Structural changes in the brain in depression and relationship to symptom recurrence

Depression is an important public health problem affecting about 15% of the general population; however, little is known about possible changes in the brain that might underlie the disorder. Neuroimaging has been a powerful tool to map actual changes in the brain structure of depressed patients that might be directly related to their symptoms of depression. Some imaging studies of brain structure have shown smaller hippocampal volume with the chronicity of depression correlating to a reduction in volume. Although the meaning of these findings is unclear, other studies have shown increased amygdala volume. Studies have found reductions in volume of the frontal cortex, with some studies showing specific reductions in subregions of the frontal cortex, including the orbitofrontal cortex. Findings of an increase in white matter lesions in elderly patients with depression have been replicated and correlated with late-onset depression, as well as impairments in social and cognitive function. These findings point to alterations in a circuit of brain regions hypothesized to include the frontal cortex, hippocampus, amygdala, striatum, and thalamus, that underlie symptoms of depression.     

Use of cue configuration geometry for spatial orientation in human infants (Homo sapiens)

Research with both rats and human infants has found that after inertial disorientation, the geometry of an enclosed environment is used in preference over distinctive featural information during goal localization. Infants (Homo sapiens, 18-24 months) were presented with a toy search task involving inertial disorientation in 1 of 2 conditions. In the identical condition, 4 identical hiding boxes in a rectangular formation were set within a circular enclosure. In the distinctive condition, 4 distinctive hiding boxes were used. Infants searched the goal box and its rotational equivalent significantly more than would be expected by chance in the identical condition, showing that they were sensitive to the geometric configuration of the array of boxes. Unlike the results of studies using a rectangular enclosure, however, in the distinctive condition, infants searched at the correct location significantly more than at other locations.     

The effect of smoothing functions on data obtained from a FFT

This research investigated the effect on power spectra when data-smoothing functions were used on EEG data prior to submitting them to a FFT. We used two smoothing function options: not using any smoothing function and using the Parzen smoothing function. We developed a program to evaluate each of these functions with real and standard data. When a set of data is submitted to smoothing prior to being submitted to a FFT, there are statistically significant differences in the power spectra obtained from the FFT. This finding holds true for standard waveforms as well as for real EEG data.     

Shades of Braitenberg’s Vehicle 5

A model with a hybrid neural network-expert system brain was designed. This model proved to have better memory than that of Braitenberg’s (1984) original simulated vehicles, on which it was based. The parallel nature of the neural network component provided more storage capacity with the same number of neurons, whereas the serial expert system component was able to use the increased memory to make fast, accurate decisions.     

Assessing the simulation of chaotic systems

Three commercially available software packages—BrainMaker, MicroSaint, and Extend—that simulate the function and operation of neural networks were compared on 11 dimensions. Also, a task-oriented analysis was done on the ability of the programs to use a neural network to output a chaotic array generated by the logistic equation. There were differences in the amount of operator overhead among the programs, but the differences in the simulation performance were not considered to be appreciable.     

Comparing two methods of visual abstraction to human data

The ability to “visually abstract” a given pattern with a neural network and abstract the same pattern by using a regression/correlation analysis was investigated. Both methods were compared with human subjects performing the same task. To visually abstract a particular shape, both quantitative methods broke the shape down into its linear, quadratic, and cubic components. Using an IBM-compatible personal computer, 10 test patterns were analyzed with a neural network (designed using Brainmaker Professional and trained with known linear, quadratic, and cubic shapes) and a regression/correlation model (designed using Lotus 1-2-3). The 10 test patterns were also analyzed by 22 human subjects. The neural network data were found to be highly correlated with the human data [r(8) = .90,p < .01]. The regression/correlation model’s data were also found to be significantly correlated with the human data [r(8) = .77,p < .01]. These findings demonstrate the successful modeling of Rumelhart’s (1991) regression/correlation approach to visual abstraction.     

Fourier analyses: A mathematical and geometric explanation

Fourier analyses are used in electrophysiological research to reduce EEG data to an interpretable, analyzable form. This article outlines the mathematical similarities and differences between Fourier transforms and fast Fourier transforms. A geometric explanation of the application of fast Fourier transforms and a Fourier series to theta-band EEG data is also included in this article.     

Place versus response as the basis of spatial errors made by young infants

Nine-month-old infants search successfully for an object which they have seen hidden in one position, but they frequently continue to search for it there after observing it being hidden in a new position. This error can be explained in terms either of egocentric response perseveration or of perseveration to a particular place in space. In order to distinguish between these hypotheses, 80 infants were presented with a problem consisting of several different conditions which separated response, position on a table, and absolute spatial position as factors leading to errors in search for hidden objects. The results strongly support the egocentric response hypothesis. The reason for this response perseveration strategy is discussed in terms of the lack of active experience of spatial displacements among 9-month-old infants.     

Part‐based representations of the body in early childhood: evidence from perceived distortions of tactile space across limb boundaries

Studies show that touch in adults is referenced to a representation of the body that is structured topologically according to body parts; the perceived distance between two stimuli crossing over a body part boundary is elongated relative to the perceived distance between two stimuli presented within one body part category. Here we investigate this influence of body parts on tactile space perception in children of 5, 6 and 7 years of age. We presented children with pairs of tactile stimuli on the left hand/arm, either within the hand, within the forearm, or over the wrist. With their eyes closed children were asked to adjust the distance between the thumb and forefinger of their right hand to represent the felt distance between the two tactile stimuli. Like adults, the children perceived the distance between two stimuli that cross the body part boundary to be further apart than those that were presented within the hand or arm. They also perceive tactile distance to be greater on the hand than the arm which is the first observation of Weber's illusion in young children. We propose that a topological mode of body representation is particularly advantageous during early life given that body part categories remain constant while the metric proportions of the body change substantially as the child grows.     

Heart electrophysiology as a dependent measure in children

This study extends the cardiac component analysis technique, reported by Eddy and his coworkers (Eddy, McKendree, McKenzie, & Bremner, 1982; McKendree, 1982), to children. Three male children between the ages of 8 and 10 years served as subjects and were tested on several days. In particular, the children were taught a simple relaxation task and a simple cognitive task. The cardiac electrophysiology of these children was statistically tested to determine whether there was a reliable difference between psychological tasks but only minimal variance within psychological tasks. The results of testing the ST component of the cardiac electrophysiology confirmed our hypothesis that there is a statistical difference between tasks (p < .001) but not within tasks when tested over time.