Feature-Based Attention Modulates Direction-Selective Hemodynamic Activity Within Human MT

Department of Neurology and Centre for Advanced Imaging, Otto-von-Guericke-University, Leipziger Str. 44, 39120 Magdeburg, Germany.
Human Brain Mapping (Impact Factor: 5.97). 12/2011; 32(12):2183-92. DOI: 10.1002/hbm.21180
Source: PubMed


Attending to the spatial location or to nonspatial features of a stimulus modulates neural activity in cortical areas that process its perceptual attributes. The feature-based attentional selection of the direction of a moving stimulus is associated with increased firing of individual neurons tuned to the direction of the movement in area V5/MT, while responses of neurons tuned to opposite directions are suppressed. However, it is not known how these multiplicatively scaled responses of individual neurons tuned to different motion-directions are integrated at the population level, in order to facilitate the processing of stimuli that match the perceptual goals. Using functional magnetic resonance imaging (fMRI) the present study revealed that attending to the movement direction of a dot field enhances the response in a number of areas including the human MT region (hMT) as a function of the coherence of the stimulus. Attending the opposite direction, however, lead to a suppressed response in hMT that was inversely correlated with stimulus-coherence. These findings demonstrate that the multiplicative scaling of single-neuron responses by feature-based attention results in an enhanced direction-selective population response within those cortical modules that processes the physical attributes of the attended stimuli. Our results provide strong support for the validity of the "feature similarity gain model" on the integrated population response as quantified by parametric fMRI in humans.

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Available from: Christian Michael Stoppel
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    • "This global effect of visual feature-based attention has also been shown in human psychophysical studies (Rossi and Paradiso, 1995; Sàenz et al., 2003), suggesting a higher accuracy for matching features. Human imaging studies (Saenz et al., 2002; Stoppel et al., 2011) extend these observations, reporting an increased fMRI response to an ignored stimulus of a given feature upon attention to a distant stimulus with the same feature compared to one with a different feature (Saenz et al., 2002). The feature-similarity gain model (Treue and Martínez-Trujillo, 1999) proposes a unified account for spatial and feature-based attentional modulation. "
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    ABSTRACT: In a reaction time study of human tactile orientation detection the effects of spatial attention and feature-based attention were investigated. Subjects had to give speeded responses to target orientations (parallel and orthogonal to the finger axis) in a random stream of oblique tactile distractor orientations presented to their index and ring fingers. Before each block of trials, subjects received a tactile cue at one finger. By manipulating the validity of this cue with respect to its location and orientation (feature), we provided an incentive to subjects to attend spatially to the cued location and only there to the cued orientation. Subjects showed quicker responses to parallel compared to orthogonal targets, pointing to an orientation anisotropy in sensory processing. Also, faster reaction times (RTs) were observed in location-matched trials, i.e., when targets appeared on the cued finger, representing a perceptual benefit of spatial attention. Most importantly, RTs were shorter to orientations matching the cue, both at the cued and at the uncued location, documenting a global enhancement of tactile sensation by feature-based attention. This is the first report of a perceptual benefit of feature-based attention outside the spatial focus of attention in somatosensory perception. The similarity to effects of feature-based attention in visual perception supports the notion of matching attentional mechanisms across sensory domains.
    Full-text · Article · Jul 2014 · Frontiers in Human Neuroscience
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    • "Nevertheless , the discrimination of simple motion sub-features like speed or direction does not necessarily rely on processing in area MT and can easily be performed in lower tier motion sensitive areas such as V3 and V3a (Sunaert et al., 1999; Tootell et al., 1997). The activity in these areas has been shown to be modulated by visual attention (Buchel et al., 1998; Stoppel et al., 2011; Sunaert et al., 2000). For more complex properties such as motion coherence it is less clear in which areas the processing takes place. "
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    ABSTRACT: Attention to specific features of moving visual stimuli modulates the activity in human cortical motion sensitive areas. In this study we employed combined event-related electrophysiological, magnetencephalographic (EEG, MEG) and hemodynamic functional magnetic resonance imaging (fMRI) measures of brain activity to investigate the precise time course and the neural correlates of feature-based attention to speed and coherence. Subjects were presented with an aperture of dots randomly moving either slow or fast, at the same time displaying a high or low level of coherence. The task was to attend either the speed or the coherence and press a button upon the high speed or high coherence stimulus respectively. When attention was directed to the speed of motion enhanced neural activity was found in the dorsal visual area V3a and in the IPL, areas previously shown to be specialized for motion processing. In contrast, when attention was directed to the coherence of motion significant hemodynamic activity was observed in the parietal areas fIPS and SPL that are specialized for the processing of complex motion patterns. Concurrent recordings of the event-related electro- and magnetencephalographic responses revealed that the speed-related attentional modulations of activity occurred at an earlier time range (around 240-290ms), while the coherence-related ones occurred later (around 320-370ms) post-stimulus. The current results suggest that the attentional selection of motion features modulates neural processing in the lowest-tier regions required to perform the task-critical discrimination.
    Full-text · Article · Sep 2012 · NeuroImage
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    • "Neural responses elicited by spatially unattended task-irrelevant probes were modulated as a function of the degree of similarity between their movement direction and the task-relevant movement direction in the attended visual field. This provides strong support for the ''feature similarity gain model " at the level of integrated population responses (Treue and Martínez Trujillo, 1999; Stoppel et al., 2011). Importantly , the global spread of feature-based attention does not occur suddenly following feature selection but rather appears to be a dynamic time-consuming process. "
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    ABSTRACT: Attentional selection on the basis of nonspatial stimulus features induces a sensory gain enhancement by increasing the firing-rate of individual neurons tuned to the attended feature, while responses of neurons tuned to opposite feature-values are suppressed. Here we recorded event-related potentials (ERPs) and magnetic fields (ERMFs) in human observers to investigate the underlying neural correlates of feature-based attention at the population level. During the task subjects attended to a moving transparent surface presented in the left visual field, while task-irrelevant probe stimuli executing brief movements into varying directions were presented in the opposite visual field. ERP and ERMF amplitudes elicited by the unattended task-irrelevant probes were modulated as a function of the similarity between their movement direction and the task-relevant movement direction in the attended visual field. These activity modulations reflecting globally enhanced processing of the attended feature were observed to start not before 200 ms poststimulus and were localized to the motion-sensitive area hMT. The current results indicate that feature-based attention operates in a global manner but needs time to spread and provide strong support for the feature-similarity gain model.
    Full-text · Article · Jul 2012 · The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
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