Biomedical subjects

D H Shum

Publications and source records attributed to D H Shum.

5 recordsLinked to original sources

PubMed2000

Effects of severe traumatic brain injury on visual memory.

The study aimed to clarify the effects of severe traumatic brain injury (TBI) on visual memory. Three groups of participants (14 late-recovery and 14 early-recovery TBI individuals and 18 controls) were administered the following: The Shum Visual Learning Test (SVLT), a test that measures the ability to remember visual patterns, an electronic maze test, a test that measures the ability to remember spatial positions, and the Rey Auditory Verbal Learning Test (RAVLT), a test of verbal memory and learning. The individuals with TBI (late- and early-recovery) were found to be impaired on the SVLT and the RAVLT but not on the electronic maze. Specifically, on the SVLT, they were found to learn at a slower rate and make more false-positive errors than the controls. The advantages of the SVLT over visual memory tests used in previous studies and the significance of findings of the present study were discussed.

Adolescent↗

PubMed1999

Normative data for a new memory test: the Shum Visual Learning Test.

This study reports normative data and test-retest reliabilities for a visuo-spatial memory test, the Shum Visual Learning Test (SVLT). Participants were 146 Caucasians (70 males and 76 females, age range between 17-83 years). The test was administered to 116 participants once and 30 participants twice (1 month apart). Age (but not gender and education) was found to affect SVLT test performance. The norms, therefore, were presented according to seven age groups (viz., 17-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70+ years). Three indices (learning, retention after interference, and delayed retention) were derived for descriptive and clinical purposes. The test-retest reliabilities for all trials of the SVLT (except Trial 6) were found to be significant (rs ranged from .63 to .82). Normative data reported allow neuropsychologists to compare patient performances with those of appropriate controls and are important for fostering clinical application of this test.

Adolescent↗

PubMed1994

Assessment of attention: relationship between psychological testing and information processing approaches.

Examined the relationship between the psychological testing and information processing approaches in assessing attention. Eighty-seven subjects (57 females, 30 males) undertook eight psychological tests of attention and a visual-spatial reaction-time task. Using the cognitive-correlate method (Posner & McLeod, 1982), it was found that three components of attention (viz., visual-motor scanning, sustained selective processing, and visual/auditory spanning) derived from the psychological tests could be significantly predicted by specific, yet different, combinations of six indices of information processing (mean reaction time (RT), mean movement time (MT), feature extraction, identification, response selection, and motor adjustment): (a) mean RT and mean MT were found to be the most important indices for predicting performance on visual-motor scanning; (b) the motor-adjustment stage was found to be the most important index for predicting performance on sustained selective processing; (c) the response-selection stage was found to be the most important index for predicting performance on visual/auditory spanning. These relationships are important for supporting the construct-related validity of the psychological tests of attention and for extending the generality and applicability of the RT task.

Adolescent↗

PubMed1994

Effects of closed-head injury on attentional processes: generality of Sternberg's additive factor method.

The present study examined the generality of Shum, McFarland, Bain, and Humphreys' (1990) findings that closed-head injury (CHI) selectively impairs different processes of attention (operationalized in terms of stages of information processing) depending on the severity of, and the time since, injury. The procedure of Shum et al. was based on Sternberg's additive factor method (AFM), with the mode of information processing involved being a physical-directional matching of visual stimuli. The present study followed a similar procedure except that a name-matching task was used. This task was administered to 16 first-year psychology students and two groups of CHI patients (viz., severe short-term (SS) and severe long-term (SL)) with matched control groups. The results obtained replicated the study by Shum in that the SS group was found to be impaired on the identification and response-selection stages of information processing whereas the SL group was found to be impaired only on the response-selection stage. The present study confirms that the AFM is not limited to one specific mode of information process and strengthens the validity of the conclusions made by Shum et al. regarding the effects of CHI on attention.

Adolescent↗

PubMed1990

Effects of closed-head injury on attentional processes: an information-processing stage analysis.

The present study, based on Sternberg's (1969) additive-factor method, examined attentional processes in terms of four information-processing stages (feature extraction, identification, response selection, and motor adjustment). Four task variables were used to operationally define the stages (signal quality, signal similarity, signal-response compatibility, and foreperiod uncertainty). In two studies, a visuo-spatial reaction-time task was undertaken by a group of university subjects (Experiment 1) and by three groups of closed-head-injured patients (severe short-term, severe long-term, and mild short-term) and their corresponding matched controls (Experiment 2). The results indicated that both patients and normals exhibited a similar mode of linear information processing. In addition, it was found that the severe short-term group was impaired on the response-selection stage and response selection stage; the severe long-term group was impaired only on the response-selection; and no evidence of impairment was found for the mild short-term patients. The implications of these findings with reference to the study of attentional processes in closed-head injured patients and to neuropsychological assessment and rehabilitation are discussed.

Adolescent↗