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Primary Sensory Cortex (primary + sensory_cortex)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Neural connectivity in hand sensorimotor brain areas: An evaluation by evoked field morphology

HUMAN BRAIN MAPPING, Issue 2 2005
Franca Tecchio
Abstract The connectivity pattern of the neural network devoted to sensory processing depends on the timing of relay recruitment from receptors to cortical areas. The aim of the present work was to uncover and quantify the way the cortical relay recruitment is reflected in the shape of the brain-evoked responses. We recorded the magnetic somatosensory evoked fields (SEF) generated in 36 volunteers by separate bilateral electrical stimulation of median nerve, thumb, and little fingers. After defining an index that quantifies the shape similarity of two SEF traces, we studied the morphologic characteristics of the recorded SEFs within the 20-ms time window that followed the impulse arrival at the primary sensory cortex. Based on our similarity criterion, the shape of the SEFs obtained stimulating the median nerve was observed to be more similar to the one obtained from the thumb (same median nerve innervation) than to the one obtained from the little finger (ulnar nerve innervation). In addition, SEF shapes associated with different brain regions were more similar within an individual than between subjects. Because the SEF morphologic characteristics turned out to be quite diverse among subjects, we defined similarity levels that allowed us to identify three main classes of SEF shapes in normalcy. We show evidence that the morphology of the evoked response describes the anatomo-functional connectivity pattern in the primary sensory areas. Our findings suggest the possible existence of a thalamo-cortico-thalamic responsiveness loop related to the different classes. Hum Brain Mapp 24:99,108, 2005. © 2004 Wiley-Liss, Inc. [source]

Functional MRI of the rodent somatosensory pathway using multislice echo planar imaging,

MAGNETIC RESONANCE IN MEDICINE, Issue 1 2004
Shella D. Keilholz
Abstract A multislice EPI sequence was used to obtain functional MR images of the entire rat brain with BOLD contrast at 11.7 T. Ten to 11 slices covering the rat brain, with an in-plane resolution of 300 ,m, provided enough sensitivity to detect activation in brain regions known to be involved in the somatosensory pathway during stimulation of the forelimbs. These regions were identified by warping a digitized rat brain atlas to each set of images. Data analysis was constrained to four major areas of the somatosensory pathway: primary and secondary somatosensory cortices, thalamus, and cerebellum. Incidence maps were generated. Electrical stimulation at 3 Hz led to significant activation in the primary sensory cortex in all rats. Activation in the secondary sensory cortex and cerebellum was observed in 70% of the studies, while thalamic activation was observed in 40%. The amplitude of activation was measured for each area, and average response time courses were calculated. Finally, the frequency dependence of the response to forepaw stimulation was measured in each of the activated areas. Optimal activation occurred in all areas at 3 Hz. These results demonstrate that whole-brain fMRI can be performed on rodents at 11.7 T to probe a well-defined neural network. Magn Reson Med 52:89,99, 2004. Published 2004 Wiley-Liss, Inc. [source]

A metric for space

HIPPOCAMPUS, Issue 12 2008
Edvard I. Moser
Abstract Not all areas of neuronal systems investigation have matured to the stage where computation can be understood at the microcircuit level. In mammals, insights into cortical circuit functions have been obtained for the early stages of sensory systems, where signals can be followed through networks of increasing complexity from the receptors to the primary sensory cortices. These studies have suggested how neurons and neuronal networks extract features from the external world, but how the brain generates its own codes, in the higher-order nonsensory parts of the cortex, has remained deeply mysterious. In this terra incognita, a path was opened by the discovery of grid cells, place-modulated entorhinal neurons whose firing locations define a periodic triangular or hexagonal array covering the entirety of the animal's available environment. This array of firing is maintained in spite of ongoing changes in the animal's speed and direction, suggesting that grid cells are part of the brain's metric for representation of space. Because the crystal-like structure of the firing fields is created within the nervous system itself, grid cells may provide scientists with direct access to some of the most basic operational principles of cortical circuits. © 2008 Wiley-Liss, Inc. [source]

fMRI evidence for multisensory recruitment associated with rapid eye movements during sleep

HUMAN BRAIN MAPPING, Issue 5 2009
Charles 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]