William Marks

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 Baddeleys 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 Baddeleys 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.

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.

Age-related deficits in generation and manipulation of mental images: I. The role of sensorimotor speed and working memory.

The authors investigated age-related slowing of information processing in mental imagery tasks. Eighty-five healthy adults (ages 18 to 77) performed a visual, sensorimotor, reaction-time task; a visual-perceptual choice reaction task; and 3 mental imagery tasks that varied in apparent difficulty and involved stimuli at 2 levels of graphic complexity. Age was associated with prolongation of response time across all tasks and both levels of stimulus complexity. Accuracy of response was adversely affected by increase in stimulus complexity in all tasks, whereas it was negatively related to age only on the tasks with substantial mental imagery requirements. Slowing of information processing and reduction in accuracy were mediated by declines in working memory but not by decrease of sensorimotor speed.

Effects of severe closed-head injury on three stages of information processing

The present study investigated the loci of the information-processing delay that characteristically follows severe closed-head injury (CHI). Sternbergs additive-factors logic was used to determine the effects of severe CHI on the central information-processing stages of stimulus encoding, memory comparison, and decision-making/response-selection. The task variables used to define the stages operationally were stimulus quality, memory set size, and stimulus-response compatibility. Twenty subjects who had sustained a severe CHI more than 18 months earlier and 20 matched control subjects completed a stimulus encoding by response selection task in Experiment 1, and a Sternberg high-speed memory scanning task in Experiment 2. The CHI group performed the stimulus encoding and decision-making/response-selection stages of processing significantly slower than did the control group. However, no significant group differences were found on the memory comparison stage, suggesting that memory comparison processes may be relatively intact in long-term patients with severe head trauma. The results are discussed in relation to a global and a late-specificity hypothesis of central processing deficits following severe CHI. The possibility that cognitive processes demanding less attention may be more resilient to injury is also considered.

Encoding processes and attentional inhibition in directed forgetting.

Lexical decisions were used to evaluate whether forget (F)-cued prime words affect subsequent encoding of target words relative to remember (R)-cued prime words. In 3 experiments, R-cued primes were better recalled than F-cued primes. Targets that followed F-cued primes were responded to faster than targets that followed R-cued primes in same-case and different-case identity priming. Semantic priming occurred for targets that followed both types of memory-cued primes. However, response times were longer for both related and unrelated targets following R-cued primes relative to F-cued primes. These results indicate that R and F items are processed to similar levels of representation and inhibitory mechanisms do not attenuate encoding of F items. However, there is slower access to working memory for information that follows R-cued items.

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.

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.

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 groups memory performance are discussed.

Elaborative processing of pictures in verbal domains

Four experiments were performed to evaluate the effect of semantic and nonsemantic verbal elaboration of the names of pictures on free recall, picture-name recognition, and picture recognition. Elaboration was manipulated by having subjects decide if the names of pictures contained two letters, rhymed with another word, or were appropriate in a sentence frame. Semantic elaboration of the names of pictures in sentence contexts requiring positive responses resulted in better name recall (Experiment 1) and name recognition (Experiments 1 and 2) than did nonsemantic elaborations (rhyme- and letter-identification tasks). However, the effects of elaborating pictures-names were greatly reduced for picture recognition (Experiments 3 and 4). The results are described in terms of elaborative processing after semantic access. Following initial semantic access, the names of pictures may be further elaborated. Semantic elaboration of the names of pictures typically leads to better retention than does nonsemantic elaboration. However, perceptual records about the appearance of objects may be relatively independent of orienting tasks that elaborate pictures- names.

Encoding pictures in scene contexts: Does task demand influence effects of encoding congruity?

Three experiments examined the role of task demand in accounting for the effect of encoding congruity in levels-of-processing research