Studies in human sensory perception provide baseline data for both determining the significance of deviations from normative values in subjects with neurological deficits and a basis for understanding fundamental mechanisms of central information processing. These metrics are compared both with metrics obtained from subjects with compromised neurological systems as well as data obtained from high resolution neurophysiological experiments in non-human primates.. The diagnostic system is novel in that the protocols are relatively fast, the stimulator is portable and it makes collecting data from large numbers of diverse subject populations (some with compromised central nervous systems) pragmatic. Studies of such diverse groups could lead to novel insights about the perceptual changes that occur with systemic alterations of cerebral cortical function.

Since the design of our measures of perception are cortically rather than perceptually based, we often refer to perceptual metrics as Cortical Metrics.

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There is substantial evidence that in autism cerebral cortical information processing is abnormal in the "high-order" areas that underlie language and social interaction skills, and also in the "lower-order areas" which accomplish the initial processing of thalamocortical afferent activity evoked by sensory stimulation. Abnormalities in the response of primary sensory cortex in autism have been convincingly demonstrated using psychophysical testing procedures and neurophysiological recording methods. For example, autism subjects routinely exhibit hyperarousal to sensory input, and a decreased ability to select among competing sensory inputs. Furthermore, the regions of cortex devoted to stimulus-driven sensory processing display excessive responsivity in individuals with autism, and exhibit little-to-no specificity in their response to either the location or modality of a sensory stimulus.

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The major goal of the work proposed is to utilize a novel method for quantitative sensory testing of tactile information processing to characterize an aging subject population. The method is driven by a conceptual model derived from neurophysiological observations of the dynamic changes that are evoked in SI cortex when stimuli that promote cortical regional interactions are presented to the skin. These sensory testing methods are atypical of the sensory testing methods that have dominated the literature for the past several decades primarily because they are designed from the perspective of generating measurable percepts that are most influenced by cortical-cortical interactions.

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CM technology is currently being used in multiple studies to evaluate the efficacy of pharmacological interventions in several different neurological disorders. Previous studies have demonstrated sensitivity of the method to drug effects. In one study (Folger et al, 2008), we investigated the effects of a low dosage of dextromethorphan (60 mg of DXM; over-the counter cough syrup), an NMDAR antagonist, to observe if it had an impact on an individual’s performance. The significance of that study was that while the drug had no significant effect on discriminative measures that are predominantly mediated by peripheral factors, the adaptation metrics were significantly impacted. Over a 3 hour time course, the low dose of cough syrup caused the adaptation metrics to deviate from normative values and returned to baseline. Thus, this demonstrated that the adaptation metric is a sensitive reflection of central information processing, and the sensitivity far exceeds any metrics that can be obtained by modern medical imaging techniques.

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Neurophysiology. Our non-invasive sensory testing is made possible through neurophysiological studies. Using traditional electrophysiological recordings and optical intrinsic signal imaging, labs across the globe have been able to investigate the underpinnings of the primate somatosensory cortex. As a result, we have been able to create sensory testing paradigms that can be used on human subjects in a clinical setting. Without this research, it would be impossible to draw conclusions as to the underlying neurophysiology of human perception. Consequently, we are able to use mathematical analysis on a patient's sensory testing response to determine whether or not the cortex is functioning properly. Additionally, though much lower in resolution than animal neurophysiological studies, we are currently conducting validation studies with human imaging methods (fMRI, MRS, EEG and MEG).

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Central to the methodology that we are developing is a unique portable and non-invasive tactile stimulator system that is USB interfaced to any laptop or computer system for a wide range of highly resolved, precisely controlled tactile stimuli.

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