Somatosensory evoked response

To identify the location of cord-supplying segmental arteries before aortic surgery can help to reduce the risk of spinal cord ischemia. Monitoring of somatosensory-evoked responses contrib-... 

The most well known of these evoked potentials are the auditory evoked response (AER), the visual evoked response (VER), and the somatosensory evoked response (SSER). The somatosensory system evoked signal can result from multiple types of stimuli to the body—light touch, pain, pressure, temperature, and proprioception (also called joint and muscle position sense). 

There have been few attempts to perform systematic electrophysiological studies in endemic cretinism. Somatosensory evoked potentials and brainstem auditory evoked responses (BAERs) have been reported in congenital hypothyroidism and acquired hypothyroidism. We report the results of electrophysiological studies on 46 cretins from a predominantly myxoedematous endemia in China, where nevertheless, all forms of cretinism are represented. 

Examples of fiiis type include all the different evoked responses (auditory, somatosensory, visual, etc.) and event-related potentials recorded in response to controlled stimuli administered to the body (or any biological system in general). These signals usually reveal functional characteristics of specific pathways in the body. For instance, evoked resptmses to peripheral somatosensory stimu-laticHi reveal the performance of the somatosensory pathway leading to sensory cortex. A segment of cmtical somatosensory evoked potential is shown in Fig. 18.1fi that was obtained after averaging 1(X) stimulus-response pairs. Evoked responses or event-related potentials are usually superimposed... 

APPLICATION I have used wavelet transforms to track the changes in the spectral components of the somatosensory evoked potentials with an ischemic injury (induced by asphyxia) to the brain in a rodent model, as illustrated in Fig. 18.4. The high-frequency components disappear first at the induction cf injury and recover long after recovery of the low-frequency components after resuscitation of the animal. The results seem to suggest differential vulnerabilities in the generators of brain potentials. The somatosensory responses were obtained by averaging 100 stimulus-response pairs. 

In this study, we applied non-invasive approach for evaluating focal cerebral ischemia. The pattern of SSEP response shows that the Pl-Nl amplitude was sipiflcant attenuated but the PI latency was not significant decayed. The hemodynamic response was detected when somatosensory evoke potential was measured from surface recording region. The result of time frequency analysis shows that the high frequency shifts in the initial of the SSEPs. Several studies have also indicated that phenomenon may be caused by brain injury. The results of neurovascular coupling are consistent with previous studies [9]. 

Franceschini M, Nissila 1, Wu W, Diamond S, Bonmassar G, Boas D. Coupling between somatosensory evoked potentials and hemodynamic response in the rat. Neuroimage. 2008 41 189-203. 

Bornhovd, K., Quante, M., Glauche, V., Bromm, B., Weiller, C., and Buchel, C. (2002). Painful stimuli evoke different stimulus-response functions in the amygdala, prefrontal, insula and somatosensory cortex A single-trial fMRI study. Brain 125, 1326-1336. 

Figure 4 Electrically evoked single-unit tactile responses recorded with microwire multielectrode arrays in rat hippocampus CA1, primary somatosensory cortex, and ventral posteromedial nucleus brain regions. (Upper) Raster plot of single-unit spikes before and after electrical current stimulation to whiskers. Each row is a separate trial. (Lower) Summed activity for all trials in 1-ms bins that demonstrate a response to electrical stimulation. The graphs show different latencies in firing for the three different regions. [Data reprinted from Ref. (1 3). Copyright (2007) National Academy of Sciences, U.S.]...

Neurophysiological evaluation of 40 patients with beta-thalassemia major showed abnormal findings in brain-stem-evoked potentials auditory (25%), visual (15%), and somatosensory (7.5%) some had abnormal nerve conduction velocity (25%) and 15% had involvement of multiple neural pathways (39). Subclinical involvement of the auditory pathway was statistically associated with a higher mean daily dose of deferoxamine and a longer duration of treatment. Abnormalities of the somatosensory pathways were related to old age, a long duration of deferoxamine use, and low serum copper concentrations. Multiple neural pathway involvement was related to the duration of treatment. However, deferoxamine is only partly responsible for the subclinical abnormalities of neural pathways often found in patients with beta-thalassemia major. 

The responses of PG neurons to natural stimuli have not been investigated extensively. Thus, although an important part of the ganglionar population corresponds to mechanoreceptors, little is known about their responses to mechanical deformation, as in baroreceptors of the nodose ganglia (6) or somatosensory afferents of the dorsal root ganglia (7). On the other hand, the responses of PG neurons to carotid body natural stimuli have been studied mostly in tissue culture, confrasting the responses evoked from neurons in pure ganglia... 

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