Vědecké spisy Vysokého učení technického v Brně. PhD Thesis ; sv. 20
31 s. : grafy ; 22 cm
Ciba Foundation symposium ; 184
[1st ed.] VIII, 347 s. : obr., tab. ; 23 cm
- MeSH
- Neurophysiology MeSH
- Ocular Physiological Phenomena MeSH
- Vision, Ocular physiology MeSH
- Publication type
- Congress MeSH
- Conspectus
- Lékařské vědy. Lékařství
- NML Fields
- fyziologie
- neurovědy
- oftalmologie
Defekty zorného pole bývají častou funkční poruchou, se kterou se v praxi setkáváme. V práci jsou uvedeny výsledky perimetrických vyšetření zdravých dobrovolníkú (odborníků i laiků), kteří simulovali určité poruchy zorného pole na počítačovém perimetru Hupmhrey.
Visual field defects are a common feature of functional visual loss at the ophthalmology praxis. The author reports the perimetry results of healthy volunteers (ophthalmology specialists and laymen, too), who have fabricated specific visual field defects.
PURPOSE: To investigate the fundamental connectivity architecture of neural structures involved in the goal-directed processing of target events. METHODS: Twenty healthy volunteers underwent event-related functional magnetic resonance imaging (fMRI) while performing a standard oddball task. In the task, two types of visual stimuli - rare (target) and frequent - were randomly presented, and subjects were instructed to mentally count the target stimuli. Dynamic causal modeling (DCM), in combination with Bayes factors was used to compare competing neurophysiological models with different intrinsic connectivity structures and input regions within the network of brain regions underlying target stimulus processing. RESULTS: Conventional analysis of fMRI data revealed significantly greater activation in response to the target stimuli (in comparison to the frequent stimuli) in several brain regions, including the intraparietal sulci and supramarginal gyri, the anterior and posterior cingulate gyri, the inferior and middle frontal gyri, the superior temporal sulcus, the precuneus/cuneus, and the subcortical grey matter (caudate and thalamus). The most extensive cortical activations were found in the right intraparietal sulcus (IPS), the anterior cingulate cortex (ACC), and the right lateral prefrontal cortex (PFC). These three regions were entered into the DCM. A comparison on a group level revealed that the dynamic causal models in which the ACC and alternatively the IPS served as input regions were superior to a model in which the PFC was assumed to receive external inputs. No significant difference was observed between the fully connected models with ACC and IPS as input regions. Subsequent analysis of the intrinsic connectivity within two investigated models (IPS and ACC) disclosed significant parallel forward connections from the IPS to the frontal areas and from the ACC to the PFC and the IPS. CONCLUSION: Our findings indicate that during target stimulus processing there is a bidirectional frontoparietal information flow, very likely reflecting parallel activation of two distinct but partially overlapping attentional or attentional/event-encoding neural systems. Additionally, a simple hierarchy within the right frontal lobe is suggested with the ACC exerting influence over the PFC.
Visual attention modulates the firing rate of neurons in many primate cortical areas. In V4, a cortical area in the ventral visual pathway, spatial attention has also been shown to reduce the tendency of neurons to fire closely separated spikes (burstiness). A recent model proposes that a single mechanism accounts for both the firing rate enhancement and the burstiness reduction in V4, but this has not been empirically tested. It is also unclear if the burstiness reduction by spatial attention is found in other visual areas and for other attentional types. We therefore recorded from single neurons in the medial superior temporal area (MST), a key motion-processing area along the dorsal visual pathway, of two rhesus monkeys while they performed a task engaging both spatial and feature-based attention. We show that in MST, spatial attention is associated with a clear reduction in burstiness that is independent of the concurrent enhancement of firing rate. In contrast, feature-based attention enhances firing rate but is not associated with a significant reduction in burstiness. These results establish burstiness reduction as a widespread effect of spatial attention. They also suggest that in contrast to the recently proposed model, the effects of spatial attention on burstiness and firing rate emerge from different mechanisms.
- MeSH
- Biological Clocks physiology MeSH
- Macaca mulatta MeSH
- Brain Waves physiology MeSH
- Nerve Net physiology MeSH
- Attention physiology MeSH
- Space Perception physiology MeSH
- Visual Fields physiology MeSH
- Visual Cortex physiology MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
