Development and validation of a contouring guideline for the taste bud bearing tongue mucosa.

PURPOSE: To introduce a contouring guideline for the taste bud bearing tongue mucosa for head and neck cancer patients receiving radiotherapy. METHODS AND MATERIALS: CT simulation images of oropharyngeal cancer patients were used to delineate both the whole tongue (extrinsic/intrinsic tongue muscles, floor of mouth) and the taste bud bearing tongue mucosa (method A: adaptation of the whole tongue structure; method B: axial adaptation of a mid-sagittal contour). Volumetric and dosimetric parameters of the whole tongue and the two methods of mucosal delineation, spatial overlap between methods A and B, and inter-observer variability for method B were calculated. RESULTS: The study cohort was comprised of 70 patients with T1-4 N0-1 tonsillar (83%) and base of tongue (17%) cancers. Most of the comparative parameters between the whole tongue and mucosa (method A) significantly differed (mean, minimum, and maximum dose, V5-V70, D40-D90). The mean dose calculated for the whole tongue deviated on average 3.77 Gy compared to method A. No significant differences were found between methods A and B of the taste bud bearing tongue mucosa structure, and none of the dosimetric parameters differed more than 1.03 Gy on average. The mean Dice similarity coefficient for both mucosal structures was 0.79 ± 0.05, and 0.63 ± 0.12 for the inter-observer analysis of method B. CONCLUSIONS: We defined two methods for delineating the taste bud bearing mucosa and both are equally satisfactory procedures. Either method is preferable over delineation of the whole tongue as organ at risk for taste impairment.

Daily computed tomography image guidance: Dosimetric advantages outweigh low-dose radiation exposure for treatment of mediastinal lymphoma.

CT-guided treatment delivery can improve target localization in mediastinal lymphoma patients treated with "butterfly" intensity-modulated radiotherapy and deep-inspiration breath hold. Although daily CT imaging adds additional radiation exposure, its use may be justified given the greater normal tissue sparing enabled by PTV margin reduction.

The visual speech head start improves perception and reduces superior temporal cortex responses to auditory speech.

Visual information about speech content from the talker's mouth is often available before auditory information from the talker's voice. Here we examined perceptual and neural responses to words with and without this visual head start. For both types of words, perception was enhanced by viewing the talker's face, but the enhancement was significantly greater for words with a head start. Neural responses were measured from electrodes implanted over auditory association cortex in the posterior superior temporal gyrus (pSTG) of epileptic patients. The presence of visual speech suppressed responses to auditory speech, more so for words with a visual head start. We suggest that the head start inhibits representations of incompatible auditory phonemes, increasing perceptual accuracy and decreasing total neural responses. Together with previous work showing visual cortex modulation (Ozker et al., 2018b) these results from pSTG demonstrate that multisensory interactions are a powerful modulator of activity throughout the speech perception network.

A causal inference explanation for enhancement of multisensory integration by co-articulation.

The McGurk effect is a popular assay of multisensory integration in which participants report the illusory percept of "da" when presented with incongruent auditory "ba" and visual "ga" (AbaVga). While the original publication describing the effect found that 98% of participants perceived it, later studies reported much lower prevalence, ranging from 17% to 81%. Understanding the source of this variability is important for interpreting the panoply of studies that examine McGurk prevalence between groups, including clinical populations such as individuals with autism or schizophrenia. The original publication used stimuli consisting of multiple repetitions of a co-articulated syllable (three repetitions, AgagaVbaba). Later studies used stimuli without repetition or co-articulation (AbaVga) and used congruent syllables from the same talker as a control. In three experiments, we tested how stimulus repetition, co-articulation, and talker repetition affect McGurk prevalence. Repetition with co-articulation increased prevalence by 20%, while repetition without co-articulation and talker repetition had no effect. A fourth experiment compared the effect of the on-line testing used in the first three experiments with the in-person testing used in the original publication; no differences were observed. We interpret our results in the framework of causal inference: co-articulation increases the evidence that auditory and visual speech tokens arise from the same talker, increasing tolerance for content disparity and likelihood of integration. The results provide a principled explanation for how co-articulation aids multisensory integration and can explain the high prevalence of the McGurk effect in the initial publication.

Mouth and Voice: A Relationship between Visual and Auditory Preference in the Human Superior Temporal Sulcus.

Cortex in and around the human posterior superior temporal sulcus (pSTS) is known to be critical for speech perception. The pSTS responds to both the visual modality (especially biological motion) and the auditory modality (especially human voices). Using fMRI in single subjects with no spatial smoothing, we show that visual and auditory selectivity are linked. Regions of the pSTS were identified that preferred visually presented moving mouths (presented in isolation or as part of a whole face) or moving eyes. Mouth-preferring regions responded strongly to voices and showed a significant preference for vocal compared with nonvocal sounds. In contrast, eye-preferring regions did not respond to either vocal or nonvocal sounds. The converse was also true: regions of the pSTS that showed a significant response to speech or preferred vocal to nonvocal sounds responded more strongly to visually presented mouths than eyes. These findings can be explained by environmental statistics. In natural environments, humans see visual mouth movements at the same time as they hear voices, while there is no auditory accompaniment to visual eye movements. The strength of a voxel's preference for visual mouth movements was strongly correlated with the magnitude of its auditory speech response and its preference for vocal sounds, suggesting that visual and auditory speech features are coded together in small populations of neurons within the pSTS.SIGNIFICANCE STATEMENT Humans interacting face to face make use of auditory cues from the talker's voice and visual cues from the talker's mouth to understand speech. The human posterior superior temporal sulcus (pSTS), a brain region known to be important for speech perception, is complex, with some regions responding to specific visual stimuli and others to specific auditory stimuli. Using BOLD fMRI, we show that the natural statistics of human speech, in which voices co-occur with mouth movements, are reflected in the neural architecture of the pSTS. Different pSTS regions prefer visually presented faces containing either a moving mouth or moving eyes, but only mouth-preferring regions respond strongly to voices.

Combined central and peripheral stimulation to facilitate motor recovery after stroke: the effect of number of sessions on outcome.

BACKGROUND: Proof-of-principle studies have demonstrated transient beneficial effects of transcranial direct current stimulation (tDCS) on motor function in stroke patients, mostly after single treatment sessions. OBJECTIVE: To assess the efficacy of multiple treatment sessions on motor outcome. METHODS: The authors examined the effects of two 5-day intervention periods of bihemispheric tDCS and simultaneous occupational/physical therapy on motor function in a group of 10 chronic stroke patients. RESULTS: The first 5-day period yielded an increase in Upper-Extremity Fugl-Meyer (UE-FM) scores by 5.9 ± 2.4 points (16.6% ± 10.6%). The second 5-day period resulted in further meaningful, although significantly lower, gains with an additional improvement of 2.3 ± 1.4 points in UE-FM compared with the end of the first 5-day period (5.5% ± 4.2%). The overall mean change after the 2 periods was 8.2 ± 2.2 points (22.9% ± 11.4%). CONCLUSION: The results confirm the efficacy of bihemispheric tDCS in combination with peripheral sensorimotor stimulation. Furthermore, they demonstrate that the effects of multiple treatment sessions in chronic stroke patients may not necessarily lead to a linear response function, which is of relevance for the design of experimental neurorehabilitation trials.

Predicting functional motor potential in chronic stroke patients using diffusion tensor imaging.

Electrophysiological and neuroimaging studies suggest that the integrity of ipsilesional and inter-hemispheric motor circuits is important for motor recovery after stroke. However, the extent to which each of these tracts contributes to the variance in outcome remains unclear. We examined whether diffusion tensor imaging (DTI)-derived measures of corticospinal and transcallosal tracts predict motor improvement in an experimental neurorehabilitation trial. 15 chronic stroke patients received bihemispheric transcranial direct current stimulation and simultaneous physical/occupational therapy for five consecutive days. Motor impairment was assessed prior to and after the intervention. At baseline, the patients underwent DTI; probabilistic fiber tracking was used to reconstruct the pyramidal tract (PT), alternate descending motor fibers (aMF), and transcallosal fibers connecting primary motor cortices (M1-M1). Ipsilesional corticospinal tracts (PT, aMF) and M1-M1 showed significantly decreased fractional anisotropy (FA) and increased directional diffusivities when compared to age-matched healthy controls. Partial correlations revealed that greater gains in motor function were related to higher FA values and lower directional diffusivities of transcallosal and ipsilesional corticospinal tracts. M1-M1 diffusivity had the greatest predictive value. An additional slice-by-slice analysis of FA values along the corticospinal tracts demonstrated that the more the ipsilesional FA profiles of patients resembled those of healthy controls, the greater their functional improvement. In conclusion, our study shows that DTI-derived measures can be used to predict functional potential for subsequent motor recovery in chronic stroke patients. Diffusivity parameters of individual tracts and tract combinations may help in assessing a patient's individual recovery potential and in determining optimal neurorehabilitative interventions.

Impairment of speech production predicted by lesion load of the left arcuate fasciculus.

BACKGROUND AND PURPOSE: Previous studies have suggested that patients' potential for poststroke language recovery is related to lesion size; however, lesion location may also be of importance, particularly when fiber tracts that are critical to the sensorimotor mapping of sounds for articulation (eg, the arcuate fasciculus) have been damaged. In this study, we tested the hypothesis that lesion loads of the arcuate fasciculus (ie, volume of arcuate fasciculus that is affected by a patient's lesion) and of 2 other tracts involved in language processing (the extreme capsule and the uncinate fasciculus) are inversely related to the severity of speech production impairments in patients with stroke with aphasia. METHODS: Thirty patients with chronic stroke with residual impairments in speech production underwent high-resolution anatomic MRI and a battery of cognitive and language tests. Impairment was assessed using 3 functional measures of spontaneous speech (eg, rate, informativeness, and overall efficiency) as well as naming ability. To quantitatively analyze the relationship between impairment scores and lesion load along the 3 fiber tracts, we calculated tract-lesion overlap volumes for each patient using probabilistic maps of the tracts derived from diffusion tensor images of 10 age-matched healthy subjects. RESULTS: Regression analyses showed that arcuate fasciculus lesion load, but not extreme capsule or uncinate fasciculus lesion load or overall lesion size, significantly predicted rate, informativeness, and overall efficiency of speech as well as naming ability. CONCLUSIONS: A new variable, arcuate fasciculus lesion load, complements established voxel-based lesion mapping techniques and, in the future, may potentially be used to estimate impairment and recovery potential after stroke and refine inclusion criteria for experimental rehabilitation programs.

Lesion load of the corticospinal tract predicts motor impairment in chronic stroke.

BACKGROUND AND PURPOSE: Previous studies have shown motor impairment after a stroke relates to lesion size and location, but unexplained variability in recovery still exists. In this study, we used lesion-mapping techniques in combination with diffusion tensor imaging to quantitatively test the hypothesis that motor recovery in patients with chronic stroke is inversely related to the proportion of the corticospinal tract (CST) affected by the lesion. METHODS: We studied 50 patients with chronic stroke, all of whom presented with moderate to severe motor impairments in the acute stage, using high-resolution anatomic MRI. We evaluated the degree of motor impairment with the Upper Extremity module of the Fugl-Meyer Assessment. To analyze the relationship between CST damage and impairment scores, we calculated a CST-lesion load for each patient by overlaying the patient's lesion map with a probabilistic tract derived from diffusion tensor images of age-matched healthy subjects. RESULTS: CST-lesion load was a significant predictor of motor deficit. Infarct size, despite correlating with motor scores, did not significantly predict impairment. CONCLUSIONS: Our results show the degree of functional motor deficit after a stroke is highly dependent on the overlap of the lesion with the CST and not lesion size per se. In the future, automated calculation of CST-lesion load may allow more precise prediction of motor impairment after stroke.

The role of low-energy electrons in the high-energy radiolysis of condensed CF3I.

The dynamics of electron-induced reactions in condensed trifluoroiodomethane (CF3I) were studied under ultrahigh vacuum conditions. Seven CF3I radiolysis products (C2F6, C2F5I, C2F3I, CF2I2, C2F4I2, CFI3 and C2F3I3) were identified using temperature-programmed desorption experiments conducted after irradiation with 4 eV electrons. Although C2F6 formation at energies above 4 eV is ascribed to electron-induced electronic excitation followed by prompt dissociation of the C-I bond to form [Formula: see text] radicals that dimerize, the formation of the other six radiolysis products at low sub-ionization incident electron energies is attributed to dissociative electron attachment (DEA) because of the observed resonance peaks in the radiolysis product yields as functions of incident electron energy (∼2 to ∼ 7 eV). All seven CF3I electron-induced reaction products were also identified following irradiation with 500 eV electrons. While dissociative electron attachment and/or electron impact excitation may play an important role in the high-energy radiation-induced synthesis of the high-yield product C2F6, a dramatic enhancement of up to ∼ 2 × 10(4) in product yield per electron at 500 eV relative to that at 4 eV for some products suggests, however, that DEA is not the dominant mechanism for the high-energy radiation-induced synthesis of those products.