Suicide-Specific Training Experiences and Needs Among Military Mental Health Providers.

BACKGROUND: Military suicide rates have risen over the past two decades, with a notable spike in recent years. To address this issue, military mental health providers must be equipped with the skills required to provide timely and effective care; yet little is known about the suicide-specific training experiences or needs of these professionals. METHODS: Thirty-five mental health care providers who treat active duty personnel at military treatment facilities participated in this mixed-methods study. All participants completed a survey assessing training and clinical experiences, comfort and proficiency in working with patients at risk for suicide, and perceived barriers to obtaining suicide-specific training. A sub-set of participants (n = 8) completed a telephone interview to further describe previous experiences and perceived challenges to obtaining training. RESULTS: The majority of participants (79.4%) had 6+ years of clinical experience, had a patient who had attempted suicide (85.3%), and completed at least one suicide-related training since finishing their education (82.4%). Survey results showed the leading barrier to enrolling in suicide-specific trainings was perceived lack of training opportunities (40.7% reported it was a barrier "quite often" or more), followed by lack of time (25%). Interview results revealed lack of time, location and logistical issues, and low perceived need for additional training among providers could impede enrollment. CONCLUSIONS: Study results identified several modifiable barriers to receiving suicide-specific continuing education among military mental health providers. Future efforts should develop accessible training programs that can be easily integrated into routine clinical operations to mount the best defense against suicide. HIGHLIGHTSMilitary mental health providers report significant experience and relatively high degrees of comfort and proficiency working with patients at high risk for suicide.Most providers reported receiving training in suicide assessment and screening; few reported prior training in management of suicidality.Study results identified several modifiable barriers to receiving suicide-prevention continuing education among military mental health care providers; future efforts should seek to develop accessible training programs that can be easily integrated into routine clinical operations to mount the best defense against suicide.

Multishell Diffusion MRI-Based Tractography of the Facial Nerve in Vestibular Schwannoma.

BACKGROUND AND PURPOSE: Tractography of the facial nerve based on single-shell diffusion MR imaging is thought to be helpful before surgery for resection of vestibular schwannoma. However, this paradigm can be vitiated by the isotropic diffusion of the CSF, the convoluted path of the facial nerve, and its crossing with other bundles. Here we propose a multishell diffusion MR imaging acquisition scheme combined with probabilistic tractography that has the potential to provide a presurgical facial nerve reconstruction uncontaminated by such effects. MATERIALS AND METHODS: Five patients scheduled for vestibular schwannoma resection underwent multishell diffusion MR imaging (b-values = 0, 300, 1000, 2000 s/mm2). Facial nerve tractography was performed with a probabilistic algorithm and anatomic seeds located in the brain stem, cerebellopontine cistern, and internal auditory canal. A single-shell diffusion MR imaging (b-value = 0, 1000 s/mm2) subset was extrapolated from the multishell diffusion MR imaging data. The quality of the facial nerve reconstruction based on both multishell diffusion MR imaging and single-shell diffusion MR imaging sequences was assessed against intraoperative videos recorded during the operation. RESULTS: Single-shell diffusion MR imaging-based tractography was characterized by failures in facial nerve tracking (2/5 cases) and inaccurate facial nerve reconstructions displaying false-positives and partial volume effects. In contrast, multishell diffusion MR imaging-based tractography provided accurate facial nerve reconstructions (4/5 cases), even in the presence of ostensibly complex patterns. CONCLUSIONS: In comparison with single-shell diffusion MR imaging, the combination of multishell diffusion MR imaging-based tractography and probabilistic algorithms is a more valuable aid for surgeons before vestibular schwannoma resection, providing more accurate facial nerve reconstructions, which may ultimately improve the postsurgical patient's outcome.

N2pc reflects two modes for coding the number of visual targets.

Humans share with a variety of animal species the spontaneous ability to detect the numerical correspondence between limited quantities of visual objects and discrete auditory events. Here, we explored how such mental representation is generated in the visual modality by monitoring a parieto-occipital ERP component, N2pc, whose amplitude covaries with the number of visual targets in explicit enumeration. Participants listened to an auditory sequence of one to three tones followed by a visual search display containing one to three targets. In Experiment 1, participants were asked to respond based on the numerical correspondence between tones and visual targets. In Experiment 2, participants were asked to ignore the tones and detect a target presence in the search display. The results of Experiment 1 showed an N2pc amplitude increase determined by the number of visual targets followed by a centroparietal ERP component modulated by the numerical correspondence between tones and visual targets. The results of Experiment 2 did not show an N2pc amplitude increase as a function of the number of visual targets. However, the numerical correspondence between tones and visual targets influenced N2pc amplitude. By comparing a subset of amplitude/latency parameters between Experiment 1 and 2, the present results suggest N2pc reflects two modes for representing the number of visual targets. One mode, susceptible to subjective control, relies on visual target segregation for exact target individuation, whereas a different mode, likely enabling spontaneous cross-modal matching, relies on the extraction of rough information about number of targets from visual input.

Sparing from the attentional blink is not spared from structural limitations.

When a series of three successive to-be-reported items (targets) is displayed in a rapid serial visual presentation (RSVP) stream of distractors, it has been shown that no attentional blink--a marked impairment in the report of the second of two targets, typically observed when the targets appear within 200-600 ms of one another--occurs in target accuracy. The present study examines three recently introduced computational models that provide different explanations of this protracted sparing effect. Using a standard RSVP design and these models, we provide empirical data and simulations that illustrate that structural limitations affect the processing of successive targets. In addition, we compare the candidate mechanisms that might underlie these limitations.

A methodology to improve estimation of stimulus-evoked hemodynamic response from fNIRS measurements.

Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical neuroimaging method used to investigate functional activity of the cerebral cortex evoked by cognitive, visual, auditory and motor tasks, detecting regional changes of oxy- and deoxy-hemoglobin concentration. Accurate estimation of the stimulus-evoked hemodynamic response (HR) from fNIRS signals in order to quantitatively investigate cognitive functions requires to cope with several noise components. Some of them appear as random disturbances (typically tackled through averaging techniques), while others are due to physiological sources, such as heart beat, respiration, vasomotor waves, and are particularly challenging to be dealt with because they lie in the same frequency band of HR. In this work we present a new two-steps methodology for the HR estimation from fNIRS data. The first step is a pre-processing stage where physiological trends in fNIRS data are reduced by exploiting a mathematical model identified from the signal of a reference channel. In the second step, the pre-processed data of the other channels are filtered with a recently presented non-parametric Bayesian approach (Scarpa et al., Optics Express, 2010). The presented method for HR estimation is compared with widely used methods: conventional averaging, band-pass filtering and principal component analysis (PCA). Results on simulated data reveal the ability of the proposed method to improve the accuracy of the estimates of the functional hemodynamic response, as well as the estimate of peak amplitude and latency. Encouraging preliminary results in a representative real data set showing an improvement of contrast to noise ratio are also reported.

Bayesian filtering of human brain hemodynamic activity elicited by visual short-term maintenance recorded through functional near-infrared spectroscopy (fNIRS).

Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique that measures changes in oxy-hemoglobin (ΔHbO) and deoxy-hemoglobin (ΔHbR) concentration associated with brain activity. The signal acquired with fNIRS is naturally affected by disturbances engendering from ongoing physiological activity (e.g., cardiac, respiratory, Mayer wave) and random measurement noise. Despite its several drawbacks, the so-called conventional averaging (CA) is still widely used to estimate the hemodynamic response function (HRF) from noisy signal. One such drawback is related to the number of trials necessary to derive stable HRF functions adopting the CA approach, which must be substantial (N >> 50). In this work, a pre-processing procedure to remove artifacts followed by the application of a non-parametric Bayesian approach is proposed that capitalizes on a priori available knowledge about HRF and noise. Results with the proposed Bayesian approach were compared with CA and with a straightforward band-pass filtering approach. On simulated data, a five times lower estimation error on HRF was obtained with respect to that obtained by CA, and 2.5 times lower than that obtained by band pass filtering. On real data, the improvement achieved by the present method was attested by an increase in the contrast to noise ratio (CNR) and by a reduced variability in single trial estimation. An application of the present Bayesian approach is illustrated that was optimized to monitor changes in hemodynamic activity reflecting variations in visual short-term memory load in humans, which are notoriously hard to detect using functional magnetic resonance imaging (fMRI). In particular, statistical analyses of HRFs recorded during a memory task established with high reliability the crucial role of the intraparietal sulcus and the intra-occipital sulcus in posterior areas of the human brain in visual short-term memory maintenance.

The picture-word interference effect is not a Stroop effect.

A psychological refractory period (PRP) paradigm was used to isolate the locus of the picture-word interference effect along the chain of processes subtended in name production. Two stimuli were presented sequentially on each trial, separated by a varying stimulus onset asynchrony (SOA). The first stimulus, SI, was a tone that required a manual response. The second stimulus, S2, was a picture-word stimulus associated with picture naming. The distractor word was conceptually related to the picture on half of the trials, and unrelated in the other trials. A picture-word interference effect was found at long SOA, but not at short SOA. Such underadditive interaction between SOA and semantic relatedness suggests strongly that the locus of the picture-word interference effect is functionally earlier than the PRP effect locus. The results are discussed in relation to models of word production suggesting the involvement of central mechanisms in the selection of lexical output.

Semantic and repetition priming within the attentional blink: an event-related brain potential (ERP) investigation study.

An attentional blink (AB) paradigm was used to directly compare semantic and repetition priming for reported words versus missed words. Three target words (T1, T2, T3) were embedded in a rapidly presented stream of non-word distractors for report at the end of each trial. Whereas T1 was not related to either T2 or T3, T2 and T3 could be unrelated words, semantically related words, or identical. Semantic and repetition priming effects were evident in both behavioral and electrophysiological measures on T3, whether T2 was accurately reported or 'blinked'. These results suggest that semantic and repetition priming effects, under rapid serial visual presentation conditions, are modulated by at least partially overlapping neural mechanisms.

The interdependence of spatial attention and lexical access as revealed by early asymmetries in occipito-parietal ERP activity.

A test of the possible functional interaction between mechanisms subserving spatial attention and lexical access was devised by displaying one green and one red string of letters, one to the left and one to the right of fixation, and having participants attend to a target string defined by color while ignoring the other distractor string. The target string for a delayed lexical decision task could be a word or a nonword. The distractor was always a word. When the target was a word, target and distractor were associatively related on half of the trials and not related in the other trials. The event-related potential time-locked to the onset of the letter strings produced an N2pc (a greater negativity at scalp sites contralateral to the target relative to the ipsilateral sites arising at about 170 ms poststimulus). N2pc amplitude was reduced when the words were related relative to when they were not related. The results provide direct, online evidence that the rapid activation of meaning by visual words can influence the efficiency of the deployment of spatial attention.

P3 latency shifts in the attentional blink: further evidence for second target processing postponement.

A rapid serial visual presentation technique was used to display sequentially two targets, T1 and T2, and monitor P3 amplitude and latency variations associated with the attentional blink (AB) effect. A red T1 digit was embedded on each trial in a sequence of black letters. T2 was either masked by a trailing stimulus or not masked. T1 had to be identified on a proportion of trials, or ignored in other trials. T2 was the black letter 'E' on 20% of the trials, or any other non-'E' black letter in the other 80% of the trials. A delayed 'E' detection task was required at the end of each trial. An AB was observed when T1 had to be reported and T2 was masked. The AB effect was associated with a sizable amplitude reduction of the P3 component time locked to T2 onset. When T2 was not masked, no AB or P3 amplitude variations were observed. When T1 had to be reported, a delayed P3 peak latency was observed at short compared to long T1-T2 intervals. No effect of T1-T2 interval was observed on the T2-locked P3 peak latency when T1 could be ignored. Taken together these findings provide converging evidence in support of temporal attention models bridging behavior and electrophysiology that postulate a direct link between the cause of the AB effect and the sources of both amplitude and latency variations in the T2-locked P3 component.

Spatial attention freezes during the attention blink.

A variant of the rapid serial visual presentation paradigm was used to display sequentially two lateral sequences of stimuli, one to the left and one to the right of fixation, embedding two pairs of target stimuli, T1 and T2. T1 was composed of a pair of alphanumeric characters, and subjects had either to ignore T1 or to encode T1 for a delayed response. T2 was a lateral square of a prespecified color. The square had a small gap in one side, and the task for this stimulus was to report which side had the gap. When subjects were required to ignore T1, the T2-locked ERP produced a clear N2pc, that is, a greater negativity at electrode sites contralateral to the position occupied by T2. This N2pc was followed by a sustained posterior contralateral negativity (SPCN). When subjects were required to monitor T1 in addition to T2, both the N2pc and the SPCN components amplitude depended on the difficulty of the task associated with T1. If T1 was composed of digits that had to be encoded for a delayed same/different judgment, both the N2pc and the SPCN components were entirely suppressed. Although attenuated, such components were present when T1 was composed of a pair of symbols that subjects could disregard. The results suggest that a set of mechanisms subserving the allocation of attention in the spatial domain, resulting in the N2pc, suffer significant interference from concurrent cognitive operations required to encode information into visual short-term memory.

Central processing overlap modulates P3 latency.

Two experiments examined the issue of the functional mechanisms exerting a modulatory effect on the latency of the P3. In experiment 1, using a psychological refractory period (PRP) paradigm, two sequential stimuli (T(1) and T(2)) were presented in each trial at varying stimulus onset asynchronies (SOAs), each requiring a speeded choice response. Substantial lengthening of the reaction time to T(2) was observed as SOA decreased (i.e., PRP effect). A systematic investigation of the T(2)-locked P3 component amplitude and latency was undertaken to discover whether either of these P3 parameters was correlated with the PRP effect. The results showed lengthening of the T(2)-locked P3 component latency as SOA was decreased, and, across subjects, a positive correlation between the PRP effect and P3 latency lengthening. No SOA-dependent P3 amplitude variation was observed. In experiment 2, the P3 component was measured under single-task conditions. P3 amplitude was higher under single-task than under dual-task conditions, but no SOA-dependent latency variations were observed in this experiment. Overall, the results of both experiments support the notion that part of the processing reflected in P3 activity occurs at or after the locus of the PRP effect, thus suggesting strongly that central mechanisms are involved in P3 latency variations.

Unitary attention in callosal agenesis.

The interhemispheric organisation of two specific components of attention was investigated in three patients affected by partial or complete agenesis of the corpus callosum. A visuospatial component of attention was explored using a visual search paradigm in which target and distractors were displayed either unilaterally within a single visual hemifield, or bilaterally across both visual hemifields in light of prior work indicating that split-brain patients were twice as fast to scan bilateral displays compared to unilateral displays. A central component of attention was explored using a psychological refractory period (PRP) paradigm in which two visual stimuli were presented laterally at various stimulus onset asynchronies (SOAs), with each stimulus associated with a different speeded two-alternative choice task. The stimulus-response compatibility in the second task was systematically manipulated in this paradigm, in light of prior work indicating that split-brain patients exhibited a close-to-normal PRP effect (i.e., slowing of the second response as SOA is decreased), with, however, abnormally decreasing effects of the manipulation of the response mapping on the second task speed as SOA was decreased. The present results showed that, although generally slower than normals in carrying out the two tasks, the performance of each of the three acallosal patients was formally equivalent to the performance of a matched control group of normal individuals. In the visual search task, the search rate of the acallosal patients was the same for unilateral and bilateral displays. Furthermore, in the PRP task, there was more mutual interference between the lateralised tasks for the acallosal patients than that evidenced in the performance of the matched control group. It is concluded that the visuospatial component and the central component of attention in agenesis of the corpus callosum are interhemispherically integrated systems.

Electrophysiological evidence of visual encoding deficits in a cross-modal attentional blink paradigm.

Two experiments are reported in which two target stimuli, T1 and T2, were presented at variable stimulus onset asynchronies (SOAs). In Experiment 1, T1 and T2 were visual stimuli embedded in a rapid serial visual presentation (RSVP) stream of distractors. Participants were asked to report T1 and T2 at the end of the stream. In Experiment 2, T1 was an auditory stimulus, and T2 a visual stimulus embedded in an RSVP stream. Participants made a speeded discriminative response to T1, and reported T2 at the end of the stream. An attentional blink (AB) effect was observed in both experiments: T2 report suffered at short SOA compared to long SOA. During the AB, the amplitude of the P300 component of the event-related potential (ERP) locked to T2 onset was sensibly reduced in both experiments. Behavioral and ERP results were very similar across the two experiments. Implications for models of the AB effect are discussed.

Four-dot masking produces the attentional blink.

When two target stimuli (T1 and T2) are presented sequentially within half a second of each other, identification accuracy is often poor for T2. This phenomenon, known as attentional blink (AB), can be observed generally only if the stimulus terminating the presentation of T2 acts as an interruption mask. Recent evidence suggests that even four small dots surrounding a target item can exert masking effects, provided the target onset occurs at an unattended spatial location. In order to test whether an AB could be observed under conditions of four-dot masking of T2, five rapid serial visual presentation streams of letters were synchronously displayed on each trial of the present experiment. T1 and T2 were digits presented at unpredictable locations and unpredictable temporal intervals. T2 was followed by either a blank field, a letter, or four-dots. No AB was observed when T2 was not masked, but robust and equally sized ABs were observed when T2 was followed by both the letter mask and the four-dots.

Cross-modal attentional deficits in processing tactile stimulation.

In order to substantiate recent theorization on the possible links between the causes of the attentional blink and the psychological refractory period phenomena (e.g., Jolicoeur, 1999a), four experiments are reported in which two target stimuli, T1 and T2, were presented in different modalities at varying stimulus onset asynchronies (SOAs), with each stimulus being associated with a distinct task, Task1 and Task2. In Experiment 1, T1 was a tone, and Task1 was a speeded vocal response based on pitch. T2 was a brief press applied to either of two distal fingerpads, and Task2 was a speeded manual response based on tactile stimulus location. In Experiment 2, the same T1 as that used in Experiment 1 was presented, and in Task1 the subject either made a speeded vocal response based on pitch or ignored T1. T2 was a masked tactile stimulation, and Task2 was an unspeeded manual discrimination of the tactile stimulation location. This Task2 was maintained in Experiments 3 and 4. The auditory T1 was replaced with a white digit embedded in a rapid serial visualization presentation of a stream of black letters, and in Task1 the subject either made an unspeeded decision based on T1 identity or ignored T1. In all the experiments, the results showed an SOA-locked impairment in Task2. As SOA was decreased, reaction times in the speeded Task2 of Experiment 1 increased, and accuracy in the unspeeded Task2 of Experiments 2-4 decreased. The SOA-locked impairment was almost eliminated when T1 could be ignored or was absent. The results are discussed in terms of central processing limitations as the cause of such effects.

Selective effect of closed-head injury on central resource allocation: evidence from dual-task performance.

Two dual-task experiments are reported bearing on the issue of slower processing time for severe chronic closed-head injury (CHI) patients compared to matched controls. In the first experiment, a classical psychological refractory period (PRP) paradigm was employed, in which two sequential stimuli, a pure tone and a colored dot, were presented at variable stimulus onset asynchronies (SOAs), each associated with a distinct task. The task on the tone required a speeded vocal response based on pitch, and the task on the colored dot required a speeded manual response based on color. In the second experiment, either one or three masked letters was presented, followed by a pure tone at variable SOAs. The task on the letters required a delayed report of the letters at the end of each trial. The task on the tone required an immediate manual response based on pitch. In both experiments, both CHI patients and matched controls reported an SOA-locked slowing of the speeded response to the second stimulus, a PRP effect. The PRP effect was more substantial for CHI patients than for matched controls, suggesting that a component of the slower processing time for CHI patients was related to a selective increase in temporal demands for central processing of the stimuli.

Selective influence of second target exposure duration and task-1 load effects in the attentional blink phenomenon.

The purpose of the experiments was to constrain the locus of interference in the attentional blink (AB) paradigm. Two visual stimuli, T1 and T2, were shown 300 msec apart, and each was followed by a mask. T1 was an "H," an "S," an "&," or a blank field; T2 consisted of five letters. In Task1, blank fields and & characters could be ignored, whereas Hs and Ss had to be identified and reported. Task2 was always to report as many letters as possible from T2. Task2 performance was lower when T1 had to be reported, as expected from the attentional blink phenomenon (AB). The exposure duration of T2 was also manipulated. More letters could be reported as exposure duration was increased. However, this effect was additive with manipulations of Task1 processing load that produced the AB effect. Log-linear analyses assuming that effects of T2 exposure duration and Task1 load effects occur at functionally distinct stages of processing provided satisfactory fits to the results, suggesting that none of the AB effect occurs as early as those of T2 exposure duration. The results suggest that the locus of the AB effect is later than the stage(s) of processing affected by exposure duration.

Visual encoding of patterns is subject to dual-task interference.

Two stimuli were presented at varying stimulus onset asynchronies (SOAs), with each stimulus associated with a distinct task. The first stimulus was a tone at one of either two or three frequencies. In two conditions, the task associated with a tone was either a speeded two-alternative discrimination (2AD), or a speeded three-alternative discrimination (3AD) based on the pitch of the tone. In a third condition, subjects were told to ignore the tone. The second stimulus was a briefly exposed study matrix of red and black squares followed by a mask. After a fixed delay, the mask was replaced by a test matrix that was either the same or different from the study matrix. The task associated with the matrices was to indicate, with no speed pressure, whether the study matrix and the test matrix were the same or different. Results from each speeded AD condition showed that subject's accuracy in the matrix task decreased as the SOA between the tone and the study matrix decreased. This effect was larger for the 3AD tone task than with a 2AD tone task. In addition, within each speeded AD condition, longer RTs in the tone task were associated with lower accuracy in the matrix task. None of these effects was evident when the subjects were told to ignore the tone. These results suggest that encoding visual information can be subject to significant capacity limitations imposed by cross-modal multitasking.