Journal of Cognitive Neuroscience最新文献

Prior studies examining the neural mechanisms underlying retrieval success and precision have yielded inconsistent results. Here, the neural correlates of success and precision were examined with a memory task that assessed precision for spatial location. A sample of healthy young adults underwent functional magnetic resonance imaging scanning during a single study-test cycle. At study, participants viewed a series of object images, each placed at a randomly selected location on an imaginary circle. At test, studied images were intermixed with new images and presented to the participants. The requirement was to move a cursor to the location of the studied image, guessing if necessary. Participants then signaled whether the presented image had been studied. Memory precision was quantified as the angular difference between the studied location and the location selected by the participant. A precision effect was evident in the left angular gyrus, where BOLD activity covaried with location accuracy. In addition, multivoxel pattern analysis revealed a significant item-level reinstatement effect in the angular gyrus for high-precision trials. There was no evidence of a retrieval success effect in this region. BOLD activity in the hippocampus was insensitive to both success and precision. These findings are partially consistent with prior evidence that success and precision are dissociable features of memory retrieval.

Survival in dynamic environments requires that organisms learn to predict danger from situational cues. One key facet of threat prediction is generalization from a predictive cue to similar cues, ensuring that a cue-outcome contingency is applied beyond the original learning environment. Generalization has been observed in laboratory studies of aversive conditioning: Behavioral and physiological processes generalize responses from a stimulus paired with threat (the conditioned stimulus [CS+]) to unpaired stimuli, with response magnitudes varying with CS+ similarity. In contrast, work focusing on sensory responses in visual cortex has found a sharpening pattern, in which responses to stimuli closely resembling the CS+ are maximally suppressed, potentially reflecting lateral inhibitory interactions with the CS+ representation. Originally demonstrated with simple visual cues, changes in visuocortical tuning have also been observed in threat generalization learning across facial identities. It is unclear to what extent these visuocortical changes represent transient or sustained effects and if generalization learning requires prior conditioning to the CS+. The present study addressed these questions using EEG and pupillometry in an aversive generalization paradigm involving hundreds of trials using a gradient of facial identities. Visuocortical steady-state visual evoked potential sharpening occurred after dozens of trials of generalization learning without prior differential conditioning, but diminished as learning continued. By contrast, generalization of alpha power suppression, pupil dilation, and self-reported valence and arousal was seen throughout the experiment. Findings are consistent with threat processing models emphasizing the role of changing visucocortical and attentional dynamics when forming, curating, and shaping fear memories as observers continue learning about stimulus-outcome contingencies.

The dual-stream model of speech processing describes a cortical network involved in speech processing. However, it is not yet known if the dual-stream model represents actual intrinsic functional brain networks. Furthermore, it is unclear how disruptions after a stroke to the functional connectivity of the dual-stream model's regions are related to speech production and comprehension impairments seen in aphasia. To address these questions, in the present study, we examined two independent resting-state fMRI data sets: (1) 28 neurotypical matched controls and (2) 28 chronic left-hemisphere stroke survivors collected at another site. We successfully identified an intrinsic functional network among the dual-stream model's regions in the control group using functional connectivity. We then used both standard functional connectivity analyses and graph theory approaches to determine how this connectivity may predict performance on clinical aphasia assessments. Our findings provide evidence that the dual-stream model of speech processing is an intrinsic network as measured via resting-state MRI and that functional connectivity of the hub nodes of the dual-stream network defined by graph theory methods, but not overall average network connectivity, is weaker in the stroke group than in the control participants. In addition, the functional connectivity of the hub nodes predicted linguistic impairments on clinical assessments. In particular, the relative strength of connectivity of the right hemisphere's homologues of the left dorsal stream hubs to the left dorsal hubs, versus to the right ventral stream hubs, is a particularly strong predictor of poststroke aphasia severity and symptomology.

Dual tasks (DTs) require additional control processes that temporally coordinate the processing of the two component tasks. Previous studies employing imaging as well as noninvasive stimulation techniques have demonstrated that the dorsolateral prefrontal cortex (dlPFC) is causally involved in these task-order coordination processes. However, in these studies, participants were instructed to match their processing order to an externally provided and mandatory order criterion during DT processing. Hence, it is still unknown whether the dlPFC is also recruited for rather voluntary order control processes, which are required in situations that allow for intentional and internally generated order choices. To address this issue, in two experiments, we applied anodal (Experiment 1) and cathodal (Experiment 2) transcranial direct-current stimulation during a random-order DT in which participants could freely decide about their order of task processing. In our results, we found facilitatory and inhibitory effects on voluntary task-order coordination because of anodal and cathodal transcranial direct-current stimulation, respectively. This was indicated by shorter RTs when participants intentionally switched the task order relative to the preceding trial during anodal as well as a reduced tendency to switch the task order relative to the preceding trial during cathodal stimulation compared with the sham stimulation. Overall, these findings indicate that the dlPFC is also causally involved in voluntary task-order coordination processes. In particular, we argue that the dlPFC is recruited for intentionally updating and implementing task-order information that is necessary for scheduling the processing of two temporally overlapping tasks.

Despite the growing interest in the study of attentional refreshing, the functioning of this working memory maintenance mechanism, including its cerebral underpinnings, is still debated. In particular, it remains unclear whether refreshing promotes long-term memory and whether it, in return, depends on long-term memory content to operate. Here, we used direct maintenance instructions and measured brain activity to investigate working memory maintenance with two objectives: (1) test if different behavioral and oscillatory patterns could be observed when participants were instructed to use attentional refreshing versus verbal rehearsal, and (2) observe whether and how refreshing is modulated when maintaining novel (pseudowords) versus familiar (words) memoranda. We conducted an EEG experiment using a modified Brown-Peterson task, in which we manipulated the type of maintenance engaged through explicit instructions (verbal rehearsal vs. refreshing), the type of memoranda (words vs. pseudowords), and the memory load (2 vs. 6). Using scalp EEG, we measured both neural oscillations during working memory maintenance and ERPs during the concurrent parity judgment task. For words, we showed that verbal rehearsal benefited more short-term recall whereas refreshing benefited more delayed recall. In keeping with these behavioral differences between maintenance instructions, frontal-midline theta power increased with memory load only when using verbal rehearsal, whereas occipito-parietal alpha desynchronization was larger with refreshing than verbal rehearsal. When maintaining pseudowords, verbal rehearsal also benefitted short-term recall more than refreshing. However, no long-term memory benefit of refreshing was observed for pseudowords, and oscillatory activity was not different under the two maintenance instructions. Our results provide new evidence supporting the independence between attentional refreshing and verbal rehearsal, and bring new insight into refreshing functioning. We discuss the possible interpretations of these results and the implications for the attentional refreshing literature.

To test whether targeting left and right posterior parietal cortex (PPC) with continuous theta-burst stimulation (cTBS) in healthy adults would strengthen associative memory (AM) performance. This study consisted of two experiments (a behavioral experiment and a formal experiment during each of the two experimental sessions). In Experiment 1, 18 adults (one male, age = 22.83 ± 3.92 years) were included in the behavioral phase and 18 adults (seven males, age = 40.11 ± 12.27 years) in the stimulation phase. There were 120 neutral facial images paired with 120 two-character nouns and then divided into six test versions (10 male faces and 10 female faces paired with 20 different nouns were considered as one version). In the behavioral experiment, participants were tested by six-version tests to assess memory materials, and in the formal experiment, participants' face-word AM performance was measured by certified tests based on a cued recall paradigm. Furthermore, 30 adults (seven males, age = 20.97 ± 1.85 years) and 15 adults (five males, age = 22.27 ± 1.29 years) participated in Experiment 2, respectively. Stimuli and procedure were the same as in Experiment 1, but the AM test was based on a forced-choice paradigm. Experiment 1 did not yield anticipated outcomes; Experiment 2 showed that cTBS of left and right PPC strengthened the AM performance compared with the control condition. In conclusion, cTBS to left and right PPC improved AM in healthy adults, which provided further experimental evidence for strengthening AM by cTBS.

There is an extensive body of research showing a significant relationship between frontal midline theta activity in the 4- to 8-Hz range and working memory (WM) performance. Transcranial alternating current stimulation (tACS) is recognized for inducing lasting changes in brain oscillatory activity. Across two experiments, we tested whether WM could be improved through tACS of dorsomedial pFC and ACC, by affecting executive control networks associated with frontal midline theta. In Experiment 1, after either a 20-min verum or sham stimulation applied to Fpz-CPz at 1 mA and 6 Hz, 31 participants performed WM tasks, while EEG was recorded. The tasks required participants to either mentally manipulate memory items or retain them in memory as they were originally presented. No significant effects were observed in behavioral performance, and we found no change in theta activity during rest and task after stimulation. However, alpha activity during retention or manipulation of information in WM was less strongly enhanced during the delay period after verum stimulation as compared with sham. In Experiment 2 (n = 25), tACS was administered during the task in two separate sessions. Here, we changed the order of the stimulation blocks: A 25-min task block was either accompanied first by sham stimulation and then by verum stimulation, or vice versa. Again, we found no improvements in WM through either tACS after-effects or online stimulation. Taken together, our results demonstrate that theta frequency tACS applied at the midline is not an effective method for enhancing WM.

Behavioral parameters obtained from cognitive control tasks have been linked to electrophysiological markers. Yet, most previous research has investigated only a few specific behavioral parameters at a time. An integrated approach with simultaneous consideration of multiple aspects of behavior may better elucidate the development and function of cognitive control. Here, we aimed to identify shared patterns between cognitive control behavior and electrophysiological markers using stop-signal task data and EEG recordings from an adolescent sample (n = 193, aged 11-25 years). We extracted behavioral variables covering various aspects of RT, accuracy, inhibition, and decision-making processes, as well as amplitude and latency of the ERPs N1, N2, and P3. To identify shared patterns between the two sets of variables, we employed a principal component analysis and a canonical correlation analysis. First, we replicated previously reported associations between various cognitive control behavioral parameters. Next, results from the canonical correlation analysis showed that overall good task performance was associated with fast and strong neural processing. Furthermore, the canonical correlation was affected by age, indicating that the association varies depending on age. The present study suggests that although distributional and computational methods can be applied to extract specific behavioral parameters, they might not capture specific patterns of cognitive control or electrophysiological brain activity in adolescents.

Attentional mechanisms are the primary processes for performing working memory (WM) tasks and can prevent distractors from interfering with the content representations stored in WM. However, our understanding of the mechanisms by which attention affects WM remains limited. As such, we analyzed ERPs of the character n-back task to investigate Chinese character selection, updating, and maintenance in WM. In Experiment 1, we collected electroencephalography data from 27 participants aged 18-25 years to explore the influence of false-character interference and symbol interference on a neural activity in the character n-back task. The results suggest that RT was longer in the false-character interference condition. The N2pc and P300 amplitudes were smaller; however, the slow wave amplitude did not differ significantly. In Experiment 2, we used a single-symbol interference and a multiple-symbol interference to establish whether the number of interferences affected the neural activity in the character n-back task. Thirty participants (aged 19-25 years) took part in the experiment. The findings imply that a longer RT and a larger N2pc amplitude occurred in the multiple-symbol interference condition, but not in the P300 and slow wave conditions. Our findings indicate that distractors that are similar to characters may produce greater interference in character recognition and affect the subsequent updating, whereas the number of distractors may only interfere with early character selection, but not with updating and maintenance phases.

Optogenetics affords new opportunities to interrogate neuronal circuits that control behavior. In primates, the usefulness of optogenetics in studying cognitive functions remains a challenge. The technique has been successfully wielded, but behavioral effects have been demonstrated primarily for sensorimotor processes. Here, we tested whether brief optogenetic suppression of primate superior colliculus can change performance in a covert attention task, in addition to previously reported optogenetic effects on saccadic eye movements. We used an attention task that required the monkey to detect and report a stimulus change at a cued location via joystick release, while ignoring changes at an uncued location. When the cued location was positioned in the response fields of transduced neurons in the superior colliculus, transient light delivery coincident with the stimulus change disrupted the monkey's detection performance, significantly lowering hit rates. When the cued location was elsewhere, hit rates were unaltered, indicating that the effect was spatially specific and not a motor deficit. Hit rates for trials with only one stimulus were also unaltered, indicating that the effect depended on selection among distractors rather than a low-level visual impairment. Psychophysical analysis revealed that optogenetic suppression increased perceptual threshold, but only for locations matching the transduced site. These data show that optogenetic manipulations can cause brief and spatially specific deficits in covert attention, independent of sensorimotor functions. This dissociation of effect, and the temporal precision provided by the technique, demonstrates the utility of optogenetics in interrogating neuronal circuits that mediate cognitive functions in the primate.