Binocular pattern deprivation with delayed onset has impact on motion perception in adulthood.

The quality of motion perception depends on visual input during early development. Even 1month of binocular deprivation (BD) from birth impairs motion coherence thresholds when tested in kittens; conversely BD with a 1-month delayed onset does not impair it (Mitchell et al., 2009). We showed that 6months of BD applied from birth induces a selective impairment in a Global Motion Detection task, but not in global form perception, when tested in adulthood (Burnat et al., 2002, 2005). In these animals cell counts of the retinal motion-sensitive alpha ganglion revealed a life-long increase in OFF-type ganglion cell (Burnat et al., 2012). Here we examined in adult cats the effect of BD on global motion perception using an array of tasks with gradually increasing perceptual difficulty. Two conditions of BD were applied: from birth, lasting for 1, 2, 4 or 6months, and with a delayed onset with first 2months of normal vision followed by 2months of BD. Cats deprived from birth for a 6-month period had Global Motion Detection impaired, as compared to the normal group. Velocity and low contrast-defined motion processing was impaired when BD was applied exclusively in months 3-4 of life. The cats deprived from birth for 1 or 2months were not impaired in any of the tested motion tasks. Motion coherence thresholds, when tested at the end of a long motion training were not affected by BD and did not differ from those obtained for the normal group. Impaired extraction of low contrast-defined motion signal was found in cats deprived solely in months 3-4 of life. Surprisingly, binocular pattern deprivation during the first 2months of life did not weaken motion sensitivity, revealing the occurrence of a critical period for motion perception later in development than previously suggested.

Remapping of the somatosensory cortex after a photothrombotic stroke: dynamics of the compensatory reorganization.

Although stroke can affect cerebral structure and function, the brain has a potential for plasticity thanks to which some degree of function can be restored. The pathways of such recovery are of great interest, since the dynamics of rewiring of the injured brain may become the basis for designing appropriate strategies of rehabilitation. We investigated the spontaneous plasticity of cortical somatosensory representations following a focal unilateral stroke in the barrel cortex of rats. Ischemic lesions were produced with the photothrombotic technique in the cortical representation of vibrissae. Functional activation of the brain in response to the stimulation of vibrissae with destroyed cortical representation was monitored through the 2 months post-stroke survival period with [(14)C] 2-deoxyglucose (2DG) autoradiographic brain mapping (1, 7, 28, 56 days after the stroke). 2DG uptake was measured on autoradiograms of tangential sections in several regions of somatosensory cortex and in motor, auditory and prefrontal cortex. Behavioral deficit was assessed by the gap-crossing test 3, 28, 56 days after the stroke. Changes in the activation pattern of the intact hemisphere and non-vibrissal somatosensory representations of the lesioned hemisphere evolved during the observation period. Full recovery of the behavioral function was reached 2 months after the stroke and at the same time, new foci of activation were observed in the lesioned hemisphere. At that time, hyperactivation of the somatosensory areas in the intact hemisphere subsided. The new activation foci located in representations of anterior vibrissae, front paw and hind paw were specific for the vibrissae stimulation and were most probably a new functional representation of the vibrissae. We demonstrated spatial and temporal remodeling of the brain induced by cortical stroke, leading to vicariation of function.

Laboratory observations of nuptial flights of the ant Polyrhachis laboriosa.

Ethology of Polyrhachis laboriosa, an ant species from equatorial Africa, is little known. No field observation of a nuptial flight of these ants was ever made. We describe two nuptial flights observed in a laboratory colony of P. laboriosa at a 3 days interval. They both occurred in the morning while the nest was kept in near darkness (less than 2 lux of daylight). Flying activity of the alates was suppressed within 1 h by their exposure to daylight of about 140 lux, and within several minutes by their exposure to a lamp emitting white light of 3,000 lux and acting as a source of heat. On the day following the first flight the alates and the workers showed exceptionally high level of mutual grooming. The alates, in particular the males, were transported by workers to the brood chambers whenever they strayed outside and after the nuptial flights.

Direction discrimination learning in normal and visually deprived cats and the effects of lateral suprasylvian lesions.

We used 5 binocularly deprived cats (BD cats), 4 control cats reared also in the laboratory (C cats) and 4 cats reared in a normal environment (N cats). The cats were trained to discriminate an upward or downward-moving light spot versus a stationary spot (detection task) and then an upward versus a downward spot (direction task). The N and C cats learned slowly. The learning was slower than in previously studied discriminations of stationary stimuli. However, all N and C cats mastered the detection task and except one C cat the direction task. In contrast, 4 BD cats failed in the detection task and all in the direction task. This result is consistent with single-cell recording data showing impairment of direction analysis in the visual system in BD cats. After completing the training the upper part of the middle suprasylvian sulcus was removed unilaterally in 7 cats and bilaterally in 6 cats. Surprisingly, the unilateral lesions were more effective: the clear-cut retention deficits were found in 5 cats lesioned unilaterally, whereas only in one cat lesioned bilaterally.