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M L Kietzman

Publications and source records attributed to M L Kietzman.

13 recordsLinked to original sources
PubMed1987

Two-pulse temporal integration functions in the fovea and peripheral retina.

The temporal integration of luminous energy was compared in the fovea and at 7 degrees eccentricity using two-pulse stimuli and two methodologies. The two-pulse stimuli consisted of two 1-msec. light pulses separated by intervals of darkness ranging from 1 to 400 msec.; they were provided by a glow modulator tube transilluminating a 21.8' opal glass target. In Exp. 1 (equal-performance design), integration functions were generated using a forced-choice staircase procedure to estimate threshold luminance. The data for two Os showed that the critical duration (CD), and thus the period of complete integration, was briefer in the fovea than at 7 degrees. Beyond the CD, integration continued to differ for the two retinal locations. In the fovea, two-pulse stimuli beyond CD evidenced partial integration and at the longest stimulus durations no integration or inhibition. In contrast, at 7 degrees stimuli beyond CD appeared to evidence probability summation. In Exp. 2 (equal-energy design), integration functions were generated by measuring the detectability of two-pulse stimuli of different durations but equal in total luminous energy. A signal-detection procedure yielded measures of both response frequency and signal detectability, P(A). The data for two Os showed that for both measures CD was briefer in the fovea than at 7 degrees. Also, in the fovea, long two-pulse stimuli appeared to show no integration or inhibition. Both experiments then showed a foveal-peripheral difference in two-pulse measures of visual temporal integration, with the fovea evidencing less integration. In addition, the forced-choice and signal-detection procedures showed that these loci differences in integration were independent of the Os' response criterion.

Adult↗
PubMed1986

Visual flicker in depression: response criteria, confidence ratings and response times.

Differences in response criterion and sensory sensitivity to visual flicker among major depressive patients, dysthymic patients, and normal controls were investigated. Also, signal detection confidence ratings and response times were compared. The results indicated that major depressive patients responded more conservatively (i.e. were less willing to respond 'flicker') than either of the other groups. The groups did not differ significantly on a criterion free measure of flicker sensitivity. The major conclusions are: previously reported visual flicker differences between depressed patients and normal controls were probably due to the more conservative response criterion of the patients and not to flicker sensitivity differences between groups; and confidence ratings and response times yield similar conclusions with respect to visual flicker sensitivity and response criterion. Therefore, interpretations concerning a sensory or perceptual deficit in depression must take into account the differences in response criterion between depressed patients and normal controls.

Adult↗
PubMed1984

The modality shift effect in schizophrenia: fact or artifact?

We investigated whether the disproportionate slowing of schizophrenic patients on cross-modal relative to ipsimodal sequences in a reaction time task ("modality shift effect") could be attributed to a psychometric artifact, as implied by Chapman and Chapman. Fifteen schizophrenic patients (Research Diagnostic Criteria) and 50 normal controls with no current or past history of psychiatric disorder were tested. Subjects made an identical finger-lift response to brief duration light and sound stimuli of different intensities presented in quasi-random order. The major finding was that psychometric artifact could not account for the disproportionate slowing of the reaction time of schizophrenic patients since the reliabilities and variances of the cross-modal and ipsimodal conditions did not differ in normal controls. Furthermore, the modality shift effect was highly significant for reaction times to both sound and light and for all intensities. Findings were the same when the schizophrenic patients were compared to a matched subgroup of slow-responding normal controls.

Cues↗
PubMed1982

Dichoptic backward masking of letters, words, and trigrams in old and young subjects.

Age differences in central visual processing were studied in 30 older adults (mean age 67.9 years) and in 30 young adults (mean age 19.8 years) using a dichoptic backward masking paradigm. Single letters, three-letter words, and consonant trigrams were used as target stimuli with a patterned masking stimulus. A significant age difference (p less than .001) was found in the interstimulus intervals necessary to escape the masking effect (ISIc) with older subjects requiring approximately 75 msec longer than the younger ones at each of three target durations. The effect of letters, words, and trigrams on ISIc for both young and old also yielded a significant difference (p = .01) with words most readily identified, letters intermediate, and trigrams requiring the longest processing time. Implications of these data with respect to previous studies and theoretical models are considered.

Adolescent↗