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D L Kigar

Publications and source records attributed to D L Kigar.

5 recordsLinked to original sources
PubMed2005

Intelligence and brain size in 100 postmortem brains: sex, lateralization and age factors.

The neural basis of variation in human intelligence is not well delineated. Numerous studies relating measures of brain size such as brain weight, head circumference, CT or MRI brain volume to different intelligence test measures, with variously defined samples of subjects have yielded inconsistent findings with correlations from approximately 0 to 0.6, with most correlations approximately 0.3 or 0.4. The study of intelligence in relation to postmortem cerebral volume is not available to date. We report the results of such a study on 100 cases (58 women and 42 men) having prospectively obtained Full Scale Wechsler Adult Intelligence Scale scores. Ability correlated with cerebral volume, but the relationship depended on the realm of intelligence studied, as well as the sex and hemispheric functional lateralization of the subject. General verbal ability was positively correlated with cerebral volume and each hemisphere's volume in women and in right-handed men accounting for 36% of the variation in verbal intelligence. There was no evidence of such a relationship in non-right-handed men, indicating that at least for verbal intelligence, functional asymmetry may be a relevant factor in structure-function relationships in men, but not in women. In women, general visuospatial ability was also positively correlated with cerebral volume, but less strongly, accounting for approximately 10% of the variance. In men, there was a non-significant trend of a negative correlation between visuospatial ability and cerebral volume, suggesting that the neural substrate of visuospatial ability may differ between the sexes. Analyses of additional research subjects used as test cases provided support for our regression models. In men, visuospatial ability and cerebral volume were strongly linked via the factor of chronological age, suggesting that the well-documented decline in visuospatial intelligence with age is related, at least in right-handed men, to the decrease in cerebral volume with age. We found that cerebral volume decreased only minimally with age in women. This leaves unknown the neural substrate underlying the visuospatial decline with age in women. Body height was found to account for 1-4% of the variation in cerebral volume within each sex, leaving the basis of the well-documented sex difference in cerebral volume unaccounted for. With finer testing instruments of specific cognitive abilities and measures of their associated brain regions, it is likely that stronger structure-function relationships will be observed. Our results point to the need for responsibility in the consideration of the possible use of brain images as intelligence tests.

Aged↗
PubMed1995

Women have greater density of neurons in posterior temporal cortex.

Cytoarchitectonic area TA1 (von Economo) in the cortex of the planum temporale within the Sylvian fissure, which is auditory association cortex and documented to be part of the neural substrate of language functions, was studied quantitatively in the brain specimens of five women and four men (mean age of 50 year). All cases were documented to be medically and cognitively normal, and consistently right-handed. We investigated the possibility that the difference in brain size between men and women is reflected in differences in the numerical density of neurons in area TA1, an area associated with morphologic and psychological sex differences. Neuron counts were made directly through cell differentiation under the microscope from Nissl-stained sections. Cortical depth, the number of neurons through the depth of cortex under 1 mm2 of cortical surface (Nc), and the number of neurons per unit volume (Nv) were obtained for the total cortex and for each of the six layers in each hemisphere. For total cortex in both hemispheres, depth and Nc were similar, but Nv was greater by 11% in women, with no overlap of scores between the sexes. The sex difference in Nv was attributable to layers II and IV; in contrast, Nv did not differ between the sexes in layers III, V, and VI. This is the first report of such a sex difference in human cortex. The results suggest that the cortical functional unit has a different ratio of input and output components in men and women which could have implications for the sex differences in cognition and behavior. Due to the small sample size and the homogeneity of the cases studied, generalizability of the results requires replication by other studies. In addition, cytoarchitectonic mapping indicated that area TA1 also occurs in the vertical posterior wall of the Sylvian fissure, providing evidence that anatomical definition of the planum temporale should include the posterior vertical wall of the superior temporal gyrus.

Adult↗
PubMed1992

Sylvian fissure morphology and asymmetry in men and women: bilateral differences in relation to handedness in men.

The anatomy of the sylvian fissure in the human brain was studied to develop reliable criteria for anatomical landmarks of the posterior part of the fissure for use in its definition and measurement; to quantify right-left asymmetries in segments of the sylvian fissure; to assess whether any anatomical features are associated with hand preference (selected as one index of hemispheric functional asymmetry); and whether structure-function relationships are similar in men and women. A sample of 67 brain specimens (24 men and 43 women, mean age = 53 years) was studied postmortem (with the aid of dissection) from people who had been tested before death for detailed hand preference. Sylvian fissure anatomy in the human brain is very variable and no agreement exists as to the point of its posterior termination. The posterior ascending ramus, originating at the posterior bifurcation of the fissure, was found to be the continuation of the main limb of the sylvian fissure. Three segments of the sylvian fissure were defined and measured: anterior, horizontal, and vertical. The anterior segment showed no asymmetry; the horizontal segment was twice as large on the left side as on the right; and the vertical segment twice as large on the right. The two asymmetries counterbalanced each other, and overall asymmetry in the posterior region (horizontal plus vertical) was minimal. The basic asymmetry is in the position at which the fissure turns up, resulting in the different extent and position of the surrounding right and left parietal and temporal gyri and associated cytoarchitectonic regions. The possible embryological course of the asymmetry is discussed. Handedness correlated with anatomy of the sylvian fissure in men. In contrast to general expectation, hand preference was associated with a bilateral feature of morphology, and not with less asymmetry in non-right-handers. Men having consistent-right-hand preference had longer horizontal segments in both hemispheres compared to men not having consistent-right-hand preference. The direction and magnitude of asymmetry did not differ between the two male hand-preference groups. Since hand preference is an index of other motor and perceptual functions which are asymmetrically represented in the two hemispheres in gyri surrounding the sylvian fissure, it is suggested that anatomy of the sylvian fissure is related to functional asymmetries in men. A sex difference in structure-function relationship was observed. No association was found between hand preference and sylvian fissure anatomy in women.(ABSTRACT TRUNCATED AT 400 WORDS)

Brain↗
PubMedDate not supplied

A computer-assisted direct-imaging system to obtain numerical densities of neurons in human cortex.

Studies of the numerical density of microscopic items in brain tissue is a time-consuming endeavor. However, such information is important for numerous issues such as the relationship between structure and function in the normal brain, individual differences, and studies of brains of neuropsychiatric patients. A computer-assisted imaging system specifically devised to obtain estimates of numerical densities in human cortex is described here. Its main advantage is that the microscopist can analyze the original image directly under the microscope, and most aspects of data acquisition and quantitative analysis are accomplished by the computer. The key features of the system are a Microvid (an electronic camera lucida) and the use of X, Y, and Z stage encoders in conjunction with three-dimensional computer software. The complete system is relatively inexpensive and is simple to set up and use. The reliability and validity of the numerical densities obtained using this system are documented.

Cell Differentiation↗