Affective picture processing: Alpha‐ and lower beta‐band desynchronization reflects emotional arousal

EEG power analysis is firmly established in the cognitive domain. This contrasts with emotional stimulus processing, which thus far has yielded a complex and ambiguous pattern of findings. To further advance understanding, the present study examined emotional stimulus processing in the context of task variations and baseline activity, which included several manipulation checks as well as internal replication of findings across conditions. Participants (N = 16) viewed erotic and romantic pictures, differing in stimulus arousal. Pictures were presented briefly (120 ms), and intertrial interval was systematically varied (~1 vs. ~8 s). In one condition, participants passively viewed the pictures, in the other, they performed an active picture categorization task. The processing of erotic compared to romantic images was associated with a decrease in power in the alpha and lower beta band in posterior and anterior sensor clusters between 600–1,000 ms poststimulus. The finding was robust and confirmed across conditions, different quantifications, and independent from baseline activity. Furthermore, key findings regarding explicit task effects as well as ERPs sensitive to emotional arousal were replicated. Results are discussed with respect to the hypothesis that alpha‐ and lower beta‐band activity may reflect cortical activation associated with emotional stimulus significance.     

Alpha‐power modulation reflects the balancing of task requirements in a selective attention task

Recent research has related the orienting of selective attention to the lateralization of posterior EEG alpha power (∼8 to 12 Hz). Typically, alpha power decreases over the side of the head contralateral to the cued side of space. However, it is not clear how this lateralization affects behavior. We recorded EEG from 20 participants while they performed a cued visual discrimination task under three different response‐deadline conditions to investigate the effect of alpha‐power modulation on behavioral performance in more detail. Although all participants benefited from the cue behaviorally and adjusted their performance according to the response deadlines, we found the cue‐related alpha‐power modulation to depend on the general alpha‐power level at baseline: Only participants with high baseline alpha power showed significant cue‐related alpha‐power lateralization that was, however, strikingly similar across response‐deadline conditions. On the other hand, participants with low alpha power at baseline did not show any lateralization, but adjusted their alpha levels according to the response‐deadline instructions and, more importantly, showed a stronger influence of the task instructions on behavioral performance and adapted their response accuracies to the task requirements more flexibly. These findings challenge the often‐assumed role of alpha‐power lateralization for attentional deployment. While alpha power seems to be related to behavioral performance and the orienting of attention, this relationship is rather complex and, at least under the current task requirements, the general alpha‐power state seems to be more strongly related to behavioral performance (in our case, the flexible adjustment to task requirements) than the cue‐related lateralization.     

Verbal working memory‐related neural network communication in schizophrenia

Impaired working memory (WM) in schizophrenia is associated with reduced hemodynamic and electromagnetic activity and altered network connectivity within and between memory‐associated neural networks. The present study sought to determine whether schizophrenia involves disruption of a frontal‐parietal network normally supporting WM and/or involvement of another brain network. Nineteen schizophrenia patients (SZ) and 19 healthy comparison subjects (HC) participated in a cued visual‐verbal Sternberg task while dense‐array EEG was recorded. A pair of item arrays each consisting of 2–4 consonants was presented bilaterally for 200 ms with a prior cue signaling the hemifield of the task‐relevant WM set. A central probe letter 2,000 ms later prompted a choice reaction time decision about match/mismatch with the target WM set. Group and WM load effects on time domain and time‐frequency domain 11–15 Hz alpha power were assessed for the cue‐to‐probe time window, and posterior 11–15 Hz alpha power and frontal 4–8 Hz theta power were assessed during the retention period. Directional connectivity was estimated via Granger causality, evaluating group differences in communication. SZ showed slower responding, lower accuracy, smaller overall time‐domain alpha power increase, and less load‐dependent alpha power increase. Midline frontal theta power increases did not vary by group or load. Network communication in SZ was characterized by temporal‐to‐posterior information flow, in contrast to bidirectional temporal‐posterior communication in HC. Results indicate aberrant WM network activity supporting WM in SZ that might facilitate normal load‐dependent and only marginally less accurate task performance, despite generally slower responding.     

Bion,Alpha‐Function and the Unconscious Mind

This paper will identify why and how Bion's ideas about dream‐work and alpha‐function evolved, and the profound implications of this development for what he calls ‘practical psychoanalysis’. Andre Green interestingly comments that for Bion the ‘model of the dream’ was unusually more important than the ‘model of the baby’; and I will consider in particular the question of ‘models’, and their relation to the making of the accurate observations of unconscious functioning we need to underpin our analytic work. It is hoped the paper will contribute to the clinically relevant question of whether there is an important link between Bion's ‘alpha‐function’ and mentalization theory.     

Sleep deprivation compromises resting‐state emotional regulatory processes: An EEG study

Resting‐state spontaneous neural activities consume far more biological energy than stimulus‐induced activities, suggesting their significance. However, existing studies of sleep loss and emotional functioning have focused on how sleep deprivation modulates stimulus‐induced emotional neural activities. The current study aimed to investigate the impacts of sleep deprivation on the brain network of emotional functioning using electroencephalogram during a resting state. Two established resting‐state electroencephalogram indexes (i.e. frontal alpha asymmetry and frontal theta/beta ratio) were used to reflect the functioning of the emotion regulatory neural network. Participants completed an 8‐min resting‐state electroencephalogram recording after a well‐rested night or 24 hr sleep deprivation. The Sleep Deprivation group had a heightened ratio of the power density in theta band to beta band (theta/beta ratio) in the frontal area than the Sleep Control group, suggesting an affective approach with reduced frontal cortical regulation of subcortical drive after sleep deprivation. There was also marginally more left‐lateralized frontal alpha power (left frontal alpha asymmetry) in the Sleep Deprivation group compared with the Sleep Control group. Besides, higher theta/beta ratio and more left alpha lateralization were correlated with higher sleepiness and lower vigilance. The results converged in suggesting compromised emotional regulatory processes during resting state after sleep deprivation. Our work provided the first resting‐state neural evidence for compromised emotional functioning after sleep loss, highlighting the significance of examining resting‐state neural activities within the affective brain network as a default functional mode in investigating the sleep–emotion relationship.     

Brain oscillation and connectivity during a chemistry visual working memory task

Many studies have reported that frontal theta and posterior alpha activities are associated with working memory tasks. However, fewer studies have focused on examining whether or not the frontal alpha or posterior theta can play a role in the working memory task. This study investigates electroencephalography (EEG) dynamics and connectivity among different brain regions' theta and alpha oscillations. The EEG was collected from undergraduate students (n = 64) while they were performing a Sternberg-like working memory task involving chemistry concepts. The results showed that the frontal midline cluster exhibited sustained theta augmentation across the periods of stimulus presentations, maintenance, and probe presentation, suggesting that the frontal midline theta might associate with facilitating the central execute function to maintain information in the working memory. Study of the central parietal and the occipital clusters revealed a sequence of theta augmentation followed by alpha suppression at constant intervals after the onset of stimulus and probe presentations, suggesting that the posterior theta might be associated with sensory processing, theta gating, or stimulus selection. It further suggests that the posterior alpha event-related de-synchronization (ERD) might be linked to direct information flow into and out of the long-term memory (LTM) and precede stimulus recognition. An alternating phasic alpha event-related synchronization (ERS) and ERD following the 1st stimulus and probe presentations were observed at the occipital cluster, in which alpha ERS might be linked to the inhibition of irrelevant information.     

Effects of mnemonic load on cortical activity during visual working memory: Linking ongoing brain activity with evoked responses

The mechanisms generating task-locked changes in cortical potentials remain poorly understood, despite a wealth of research. It has recently been proposed that ongoing brain oscillations are not symmetric, so that task-related amplitude modulations generate a baseline shift that does not average out, leading to slow event-related potentials. We test this hypothesis using multivariate methods to formally assess the co-variation between task-related evoked potentials and spectral changes in scalp EEG during a visual working memory task, which is known to elicit both evoked and sustained cortical activities across broadly distributed cortical regions. 64-channel EEG data were acquired from eight healthy human subjects who completed a visuo-spatial associative working memory task as memory load was parametrically increased from easy to hard. As anticipated, evoked activity showed a complex but robust spatio-temporal waveform maximally expressed bilaterally in the parieto-occipital and anterior midline regions, showing robust effects of memory load that were specific to the stage of the working memory trial. Similarly, memory load was associated with robust spectral changes in the theta and alpha range, throughout encoding in posterior regions and through maintenance and retrieval in anterior regions, consistent with the additional resources required for decision making in prefrontal cortex. Analysis of the relationship between event-related changes in slow potentials and cortical rhythms, using partial least squares, is indeed consistent with the notion that the former make a causal contribution to the latter.     

Auditory‐visual integration modulates location‐specific repetition suppression of auditory responses

Space is a dimension shared by different modalities, but at what stage spatial encoding is affected by multisensory processes is unclear. Early studies observed attenuation of N1/P2 auditory evoked responses following repetition of sounds from the same location. Here, we asked whether this effect is modulated by audiovisual interactions. In two experiments, using a repetition‐suppression paradigm, we presented pairs of tones in free field, where the test stimulus was a tone presented at a fixed lateral location. Experiment 1 established a neural index of auditory spatial sensitivity, by comparing the degree of attenuation of the response to test stimuli when they were preceded by an adapter sound at the same location versus 30° or 60° away. We found that the degree of attenuation at the P2 latency was inversely related to the spatial distance between the test stimulus and the adapter stimulus. In Experiment 2, the adapter stimulus was a tone presented from the same location or a more medial location than the test stimulus. The adapter stimulus was accompanied by a simultaneous flash displayed orthogonally from one of the two locations. Sound‐flash incongruence reduced accuracy in a same‐different location discrimination task (i.e., the ventriloquism effect) and reduced the location‐specific repetition‐suppression at the P2 latency. Importantly, this multisensory effect included topographic modulations, indicative of changes in the relative contribution of underlying sources across conditions. Our findings suggest that the auditory response at the P2 latency is affected by spatially selective brain activity, which is affected crossmodally by visual information.     

Applying computational modeling to assess age‐, sex‐, and strategy‐related differences in Spin the Pots,a working memory task for 2‐ to 4‐year‐olds

Working memory (WM) develops rapidly during early childhood. In the present study, visual WM (VSM) was measured using the well‐established Spin the Pots task (Hughes & Ensor, 2005), a complex non‐verbal eight‐location object occlusion task. A self‐ordered hiding procedure was adopted to allow for an examination of children's strategy use during a VWM task. Participants (N = 640) between the ages of 2 and 4 years were tested under semi‐naturalistic conditions, in the home or in a museum. Computational modeling was used to estimate an expected value for the total trials to complete Spin the Pots via a random search and child performance was compared to expected values. Based on this approach, we determined that children who found six stickers retrieved them in significantly fewer trials than the expected value, excluding chance performance and implicating VWM. Results also showed age‐related and sex‐related changes in VWM. Between 2 and 4 years of age, 4‐year‐olds performed significantly better than younger children and girls out‐performed the boys. Spontaneous use of a color matching hiding strategy was associated with a higher success rate on the task. Implications of these findings for early development of VWM are discussed.     

Nicotine receptor gene CHRNA4 modulates early event-related potentials in auditory and visual oddball target detection tasks

The present study seeks to identify effects of a common genetic polymorphism in the human nicotinic alpha4beta2 receptor on components of the cognitive event-related potentials in auditory and visual modalities. The same sense thymine-to-cytosine polymorphism (c.1629T-C; Ser543Ser) was shown to preferentially modulate early components in both modalities. Specifically, the auditory N1 component amplitude was higher for T allele homozygotes than for C allele carriers. The visual P1 component revealed the same pattern of significant polymorphic modulation, but the later N1 amplitude differences were only marginally significant. There was no reliable indication of interactions between genotype and task factors. Parallel modulation of early latency modality-specific event-related potential (ERP) components in vision and audition may indicate that the CHRNA4 polymorphism affects factors that are common to top-down modulation of sensory processing across modalities.     

Neural measures of working memory in a bilateral change detection task

The change detection task is a widely used paradigm to examine visual working memory processes. Participants memorize a set of items and then, try to detect changes in the set after a retention period. The negative slow wave (NSW) and contralateral delay activity (CDA) are event‐related potentials in the EEG signal that are commonly used in change detection tasks to track working memory load, as both increase with the number of items maintained in working memory (set size). While the CDA was argued to more purely reflect the memory‐specific neural activity than the NSW, it also requires a lateralized design and attention shifts prior to memoranda onset, imposing more restrictions on the task than the NSW. The present study proposes a novel change detection task in which both CDA and NSW can be measured at the same time. Memory items were presented bilaterally, but their distribution in the left and right hemifield varied, inducing a target imbalance or “net load.” NSW increased with set size, whereas CDA increased with net load. In addition, a multivariate linear classifier was able to decode the set size and net load from the EEG signal. CDA, NSW, and decoding accuracy predicted an individual's working memory capacity. In line with the notion of a bilateral advantage in working memory, accuracy, and CDA data suggest that participants tended to encode items relatively balanced. In sum, this novel change detection task offers a basis to make use of converging neural measures of working memory in a comprehensive paradigm.     

Electrophysiological correlates of hyperoxia during resting‐state EEG in awake human subjects

Recreational use of concentrated oxygen has increased. Claims have been made that hyperoxic breathing can help reduce fatigue, increase alertness, and improve attentional capacities; however, few systematic studies of these potential benefits exist. Here, we examined the effects of short‐term (15 min) hyperoxia on resting states in awake human subjects by measuring spontaneous EEG activity between normoxic and hyperoxic situations, using a within‐subject design for both eyes‐opened and eyes‐closed conditions. We also measured respiration rate, heart rate, and blood oxygen saturation levels to correlate basic physiological changes due to the hyperoxic challenge with any brain activity changes. Our results show that breathing short‐term 100% oxygen led to increased blood oxygen saturation levels, decreased heart rate, and a slight, but nonsignificant, decrease in breathing rate. Changes of brain activity were apparent, including decreases in low‐alpha (7–10 Hz), high‐alpha (10–14 Hz), beta (14–30 Hz), and gamma (30–50 Hz) frequency ranges during eyes‐opened hyperoxic conditions. During eyes‐closed hyperoxia, increases in the delta (0.5–3.5 Hz) and theta (3.5–7 Hz) frequency range were apparent together with decreases in the beta range. Hyperoxia appeared to accentuate the decrease of low alpha and gamma ranges across the eyes‐opened and eyes‐closed conditions, suggesting that it modulated brain state itself. As decreased alpha during eyes‐opened conditions has been associated with increased attentional processing and selective attention, and increased delta and theta during eyes‐closed condition are typically associated with the initiation of sleep, our results suggest a state‐specific and perhaps opposing influence of short‐term hyperoxia.     

Spectral EEG characteristics during increases in the complexity of the context of cognitive activity

The spatial and frequency characteristics of cortical electrical activity were studied in healthy human subjects in two series of experiments involving solution of sequentially presented visual tasks. The first task was to assess the relative sizes of two circles and was identical in both series. In the first series, this was supplemented by a task consisting of recognition of pseudowords/words, presumptively also requiring predominant involvement of the ventral “what?” visual system. In the second series, the additional task (spatial localization of a target stimulus in a matrix of letters) was associated with the predominant involvement of the dorsal “where?” visual system. Cortical electrical activity immediately before presentation of pairs of tasks was analyzed. Measures of EEG spectral power in the frontal, central, occipital, and temporal areas of the cortex was subjected to dispersion analysis. The power of electrical potentials in the delta and beta1 frequency ranges was greater when both tasks were associated predominantly with activation of the ventral visual system (first series of experiments). Power in the occipital alpha rhythm was lesser in the left hemisphere in both series of experiments. The interaction of the “experimental series” and “hemisphere” factors was significant in the temporal areas for EEG activity in the alpha2 range, where the predominant involvement of the ventral visual system on solution of both tasks corresponded to greater asymmetry in the electrical oscillations in the rapid alpha2 rhythm and its neighboring beta1 range with greater desynchronization (lesser power) on the left side. Thus, the nature of the ongoing activity is reflected in the spatial-frequency characteristics of the “background” electrical activity of the cortex.     

EEG power changes reflect distinct mechanisms during long‐term memory retrieval

The roles of theta and alpha oscillations for long‐term memory (LTM) retrieval are still under debate. Both are modulated by LTM retrieval demands, but it is unclear what specific LTM functions they are related to. Here, different oscillatory correlates of LTM retrieval could be obtained for theta and alpha with a paradigm that is suited to monitor the activation of a varying number of material‐specific LTM representations. Both frequency bands responded parametrically to the number of retrieved items. However, only the alpha effect dissociated topographically for material type, indicating that the activation of material‐specific representations became systematically modulated. For theta, this effect was material‐unspecific with mid‐frontal topography. These results suggest that alpha is functionally related to the activation of stored information, whereas theta is a sign of retrieval‐related control processes.     

The role of the cognitive activity context in the conservatism of unconscious visual sets

Studiesin healthy adults were performed to compare measures of the rigidity of a verbal set in three series of experiments: in series 1, pseudowords were presented at the set-forming stage of the experiment, while common words were presented in the test stage; series 2 used the pseudoword/word conditions of series 1 with the additional task of identifying the position of a target stimulus in a matrix, requiring discrimination from other symbols in terms of two characteristics; in series 3, the pseudoword/word test was followed by an initial task consisting of identifying the matrix position of a target stimulus in conditions in which the need to discriminate was minimized. The results supported the hypothesis that the rigidity of a visual set depends on the cognitive activity context. This property is significantly dependent on the loading applied to working memory and the cognitive tasks solved by the subject, particularly the ratio of involvement of the ventral and dorsal visual systems in the cortical processing of sequentially acting verbal and non-verbal visual stimuli. The cognitive set paradigm serves as a model for experimental studies of the roles of the ventral and dorsal visual systems in organizing recognition functions. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 55, No. 5, pp. 633–638, September–October, 2005.     

Localization of Alpha‐Keratin and Beta‐Keratin (Corneous Beta Protein) in the Epithelium on the Ventral Surface of the Lingual Apex and Its Lingual Nail in the Domestic Goose (Anser Anser f. domestica) by Using Immunohistochemistry and Raman Microspectroscopy Analysis

The epithelium of the ventral surface of the apex of the tongue in most birds is specified by the presence of the special superficial layer called lingual nail. The aim of the present study is to determine the localization of the alpha‐keratin and beta‐keratin (corneous beta protein) in this special epithelium in the domestic goose by using immunohistochemistry staining and the Raman spectroscopy analysis. Due to lack of commercially available antibodies to detect beta‐keratin (corneous beta protein), the Raman spectroscopy was used as a specific tool to detect and describe the secondary structure of proteins. The immunohistochemical (IHC) detections reveal the presence of alpha‐keratin in all layers of the epithelium, but significant differences in the distribution of the alpha‐keratin in the epithelial layers appear. The staining reaction is stronger from the basal layer to the upper zone of the intermediate layer. The unique result is weak staining for the alpha‐keratin in the lingual nail. Applications of the Raman spectroscopy as a complementary method not only confirmed results of IHC staining for alpha‐keratin, but showed that this technique could be used to demonstrate the presence of beta‐keratin (corneous beta protein). Functionally, the localization of alpha‐keratin in the epithelium of the ventral surface of the lingual apex provides a proper scaffold for epithelial cells and promotes structural integrity, whereas the presence of beta‐keratin (corneous beta protein) in the lingual nail, described also as exoskeleton of the ventral surface of the apex, endures mechanical stress. Anat Rec, 300:1361–1368, 2017. © 2017 Wiley Periodicals, Inc.     

The elicitation of steady‐state visual evoked potentials during sleep

This study confirmed the hypothesis that it is possible to elicit SSVEPs through closed eyelids during NREM sleep. To test this hypothesis, SSVEP amplitudes were measured in eight subjects across two conditions of stimulation (stimulation on and stimulation off) and three brain states (waking, light sleep, and deep sleep). Results showed a significant interaction between stimulation and brain state. In particular, EEG activity at the frequency of stimulation was higher during both light sleep and deep sleep in the stimulation on condition than in the stimulation off condition. The fact that it is possible to elicit SSVEPs during sleep may provide a new way to study how SSVEPs are generated in the brain—one that might help resolve open questions such as identifying the SSVEP activation sequence or deciding if SSVEPs derive from evoked or oscillatory neural processes.     

An electrophysiological measure of visual short‐term memory capacity within and across hemifields

Recent electrophysiological research has identified a specific contralateral correlate of the contents of visual short‐term memory (VSTM). This posterior contralateral delay activity (CDA) persists during the retention period, and its amplitude is modulated by the number of items held at any one time. Here we show that, despite the contralateral nature of this activity, its amplitude is modulated by the number of objects from both hemifields. When objects from one side of the visual field are held in memory, CDA activity increased for arrays of one, two, and three objects, but stopped getting larger for arrays of four objects. However, when objects from both sides are memorized at the same time, CDA activity reached its asymptotic limit for arrays of two objects per side. These results suggest that, in spite of being contralaterally organized, VSTM is limited by the number of objects from both hemifields.     

The role of inhibition for working memory processes: ERP evidence from a short‐term storage task

Human working memory is the central unit for short‐term storage of information. In addition to the selection and adequate storage of relevant information, the suppression of irrelevant stimuli from the environment seems to be of importance for working memory processes. To learn more about the interplay of information uptake and inhibition of irrelevant information, the present study used ERP measures and a short‐term storage and retrieval task, in which pairs of either numbers or letters had to be compared. Random sequences of four stimuli (two numbers and two letters) were presented, with either the numbers or the letters being relevant for comparison. The analysis of ERPs to each of the four stimuli indicated more pronounced P2 and P3b amplitudes for relevant than irrelevant stimuli. In contrast, the N2 (reflecting inhibitory control) was only elicited by irrelevant stimuli. Moreover, the N2 amplitude of the second irrelevant stimulus was associated with behavioral performance, indicating the importance of inhibition of task‐irrelevant stimuli for working memory processes. In sum, the findings demonstrate the role of cognitive control mechanisms for protecting relevant contents in working memory against irrelevant information.