Task-Dependent Activations of Human Auditory Cortex during Pitch Discrimination and Pitch Memory Tasks

Abstract

). However, the task dependence of AC activations has not been systematically investigated. In the present study, we applied high-resolution functional magnetic resonance imaging of the AC and adjacent areas to compare activations during pitch discrimination and n-back pitch memory tasks that were varied parametrically in difficulty. We found that anterior AC activations were increased during discrimination but not during memory tasks, while activations in the inferior parietal lobule posterior to the AC were enhanced during memory tasks but not during discrimination. We also found that wide areas of the anterior AC and anterior insula were strongly deactivated during the pitch memory tasks. While these results are consistent with the proposition that the anterior and posterior AC belong to functionally separate auditory processing streams, our results show that this division is present also between tasks using spatially invariant sounds. Together, our results indicate that activations of human AC are strongly dependent on the characteristics of the behavioral task.

Noise in Brain Activity Engenders Perception and Influences Discrimination Sensitivity

“…The present results are distinct from the literature reporting differential behavioral and brain responses to physically identical stimuli, including phenomena associated with binocular rivalry (Tong et al, 2006), ambiguous multistable stimuli (Haynes et al, 2005;Sterzer et al, 2009;Britz et al, 2011), or variations in the instruction about which stimuli characteristics participants had to attend (Rinne et al, 2009). The stimuli in all of these cases indeed contained the physical information that participants perceived across the experimental conditions.…”

“…Dissociations between observers' responses and physical stimuli resulted from spontaneous or experimentally induced modulation of selective attention, in turn determining which stimulus characteristic observers attended to and consciously perceived. For instance, in a recent neuroimaging study on pitch processing, Rinne et al (2009) showed that task instructions modulated brain responses within low-level auditory cortices to the same stimuli in a condition involving attending to different characteristics of the stimuli, namely pitch differences, or to the sequence between the stimuli. By contrast, the discrimination on the identical stimuli in our study was to be done on the same dimension across the experimental conditions, and the value of this dimension did not change; there was no acoustic information allowing participants to perceive a given stimulus as being of higher or lower pitch or longer or shorter duration.…”

“…Behavioral and brain responses to identical stimuli can vary depending on experimental parameters, for example, which physical dimension of the stimulus observers are instructed to attend (Rinne et al, 2009) or the context of stimulus presentation (van Dijk and Backes, 2003). In the absence of any experimental manipulation, spontaneous variations in attention also dramatically impact behavioral and brain responses to ambiguous stimuli (Haynes et al, 2005;Sterzer et al, 2009).…”

Acoustical and categorical tasks differently modulate activations of human auditory cortex to vowels

“…Although isolated vowels lack many key features of speech (e.g., fast transitions in consonant-vowel syllables), vowels can be used to study the basis of speech processing in a controlled manner. This is important because activations in auditory cortex (AC) and other cortical areas are strongly modulated by attention and task (Hall et al, 2000;Petkov et al, 2004;Rinne, Koistinen, Salonen, & Alho, 2009;Rinne, Koistinen, Talja, Wikman, & Salonen, 2012). As native speech is often hard to ignore, such effects are easier to control using isolated vowels (no word-level semantics) than words and phrases.…”

“…In 2-back tasks, subjects indicated when the vowel pair belonged to the same category as the one presented two trials before. Based on previous studies, we expected that this paradigm would reveal distinct activation patterns depending on the task and depending on the prototypic (Pr vs. NPr) or phonemic (e.g., NPr vs. NPh) status of the vowels (Guenther et al, 2004;Rinne et al, 2009). In particular, we tested the novel hypothesis that activations to vowels during the vowel discrimination and category discrimination tasks performed on identical stimuli would differ so that activations during the category discrimination task would be more similar to those during the 2-back task.…”