Biomedical subjects

K C Lindfield

Publications and source records attributed to K C Lindfield.

6 recordsLinked to original sources

PubMed2000

Semantic capacities of the right hemisphere as seen in two cases of pure word blindness.

Two patients with pure alexia were studied with tachistoscopically presented stimuli to examine factors influencing their ability to distinguish words from nonwords and to derive semantic information at exposures too brief for explicit letter identification. Both patients had profound right hemianopia and computerized tomography (CT) evidence of splenial destruction. Both patients were successful in making word/nonword decisions for high-frequency, but not low-frequency, words. They could judge semantic class membership reliably for such common categories as animals and vegetables, but not for arbitrarily selected categories, such as office-related items. Judgments about the gender of people's names and place versus person name distinctions were made with high reliability. Results are interpreted as evidence for limited word recognition and semantic-processing capacity in the right hemisphere.

Aged↗

PubMed2000

Effects of age and hearing sensitivity on the use of prosodic information in spoken word recognition.

It is well known that spoken words can often be recognized from just their onsets and that older adults require a greater word onset duration for recognition than young adults. In this study, young and older adults heard either just word onsets, word onsets followed by white noise indicating the full duration of the target word, or word onsets followed by a low-pass-filtered signal that indicated the number of syllables and syllabic stress (word prosody) in the absence of segmental information. Older adults required longer stimulus durations for word recognition under all conditions, with age differences in hearing sensitivity contributing significantly to this age difference. Within this difference, however, word recognition was facilitated by knowledge of word prosody to the same degree for young and older adults. These findings suggest, first, that listeners can detect and utilize word stress in making perceptual judgments and, second, that this ability remains spared in normal aging.

Adolescent↗

PubMed1998

Adult age differences in the temporal characteristics of category free recall.

Two experiments are reported that examined the temporal structure of recall for categorizable word lists by younger and older adults. All participants showed response bursting, in which recall order is clustered by semantic category, with longer interresponse times (IRTs) appearing between categories than within categories. Experiment 1 demonstrated that older adults, even when matched to younger adults in overall accuracy, differed in the rate of increase of between-category IRTs with output position, but not in within-category IRTs. Experiment 2 showed that this interaction is eliminated when the names of the response categories are provided to the participants. Results are interpreted in terms of combined effects of an age-compromised episodic memory system (between-category IRTs) accompanied by a comparatively preserved semantic system (within-category IRTs) in healthy aging.

Adolescent↗

PubMedDate not supplied

The role of prosody in the mental lexicon.

Current models of spoken word recognition take into account factors such as word frequency, word onset cohort size, and phonological neighborhood density. Using the word onset gating technique we tested word recognition when bandpass filtering was used to allow subjects to hear the full prosodic pattern of a word (number of syllables and syllabic stress), deprived of segmental information beyond that contained in the onset gate. Subjects also heard either word onsets plus duration information or only word onsets. Results suggest that word prosody is represented in the mental lexicon and is effectively used by listeners in spoken word recognition.

Cognition↗

PubMedDate not supplied

Multiple memory systems in the processing of speech: evidence from aging.

Young and old adults gave verbatim recall of recorded prose passages that varied in average word predictability and rate of presentation. Subjects were allowed to interrupt the speech passages at points of their choosing for recall of what they had heard on a segment-by-segment basis. For both age groups, the sizes of the segments selected were affected by level of predictability but not by the speech rate of the spoken passages. Subjects tended to interrupt the passages for recall at linguistic constituent boundaries. Recall of the segments was poorer for the elderly adults than for the young adults, with larger age differences for faster speech rates and for passages that were lower in average word predictability. Results are discussed in terms of the recent suggestion that multiple memory representations of a speech message may co-occur briefly in time.

Adolescent↗

PubMedDate not supplied

An experimental and computational analysis of age differences in the recognition of fragmented pictures: inhibitory connections versus speed of processing.

Young and older adults were tested for the ability to identify degraded pictures presented either in a series of incremental steps with each step increasing the completeness of the visual information (ascending condition) or in one single exposure (fixed condition). Significant interference effects, indicated by a superiority of fixed over ascending presentations, appeared at a lower level of performance for the older adults than for the young adults. This finding was consistent with the notion of an inhibition deficit operating in normal aging. A computer simulation, based on simple connectionist architecture, demonstrated that an age-related inhibition deficit in the identification of fragmented pictures can be produced by slowed processing rates.

Adolescent↗