Attention to Speed of Motion, Speed Discrimination, and Task Difficulty: An fMRI Study

University of Leuven, Louvain, Flanders, Belgium
NeuroImage (Impact Factor: 6.36). 07/2000; 11(6 Pt 1):612-23. DOI: 10.1006/nimg.2000.0587
Source: PubMed


We studied the functional neuroanatomy of attention to speed of motion using functional magnetic resonance imaging in eight healthy subjects, who performed a speed discrimination (SID) task using a random textured pattern moving at a reference speed of 6 deg/s. During the control condition (DIM), with retinal stimulation identical to that during SID, subjects detected the dimming of the central fixation point. Attention to speed (SID compared to DIM) activated mainly ventral V3 and V4, dorsal V3 and V3A. Compared to a fixation control condition, speed discrimination recruited a large visuomotor network, including hMT/V5+. However, hMT/V5+ was only marginally more active during speed discrimination than during dimming detection. Thus hMT/V5+ is involved in speed discrimination, in line with the speed discrimination impairments following hMT/V5+ lesions, but our results suggest that this activity simply reflects the processing of motion rather than attention to speed. Manipulating the difficulty of the speed discrimination task over a large range of the psychometric curve revealed that increasing difficulty linearly increases activity in right frontal regions, as well as in lateral occipital and dorsal parietal regions. A weak effect of difficulty was also observed in dorsal V3.

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Available from: Stefan Sunaert
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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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    • "In this experiment, we considered that our three tasks may inequitably tap attentional resources. Actively attending to motion features is known to boost the BOLD response in hMT for simple RDK displays (Saenz et al., 2002; Sunaert et al., 2000), and because biological motion is more inherently " interesting " than the simpler motion stimuli, subjects may be more motivated to analyze the complex features (which may be either local, dynamic features, or global structural features; e.g. Lu and Liu, 2006; Thurman et al., 2010). "
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    ABSTRACT: The brain systems that support motion perception are some of the most studied in the primate visual system, with apparent specialization in the middle temporal area (hMT+ in humans, MT or V5 in monkeys). Even with this specialization, it is safe to assume that the hMT+ interacts with other brain systems as visual tasks demand. Here we have measured those interactions using a specialized case of structure-from-motion, point-light biological motion. We have measured the BOLD-contrast response functions in hMT+ for translating and biological motion. Even after controlling for task and attention, we find the BOLD response for translating motion to be largely insensitive to contrast, but the BOLD response for biological motion to be strongly contrast dependent. To track the brain systems involved in these interactions, we probed for brain areas outside of the hMT+ with the same contrast dependent neural response. This analysis revealed brain systems known to support form perception (including ventral temporal cortex and the superior temporal sulcus). We conclude that the contrast dependent response in hMT+ likely reflects stimulus complexity, and may be evidence for interactions with shape-based brain systems.
    Full-text · Article · May 2012 · Brain research
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    • "In the human brain, some functional imaging studies have implicated the MT complex in speed discrimination (e.g. [64]), but this finding is not consistent across studies (see [65] for negative evidences). Interestingly, and in line with present results, McKeefry and coll. "
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    ABSTRACT: Neuroimaging studies have identified several motion-sensitive visual areas in the human brain, but the time course of their activation cannot be measured with these techniques. In the present study, we combined electrophysiological and neuroimaging methods (including retinotopic brain mapping) to determine the spatio-temporal profile of motion-onset visual evoked potentials for slow and fast motion stimuli and to localize its neural generators. We found that cortical activity initiates in the primary visual area (V1) for slow stimuli, peaking 100 ms after the onset of motion. Subsequently, activity in the mid-temporal motion-sensitive areas, MT+, peaked at 120 ms, followed by peaks in activity in the more dorsal area, V3A, at 160 ms and the lateral occipital complex at 180 ms. Approximately 250 ms after stimulus onset, activity fast motion stimuli was predominant in area V6 along the parieto-occipital sulcus. Finally, at 350 ms (100 ms after the motion offset) brain activity was visible again in area V1. For fast motion stimuli, the spatio-temporal brain pattern was similar, except that the first activity was detected at 70 ms in area MT+. Comparing functional magnetic resonance data for slow vs. fast motion, we found signs of slow-fast motion stimulus topography along the posterior brain in at least three cortical regions (MT+, V3A and LOR).
    Full-text · Article · Apr 2012 · PLoS ONE
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