Objective, reliable, and valid? Measuring auditory attention
Professor Jonas Obleser, University of Lübeck, Germany
Auditory attention is a fascinating feat. For example, it is most astonishing how our brain 'does away' with considerable differences in sound pressure between a behaviourally relevant sound source and other interferences. Meanwhile, auditory attention has remained this elusive phenomenon: do we really understand enough just yet of auditory attention to build machines that attend, or machines that help us attend? Illustrated by behavioural, electrophysiological, and functional imaging data from his own lab and others, Professor Obleser will take stock of the evidence: are top-down selective-attention abilities indeed a stable, trait-like feature of the individual listener, with predictable decline in older adults? And, what are we really getting from our current go-to neural measures of auditory attention, speech tracking aka 'neural entrainment' versus alpha-power fluctuations? Luckily, Professor Obleser will probably be out of time as the talk reaches the main question: what are we measuring when we measure auditory attention?
Auditory selective attention: lessons from distracting sounds
Dr Elana Golumbic, Bar Ilan University, Israel
A fundamental assumption in attention research is that, since processing resources are limited, the core function of attention is to manage these resources and allocate them among concurrent stimuli or tasks, according to current behavioural goals and environmental needs. However, despite decades of research, we still do not have a full characterisation of the nature these processing limitations, or ‘bottlenecks’ – ie what processes can be in performed in parallel and where the need for attentional selection kicks in. This question is particularly pertinent in the auditory system, which has been studied far less extensively than the visual system, and is proposed to have a wider capacity for parallel processing of incoming stimuli.
In this talk Dr Golumbic will discuss a series of experiments studying the depth of processing applied to task-irrelevant sounds and their neural encoding in auditory cortex. She will look at how this is affected by the acoustic properties, temporal structure, and linguistic structure of unattended sounds, as well as by overall acoustic load and task demands, in attempt to understand what levels suffer most from processing bottlenecks. In addition, she will discuss what we can learn about the capacity of parallel processing of auditory stimuli from pushing the system to its limits and requiring the division of attention among multiple concurrent inputs.
The neuro-computational architecture of auditory attention
Professor Elia Formisano, Maastricht University, The Netherlands
Auditory attention is a crucial component of real-life listening and is required, for instance, to enhance a particularly relevant aspect of a sound or to separate a sound of interest from noisy backgrounds. When listening to simple tones, attending to a certain frequency range induces a rapid and specific adaptation of neuronal tuning, which ultimately results in enhanced processing of that frequency range and suppression of the other frequencies. But which are the neural mechanisms enabling attentive selection and enhancement when listening to complex real-life sounds and scenes? At which levels of neural sound representation does attention operate? And how do these mechanisms depend on the specific behavioural requirements? High-resolution fMRI and computational modelling of sound representations both provide a relevant contribution to address these questions. Sub-millimetre fMRI enables distinguishing the activity and connectivity of neuronal populations across cortical layers non-invasively in humans (laminar fMRI). This is required for disentangling feedforward/feedback processing in primary and non-primary auditory areas and the communication between auditory and other areas (eg frontal areas). Modelling of sound representations allows formulating well-defined hypotheses on the nature of simple and complex features processed in the network of auditory areas and how the neural sensitivity for these features is affected by attention and behavioural task demands. The combination of laminar fMRI and sound representation models is thus ideally positioned to unravel the neural circuitry and the computational architecture of auditory attention in naturalistic listening scenarios.
How attention modulates processing of mildly degraded speech to influence perception and memory
Professor Ingrid Johnsrude, Western University, Canada
Professor Johnsrude and colleagues have previously demonstrated that, whereas the pattern of brain (fMRI) activity elicited by clearly spoken sentences does not seem to depend on attention, patterns are markedly different when attending or not to highly intelligible but degraded (6-band noise vocoded) sentences (Wild et al, J Neurosci, 2012). They have replicated and extended this work to sentences that, although slightly degraded (12-band noise vocoded), can be reported word-for-word with 100% accuracy. Even for these very intelligible materials, a marked dissociatation was observed in patterns of brain activity when people attended to these compared to when they were performing a multiple object tracking task. Furthermore, in both of these experiments, memory for degraded items was enhanced by attention, whereas memory for clear sentences was not, suggesting that even perfectly intelligible but degraded sentences are processed in a qualitatively different, attentionally gated, way, compared to clear sentences. Supported by a Canadian Institutes of Health Research operating grant (MOP 133450) and Canadian Natural Sciences and Engineering Research Council Discovery grant (3274292012).