A neurocognitive model for short-term sensory and motor preparatory activity in humans

The purpose of this review is to present information from different experiments that supports the proposal that brain systems are able to predict, in a short-term interval, certain characteristics about the next incoming stimuli. This ability allows the subject to be ready for the stimuli and be more efficient in completing the required task. Evidence is presented from different sensory-motor experiments, such as the central cueing Posner paradigm; Contingent Negative Variation (E1-E2), spectral modulation during expectancy and Lateralized Readiness Potential during the first-order sequential effect. Some cases from motor experiments are also presented, such as express saccades, the manual gap paradigm and ocular smooth pursuit movements. All these data support a neurocognitive model that can be related to neuroanatomical structures whose connections have been well- established. In the final section, a possible algorithm that explains the selection of a preparatory set among the alternatives is discussed

Who is more prone to distraction? A simple test to evaluate the interference of emotional stimuli in females and males

In order to quantify gender differences in attentional capability depending on the presence of emotional stimuli, the effectiveness of responses to a target stimulus were analysed between groups. Fifty-two men and 52 women carried out two experiments based on the Eriksen flanker task. Half the participants were instructed to indicate the orientation of an arrow without flankers. The other half carried out the same task, but in this case the arrow was flanked by images with sexual or relaxing content. The study suggests that men are faster than women in discriminating the spatial orientation of a relevant stimulus, despite being more prone to distraction by adjacent stimuli. Regarding emotional interference, which is equivalent in both genders, it is higher for images with sexual content compared to those with relaxing content

Sequential P3 effects in a Posner’s spatial cueing paradigm: Trial-by-trial learning of the predictive value of the cue

The neurocognitive consequences of correct or incorrect spatial prediction in a sequential S1–S2 paradigm were assessed. Sequential dependence on previous trial outcome (valid or invalid) was assessed by late Event-Related Potentials (ERPs) and behavioural responses. Two different experiments were performed, situating the target in the vertical (Experiment 1) or in the horizontal (Experiment 2) meridian. RTs and late positivities (P3a and P3b) were recorded. ERPs showed that posterior positivity (probably a P3b) was greater in invalid–valid trials than in valid–valid trials but lower than in valid– invalid trials. However, at the frontal electrodes, late positivity (probably a P3a) only appeared in valid–invalid trials, indicating that invalid trials are analyzed as novel-like stimuli. The P3b results suggest trial-by-trial learning of the predictive value of the cue, which needs to be updated as indicated by the pattern of P3b amplitudes: valid–invalid > invalid–valid > valid–valid.Ministerio de Educación y Ciencia (España)Junta de Andalucí

Multiple evoked and induced alpha modulations in a visual attention task: Latency

Alpha event-related desynchronization (ERD) has been widely applied to understand the psychophysiological role of this band in cognition. In particular, a considerable number of publications have described spectral alterations in several pathologies using this time-frequency approach. However, ERD is not capable of specifically showing nonphase (induced) activity related to the presentation of stimuli. Recent studies have described an evoked and induced activity in the early phases (first 200 ms) of stimulus processing. However, scarce studies have analyzed induced and evoked modulations in longer latencies (>200 ms) and their potential roles in cognitive processing. The main goal of the present study was to analyze diverse evoked and induced modulations in response to visual stimuli. Thus, 58- channel electroencephalogram (EEG) was recorded in 21 healthy subjects during the performance of a visual attention task, and analyses were performed for both target and standard stimuli. The initial result showed that phase-locked and nonphase locked activities coexist in the early processing of target and standard stimuli as has been reported by previous studies. However, more modulations were evident in longer latencies in both evoked and induced activities. Correlation analyses suggest that similar maps were present for evoked and induced activities at different timepoints. In the discussion section, diverse proposals will be stated to define the potential roles of these modulations in the information processing for this cognitive task. As a general conclusion, induced activity enables the observation of cognitive mechanisms that are not visible by ERD or ERP modulations

Individual test-retest reliability of evoked and induced alpha activity in human EEG data

Diverse psychological mechanisms have been associated with modulations of different EEG frequencies. To the extent of our knowledge, there are few studies of the test-retest reliability of these modulations in the human brain. To assess evoked and induced alpha reliabilities related to cognitive processing, EEG data from twenty subjects were recorded in 58 derivations in two different sessions separated by 49.5 +/- 48.9 (mean +/- standard deviation) days. A visual oddball was selected as the cognitive task, and three main parameters were analyzed for evoked and induced alpha modulations (latency, amplitude and topography). Latency and amplitude for evoked and induced modulations showed stable behavior between the two sessions. The correlation between sessions for alpha evoked and induced topographies in the grand average (group level) was r = 0.923, p<0.001; r = 0.962, p<0.001, respectively. The within-subject correlation values for evoked modulation ranged from 0.472 to 0.974 (mean: 0.766), whereas induced activity showed a different range, 0.193 to 0.892 (mean: 0.655). Individual analysis of the test-retest reliability showed a higher heterogeneity in the induced modulation, probably due to the heterogeneous phases found in the second case. However, despite this heterogeneity in phase values for induced activity relative to the onset of the stimuli, an excellent correlation score was obtained for group topography, with values that were better than those of the grand average evoked topography. As a main conclusion, induced alpha activity can be observed as a stable and reproducible response in the cognitive processing of the human brain

Reduction of EEG power during expectancy periods in humans

The contingent negative variation (CNV), and the associated event-related desynchronization (ERD) on motor areas and sensory areas, and increase of alpha in the ipsilateral to the cued stimulus side, are different brain signals that reflect motor, sensory, and cognitive activations related to the expectancy of the next stimulus. However, the possibility of an overall change in EEG oscillatory activity during expectancy periods has not been directly addressed. The present report tests whether the background oscillatory activity is modulated by a warning signal. During the expectancy period, the power spectral density (PSD) between 0 and 42.9 Hz – including delta, theta, alpha, beta, and gamma – decreased with respect to the baseline. These results suggest that during expectancy periods there is a generalised decrease in the oscillatory activity, and that reduction of the EEG power would facilitate the phasic and oscillatory neural activities triggered by the next target stimulus.Junta de AndalucíaMinisterio de Ciencia y Tecnología (España

Affective Valence Detection from EEG Signals Using Wrapper Methods

In this work, a novel valence recognition system applied to EEG signals is presented. It consists of a feature extraction block followed by a wrapper classification algorithm. The proposed feature extraction method is based on measures of relative energies computed in short‐time intervals and certain frequency bands of EEG signal segments time‐locked to the stimuli presentation. These measures represent event‐related desynchronization/synchronization of underlying brain neural networks. The subsequent feature selection and classification steps comprise a wrapper technique based on two different classification approaches: an ensemble classifier, i.e., a random forest of classification trees and a support vector machine algorithm. Applying a proper importance measure from the classifiers, the feature elimination has been used to identify the most relevant features of the decision making both for intrasubject and intersubject settings, using single trial signals and ensemble averaged signals, respectively. The proposed methodologies allowed us to identify a frontal region and a beta band as the most relevant characteristics, extracted from the electrical brain activity, in order to determine the affective valence elicited by visual stimuli

Retest reliability of individual alpha ERD topography assessed by human electroencephalography

Background Despite the immense literature related to diverse human electroencephalographic (EEG) parameters, very few studies have focused on the reliability of these measures. Some of the most studied components (i.e., P3 or MMN) have received more attention regarding the stability of their main parameters, such as latency, amplitude or topography. However, spectral modulations have not been as extensively evaluated considering that different analysis methods are available. The main aim of the present study is to assess the reliability of the latency, amplitude and topography of event-related desynchronization (ERD) for the alpha band (10–14 Hz) observed in a cognitive task (visual oddball). Topography reliability was analysed at different levels (for the group, within-subjects individually and between-subjects individually). Results The latency for alpha ERD showed stable behaviour between two sessions, and the amplitude exhibited an increment (more negative) in the second session. Alpha ERD topography exhibited a high correlation score between sessions at the group level (r = 0.903, p<0.001). The mean value for within-subject correlations was 0.750 (with a range from 0.391 to 0.954). Regarding between-subject topography comparisons, some subjects showed a highly specific topography, whereas other subjects showed topographies that were more similar to those of other subjects. Conclusion ERD was mainly stable between the two sessions with the exception of amplitude, which exhibited an increment in the second session. Topography exhibits excellent reliability at the group level; however, it exhibits highly heterogeneous behaviour at the individual level. Considering that the P3 was previously evaluated for this group of subjects, a direct comparison of the correlation scores was possible, and it showed that the ERD component is less reliable in individual topography than in the ERP component (P3).Ministerio de Economía y Competitividad (España) PSI2016-78133-PAsociación Sanitaria Virgen Macaren

Ascomicetos hipogeos de la región occidental del Sistema Volcánico Transversal, México

Background and Aims: In Mexico, 42 species of ascomycetes have been reported with hypogeous habit, which are few considering the knowledge of other groups of fungi. The purpose of this paper is to increase the knowledge about the diversion and distribution of hypogeous fungi species for Mexico.Methods: Specimens were collected from different types of vegetation in the western portion of the transverse volcanic system, located in the state of Michoacán. The specimens collected were pictured and described following the protocols for the group.Key results: We present the description and discussion of six species of ascomycetes with hypogeous habit, Elaphomyces appalachiensis, Genea mexicana, Genabea cerebriformis, Hydnobolites cerebriformis, Tuber pseudoseparans and T. tequilanum.Conclusions: The records of these species represent new collection sites for Mexico and first records for the mycobiota of the state of Michoacán. It increases the distribution of Elaphomyces appalachiensis, Genabea cerebriformis and Hydnobolites cerebriformis, known from the United States of America and northern Mexico, to the Transversal Volcanic System, while Genea mexicana, Tuber pseudoseparans and T. tequilanum only are known in this mountainous system.Antecedentes y Objetivos: En México se han reportado 42 especies de ascomicetos con hábito hipogeo; son pocas considerando el conocimiento de otros grupos de hongos. El objetivo de este trabajo fue incrementar el conocimiento sobre la diversidad y distribución de especies de hongos hipogeos para México.Métodos: Se realizaron recolectas en diversos tipos de vegetación del Sistema Volcánico Transversal en la porción occidental perteneciente al estado de Michoacán. El material se fotografió y describió siguiendo los protocolos para el grupo.Resultados clave: Se presentan la descripción y discusión de seis especies de ascomicetos con hábito hipogeo, Elaphomyces appalachiensis, Genea mexicana, Genabea cerebriformis, Hydnobolites cerebriformis, Tuber pseudoseparans y T. tequilanum.Conclusiones: Los registros representan nuevas localidades para el país y primeras citas para la micobiota del estado de Michoacán. Se incrementa la distribución de Elaphomyces appalachiensis, Genabea cerebriformis e Hydnobolites cerebriformis, conocidos de los Estados Unidos de América y el Norte de México, hasta el Sistema Volcánico Transversal, mientras que Genea mexicana, Tuber pseudoseparans y T. tequilanum solo se conocen en este sistema montañoso

Retest reliability of individual P3 topography assessed by high density electroencephalography

Background Some controversy remains about the potential applicability of cognitive potentials for evaluating the cerebral activity associated with cognitive capacity. A fundamental requirement is that these neurophysiological parameters show a high level of stability over time. Previous studies have shown that the reliability of diverse parameters of the P3 component (latency and amplitude) ranges between moderate and high. However, few studies have paid attention to the retest reliability of the P3 topography in groups or individuals. Considering that changes in P3 topography have been related to different pathologies and healthy aging, the main objective of this article was to evaluate in a longitudinal study (two sessions) the reliability of P3 topography in a group and at the individual level. Results The correlation between sessions for P3 topography in the grand average of groups was high (r = 0.977, p<0.001). The within-subject correlation values ranged from 0.626 to 0.981 (mean: 0.888). In the between-subjects topography comparisons, the correlation was always lower for comparisons between different subjects than for within-subjects correlations in the first session but not in the second session. Conclusions The present study shows that P3 topography is highly reliable for group analysis (comprising the same subjects) in different sessions. The results also confirmed that retest reliability for individual P3 maps is suitable for follow-up studies for a particular subject. Moreover, P3 topography appears to be a specific marker considering that the between-subjects correlations were lower than the within-subject correlations. However, P3 topography appears more similar between subjects in the second session, demonstrating that is modulated by experience. Possible clinical applications of all these results are discussed.Ministerio de Economía de España SEJ2007-6534