Subcortical Anatomy Research Articles

A locus-driven mechanism for rapid and automated atlas-assisted analysis of functional images by using the Brain Atlas for Functional Imaging.

Functional imaging is an established neurosurgical modality for studying the brain in health and disease. Identifying numerous activation loci on many functional images and reading their underlying cortical and subcortical anatomy, coordinates, and anatomical and functional values is a tedious, time-consuming, and error-prone task. In this study the authors propose a novel approach to this problem by using an electronic brain atlas in conjunction with a locus-driven mechanism. The Brain Atlas for Functional Imaging containing an enhanced and extended electronic version of the Talairach-Tournoux brain atlas was used for analysis. It enables loading of anatomical and functional data, correlation of these data, identification of activation loci, and their labeling with Brodmann areas, gyri, and subcortical structures by means of the atlas. The Talairach proportional grid system transformation is used to register the anatomical and functional data with the atlas. The availability of numerous tools supports this process. A locus-driven mechanism for analysis of activation loci is implemented. Locus placement within the activation region is supported by thresholding, and its location can be further edited in three dimensions on any orthogonal plane. Once all loci are identified and edited, their labels, coordinates, and anatomical/functional values are read automatically and saved in an external file. This mechanism enables the analysis to be performed in an automated, rapid, explicit, three-dimensionally consistent, and user-friendly way. The electronic brain atlas with locus-driven mechanism is a useful tool for localization analysis of functional images.

An automated method for neuroanatomic and cytoarchitectonic atlas-based interrogation of fMRI data sets

Analysis and interpretation of functional MRI (fMRI) data have traditionally been based on identifying areas of significance on a thresholded statistical map of the entire imaged brain volume. This form of analysis can be likened to a “fishing expedition.” As we become more knowledgeable about the structure–function relationships of different brain regions, tools for a priori hypothesis testing are needed. These tools must be able to generate region of interest masks for a priori hypothesis testing consistently and with minimal effort. Current tools that generate region of interest masks required for a priori hypothesis testing can be time-consuming and are often laboratory specific. In this paper we demonstrate a method of hypothesis-driven data analysis using an automated atlas-based masking technique. We provide a powerful method of probing fMRI data using automatically generated masks based on lobar anatomy, cortical and subcortical anatomy, and Brodmann areas. Hemisphere, lobar, anatomic label, tissue type, and Brodmann area atlases were generated in MNI space based on the Talairach Daemon. Additionally, we interfaced these multivolume atlases to a widely used fMRI software package, SPM99, and demonstrate the use of the atlas tool with representative fMRI data. This tool represents a necessary evolution in fMRI data analysis for testing of more spatially complex hypotheses.

The subcortical anatomy of human spatial neglect: putamen, caudate nucleus and pulvinar.

Various studies have documented that right hemispheric lesions restricted to the basal ganglia or to the thalamus may evoke spatial neglect. However, for methodological reasons, the exact anatomical correlate of spatial neglect within these two subcortical structures still remained uncertain. The present study identified these locations by comparing the anatomy of subcortical lesions to the basal ganglia or thalamus between neglect and control patients. Analysis revealed that the putamen, the pulvinar and, to a smaller degree, the caudate nucleus are the subcortical structures typically associated with spatial neglect in humans. All these structures have direct anatomical connections to the superior temporal gyrus (STG), which recently has been identified as the neural correlate of spatial neglect in the human cortex. Therefore, it is assumed that the right putamen, caudate nucleus, pulvinar and STG form a coherent corticosubcortical anatomical network in the genesis of spatial neglect in humans.

Complex sensory-motor sequence learning based on recurrent state representation and reinforcement learning

A novel neural network model is presented that learns by trial-and-error to reproduce complex sensory-motor sequences. One subnetwork, corresponding to the prefrontal cortex (PFC), is responsible for generating unique patterns of activity that represent the continuous state of sequence execution. A second subnetwork, corresponding to the striatum, associates these state-encoding patterns with the correct response at each point in the sequence execution. From a neuroscience perspective, the model is based on the known cortical and subcortical anatomy of the primate oculomotor system. From a theoretical perspective, the architecture is similar to that of a finite automaton in which outputs and state transitions are generated as a function of inputs and the current state. Simulation results for complex sequence reproduction and sequence discrimination are presented.

Prefrontal-Limbic Epilepsy

Nonconvulsive seizures from prefrontal cortex in humans cause complex behavioral, motor, and autonomic manifestations. In order to gain insight into the possible anatomical basis of these phenomena, we have studied experimental seizures from medial and lateral prefrontal-limbic cortex and the amygdaloid complex in rat. Small injections of penicillin or electrical stimulation were used to induce seizures, and the [14C]deoxyglucose technique was employed to map pathways of seizure spread. Analysis of results indicates that prefrontal-limbic cortex and amygdala exhibit strong bilateral reciprocal interaction. Mild seizures from these different areas activated both unique and similar pathways and targets. With increasing strength of discharge from these areas, there was a convergence of the subcortical pattern of activation in medial and midline thalamic nuclei and bilateral substantia nigra. These studies suggest that complex epileptic phenomena in humans evoked from a prefrontal seizure focus relate to activation of cortical and subcortical functional limbic anatomy.

Environmental complexity modulates growth of granule cell dendrites in developing but not adult hippocampus of rats

The dendritic fields of hippocampal dentate gyrus granule cells were studied in Golgi-stained brains of rats placed in complex or isolated environments for 4 weeks after weaning or for 12 weeks in adulthood (beginning at 145 days of age). Rats placed in the complex environment at weaning had more lower-order dendritic branching by two measures and wider dendritic fields compared to rats reared in isolation. Rats reared socially and placed as adults in complex or isolated environments did not differ on any granule cell measures. The results are compatible with reports of the behavioral effects of environmental complexity, with prior studies of rearing complexity effects upon subcortical anatomy and chemistry, and with studies of hippocampal development, and they suggest a possible sensitive period for the effects of rearing complexity upon hippocampal dentrate gyrus organization.