Home About us Contact
|
Home About us Contact | ||
|
|
||
Visuospatial Attention (visuospatial + attention)
Selected AbstractsfMRI evidence for multisensory recruitment associated with rapid eye movements during sleepHUMAN BRAIN MAPPING, Issue 5 2009Charles Chong-Hwa Hong Abstract We studied the neural correlates of rapid eye movement during sleep (REM) by timing REMs from video recording and using rapid event-related functional MRI. Consistent with the hypothesis that REMs share the brain systems and mechanisms with waking eye movements and are visually-targeted saccades, we found REM-locked activation in the primary visual cortex, thalamic reticular nucleus (TRN), ,visual claustrum', retrosplenial cortex (RSC, only on the right hemisphere), fusiform gyrus, anterior cingulate cortex, and the oculomotor circuit that controls awake saccadic eye movements (and subserves awake visuospatial attention). Unexpectedly, robust activation also occurred in non-visual sensory cortices, motor cortex, language areas, and the ascending reticular activating system, including basal forebrain, the major source of cholinergic input to the entire cortex. REM-associated activation of these areas, especially non-visual primary sensory cortices, TRN and claustrum, parallels findings from waking studies on the interactions between multiple sensory data, and their ,binding' into a unified percept, suggesting that these mechanisms are also shared in waking and dreaming and that the sharing goes beyond the expected visual scanning mechanisms. Surprisingly, REMs were associated with a decrease in signal in specific periventricular subregions, matching the distribution of the serotonergic supraependymal plexus. REMs might serve as a useful task-free probe into major brain systems for functional brain imaging. Hum Brain Mapp 2009. © 2008 Wiley-Liss, Inc. [source] Brain mechanisms of involuntary visuospatial attention: An event-related potential studyHUMAN BRAIN MAPPING, Issue 4 2005Shimin Fu Abstract The brain mechanisms mediating visuospatial attention were investigated by recording event-related potentials (ERPs) during a line-orientation discrimination task. Nonpredictive peripheral cues were used to direct participant's attention involuntarily to a spatial location. The earliest attentional modulation was observed in the P1 component (peak latency about 130 ms), with the valid trials eliciting larger P1 than invalid trials. Moreover, the attentional modulations on both the amplitude and latency of the P1 and N1 components had a different pattern as compared to previous studies with voluntary attention tasks. In contrast, the earliest visual ERP component, C1 (peak latency about 80 ms), was not modulated by attention. Low-resolution brain electromagnetic tomography (LORETA) showed that the earliest attentional modulation occurred in extrastriate cortex (middle occipital gyrus, BA 19) but not in the primary visual cortex. Later attention-related reactivations in the primary visual cortex were found at about 110 ms after stimulus onset. The results suggest that involuntary as well as voluntary attention modulates visual processing at the level of extrastriate cortex; however, at least some different processes are involved by involuntary attention compared to voluntary attention. In addition, the possible feedback from higher visual cortex to the primary visual cortex is faster and occurs earlier in involuntary relative to voluntary attention task. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] REVIEW: The functional organization of the intraparietal sulcus in humans and monkeysJOURNAL OF ANATOMY, Issue 1 2005Christian Grefkes Abstract In macaque monkeys, the posterior parietal cortex (PPC) is concerned with the integration of multimodal information for constructing a spatial representation of the external world (in relation to the macaque's body or parts thereof), and planning and executing object-centred movements. The areas within the intraparietal sulcus (IPS), in particular, serve as interfaces between the perceptive and motor systems for controlling arm and eye movements in space. We review here the latest evidence for the existence of the IPS areas AIP (anterior intraparietal area), VIP (ventral intraparietal area), MIP (medial intraparietal area), LIP (lateral intraparietal area) and CIP (caudal intraparietal area) in macaques, and discuss putative human equivalents as assessed with functional magnetic resonance imaging. The data suggest that anterior parts of the IPS comprising areas AIP and VIP are relatively well preserved across species. By contrast, posterior areas such as area LIP and CIP have been found more medially in humans, possibly reflecting differences in the evolution of the dorsal visual stream and the inferior parietal lobule. Despite interspecies differences in the precise functional anatomy of the IPS areas, the functional relevance of this sulcus for visuomotor tasks comprising target selections for arm and eye movements, object manipulation and visuospatial attention is similar in humans and macaques, as is also suggested by studies of neurological deficits (apraxia, neglect, Bálint's syndrome) resulting from lesions to this region. [source] | ||||||||||