Lack of early pattern stimulation prevents normal development of the alpha (Y) retinal ganglion cell population in the cat.

Binocular deprivation of pattern vision (BD) early in life permanently impairs global motion perception. With the SMI-32 antibody against neurofilament protein (NFP) as a marker of the motion-sensitive Y-cell pathway (Van der Gucht et al. [2001] Cereb. Cortex 17:2805-2819), we analyzed the impact of early BD on the retinal circuitry in adult, perceptually characterized cats (Burnat et al. [2005] Neuroreport 16:751-754). In controls, large retinal ganglion cells exhibited a strong NFP signal in the soma and in the proximal parts of the dendritic arbors. The NFP-immunoreactive dendrites typically branched into sublamina a of the inner plexiform layer (IPL), i.e., the OFF inner plexiform sublamina. In the retina of adult BD cats, however, most of the NFP-immunoreactive ganglion cell dendrites branched throughout the entire IPL. The NFP-immunoreactive cell bodies were less regularly distributed, often appeared in pairs, and had a significantly larger diameter compared with NFP-expressing cells in control retinas. These remarkable differences in the immunoreactivity pattern were typically observed in temporal retina. In conclusion, we show that the anatomical organization typical of premature Y-type retinal ganglion cells persists into adulthood even if normal visual experience follows for years upon an initial 6-month period of BD. Binocular pattern deprivation possibly induces a lifelong OFF functional domination, normally apparent only during development, putting early high-quality vision forward as a premise for proper ON-OFF pathway segregation. These new observations for pattern-deprived animals provide an anatomical basis for the well-described motion perception deficits in congenital cataract patients.

Cytoarchitecture of the mouse neocortex revealed by the low-molecular-weight neurofilament protein subunit.

The expression patterns of the medium- and high-molecular-weight subunits of the neurofilament protein triplet have been extensively studied in several neuroanatomical studies. In the present study, we report the use of the low-molecular-weight neurofilament protein subunit (NF-L) as a reliable marker within the neurofilament protein family to reveal the regional architecture of mammalian neocortex. We document clearly its usefulness in anatomical parcellation studies and report unique expression patterns of NF-L throughout the mouse neocortex. NF-L was most abundant in the somatosensory cortex, the lateral secondary visual area, the granular insular cortex, and the motor cortex. Low NF-L staining intensity was observed in the agranular insular cortex, the prelimbic and infralimbic cortex, the anterior cingulate cortex, the visual rostromedial areas, the temporal association cortex, the ectorhinal cortex, and the lateral entorhinal cortex. NF-L immunoreactivity was present in the perikarya, dendrites, and proximal segment of axons primarily of pyramidal neurons, and was mainly located in layers II and III, and to a lesser extent in layers V and VI. Interestingly, Black-Gold myelin staining confirmed a close correlation between NF-L immunoreactivity and myelination patterns. The characteristic and distinctive distribution and laminar expression profiles of NF-L make it an excellent tool to assess accurately topographical boundaries among neocortical areas as illustrated herein in the adult mouse brain.

A claim in search of evidence: reply to Manger's thermogenesis hypothesis of cetacean brain structure.

In a recent publication in Biological Reviews, Manger (2006) made the controversial claim that the large brains of cetaceans evolved to generate heat during oceanic cooling in the Oligocene epoch and not, as is the currently accepted view, as a basis for an increase in cognitive or information-processing capabilities in response to ecological or social pressures. Manger further argued that dolphins and other cetaceans are considerably less intelligent than generally thought. In this review we challenge Manger's arguments and provide abundant evidence that modern cetacean brains are large in order to support complex cognitive abilities driven by social and ecological forces.