Anatomical Specialization of the Anterior Motor Speech Area: Hemispheric Differences in Magnopyramidal Neurons

The lateralization of motor speech function to the left hemisphere is supported by multiple lines of evidence, but relatively little is known about the anatomical basis of that specialization. In a preliminary study, we recently reported that area 45 of the left hemisphere (Broca′s area) contained a subpopulation of magnopyramidal neurons which were significantly larger than any seen in the homotopic region of the right hemisphere (Hayes and Lewis, 1993a). In the present study we examined a larger sample of cases in order to determine how consistently this difference is present in the population, if it is specific to Broca′s area or is a general feature of cortical regions mediating lateralized functions, and whether the subpopulation of large magnopyramidal neurons in left area 45 can be distinguished by their chemical phenotype. In Nissl-stained sections from 19 human brains, the mean (±SD) cross-sectional area of the largest layer III pyramidal neurons in area 45 was significantly (p < .0001) greater in the left hemisphere (522.1 ± 128.3 μm²) than in the right (454.1 ± 121.5 μm²). This interhemispheric difference appeared to be a unique characteristic of the largest neurons, since the mean size of all layer III pyramids in this area was not significantly different in the left (206.2 ± 93.5 μm²) and right (213.3 ± 103.9 μm²) hemispheres. In contrast to area 45, there was no interhemispheric difference in the mean cross-sectional area of the largest layer III pyramids in another lateralized region, primary motor cortex. in addition, in area 46, a region of prefrontal association cortex not known to be functionally lateralized, the mean somal size of the largest layer III pyramidal neurons was significantly (p < .001) smaller in the left hemisphere (402.4 ± 84.9 μm²) than in the right (437.8 ± 88.3 μm²). Finally, although the large layer III pyramids in area 45 were immunoreactive for nonphosphorylated neurofilament protein in both hemispheres, the mean cross-sectional area of the largest labeled neurons was significantly larger (p < .002) in the left hemisphere (525.2 ± 149.0 μm²) than in the right (490.3 ± 154.1 μm²). These findings demonstrate that layer III of Broca′s area contains a distinctive subpopulation of neurons that may play an important role in the specific functional architecture of this region.     

Finkish Dispositions

Many years ago, C.B. Martin drew our attention to the possibility of 'finkish' dispositions: dispositions which, if put to the test would not be manifested, but rather would disappear. Thus if x if finkishly disposed to give response r to stimulus s , it is not so that if x were subjected to stimulus r , x would give response z ; so finkish dispositions afford a counter-example to the simplest conditional analysis of dispositions. Martin went on to suggest that finkish dispositions required a theory of primitive causal powers; there, I think, he was mistaken. All that they require is an improved conditional analysis, and this improved analysis can be built upon whatever treatments of properties and of laws we may favour on other grounds.     

Toward a profile of the female voter: Sex differences in perceived physical attractiveness and competence of political candidates

Recent national attention has focused on women's voting behavior because of this group's increasing power to determine outcomes of local, state, and national elections. Research has not established whether males and females use the same decision rules in evaluating political candidates. Because of the link between perceived physical attractiveness and many positive attributes, the present study examined sex differences in ratings of attractiveness and competence of 44 men and women in the U.S. House of Representatives. Results indicated that males and females use similar rules in evaluating male politicans' attractiveness. Women show a pro-female sentiment in evaluating female politicians' competence. Physical attractiveness was positively related to perceived competence for both male and female politicians. Contrary to previous research, women voters showed a marked pro-female sentiment, and men were neutral, evaluating male and female politicians similarly.     

Marginal distributions for the estimation of proportions inm groups

A Bayesian Model II approach to the estimation of proportions inm groups (discussed by Novick, Lewis, and Jackson) is extended to obtain posterior marginal distributions for the proportions. It is anticipated that these will be useful in applications (such as Individually Prescribed Instruction) where decisions are to be made separately for each proportion, rather than jointly for the set of proportions. In addition, the approach is extended to allow greater use of prior information than previously and the specification of this prior information is discussed.We are grateful to a reviewer for suggestions that made possible a more concise and complete presentation of our work.     

An EEG investigation of awareness during anaesthesia

Previous studies of awareness during anaesthesia have used patients undergoing surgery. In an attempt to overcome the complications of anxiety and specific stimuli of surgery, this study used healthy volunteers in a laboratory setting. No evidence of recall of events taking place during light anaesthesia was found.