Modulation of response patterns in human auditory cortex during a target detection task: An intracranial electrophysiology study

Abstract

Selective attention enhances cortical activity representing an attended sound stream in human posterolateral superior temporal gyrus (PLST). It is unclear, however, what mechanisms are associated with a target detection task that necessitates sustained attention (vigilance) to a sound stream. We compared responses elicited by target and non-target sounds, and to sounds presented in a passive-listening paradigm. Subjects were neurosurgical patients undergoing invasive monitoring for medically refractory epilepsy. Stimuli were complex tones, band-limited noise bursts and speech syllables. High gamma cortical activity (70–150 Hz) was examined in all subjects using subdural grid electrodes implanted over PLST. Additionally, responses were measured from depth electrodes implanted within Heschl’s gyrus (HG) in one subject. Responses to target sounds recorded from PLST were increased when compared to responses elicited by the same sounds when they were not-targets, and when they were presented during passive listening. Increases in high gamma activity to target sounds occurred during later portions (after 250 ms) of the response. These increases were related to the task and not to detailed stimulus characteristics. In contrast, earlier activity that did not vary across conditions did represent stimulus acoustic characteristics. Effects observed on PLST were not noted in HG. No consistent effects were noted in the averaged evoked potentials in either cortical region. We conclude that task dependence modulates later activity in PLST during vigilance. Later activity may represent feedback from higher cortical areas. Study of concurrently recorded activity from frontoparietal areas is necessary to further clarify task-related modulation of activity on PLST.

Sound identification in human auditory cortex: Differential contribution of local field potentials and high gamma power as revealed by direct intracranial recordings

“…In the current study, classification performance was superior when features of the LFP were analyzed. In contrast, in an earlier report, high gamma activity within PLST, but not the AEP, was modulated strongly by attention and behavioral task (Nourski et al, 2014b; Steinschneider et al, 2014). …”

“…For instance, this analysis has helped characterize the functional representation of phonetic categories used in speech (Pasley et al, 2011; Mesgarani et al, 2014) and the powerful effects of selective attention in modulating auditory cortical activity when listening to competing speech streams (e.g., Mesgarani and Chang, 2012). Analysis of high gamma activity has also demonstrated tiered effects of attention across auditory and auditory-related cortical areas (Nourski et al, 2014b; Steinschneider et al, 2014). All these findings parallel those obtained from patterns of spiking activity in experimental animals (e.g., Fritz et al, 2003; Mesgarani et al, 2008; Tsunada et al, 2011; Steinschneider et al, 2013).…”

Evidence for cue-independent spatial representation in the human auditory cortex during active listening

“…Topographically, these results are consistent with the locus of modulations observed during auditory attention (33,40,49) and spatial discrimination tasks (47,60). Despite significant differences in experimental design and analysis, the results reported here defining regional sensitivity to sound location and auditory task processing are strikingly similar to those reported by Häk-kinen et al (43).…”

“…Task-dependent modulation of AC activity has been demonstrated across a variety of experimental paradigms and methodological techniques, including animal electrophysiology (30)(31)(32), human electrocorticography (33,34), EEG/MEG (35)(36)(37)(38), monkey fMRI (39), and human fMRI (40)(41)(42)(43)(44)(45). The current study aimed to ascertain whether spatial listening alters the form of ITD and ILD sensitivity in human AC.…”

Differential activation of human core, non-core and auditory-related cortex during speech categorization tasks as revealed by intracranial recordings

“…Studies have demonstrated that early high gamma activity reflects more automatic processing that helps represent specific spectral characteristics of tone stimuli (Nourski et al, 2014a,b), as well as the remapping of acoustic speech characteristics to those representing phonetic categories (Chang et al, 2010; Travis et al, 2013; Mesgarani et al, 2014). In contrast, later high gamma activity on PLST could be strongly modulated by task requirements.…”