Dorsal and ventral mossy cells differ in their long-range axonal projections throughout the dentate gyrus of the mouse hippocampus

ABSTRACTGlutamatergic hilar mossy cells (MCs) have axons that terminate both near and far from their cell body but stay within the DG, making synapses in the inner molecular layer primarily. The long-range axons are considered the primary projection, and extend throughout the DG ipsilateral to the soma, and project to the contralateral DG. The specificity of long-range MC axons for the inner molecular layer (IML) has been considered to be a key characteristic of the DG. In the present study we made the surprising finding that dorsal MC axons are an exception to this rule. We used two mouse lines that allow for Cre-dependent viral labeling of MCs and their axons: dopamine receptor d2 (Drd2-Cre) and calcitonin receptor-like receptor (Crlr-Cre). A single viral injection into the dorsal DG to label dorsal MCs resulted in labeling of MC axons in both the IML and middle molecular layer (MML). Interestingly, this broad termination of MC axons applied to all long-range axons. In contrast, long-range axons of ventral MCs mainly terminated in the IML, consistent with the literature. Taken together, these results suggest that dorsal and ventral MCs differ significantly in their axonal projections, and the difference is primarily in their long-range projections. Since those projections are thought to terminate primarily on GCs, the results suggest a dorsal-ventral difference in MC activation of GCs. The surprising difference in dorsal and ventral MC projections should therefore be considered when evaluating dorsal-ventral differences in DG function.

A View from the Beginning of Magnetoencephalography

This chapter examines the author’s work on visually evoked field (VEF) experiments. After their first VEF experiment, the author and other researchers thought that it may well be possible to use magnetoencephalography (MEG) to noninvasively map primary projection areas of several sensory pathways on the cerebral cortex. The importance of such a task lay partly in the fact that an enormous amount of information about these areas already existed. This information was gained in part by studying patients with penetrating wounds of their brains. Other studies applied electric stimuli during brain surgery to exposed brain tissue. Even if the researchers could not add anything of value to this knowledge base, they may still be able to verify MEG’s ostensible potential for locating specific functional areas noninvasively. Ultimately, this became one of the more valuable potential applications before brain surgery. The chapter then suggests some research projects that may accelerate progress in MEG.

A new genus of Theraphosid spider from Mexico, with a particular palpal bulb structure (Araneae, Theraphosidae, Theraphosinae)

Magnacarina gen. nov. from Mexico is described. Hapalopus aldanus West, 2000 from Nayarit, is transferred to the new genus with an emended diagnosis creating the new combination Magnacarina aldana comb. nov. Three new species are described: Magnacarina moderata Locht, Mendoza & Medina sp. nov. from Nayarit and Sinaloa; Magnacarina primaverensis Mendoza & Locht sp. nov. and Magnacarina cancer Mendoza & Locht sp. nov., both from Jalisco. Magnacarina gen. nov. is characterized by an unusual bifid palpal bulb, and has a primary projection located in the central area of the palpal bulb and directed retrolaterally; this projection possesses the prolateral superior and retrolateral keels. Next to the primary projection is a secondary projection, which may be short or long, ending in the prolateral inferior and apical keel surrounding the sperm pore. This secondary projection may have prolateral accessory keels and is diagnosed by possessing a nodule of inwardly curled megaspines, located in the basal ventro-retrolateral region of metatarsi I in adult males. Additionally, male tibiae I possess three apophyses. Females of Magnacarina gen. nov. have a single reduced and strongly sclerotized spermatheca, with an apical lobe projecting ventrally, and with a uterus externus that is longer and wider than the spermatheca.

An overlooked threatened species of eagle: Legge's Hawk Eagle Nisaetus kelaarti (Aves: Accipitriformes)

Species delimitation is fundamental to many areas of biology, and in cases where taxonomic status has not been sufficiently clarified the ramifications can be as serious as extinction due to the failure to implement conservation measures. Since 1931, the Mountain Hawk Eagle Nisaetus (Spizaetus) nipalensis Hodgson has included the allopatric Sri Lankan and southern Indian taxon N. kelaarti (Legge) as a subspecies, and its taxonomic status has not been re-evaluated. We found that N. kelaarti differs considerably from N. nipalensis in its relatively much larger bill and claws and short primary projection, and that it also differs consistently in numerous plumage characters and other mensural characters. Its vocalizations differ distinctly, and an earlier study found a moderate degree of genetic differentiation (4.4% in cyt b and 3.1% in CR) from N. nipalensis. The available evidence thus strongly and unambiguously supports the specific distinctness of N. kelaarti.

Man's Triune Conscious Mind

In a previously presented perceptual model perception was assumed to be the result of two separate but coupled modes of consciousness, one sensory-based or outer and one memory-based or inner. Evidence was found for the assumption that the outer mode of consciousness is related to the primary projection areas of the sensory cortices. In the present paper the perceptual model is further integrated with the cognitive system while considering neuropsychological aspects. The two perceptual modes of consciousness, and one mode related to the experience of feelings, are considered to be the conscious outlets of three functionally and physiologically distinguishable minds which cooperate or compete in the control of man's behavior.