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| Author | Kapur, Shweta; Friedman, Jason; Zatsiorsky, Vladimir M.; Latash, Mark L. | ||||
| Title | Finger interaction in a three-dimensional pressing task | Type | Journal Article | ||
| Year | 2010 | Publication | Experimental Brain Research | Abbreviated Journal | |
| Volume | 203 | Issue | 1 | Pages | 101-118 |
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Abstract  |
Accurate control of forces produced by the fingers is essential for performing object manipulation. This study examines the indices of finger interaction when accurate time profiles of force are produced in different directions, while using one of the fingers or all four fingers of the hand. We hypothesized that patterns of unintended force production among shear force components may involve features not observed in the earlier studies of vertical force production. In particular, we expected to see unintended forces generated by non-task fingers not in the direction on the instructed force but in the opposite direction as well as substantial force production in directions orthogonal to the instructed direction. We also tested a hypothesis that multi-finger synergies, quantified using the framework of the uncontrolled manifold hypothesis, will help reduce across-trials variance of both total force magnitude and direction. Young, healthy subjects were required to produce accurate ramps of force in five different directions by pressing on force sensors with the fingers of the right (dominant) hand. The index finger induced the smallest unintended forces in non-task fingers. The little finger showed the smallest unintended forces when it was a non-task finger. Task fingers showed substantial force production in directions orthogonal to the intended force direction. During four-finger tasks, individual force vectors typically pointed off the task direction, with these deviations nearly perfectly matched to produce a resultant force in the task direction. Multi-finger synergy indices reflected strong co-variation in the space of finger modes (commands to fingers) that reduced variability of the total force magnitude and direction across trials. The synergy indices increased in magnitude over the first 30% of the trial time and then stayed at a nearly constant level. The synergy index for stabilization of total force magnitude was higher for shear force components as compared to the downward pressing force component. The results suggest complex interactions between enslaving and synergic force adjustments, possibly reflecting the experience with everyday prehensile tasks. For the first time, the data document multi-finger synergies stabilizing both shear force magnitude and force vector direction. These synergies may play a major role in stabilizing the hand action during object manipulation. |
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| Notes | in press | Approved | no | ||
| Call Number | Penn State @ write.to.jason @ | Serial | 20 | ||
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| Author | Zopf, Regine; Truong, Sandra; Finkbeiner, Matthew; Friedman, Jason; Williams, Mark A | ||||
| Title | Viewing and feeling touch modulates hand position for reaching | Type | Journal Article | ||
| Year | 2011 | Publication | Neuropsychologia | Abbreviated Journal | |
| Volume | 49 | Issue | 5 | Pages | 1287–1293 |
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| Abstract |
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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| Notes | Approved | no | |||
| Call Number | Penn State @ write.to.jason @ | Serial | 23 | ||
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| Author | Finkbeiner, Matthew; Friedman, Jason | ||||
| Title | The flexibility of nonconsciously deployed cognitive processes: Evidence from masked congruence priming | Type | Journal Article | ||
| Year | 2011 | Publication | PLoS ONE | Abbreviated Journal | |
| Volume | 6 | Issue | 2 | Pages | e17095 |
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Background It is well accepted in the subliminal priming literature that task-level properties modulate nonconscious processes. For example, in tasks with a limited number of targets, subliminal priming effects are limited to primes that are physically similar to the targets. In contrast, when a large number of targets are used, subliminal priming effects are observed for primes that share a semantic (but not necessarily physical) relationship with the target. Findings such as these have led researchers to conclude that task-level properties can direct nonconscious processes to be deployed exclusively over central (semantic) or peripheral (physically specified) representations. Principal Findings We find distinct patterns of masked priming for “novel” and “repeated” primes within a single task context. Novel primes never appear as targets and thus are not seen consciously in the experiment. Repeated primes do appear as targets, thereby lending themselves to the establishment of peripheral stimulus-response mappings. If the source of the masked priming effect were exclusively central or peripheral, then both novel and repeated primes should yield similar patterns of priming. In contrast, we find that both novel and repeated primes produce robust, yet distinct, patterns of priming. Conclusions Our findings indicate that nonconsciously elicited cognitive processes can be flexibly deployed over both central and peripheral representations within a single task context. While we agree that task level properties can influence nonconscious processes, our findings sharply constrain the extent of this influence. Specifically, our findings are inconsistent with extant accounts which hold that the influence of task-level properties is strong enough to restrict the deployment of nonconsciously elicited cognitive processes to a single type of representation (i.e. central or peripheral). |
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| Call Number | Penn State @ write.to.jason @ | Serial | 22 | ||
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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 | Type | Journal Article | ||
| Year | 2012 | Publication | Cognitive Neuroscience | Abbreviated Journal | |
| Volume | 3 | Issue | 2 | Pages | 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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| Notes | Approved | no | |||
| Call Number | Penn State @ write.to.jason @ | Serial | 27 | ||
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| Author | Awasthi, Bhuvanesh; Friedman, Jason; Williams, Mark | ||||
| Title | Faster, stronger, lateralized: Low spatial frequency information supports face processing | Type | Journal Article | ||
| Year | 2011 | Publication | Neuropsychologia | Abbreviated Journal | |
| Volume | 49 | Issue | 13 | Pages | 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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| Notes | Approved | no | |||
| Call Number | Penn State @ write.to.jason @ | Serial | 25 | ||
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