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I Fine

Publications and source records attributed to I Fine.

9 recordsLinked to original sources
PubMed2001

Visual stimuli activate auditory cortex in the deaf.

Previous brain imaging studies have demonstrated responses to tactile and auditory stimuli in visual cortex of blind subjects, suggesting that removal of one sensory modality leads to neural reorganization of the remaining modalities. To investigate whether similar 'cross-modal' plasticity occurs in human auditory cortex, we used functional magnetic resonance imaging (fMRI) to measure visually evoked activity in auditory areas of both early-deafened and hearing individuals. Here we find that deaf subjects exhibit activation in a region of the right auditory cortex, corresponding to Brodmann's areas 42 and 22, as well as in area 41 (primary auditory cortex), demonstrating that early deafness results in the processing of visual stimuli in auditory cortex.

Adult↗
PubMed2000

Perceptual learning for a pattern discrimination task.

Our goal was to differentiate low and mid level perceptual learning. We used a complex grating discrimination task that required observers to combine information across wide ranges of spatial frequency and orientation. Stimuli were 'wicker'-like textures containing two orthogonal signal components of 3 and 9 c/deg. Observers discriminated a 15% spatial frequency shift in these components. Stimuli also contained four noise components, separated from the signal components by at least 45 degrees of orientation or approximately 2 octaves in spatial frequency. In Experiment 1 naive observers were trained for eight sessions with a four-alternative same-different forced choice judgment with feedback. Observers showed significant learning, thresholds dropped to approximately 1/3 of their original value. In Experiment 2 we found that observers showed far less learning when the noise components were not present. Experiment 3 found, unlike many other studies, almost complete transfer of learning across orientation. The results of Experiments 2 and 3 suggest that, unlike many other perceptual learning studies, most learning in Experiment 1 occurs at mid to high levels of processing rather than within low level analyzers tuned for spatial frequency and orientation. Experiment 4 found that performance was more severely impaired by spatial frequency shifts in noise components of the same spatial frequency or orientation as the signal components (though there was significant variability between observers). This suggests that after training observers based their responses on mechanisms tuned for selective regions of Fourier space. Experiment 5 examined transfer of learning from a same-sign task (the two signal components both increased/decreased in spatial frequency) to an opposite-sign task (signal components shifted in opposite directions in frequency space). Transfer of learning from same-sign to opposite-sign tasks and vice versa was complete suggesting that observers combined information from the two signal components independently.

Adult↗
PubMed1999

Modeling the combination of motion, stereo, and vergence angle cues to visual depth.

Three models of visual cue combination were simulated: a weak fusion model, a modified weak model, and a strong model. Their relative strengths and weaknesses are evaluated on the basis of their performances on the tasks of judging the depth and shape of an ellipse. The models differ in the amount of interaction that they permit among the cues of stereo, motion, and vergence angle. Results suggest that the constrained nonlinear interaction of the modified weak model allows better performance than either the linear interaction of the weak model or the unconstrained nonlinear interaction of the strong model. Further examination of the modified weak model revealed that its weighting of motion and stereo cues was dependent on the task, the viewing distance, and, to a lesser degree, the noise model. Although the dependencies were sensible from a computational viewpoint, they were sometimes inconsistent with psychophysical experimental data. In a second set of experiments, the modified weak model was given contradictory motion and stereo information. One cue was informative in the sense that it indicated an ellipse, while the other cue indicated a flat surface. The modified weak model rapidly reweighted its use of stereo and motion cues as a function of each cue's informativeness. Overall, the simulation results suggest that relative to the weak and strong models, the modified weak fusion model is a good candidate model of the combination of motion, stereo, and vergence angle cues, although the results also highlight areas in which this model needs modification or further elaboration.

Computer Simulation↗
PubMed1999

Experience-dependent integration of texture and motion cues to depth.

Previous investigators have shown that observers' visual cue combination strategies are remarkably flexible in the sense that these strategies adapt on the basis of the estimated reliabilities of the visual cues. However, these researchers have not addressed how observers' acquire these estimated reliabilities. This article studies observers' abilities to learn cue combination strategies. Subjects made depth judgments about simulated cylinders whose shapes were indicated by motion and texture cues. Because the two cues could indicate different shapes, it was possible to design tasks in which one cue provided useful information for making depth judgments, whereas the other cue was irrelevant. The results of experiment 1 suggest that observers' cue combination strategies are adaptable as a function of training; subjects adjusted their cue combination rules to use a cue more heavily when the cue was informative on a task versus when the cue was irrelevant. Experiment 2 demonstrated that experience-dependent adaptation of cue combination rules is context-sensitive. On trials with presentations of short cylinders, one cue was informative, whereas on trials with presentations of tall cylinders, the other cue was informative. The results suggest that observers can learn multiple cue combination rules, and can learn to apply each rule in the appropriate context. Experiment 3 demonstrated a possible limitation on the context-sensitivity of adaptation of cue combination rules. One cue was informative on trials with presentations of cylinders at a left oblique orientation, whereas the other cue was informative on trials with presentations of cylinders at a right oblique orientation. The results indicate that observers did not learn to use different cue combination rules in different contexts under these circumstances. These results are consistent with the hypothesis that observers' visual systems are biased to learn to perceive in the same way views of bilaterally symmetric objects that differ solely by a symmetry transformation. Taken in conjunction with the results of Experiment 2, this means that the visual learning mechanism underlying cue combination adaptation is biased such that some sets of statistics are more easily learned than others.

Cues↗
PubMed1997

Antepartum fetal pulse oximetry.

OBJECTIVE: To examine the feasibility of antepartum fetal pulse oximetry by using a specially designed probe. STUDY DESIGN: Twenty multiparous patients at term planned for induction of labor. The probe was passed through the cervix and held against the fetal scalp. Two laser diodes provided light in the near-infrared spectral region. Only reflected signals of both wavelengths which were consistent in pulse frequency and phase and with an AC/DC ratio of > 0.02% were considered usable. RESULTS: Usable measurements were obtained in 16 out of 20 cases. Overall usable signal time was 45% (range 30.2-61.5%). There was no accidental rupture of membranes. Mean fetal oxygen saturation was 76.1 +/- 6.2%. CONCLUSIONS: This study has shown that antepartum fetal pulse oximetry is feasible once a specially designed probe and signal analysis system are used.

Female↗
PubMed1993

Multiple-scattering effects in transmission oximetry.

To develop an algorithm for the spectrophotometric determination of the oxygen saturation in blood, a model for the transmission of light in a scattering and absorbing medium is developed, taking into account effects of multiple scattering. The computed results obtained by a Monte Carlo simulating program agreed well with those found by experiment. The results were compared with those obtained by the commonly used algorithm of transmission oximetry (based on Lambert-Beer's law) and it was found that the calibration curves obtained by this method were strongly dependent on the haematocrit and thickness of the sample. These curves were less reliable the lower the saturation of oxygen.

Algorithms↗
PubMed1993

Errors in direction-of-motion discrimination with dichoptically viewed stimuli.

At durations shorter than about 150 msec, a complex grating comprising a static 1-c/deg grating and a moving 3-c/deg grating is perceived as moving in the direction opposite that of the physical direction of motion. Here the phenomenon is further examined by measuring the perceived direction of motion of the fused images of a 1-c/deg grating presented to one eye and a moving 3-c/deg grating presented to the other. The strength of the illusion is almost unaffected by dichoptic presentation. This observation is consistent with the hypothesis that perceived motion is a consequence of the way the visual system integrates signals arising from different detectors tuned to the two component gratings.

Humans↗
PubMed1985

Optical properties of the sclera.

A relationship between the structure of the sclera and its light scattering properties is proposed. The relative optical density as a function of wavelength in the infrared was measured for three sclera and a good correlation with the predicted function was found. The angular distribution of the scattered light at 632.8 nm as well as the degree of polarisation of the scattered light at zero angle was measured for three sclera; from these results the total transmission of the sclera was determined.

Collagen↗