Functional organization of human auditory cortex during active auditory tasks
Year: 2018
Type: dissertation
Abstract: Previous imaging studies have shown that activation in human auditory cortex (AC) is strongly modulated during active listening tasks. However, the prevalent models of AC mainly focus on the processing of stimulus-specific information and speech and do not predict such task-dependent modulation. In the present thesis, functional magnetic resonance imaging was used to measure regional activation in AC during discrimination and n-back memory tasks in order to investigate the relationship between stimulus-specific and task-dependent processing (Study I) and inter-regional connectivity during rest and active tasks (Study III). In addition, source analysis of scalp-recorded event-related potentials was carried out to study the temporal dynamics of task-dependent activation in AC (Study II). In Study I, distinct stimulus-specific activation patterns to pitch-varying and location-varying sounds were similarly observed during visual (no directed auditory attention) and auditory tasks. This is consistent with the prevalent models which presume parallel and independent “what” (e.g. pitch) and “where” processing streams. As expected, discrimination and n-back memory tasks were associated with distinct task-dependent activation patterns. These activation patterns were independent of whether subjects performed pitch or location versions of these tasks. Thus, AC activation during discrimination and n-back memory tasks cannot be explained by enhanced stimulus-specific processing (of pitch and location). Consistently, Study II showed that the task-dependent effects in AC occur relatively late (200–700 ms from stimulus onset) compared to the latency of stimulus-specific pitch processing (0–200 ms). In Study III, the organization of human AC was investigated based on functional connectivity. Connectivity-based parcellation revealed a network structure that consisted of six modules in supratemporal plane, temporal lobe, and inferior parietal lobule in both hemispheres. Multivariate pattern analysis showed that connectivity within this network structure was significantly modulated during the presentation of sounds (visual task) and auditory task performance. Together the results of this thesis show that (1) activation in human AC strongly depends on the requirements of the listening task and that task-dependent modulation is not due to enhanced stimulus-specific processing, (2) regions in inferior parietal lobule play an important role in the processing of both task-irrelevant and task-relevant auditory information in human AC, and (3) the activation patterns in human AC during the presentation of task-irrelevant and task-relevant sounds cannot be fully explained by a hierarchical model in which information is processed in two parallel processing streams.
Source: Työväentutkimus Vuosikirja
Author: Suvi Häkkinen
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2811498689