ENGLISH: SUMMARYThe present thesis encloses four studies that sought to asses the neural correlates, timing and modulatory effects of a negative emotional context on the processing of task-irrelevant novel sounds within the framework of auditory-visual oddball experimentation. Study I, II and III were conducted using event-related brain potentials (ERP) and Study IV used functional magnetic resonance imaging (fMRI).In Study I, fourteen healthy volunteers responded to a visual discrimination task, with either neutral or threatening sceneries, while a 64-channel electroencephalogram (EEG) was recorded. In Study II, fourteen healthy female volunteers responded to visual stimuli displaying either threatening or neutral sceneries, using an optimised version of the task, while a 64-channel electroencephalogram (EEG) was recorded. In Study III, fourteen female subjects and fourteen male subjects were recorded using a 64-channel electroencephalogram (EEG) while performing the same visual discrimination task as in Study II. In Study IV, seventeen healthy female volunteers responded to a visual colour discrimination task, with images of emotional facial expressions (angry, fearful or neutral), while neuroimaged in a 3Tesla scanner. In all experimental designs, single auditory stimuli, consisting of a majority of standard tones and infrequent novel environmental sounds, preceded the images and had to be ignored by the subjects. The main results in all four studies were pointing at comparable conclusions. Novel sounds elicited a distracting effect on subjects' performance, reflected by longer response times compared to those in standard trials. This effect was consistently magnified when preceding and following images were of a negative emotional load as compared to the neutral images. In Study III, women, but not men, showed this effect.Brain responses recorded with ERPs revealed, in Study I, an enhancement of late novelty-P3 responses to novel sounds in negative context, compared to the neutral one. Furthermore, Study II demonstrated that this modulatory effect can also occur in the early phase of this ERP component. Study III showed that the modulation of the early novelty-P3 was present only in women. Hemodynamic responses, in turn, showed that activation induced by novel sounds in superior temporal gyrus, comprising secondary cortex, planum temporale and primary auditory cortex, was enhanced when subjects responded to faces with a negative emotional expression compared to the neutral ones. The combination of results in the four studies show that the emotional context enhances excitability of auditory novelty cerebral regions at early stages of processing, making irrelevant sounds become more available in the attentional set under threatening conditions. Still, gender differences may be present in these effects, possibly due to differences in the evaluation of the emotional stimuli. / CATALÀ:La present tesi inclou quatre estudis que pretenen determinar els correlats neurals, temporalitat i efectes modulatoris d'un context emocional negatiu en el processament de sons novedosos irrellevants per la tasca en curs, en el marc de l'experimentació oddball auditivo- visual. L'Estudi I, II i III van ser duts a terme amb la tècnica de potencials evocats (PEs) i per l'Estudi IV es va utilitzar resonància magnètica funcional (RMf).A l'Estudi I, catorze voluntaris sans van respondre a una tasca de discriminació visual, amb escenes bé neutres, bé amenaçants, mentre s'enregistrava el seu electroencefalograma (EEG) de 64 canals. A l'Estudi II, catorze voluntàries sanes van respondre a estímuls visuals que representaven, bé escenes amenaçants o bé neutres, utilitzant una versió optimitzada de la tasca, mentre s'enregistrava el seu electroencefalograma (EEG) de 64 canals. A l'Estudi III, catorze dones i catorze homes van ser enregistrats utilitzant electroencefalograma (EEG) de 64 canals mentre realitzaven la mateixa tasca de discriminació visual que a l'Estudi II. A l'Estudi IV, disset voluntàries sanes van respondre a una tasca de discriminació de color, amb imatges d'expressions facials emocionals (d'amenaça, de por o neutra), mentre eren mesurades en un escàner de RMf de 3Tesla. En tots els dissenys experimentals, un estímul auditiu únic, que podia ser, bé en una majoria un to estàndard, o bé un so novedós ambiental infreqüent, precedia les imatges i havia d'ésser ignorat pels subjectes. Els principals resultats en tots quatre estudis apuntaren a conclusions comparables. Els sons novedosos produïren un efecte distractor en el rendiment dels subjectes, reflexat en temps de resposta més llargs comparats amb els assaigs amb sons estàndard. Aquest efecte va veure's consistentment magnificat quan les imatges precedents i següents tenien una càrrega emocional negativa en comparació a les imatges neutres. A l'Estudi III, les dones, però no els homes, van mostrar aquest efecte.Les respostes cerebrals enregistrades amb PEs revelaren, a l'Estudi I, un augment d'amplitud de la fase tardana del patró P3 de novetat davant de sons novedosos en context negatiu, en comparació amb el context neutre. A més, l'Estudi II va demostrar que aquest efecte modulatori pot ocórrer també en la fase primerenca d'aquest component de PE. L'Estudi III va mostrar que la modulació de la P3 de novetat era present només en dones. Les respostes hemodinàmiques, alhora, van mostrar que l'activació induïda pels sons novedosos al gir temporal superior, incloent escorça auditiva secundària, planum temporale i escorça auditiva primària, va ser augmentada quan els subjectes respongueren a cares amb una expressió emocional negativa en comparació amb les neutres. La combinació de resultats en els quatre estudis mostra que el context emocional augmenta l'excitabilitat de regions cerebrals en àrees primerenques de processament, fent que sons irrellevants es esdevinguin més disponibles en el set atencional en condicions d'amenaça. Tanmateix, és possible l'existència de diferències de gènere en aquests efectes, possiblement degut a diferències en l'avaluació dels estímuls emocionals. REFERENCESAlho, K., Winkler, I., Escera, C., Huotilainen, M., Virtanen, J., Jääskelainen, I.P., Pekkonen, E., Ilmoniemi, R.J. (1998). Processing of novel sounds and frequency changes in the human auditory cortex: magnetoencephalographic recordings. Psychophysiology, 35, 211-224.Bledowski, C., Prvulovic, D., Hoechstetter, K., Scherg, M., Wibral, M., Goebel, R., Linden, D.E.J. (2004). Localizing P300 generators in visual target and distractor processing: a combined event-related potential and functional magnetic resonance imaging study. The Journal of Neuroscience, 24(42), 9353-9360.Bradley, M.M., Codispoti, M., Lang, P.J. (2006). A multi-process account of startle modulation during affective perception. Psychophysiology, 43, 486-497.Clark, V.P., Fannon, S., Lai, S., Benson, R., Bauer, L. (2000). Responses to rare visual target and distractor stimuli using event-related fMRI. Journal of Neurophysiology, 83, 3133-3139. Cuthbert, B.N., Schupp, H.T., Bradley, M.M., McManis, M., Lang, P.J. (1998). Probing affective pictures: attended startle and tone probes. Psychophysiology, 35, 344-347.Escera, C., Alho, K., Winkler, I., Näätäänen, R. (1998). Neural mechanisms of involuntary attention to acoustic novelty and change. Journal of Cognitive Neuroscience, 10(5), 590-604.Escera, C., Alho, K., Schröger, E., Winkler, I. (2000). Involuntary attention and distractibility as evaluated with event-related brain potentials. Audiology and Neurootology, 5, 151-166.

The human central auditory system can automatically extract abstract regularities from a variant auditory input. To this end, temporarily separated events need to be related. This study tested whether the timing between events, falling either within or outside the temporal window of integration (~350 ms), impacts the extraction of abstract feature relations. We utilized tone pairs for which tones within but not across pairs revealed a constant pitch relation (e.g., pitch of second tone of a pair higher than pitch of first tone, while absolute pitch values varied across pairs). We measured the mismatch negativity (MMN; the brain’s error signal to auditory regularity violations) to second tones that rarely violated the pitch relation (e.g., pitch of second tone lower). A Short condition in which tone duration (90 ms) and stimulus onset asynchrony between the tones of a pair were short (110 ms) was compared to two conditions, where this onset asynchrony was long (510 ms). In the Long Gap condition, the tone durations were identical to Short (90 ms), but the silent interval was prolonged by 400 ms. In Long Tone, the duration of the first tone was prolonged by 400 ms, while the silent interval was comparable to Short (20 ms). Results show a frontocentral MMN of comparable amplitude in all conditions. Thus, abstract pitch relations can be extracted even when the within-pair timing exceeds the integration period. Source analyses indicate MMN generators in the supratemporal cortex. Interestingly, they were located more anterior in Long Gap than in Short and Long Tone. Moreover, frontal generator activity was found for Long Gap and Long Tone. Thus, the way in which the system automatically registers irregular abstract pitch relations depends on the timing of the events to be linked. Pending that the current MMN data mirror established abstract rule representations coding the regular pitch relation, neural processes building these templates vary with timing.

The human central auditory system can automatically extract abstract regularities from a variant auditory input. To this end, temporarily separated events need to be related. This study tested whether the timing between events, falling either within or outside the temporal window of integration (~350 ms), impacts the extraction of abstract feature relations. We utilized tone pairs for which tones within but not across pairs revealed a constant pitch relation (e.g., pitch of second tone of a pair higher than pitch of first tone, while absolute pitch values varied across pairs). We measured the mismatch negativity (MMN; the brain’s error signal to auditory regularity violations) to second tones that rarely violated the pitch relation (e.g., pitch of second tone lower). A Short condition in which tone duration (90 ms) and stimulus onset asynchrony between the tones of a pair were short (110 ms) was compared to two conditions, where this onset asynchrony was long (510 ms). In the Long Gap condition, the tone durations were identical to Short (90 ms), but the silent interval was prolonged by 400 ms. In Long Tone, the duration of the first tone was prolonged by 400 ms, while the silent interval was comparable to Short (20 ms). Results show a frontocentral MMN of comparable amplitude in all conditions. Thus, abstract pitch relations can be extracted even when the within-pair timing exceeds the integration period. Source analyses indicate MMN generators in the supratemporal cortex. Interestingly, they were located more anterior in Long Gap than in Short and Long Tone. Moreover, frontal generator activity was found for Long Gap and Long Tone. Thus, the way in which the system automatically registers irregular abstract pitch relations depends on the timing of the events to be linked. Pending that the current MMN data mirror established abstract rule representations coding the regular pitch relation, neural processes building these templates vary with timing.:Introduction; Materials and methods; Results; Discussion; Conclusion