An investigation of the white matter microstructure in motion detection using diffusion MRI.

One of the most widely investigated functions of the brain is vision. Whereas special attention is often paid to motion detection and its modulation by attention, comparatively still little is known about the structural background of this function. We therefore, examined the white matter microstructural background of coherent motion detection. A random-dot kinematogram paradigm was used to measure the sensitivity of healthy individuals׳ to movement coherence. The potential correlation was investigated between the motion detection threshold and the white matter microstructure as measured by high angular resolution diffusion MRI. The Track Based Spatial Statistics method was used to address this correlation and probabilistic tractography to reveal the connection between identified regions. A significant positive correlation was found between the behavioural data and the local fractional anisotropy in the posterior part of the right superior frontal gyrus, the right juxta-cortical superior parietal lobule, the left parietal white matter, the left superior temporal gyrus and the left optic radiation. Probabilistic tractography identified pathways that are highly similar to the segregated attention networks, which have a crucial role in the paradigm. This study draws attention to the structural determinant of a behavioural function.

Delayed development of visual motion processing in childhood migraine.

INTRODUCTION: Altered visual processing has been observed in adult migraineurs. But because visual processing has not been studied in paediatric cases, it is not known whether such visual system alterations are already present in early development. We therefore used a dynamic visual task to investigate motion detection threshold in paediatric migraine. METHODS: Fourteen migraineurs and 21 controls participated in the study (age range: 8-17 years). The minimal percentage of coherently moving dot stimuli at which subjects were still able to detect coherent movement (absolute threshold) was determined using a random dot kinematogram paradigm. RESULTS: Motion coherence detection threshold was higher in migraineurs (p < 0.05). This difference between groups was more pronounced at younger ages, but migraineurs seem to catch up with healthy controls over the years. CONCLUSIONS: Children with migraine exhibit a delayed development of visual motion processing. This might be a useful supplementary biomarker in paediatric migraine.

Visual stimulation synchronizes or desynchronizes the activity of neuron pairs between the caudate nucleus and the posterior thalamus.

Recent morphological and physiological studies have suggested a strong relationship between the suprageniculate nucleus (Sg) of the posterior thalamus and the input structure of the basal ganglia, the caudate nucleus (CN) of the feline brain. Accordingly, to clarify if there is a real functional relationship between Sg and CN during visual information processing, we investigated the temporal relations of simultaneously recorded neuronal spike trains of these two structures, looking for any significant cross-correlation between the spiking of the simultaneously recorded neurons. For the purposes of statistical analysis, we used the shuffle and jittering resampling methods. Of the recorded 288 Sg-CN neuron pairs, 26 (9.2%) showed significantly correlated spontaneous activity. Nineteen pairs (6.7%) showed correlated activity during stationary visual stimulation, while 21 (7.4%) pairs during stimulus movement. There was no overlap between the neuron pairs that showed cross-correlated spontaneous activity and the pairs that synchronized their activity during visual stimulation. Thus visual stimulation seems to have been able to synchronize, and also, by other neuron pairs, desynchronize the activity of CN and Sg. In about half of the cases, the activation of Sg preceded the activation of CN by a few milliseconds, while in the other half, CN was activated earlier. Our results provide the first piece of evidence for the existence of a functional cooperation between Sg and CN. We argue that either a monosynaptic bidirectional direct connection should exist between these structures, or a common input comprising of parallel pathways synchronizing them.

Development of visual contour integration in children with migraine without aura.

INTRODUCTION: As migraine attacks pose insult to cerebral circulation and ion homeostasis, migraine has the potential to interfere with the development of different brain structures, producing functional deficits. It is known that visual contour integration (CI) is a function with a protracted development. Therefore, we sought to establish whether migraine interferes with its development. METHODS: Forty-eight migraineurs (without aura) and 48 age- and sex-matched controls participated in the study, divided into three cohorts by age. Stimuli were presented on cards with a contour consisting of Gabor patches embedded in random noise. Difficulty was varied by the manipulation of relative noise density. The task was to identify and show the contour. RESULTS: A significant difference was found between the performance of migraineurs and controls in the 10-14-year-old and 15-18-year-old cohorts (p < 0.05). Development between all three cohorts was significant in the control group (p < 0.017), while it was not significant in migraineurs between 6 and 14 years. Correlation between age and CI threshold was stronger in controls than in migraineurs. CONCLUSION: Children with paediatric migraine exhibited a less marked development in the Gabor patch-based CI task.

Is the development of visual contrast sensitivity impaired in children with migraine? An exploratory study.

INTRODUCTION: Impairment of visual contrast sensitivity is a well-known phenomenon in adult migraineurs. Little is known, however, about whether contrast sensitivity deficits are already present in children with migraine. METHODS: We conducted an exploratory study with 18 children with migraine without aura, in which we tested our subjects' visual contrast sensitivity. Eighteen age- and sex-matched healthy children served as controls. RESULTS: Among the youngest subjects (6-10 years) we found no significant differences at any of the spatial frequencies tested, as compared to the controls, whereas from the age of 10 on, migraineurs exhibited significantly poorer contrast sensitivity, especially at the lower spatial frequencies. CONCLUSION: To our knowledge, we are the first to report on such a deficit in children, and we conclude that our findings might be interpreted as reflecting an increased vulnerability of the visual system to migraine attacks as part of the migrainous endophenotype.

Parallel development of contour integration and visual contrast sensitivity at low spatial frequencies.

It has been suggested that visual contrast sensitivity and contour integration functions exhibit a late maturation during adolescence. However, the relationship between these functions has not been investigated. The aim of this study was to assess the development of visual contrast sensitivity and contour integration in 152 healthy volunteers aged between 5 and 30 years. The results revealed a significant maturation of contrast sensitivity at low spatial frequencies (0.5, 1.2, and 1.9 cycles/degree) and contour integration. The largest developmental step was observed for both contrast sensitivity and contour integration tasks when the 5-8-year olds were compared with the 9-11-year olds. There was a significant correlation between the development of low spatial frequency contrast sensitivity and contour integration. These results raise the possibility that the development of low spatial frequency processing may affect attentional mechanisms, which may have an impact on early contour integration.

Visual pathways serving motion detection in the mammalian brain.

Motion perception is the process through which one gathers information on the dynamic visual world, in terms of the speed and movement direction of its elements. Motion sensation takes place from the retinal light sensitive elements, through the visual thalamus, the primary and higher visual cortices. In the present review we aim to focus on the extrageniculo-extrastriate cortical and subcortical visual structures of the feline and macaque brain and discuss their functional role in visual motion perception. Special attention is paid to the ascending tectofugal system that may serve for detection of the visual environment during self-motion.