John A.W. Kirsch

Phylogeny through Brain Traits: The Distribution of Categorizing Characters in Contemporary Mammals

The varying states of 15 characters of the central neural organization are tabulated as they occur in each of 147 mammalian species. For each character and species, scores are entered designating the primitive or derived state of the character as it is observed in that species. This tabulation provides data in numerically ordered form for multiple analyses of possible phylogenetic relationships which take into account variations in several different characters simultaneously.

Phylogeny through Brain Traits: The Mammalian Family Tree

Wagner trees based on the analysis of 15 brain characters scored on 154 specimens of 134 mammalian species show consistent patterns of relationship among the taxa, i.e. (1) monotremes are the primitive complement of the group uniting marsupials and placentals; (2) among marsupials, diprotodont Australian forms are more derived; (3) placental mammals divide into two groups of orders, roughly the ferungulates (carnivores, ungulates, and subungulates) and the unguiculates-plus-gliroids (chiropterans, dermopterans, lagomorphs, rodents, primates, and insectivores including elephant shrews); (4) edentates sit at the base of or just before the placental dichotomy; (5) the tree shrew and tarsier show the same pattern of distribution of brain traits as some rodents, as do prosimians and New World monkeys.

Phylogeny through Brain Traits: Fifteen Characters Which Adumbrate Mammalian Genealogy

Fifteen characters of brain organization are identified for which primitive and derived states can be distinguished, and which are thus useful in reconstructing mammalian phylogeny. The states of the characters are numerically coded in sequence from most primitive to most derived, to facilitate reciprocal comparisons in comprehensive genealogical analyses. The characters include certain features of cerebral circulation, cytoarchitecture, fiber pathways, and sensory projections. Seven characters are shared with nonmammals, a fact which makes then particularly useful for establishing their primitive vs. derived states; the other eight characters are features peculiar to mammals. Ten characters provide impressive reinforcement for traditional major grouping of the species, while five provide bases for new ideas about mammalian relationships.

Phylogeny through brain traits: Relation of lateral olfactory tract fibers to the accessory olfactory formation as a palimpsest of mammalian descent

In mammals the fibers of the dorsal lateral olfactory tract either pass under the accessory olfactory formation, or they penetrate through it separating the internal granule cells from the output cells. The use of this trait as a phylogenetic indicator in 181 specimens representing 131 species of 16 orders yielded evidence for common ancestry of Insectivora, Chiroptera, Dermoptera, Rodentia, and Primates (including Tupaia), since all share the derived trait, their dorsal lateral olfactory tract fibers passing through the accessory olfactory formation. Carnivora (including Pinnipedia), Hyracoidea, Perissodactyla, and most Artiodactyla share the primitive condition (fibers passing under) with the one order of monotremes and three marsupial orders. The Edentata and Lagomorpha may be separate from the two major placental groups and from each other, or they may represent successive stages in the evolution of the derived state through progressive alterations in the relative chronology of development of olfactory system components, or one or both orders may occupy an ancestral position with respect to the dichotomy within placental mammals.

Phylogeny through Brain Traits: Objectives and Method

Principles of phylogenetic reconstruction are reviewed and the Wagner algorithm for building trees from many characters simultaneously is described. An example worked by hand is presented using five b

RF-induced heating in tissue near bilateral DBS implants during MRI at 1.5 T and 3T: The role of surgical lead management

&NA; Access to MRI is limited for patients with deep brain stimulation (DBS) implants due to safety hazards, including radiofrequency (RF) heating of tissue surrounding the leads. Computational models provide an exquisite tool to explore the multi‐variate problem of RF heating and help better understand the interaction of electromagnetic fields and biological tissues. This paper presents a computational approach to assess RF‐induced heating, in terms of specific absorption rate (SAR) in the tissue, around the tip of bilateral DBS leads during MRI at 64MHz/1.5 T and 127 MHz/3T. Patient‐specific realistic lead models were constructed from post‐operative CT images of nine patients operated for sub‐thalamic nucleus DBS. Finite element method was applied to calculate the SAR at the tip of left and right DBS contact electrodes. Both transmit head coils and transmit body coils were analyzed. We found a substantial difference between the SAR and temperature rise at the tip of right and left DBS leads, with the lead contralateral to the implanted pulse generator (IPG) exhibiting up to 7 times higher SAR in simulations, and up to 10 times higher temperature rise during measurements. The orientation of incident electric field with respect to lead trajectories was explored and a metric to predict local SAR amplification was introduced. Modification of the lead trajectory was shown to substantially reduce the heating in phantom experiments using both conductive wires and commercially available DBS leads. Finally, the surgical feasibility of implementing the modified trajectories was demonstrated in a patient operated for bilateral DBS. HighlightsAccess to MRI is limited for patients with DBS implants due to safety hazards, including radiofrequency heating of tissue surrounding the leads.Computational models provide an exquisite tool to explore the multi‐variate problem of RF implant heating.We used a computational approach to assess RF heating around tips of bilateral DBS leads during MRI at 1.5T and 3T using realistic DBS lead models.A substantial difference was found between the SAR and temperature rise at the tip of right and left DBS leads.Modification of DBS lead trajectory reduced heating in phantom experiments using both conductive wires and commercially available DBS leads.