Effects of change in fatigue and depression on physical activity over time in relapsing-remitting multiple sclerosis

This prospective, observational study examined the effects of change in the symptoms of fatigue and depression on physical activity over time in persons with relapsing-remitting multiple sclerosis (RRMS). Adults with a confirmed diagnosis of RRMS completed a battery of questionnaires at baseline (n = 269) and six-month follow-up (n = 263). The data were analyzed using linear panel analysis and covariance modeling in Mplus 3.0. The panel model fit the data (χ(2) = 24.00, df = 15, p = 0.07, SRMR = 0.04, CFI = 0.98) and demonstrated that changes in both fatigue (path coefficient = -0.09) and depressive symptoms (path coefficient = -0.12) were significantly associated with residual change in physical activity. Such findings support the importance of fatigue and depression for predicting longitudinal changes in physical activity in adults with RRMS.     

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.     

Infants' tracking of objects and collections

Recent research suggests that infants' understanding of the physical world is more complex and adult-like than previously believed. One of the most impressive discoveries has been infants' ability to reason about medium-sized, material objects. They are able to individuate objects in a scene, and to enumerate and reason about them. This article reports a series of experiments investigating 8-month-old infants' ability to reason about collections of objects. Experiment 1 shows a sharp contrast between infants' understanding of single objects versus collections. While infants detected the discontinuous ('Magical') disappearance of a single object, they did not detect the Magical Disappearance of a non-cohesive pile of objects. Experiments 2-4 found that infants' difficulty remained even when the distinct identity of each object in the collection was emphasized, but could be overcome if infants (a) first saw the individual objects clearly separated from each other prior to their being placed together in a pile, or (b) had prior experience with the objects making up the collection. Our findings suggest that infants' expectations about object behavior are highly specific regarding the entities they are applied to. They do not automatically apply to any and all portions of matter within the visual field. Both the behavior of an entity, and infants' prior experience play roles in determining whether infants will treat that entity as an object.     

Interrupting infants’ persisting object representations: an object‐based limit?

Making sense of the visual world requires keeping track of objects as the same persisting individuals over time and occlusion. Here we implement a new paradigm using 10-month-old infants to explore the processes and representations that support this ability in two ways. First, we demonstrate that persisting object representations can be maintained over brief interruptions from additional independent events - just as a memory of a traffic scene may be maintained through a brief glance in the rearview mirror. Second, we demonstrate that this ability is nevertheless subject to an object-based limit: if an interrupting event involves enough objects (carefully controlling for overall salience), then it will impair the maintenance of other persisting object representations even though it is an independent event. These experiments demonstrate how object representations can be studied via their 'interruptibility', and the results are consistent with the idea that infants' persisting object representations are constructed and maintained by capacity-limited mid-level 'object-files'.     

Six-month-old infants use analog magnitudes to represent duration

While many studies have investigated duration discrimination in human adults and in nonhuman animals, few have investigated this ability in infants. Here, we report findings that 6-month-old infants are able to discriminate brief durations, and, as with other animal species, their discrimination function is characterized by Weber's Law: proportionate difference rather than absolute difference between stimuli determined successful discrimination. Importantly, paralleling results found with nonhuman animals, the Weber function that we found for infants' discrimination of time is the same as that found for their discrimination of number. Infants discriminated durations of an audiovisual event differing by a 1:2 ratio, but not those differing by a 2:3 ratio, over a range of durations. This suggests that (a) in human as in nonhuman animals, the same mental mechanism may underlie the ability to measure duration as to represent number, and (b) we may share this mental mechanism with other animal species.     

Working memory and strategies in syllogistic-reasoning tasks

It has often been asserted that working-memory limitations are a major factor contributing to problem difficulty; for example, Johnson-Laird’s (1983) mental-models theory appeals to working memory limitations to explain the difficulty of syllogistic reasoning. However, few studies have directly explored working memory in problem solving in general or syllogistic reasoning in particular. This paper reports two studies. In the first, working-memory load was varied by presenting syllogistic tasks either verbally or visually (so that the premises were continuous1y avai1ab1e for inspection). A significant effect of memory load was obtained. In the second study, premises were presented visually for a subject-determined time. Dual-task methods were used to assess the role of working-memory components, as identified in Baddeley’s (1986) model. Syllogistic performance was disrupted by concurrent random-number generation but not by concurrent articulatory suppression or by concurrent tapping in a preset pattern. Furthermore, the concurrent syllogism task interfered with random generation and to a lesser extent with articulatory suppression, but not with tapping. We conclude that while the central-executive component of working memory played a major role in the syllogistic-task performance reported here, the articulatory loop had a lesser role, and the visuospatial scratch pad was not involved.     

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.     

Archaeology and cognitive evolution

Archaeology can provide two bodies of information relevant to the understanding of the evolution of human cognition--the timing of developments, and the evolutionary context of these developments. The challenge is methodological. Archaeology must document attributes that have direct implications for underlying cognitive mechanisms. One example of such a cognitive archaeology is found in spatial cognition. The archaeological record documents an evolutionary sequence that begins with ape-equivalent spatial abilities 2.5 million years ago and ends with the appearance of modern abilities in the still remote past of 400,000 years ago. The timing of these developments reveals two major episodes in the evolution in spatial ability, one, 1.5 million years ago and the other, one million years later. The two episodes of development in spatial cognition had very different evolutionary contexts. The first was associated with the shift to an open country adaptive niche that occurred early in the time range of Homo erectus. The second was associated with no clear adaptive shift, though it does appear to have coincided with the invasion of more hostile environments and the appearance of systematic hunting of large mammals. Neither, however, occurred in a context of modern hunting and gathering.