scholarly journals Algorithm for improving psychophysical threshold estimates by detecting sustained inattention in experiments using PEST

2018 ◽  
Vol 80 (6) ◽  
pp. 1629-1645 ◽  
Author(s):  
Mike D. Rinderknecht ◽  
Raffaele Ranzani ◽  
Werner L. Popp ◽  
Olivier Lambercy ◽  
Roger Gassert
Keyword(s):  
Psychophysical Threshold

Psychophysical threshold variability in cochlear implant subjects

2003 ◽  
Vol 180 (1-2) ◽  
pp. 101-113 ◽  
Author(s):  
William D Ferguson ◽  
Leslie M Collins ◽  
David W Smith
Keyword(s):  
Cochlear Implant ◽  
Psychophysical Threshold

scholarly journals Effects of Electrical Pulse Polarity Shape on Intra Cochlear Neural Responses in Humans: Triphasic Pulses with Anodic and Cathodic Second Phase

2020 ◽  
Author(s):  
Katharina Kretzer ◽  
David P. Herrmann ◽  
Sabrina H. Pieper ◽  
Andreas Bahmer
Keyword(s):  
Pulse Shape ◽  
Amplitude Ratio ◽  
Electrical Pulse ◽  
Second Phase ◽  
Neural Responses ◽  
Compound Action Potentials ◽  
Psychophysical Threshold ◽  
Pulse Polarity ◽  
Phase Amplitude ◽  
Pulse Stimulation

Modern cochlear implants employ charge-balanced biphasic and triphasic pulses. However, the effectiveness of electrical pulse shape and polarity is still a matter of debate. For this purpose, in a previous study (Bahmer & Baumann, 2013) electrophysiological and psychophysical measurement after triphasic pulse stimulation with cathodic second phase was determined. Depending on the pulse shape configuration, the stimulation effectiveness differed similarly for electrophysiological and psychophysical measurements. However, the experiments were limited to stimulation pulses with cathodic second phase. In this study, cathodic and anodic second phase stimulation was applied. Evoked compound action potentials (ECAPs) and psychophysical responses were recorded in eleven cochlear implant recipients (SYNCHRONY/SONATAti100/PULSARci100 devices, MED-EL Innsbruck). We compared the strength of the ECAP responses with individual psychophysical threshold levels depending on the pulse shape. Results for pulses with cathodic second phase showed the weakest ECAP response and highest psychophysical thresholds for symmetric triphasic pulse shapes, and the strongest ECAP response and lowest psychophysical thresholds for biphasic pulses. The ECAP responses for anodic second phase differed from the results of triphasic stimulation with cathodic second phase. The U-shape of the ECAP response with increasing phase amplitude ratio (PAR) for cathodic second phase could not be observed for the anodic second phase. Instead, a flat curve was observed. In contrast, psychophysical threshold curves with increasing PAR were similar between cathodic and anodic second phase stimulation.

scholarly journals Modeling Social Sensory Processing During Social Computerized Cognitive Training for Psychosis Spectrum: The Resting-State Approach

2020 ◽  
Vol 11 ◽  
Author(s):  
Lana Kambeitz-Ilankovic ◽  
Julian Wenzel ◽  
Shalaila S. Haas ◽  
Anne Ruef ◽  
Linda A. Antonucci ◽  
...  
Keyword(s):  
Cognitive Training ◽  
Sensory Processing ◽  
Default Mode Network ◽  
Resting State ◽  
Social Cognitive ◽  
Pearson Correlation ◽  
Matching Task ◽  
Default Mode ◽  
Computerized Cognitive Training ◽  
Psychophysical Threshold

Background: Greater impairments in early sensory processing predict response to auditory computerized cognitive training (CCT) in patients with recent-onset psychosis (ROP). Little is known about neuroimaging predictors of response to social CCT, an experimental treatment that was recently shown to induce cognitive improvements in patients with psychosis. Here, we investigated whether ROP patients show interindividual differences in sensory processing change and whether different patterns of SPC are (1) related to the differential response to treatment, as indexed by gains in social cognitive neuropsychological tests and (2) associated with unique resting-state functional connectivity (rsFC).Methods: Twenty-six ROP patients completed 10 h of CCT over the period of 4–6 weeks. Subject-specific improvement in one CCT exercise targeting early sensory processing—a speeded facial Emotion Matching Task (EMT)—was studied as potential proxy for target engagement. Based on the median split of SPC from the EMT, two patient groups were created. Resting-state activity was collected at baseline, and bold time series were extracted from two major default mode network (DMN) hubs: left medial prefrontal cortex (mPFC) and left posterior cingulate cortex (PCC). Seed rsFC analysis was performed using standardized Pearson correlation matrices, generated between the average time course for each seed and each voxel in the brain.Results: Based on SPC, we distinguished improvers—i.e., participants who showed impaired performance at baseline and reached the EMT psychophysical threshold during CCT—from maintainers—i.e., those who showed intact EMT performance at baseline and sustained the EMT psychophysical threshold throughout CCT. Compared to maintainers, improvers showed an increase of rsFC at rest between PCC and left superior and medial frontal regions and the cerebellum. Compared to improvers, maintainers showed increased rsFC at baseline between PCC and superior temporal and insular regions bilaterally.Conclusions: In ROP patients with an increase of connectivity at rest in the default mode network, social CCT is still able to induce sensory processing changes that however do not translate into social cognitive gains. Future studies should investigate if impairments in short-term synaptic plasticity are responsible for this lack of response and can be remediated by pharmacological augmentation during CCT.

Chromatic input to cells of the magnocellular pathway: Mean chromaticity and the relative phase of modulated lights

2004 ◽  
Vol 21 (3) ◽  
pp. 309-314 ◽  
Author(s):  
BARRY B. LEE ◽  
HAO SUN
Keyword(s):  
Phase Shift ◽  
Relative Phase ◽  
Relative Size ◽  
Physiological Mechanism ◽  
Opposite Polarity ◽  
Cell Behavior ◽  
Magnocellular Pathway ◽  
Psychophysical Threshold

If the relative phase of red and green modulated lights is changed, at low temporal frequencies the response of cells of the magnocellular (MC) pathway has been found to be minimal not to counterphase, chromatic modulation (as expected of a luminance mechanism) but shifted to some phase intermediate between luminance and chromatic modulation. The results could only be modeled by assuming interaction between achromatic and chromatic inputs to MC cells. The ‘phase shift’ resembled that seen with psychophysical threshold measurements using the same stimuli. Psychophysical results also showed that the phase shift is dependent on the chromaticity of a background. The results reported here show that the direction of the phase shift in MC cells is reversed by changing the background from long to short wavelengths and is consistent with psychophysical observations. Cell behavior was again modeled by assuming vector summation of achromatic and chromatic inputs. The reversal of phase-shift direction requires a reversal in polarity of the chromatic input. The underlying physiological mechanism may involve summation of chromatic signals of opposite polarity; if the relative size of these signals depends on the background, this may determine the direction of phase shift.

Behavioral estimates of absolute threshold in rat

1994 ◽  
Vol 11 (6) ◽  
pp. 1077-1082 ◽  
Author(s):  
Carmen Muñoz Tedó ◽  
Pilar Herreros De Tejada ◽  
Daniel G. Green
Keyword(s):  
Light Intensity ◽  
Evoked Potentials ◽  
Visual Evoked Potentials ◽  
Light Stimulus ◽  
Absolute Threshold ◽  
Albino Rats ◽  
Water Reinforcement ◽  
Behavioral Experiments ◽  
Psychophysical Threshold ◽  
Behavioral Methods

AbstractDark-adapted thresholds of albino and pigmented rats were estimated using behavioral methods. Albino and pigmented rats who had been water deprived learned to bar press for water reinforcement when a light stimulus was presented. Absolute threshold was defined to be the light intensity at which bar pressing behavior was significantly modified by the presence of the light stimulus. Albino rats had an average threshold of −5.23 log cd/m2 and the pigmented rats had a threshold of −5.0 log cd/m2. These values are close to −5.3 log cd/m2, the psychophysical threshold of human observers in the same apparatus. Consistent with our earlier electrophysiology, these behavioral experiments provide no evidence for an albino/pigmented sensitivity difference. Comparisons are made between behavioral and electrophysiological determinations of absolute threshold in albino and pigmented rats. Thresholds determined behaviorally agree remarkably well with those derived from visual evoked potentials.

Visual impairment by surrounding noise is due to interactions among stimuli in the higher-order visual cortex

2014 ◽  
Vol 112 (3) ◽  
pp. 620-630
Author(s):  
Hironori Kumano ◽  
Takanori Uka
Keyword(s):  
Visual Cortex ◽  
Peripheral Vision ◽  
Higher Order ◽  
Visual Neurons ◽  
Middle Temporal ◽  
Mt Neurons ◽  
Impaired Ability ◽  
Psychophysical Threshold ◽  
Task Irrelevant ◽  
Visual Area Mt

Observers have difficulty identifying a target in their peripheral vision in the presence of surrounding stimuli. Although hypotheses addressing this phenomenon have been proposed, such as the integration of stimuli and surround suppression in the higher-order visual cortex, no direct comparisons of the psychophysical and neuronal sensitivities have been performed. Here we measured the performance of monkeys with a variant of the direction discrimination task using a center/surround bipartite random-dot stimulus while simultaneously recording from isolated neurons from the middle temporal visual area (MT). The psychophysical threshold increased with the addition of a task-irrelevant noise annulus that surrounded the task-relevant motion stimuli. The neuronal threshold of MT neurons also increased at a spatial scale similar to the psychophysical threshold. This suggests that the impaired ability in our task resulted from impairment in the MT area. Importantly, reduced neuronal performance was due to both a reduced response to preferred motion and an enhanced response to nonpreferred motion. These observations suggest that impairment caused by surrounding noise results from interactions between stimuli and noise and not from a reduction in the response of visual neurons.

scholarly journals Melanopic stimulation does not alter psychophysical threshold sensitivity for luminance flicker

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Joris Vincent ◽  
Edda B. Haggerty ◽  
David H. Brainard ◽  
Geoffrey K. Aguirre
Keyword(s):  
Circadian Rhythm ◽  
Visual Perception ◽  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Threshold Sensitivity ◽  
Retinal Ganglion ◽  
Pupil Response ◽  
Visual Functions ◽  
Psychophysical Threshold ◽  
Rod And Cone Photoreceptors

AbstractIn addition to the rod and cone photoreceptors the retina contains intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells express the photopigment melanopsin and are known to be involved in reflexive visual functions such as pupil response and photo-entrainment of the circadian rhythm. It is possible that the ipRGCs contribute to conscious visual perception, either by providing an independent signal to the geniculo-striate pathway, or by interacting with and thus modifying signals arising from “classical” retinal ganglion cells that combine and contrast cone input. Here, we tested for the existence of an interaction by asking if a 350% change in melanopsin stimulation alters psychophysical sensitivity for the detection of luminance flicker. In Experiment 1, we tested for a change in the threshold for detecting luminance flicker in three participants after they adapted to backgrounds with different degrees of tonic melanopsin stimulation. In Experiments 2 and 3, this test was repeated, but now for luminance flicker presented on a transient pedestal of melanopsin stimulation. Across the three experiments, no effect of melanopsin stimulation upon threshold flicker sensitivity was found. Our results suggest that even large changes in melanopsin stimulation do not affect near-threshold, cone-mediated visual perception.

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