Different patterns of cognitive slowing produced by Alzheimer's disease and normal aging

Aging has previously been shown to produce a generalized proportional slowing of all cognitive operations. In contrast, the present results suggested that Alzheimer's disease produces a disproportionate reduction in the speed with which patients carry out one or more mental operations. The tasks that demented patients found particularly difficult involved either a self-directed search of their lexicon or the use of familiarity information.     

Semantic memory in Alzheimer's disease

Patients with Alzheimer's disease have been suggested to have a semantic memory impairment not present in the normal old. This article reviews the performance of Alzheimer patients on tests of various aspects of semantic memory, including word finding, knowledge of the semantic attributes, and associates of concepts, as well as their category membership. The effect that semantic context has on cognitive processes such as lexical and semantic priming and memory encoding is also reviewed. Finally, the ability of theoretical constructs such as implicit memory and automaticity to explain intertask variability in Alzheimer patients' semantic performance is discussed.     

Preserved organization of semantic attributes in Alzheimer's disease

This study investigated whether Alzheimer's disease (AD) disrupts the basic organization of the semantic attributes of concepts. Young and normal older subjects and AD patients were presented with a target concept followed by a stimulus word and were to decide whether the stimulus was related to the target. On those trials where it was, the stimulus was either a high-, medium-, or low-dominance attribute of the target. The higher the normative dominance, the more important the attribute to concept meaning. In all 3 subject groups, decision time varied as a function of dominance. The higher the dominance, the faster the decision. Attribute dominance affected the performance of AD patients more than that of normal subjects. These results suggest that AD patients retain their knowledge of the relative importance that the different attributes of a concept have for concept meaning.     

Aging increases the energetic demands of episodic memory: a cardiovascular analysis

We hypothesized that older volunteers allocate more attentional resources to memory maintenance than do younger volunteers. Allocation of a resource supporting memory maintenance was inferred from performance and cardiovascular measures. Eighteen 18- to 26-year-old men and eighteen 60- to 79-year-old men performed a serial memory task both as a single task and as a dual task that added simple reaction time stimuli. Items presented early or later in the serial list created relatively low or high memory load. The results suggested that older men allocated greater attention to memory maintenance, particularly during high-memory-load items. They showed a slowing of dual-task reaction time and increased heart rate during high- vs. low-memory-load items. Cardiac and vascular reactions further suggested that memory maintenance is supported by phasic autonomic adjustments and that with age, more of this support is required for adequate maintenance of episodic memory.     

Intellectual differences in relation to personal and family handedness

Right, mixed and left-handed college students were given the complete WAIS, and a series of cognitive factor tests. Results showed left- and mixed-handed individuals to have a significantly lower full scale I.Q. than right-handers. There was no difference between the mixed and left-handers. In all three handedness groups, subjects with a positive family history of sinistrality had a lower full scale I.Q. than did subjects without left-handed relatives. Neither handedness nor family history differentially affected the Verbal or Performance subscales, nor did they have a significant effect on scores in the other cognitive tests. These results are discussed with respect to Levy's theory of hemispheric specialization, and to the role of inheritance and brain damage in the causation of left- and mixed-handedness.     

A comparison of dichotic and visuo-acoustic competition in hemispherectomized patients

Following hemispherectomy, patients performing dichotic listening tasks have great difficulty reporting items presented to the ear ipsilateral to their intact hemisphere. One possible cause is an attentional imbalance which, when competing inputs are received from both sides of space, restricts the patient's attention to the stimulus contralateral to his remaining hemisphere. If this explanation is true, then a similar ipsilateral ear decrement should occur when a competing visual stimulus is presented in the contralateral field. In the present study, however, hemispherectomy patients easily reported a digit presented to the ear ipsilateral to their intact hemisphere despite the concurrent presentation of a visual digit to their contralateral field.     

Presence and television.

Film and a number of emerging entertainment technologies offer media consumers an illusion of nonmediation known as presence. To investigate the possibility that television can evoke presence, 65 undergraduate students were shown brief examples of rapid point‐of‐view movement from commercially available videotapes on a television with either a small screen (12 inches [30.5 cm], measured diagonally) or a large screen (46 inches [116.8 cm]). Participants' responses were measured via a questionnaire and a computer‐based recording of arousal (electrodermal activity). Viewers of both televisions reported an enjoyable sense of physical movement, excitement, involvement, and a sense of participation. Furthermore, as predicted, participants who watched the large screen television thought the movement in the scenes was faster, experienced a greater sense of physical movement, enjoyed the movement to a greater extent, found the viewing experience more exciting, and were more physiologically aroused. Practical and theoretical implications are discussed.     

Forms, uses and functions of children's favourite objects

In this study, the notion of a favourite object is used as a heuristic concept for things that children are occupied with and absorbed by. According to earlier studies, favourite objects can be grouped into four categories: forerunners of transitional objects, primary and secondary transitional objects, and favourite toys. This initial classification was compared to results of cluster analyses of characteristics of favourite objects among 32 preschool and 30 primary school children, corroborating the initial classification and specifying the typology. The distribution of types of objects was different for the two groups of children, but was not dependent on age within groups or, for the preschool children, on mental development. These results indicate that changes of favourite objects with mental maturation are slow.
The softness of the material of primary and secondary transitional objects and the preference for objects that could be kept close to the body suggest that the comforting character of these favourite objects has its root in the child's self-soothing actions with the object.     

A Positron Emission Tomography (PET) Study of Autobiographical Memory Retrieval

Memory for the experiences of one's life, autobiographical memory (AM), is one of the most human types of memory, yet comparatively little is known of its neurobiology. A positron emission tomography (PET) study of AM retrieval revealed that the left frontal cortex was significantly active during retrieval (compared to memory control tasks), together with activation in the inferior temporal and occipital lobes in the left hemisphere. We propose that this left frontal lobe activation reflects the operation of control processes that modulate the construction of AMs in posterior neocortical networks.