Language functioning after bilateral prefrontal leukotomy

Three groups of patients with orbital frontal lesions secondary to leukotomy were compared to psychiatric and normal control groups on a series of tasks involving language. The results indicated that chronic orbital frontal lesions, at least in the patients in this study, do not affect language as defined by the tasks used in the study. The frontal lobes, when implicated in language, appear to require dorsal-lateral or medial cortical involvement.     

Age,working memory,and the Tower of London task

The current study explores the role of three components of working memory in age differences in an executive task, the Tower of London (TOL). The TOL task is sensitive to frontal lobe damage, and is widely used to measure planning ability. Dual tasks were used to test the involvement of the phonological loop (articulatory suppression), visuospatial buffer (pattern tapping), and central executive (random generation) in age effects on the TOL. Older adults showed greater reliance than young on domain-specific verbal and spatial memory components in performing the TOL. In terms of executive function, qualitatively different interference patterns were seen in young and old participants. However, the validity of using random generation tasks to assess executive function in older populations can be questioned. For older participants, performing the TOL loads all components of working memory, whereas for the younger participants the TOL more specifically loads executive functioning.     

The selective disruption of spatial working memory by eye movements

In the late 1970s/early 1980s, Baddeley and colleagues conducted a series of experiments investigating the role of eye movements in visual working memory. Although only described briefly in a book (Baddeley, 1986), these studies have influenced a remarkable number of empirical and theoretical developments in fields ranging from experimental psychology to human neuropsychology to nonhuman primate electrophysiology. This paper presents, in full detail, three critical studies from this series, together with a recently performed study that includes a level of eye movement measurement and control that was not available for the older studies. Together, the results demonstrate several facts about the sensitivity of visuospatial working memory to eye movements. First, it is eye movement control, not movement per se, that produces the disruptive effects. Second, these effects are limited to working memory for locations and do not generalize to visual working memory for shapes. Third, they can be isolated to the storage/maintenance components of working memory (e.g., to the delay period of the delayed-recognition task). These facts have important implications for models of visual working memory.     

Relating the adolescent mother—child relationship to preschool outcomes

Two domains of potential risk in relation to the cognitive-linguistic outcomes of preschool children of adolescent mothers were investigated: (1) interactive features of the mother—child relationship and (2) aspects of the demographic context of parenting. Sixty-nine adolescent mothers and their children participated in evaluations when the children were 13, 20, 30, and 44 months old. Results indicated that the cognitive-linguistic development of children of adolescent mothers was affected by both the mother—child relationship and cumulative index of demographic risk. Specifically, positive maternal affect, mother—child verbal reciprocity, mother—child interactive fit, and cumulative demographic risk all contributed to explaining difficulties in preschool cognitive and linguistic functioning in children of adolescent mothers.     

Visual similarity effects in immediate verbal serial recall

The role of visual working memory in temporary serial retention of verbal information was examined in four experiments on immediate serial recall of words that varied in visual similarity and letters that varied in the visual consistency between upper and lower case. Experiments 1 and 2 involved words that were either visually similar (e.g. fly, cry, dry; hew, new, few ) or were visually distinct (e.g. guy, sigh, lie; who, blue, ewe ). Experiments 3 and 4 involved serial recall of both letter and case from sequences of letters chosen such that the upper- and lower-case versions were visually similar, for example Kk, Cc, Zz, Ww , or were visually dissimilar, for example Dd, Hh, Rr, Qq . Hence in the latter set, case informationwas encoded interms of both the shape and the size of the letters. With both words and letters, the visually similar items resulted in poorer recall both with and without concurrent articulatory suppression. This visual similarity effect was robust and was replicated across the four experiments. The effect was not restricted to any particular serial position and was particularly salient in the recall of letter case. These data suggest the presence of a visual code for retention of visually presented verbal sequences in addition to a phonological code, and they are consistent with the use of a visual temporary memory, or visual "cache", in verbal serial recall tasks.     

Prospective and retrospective memory in normal aging and dementia: an experimental study

Two experiments investigated the effects of normal aging and dementia on laboratory-based prospective memory (PM) tasks. Participants viewed a film for a later recognition memory task. In Experiment 1, they were also required either to say "animal" when an animal appeared in the film (event-based PM task) or to stop a clock every 3 min (time-based PM task). In both tasks, young participants were more successful than older participants, who were, in turn, more successful than patients with Alzheimer's disease (AD). For successful remembering in the time-based task, older participants and AD patients checked the clock more often than did young participants. In Experiment 2, participants were asked to reset a clock either when an animal appeared in the film (unrelated cue-action) or when a clock appeared in the film (related cue-action). Responses were faster in the related condition than in the unrelated condition. Again, there were differences in PM performance between young and older participants, and between older participants and AD patients. The observed deficits were not due to the forgetting of the PM task instructions in either experiment. Retrospective memory (RM) tasks (digit span, sentence span, free recall, and recognition) were more impaired by AD than were the PM tasks. Factor analysis revealed separate factors corresponding to RM and PM.     

Age,executive function,and social decision making: a dorsolateral prefrontal theory of cognitive aging

Current neuropsychological models propose that some age-related cognitive changes are due to frontal-lobe deterioration. However, these models have not considered the possible subdivision of the frontal lobes into the dorsolateral and ventromedial regions. This study assessed the age effects on 3 tasks of executive function and working memory, tasks dependent on dorsolateral prefrontal dysfunction; and 3 tasks of emotion and social decision making, tasks dependent on ventromedial prefrontal dysfunction. Age-related differences in performance were found on all tasks dependent on dorsolateral prefrontal dysfunction. In contrast, age-related differences were not found on the majority of the tasks dependent on ventromedial prefrontal dysfunction. The results support a specific dorsolateral prefrontal theory of cognitive changes with age, rather than a global decline in frontal-lobe function.