Identification of a Novel PROP1 Mutation in a Patient with Combined Pituitary Hormone Deficiency and Enlarged Pituitary.

Growth hormone deficiency (GHD) can be present from the neonatal period to adulthood and can be the result of congenital or acquired insults. In addition, GHD can be classified into two types: isolated growth hormone deficiency (IGHD) and combined pituitary hormone deficiency (CPHD). CPHD is a disorder characterized by impaired production of two or more anterior and/or posterior pituitary hormones. Many genes implicated in CPHD remain to be identified. Better genetic characterization will provide more information about the disorder and result in important genetic counselling because a number of patients with hypopituitarism represent familial cases. To date, PROP1 mutations represent the most common known genetic cause of CPHD both in sporadic and familial cases. We report a novel mutation in the PROP1 gene in an infant with CPHD and an enlarged pituitary gland. Close long-term follow-up will reveal other possible hormonal defects and pituitary involution.

Spatiotemporal dynamics of perisaccadic remapping in humans revealed by classification images.

We actively scan our environment with fast ballistic movements called saccades, which create large and rapid displacements of the image on the retina. At the time of saccades, vision becomes transiently distorted in many ways: Briefly flashed stimuli are displaced in space and in time, and spatial and temporal intervals appear compressed. Here we apply the psychophysical technique of classification images to study the spatiotemporal dynamics of visual mechanisms during saccades. We show that saccades cause gross distortions of the classification images. Before the onset of saccadic eye movements, the positive lobes of the images become enlarged in both space and in time and also shifted in a systematic manner toward the pre-saccadic fixation (in space) and anticipated in time by about 50 ms. The transient reorganization creates a spatiotemporal organization oriented in the direction of saccadic-induced motion at the time of saccades, providing a potential mechanism for integrating stimuli across saccades, facilitating stable and continuous vision in the face of constant eye movements.

Acoustic cues to visual detection: a classification image study.

A non-informative sound is known to improve contrast detection thresholds for a synchronous visual target (M. Lippert, N. K. Logothetis, & C. Kayser, 2007). We investigated the spatio-temporal characteristics of the mechanisms underlying this crossmodal effect by using a classification image paradigm specifically suited to investigate perceptual templates across both space and time (P. Neri & D. J. Heeger, 2002). A bright bar was embedded in 2D (space-time) dynamic noise and observers were asked to detect its presence in both unimodal (only visual) and bimodal (audio-visual) conditions. Classification image analysis was performed and the 1st and 2nd order kernels were derived. Our results show that the cross-modal facilitation of detection consists in a reduction of activity of the early mechanisms elicited by the onset of the stimulation and not directly involved in the identification of the target. In fact, the sound sharpens the 2nd order kernels (involved in target detection) by suppressing the activation preceding the target, whereas it does not influence the 1st order kernels. These data suggest that the sound affects some non-linear process involved with the detection of a visual stimulus by, decreasing the activity of contrast energy filters temporally uncorrelated with the target, hence reducing temporal uncertainty.