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PubMed1992

Influence of processing speed on adult age differences in working memory.

Two studies are reported in which adults ranging from 18 to 80 years of age performed tasks designed to measure working memory functioning and perceptual comparison speed. The results from both studies indicated that statistical control of the measures of perceptual comparison speed greatly attenuated the age-related variance in measures of working memory even when working memory was assessed under self-paced conditions. Additional results in the second study supported the hypothesis that the speed influence was manifested in the rate of activating information rather than in the rate at which it was lost as a function of time or other processing.

Adolescent↗
PubMed1997

Backward masking of words and faces: evidence for different processing speeds in the hemispheres?

Two tachistoscopic experiments with a lateralized presentation of function words and faces were carried out to investigate the influence of temporal factors and type of masking on visual field asymmetries. Accuracy, represented by signal detection measures (d' and beta), was calculated separately for the two visual fields, for various interstimulus intervals, and for noise and pattern masking. In both experiments, d' increased with prolonged temporal delay between target and mask. In the lexical decision task, visual field interacted with mask type confirming that only in the pattern mask condition did an advantage of the right visual field emerge. In the facial decision task, however, visual field interacted with interstimulus interval, confirming that, in the left visual field, the facial information escaped the masking effect earlier than in the right visual field. In the facial task, there was a higher response criterion (beta) in the left visual field. By applying different types of masks, visual processing of lexical stimuli can be disrupted at distinct stages where perceptual asymmetries are present to a varying extent. The results of both experiments suggest that words and faces are differentially affected by masking procedures.

Adult↗
PubMed1991

Effects of processing speed on cerebral asymmetry for left- and right-oriented faces.

A free-vision chimeric facial emotion judgment task and a tachistoscopic face-recognition reaction time task were administered to 20 male right-handed subjects. The tachistoscopic task involved judgments of whether a poser in the centrally presented full-face photograph was the same or different poser than in a profile photograph presented in the left or right visual field (LVF, RVF). The free-vision task was that used by J. Levy, W. Heller, M. Banich, and L. Burton (1983, Brain and Cognition, 2, 404-419) and involved judging which of two chimeric faces appeared happier, in which the two chimeras were mirror images of each other and each chimera consisted of a smiling half-face joined at the midline to a neutral half-face of the same poser. For the tachistoscopic task, subjects were divided into groups of Fast and Slow responders by a median split of the mean reaction times. For the Fast subjects, judgments were faster in the LVF than in the RVF, and there was a significant interaction between visual field and profile direction, such that responses were faster for medially oriented profiles; i.e., LVF responses were faster for right-facing than for left-facing profiles, with the reverse relationship in the RVF. The Slow responders did not show these effects. Only the Fast group showed the bias for choosing the chimera with the smile on the left as happier, and mean response speed and the LVF advantage on the tachistoscopic test correlated with the leftward bias on the free-vision task for all subjects combined. It was suggested that overall response speed on the face-matching task reflected the extent to which specialized and more efficient right hemisphere functions were activated.

Adult↗
PubMed1994

Processing speed in the cerebral cortex and the neurophysiology of visual masking.

In experiments to investigate the duration of the time for which cortical neurons respond when the identification of a visual stimulus is just possible, we presented a test face stimulus for 16 ms, and followed it at different intervals by a masking stimulus (either an N-O pattern or a face) while recording from single neurons in the temporal visual cortex of macaques. When there was no mask the cells responded to the 16 ms of the test stimulus for 200-300 ms, far longer than the presentation time. We suggest that this reflects the operation of a short-term memory system implemented in cortical circuitry. If the mask was a stimulus which did not stimulate the cells (either a non-face pattern or a face which was a non-effective stimulus for that cell), then, as the interval between the onset of the test stimulus and the onset of the mask stimulus (the stimulus onset asynchrony) was reduced, the length of time for which the cells fired in response to the test stimulus was reduced. It is suggested that this is due to the mask stimulating adjacent cells in the cortex which by lateral inhibition reduce the responses of the cells activated by the test stimulus. When the stimulus onset asynchrony was 20 ms, face-selective neurons in the inferior temporal cortex of macaques responded for a period of 20-30 ms before their firing was interrupted by the mask. With the same test-mask stimulus onset asynchrony of 20 ms, humans could just identify which of six faces was shown.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Effects of training in monitoring accuracy on processing speed in mental retardation.

Monitoring accuracy during choice RT allows subjects to maintain fast, safe RT bands and avoid overly fast, unsafe RT bands. 5 retarded adults received trial-by-trial feedback on accuracy over a number of sessions to train monitoring of accuracy and to improve RT performance. Training was introduced according to a multiple-baseline-across-subjects (with reversal) design. Training had no significant effect on subsequent RT performance, suggesting that inefficient monitoring of accuracy may be a structural characteristic of mental retardation.

Adult↗
PubMed1998

Real-time reconstruction and high-speed processing in functional MR imaging.

Access to fully processed activation maps in near real time during a functional MR examination enables run-to-run assessment of results. This is particularly useful in clinical studies, since the results of the functional MR examination can be ascertained before the patient leaves the MR suite, permitting interactive tailoring of the functional MR study. We describe how a real-time MR system can be customized to complete the following tasks in less than 3 minutes: obtain an 81-second acquisition of a multisection functional MR imaging time series using single-shot echo-planar imaging, perform image reconstruction, extract functional MR activation maps using cross-correlation and thresholding, and superimpose activation maps on previously acquired T1-weighted anatomic images.

Algorithms↗
PubMed1997

Developmental changes in speed of information processing in young children.

This study investigated developmental increases in processing speed in young children, relative to adults, with only nonverbal stimuli. R. Kail's (1991) model of the rate of change in processing speed from childhood to adulthood was evaluated. Processing speed was measured in 34 children at 4 years, 37 at 5 years, and 38 at 6 years and in 43 adults, with a battery of 8 computer-administered tests. Results showed clear age-related increases in processing speed that cannot be attributed to increased accuracy and error rate monitoring. Kail's model adequately accounted for the observed rate of developmental change in processing speed; however, the parameter estimates of R. Kail and Y. Park (1992) provided more accurate predictions than did the meta-analytically derived estimates of Kail (1991). Findings support the global developmental trend hypothesis and suggest that this trend extends beyond the range of verbal skills evaluated in previous research.

Adult↗
PubMed1996

Cognitive factors in auditory performance: context, speed of processing, and constraints of memory.

This paper describes several techniques used to explore the role of cognitive factors in auditory performance in elderly adults. Two factors, cognitive slowing and age-related memory constraints, receive special attention. Assessing listeners' ability to report the content of time-compressed speech shows elderly adults to be especially vulnerable to rapid speech input. Such effects, however, are ameliorated by effective use of linguistic knowledge, which, unlike processing speed, remains relatively stable in adult aging. A second technique is described in which intelligibility is tested for words excerpted from fluent speech, first presented in isolation and then with varying amounts of preceding or following context from the original utterances. Memory constraints are shown to have a significant effect on elderly listeners' ability to use linguistic context that follows an acoustically ambiguous region for a retrospective analysis of what had been heard. Thus, cognitive factors can both enhance and limit auditory performance in elderly listeners.

Adolescent↗
PubMed1985

A cross-sequential analysis of developmental differences in speed of visual information processing.

Development of processing speed was examined in three backward masking studies. The first verified the central nature of backward masking for children aged 8 and 11 years and for adults. The second suggested that task requirements were equivalent for children similar to those in Study 1, and that age differences in performance were not attributable to nonprocessing variables. The main cross-sequential study estimated speed of processing in 80 children (approximately 6 years to 13 years) and young adults using an inspection time task. Target exposure duration was varied to establish the time required to achieve a high level of discriminative accuracy. Estimates of processing speed increased until about 11-13 years of age; beyond this, the trend was less obvious, and it is possible that inspection time asymptotes at around the onset of adolescence. Performance improvement after 1 year could not be explained as resulting from practice since improvement among controls over a period of 2 weeks was significantly less. Correlations between estimates of inspection time made up to 2 years apart found the measure to be reliable.

Adolescent↗