Biomedical subjects

J E Frick

Publications and source records attributed to J E Frick.

5 recordsLinked to original sources

PubMed1998

Long- and short-looking infants' recognition of symmetrical and asymmetrical forms.

Adults process symmetrical visual forms more rapidly than asymmetrical visual forms, presumably because symmetrical forms are amenable to a global visual encoding strategy. Individual differences in look duration during infancy have been hypothesized to covary with different modes of visual intake and encoding, with longer look durations reflecting encoding based on prolonged inspection of local visual properties, and briefer look durations reflecting encoding based on more of a global, or global-to-local processing sequence. This hypothesis predicts that short-looking infants would process symmetrical stimuli faster than asymmetrical stimuli, but that long-looking infants would not. Three experiments are described here in which this prediction is tested. Results were in general accord with the prediction, and provide further support for the hypothesis that individual differences in look duration may reflect different modes of visual encoding or inspection.

Analysis of Variance↗

PubMed1997

Sensitization during visual habituation sequences: procedural effects and individual differences.

Although individual differences in visual habituation have long been interpreted in terms of processes derived from comparator theory, research over the last decade has suggested that arousal or arousability as manifest in sensitization may contribute to infants' attentional profiles, and thus, to individual differences in those profiles. We explored this possibility by habituating 4-month-old infants to 4 x 4, 10 x 10, or 20 x 20 checkerboards in a fixed-trial paradigm. The first specific aim was to examine the attentional characteristics of infants with habituation patterns showing sensitization versus those that did not. The second specific aim was to determine whether patterns of attention suggestive of sensitization effects reported in past research might be attributable to the use of illuminated interstimulus intervals (ISIs). Trends were observed for sensitization to occur more frequently with more complex than with less complex checkerboards. Infants who showed looking patterns characteristic of sensitization looked longer and did not habituate as readily as infants who did not show sensitization. Finally, different ISIs did not engender different levels of sensitization, but dark ISIs significantly increased infants' looking times to stimuli during trials.

Arousal↗

PubMed1997

Primordial germ cells and oocytes of Branchiostoma virginiae (Cephalochordata, Acrania) are flagellated epithelial cells: relationship between epithelial and primary egg polarity.

Primordial germ cells (PGCs) are described from the gonad of c. 2 cm juvenile Branchiostoma virginiae; early oocytes (c. 10 microm) and enlarging, previtellogenic oocytes (c. 35 microm) are described from the ovary of c. 5 cm adults. The germinal epithelium of the juvenile gonad and adult ovary is composed of both germinal and somatic cells. In the juvenile, somatic cells retain contact with the basal lamina of the germinal epithelium though their perikarya may be displaced towards the lumen; the germinal epithelium is, therefore, a simple but pseudostratified epithelium. In the adult ovary, somatic cells may lose contact with the basal lamina and the epithelium appears to become stratified. PGCs and oocytes are identified as germ cells by the presence of nuage. PGCs and oocytes are polarised epithelial cells. They rest on a basal lamina, extend apically towards a lumen, form adhering junctions with neighbouring cells, and exhibit apical-basal polarity. PGCs and early oocytes have an apical flagellum with an associated basal body, accessory centriole, and one or more striated rootlet fibres. The flagellum is surrounded by a collar of microvilli. Once oocytes begin to enlarge and bulge basally into the connective tissue layer, the flagellum is lost, but the basal bodies and ciliary rootlets are present at the apex of 35 microm oocytes. Similarities of the oogenic pattern in cephalochordates and echinoderms indicate that the establishment of egg polarity in deuterostomes is influenced by the polarity of the germinal epithelium.

Animals↗

PubMed1996

Individual differences in infant visual attention: recognition of degraded visual forms by four-month-olds.

In 5 experiments, 4-month-old infants were tested for their ability to recognize degraded visual targets as a function of individual differences in fixation duration. Targets were degraded by removing 10% of the total contour either from vertices (vertex-absent) or from midsegments (vertex-present). Both qualitative and quantitative differences were found in long and short lookers' ability to recognize the degraded forms. Short-looking infants were able to recognize degraded forms in both vertex-absent and vertex-present conditions, but the vertex-absent discrimination was more difficult. Long-looking infants required longer familiarization times before showing evidence of recognition in the vertex-present condition, and were unable to recognize targets in which contour was removed at vertices. The findings are discussed within the framework of the persistence of early visual processing strategies, and reliance of long-looking infants on particular local elements in visual analysis.

Attention↗

PubMedDate not supplied

Individual and developmental differences in disengagement of fixation in early infancy.

The current study investigated whether individual and developmental differences in look duration are correlated with the latency for infants to disengage fixation from a visual stimulus. Ninety-four infants (52 3-month-olds, 42 4-month-olds) were tested in a procedure that measured ocular reaction time to shift fixation from a central target to a peripheral target under conditions in which the central-target either remained present ("competition" condition) or was removed from the display ("noncompetition" condition). Look duration was correlated with disengagement latency; longer-looking infants were slower than shorter-looking infants to shift fixation to the peripheral target on competition trials, but not noncompetition trials. Results were similar for 3- and 4-month-olds, although 3-month-olds showed slower latencies on all trials. Furthermore, long-looking infants were not consistently slower, but rather showed greater variability in their response latencies under conditions that required disengagement of fixation. The results support the position that developmental and individual differences in look duration are linked to the development of the neural attentional systems that control the ability to disengage, or inhibit, visual fixation.

Analysis of Variance↗