Cortical processing of musical pitch as reflected by behavioural and electrophysiological evidence

In a musical context, the pitch of sounds is encoded according to domain-general principles not confined to music or even to audition overall but common to other perceptual and cognitive processes (such as multiple pattern encoding and feature integration), and to domain-specific and culture-specific properties related to a particular musical system only (such as the pitch steps of the Western tonal system). The studies included in this thesis shed light on the processing stages during which pitch encoding occurs on the basis of both domain-general and music-specific properties, and elucidate the putative brain mechanisms underlying pitch-related music perception. Study I showed, in subjects without formal musical education, that the pitch and timbre of multiple sounds are integrated as unified object representations in sensory memory before attentional intervention. Similarly, multiple pattern pitches are simultaneously maintained in non-musicians' sensory memory (Study II). These findings demonstrate the degree of sophistication of pitch processing at the sensory memory stage, requiring neither attention nor any special expertise of the subjects. Furthermore, music- and culture-specific properties, such as the pitch steps of the equal-tempered musical scale, are automatically discriminated in sensory memory even by subjects without formal musical education (Studies III and IV). The cognitive processing of pitch according to culture-specific musical-scale schemata hence occurs as early as at the sensory-memory stage of pitch analysis. Exposure and cortical plasticity seem to be involved in musical pitch encoding. For instance, after only one hour of laboratory training, the neural representations of pitch in the auditory cortex are altered (Study V). However, faulty brain mechanisms for attentive processing of fine-grained pitch steps lead to inborn deficits in music perception and recognition such as those encountered in congenital amusia (Study VI). These findings suggest that predispositions for exact pitch-step discrimination together with long-term exposure to music govern the acquisition of the automatized schematic knowledge of the music of a particular culture that even non-musicians possess.

Human brain mechanisms of auditory and audiovisual selective attention

Selective attention refers to the process in which certain information is actively selected for conscious processing, while other information is ignored. The aim of the present studies was to investigate the human brain mechanisms of auditory and audiovisual selective attention with functional magnetic resonance imaging (fMRI), electroencephalography (EEG) and magnetoencephalography (MEG). The main focus was on attention-related processing in the auditory cortex. It was found that selective attention to sounds strongly enhances auditory cortex activity associated with processing the sounds. In addition, the amplitude of this attention-related modulation was shown to increase with the presentation rate of attended sounds. Attention to the pitch of sounds and to their location appeared to enhance activity in overlapping auditory-cortex regions. However, attention to location produced stronger activity than attention to pitch in the temporo-parietal junction and frontal cortical regions. In addition, a study on bimodal attentional selection found stronger audiovisual than auditory or visual attention-related modulations in the auditory cortex. These results were discussed in light of Näätänen s attentional-trace theory and other research concerning the brain mechanisms of selective attention.

Investigating online reading with eye tracking and EEG : The influence of text format, reading task and parafoveal stimuli on reading processes

Research on reading has been successful in revealing how attention guides eye movements when people read single sentences or text paragraphs in simplified and strictly controlled experimental conditions. However, less is known about reading processes in more naturalistic and applied settings, such as reading Web pages. This thesis investigates online reading processes by recording participants eye movements. The thesis consists of four experimental studies that examine how location of stimuli presented outside the currently fixated region (Study I and III), text format (Study II), animation and abrupt onset of online advertisements (Study III), and phase of an online information search task (Study IV) affect written language processing. Furthermore, the studies investigate how the goal of the reading task affects attention allocation during reading by comparing reading for comprehension with free browsing, and by varying the difficulty of an information search task. The results show that text format affects the reading process, that is, vertical text (word/line) is read at a slower rate than a standard horizontal text, and the mean fixation durations are longer for vertical text than for horizontal text. Furthermore, animated online ads and abrupt ad onsets capture online readers attention and direct their gaze toward the ads, and distract the reading process. Compared to a reading-for-comprehension task, online ads are attended to more in a free browsing task. Moreover, in both tasks abrupt ad onsets result in rather immediate fixations toward the ads. This effect is enhanced when the ad is presented in the proximity of the text being read. In addition, the reading processes vary when Web users proceed in online information search tasks, for example when they are searching for a specific keyword, looking for an answer to a question, or trying to find a subjectively most interesting topic. A scanning type of behavior is typical at the beginning of the tasks, after which participants tend to switch to a more careful reading state before finishing the tasks in the states referred to as decision states. Furthermore, the results also provided evidence that left-to-right readers extract more parafoveal information to the right of the fixated word than to the left, suggesting that learning biases attentional orienting towards the reading direction.