Distractor suppression is independent of target selection and fluctuates rhythmically across time
Universität zu Lübeck, Germany
Although well-established models of attention rest on the assumption that irrelevant sensory information is filtered out, the neural implementation of such a filter mechanism is unclear. I will present behavioural and electroencephalography (EEG) data of two recent studies that support the autonomy of neural distractor suppression mechanisms and the rhythmic modulation of distractor suppression across time. First, in a pre-registered auditory spatial attention study (https://osf.io/bv7zs), we decoupled target selection from distractor suppression. In line with pre-registered hypotheses, we found two sign-reversed lateralized alpha oscillatory responses (~10 Hz) reflecting target selection versus distractor suppression. Critically, these alpha responses were reliable, independent of each other, and generated in more anterior, frontal regions for suppression versus selection. These results suggest that the neurobiological foundation of attention implies a selection-independent alpha oscillatory mechanism to suppress distraction. Second, in a pitch comparison task, we systematically varied the onset time of a task-irrelevant 25-Hz modulated tone sequence, which was presented in-between two to-be-compared target tones. Two metrics of distraction were utilized: On the level of behaviour, perceptual sensitivity (d’) in pitch comparison inversely relates to the degree of distraction, with decreasing sensitivity signifying increasing distraction. Second, on the neural level, the 25-Hz amplitude in the EEG response to the distractor reflects distractor encoding. We found that distractor onset time rhythmically modulated both metrics of distraction at frequencies 3–5 Hz. I will discuss how and to what extent results of these studies advance our understanding of the neural and psychological basis of distractor suppression.
Rhythmic modulation of visual perception through cross-modal entrainment
1Department of Experimental Psychology, University of Oxford, UK; 2Oxford Centre for Human Brain Activity, Wellcome Centre for Integrative Neuroimaging, Department of Psychiatry, University of Oxford, UK; 3Institute for Brain and Behavior Amsterdam, Department of Experimental and Applied Psychology, Vrije Universiteit Amsterdam, The Netherlands
Our sensory environment is filled with rhythmic structures to which neural activity can become synchronised to guide adaptive behaviour. In natural settings, sensory signals are rarely restricted to one sensory modality. It has been suggested that the synchronisation between the incoming sensory streams in different modalities and brain rhythms is important to facilitate information transfer across sensory modalities. Here, we investigated the cross-modal influences of a continuous auditory frequency-modulated (FM) sound on visual perception and visual cortical activity. In a human electroencephalography (EEG) study (N = 28), participants listened to a 3-Hz FM stimulus of 2 second duration and discriminated the orientation of a Gabor grating presented at threshold. Grating onset varied according to the phase of the auditory modulation and visual performance was found to co-vary accordingly. We further show that this rhythmic modulation in visual perception is related to an accompanying rhythmic modulation of neural activity recorded over visual areas. Importantly, in our task, perceptual and neural visual modulations occurred without any abrupt and salient onsets in the energy of the auditory stimulation and without any rhythmic structure in the visual stimulus. The current work suggests that continuous auditory fluctuations in the natural environment can provide a pacing signal for neural activity and thereby influence behavioural performance across sensory modalities.
EEG insights into neural tracking of target and distractor streams in continuous, naturalistic auditory scenes
Carl von Ossietzky Universität Oldenburg, Germany
Listening to speech in adverse, noisy environments can be a difficult task for listeners with normal-hearing (NH), but significantly more so for hearing-impaired (HI) individuals. Here we investigate selective attention to speech and how different factors may influence it in normal-hearing and hearing-impaired individuals. In our investigation we use electroencephalography (EEG) and auditory attention decoding approach which relies on the fact that neural signals synchronize to continuous, running auditory stimulus, more so to attended than to ignored one. Our NH and aided HI participants listened to an audiobook presented in noise. We manipulated noise level (easy vs. hard listening), but also participants’ motivation by providing a monetary reward. Both participant groups performed better in easier listening condition, which was reflected in faster EEG impulse responses to speech. NH participants behaviorally performed better than HI, but increase in motivation indeed improved performance of HI group. In a separate study we also showed on neural level that selective attention abilities of HI participants improve with help of visual cues, such as speaker's lip movements. On behavioral level we showed that this increase is related to the amount of hearing loss. We suggest that auditory selective attention should be investigated in context of cues and scenarios that are common in every-day life as we do observe their influence on cortical speech tracking. In HI individuals these effects are even stronger than in NH and ecological approaches are needed to fully explain stream segregation and selective attention mechanisms.
Target selection and distractor suppression in visual working memory
Leibniz Research Centre for Working Environment and Human Factors, Deutschland
Prioritization of information stored in working memory facilitates performance. However, there is an ongoing debate on the attentional sub-processes underlying this behavioral benefit. We investigated respective electrophysiological correlates of by means of a retroactive cuing task and oscillatory EEG parameters. In order to disentangle target- vs. distractor-related attentional processes, the to-be-memorized information was presented in a way that posterior hemispheric asymmetries in oscillatory power could be unambiguously linked to the processing of laterally presented visual stimuli. A retroactive cue indicated a subset of visual objects stored in working memory as task relevant. A contralateral increase of posterior alpha power (8-13 Hz) was evident when the non-cued working memory content was presented laterally. Furthermore, posterior alpha was decreased contralateral to the position of cued contents, but this effect was also evident when a neutral cue indicated all working memory representations as further on task-relevant. This indicates that retroactive attentional orienting is largely based on an inhibitory control process for withdrawing the focus of attention from irrelevant locations.
Learning to ignore: Expectation-dependent distractor suppression
Vrije Universiteit Amsterdam, Netherlands, The
Much insight has been gained into how selective attention may filter information processing at the neural level, by directly boosting relevant information (target facilitation), and/or by suppressing irrelevant information (distractor inhibition). Yet, there is still debate as to whether target facilitation and distractor inhibition are simply two sides of the same coin or whether they are controlled by distinct neural mechanisms. Recent work indicates that distractor suppression only emerges when distractor information can be (implicitly) predicted, suggesting that distractor suppression is in particular expectation dependent. I will discuss recent findings from behavioral and EEG studies examaning how expectations about upcoming target or distractor locations and/or features influence facilitatory and inhibitory effects of attention on visual information processing and representation using ERPs, multivariate decoding analyses, and inverted encoding models. Collectively, these confirm an important role for alpha oscillatory activity in top-down biasing of attention to, and tuning of representations of target locations. Yet, they also show that target facilitation and distractor suppression are differentially influenced by expectations, and rely at least partly on different neural mechanisms. Specifically, we did not find any changes in preparatory neural activity as a function of spatial distractor expectations, but a strongly reduced Pd, an ERP index of inhibition. Also, the expected distractor features could not only be decoded pre-stimulus, but their representation differed from the representation of that same feature when part of the target. These results demonstrate that neural effects of expectations critically depend on the task relevance and dimension (spatial, feature) of predictions.