Brain activation during maintenance of standing postures in humans.

1. Luis H. Ospina, MD* 1. *Assistant Professor, Pediatric Ophthalmology and Neuro-ophthalmology, Ste-Justine Hospital, University de Montreal, Montreal, Quebec, Canada After completing this article, readers should be able to: 1. Recognize cortical visual impairment (CVI) as an important cause of pediatric visual loss. 2. Identify the most frequent causes of pediatric CVI and, more specifically, understand the role of hypoxia as a cause of central visual damage. 3. Describe the different patterns and implications for future vision of hypoxic central visual damage occurring in preterm compared with term babies. 4. Know the clinical signs suggestive of CVI in children. 5. Discuss the involvement of visual functions other than visual acuity (ie, cognitive visual aspects) in CVI and correlate them with the likely affected neuroanatomic substrates. 6. Explain the value of using a multidisciplinary approach in rehabilitating children who have CVI early in their development. Vision loss caused by central nervous system damage often is referred to as CVI but also may be referred to as cerebral visual impairment or neurologic visual impairment. These terms refer to the fact that the primary defect may not necessarily be limited to the striate (primary visual) cortex and may affect other areas subserving vision, such as the visual associative cortex, optic radiations, and visual attention pathways. Although it is not yet certain which of these three terms best describes the visual deficit, it is clear that use of the label cortical blindness must be abandoned. That term not only evokes negative connotations for the child and the family but is inaccurate because in almost every instance, some degree of residual vision remains, and visual improvement can occur. CVI has become the greatest cause of pediatric visual impairment in developed countries (1)(2)(3)(4)(5) and is becoming increasingly prevalent in developing nations. CVI is a problem of increasing frequency for two primary reasons. First, the progress in neonatal care has resulted in improved survival of …

The cortico-cortical circuitry of the cross-modal plasticity in the blind

Regulatory focus theory (RFT) postulates two cognitive-motivational systems for personal goal pursuit: the promotion system, which is associated with ideal goals (an individual's hopes, dreams, and aspirations), and the prevention system, which is associated with ought goals (an individual's duties, responsibilities, and obligations). The two systems have been studied extensively in behavioral research with reference to differences between promotion and prevention goal pursuit as well as the consequences of perceived attainment versus nonattainment within each system. However, no study has examined the neural correlates of each combination of goal domain and goal attainment status. We used a rapid masked idiographic goal priming paradigm and functional magnetic resonance imaging to present individually selected promotion and prevention goals, which participants had reported previously that they were close to attaining ("match") or far from attaining ("mismatch"). Across the four priming conditions, significant activations were observed in bilateral insula (Brodmann area (BA) 13) and visual association cortex (BA 18/19). Promotion priming discriminantly engaged left prefrontal cortex (BA 9), whereas prevention priming discriminantly engaged right prefrontal cortex (BA 8/9). Activation in response to promotion goal priming was also correlated with an individual difference measure of perceived success in promotion goal attainment. Our findings extend the construct validity of RFT by showing that the two systems postulated by RFT, under conditions of both attainment and nonattainment, have shared and distinct neural correlates that interface logically with established network models of self-regulatory cognition.

Positron emission tomography was used to measure cerebral activity and to evaluate regional interrelationships within visual cortices and their projections during rapid eye movement (REM) sleep in human subjects. REM sleep was associated with selective activation of extrastriate visual cortices, particularly within the ventral processing stream, and an unexpected attenuation of activity in the primary visual cortex; increases in regional cerebral blood flow in extrastriate areas were significantly correlated with decreases in the striate cortex. Extrastriate activity was also associated with concomitant activation of limbic and paralimbic regions, but with a marked reduction of activity in frontal association areas including lateral orbital and dorsolateral prefrontal cortices. This pattern suggests a model for brain mechanisms subserving REM sleep where visual association cortices and their paralimbic projections may operate as a closed system dissociated from the regions at either end of the visual hierarchy that mediate interactions with the external world.

Objective: To detect the pathogenetic mechanism of motion-sensitive cortical deficit in response to motion stimuli in children with anisometropic amblyopia using a blood oxygenation level-dependent functional magnetic resonance imaging technique (BOLD-fMRI). Methods: This was a case series study. Patients were collected from June to December 2017 at Tianjin Eye Hospital. Twenty-five patients who were diagnosed with anisometropic amblyopia as amblyopia group and twenty-five normal volunteers were examined as control group. A BOLD-fMRI technique on a 1.5T MRI and a horizontally moving sinusoidal grating block design were used for task conditions. All data were processed with SPM5 software, were analyzed by t test. Results: Significant fMRI activation and comparable right and left eye activation were found in the middle temporal area (MT), and Brodmann areas 19 and 37, in all control subjects; Lesser cortical activation in area MT and Brodmann areas 37, 19, and greater activation in the frontal gyrus of the lazy eye group were detected compared to the control group. Lesser cortical activation in Brodmann area 37, 18 of the contralateral eye of the amblyopic group was detected compared to the control group. Lesser cortical activation in area MT and Brodmann areas 19, 18, and greater activation in the frontal lobes of the anisometropic amblyopic eyes were detected compared to the contralateral eyes. Conclusions: The spatial extent and intensity of the visual cortex activation in the visual cortex decreases in the amblyopic eye compared to the normal control. Decreased cortical activation in the fellow eye is prevalent. A greater visual cortex area is activated when stimulating the amblyopic eye. Key words: Anisometropia; amblyopia; magnetic resonance imaging; visual motion; cortical deficit

Preparation for the in vivo recording of neuronal responses in the visual cortex of anaesthetised marmosets ( Callithrix jacchus)

Developmental patterns of acetylcholinesterase (AChE), choline acetyltransferase (CAT) and adenosinetriphosphatase (ATPase) activities were studied in visual centers of normally reared and binocularly deprived cats, from 1 week to 9 months of age. It was found that the activity of these enzymes increased during postnatal development at different rates in various structures. Visual deprivation influenced AChE activity in the lateral geniculate nuclei (LGN) and visual cortex, increasing it by 20 and up to 32%, respectively, but had no effect on the superior colIiculus, visual association cortex and somatosensory cortex. ATPase activity was depressed in the visual cortex of pattern-deprived cats. Visual deprivation had no effect on CAT activity and protein content in the investigated structures.

Spatiotemporal response properties of cerebellar Purkinje cells to animal displacement: a population analysis

Developing optogenetic methods for research in non-human primates (NHP) is important for translational neuroscience and for delineating brain function with unprecedented specificity. Here we assess, in macaque monkeys, the selectivity by which optogenetic stimulation of the primary visual cortex (V1) drives the local laminar and widespread cortical connectivity related to visual perception. Towards this end, we transfected neurons with light-sensitive channelrhodopsin in dorsal V1. fMRI revealed that optogenetic stimulation of V1 using blue light at 40Hz increased functional activity in the visual association cortex, including areas V2/V3, V4, motion-sensitive area MT and frontal eye fields, although nonspecific heating and eye movement contributions to this effect could not be ruled out. Neurophysiology and immunohistochemistry analyses confirmed optogenetic modulation of spiking activity and opsin expression with the strongest expression in layer 4-B in V1. Stimulating this pathway during a perceptual decision task effectively elicited a phosphene percept in the receptive field of the stimulated neurons in one monkey. Taken together, our findings demonstrate the great potential of optogenetic methods to drive the large-scale cortical circuits of the primate brain with high functional and spatial specificity.

The cortical topography of temporal lobe hypometabolism in early Alzheimer's disease

Background: Fisher syndrome (FS) is characterised by a triad of ophthalmoplegia, ataxia and areflexia. The lesion sites responsible for ataxia and ophthalmoplegia in FS require further exploration. The aim of...

Reward modulation of prefrontal and visual association cortex during an incentive working memory task

The primary visual cortex, Brodmann's area (BA 17), plays a vital role in basic survival mechanisms in humans. In most neuro-imaging studies in which the volunteers have to watch pictures or movies, the primary visual cortex is similarly activated independent of the content of the pictures or movies. However, in case the volunteers perform demanding non-visual tasks, the primary visual cortex becomes de-activated, although the amount of incoming visual sensory information is the same. Do low- and high-intensity erotic movies, compared to neutral movies, produce similar de-activation of the primary visual cortex? Brain activation/de-activation was studied by Positron Emission Tomography scanning of the brains of 12 healthy heterosexual premenopausal women, aged 18-47, who watched neutral, low- and high-intensity erotic film segments. We measured differences in regional cerebral blood flow (rCBF) in the primary visual cortex during watching neutral, low-intensity erotic, and high-intensity erotic film segments. Watching high-intensity erotic, but not low-intensity erotic movies, compared to neutral movies resulted in strong de-activation of the primary (BA 17) and adjoining parts of the secondary visual cortex. The strong de-activation during watching high-intensity erotic film might represent compensation for the increased blood supply in the brain regions involved in sexual arousal, also because high-intensity erotic movies do not require precise scanning of the visual field, because the impact is clear to the observer.

Cerebellar vermis abnormalities and cognitive functions in individuals with Williams syndrome

Neurovascular coupling is the generic term for changes in cerebral metabolic rate of oxygen (CMRO 2), cerebral blood flow, and cerebral blood volume related to brain activity. The goal of this paper is to better understand the effects of neurovascular coupling in the visual and motor cortices using frequency-domain near-infrared spectroscopy. Maps of concentration changes in oxyhemoglobin [O 2Hb], deoxyhemoglobin [HHb], and total hemoglobin of the visual and motor cortices were generated during stimulation using a reversing checkerboard screen and palm-squeezing, respectively. Seven healthy volunteers of 18–37 years of age were included. In the visual cortex the patterns of [O 2Hb] and [HHb] were strongly linearly correlated ( r 2 > 0.8 in 13 of a total of 24 locations). In 20 locations the change in [O 2Hb] was larger than 0.25 μM. The mean slope of the linear regression between [O 2Hb] and [HHb] was −3.93 ± 0.31 (SE). The patterns of the [O 2Hb] and [HHb] traces over the motor cortex looked different. The [O 2Hb] reached its maximum change a few seconds before the [HHb] reached its minimum. This was confirmed by the linear regression analysis ( r 2 > 0.8 in none of 40 locations). In 20 locations the change in [O 2Hb] was larger than 0.25 μM. The mean slope of the regression line was −1.76 ± 0.20, which is significantly higher than that in the motor cortex ( P < 0.0000001). Patterns of [O 2Hb] and [HHb] differ among cortex areas. This implies that the regulation of perfusion in the visual cortex is different from that in the motor cortex. There is evidence that the CMRO 2 increases substantially in the visual cortex, while this is not the case for the motor cortex.