Multi-Target and Multi-Session Transcranial Direct Current Stimulation in Patients With Prolonged Disorders of Consciousness: A Controlled Study

Objectives: To investigate the effect of multi-session transcranial direct current stimulation (tDCS) over the prefrontal area, left dorsolateral prefrontal cortex (DLPFC), and bilateral fronto-temporo-parietal cortices (FTPCs) in patients with prolonged disorders of consciousness (DOC) and to examine the altered cortical interconnections using non-linear electroencephalography (EEG).Methods: In this open-label controlled study, conventional treatments were implemented in both the control and tDCS groups, together with 80 tDCS sessions only in the tDCS group. The order of tDCS targets was as follows: prefrontal area, left FTPC, right FTPC, and left DLPFC. The Coma Recovery Scale-Revised (CRS-R) and non-linear EEG index were evaluated before and after the treatment. Additionally, the modified Glasgow Outcome Scale (mGOS) was used as a follow-up evaluation at 12 months after the disease onset.Results: The CRS-R improved significantly in both groups after the treatment. However, the CRS-R and mGOS were more significantly improved in the tDCS group than in the control group. Among the cross approximate entropy (C-ApEn) indices, the local CA-PA and CA-FA under the affected painful stimulus condition and all local and remote indices of the unaffected side under the unaffected painful stimulus condition were significantly higher in the tDCS group than in the control group. Multivariate logistic regression analysis revealed that group and type were the main relevant factors based on mGOS improvement. Multivariate linear regression analysis revealed that group, CA-FA, and CU-MTU were the main relevant factors based on CRS-R improvement under the affected painful stimulus conditions, whereas only CU-MTU and CU-FPU were relevant under the unaffected painful stimulus condition.Conclusion: Multi-target and multi-session tDCS could improve the cortical connections between the primary sensorimotor and frontal cortices of the affected hemisphere and the prefrontal-parietal and temporo-parietal associative cortical networks of the unaffected hemisphere. Thus, this tDCS protocol may be used as an add-on treatment for prolonged DOC.

Rapid activation of esophageal mechanoreceptors alters the pharyngeal phase of swallow: Evidence for inspiratory activity during swallow

Swallow is a complex behavior that consists of three coordinated phases: oral, pharyngeal, and esophageal. Esophageal distension (EDist) has been shown to elicit pharyngeal swallow, but the physiologic characteristics of EDist-induced pharyngeal swallow have not been specifically described. We examined the effect of rapid EDist on oropharyngeal swallow, with and without an oral water stimulus, in spontaneously breathing, sodium pentobarbital anesthetized cats (n = 5). Electromyograms (EMGs) of activity of 8 muscles were used to evaluate swallow: mylohyoid (MyHy), geniohyoid (GeHy), thyrohyoid (ThHy), thyropharyngeus (ThPh), thyroarytenoid (ThAr), cricopharyngeus (upper esophageal sphincter: UES), parasternal (PS), and costal diaphragm (Dia). Swallow was defined as quiescence of the UES with overlapping upper airway activity, and it was analyzed across three stimulus conditions: 1) oropharyngeal water infusion only, 2) rapid esophageal distension (EDist) only, and 3) combined stimuli. Results show a significant effect of stimulus condition on swallow EMG amplitude of the mylohyoid, geniohyoid, thyroarytenoid, diaphragm, and UES muscles. Collectively, we found that, compared to rapid cervical esophageal distension alone, the stimulus condition of rapid distension combined with water infusion is correlated with increased laryngeal adductor and diaphragm swallow-related EMG activity (schluckatmung), and post-swallow UES recruitment. We hypothesize that these effects of upper esophageal distension activate the brainstem swallow network, and function to protect the airway through initiation and/or modulation of a pharyngeal swallow response.

The Level of Processing Modulates Visual Awareness: Evidence from Behavioral and Electrophysiological Measures

The level of processing hypothesis (LoP) proposes that the transition from unaware to aware visual perception is graded for low-level (i.e., energy, features) stimulus whereas dichotomous for high-level (i.e., letters, words, meaning) stimulus. In this study, we explore the behavioral patterns and neural correlates associated to different depths (i.e., low vs. high) of stimulus processing. The low-level stimulus condition consisted of identifying the color (i.e., blue/blueish vs. red/reddish) of the target, whereas the high-level stimulus condition consisted of identifying stimulus category (animal vs. object). Behavioral results showed that the levels of processing manipulation produced significant differences in both the awareness rating distributions and accuracy performances between tasks, the low-level task producing more intermediate subjective ratings and linearly increasing accuracy performances and the high-level task producing less intermediate ratings and a more nonlinear pattern for accuracies. The electrophysiological recordings revealed two correlates of visual awareness, an enhanced posterior negativity in the N200 time window (visual awareness negativity [VAN]), and an enhanced positivity in the P3 time window (late positivity [LP]). The analyses showed a double dissociation between awareness and the level of processing hypothesis manipulation: Awareness modulated VAN amplitudes only in the low-level color task, whereas LP amplitude modulations were observed only in the higher level category task. These findings are compatible with a two-stage microgenesis model of conscious perception, where an early elementary phenomenal sensation of the stimulus (i.e., the subjective perception of color) would be indexed by VAN, whereas stimulus' higher level properties (i.e., the category of the target) would be reflected in the LP in a later latency range.

Functional Near Infrared Spectroscopy (fNIRS) based Odor Detection and Classification using Functional Data Analysis

An objective approach for odor detection is to analyze the brain activity using imaging techniques during the odor stimulation. In this study, Functional Near Infrared Spectroscopy (fNIRS) is used to record hemodynamic response from the frontal region of the brain by using a 4-channel fNIRS system. The fNIRs data is collected during the odor detection task in which the subjects were asked to press a button when they detect the given odor. Functional Data Analysis (FDA) was applied on fNIRs data to convert discrete measured samples of data to continuous smooth curves. The FDA method enables us to use the bases coefficients of fNIRS smoothed curves for features that represent the shape of the raw fNIRS signal. With the learning algorithm that we proposed, these features were used to train the support vector machine classifier. We evaluated the odor detection problem, in two binary classification cases: odorant vs. non-odorant and odorant vs. fingertapping. The model achieved a classification accuracy of 94.12% and 97.06% over the stimulus condition in the two cases, respectively. Moreover to find the actual predictors we used the extracted defined features (slope, standard deviation, and delta) to train our classifier. We achieved an average accuracy of 91.18 % on classifying odorant vs. non-odorant and an accuracy of 94.12% for odorant vs. fingertapping on the stimulus condition. The results determined that fNIRs signals of odorant and non-odorant are distinguishable without being affected by the motor activity during the experiment.These findings suggest that fNIRs measurement on the forehead could be potentially used for objective and comparably inexpensive assessment of odor detection in cases that the subjective report is unreliable.

Rat Ultrasonic Vocalizations as Social Reinforcers—Implications for a Multilevel Model of the Cognitive Representation of Action and Rats’ Social World

Rats are social animals. For example, rats exhibit mutual-reward preferences, preferring choice alternatives that yield a reward to themselves as well as to a conspecific, over alternatives that yield a reward only to themselves. We have recently hypothesized that such mutual-reward preferences might be the result of reinforcing properties of ultrasonic vocalizations (USVs) emitted by the conspecifics. USVs in rats serve as situation-dependent socio-affective signals with important communicative functions. To test this possibility, here, we trained rats to enter one of two compartments in a T-maze setting. Entering either compartment yielded identical food rewards as well as playback of pre-recorded USVs either in the 50-kHz range, which we expected to be appetitive or therefore a potential positive reinforcer, or in the 22-kHz range predicted to be aversive and therefore a potential negative reinforcer. In three separate experimental conditions, rats chose between compartments yielding either 50-kHz USVs versus a non-ultrasonic control stimulus (condition 1), 22-kHz USVs versus a non-ultrasonic control stimulus (condition 2), or 50-kHz versus 22-kHz USVs (condition 3). Results show that rats exhibit a transient preference for the 50-kHz USV playback over non-ultrasonic control stimuli, as well as an initial avoidance of 22-kHz USV relative to non-ultrasonic control stimuli on trend-level. As rats progressed within session through trials, and across sessions, these preferences diminished, in line with previous findings. These results support our hypothesis that USVs have transiently motivating reinforcing properties, putatively acquired through association processes, but also highlight that these motivating properties are context-dependent and modulatory, and might not act as primary reinforcers when presented in isolation. We conclude this article with a second part on a multilevel cognitive theory of rats’ action and action learning. The “cascade” approach assumes that rats’ cognitive representations of action may be multilevel. A basic physical level of action may be invested with higher levels of action that integrate emotional, motivational, and social significance. Learning in an experiment consists in the cognitive formation of multilevel action representations. Social action and interaction in particular are proposed to be cognitively modeled as multilevel. Our results have implications for understanding the structure of social cognition, and social learning, in animals and humans.

The Influence of Situational Cues on Children’s Creativity in an Alternative Uses Task and the Moderating Effect of Selective Attention

Taking a perception-action perspective, we investigated how the presence of different real objects in children’s immediate situation affected their creativity and whether this effect was moderated by their selective attention. Seventy children between ages 9 and 12 years old participated. Verbal responses on a visual Alternative Uses Task with a low stimulus and high stimulus condition were coded on fluency, flexibility, and originality. Selective attention was measured with a visual search task. Results showed that fluency was not affected by stimulus condition and was unrelated to selective attention. Flexibility was positively associated with selective attention. Originality, net of fluency and flexibility, showed a main effect of stimulus condition in an unexpected direction, as children gave more original responses in the low stimulus condition compared to the high stimulus condition. A significant moderation effect revealed that children with better selective attention skills benefitted from a low stimulus environment, whereas children with weaker selective attention performed better in a high stimulus environment. The findings demonstrate differential effects of the immediate situation and selective attention, and support the hypothesis that creativity is impacted by immediate situation and selective attention, yet in unexpected ways.

Triggers

A disposition’s trigger is its circumstances of manifestation or stimulus condition. Examples of triggers include striking, stretching, and submerging in water. Some argue that no dispositions have triggers. However, such a view leaves it unclear how dispositions can be testable or action guiding. Furthermore, triggers are events, and events involve an object acquiring a property. This leads to a regress problem for pandispositionalism, the view that all properties are dispositions. Some dispositions need a stimulus in order to manifest, and some do not. Dispositions that manifest spontaneously and those that are constantly manifesting do not have triggers. However, some dispositions have a latent or dormant state, and only manifest in certain circumstances.

Effect of a Romantic Song on the Autonomic Nervous System and the Heart of Indian Male Volunteers

In this chapter, the effect of an old generation romantic music (stimulus) on the autonomic nervous system (ANS) activity and the cardiac electrophysiology of Indian male volunteers was investigated. Electrocardiogram (ECG) signals were acquired and the corresponding RR intervals (RRIs) were extracted. The recurrence analysis of the RRI time series suggested a more stable heart rate in the post-stimulus condition. Heart rate variability (HRV) analysis detected a dominant parasympathetic activity in the post-stimulus condition. The time-domain and the wavelet transform analyses of the ECG signals predicted an alteration in the electrical activity of the heart because of the exposure to the music stimulus. The classification of the HRV and the ECG parameters was performed using artificial neural network (ANN), which resulted in an accuracy of ≥80%.

Effect of a Motivational Song on the Autonomic Nervous System and the Heart of Indian Male Volunteers

This chapter investigates the effect of a motivational song (stimulus) on the physiology of the autonomic nervous system and the electrical activity of the heart. Five min electrocardiogram (ECG) signals were acquired from 19 volunteers during the resting and the post-stimulus conditions. The RR intervals (RRIs) were extracted. Recurrence analysis of the RRI time series indicated a higher alteration (acceleration or deceleration) in the heart rate along with the reduction of the causality and patterned behavior of the RRIs. The exact alteration in the ANS physiology was examined using heart rate variability (HRV) analysis. The results of the HRV analysis suggested an increase in the parasympathetic activity in the post-stimulus condition. The alteration in the cardiac activity was analyzed using time domain and joint time-frequency domain analyses of ECG signals. The results suggested an alteration in the cardiac electrical activity of the heart in the post-stimulus condition.

Visual-Somatosensory Integration in Older Adults: Links to Sensory Functioning

Research investigating multisensory integration (MSI) processes in aging is scarce, but converging evidence for larger behavioral MSI effects in older compared to younger adults exists. The current study employed a three-prong approach to determine whether inherent age-related sensory processing declines were associated with larger (i.e., worse) visual-somatosensory (VS) reaction time (RT) facilitation effects. Non-demented older adults (; mean age = 77 years; 55% female) without any medical or psychiatric conditions were included. Participants were instructed to make speeded foot-pedal responses as soon as they detected visual, somatosensory, or VS stimulation. Visual acuity was assessed using the Snellen test while somatosensory sensitivity was determined using vibration thresholds. The aims of the current study were to: (1) replicate a reliable MSI effect; (2) investigate the effect of unisensory functioning on VS RT facilitation; and (3) determine whether sensory functioning combination groups manifested differential MSI effects. Results revealed a significant VS RT facilitation effect that was influenced by somatosensory sensitivity but not visual acuity. That is, older adults with poor somatosensory sensitivity demonstrated significantly larger MSI effects than those with intact somatosensory sensitivity. Additionally, a significant interaction between stimulus condition and sensory functioning group suggested that the group with poor visual acuity and poor somatosensory functioning demonstrated the largest MSI effect compared to the other groups. In summary, the current study reveals that worse somatosensory functioning is associated with larger MSI effects in older adults. To our knowledge, this is first study to identify potential mechanisms behind increased RT facilitation in aging.