Computer-aided two-dimensional high-resolution axon tracing: an application using the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHAL)

A computer-aided method for mapping the spatial distribution of axons labeled with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHAL) has been devised. The method is based upon a histochemical charting system that controls a motorized microscope stage. The Computerized Charting System (CCS) does not require a camera lucida and can be installed on a common laboratory computer with minimal specialized hardware. The system provides features for storing, manipulating, and plotting the data, and recording the location of photographic images. The CCS has been used in our laboratory for: (1) the analysis of retrograde and anterograde neuroanatomical tract tracing using horseradish peroxidase, fluorescent dyes, PHAL, and ³H-labeled amino acids; (2) mapping the distribution of cells identified by immunohistochemistry; (3) mapping the distribution of silver grain-positive cells using in situ hybridization; (4) mapping the spatial distribution of neurofibrillary tangles and neuritic plaques in Alzheimer's disease; and (5) mapping the pattern of congophilic angiopathy in human brain. With the addition of high-resolution tracing features, the CCS provides a cost-effective and comprehensive alternative to the tedious and often inaccurate X-Y recording techniques used routinely in neuroanatomy and neuropathology.