Lack of the metabotropic glutamate receptor subtype 7 selectively modulates Theta rhythm and working memory

Metabotropic glutamate receptors (mGluRs) are known to play a role in synaptic plasticity and learning. We have previously shown that mGluR7 deletion in mice produces a selective working memory (WM) impairment, while other types of memory such as reference memory remain unaffected. Since WM has been associated with Theta activity (6-12 Hz) in EEGs, and since EEG abnormalities have been observed in these mice before, we studied the effect of mGluR7 gene ablation on EEG activity in the hippocampus, in particular in the Theta range, during performance of a WM task. In an eight-arm maze with four arms baited, mGluR7 knock-out (KO) and wild-type mice committed the same number of reference memory errors, whereas KOs committed more WM errors. While performing the task, KO mice showed substantially higher Theta amplitudes, and the ratio of Theta to overall EEG power was much increased. No change was seen in the Delta (0-5 Hz), or Gamma (30-40 Hz) EEG bands compared with controls. When recording EEGs during periods of rest in the home cages, no difference was seen between groups. These findings suggest that mGluR7 is important for modulation and control of Theta activity. Since only WM was affected, and only the Theta range of EEG activity was altered, these results show a correlation between Theta rhythm and WM performance, and therefore support the concept that Theta activity in the hippocampus is involved in WM storage.     

Analysis of response repetition as an error-correction strategy during sight-word reading

A great deal is known about the effects of positive reinforcement on response acquisition; by contrast, much less research has been conducted on contingencies applied to errors. We examined the effects of response repetition as an error-correction procedure on the sight-word reading performance of 11 adults with developmental disabilities. Study 1 compared single-response (SR) repetition and multiple-response (MR) repetition, and results showed that all 6 participants acquired more sight words with the MR procedure. Study 2 compared MR error correction following every incorrect response (continuous) and following one third of incorrect responses (intermittent), and results showed that all 6 participants acquired more sight words when error correction was continuous. Study 3 compared MR error correction in which errors required practice of the training word (relevant) versus a different word (irrelevant), and results showed that 3 of 9 participants showed better performance under the relevant condition; however, all participants showed improvement even under the irrelevant condition. Findings are discussed in terms of the behavioral processes by which error correction may enhance performance during acquisition.     

Context effects: the proportional difference model and the reflection of preference

The reflection effect (D. Kahneman & A. Tversky, 1979) was investigated using the stochastic model of choice developed by C. Gonzalez-Vallejo (2002). The model assumes that individuals make trade-offs among attribute values by relying on a difference variable. The model also specifies a threshold representing individual proclivities to reach to attribute differences. Two experiments demonstrated that changes in risk attitudes, from a gain to a loss situation, depended on the stimuli as well as on individuals' thresholds. Thresholds were generally lower in losses than in gains, indicating a risk-taking tendency. Thresholds were also lower when participants were endowed with greater savings. Model testing revealed better fits for the stochastic model than cumulative prospect theory (A. Tversky &. D. Kahneman, 1992).     

Measuring the perceptual magnet effect in the perception of /i/ by German listeners

In a study of the internal category structure of the vowel /i/, Kuhl found a “perceptual magnet effect”: Discrimination sensitivity was poorer for category instances that were acoustically similar to the category prototype than it was for category instances that were not. The typicality of category exemplars was determined by goodness judgments and was found to correlate with the acoustics of average production. Analysis and interpretation of discrimination performance relied on two important assumptions: that listeners perceived all stimuli presented as exemplars of the same vowel category and that, apart from the influence of phonetic coding, discrimination sensitivity was the same across the investigated part of the vowel space. In the present study, it is shown that production and perception estimates of the category prototype may diverge, possibly because listeners seem to prefer hyperarticulated variants of vowel categories. An approach towards measurement of intra-category discrimination minima is put forward and tested that protects against intercategory confounds and avoids the isosensitivity assumption. Received: 26 November 1997 / Accepted: 25 May 1998     

Inertial eigenvalues, rod density, and rod diameter in length perception by dynamic touch

Four experiments addressed the relevance of the eigenvaluesI _k of the inertia tensor for perceiving length by dynamic touch. Experiments 1–2 focused on the consequences of limiting variation in the minimum eigenvalueI ₃. Both revealed that perceived length is a function ofI _k . Whether the contribution ofI ₃ is detected, however, depends on the range of values that characterize a particular object set. Experiments 3–4 considered the relationship between an independent index of a rod’s diameter, which does not affectI _k , and actual manipulation of a rod’s diameter, which does affectI _k . Whereas the former appeared as satisfaction of implicit instructions to alter reports of perceived length, the latter entailed actual differences in perceived length in accordance withI _k . Results are discussed with respect to the links among actual length, perceived length, andI _k , as well as, in particular, how these links guarantee that perceived length is in the range of actual lengths.     

REMOVING VEILS OF IGNORANCE1

For more than two millennia the development of philosophy in what is called the West has been the province of men who trace their intellectual heritage to (some) men in ancient Greece. Within “the development of philosophy” I include the training of philosophers as well as publishing and preserving philosophical work in libraries. Thus I regard philosophy as a very material as well as spiritual enterprise. My focus here is on the spiritual impact, actual and potential, of recent changes in the material base of philosophy and the material impact of recent changes in the spiritual focus of philosophers. Before the Twentieth Century, the most significant transitions in the development of Western philosophy were its coming under the domination of Christian religious institutions and then its becoming relatively freed from such domination. Since the advent of the Twentieth Century, the most significant transitions may come from the increasing access to academic institutions of the middle and working classes, of people of color with histories of oppression by white societies, and of women from all classes and ethnic backgrounds—people who do not always or only trace their intellectual heritages to men of ancient Greece. What differences might these changes make to, and call for in, the development of philosophy? What I have thought about most are differences made by women and differences that have drawn in women to academic philosophy in Western democracies, such as the United States. Twentieth Century women in these contexts have published substantial bodies of philosophical inquiry with feminist agendas (both philosophy of feminism and philosophy manifesting feminist perspectives in ethics, epistemology, etc.). I want to comment on two features of such inquiry that often make it attractive to women less readily engaged by the traditions defined by privileged men. These features are holism and what I call “historical particularism.” I begin with “particularism.”