Rationale: Since the mid-1970s, cross-species translational studies of prepulse inhibition (PPI) have increased at an astounding pace as the value of this neurobiologically informative measure has been optimized. PPI occurs when a relatively weak sensory event (the prepulse) is presented 30–500 ms before a strong startle-inducing stimulus, and reduces the magnitude of the startle response. In humans, PPI occurs in a robust, predictable manner when the prepulse and startling stimuli occur in either the same or different modalities (acoustic, visual, or cutaneous). Objective: This review covers three areas of interest in human PPI studies. First, we review the normal influences on PPI related to the underlying construct of sensori- (prepulse) motor (startle reflex) gating. Second, we review PPI studies in psychopathological disorders that form a family of gating disorders. Third, we review the relatively limited but interesting and rapidly expanding literature on pharmacological influences on PPI in humans. Methods: All studies identified by a computerized literature search that addressed the three topics of this review were compiled and evaluated. The principal studies were summarized in appropriate tables. Results: The major influences on PPI as a measure of sensorimotor gating can be grouped into 11 domains. Most of these domains are similar across species, supporting the value of PPI studies in translational comparisons across species. The most prominent literature describing deficits in PPI in psychiatrically defined groups features schizophrenia-spectrum patients and their clinically unaffected relatives. These findings support the use of PPI as an endophenotype in genetic studies. Additional groups of psychopathologically disordered patients with neuropathology involving cortico-striato-pallido-pontine circuits exhibit poor gating of motor, sensory, or cognitive information and corresponding PPI deficits. These groups include patients with obsessive compulsive disorder, Tourette's syndrome, blepharospasm, temporal lobe epilepsy with psychosis, enuresis, and perhaps post-traumatic stress disorder (PTSD). Several pharmacological manipulations have been examined for their effects on PPI in healthy human subjects. In some cases, the alterations in PPI produced by these drugs in animals correspond to similar effects in humans. Specifically, dopamine agonists disrupt and nicotine increases PPI in at least some human studies. With some other compounds, however, the effects seen in humans appear to differ from those reported in animals. For example, the PPI-increasing effects of the glutamate antagonist ketamine and the serotonin releaser MDMA in humans are opposite to the PPI-disruptive effects of these compounds in rodents. Conclusions: Considerable evidence supports a high degree of homology between measures of PPI in rodents and humans, consistent with the use of PPI as a cross-species measure of sensorimotor gating. Multiple investigations of PPI using a variety of methods and parameters confirm that deficits in PPI are evident in schizophrenia-spectrum patients and in certain other disorders in which gating mechanisms are disturbed. In contrast to the extensive literature on clinical populations, much more work is required to clarify the degree of correspondence between pharmacological effects on PPI in healthy humans and those reported in animals.

Human studies of prepulse inhibition of startle: normal subjects, patient groups, and pharmacological studies.

A common problem with designing and developing applications with tactile interfaces is the lack of a vocabulary that allows one to describe or communicate about haptics. Here we present the findings from a study exploring participants' verbalizations of their tactile experiences across two modulated tactile stimuli (16Hz and 250Hz) related to two important mechanoreceptors in the human hand. The study, with 14 participants, applied the explicitation interview technique to capture detailed descriptions of the diachronic and synchronic structure of tactile experiences. We propose 14 categories for a human-experiential vocabulary based on the categorization of the findings and tie them back to neurophysiological and psychophysical data on the human hand. We finally discuss design opportunities created through this experiential understanding in relation to the two mechanoreceptors.

Talking about tactile experiences

The computational brain: Patricia S. Churchland and Terrence J. Sejnowski (MIT Press, Cambridge, MA, 1992); xi, 544 pages, $39.95

https://webs.wofford.edu/pittmandw/psy230/lab/koch.pdf

The neurobiology of startle.

Quantitative sensory testing: a comprehensive protocol for clinical trials

Contents: Preface. Psychophysical Measurement of Thresholds: Differential Sensitivity. Psychophysical Measurement of Thresholds: Absolute Sensitivity. The Classical Psychophysical Methods. Classical Psychophysical Theory. The Theory of Signal Detection. Further Considerations of TSD. Procedures of TSD. Some Applications of TSD. The Measurement of Sensory Attributes and Discrimination Scales. Partition Scales. Psychophysical Ration Scaling. Evaluation of Ratio Scaling Methods. The Psychophysical Law. Some Fundamental Issues in Psychophysical Scaling.

Psychophysics: The Fundamentals

Although previous physiological and anatomical experiments have identified four afferent fiber types (PC, RA, SA II, and SA I) in glabrous (nonhairy) skin of the human somatosensory periphery, only three have been shown to mediate tactile (mechanoreceptive) sensation. Psychophysical evidence that four channels (P, NP I, NP II, and NP III) do, indeed, participate in the perceptual process is presented. In a series of experiments involving selective masking of the various channels, modification of the skin‐surface temperature, and testing cutaneous sensitivity down to very low‐vibratory frequencies, the fourth psychophysical channel (NP III) is defined. Based on these experiments and previous work from our laboratory, it is concluded that the four channels work in conjunction at threshold to create an operating range for the perception of vibration that extends from at least 0.4 to greater than 500 Hz. Each of the four channels appears to mediate specific portions of the overall threshold‐frequency characteristic. Selection of appropriate neural‐response criteria from previously published physiological data and correlation of their derived frequency characteristics with the four psychophysical channels indicates that each channel has its own physiological substrate: P channel and PC fibers, NP I channel and RA fibers, NP II channel and SA II fibers, and NP III channel and SA I fibers. These channels partially overlap in their absolute sensitivities, making it likely that suprathreshold stimuli may activate two or more of the channels at the same time. Thus the perceptual qualities of touch may be determined by the combined inputs from four channels.

Four channels mediate the mechanical aspects of touch

The problems of psychophysics -- the scientific study of the relationship between stimulus and sensation -- constitute some of the most basic problems of modern psychology This book introduces students to the fundamentals of classical and modern psychophysics

George A. Gescheider

Papers

Psychophysics: The Fundamentals

Four channels mediate the mechanical aspects of touch

Psychophysics: Method, Theory, and Application

Psychophysics: The fundamentals, 3rd ed.

Psychophysics: Method and theory