Contrasting patterns of memory span decrement in ageing and aphasia

As compared with young adult controls, elderly subjects matched for verbal ability showed only a minor deficit in mean auditory letter memory span but proportionately more dependence upon the occurrence of letter groupings prevalent in the written language. An aphasic group that also had a relatively limited mean letter span conversely made no detectable use at all of such groupings. These findings suggest that the aged tend if anything towards undue assimilation of information into preformed schemata, while aphasics accommodate to individual messages without evidence of such organization

Confabulation, delusion, and anosognosia: motivational factors and false claims

False claims are a key feature of confabulation, delusion, and anosognosia. In this paper we consider the role of motivational factors in such claims. We review motivational accounts of each symptom and consider the evidence adduced in support of these accounts. In our view the evidence is strongly suggestive of a role for motivational factors in each domain. Before concluding, we widen the focus by outlining a tentative general taxonomy of false claims, including false claims that occur in clinical settings as well as more garden-variety false claims, and incorporating both motivational and nonmotivational approaches to explaining such claims

Counting Consciousnesses: None, One, Two, or None of the Above?

In a minute there is time For decisions and revisions which a minute will reverse. --T. S. Eliot, "The Love Song of J. Alfred Prufrock" In a second there is also time enough, we might add. In his dichotomizing fervor, Bogen fails to realize that our argument is neutral with respect to the number of consciousnesses that inhabit the normal or the split-brain skull. Should there be two, for instance, we would point out that within the neural network that subserves each, no privileged locus should be postulated. (Midline location is not the issue--it was only a minor issue for Descartes, in fact.

Progress in the Measurement of Laterality and Implications for Dyslexia Research

The final paper in this year's journal is by Merrill Hiscock and Marcel Kinsbourne, who have done so much over the years to clarify our understanding of neuropsychological processes and assessment, especially as these relate to reading disability. In this paper, Hiscock and Kinsbourne review the current research on laterality, long hypothesized to be a predictor and correlate of specific reading disability. In a carefully argued and well-documented discussion, they explain why it is that the evidence for an association between reading and laterality remains so equivocal, even after years of technological advances and ever more well-controlled studies. Of particular concern, they argue, is the fact that we have not yet reached the point where we can precisely assess laterality of individual childrenmthey emphasize the fact that the currently available methods are still useful only for interpretation of group data. This discussion should provide food for thought for clinicians who employ neuropsychological assessment, as well as for researchers seeking methods for assessing laterality using behavioral techniques. As Hiscock and Kinsbourne point out, there will be much to learn in the very near future, as data from brain functioning are correlated with neuropsychological behavior--these will be developments worth watching for and it is best to be well-prepared to interpret them judiciously

Time and the Observer

Two models of consciousness are contrasted with regard to their treatment of subjective timing. The standard Cartesian Theater model postulates a place in the brain where "it all comes together": where the discriminations in all modalities are somehow put into registration and "presented" for subjective judgment. In particular, the Cartesian Theater model implies that the temporal properties of the content-bearing events occurring within this privileged representational medium determine subjective order. The alternative, Multiple Drafts model holds that whereas the brain events that discriminate various perceptual contents are distributed in both space and time in the brain, and whereas the temporal properties of these various events are determinate, none of these temporal properties determine subjective order, since there is no single, constitutive "stream of consciousness" but rather a parallel stream of conflicting and continuously revised contents. Four puzzling phenomena that resist explanation by the standard model are analyzed: two results claimed by Libet, an apparent motion phenomenon involving color change (Kolers and von Grunau), and the "cutaneous rabbit" (Geldard and Sherrick) an illusion of evenly spaced series of "hops" produced by two or more widely spaced series of taps delivered to the skin. The unexamined assumptions that have always made the Cartesian Theater model so attractive are exposed and dismantled. The Multiple Drafts model provides a better account of the puzzling phenomena, avoiding the scientific and metaphysical extravagances of the Cartesian Theater