An Application of Machine Learning to Predict Stiffness Discrimination Thresholds Using Haptics

The effectiveness of our interaction with the computer-generated environments is subject to our physical limitations in real life such as our ability of discriminating differences in stiffness or roughness. This ability, represented by Weber fractions, is usually quantified by means of psychophysical experimentation. The experimentation process is tedious and repetitive as it requires the same task to be completed by participants until the mastery at a certain stimulus level can be ensured before moving onto the next level. Moreover, these thresholds are dependent on the tested standard stimulus level and, therefore, need to be identified by separate experiments for every possible standard stimulus level. The purpose of the current study is to reduce the amount of experimentation and predict the thresholds for stiffness discrimination of individuals after being tested at a single stimulus level. The prediction models tested provide a moderate level of prediction power, but more features, potentially physical and demographical in nature, are needed to increase their effectiveness. The procedure described herein can be extended to any modality other than stiffness and, therefore, has the potential to predict overall palpation effectiveness of an individual after a feasible amount of data is obtained through experimentation.

359 Tailoring of Cognitive Behavior Therapy for Insomnia for Patients with Kidney Failure Undergoing Hemodialysis: The SLEEP-HD Study

Introduction Patients with kidney failure treated with hemodialysis (HD) frequently report insomnia symptoms. Cognitive-behavior therapy for insomnia (CBT-I) is a first line treatment for insomnia but there are unique issues surrounding kidney failure and HD that impact patients’ ability to access CBT-I and follow standard treatment recommendations. This presentation describes CBT-I protocol modifications made to address these issues as part of an ongoing multi-center clinical trial testing the efficacy of telehealth CBT-I compared to trazodone or medication placebo control. Methods CBT-I protocol modifications were made prior to starting the SLEEP-HD randomized trial based upon unique clinical considerations for HD patients, e.g., irregular sleep-wake scheduling that HD treatment demands, and napping during HD sessions or afterwards due to post-HD treatment fatigue. Participants in the SLEEP-HD study are undergoing thrice-weekly maintenance hemodialysis for >3 months and have baseline Insomnia Severity Index scores >10 with sleep disturbances >3 nights/week for >3 months. Participants randomized into the modified CBT-I protocol receive six weekly sessions, delivered by trained CBT-I therapists (1 MSW, 1 PhD) face-to-face via a HIPPA-compliant video telehealth platform. Participants keep a daily sleep diary throughout the CBT-I treatment period. Results To date, 91 patients (mean age=56.5 years [SD=14.7], 48.4% female) recruited from community-based dialysis facilities in Seattle and Albuquerque have been randomized into the SLEEP-HD study (n=31 CBT-I). Forty-eight percent of CBT-I clients have chosen to conduct their telehealth sessions during dialysis with the remainder choosing a different location. CBT-I adaptations include therapists developing weekly bed restriction recommendations based on non-dialysis treatment days; allowing shifts in dialysis day “bed window” scheduling for patients with very early or very late dialysis schedules so long as a consistent total time in bed in maintained; and including napping during early/late dialysis sessions as part of the allowable bed window duration. Treatment modifications were also designed to accommodate the diverse socioeconomic circumstances of dialysis patients, including housing instability, which can impact adherence to some standard stimulus control and bed restriction CBT-I recommendations. Conclusion It is feasible to deliver CBT-I via telehealth to HD patients but modifications to standard protocols are required. Support (if any) This work was supported by PHS grant 5R01AG053221.

Cerebrovascular Reactivity: Purpose, Optimizing Methods, and Limitations to Interpretation – A Personal 20-Year Odyssey of (Re)searching

The brain is a neurovascular organ. A stimulus-response approach is effective in interrogating the physiology of its vasculature. Ideally, the stimulus is standardized across patients, and in a single patient over time. We developed a standard stimulus and attempted to measure, classify, and interpret the many forms of responses. Over the past 20 years, our work has delivered nuanced insights into normal cerebral vascular physiology, as well as adaptive physiological responses in the presence of disease. The trajectory of our understanding did not follow a logical linear progression; rather, it emerged as a coalescence of new, old, and previously dismissed, ideas that had accumulated over time. In this essay, we review what we believe were our most valuable – and sometimes controversial insights during our two decades-long journey.

Stimulus Intervals Modulate the Balance of Brain Activity in the Human Primary Somatosensory Cortex: An ERP Study

Neuronal excitation and inhibition occur in the brain at the same time, and brain activation reflects changes in the sum of excitation and inhibition. This principle has been well-established in lower-level sensory systems, including vision and touch, based on animal studies. However, it is unclear how the somatosensory system processes the balance between excitation and inhibition. In the present ERP study, we modified the traditional spatial attention paradigm by adding double stimuli presentations at short intervals (i.e., 10, 30, and 100 ms). Seventeen subjects participated in the experiment. Five types of stimulation were used in the experiment: a single stimulus (one raised pin for 40 ms), standard stimulus (eight pins for 40 ms), and double stimuli presented at intervals of 10, 30, and 100 ms. The subjects were asked to attend to a particular finger and detect whether the standard stimulus was presented to that finger. The results showed a clear attention-related ERP component in the single stimulus condition, but the suppression components associated with the three interval conditions seemed to be dominant in somatosensory areas. In particular, we found the strongest suppression effect in the ISI-30 condition (interval of 30 ms) and that the suppression and enhancement effects seemed to be counterbalanced in both the ISI-10 and ISI-100 conditions (intervals of 10 and 100 ms, respectively). This type of processing may allow humans to easily discriminate between multiple stimuli on the same body part.

Apparent physical brightness of graphemes is altered by their synaesthetic colour in grapheme-colour synaesthetes

Grapheme-colour synaesthesia is a condition in which the visual perception of letters or numbers induces a specific colour sensation. In this study, we demonstrated that the apparent physical brightness of graphemes is modulated by the synaesthetic colours elicited by them. Synaesthetes first selected a synaesthetic colour corresponding to each capital letter and digit. Then, we selected a grapheme stimulus with a bright synaesthetic colour and one with a dark colour for each synaesthete. Finally, synaesthetes and non-synaesthete controls participated in a brightness judgment task, in which each participant judged the real brightness of each of the two stimuli compared to a standard stimulus. Compared to non-synaesthetes, synaesthetes judged a grapheme with a bright synaesthetic colour to be brighter than one with a dark synaesthetic colour, suggesting that the synaesthetic colour experience of synaesthetes alters their brightness perception. Such alteration in real brightness perception was observed both in those who experienced synaesthetic colours in external space (projector-type synaesthetes) and in those who experienced such colours ‘in the mind’s eye’ (associator-type synaesthetes). These results support the view that early visual processing is modulated by feedback transmitted from the V4 colour area, the neural activation of which accompanies synaesthetic colour experience.

The effects of auditory numerosity and magnitude on visual numerosity representation: An ERP study

Numerical representation is not restricted to sensory modalities. It remains unclear how numerosity processing in different modalities interacts within the brain. Moreover, the effect of continuous magnitudes presented in one modality on the representation of numerosity in another modality has not been well studied. By using event-related potential (ERP) and source localization analyses, the present study examined whether there was an interaction between auditory numerosity and continuous magnitude on visual numerosity representation. A visual dot array (visual standard stimulus) was preceded by sound in which numerosity (Multiple-tone vs. One-tone conditions) and magnitude (Loud-tone vs. Soft-tone conditions) information were manipulated. Then, another visual dot array (visual comparison stimulus) was presented, and participants were required to compare the numerosities of the visual dots. Behavioural results revealed that participants showed smaller just-noticeable differences (JNDs) when visual stimuli were preceded by multiple tones than those when visual stimuli were preceded by one tone. The subsequent ERP analysis of visual standard stimuli revealed that the peak amplitude of N1 was more negative under the Loud-tone condition than that under the Soft-tone condition, which could be related to better preparatory attention. Moreover, a significant interaction between auditory numerosity and magnitude was found within the P2p time window for the standard stimuli. Further source localization analysis identified the effect of N1 and P2p to be in the right middle frontal gyrus (MFG) and left inferior parietal lobule (IPL). The present study suggests that numerosity information presented in one sensory modality could spontaneously affect the numerical representation in another modality.