An adaptive filter for steady-state evoked responses

Tang, Yu; Norcia, Anthony M.

doi:10.1016/0168-5597(94)00309-3

Cited by 106 publications

(70 citation statements)

References 9 publications

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“…Electrode impedance was equal to or less than 5 k⍀. Data acquisition and stimulus presentation were controlled using an in-house software system (37,41).…”

Section: Methodsmentioning

confidence: 99%

“…For each bin, a recursive, least-squares algorithm (41) was used to generate a series of complex-valued spectral coefficients representing the amplitude and phase of response components tuned to various multiples (harmonics) of the stimulus frequency. These spectral coefficients for each bin were averaged together across trials for each subject, channel, harmonic, and stimulus condition.…”

Section: Methodsmentioning

confidence: 99%

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Visual Development in Very Low Birth Weight Infants

et al. 2006

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ABSTRACT:Extremely preterm infants are at risk for neurodevelopmental problems and the visual system is particularly vulnerable. However, development of visual function in preterm infants with little or no retinal or neurologic injury has not been well defined. This study compared development of visual function in preterm infants without severe retinopathy of prematurity (ROP), intraventricular hemorrhage (IVH) or periventricular leukomalacia (PVL) to that of term infants at 5-7 mo corrected age. Twenty-one very low birth weight (VLBW) preterm infants (24 -32 wk gestational age, weighing Ͻ 1500 g), and 22 healthy term infants were tested at 5-7 mo corrected age. Infants with any IVH/PVL and Ͼ Stage II ROP or Plus disease were excluded. Contrast sensitivity, grating acuity, and vernier acuity were measured using swept-parameter visual evoked potentials. Thresholds and maximum amplitudes were compared between groups. VLBW and term infants showed no differences in sensitivity for contrast (67.5 versus 63.8), grating resolution (12.4 versus 12.5 cpd) or vernier acuity (1.2 versus 1.0 arcmin). However, the amplitudes for swept contrast (p Ͻ 0.03) and swept vernier offset (p Ͻ 0.04) stimuli were higher in VLBW infants. Visual thresholds in VLBW infants without serious retinal or neurologic abnormalities were not significantly different from those of term infants, suggesting that increased visual experience does not influence visual sensitivity. The higher amplitudes in VLBW infants, suggests that visual experience may affect responses to suprathreshold stimuli.

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“…Electrode impedance was equal to or less than 5 k⍀. Data acquisition and stimulus presentation were controlled using an in-house software system (37,41).…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Visual Development in Very Low Birth Weight Infants

et al. 2006

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“…A recursive least square (RLS) adaptive filter (Tang and Norcia, 1995) was used to determine VEP amplitude and phase for the second-order terms (2f 1 , 2f 2 , f 1 ϩ f 2 and f 1 Ϫ f 2 ) and the fourth-order terms (4f 1 , 4f 2 , 2f 1 ϩ2 f 2 and 2 f 1 Ϫ2 f 2 ), where f 1 was 4.52 Hz and f 2 was 2.58 Hz. The target and flanker temporal frequencies were integer submultiples of the vertical frame rate (16 and 28) and were nearly incommensurate.…”

Section: Methodsmentioning

confidence: 99%

Development of the Spatial Organization and Dynamics of Lateral Interactions in the Human Visual System

et al. 2003

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Psychophysical thresholds and neuronal responses for isolated stimuli are strongly modified by nearby stimuli in the visual field. We studied the orientation and position specificity of these contextual interactions using a dual-frequency visual-evoked potential technique in developing human infants and adults. One set of small, oriented stimulus elements (targets) was tagged with a temporal frequency f 1 of 4.52 Hz. The addition of an abutting second set of similar patches (flankers) tagged at f 2 ϭ 2.58 Hz had three effects: (1) The flankers reduced the second and fourth harmonic responses to the targets. This reduction was independent of flanker orientation or position and age. (2) The response to the combination of targets and flankers also contained nonlinear interaction terms (1f 1 Ϯ 1f 2 ) that were tuned for flanker orientation and position in adults, but only for flanker orientation in infants 8 -31 weeks of age. (3) Nonlinear interaction terms recorded at 2f 1 Ϯ 2f 2 were large and untuned for flanker orientation and position in adults but were nearly absent in the youngest infants. The three forms of nonlinear interaction, thus, have differences in sensitivity to flanker orientation and position and differential growth trends, indicating that they are generated by different mechanisms. These three forms of interaction could serve different functional roles. The first process provides a nonselective gain control that is fully functional in early infancy. The second process, which develops slowly, is selective for the specific form of the stimuli. The third process, which is also immature, pools across orientation.

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“…The sampled data was adaptively filtered in real-time on the MacDSP card using the method described in Tang & Norcia (1995). A Recursive Least Squares (RLS) adaptation algorithm was used in a modification of the Adaptive Noise Cancellation technique of Widrow et al (1975).…”

Section: Vep Data Acquisition and Response Analysismentioning

confidence: 99%

The Jitter Spatial Frequency Sweep VEP: A new paradigm to study spatiotemporal development of pattern- and motion-processing mechanisms in human infants.

Hamer¹,

Norcia²

2009

Psychology & Neuroscience

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We introduce a new VEP paradigm -the Jitter Spatial Frequency (JSF) Sweep VEP -that permits efficient mapping of the spatiotemporal tuning of the developmental motion asymmetry (DMA). Vertical sinewave gratings undergoing 90 o horizontal oscillatory displacements (6 or 10 Hz) were presented while their SF was swept over 2 to 5 octaves during each VEP trial. JSF sweep VEPs were recorded from 28 infants (8-43 weeks), and symmetric (second-harmonic, F2) and asymmetric (F1) components of the VEP were measured. JSF sweeps can provide four useful estimates: (1,2) the high-SF cutoff of F1 and F2 responses estimates the spatial resolution of direction-selective (DS) and non-DS mechanisms, respectively; (3) the low-SF cutoff for F1 estimate the SF-boundary between mature (F1 absent) and immature (F1 present) DS mechanisms; and (4) the F1 high-SF cutoff estimates the lower velocity limit of cortical DS cells. For 6 Hz, the low-SF F1 cutoffs increased two times faster than traditional (contrast-reversal) VEP grating acuity (0.5 vs ~0.25 octaves/month), and twice that of the high-SF F1 and F2 cutoffs. This implies that no single mechanism can account for the DMA at both low and high SFs. At 10 Hz, the DMA exhibited no significant development, consistent with slower maturation of DS mechanisms at higher ST frequencies. The F2 high-SF cutoffs were higher than F1 at both 6 and 10 Hz, suggesting higher spatial resolution for non-DS (pattern) vs DS (motion) mechanisms. Finally, the lower velocity limit of the DS mechanisms decreased from ~2 deg/sec at 8 weeks, to 0.75 deg/sec at 33 weeks, similar to analogous limits for direction-of-motion identification in adults (~0.5 -1 deg/sec), and close to prior VEP estimates in infants (0.6 deg/sec).

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An adaptive filter for steady-state evoked responses

Cited by 106 publications

References 9 publications

Visual Development in Very Low Birth Weight Infants

Visual Development in Very Low Birth Weight Infants

Development of the Spatial Organization and Dynamics of Lateral Interactions in the Human Visual System

The Jitter Spatial Frequency Sweep VEP: A new paradigm to study spatiotemporal development of pattern- and motion-processing mechanisms in human infants.

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