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Biomedical subjects

William Marks

Publications and source records attributed to William Marks.

9 recordsLinked to original sources
PubMed2006

The effects of training and transfer on global/local processing.

We investigated interference, inhibition and transfer effects associated with training on a global-local task. Participants received 10,080 training trials on identifying local features of global/local stimuli. Global processing advantage was eliminated with practice. Global interference decreased with training whereas local interference developed with training. Transfer analyses indicated that training produced stimulus-specific effects in local processing and task-specific effects in global processing. Our findings are discussed in regards to models of global/local processing.

Analysis of Variance↗
PubMed2006

Heightened false memory: a long-term sequela of severe closed head injury.

Declarative memory impairment is a common long-term sequela of severe closed head injury (CHI). Although veridical memory performance following severe CHI has received attention in the literature, little is known about false memory production in this population. Within the present study, both long-term survivors of severe CHI and matched control participants studied and were tested on six 12-items word lists from the Deese Roediger McDermott (DRM) paradigm. Word lists from the DRM are composed of words that are strongly semantically associated to a non-presented word (i.e., the critical lure). Prior studies have shown that healthy young adults show a high level of false recall and recognition memory for the critical lures, and it was hypothesized individuals with severe CHI would show heightened susceptibility to false memory compared to control participants due to difficulty with monitoring of memory. It was further hypothesized that severe CHI participants would show high confidence in their false memories. Consistent with hypotheses, results indicated that although severe CHI participants remembered fewer actual list items, they made more semantically related intrusion errors (recall) and false-positive responses (recognition) than the control participants. Severe CHI participants also showed greater confidence in their false memories than did control participants. The results are interpreted in the context of theoretical accounts of false memory, and possible structural and functional brain changes that might account for the Severe CHI group's memory performance are discussed.

Adolescent↗
PubMed2006

Donation after cardiac death has a minimal impact on thoracic organ recovery.

BACKGROUND: Our organ procurement organization recently developed an aggressive donation after cardiac death program. Thoracic organs are rarely recovered from non-heart-beating donors. Therefore, there is concern that donation after cardiac death may affect the recovery of thoracic organs from donors not allowed to progress to brain death. OBJECTIVE: To evaluate the potential impact of donation after cardiac death on the recovery of thoracic organs. METHODS: On the assumption that prolongation of care on all cases would result in a diagnosis of brain death. By retrospective chart review, all donations after cardiac death were evaluated for thoracic organ potential using the same standards that were used to evaluate brain-dead donors. RESULTS: During the study period there were 34 of 44 (77%) non-heart-beating donors qualified to donate abdominal organs only. Ten of 44 non-heart-beating donors (24%) qualified to potentially donate thoracic organs; the families of 4 of 10 of these donors insisted on the immediate withdrawal of life support, leaving only 6 donors with thoracic organ potential. All 6 of these donors qualified as potential heart donors and 3 as potential lung donors. CONCLUSIONS: A total of 97 organs were recovered and successfully transplanted from 44 non-heart-beating donors. If all the donors who qualified to donate thoracic organs progressed to brain death and if their thoracic organs were transplantable, then 6 additional hearts and 3 pairs of lungs may have been recovered. These data demonstrate that an aggressive donation after cardiac death program contributes significantly to the organ donor pool, with a minimal impact on potential thoracic organ recovery.

Death↗
PubMed2005

Selective attention deficits following severe closed head injury: the role of inhibitory processes.

Heightened distractibility following severe closed head injury (sCHI) may result from a deficit in selective attention. The integrity of inhibitory processes involved in selective attention was assessed through use of a negative priming paradigm, allowing dissociation of inhibitory and episodic retrieval processes. In this task, inhibitory processes are elicited under intact stimulus conditions, whereas episodic retrieval is elicited when target stimuli are degraded. Despite inconsistent evidence of inhibitory deficits following sCHI in the literature, long-term survivors of sCHI showed no negative priming under intact stimulus conditions, providing evidence of compromised inhibitory processing. The sCHI participants' demonstration of negative priming when target stimuli were degraded provides evidence that automatic retrieval processes are intact following sCHI, results that are consistent with prior findings.

Adolescent↗
PubMed2004

Retrieval inhibition in directed forgetting following severe closed-head injury.

A variant of the list method directed forgetting procedure was used to examine the role of inhibition in memory performance following severe closed-head injury (CHI). Twenty-four participants with severe CHI and 24 controls studied picture and word stimuli in both forget and remember conditions. Memory testing for the to-be-forgotten and to-be-remembered items consisted of a free-recall test followed by a source-monitoring task. Despite poorer recall performance, the participants with CHI exhibited a directed forgetting effect similar to that in controls. Item recognition scores indicated that the inhibited items were not forgotten but rather were items whose accessibility had been lowered. These findings suggest that residual memory deficits in patients with severe CHI are unlikely to reflect inefficient retrieval inhibition.

Adult↗
PubMed1999

Age-related deficits in generation and manipulation of mental images: II. The role of dorsolateral prefrontal cortex.

The authors investigated neural substrates of age-related declines in mental imagery. Healthy adult participants (ages 19 to 77) performed a series of visual-spatial mental imagery tasks that varied in apparent difficulty and involved stimuli of varying graphic complexity. The volumes of the dorsolateral frontal cortex (DLPFC) and posterior visual processing areas were estimated from magnetic resonance imaging scans. The volume of the DLPFC and the fusiform cortex, working-memory capacity, and performance on the tasks involving image generation and manipulation were significantly reduced with age. Further analyses suggested that age-related deficits in performance on mental imagery tasks may stem in part from age-related shrinkage of the prefrontal cortex and age-related declines in working memory but not from age-related slowing of sensorimotor reaction time. The volume of cortical regions associated with modality-specific visual information processing did not show a consistent relationship with specific mental imagery processes.

Adult↗
PubMedDate not supplied

Aging and directed forgetting: pre-cue encoding and post-cue rehearsal effects.

The effects of pre-cue encoding and post-cue rehearsal on item-method-directed forgetting in young and older adults were examined. In Experiment 1, level-of-processing manipulations were used to examine pre-cue representations of items in directed forgetting. In Experiment 2, pre-cue levels of processing was manipulated as well as post-cue rehearsal time. In general, young adults showed greater directed forgetting than older adults, and levels of processing did not affect directed forgetting. However, increased post-cue rehearsal time eliminated directed forgetting. These findings are discussed in terms of constraints that influence item-method-directed forgetting. It is suggested that young adults, but not older adults, may use compensatory strategies to overcome these constraints.

Adult↗
PubMedDate not supplied

Specific impairment in developmental reading disabilities: a working memory approach.

Children with developmental reading disabilities (RD) frequently display impaired working memory functioning. However, research has been divergent regarding the characteristics of the deficit. Our investigation addressed this controversy by assessing Baddeley's working memory model as a whole rather than focusing on particular aspects of it, as has been done by much of the research to date. Participants included 20 children with RD and 20 typical readers between the ages of 9 and 13. The phonological loop, visual-spatial sketchpad, and central executive were assessed according to Baddeley's model. The results demonstrated that children with RD have an impaired phonological loop but intact visual-spatial sketchpad and central executive functioning as compared to controls. In terms of the phonological loop, the deficit appears to be specific to the phonological store. Furthermore, our research supports a relationship between phonological processing and phonological loop functioning.

Adolescent↗