker pronouncing a list of words (Experiments 1 and 3) or a hand playing a musical pattern on a piano (Experiment 2). The auditory and visual channels were either presented in synchrony, or else asynchronously (with the visual signal leading the auditory signal by 300 ms; Experiments 1 and 2). While performing the monitoring task, participants were asked to judge the temporal order of pairs of auditory (white noise bursts) and visual stimuli (flashes) that were presented at varying stimulus onset asynchronies (SOAs) during the session. The results showed that, while monitoring desynchronized speech or music, participants required a longer interval between the auditory and visual stimuli in order to perceive their temporal order correctly, suggesting a widening of the temporal window for audiovisual integration. The fact that no such recalibration occurred when we used a longer asynchrony (1000 ms) that exceeded the temporal window for audiovisual integration (Experiment 3) supports this conclusion.

To investigate the impact of spatial frequency on emotional facial expression analysis, ERPs were recorded in response to low spatial frequency (LSF), high spatial frequency (HSF), and unfiltered broad spatial frequency (BSF) faces with fearful or neutral expressions, houses, and chairs. In line with previous findings, BSF fearful facial expressions elicited a greater frontal positivity than BSF neutral facial expressions, starting at about 150 ms after stimulus onset. In contrast, this emotional expression effect was absent for HSF and LSF faces. Given that some brain regions involved in emotion processing, such as amygdala and connected structures, are selectively tuned to LSF visual inputs, these data suggest that ERP effects of emotional facial expression do not directly reflect activity in these regions. It is argued that higher order neocortical brain systems are involved in the generation of emotion-specific waveform modulations. The face-sensitive N170 component was neither affected by emotional facial expression nor by spatial frequency information.