3.02 Tesis doctorado

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Attentional bias for food cues after sleeve gastrectomy : a behavioral and electrophysiological study
(2019) Zumaeta Valenzuela, Arturo Ulises; Aboitiz, Francisco; Pontificia Universidad Católica de Chile. Facultad de Medicina
Attentional bias for food cues (ABFC) has been linked to food craving, the inability to lose weight, and obesity. For this study, we explored the presence of ABFC in a bariatric group, using a food-modified Stroop task and visual task, with EEG and eye-tracking recording, respectively. Our data showed an increased attentional bias for appetizing food, a decreased bias for diet food and a prolonged brain processing of food stimuli in the bariatric group.
Brain response to auditory deviance with and without conscious access
(2022) Osorio Galeano, Sergio Andrés; Aboitiz, Francisco; Pontificia Universidad Católica de Chile. Facultad de Medicina
La habilidad de extraer regularidades estadísticas presentes en estímulos sensoriales y detectar cuando se presentan violaciones a dichas regularidades es de vital importancia para los organismos biológicos, en tanto median respuestas autonómicas y dirigidas a metas que son cruciales para la supervivencia. Por un lado, la extracción de regularidades estadísticas presentes en la escena sensorial permite la consolidación de un modelo interno del mundo. Por otro, la detección de violaciones en estas regularidades permite la actualización de dicho modelo, mediando así procesos de adaptación conductual. En el campo de la neurociencia cognitiva, la respuesta del cerebro a la desviación sensorial en la modalidad auditiva ha sido estudiada de manera clásica por medio de los potenciales asociados a eventos (ERPs, por su sigla en inglés). Esta literatura ha mostrado que la respuesta del cerebro a la desviación auditiva se puede caracterizar por la secuencia de dos respuestas neurales en la señal electroencefalográfica: el potencial de disparidad (MMN, por su sigla en inglés) y la respuesta P3. El MMN es un evento neural automático que puede ser observado independientemente de los estados atencionales o de consciencia de los individuos, mientras que la respuesta P3 depende crucialmente del acceso consciente a la desviación sensorial. Otros dos potenciales marcadores de la desviación auditiva son los cambios fásicos en el tamaño de la pupila e incremento evocados en el poder oscilatorio de las bandas de frecuencia theta (4-7 Hz) y beta (15-30 Hz). Mientras la literatura muestra que la detección de la desviación está acompañada de incrementos en el tamaño de la pupila (un marcador de la alerta y del sistema norepinefrinérgico) y del poder de theta y beta, no se conoce muy bien como estas respuestas neurales estarían moduladas por el acceso consciente a la desviación auditiva. Entender cómo responde el cerebro a la desviación auditiva con y sin acceso consciente nos permitiría entender la interacción dinámica existente entre mecanismos de procesamiento bottom-up y de modulación top-down durante el comportamiento enfocado a metas. En este estudio, nos propusimos entender cómo responde el cerebro a la desviación auditiva con y sin acceso consciente. Para esto, diseñamos una versión modificada de la tarea clásica de tipo oddball auditivo que nos permitió separar el procesamiento consciente del procesamiento subconsciente de la desviación auditiva. Para esto, identificamos los umbrales de discriminación consciente de cada individuo, lo cual nos permitió presentar a nuestros sujetos secuencias de tonos donde el último estímulo (el estímulo objetivo), podía ser otro tono estándar, un estímulo subumbral o un estímulo supraumbral. Los participantes debían reportar si el último estímulo de cada secuencia había sido igual o distinto de los anteriores. Por medio de esta tarea, recogimos datos conductuales (índices de sensibilidad y tiempos de reacción), pupilométricos (respuestas evocadas) y electroencefalográficos (ERPs, transformaciones de tiempo frecuencia al nivel de los electrodos y de las fuentes corticales, así como datos de conectividad funcional). Nuestros resultados muestran que las desviaciones subumbrales fueron incorrecta y sistemáticamente juzgadas como tonos estándar, lo cual refleja el procesamiento subconsciente de la desviación. En cambio, las desviaciones supraumbrales fueron correcta y sistemáticamente reportadas como diferentes, lo cual da cuenta del acceso consciente a la desviación auditiva. Además, replicamos hallazgos sobre la secuencia de MMN y P3 como marcadores confiables del procesamiento consciente y subconsciente de la desviación. Los datos pupilométricos sugieren que todos los estímulos objetivos están asociados a una respuesta pupilar, pero que dicha respuesta es mayor durante el procesamiento subconsciente de la desviación auditiva, reflejando de esta manera el procesamiento de la incertidumbre perceptual inesperada. Incrementos en el poder de theta y beta fueron observados en regiones corticales previamente asociadas con los orígenes del MMN y P3, incluyendo regiones temporales, prefrontales y cinguladas. Mientras que el poder de theta en regiones temporales reflejaría predicciones auditivas y mantención de la información sobre la identidad de un estímulo auditivo novedoso, los incrementos en el poder de beta en regiones prefrontales y cinguladas reflejarían la detección de un error en la predicción y la incertidumbre sensorial. Finalmente, incrementos en la conectividad funcional dentro del rango de theta reflejarían intercambio de información entre procesadores corticales distribuidos globalmente, lo cual soportaría la percepción consciente y la toma de decisiones, mientras que incrementos de conectividad funcional dentro del rango de beta reflejarían procesos de modulación top-down señalando así la necesidad de adaptación de los niveles de alerta debido a una alta incertidumbre y mecanismos de detección de errores en la predicción que son sensibles a una mayor saliencia del evento sensorial. Nuestros resultados subrayan como el cerebro asigna pesos a los mecanismos bottom-up y top-down durante el comportamiento enfocado a metas en función de si los eventos sensoriales son percibidos conscientemente o no, así como la contribución de la adaptación de la alerta durante esta interacción entre mecanismos de procesamiento de la información sensorial. Eso ilustra además la relación dinámica y en constante adaptación entre percepción y cognición.
Functional and structural neural correlates of attention and memory during bimodal (auditory/visual) stimuli in children who play a musical instrument
(2018) Kausel Kamp, Leonie Margarita; Aboitiz, Francisco; Pontificia Universidad Católica de Chile. Facultad de Medicina
The ability to focus on one or more stimuli at the same time is a crucial capacity that allows us to cope successfully with our daily life. Since playing a musical instrument demands to pay attention to lots of events at the same time, we hypothesized that this activity trains these types of attention, and that the neural networks underlying these skills would be boosted in children who regularly learn and play a musical instrument. To test our hypothesis, we asked children aged 10 to 13 with and without musical training to complete a selective and divided attention task while their brain activity was measured with fMRI. The task presented a pair of bimodal stimuli (melody and figure) to the participants and they were asked to pay attention only to the auditory, only to the visual, or to both stimuli at the same time. Both stimuli were tested with a same/different memory task after presentation in order to confirm attention allocation. Our study showed that both groups were able to follow the attention instructions, showing a better performance on the memory tasks of the items that they were instructed to attend, but musically trained children had an overall better performance on both memory tasks. This difference between groups in overall performance was guided by higher activation in musicians of the fronto-parietal attention network and the thalamus among others in the encoding phase of in the three attention conditions. In addition, we found that the better performance of musically trained children on the auditory memory tasks was not only due to improved allocation of attentional resources, but also due to facilitated encoding of auditory stimuli given by the years of training that depended on the left inferior frontal gyrus (IFG) and left supramarginal gyrus (SMG), which are part of the phonological loop. Therefore, our results strongly suggest that two distinct neural mechanisms played a role in the better performance of musically trained children on our task. Based on our results, we propose a mechanistic framework that allows to interpret the observations that have been made on the impact of musical training across lifespan. Our results could be relevant for educational and public health policies, and they also suggest that musical training could be used as a non-pharmacological intervention strategy for children with attentional problems.
Identification of electroencephalography and psychophysical parameters with potential diagnostic use for suicidal patients
(2023) Gajardo Gómez, Rosario; Aboitiz, Francisco; Pontificia Universidad Católica de Chile. Facultad de Medicina
Suicide is a global public health concern, with women showing a higher prevalence of suicidal thoughts and attempts compared to men. The shift from suicidal ideation to suicidal attempts involves individual, social, and environmental factors, with impulsivity playing a significant role. Early detection of suicide risk is vital, and early biological markers are urgently needed. An interesting candidate marker is the Loudness Dependence of Auditory Evoked Potentials (LDAEP). While LDAEP shows promise in characterizing patients with depression and impulsivity, it has been largely used with emotionally neutral stimuli. Thus, its characterization in response to emotional auditory stimuli could represent an improvement as a neuropsychiatric risk marker. This study addresses this gap by examining neural and emotional processing in female patients with depressive episodes, suicidal ideation, and recent suicidal attempts. Our hypothesis posits that female patients with depressive episodes and recent suicide attempts will exhibit greater impairments in neural and emotional processing, but lower levels of impulsivity compared to female patients with depressive episodes and suicidal ideation but no recent suicida attempts. To achieve this, this study explored the interplay between behavior, electrophysiology, and psychology in 19 female patients, including 10 subjects with Suicidal Ideation (SI) and 9 subjects with Suicide Attempt (SA), all admitted to the psychiatric hospitalization service of San Carlos de Apoquindo Clinical Center. Socioeconomic and demographic factors were comparable between groups, emphasizing the role of individual experiences. The LDAEP component was assessed in response to tonal and emotional auditory stimuli. False alarms, accuracy, and response times were analyzed. A multiple correlation matrix with false discovery rate (FDR) correction revealed associations between clinical psychological evaluations and electrophysiological data. Linear regression analysis uncovered mediating factors shaping these relationships. All patients had depressive episodes, with common triggers being suicidal thoughts, interpersonal issues, family conflicts, and academic stressors. Most had received therapy, and self-harm was prevalent, especially in SA. Findings revealed shorter reaction times (RT) in SI the group to neutral stimuli, suggesting impulsive tendencies. RT frequency distributions in the SA group displayed a faster response to negative stimuli, indicating a negative bias associated with depressive states. LDAEP analysis of tonal and emotional stimuli showed no significant differences between groups. However, the SI group demonstrated a tendency towards a greater tonal LDAEP. SI showed increased P2 amplitude, signifying enhanced perceptual attentional processing of emotional information. A deflection in the P3 component suggested reduced attentional allocation, diminished cognitive processing, and a lower level of emotional content evaluation. A consistent plateau in P2-P3 amplitudes was observed for both positive and negative stimuli, indicating a blunted affective response and decreased cognitive and emotional flexibility. SI demonstrated a stronger correlation between impulsivity and depression, while SA showed associations between hopelessness, impulsivity, and depression. Childhood trauma, particularly sexual aggression, exacerbated pathology in SI. Family support was a significant factor influencing depressive symptoms in both groups. SI exhibited a negative correlation between depressive symptoms and hopelessness, influenced by protective factors. Significant correlations were found between electrophysiological and psychological variables. In SI, cognitive factors related to life satisfaction affected neural responses, while hopelessness and childhood trauma influenced depressive symptoms. In SA, depressive symptoms, hopelessness, and impulsivity were strongly correlated, emphasizing the need for clinical intervention. The results highlight the complex interplay of impulsivity, depressive states, cognitive processing, and emotional regulation in shaping suicidal ideation and suicide attempts. Further investigations should continue to explore the intricate mechanisms underlying suicidality, ultimately leading to more effective strategies for identifying and supporting individuals at risk of suicide.
Modulation of attention by motor interaction: A study in a visual discrimination task
(2019) Arellano Roco, Cristian Andrés; Aboitiz, Francisco; Maldonado Arbogast, Pedro; Pontificia Universidad Católica de Chile. Facultad de Medicina
Most of the traditional neuroscience research has considered attention as a superior cognitive function mainly oriented to perceptual processes and away from sensorimotor functions. Alternatively, the “Attention for Action” framework proposes a close relationship between cognitive and sensorimotor processes, where attention would act as an integrative mechanism. There is empirical evidence suggesting that the processes of preparation and motor execution have a positive impact on the attentional and perceptual processes, but there is no consensus if the interaction of these processes produces interference or improvement in them. The aim of this thesis is to contribute to a better understanding of the interactions between attentional and motor processes. In this thesis we propose that the functional coupling between attentional and motor processes positively modulates attention processes. To evaluate this proposition we designed an ocular pursuit dual task that required sustained attention and discrimination of a visual stimulus (visual condition). By adding a motor relevant act to the task (motor condition) we were able to evaluate if this produced a modulating effect on the attention and if differences were observed between both experimental conditions. Task performance was measured using behavioral, electro physiological (ERPs) and pupil diameter variation parameters in both, a group of healthy children (Control group) and another group of children with attentional deficit (ADHD group). Behavioral results showed that the Control group had a better overall performance in the task than the ADHD group, with better performance in visual condition than in motor condition, but that differentiating effect between groups disappeared when comparing them within motor condition, that means the motor effect favored the performance of the ADHD group. Electrophysiology showed that in motor condition a modulating effect was produced on CNV, P1 and N1 compared with the visual condition for both groups, it being larger in the Control group. Finally, Control group showed a progressive increase in pupillary diameter along the trial in the motor condition, while in the visual condition this increase was stabilized 400 ms. prior to the appearance of visual stimulus and remained so until the end of the trial. ADHD group, however, showed a progressive increase in pupillary diameter along the trial for both conditions, which could reflect a greater attentional load of these subjects in the task. These results suggest that in the analyzed task there would be a positive modulatory effect of the motor component on the attentional processes, which despite not being clear in behavioral performance, is consistent at electrophysiological level and in the pupil diameter variation, which would reflect positive interaction between these processes.
The role of sleep-oscillations in the emergence of hippocampal-dependent memory during postnatal development
(2022) García Pérez, María Alexandra; Valdés Guerrero, José Luis; Maldonado Arbogast, Pedro; Aboitiz, Francisco; Pontificia Universidad Católica de Chile. Escuela de Medicina
Las memorias dependientes del hipocampo surgen tardíamente en el desarrollo postnatal y en paralelo con la maduración del hipocampo. El modelo de formación de la memoria en dos etapas afirma que durante el sueño ocurre un diálogo entre el hipocampo y la neocorteza, donde las oscilaciones lentas corticales (SO), los Spindles talamocorticales y los Sharp-wave ripples del hipocampo (SWR) se sincronizan, permitiendo la consolidación de los recuerdos de tipo episódicos. Sin embargo, este modelo no ha sido validado en etapas tempranas del desarrollo. En esta tesis, se evaluó la aparición de la memoria dependiente de hipocampo mediante la exposición sucesiva a la prueba conductual de reconocimiento de objeto-lugar. Junto con esto, se registró la actividad in vivo de SO, Spindles y SWRs durante periodos de sueño inmediatamente posteriores a la evocación en la tarea de objeto-lugar, donde encontramos que la memoria dependiente del hipocampo aparece en el día postnatal 32, independientemente del sobre-entrenamiento previo de la tarea. Curiosamente, observamos que los animales con mejor rendimiento tenían una mayor densidad y duración de los Spindles y una menor densidad de SWRs. Además, observamos cambios en el acoplamiento temporal entre SO-Spindles y Spindles-SWRs durante esta ventana temporal. Nuestros resultados aportan nuevas evidencias sobre el inicio de la memoria dependiente del hipocampo y explican cómo se ajustan los modelos de consolidación adulta en las primeras etapas del desarrollo postnatal.

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