The neurophysiology of human biological motion processing: a high-density electrical mapping study

The neural processing of biological motion (BM) is of profound experimental interest since it is often through the movement of another that we interpret their immediate intentions. Neuroimaging points to a specialized cortical network for processing biological motion. Here, high-density electrical mapping and source-analysis techniques were employed to interrogate the timing of information processing across this network. Participants viewed point-light-displays depicting standard body movements (e.g. jumping), while event-related potentials (ERPs) were recorded and compared to ERPs to scrambled motion control stimuli. In a pair of experiments, three major phases of BM-specific processing were identified: 1) The earliest phase of BM-sensitive modulation was characterized by a positive shift of the ERP between 100 and 200 ms after stimulus onset. This modulation was observed exclusively over the right hemisphere and source-analysis suggested a likely generator in close proximity to regions associated with general motion processing (KO/hMT). 2) The second phase of BM-sensitivity occurred from 200 to 350 ms, characterized by a robust negative-going ERP modulation over posterior middle temporal regions bilaterally. Source-analysis pointed to bilateral generators at or near the posterior superior temporal sulcus (STS). 3) A third phase of processing was evident only in our second experiment, where participants actively attended the BM aspect of the stimuli, and was manifest as a centro-parietal positive ERP deflection, likely related to later cognitive processes. These results point to very early sensory registration of biological motion, and highlight the interactive role of the posterior STS in analyzing the movements of other living organisms.     

Task switching: a high-density electrical mapping study

Flexibly switching between tasks is one of the paradigmatic functions of so-called "executive control" processes. Neuroimaging studies have implicated both prefrontal and parietal cortical regions in the processing necessary to effectively switch task. Beyond their general involvement in this critical function, however, little is known about the dynamics of processing across frontal and parietal regions. For instance, it remains to be determined to what extent these areas play a role in preparing to switch task before arrival of the stimulus to be acted upon and to what extent they play a role in any switching processes that occur after the stimulus is presented. Here, we used the excellent temporal resolution afforded by high-density mapping of brain potentials to explore the time course of the processes underlying (1) the performance of and (2) the preparation for a switch of task. We detail the contributions of both frontal and parietal processes to these two aspects of the task-switching process. Our data revealed a complex pattern of effects. Most striking was a period of sustained activity over bilateral parietal regions preceding the switch trial. Over frontal regions, activity actually decreased during this same period. Strongest sustained frontal activity was in fact seen for trials on which no switch was required. Further, we find that the first differential activity associated with switching task was over posterior parietal areas (220 ms), whereas over frontal scalp, the first differential activity is found more than 200 ms later. These and other effects are interpreted in terms of a "competition" model in which preparing to switch task is understood as the beginning of a competition between the potentially relevant tasks that is resolved during the switch trial. Our findings are difficult to account for with models that posit a strong role for frontal cortical regions in "reconfiguring" the system during switches of task.     

The chronoarchitecture of human sexual desire: a high-density electrical mapping study

Recent neuroimaging research suggests that human sexual desire (SD) recruits both the limbic system and higher-order cognitive brain areas. Because of the temporal limitation of this technique, the chronoarchitecture of SD remains however unresolved. Here, we investigated the spatio-temporal dynamics of SD by combining a behavioral desire decision task with high-density visual event-related potential (VEP) recordings and brain source estimations. VEPs were recorded from thirteen healthy participants when presented with pictures from two different stimulus categories (i.e., high and low desirability). In agreement with the literature, behavioral results showed that participants were faster to rate non-desired stimuli than desired stimuli (p=0.028). Electrophysiological results extended these behavioral data. Group-averaged VEPs peaked at 90 to 140 ms (P100), at 142 to 220 ms (N200), and at 222 to 360 ms (P300). Desired stimuli (DS) were distinguished from non-desired stimuli (NDS) over the N200 period, notably from 142 to 187 ms. Over this time period, DS processing was characterized by a significant scalp potential field. Although both conditions (DS and NDS) showed the recruitment of the occipito-temporal region (including the extrastriate body area, EBA), LAURA source estimation of the DS scalp potential field revealed a more right-lateralized current source density maximum in the posterior superior temporal sulcus (STS) extending to the temporo-parietal junction (TPJ). The recruitment of STS and TPJ for desired stimuli indicates that these brain areas, known to be respectively involved in social cognition, attention, integration of body-related information and self-processing, play a crucial role for the coding of desirability of visual sexual human stimuli within the first 200 ms after stimulus onset. These findings support the hypothesis that complex cognitive processing for desire occurs much faster than previously thought and open new perspectives with respect to the role of both bottom-up and top-down mechanisms in visual processing of sexual stimuli.     

Neurophysiological markers of alert responding during goal-directed behavior: a high-density electrical mapping study

The ability to dynamically modulate the intensity of sustained attention (i.e., alertness) is an essential component of the human executive control system, allowing us to function purposefully in accordance with our goals. In this study we examine high-density ERP markers of alert responding during the fixed sequence sustained attention to response task (SART(fixed)). This paradigm has proven to be a sensitive clinical metric in patient populations with deficits in their ability to sustain attention (e.g., attention deficit hyperactivity disorder). In this task subjects withhold a button press to an infrequent no-go target ('3') embedded within a predictable sequence of numbers ('1' to '9'). Our data reveal a complex pattern of effects across the trial sequence of the SART, with clear contributions from frontal and parietal cortices to sustained attentional performance. Over occipito-parietal regions, early visual attention processes were increased during trial 2 (i.e., trial in which the digit '2' was presented) and trial 3, giving rise to the so-called selection negativity (SN). Two prominent late components were manifest during trial 2: LP1 (550-800 ms) and LP2 (850-1150 ms) over occipito-parietal and central sites. We interpret the LP1 component on trial 2 as reflecting retrieval of the task goal and the subsequent LP2 as reflecting competition between the currently relevant go response and the subsequent no-go response. On trial 3, an enhanced "no-go N2" (250-450 ms) was seen fronto-centrally in the absence of the "no-go P3" that typically follows. Fronto-polar activity was also seen across all trials and may be indicative of subgoal processes to integrate the association between stimulus and goal. Prior to a lapse of attention (i.e., failure to inhibit a response to "3") the LP1 was significantly attenuated on the preceding trial 2 indicating a failure of anticipatory goal-directed processing. The results are discussed in terms of models of sustained attention involving frontal and parietal cortices.     

Right hemisphere control of visuospatial attention: line-bisection judgments evaluated with high-density electrical mapping and source analysis

The "line-bisection" task has proven an especially useful clinical tool for assessment of spatial neglect syndrome in neurological patients. Here, we investigated the neural processes involved in performing this task by recording high-density event-related potentials from 128 scalp electrodes in normal observers. We characterized a robust net negative potential from 170-400 ms poststimulus presentation that correlates with line-bisection judgments. Topographic mapping shows three distinct phases to this negativity. The first phase (approximately 170-190 ms) has a scalp distribution exclusively over the right parieto-occipital and lateral occipital scalp, consistent with generators in the region of the right temporo-parietal junction and right lateral occipital cortices. The second phase (approximately 190-240 ms) sees the emergence of a second negative focus over the right central parietal scalp, consistent with subsequent involvement of right superior parietal cortices. In the third phase (approximately 240-400 ms), the topography becomes dominated by this right central parietal negativity. Inverse source modeling confirmed that right hemisphere lateral occipital, inferior parietal, and superior parietal regions were the likeliest generators of the bulk of the activity associated with this effect. The line stimuli were also presented at three contrast levels (3, 25, and 100%) in order to manipulate both the latency of stimulus processing and the relative contributions from magnocellular and parvocellular inputs. Through this manipulation, we show that the line-bisection effect systematically tracks/follows the latency of the N1 component, which is considered a temporal marker for object processing in the ventral visual stream. This pattern of effects suggests that this task invokes an allocentric (object-based) form of visuospatial attention. Further, at 3% contrast, the line-bisection effect was equivalent to the effects seen at higher contrast levels, suggesting that parvocellular inputs are not necessary for successful performance of this task.     

Visual perceptual learning in human object recognition areas: a repetition priming study using high-density electrical mapping

It is often the case that only partial or degraded views of an object are available to an observer, and yet in many of these cases, object recognition is accomplished with surprising ease. The perceptual filling-in or "closure" that makes this possible has been linked to a group of object recognition areas in the human brain, the lateral occipital (LO) complex, and has been shown to have a specific electrophysiological correlate, the N(cl) component of the event related potential. Perceptual closure presumably occurs because repeated and varied exposure to different classes of objects has caused the brain to undergo "perceptual learning," which promotes a robust mnemonic representation, accessible under partial information circumstances. The present study examined the impact of perceptual learning on closure-related brain processes. Fragmented pictures of common objects were presented, such that information content was incrementally increased until just enough information was present to permit closure and object recognition. Periodic repetition of a subset of these picture sequences was used to induce repetition priming due to perceptual learning. This priming has an electrophysiological signature that is putatively generated in the LO complex, but significantly precedes the electrophysiological correlate of closure. The temporal progression of priming- and closure-related activity in the LO complex supports the view that sensory processing entails multiple reentrant stages of activity within processing modules of the visual hierarchy. That the earliest priming-related activity occurs over LO complex, suggests that the sensory trace itself may reside in these object recognition areas.     

Spatiotemporal dynamics of human object recognition processing: an integrated high-density electrical mapping and functional imaging study of "closure" processes

Humans are capable of recognizing objects, often despite highly adverse viewing conditions (e.g., occlusion). The term "perceptual closure" has been used to refer to the neural processes responsible for "filling-in" missing information in the visual image under such conditions. Closure phenomena have been linked to a group of object recognition areas, the so-called lateral-occipital complex (LOC). Here, we investigated the spatiotemporal dynamics of perceptual closure processes by coregistering data from high-density electrical recordings (ERPs) and functional magnetic resonance imaging (fMRI) while subjects participated in a perceptual closure task. Subjects were presented with highly fragmented images and control scrambled images. Fragmented images were calibrated to be 'just' recognizable as objects (that is, perceptual closure was necessary), whereas the scrambled images were unrecognizable. Comparison of responses to these two stimulus classes revealed the neural processes underlying perceptual closure. fMRI revealed an object recognition system that mediates these closure processes, the core of which consists of the LOC regions. ERP recordings resulted in the well-characterized N(CL) component (for negativity associated with closure), a robust relative negativity over bilateral occipito-temporal scalp that occurs in the 230-400 ms timeframe. Our investigations further revealed an extended network of dorsal and frontal regions, also involved in perceptual closure processes. Inverse source analysis showed that the major generators of N(CL) localized to the identical regions within LOC revealed by the fMRI recordings and detailed the temporal dynamics across these LOC regions including interactions between LOC and these other nodes of the object recognition circuit.     

Segregated processing of auditory motion and auditory location: an ERP mapping study

Recent studies have revealed a distinct cortical network activated during the analysis of sounds' spatial properties. Whether common brain regions in this auditory where pathway are involved in both auditory motion and location processing is unresolved. We investigated this question with multichannel auditory evoked potentials (AEPs) in 11 subjects. Stimuli were binaural 500-ms white noise bursts. Interaural time differences (ITD) created the sensation of moving or stationary sounds within each auditory hemifield, and subjects discriminated either their position or direction of motion in a blocked design. Scalp potential distributions (AEP maps) differentiated electric field configurations across stimulus classes. The initial approximately 250-ms poststimulus yielded common topographies for both stimulus classes and hemifields. After approximately 250-ms, moving and stationary sounds engaged distinct cortical networks at two time periods, again with no differences observed between hemifields. The first ( approximately 250- to 350-ms poststimulus onset) was during stimulus presentation, and the second ( approximately 550- to 900-ms poststimulus onset) occurred after stimulus offset. Distributed linear inverse solutions of the maps over the 250- to 350-ms time period revealed not only bilateral inferior frontal activation for both types of auditory spatial processing, but also strong right inferior parietal activation in the case of auditory motion discrimination. During the later 550-to 900-ms time period, right inferior parietal and bilateral inferior frontal activity was again observed for moving sounds, whereas strong bilateral superior frontal activity was seen in the case of stationary sounds. Collectively, the evidence supports the existence of partly segregated networks within the auditory where pathway for auditory location and auditory motion processing.     

Therapist effects in substance abuse treatment: a naturalistic study

Objective: The purpose of this naturalistic study was to investigate between-therapist variation in the working alliance, treatment effectiveness and client satisfaction.

Methods: The subjects were Finnish outpatients (N = 327) with various substance use disorders and their therapists (N = 33). The clients were randomly assigned to the therapists, and they were followed-up for 6 months. Regression analyses with mixed models were used.

Results: The findings indicated that between-therapist variation was wider in the therapists’ ratings of the alliance than in the clients’ ratings. The therapist effect was present at follow-up in prolonged abstinence period and client satisfaction with the therapist. According to the clients’ ratings of the alliance and post-treatment satisfaction, the therapist effect on satisfaction in general increased as treatment progressed. The therapists’ and clients’ ratings of the alliance differed significantly from each other, the clients’ ratings being more positive than the therapists’ ratings, although correlations showed that they were significantly interrelated.

Conclusions: It can be concluded that the size of the therapist effect varied with regard to the treatment aspects measured.     

Duration of untreated illness in major depressive disorder: a naturalistic study

BACKGROUND: Most of the studies on the duration of untreated illness (DUI) as a possible predictor of the clinical outcome and the course have focused on the psychotic disorders. The present naturalistic study was aimed to evaluate the possible relationship between the DUI and some clinical characteristics of a sample of patients with major depressive disorder (MDD). METHODS: Sixty-eight patients with MDD, according to the Diagnostic and Statistical Manual of Mental Disorders, IV Edition, Text Revision (DSM-IV-TR) criteria, followed-up for 4 years, were selected, interviewed and their clinical charts reviewed. The DUI was defined as the interval between the onset of the first major depressive episode and the first adequate antidepressant treatment. The sample was divided in two groups according to a DUI 12 months (n = 23). The main demographic and clinical course variables were compared between the two groups using t-tests or chi-squared tests. RESULTS: Patients with a DUI > 12 months were more frequently women (chi2 = 4.005, p = 0.045), had an earlier onset (t = 2.515, p = 0.014), a longer duration of illness (t = -2.483, p = 0.016), a higher number of recurrences (t = -2.262, p = 0.027) and had more frequently comorbid Axis I disorders with onset later than MDD (chi2 = 5.595, p = 0.05). CONCLUSIONS: These findings suggest that a longer DUI may negatively influence the clinical course of MDD. Further studies on larger samples are warranted to confirm these preliminary results.     

Parallel networks operating across attentional deployment and motion processing: a multi-seed partial least squares fMRI study

Anticipatory deployment of attention may operate through networks of brain areas that modulate the representations of to-be-attended items in advance of their occurrence through top-down control. Luks and Simpson (2004) (Luks, T.L., Simpson, G.V., 2004. Preparatory deployment of attention to motion activates higher order motion-processing brain regions. NeuroImage 22, 1515-1522) found activations in both control areas and sensory areas during anticipatory deployment of attention to visual motion in the absence of stimuli. In the present follow-up analysis, we tested which network activity during anticipatory deployment of attention is functionally connected with task-related network activity during subsequent selective processing of motion stimuli. Following a cue (anticipatory phase), participants monitored a sequence of complex motion stimuli for a target motion pattern (task phase). We analyzed fMR signal using a partial least squares analysis with previously identified cue- and motion-related voxels as seed regions. The method identified two networks that covaried with the activity of seed regions during the cue and motion-stimulus-processing phases of the task. We suggest that the first network, involving ventral intraparietal sulcus, superior parietal lobule and motor areas, is related to anticipatory and sustained visuomotor attention. Operating in parallel to this visuomotor attention network, there is a second network, involving visual occipital areas, frontal areas as well as angular and supramarginal gyri, that may underlie anticipatory and sustained visual attention processes.     

Comparing neural correlates of configural processing in faces and objects: an ERP study of the Thatcher illusion

In the Thatcher illusion, a face with inverted eyes and mouth looks abnormal when upright but not when inverted. Behavioral studies have shown that thatcherization of an upright face disrupts perceptual processing of the local configuration. We recorded high-density EEG from normal observers to study ERP correlates of the illusion during the perception of faces and nonface objects, to determine whether inversion and thatcherization affect similar neural mechanisms. Observers viewed faces and houses in four conditions (upright vs. inverted, and normal vs. thatcherized) while detecting an oddball category (chairs). Thatcherization delayed the N170 component over occipito-temporal cortex to faces, but not to houses. This modulation matched the illusion as it was larger for upright than inverted faces. The P1 over medial occipital regions was delayed by face inversion but unaffected by thatcherization. Finally, face thatcherization delayed P2 over occipito-temporal but not over parietal regions, while inversion affected P2 across categories. All effects involving thatcherization were face-specific. These results indicate that effects of face inversion and feature inversion (in thatcherized faces) can be distinguished on a functional as well as neural level, and that they affect configural processing of faces in different time windows.     

Migraine treatment outcomes with rizatriptan in triptan-naive patients: a naturalistic study.

BACKGROUND: The 5-hydroxytryptamine(1B/1D) agonists, or triptans, are the newest class of drugs to become available for the acute treatment of migraine. The class currently includes sumatriptan, zolmitriptan, naratriptan, and rizatriptan. The efficacy of rizatriptan in the acute treatment of migraine has been established against placebo and other oral triptans in controlled comparative trials. OBJECTIVE: The US Migraine Assessment Protocol (USMAP) collected data on the use of rizatriptan in a naturalistic setting reflecting clinical practice. This paper presents results for patients enrolled in the USMAP study who had never taken a triptan before the study. METHODS: At enrollment, 216 patients completed a questionnaire describing their responses to their current nontriptan medications. They were then given specially packaged samples of 4 standard 10-mg rizatriptan tablets and 4 orally disintegrating 10-mg rizatriptan tablets (wafers) and were asked to take a different formulation for each of their next 2 attacks, the sequence to be at their discretion. Within approximately 24 hours after taking rizatriptan, patients were to call a toll-free number to report their responses to rizatriptan using an interactive voice-response system. RESULTS: Within 2 hours after initial dosing of rizatriptan, significantly more patients taking either the rizatriptan tablet or the rizatriptan wafer reported onset of pain relief, had become largely symptom free, and were able to resume usual activities compared with their baseline responses to nontriptans (P < 0.05). In addition, compared with their baseline responses to nontriptans, significantly more patients taking either rizatriptan formulation had mild or no pain 2 hours after dosing (P < 0.05). More than twice as many patients taking the rizatriptan tablets or wafers were either somewhat or very satisfied with the medication compared with their satisfaction with nontriptans (P < 0.05). CONCLUSIONS: In the naturalistic setting of this study, migraineurs who had not previously taken a triptan medication reported more rapid relief of pain, more effective pain relief, and more rapid resumption of normal activities when taking rizatriptan tablets or wafers than when taking a nontriptan medication. Patients dissatisfied with their current nontriptan migraine therapy may benefit from treatment with rizatriptan.     

Effect of attention on cortical processing of sound motion: an EEG study

The onset of motion in an otherwise continuous sound elicits a prominent auditory evoked potential, the so-called motion onset response (MOR). The MOR has recently been shown to be modulated by stimulus-dependent factors, such as velocity, while the possible role of task-dependent factors has remained unclear. Here, the effect of spatial attention on the MOR was investigated in 19 listeners. In each trial, the subject initially heard a free-field sound, consisting of a stationary period and a subsequent period of motion. Then, two successive stationary test tones were presented that differed in location and pitch. Subjects either judged whether or not the starting and final positions of the preceded motion matched the positions of the two test tones ('motion-focused condition'), or whether or not the test tones were identical in pitch, irrespective of the preceded motion stimulus ('baseline condition'). These two tasks were presented in separate experimental blocks. The performance level in both tasks was similar. However, especially later portions of the MOR were significantly increased in amplitude when auditory motion was task-relevant. Cortical source localization indicated that this extra activation originated in dorsofrontal areas that have been proposed to be part of the dorsal auditory processing stream. These results support the assumption that auditory motion processing is based on a complex interaction of both stimulus-specific and attentional processes.     

Advances in electrical and mechanical cardiac mapping

Cardiac mapping--recording cardiac activity during electrophysiological testing--has evolved into an indispensable tool in studying the cardiac excitation process, analysing activation patterns, and identifying arrhythmogenic tissue. Cardiac mapping is a broad term that is used here to encompass applications that record electrical or mechanical activity of the heart or both. In recent years, simultaneous and sequential electrical mapping methods have been combined with direct mechanical measurements or imaging techniques to acquire information regarding both the electrical and mechanical activity of the heart (electromechanical mapping) during normal and irregular cardiac behavior. This paper reviews the emerging area of electromechanical mapping from the point of view of the applicable technology, including its history and application.     

Continuous noninvasive estimation of cardiac output by electrical bioimpedance: an experimental study in dogs

A new device has been developed to estimate continuously and noninvasively cardiac output from the thoracic electrical bioimpedance (CObi). CObi was compared to cardiac output by thermodilution (COtd) in five anesthetized dogs. Blood pressure, blood volume, and blood flow were manipulated by hemorrhage and infusions of sodium nitroprusside and phenylephrine. These data were used to determine the correlation between CObi and COtd under conditions of hypotensive normal flow and normotensive low flow, as well as during hemorrhagic shock and resuscitation. The CObi device was calibrated in vivo to COtd for each dog at the beginning of each experiment. CObi had a significant positive correlation with COtd throughout the experiments (r = 0.84, slope = 0.91, intercept = 0.55, p less than 0.01), and CObi predicted COtd with a standard error of the estimate of 0.81 L/min. Neither heart rate nor mean arterial pressure was significantly correlated with COtd or CObi. During severe hemorrhagic shock, CObi could not determine cardiac output in two of the dogs when COtd averaged 1.7 L/min. These data indicate that CObi is a blood-flow related variable that can be monitored continuously.     

体素内不相干运动扩散加权成像及T1mapping评价自身免疫性胰腺炎的临床研究

目的探讨磁共振体素内不相干运动扩散加权成像(intravoxel incoherentmotion diffusion weighted imaging,IVIM-DWI)及T1 mapping在评价自身免疫性胰腺炎(autoimmune pancreatitis,AIP)中的价值。材料与方法 26例AIP患者及18例健康志愿者、39例胰腺癌(pancreatic cancer,PC)患者行IVIM-DWI及T1 mapping检查,b值分别为0、25、75、100、150、200、500、800及1000 s/mm^2,AIP以病理诊断或临床证实,PC均由手术及病理证实,分析正常胰腺、PC及AIP之间的T1值、IVIM-DWI成像参数[真实扩散系数(D),假性扩散系数(D^*)和灌注分数(f)]差异,采用受试者工作曲线(receiveroperating characteristic curve,ROC)评价D、D^*、f值鉴别AIP及PC、AIP与正常胰腺的效能。结果 f值在志愿者、PC及AIP三组的值分别为(20.6±4.2)%、(12.0±3.7)%及(9.1±3.1)%,三组差异有统计学意义(P<0.001)。f值在鉴别志愿者与AIP,AIP与PC的曲线下面积(area under curve,AUC)分别为0.970和0.747,均高于T1值(AUC=0.949,0.685)、D^*(AUC=0.825,0.493)和D (AUC=0.513,0.582)。结论采用磁共振IVIMDWI灌注分数f鉴别诊断AIP具有良好的前景。     

Comparison of optical and electrical mapping of fibrillation

Optical recordings with transmembrane potential (Vm)-sensitive fluorescent dye, or extracellular potential (Ve) recordings are used to map spatiotemporal patterns of cardiac excitation during ventricular fibrillation (VF). While the optical and electrical methods are accepted, there has not been a test of whether they yield equivalent excitation times during VF. Times may differ since previous results indicate optical Vm interrogates deeper than Ve. We tested whether the steepest parts of the downward deflection of the Ve and upward deflection of optical Vm are synchronized during VF. We used simultaneous coepicentral optical and electrical mapping (32 spots, 4 kHz) with translucent indium tin oxide electrodes and a laser scanner on ventricular epicardium. VF was electrically induced in arterially-perfused rabbit hearts stained with di-4-ANEPPS. For both the optical and electrical deflections, maximum magnitudes of the slopes varied over a > 4 fold range, morphologies varied and spatiotemporal distributions were nonuniform. Time differences between the steepest parts of the optical and electrical deflections were typically a few ms. Standard deviations of time differences increased for the deflections that had the smaller slopes, which was only partly due to effects of recording noise as indicated by simulations. For deflections that had slopes ranging from the steepest found at each spot to 1/4 of the steepest, the optical deflections were on average 0.7-1 ms earlier than the Ve deflections. Thus, excitation times during VF measured optically and electrically differ. Considered together with our earlier results indicating that the optical Vm interrogates deeper than Ve, the results suggest that most fibrillatory excitations occur earlier in subsurface tissue than at the heart surface.