Brainmapping of α-chloralose anesthetized rats withT2*-weighted imaging: distinction between the representation of the forepaw and hindpaw in the somatosensory cortex

Abstract

T2*‐weighted imaging at 4.7 T was used to identify the cortical areas activated by electrical stimulation of the forepaw and hindpaw of α‐chloralose anesthetized rats. Variation of the coronal slice position relative to the bregma, showed that the forepaw representation in the somatosensory cortex is more frontal and lateral than that of the hindpaw. Overlap between both activation areas was observed only in a small region in the slice at the level of the bregma. Documented localizations of both representations are in good agreement with earlier observations using invasive techniques. The determination of the separate areas of both paws indicates the feasibility of more complex activation studies in anesthetized animals, such as combined stimulations for the investigation of potentiation or depression effects on individual stimuli. © 1998 John Wiley & Sons, Ltd.

Differential Effects of NMDA and AMPA Glutamate Receptors on Functional Magnetic Resonance Imaging Signals and Evoked Neuronal Activity during Forepaw Stimulation of the Rat

“…Spin excitation was accomplished by a homebuilt 12 cm ID Helmholtz receptive field coil, which was actively decoupled from a 2.4 cm ID receiveonly surface coil used for signal detection. Pilot stimulations served to locate the activation maximum in the contralateral somatosensory cortex, located at an average of ϳ4.5 mm caudal of the rhinal fissure and 4 mm lateral to midline (Bock et al, 1998). A spin-echo echo-planar imaging (EPI) sequence, modified to allow the simultaneous acquisition of blood oxygenation level-dependent (BOLD)-and perfusion-weighted contrast was used for all fMRI experiments.…”

“…This stimulation frequency was also ideally suited for artifact-free recordings of the SEPs in the time gaps between the gradient switching phases of the applied fMRI sequence Ogawa et al, 2000). The applied stimulus intensity of 1 mA produces painless stimulation (Gyngell et al, 1996;Bock et al, 1998), and the interstimulus interval with blocks of 30 s ON versus 90 s OFF stimulation was chosen to ensure absence of any significant habituation (Ances et al, 2000b).…”

Propofol allows precise quantitative arterial spin labelling functional magnetic resonance imaging in the rat

“…Previous studies of electrical mapping of the exposed brain have been confirmed using fMRI for cortical localisation of the body's surface. In the rat, fMRI has been successfully used for the mapping of the forepaw (Hyder et al, 1994;Masamoto et al, 2007;Van Camp et al, 2006), the hindpaw (Bock et al, 1998), the tail (Spenger et al, 2000) and the barrel zones of the whiskers (Lu et al, 2005) .…”

Blood Oxygenation Level-Dependent Visualization of Synaptic Relay Stations of Sensory Pathways along the Neuroaxis in Response to Graded Sensory Stimulation of a Limb

“…Although the small size of the rodent brain initially made fMRI relatively challenging, recent progress in MR hardware and scanning sequences has overcome these difficulties to allow functional mapping of the brain in response to peripheral sensory stimulation (Spenger et al, 2000;Keilholz et al, 2004). Introduction of ␣-chloralose to animal anesthesia has helped to standardize the technique (Bock et al, 1998;Austin et al, 2005). In parallel, fMRI has been applied to animal models of spinal cord injury and stroke (Dijkhuizen et al, 2003;Hofstetter et al, 2003Hofstetter et al, , 2005 and used to monitor pain perception (Tuor et al, 2000;Chang and Shyu, 2001).…”