Attention to speed of motion, speed discrimination, and task difficulty: an fMRI study.
ABSTRACT 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.
Full-textDOI: · Available from: Stefan Sunaert, May 30, 2015
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ABSTRACT: In the recent perceptual decision-making literature, a fronto-parietal network is typically reported to primarily represent the neural substrate of human perceptual decision-making. However, the view that only cortical areas are involved in perceptual decision-making has been challenged by several neurocomputational models which all argue that the basal ganglia play an essential role in perceptual decisions. To consolidate these different views, we conducted an Activation Likelihood Estimation (ALE) meta-analysis on the existing neuroimaging literature. The results argue in favor of the involvement of a frontal-parietal network in general perceptual decision-making that is possibly complemented by the basal ganglia, and modulated in substantial parts by task difficulty. In contrast, expectation of reward, an important aspect of many decision-making processes, shows almost no overlap with the general perceptual decision-making network.Frontiers in Human Neuroscience 06/2014; 8. DOI:10.3389/fnhum.2014.00445 · 2.90 Impact Factor
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ABSTRACT: Individuals with Autism Spectrum Disorder (ASD) appear to show a general face discrimination deficit across a range of tasks including social-emotional judgments as well as identification and discrimination. However, functional magnetic resonance imaging (fMRI) studies probing the neural bases of these behavioral differences have produced conflicting results: while some studies have reported reduced or no activity to faces in ASD in the Fusiform Face Area (FFA), a key region in human face processing, others have suggested more typical activation levels, possibly reflecting limitations of conventional fMRI techniques to characterize neuron-level processing. Here, we test the hypotheses that face discrimination abilities are highly heterogeneous in ASD and are mediated by FFA neurons, with differences in face discrimination abilities being quantitatively linked to variations in the estimated selectivity of face neurons in the FFA. Behavioral results revealed a wide distribution of face discrimination performance in ASD, ranging from typical performance to chance level performance. Despite this heterogeneity in perceptual abilities, individual face discrimination performance was well predicted by neural selectivity to faces in the FFA, estimated via both a novel analysis of local voxel-wise correlations, and the more commonly used fMRI rapid adaptation technique. Thus, face processing in ASD appears to rely on the FFA as in typical individuals, differing quantitatively but not qualitatively. These results for the first time mechanistically link variations in the ASD phenotype to specific differences in the typical face processing circuit, identifying promising targets for interventions.01/2013; 2:320-31. DOI:10.1016/j.nicl.2013.02.002
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ABSTRACT: We investigated the difference between brain activities in speeded and precisely timed responses to identical visual stimulus using fMRI. Stimulus used was a row of seven light-emitting diodes (LEDs) lightened up one after another with constant speed within a trial but with various speeds between trials. Subjects were asked to execute finger-thumb tapping with the right hand in response to the onset of the first LED light in the reaction time (RT) task and in anticipation of the onset of the last (i.e., seventh) LED light in the timing task. In control condition, they were asked to passively view the stimulus without motor response. Results showed that various movement-related areas including contralateral cingulate motor cortex were commonly activated for both tasks relative to the control condition, suggesting these structures are involved in general perception and response execution rather than specific function for speeded or precisely timed responses. In the RT task, the presupplementary motor area extending to the cingulate sulcus was activated more strongly than in the timing task probably to focus attention to the onset of the first LED light unpredictably presented after random foreperiods. The lateral occipital area extending to the temporo-parieto-occipital junction was activated more strongly in the timing task than in the RT task; the same area was deactivated in the RT task relative to the control condition. Auditory-related areas were also deactivated in the both tasks. This inter- and intramodal task-specific modification including deactivation underscores significance of the context for perception and action and can have an important role in dexterous or skilled performance.NeuroImage 05/2004; DOI:10.1016/S1053-8119(04)00170-3 · 6.13 Impact Factor