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| Author |
Awasthi, Bhuvanesh; Friedman, Jason; Williams, Mark A |
| Title |
Reach Trajectories Reveal Delayed Processing of Low Spatial Frequency Faces in Developmental Prosopagnosia |
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2012 |
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Cognitive Neuroscience |
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3 |
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2 |
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120-130 |
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Developmental prosopagnosia (DP) is characterized by a selective deficit in face recognition despite normal cognitive and neurological functioning. Previous research has established configural processing deficits in DP subjects. Low spatial frequency (LSF) information subserves configural face processing. Using hybrid stimuli, here we examined the evolution of perceptual dynamics and integration of LSF information by DP subjects while they pointed to high spatial frequency (HSF) face targets. Permutation analysis revealed a 230-ms delay in LSF processing by DP subjects as compared to controls. This delayed processing is likely to contribute to the difficulties associated with face recognition in DP subjects and is reflective of their alleged reliance on local rather than global features in face perception. These results suggest that quick and efficient processing of LSF information is critical for the development of normal face perception. |
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Penn State @ write.to.jason @ |
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Friedman, Jason; Flash, Tamar |
| Title |
Task-dependent selection of grasp kinematics and stiffness in human object manipulation |
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Journal Article |
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2007 |
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Cortex |
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43 |
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3 |
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444-460 |
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Object manipulation with the hand is a complex task. The task has redundancies at many levels, allowing many possibilities for the selection of grasp points, the orientation and posture of the hand, the forces to be applied at each fingertip and the impedance properties of the hand. Despite this inherent complexity, humans perform object manipulation nearly effortlessly. This article presents experimental findings of how humans grasp and manipulate objects, and examines the compatibility of grasps selected for specific tasks. This is accomplished by looking at the velocity transmission and force transmission ellipsoids, which represent the transmission ratios of the corresponding quantity from the joints to the object, as well as the stiffness ellipsoid which represents the directional stiffness of the grasp. These ellipsoids allow visualization of the grasp Jacobian and grasp stiffness matrices. The results show that the orientation of the ellipsoids can be related to salient task requirements. |
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Penn State @ write.to.jason @ |
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14 |
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| Author |
Awasthi, Bhuvanesh; Friedman, Jason; Williams, Mark |
| Title |
Faster, stronger, lateralized: Low spatial frequency information supports face processing |
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Journal Article |
| Year |
2011 |
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Neuropsychologia |
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49 |
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13 |
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3583-3590 |
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Distinct visual pathways are selectively tuned for processing specific spatial frequencies. Recently, Awasthi, Friedman and Williams (2011) reported fast categorisation of faces at periphery, arguing for primacy of low spatial frequency (LSF) information in face processing. However, previous studies have also documented rapid categorization of places and natural scenes. Here, we tested if the LSF advantage is face specific or also involved in place perception. We used visually guided reaching as a continuous behavioral measure to examine the processing of LSF and high spatial frequency (HSF) hybrids, presented at the periphery. Subjects reached out and touched targets and their movements were recorded. The trajectories revealed that LSF interference was both 95 ms earlier and stronger for faces than places and was lateralized to the left visual field. The early processing of LSF information supports the assumption that faces are prioritised and provides a (neural) framework for such specialised processing. |
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Penn State @ write.to.jason @ |
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25 |
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Awasthi, Bhuvanesh; Friedman, Jason; Williams, Mark A |
| Title |
Processing of low spatial frequency faces at periphery in choice reaching tasks |
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Journal Article |
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2011 |
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Neuropsychologia |
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49 |
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7 |
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2136-2141 |
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Various aspects of face processing have been associated with distinct ranges of spatial frequencies. Configural processing of faces depends chiefly on low spatial frequency (LSF) information whereas high spatial frequency (HSF) supports feature based processing. However, it has also been argued that face processing has a foveal-bias (HSF channels dominate the fovea). Here we used reach trajectories as a continuous behavioral measure to study perceptual processing of faces. Experimental stimuli were LSF–HSF hybrids of male and female faces superimposed and were presented peripherally and centrally. Subject reached out to touch a specified sex and their movements were recorded. The reaching trajectories reveal that there is less effect of (interference by) LSF faces at fovea as compared to periphery while reaching to HSF targets. These results demonstrate that peripherally presented LSF information, carried chiefly by magnocellular channels, enables efficient processing of faces, possibly via a retinotectal (subcortical) pathway. |
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24 |
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Zopf, Regine; Truong, Sandra; Finkbeiner, Matthew; Friedman, Jason; Williams, Mark A |
| Title |
Viewing and feeling touch modulates hand position for reaching |
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Journal Article |
| Year |
2011 |
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Neuropsychologia |
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49 |
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5 |
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1287–1293 |
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Action requires knowledge of our body location in space. Here we asked if interactions with the external world prior to a reaching action influence how visual location information is used. We investigated if the temporal synchrony between viewing and feeling touch modulates the integration of visual and proprioceptive body location information for action. We manipulated the synchrony between viewing and feeling touch in the Rubber Hand Illusion paradigm prior to participants performing a ballistic reaching task to a visually specified target. When synchronous touch was given, reaching trajectories were significantly shifted compared to asynchronous touch. The direction of this shift suggests that touch influences the encoding of hand position for action. On the basis of this data and previous findings, we propose that the brain uses correlated cues from passive touch and vision to update its own position for action and experience of self-location. |
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Penn State @ write.to.jason @ |
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