Marcadores Neurales como Indicadores de Funciones Predictivas en Pacientes con Traumatismo Cerebral Moderado a Severo / Neural Markers as Indicators of Predictive Functions in Patients with Moderate to Severe Brain Trauma

Introducción. El traumatismo encéfalo craneano moderado a severo (TEC-MS) es una condición compleja que cambia la estructura y función del cerebro, afectando a personas de distintas edades. Los problemas cognitivos y motores son la mayor causa de discapacidad en individuos con TEC-MS crónico. Sin embargo, muchas de estas dificultades no son visibles de inmediato clasificándose como una "Epidemia silenciosa". Las principales alteraciones reportadas por los pacientes tienen relación con problemas de la memoria, atención y lentitud psicomotora, los cuales tienen un impacto en su independencia y funcionalidad. Objetivo. Este estudio tiene por objetivo discutir y revisar la evidencia disponible acerca de la capacidad de los pacientes crónicos con TEC-MS para generar predicciones en diferentes niveles de procesamiento cerebral. Métodos. Para esto, utilizamos desde las neurociencias el modelo teórico del código predictivo para explicar las respuestas neurofisiológicas adquiridas bajo un paradigma de predicción auditiva. Esta información es complementada con el reporte de datos preliminares de sujetos con TEC-MS y sujetos control, con el fin de ilustrar los aspectos teóricos discutidos. Conclusiones. Esto podría contribuir a una mejor comprensión de los mecanismos neurales detrás de los déficits cognitivos en esta población, aportando una perspectiva que nos oriente al desarrollo de nuestras estrategias terapéuticas.

Background. Moderate to severe traumatic brain injury (TBI-MS) is a complex condition that changes the structure and function of the brain, affecting people of different ages. Cognitive and motor problems are the major cause of disability in individuals with chronic ECT-MS. However, many of these difficulties are not immediately visible, classifying them as a "Silent Epidemic." The main alterations reported by patients are related to problems with memory, attention and psychomotor slowness, which have an impact on their independence and functionality. Objetive. This study aims to discuss and review the available evidence about the ability of chronic ECT-MS patients to generate predictions at different levels of brain processing. Methods. For this, we use the theoretical model of the predictive code from neuroscience to explain the neurophysiological responses acquired under an auditory prediction paradigm. This information is complemented with the report of preliminary data from subjects with ECT-MS and control subjects, in order to illustrate the theoretical aspects discussed. Conclusions. This could contribute to a better understanding of the neural mechanisms behind cognitive deficits in this population, providing a perspective that guides us in the development of our therapeutic strategies.

Efectos de la expresión emocional y de la orientación del rostro sobre las respuestas conductuales y el componente N170 / Effects of emotional expresión and orientation of faces on behavioral and on N170 component

Resumen En este estudio se pretendió corroborar el efecto de inversión con estímulos de rostros calmos, de miedo e ira tomados de la base de datos de rostros calmos y emocionales NSTIM (base de datos de rostros), presentados de forma vertical e invertida, con una duración de presentación de 2000 milisegundos. Los resultados muestran que no hubo modulación del componente N170 tanto en latencia como en amplitud ante la presentación de rostros invertidos comparados con los rostros presentados verticalmente. Tampoco se encontró alteración en la precisión de la respuesta y demora en los tiempos de reacción ante los rostros invertidos comparados con los rostros verticales. Estos resultados probablemente se pueden explicar por la presentación prolongada de los rostros invertidos que permitieron a los participantes tener el tiempo para reorganizar los elementos que componen los rostros. El aporte de este estudio es poner en evidencia que el tiempo de presentación de rostros invertidos es crucial para que se presente el efecto de inversión de rostros, el cual debe estar entre 200 y 500 milisegundos.

Abstract The aim of this study was to confirm the inversion effect with calm, fear and anger faces taken from calm and emotional NSTIM (face database) face database presented in upright and upside down position. The duration of the stimuli was 2000 ms. There was no modulation in latency or amplitude of the N170 component for inverted faces. There was no alteration in accuracy and reaction times in inverted faces compared to vertical faces. These results could be explained by the long presentation of the inverted faces that probably permitted the participants to reorganize the elements that compose the face. The contribution of this study is to demonstrate that the time presentation of the inverted faces between 200 and 500 ms is crucial for the FIE to appear.

Error related negativity and multi-source interference task in children with attention deficit hyperactivity disorder-combined type / La negatividad relacionada al error en una tarea de interferencia multifuente en niños con trastorno por déficit de atención-hiperactividad tipo combinado

Objective To compare performance of children with attention deficit hyperactivity disorders-combined (ADHD-C) type with control children in multi-source interference task (MSIT) evaluated by means of error related negativity (ERN). Method We studied 12 children with ADHD-C type with a median age of 7 years, control children were age- and gender-matched. Children performed MSIT and simultaneous recording of ERN. Results We found no differences in MSIT parameters among groups. We found no differences in ERN variables between groups. We found a significant association of ERN amplitude with MSIT in children with ADHD-C type. Some correlation went in positive direction (frequency of hits and MSIT amplitude), and others in negative direction (frequency of errors and RT in MSIT). Conclusion Children with ADHD-C type exhibited a significant association between ERN amplitude with MSIT. These results underline participation of a cingulo-fronto-parietal network and could help in the comprehension of pathophysiological mechanisms of ADHD. .

Objetivo Comparar el rendimiento de un grupo de niños con trastorno por déficit de atención-hiperactividad de tipo combinado (TDAH-C), con niños controles, en la tarea de interferencia multi-fuente (TIMF), evaluado por la negatividad relacionada al error (NRE). Método Estudiamos 12 niños con TDAH-C con una mediana de 7 años, los controles estuvieron pareados por edad y género. Los niños realizaron la TIMF con registros simultáneos de NRE. Resultados No encontramos diferencias en los parámetros de la TIMF entre grupos. No encontramos diferencias en las variables de la NRE entre grupos. Encontramos asociaciones significativas entre la amplitud de la NRE en niños con TDAH-C. Una correlación fue en dirección positiva: (frecuencia de aciertos y amplitud de TIMF), y otras fueron en dirección negativa (frecuencia de errores y el tiempo de respuesta en la TIMF). Conclusión Los niños con TDAH-C presentan una asociación significativa entre la amplitud de la NRE con la TIMF. Los resultados sugieren la participación de la red cíngulo-fronto-parietal y pueden ayudar en la comprensión de los mecanismos fisiopatológicos del TDAH-C. .

Potenciales evocados como marcadores neurofisiológicos de la percepción y el reconocimiento de caras / Event-related potentials as neurophysiological markers of face perception and face recognition

La percepción y el reconocimiento de caras como funciones cerebrales complejas de gran relevancia psicobiológica son objeto de estudio por parte de la comunidad neurocientífica desde hace varias décadas. En este artículo se revisan los datos existentes sobre potenciales evocados y procesamiento de caras y se discute la significación funcional de cada una de las respuestas psicofisiológicas analizadas en relación con las diferentes etapas o módulos descritos en los modelos cognitivos y neurales sobre el procesamiento de rostros familiares y desconocidos. El procesamiento inicial de las caras está relacionado con respuestas electrofisiológicas muy tempranas como la onda occipital P120, asociada a la detección de aspectos estructurales primarios sugerentes, grosso modo, de la presencia de una cara en nuestro campo visual. La onda temporal posterior N170 es más sensible a la configuración facial (vs. otros objetos) y a la presencia de rasgos faciales distintivos antes de que se produzca la individualización intra-categorial (reconocimiento visual de la identidad), mientras que las respuestas de latencia más tardía como la temporal anterior N250r y la topográficamente más distribuida N400 son las que reflejan, respectivamente, los procesos de acceso y recuperación de información relativa a las caras conocidas en la memoria a largo plazo.

The perception and recognition of faces are complex brain functions of great psychobiological relevance and have been studied by the neuroscientific community for decades. This paper reviews existing data on event-related potentials and facial processing, therefore, the functional significance of each psychophysiological response, in relation with the different stages or modules described in cognitive and neural models regarding the processing of familiar and unknown faces are discussed. The initial processing of faces is related to early electrophysiological responses as occipital P120 wave, associated with the detection of primary structural features suggestive of, basically, the presence of a face in our visual field. The posterior temporal N170 wave is more sensitive to facial configuration (vs. other objects) and to the presence of specific facial features before the intra-categorical identification takes place (visual recognition of identity), while the later latency responses as the anterior temporal N250r and the more topographically distributed N400 are those that reflect, respectively, the access and retrieval of information on familiar faces in long-term memory.

Potenciales cerebrales relacionados a feedback en el estudio del aprendizaje y la toma de decisiones económicas / Brain Potentials Related to Feedback on the Study of Learning and Economic Decision Making

Investigaciones con Potenciales Relacionados a Eventos han demostrado la existencia de un componente llamado Negatividad Relacionada a Retroalimentación de Error, el cual ha sido referido como una deflexión negativa que distingue entre ganancias y pérdidas, en tanto resultados esperados y no esperados respectivamente. Así, mientras algunos estudios han operacionalizado la idea de resultado esperado como la probabilidad de ganar vs. Perder, otros lo han hecho como la magnitud esperada de las recompensas. Hasta ahora existe poca investigación tendiente a observar cómo estas interpretaciones alternativas de "resultado esperado", o su interacción en términos de un modelo de "valor esperado" que las integre, afectan la Negatividad Relacionada a Retroalimentación de Error. El presente trabajo contextualiza el estudio de los mecanismos cerebrales asociados a la toma de decisiones, situando los estudios de Negatividad Relacionada a Retroalimentación de Error en su contexto teórico, revisa las dos tendencias de estudio desarrolladas hasta la fecha y explora posibilidades de ampliación del estudio de este componente en el contexto del naciente campo transdisciplinario de la neuroeconomía.

Studies using Event-Related Potentials have shown the existence of a component called Feedback Error-Related Negativity (fERN). This component has been characterized as a negative deflection which responds differentially to profits and losses in terms of expected and unexpected outcomes. Thus, while some studies have defined the idea of "expected outcome" as the probability to win vs. to lose, others have defined it as the expected size of rewards. How these alternative interpretations of "expected outcome" affect the fERN's research, and the effects of their interaction under a specific model of "expected value" has not been properly assessed. This work contextualizes the general study of neural mechanisms involved in decisionmaking processes, putting the fERN studies in context; besides, it reviews the two main approaches to its research; and finally, it explores the possibilities to further expand the fERN studies, in the context of the transdisciplinary rising field of neuroeconomics.

Procesamiento léxico-semántico en un grupo de sujetos sanos: estudio con potenciales relacionados a eventos

resumen está disponible en el texto completo

Abstract: Introduction: An insight into the meaning of words is one of the central processes of semantic memory. To evalúate the access to the cognitive representation of the meaning of words, in the present study we used the lexical decision paradigm developed by Marcos. In this situation, the subject has to recognize if the presented stimulus corresponds to a word or a pseudo-word with the purpose of building a model of normal processing. Once such a model of normal processing is obtained, the findings can be contrasted with pathologies in which semantic memory is altered. Method: The sample consisted of 32 healthy subjects (7 men, 25 women), right-handed and with no personal or familial history of neurological or psychiatric conditions. The average age of the subjects was 34.4 (+ 9.56) years and they had an average educational level of 16.2 (+ 4.4) years. The lexical decision paradigm employed in this study is constituted by 408 stimuli, 240 words and 168 pseudo-words. The criteria for word selection were: frequency, length, grammatical category and morphology. Electroencephalogram (EEG) monopolar recording was obtained from 19 derivations (F3, F4, C3, C4, P3, P4, O1, O2, F7, F8, T3, T4, T5, T6, Fz, Cz and Pz), as well as event-related potentials (ERPs) for the word and pseudo-word sub-states. Results: In the first place, a chi-squared analysis was performed to establish whether significative differences existed between the rates of correct and incorrect answers for both sub-states. The value of chi-squared was 65.7 (gl=1) and significant for p<0.0001. A correlation value of 0.43 (p< 0.02) was found when the educational level and the percentage of correct answers in the sub-sate word were compared. On the other hand, for the pseudo-word sub-state, the value 0.24 was encountered for the same correlation, being statistically non-significant. Pearson's correlation coefficient was also calculated for the educational level variable compared to the mistakes committed when subjects were presented with frequent and infrequent words. In the case of infrequent words, a value of r = - 0.43 (p<0.02) was obtained when the educational level and the number of mistakes were correlated. No correlation was found when the educational level and the number of mistakes commited for frequent words were compared (r = - 0.06). A multivariate variance analysis for repeated measures was performed to determine significant differences between the reaction times when recognizing words or pseudo-words. The outcome showed that all effects were significant in the following cases: reaction times for words and pseudo-words, notwithstanding whether they were correct or incorrect; comparison between correct and incorrect answers, independently of their being words or pseudo-words, as well as the interactions between both effects. To determine differences between average ERPs for both sub-states, Student's T-test was applied with Bonferroni's correction and p<0.0002 as the significance level. Significant differences were encountered between the two sub-states, independently of the age or gender. In the 375-495 ms latency interval, a negative component was appreciated in the pseudo-words case, showing significant differences (p<0.0002) in the following derivations: F3, F4, C3, C4, P3, P4, O1, O2, T3, T5, T6, Fz, Cz and Pz. Amplitude differences between the two sub-states were more evident in Pz and P3 derivations followed by Cz. In addition, a positive component in the 700-795 ms latency interval was detected (mainly in 795 ms) when pseudo-words were presented. Here, the significant differences (p<0.0002) were manifest in the following derivations: F3, C3, P3, F7, T3, T5 and Pz. Amplitude differences between the two sub-states were mainly patent in Pz and P3 followed by C3. Discussion: When analyzing behavioral aspects, subjects made more mistakes when presented with words. However, individuals with less education were the ones committing more mistakes. From this we can infer that this variable may be associated with the range of lexical repertoire. A relation was encountered between educational level and word recognition. With regard to reaction times, significant differences were detected between both sub-states, since the recognition of both words and correct answers was achieved in shorter reaction times. Average reaction times for words and pseudo-words were 819.73 ms and 999.35 ms, respectively. Similarly, the latest potential component appeared in an interval of significant differences between 600 and 940 ms, though with a significance p<0.0005 between 690 and 805 ms. This means that positiveness occurred much sooner than the response, implying that the activity underlying ERPs is related to a cognitive processing of information due to the paradigm used. The analysis of ERPs primary components for both sub-states shows that significant differences arise until 270 ms. The negative component in this study was present between 270 and 580 ms, rendering it similar to N400 given its latency (around 400 ms). Although well-defined in centro-parietal regions, its distribution was generalized, which corresponds to the results of studies using the semantic incongruence paradigm. According to the data from previous research on ERPs, N400 has been associated with the integration process. If this were the case, this association would be equivalent to the semantic incongruence within a lexical integration process described in conventional literature as a "semantic facilitator", only that this time it would be limited to the process of access to the lexicon, which can be interpreted as a discrimination of the answer by assigning a meaning to a word, that is, to process information in the semantic module. This negative component may be related to the generalized response to brain activity when given a meaningless stimulus, i.e., a pseudo-word. Similarly, the wave amplitude may be related to the amount of activation necessary to gain access to the semantic representation of the stimulus in the memory. With regard to the positive component in this study, it is present between 600 and 940 ms and is interpreted as a late P300 (P3b), which has a latency in the 500-1400 ms interval. It is distributed over the centro-parietal region, making it a liable participant in the task categorization process, in which it is necessary to discriminate between the target from the non-target stimulus, and also reflects focalized attentional processes (voluntary) involved in the execution of the task. From the former, it is believed that this component may be related to attentional resources necessary to process the presentation of pseudo-words. Research dealing with the P600 component locate it within the context of statements and associate it with an anomaly in statement syntax. Therefore, even though the positive component lies within the P600 latency domain, this particular component was not considered as being present in this study, because a syntax incongruence paradigm was not used. Finally, the contribution of the present study lies in the finding of N400 and "P600" components, which have been reported when the "semantic facilitator" and the syntax incongruence paradigm were respectively used, but had not been observed when a lexical decision paradigm based on word recognition per se was utilized. Similarly, given that our results stem from a sample of healthy subjects, a comparison can be made with a patient population with semantic memory alterations.

Alexia sin agrafia en el infarto cerebral occipital

Se investigó un caso con alexia pura sin agrafia, secundaria a un infarto cerebral occipital. Se presentó, clínicamente, con una amaurosis bilateral de 2 h de duración, seguida de una marcada dificultad para la lectura, la cual era interpretada por el paciente como un déficit para la visión cercana y por los oftalmólogos y optometristas como una presbiopía. Se constató la ausencia de la onda P-300 en el estudio del componente endógeno de los potenciales relacionados con eventos (PRE) con tareas de discriminación fonética y su registro normal con tareas de discriminación gráfica. Así se confirmó el diagnóstico cliniconeurofisiológico de alexia pura sin agrafia mediante este método no invasivo, que estudia el proceso cognitivo cerebral.

A case of pure alexia without agraphia after en occipital cerebral infarction was presented. It clinically manifested with a bilateral amaurosis of 2 hours, followed by a marked difficulty for reading, which was interpreted by the patient as a visual deficit and by the ophthalmologists and optometrists as a presbyopia. The absence of the P-300 wave was proved in the study of the endogenous component of the event-related potentials (ERP) by using phonetic discrimination tasks and their normal record with graphic discrimination tasks. Thus, the cliniconeurophysiological diagnosis of pure alexia without agraphia was confirmed by this non-invasive method that studies the cerebral cognitive process.