Biomedical subjects

Henry P Brent

Publications and source records attributed to Henry P Brent.

5 recordsLinked to original sources

PubMed2004

Impairment in holistic face processing following early visual deprivation.

Unlike most objects, faces are processed holistically: They are processed as a whole rather than as a collection of independent features. We examined the role of early visual experience in the development of this type of processing of faces by using the composite-face task, a measure of holistic processing, to test patients deprived of visual experience during infancy. Visually normal control subjects showed the expected composite-face effect: They had difficulty perceiving that the top halves of two faces were the same when the top halves were aligned with different bottom halves. Performance improved when holistic processing was disrupted by misaligning the top and bottom halves. Deprived patients, in contrast, showed no evidence of holistic processing, and in fact performed significantly better than control subjects when top and bottom halves were aligned. These findings suggest that early visual experience is necessary to set up or maintain the neural substrate that leads to holistic processing of faces.

Adolescent↗

PubMed2003

Expert face processing requires visual input to the right hemisphere during infancy.

Adult expertise in face processing is mediated largely by neural networks in the right hemisphere. Here we evaluate the contribution of early visual input in establishing this neural substrate. We compared visually normal individuals to patients for whom visual input had been restricted mainly to one hemisphere during infancy. We show that early deprivation of visual input to the right hemisphere severely impairs the development of expert face processing, whereas deprivation restricted mainly to the left hemisphere does not. Our results indicate that the neural circuitry responsible for adults' face expertise is not pre-specified, but requires early visual experience. However, the two hemispheres are not equipotent: only the right hemisphere is capable of using the early input to develop expertise at face processing.

Adolescent↗

PubMed2003

Contact lenses for the treatment of pediatric cataracts.

OBJECTIVE: To evaluate the experiences, attitudes, and perceptions of the caregivers of children with cataracts who were visually rehabilitated with contact lenses. PARTICIPANTS: One hundred twenty-three caregivers of children <8.1 years old treated for unilateral and bilateral cataracts at one pediatric hospital. DESIGN: Survey by questionnaire. INTERVENTION: Primary caregivers were asked to complete an anonymous questionnaire. MAIN OUTCOME MEASURES: Caregiver responses to questions assessing background and demographic and clinical information, as well as perceptions, attitudes, levels of compliance, and anxiety with respect to treatment, were reviewed. Caregivers were also asked to choose between aphakic rehabilitation with contact lenses, aphakic glasses, or intraocular lenses, given various hypothetical scenarios differing in regard to their final visual prognosis, risks of treatment complications, and cost. RESULTS: The response rate was 82.9%. Absolute average stress levels for contact lens use were 1.36 +/- 1.79 and 0.79 +/- 1.48 (scale, 0-5) for insertion and removal, respectively, compared with 4.03 +/- 1.64 and 2.40 +/- 1.92 for cataract surgery and patching therapy, respectively. Although average paired initial resistance to treatment (RT) levels for contact lens insertion and removal on a scale of 0 to 3 were high (2.09 +/- 1.15) and moderate (1.63 +/- 1.20), respectively, final RT levels were significantly lower (1.09 +/- 1.14 and 0.66 +/- 1.07, respectively; P < 0.0001). The vast majority of caregivers chose contact lens use in hypothetical scenarios that depicted realistic expectations for other forms of aphakic rehabilitation. CONCLUSIONS: In our study, contact lenses seemed to be well tolerated by most patients, as assessed by caregivers. Although initial resistance to contact lens use is high, this decreases with time. Relative to other events in the treatment of pediatric cataracts, contact lens use is not a major stressor for most caregivers and patients. This study supports the notion that contact lenses should continue to receive serious consideration as a treatment option for pediatric cataracts.

Aphakia, Postcataract↗

PubMed2002

Better perception of global motion after monocular than after binocular deprivation.

We used random-dot kinematograms to compare the effects of early monocular versus early binocular deprivation on the development of the perception of the direction of global motion. Patients had been visually deprived by a cataract in one or both eyes from birth or later after a history of normal visual experience. The discrimination of direction of global motion was significantly impaired after early visual deprivation. Surprisingly, impairments were significantly worse after early binocular deprivation than after early monocular deprivation, and the sensitive period was very short. The unexpectedly good results after monocular deprivation suggest that the higher centers involved in the integration of global motion profit from input to the nondeprived eye. These findings suggest that beyond the primary visual cortex, competitive interactions between the eyes can give way to collaborative interactions that enable a relative sparing of some visual functions after monocular deprivation.

Adolescent↗

PubMed2002

Sensitivity to global form in glass patterns after early visual deprivation in humans.

To compare the effects of early monocular versus early binocular deprivation on the perception of global form, we assessed sensitivity to global concentric structure in Glass patterns with varying ratios of paired signal dots to noise dots. Children who had been deprived by dense congenital cataracts in one (n=10) or both (n=8) eyes performed significantly worse than comparably aged children without eye problems. Consistent with previous results on sensitivity to global motion [Vision Research 42 (2002) 169], thresholds in the deprived eyes were significantly better after monocular deprivation than after binocular deprivation of comparable duration, even when there had been little patching of the nondeprived eye after monocular deprivation. Together, the results indicate that the competitive interactions between a deprived and nondeprived eye evident in the primary visual cortex can co-occur with complementary interactions in extrastriate cortex that enable a relative sparing of some visual functions after early monocular deprivation.

Adolescent↗