John D. Pettigrew

Learn More
1. Binocularly driven units were investigated in the cat's primary visual cortex.2. It was found that a stimulus located correctly in the visual fields of both eyes was more effective in driving the units than a monocular stimulus, and much more effective than a binocular stimulus which was correctly positioned in only one eye: the response to the correctly(More)
We have estimated the total number, distribution and peak density of retinal ganglion cells (RGCs) in retinal wholemounts of several species of microchiropteran (echolocating) bats. The estimates are based on counts of Nissl-stained, presumed RGCs. The total number of presumed RGCs varies among the species: from about 4,500 in Rhinolophus rouxi to about(More)
The visual capacity of the common barn owl (Tyto alba) was studied by quantitative analysis of the retina and optic nerve. Cell counts in the ganglion cell layer of the whole-mounted retina revealed a temporal area centralis with peak cell density of 12,500 cells/mm2 and a horizontal streak of high cell density extending from the area centralis into the(More)
Despite years of research into bipolar disorder (manic depression), its underlying pathophysiology remains elusive. It is widely acknowledged that the disorder is strongly heritable, but the genetics are complex with less than full concordance in monozygotic twins and at least four susceptibility loci identified. We propose that bipolar disorder is the(More)
A diverse range of retinal specializations are examined in twelve species of reef teleosts and estimates of the spatial resolution of neurons within the ganglion cell layer calculated using Matthiessen's ratio. Upper limits of between 4 and 27 cycles per degree were found to facilitate acute vision into frontal and eccentric space, utilizing temporal and(More)
The visual response properties of single neurons in the owl's visual Wulst suggest that this forebrain structure is an analog of the mammalian visual cortex. Features in common with the cat and the monkey visual cortex include a precise topographic organization, a high degree of binocular interaction, and selectivity for orientation, direction of movement,(More)
The retinal ganglion cell layer of five species of teleosts has been studied from Nissl-stained whole-mounts and the distribution of neuronal elements determined quantitatively. Isodensity contour maps of neurons in the ganglion cell layer revealed areas of high density (areae centrales) predominantly in the temporal retina, but other areae were also found(More)
Single neurons recorded from the owl's visual Wulst are surprisingly similar to those found in mammalian striate cortex. The receptive fields of Wulst neurons are elaborated, in an apparently hierarchical fashion, from those of their monocular, concentrically organized inputs to produce binocular interneurons with increasingly sophisticated requirements for(More)
We examine the paraphylectic hypothesis of bat origins, both in the light of previous discussions, and in the light of new evidence from our analyses of neurological traits and wing morphology. Megabats share with primates a variety of complex details in the organization of neural pathways that have not been found in any other mammalian group, particularly(More)