Relevant Locations Research Articles

Autofluorescence hyperspectral imaging of radiofrequency ablation lesions in porcine cardiac tissue.

Radiofrequency ablation (RFA) is a widely used treatment for atrial fibrillation, the most common cardiac arrhythmia. Here, we explore autofluorescence hyperspectral imaging (aHSI) as a method to visualize RFA lesions and interlesional gaps in the highly collagenous left atrium. RFA lesions made on the endocardial surface of freshly excised porcine left atrial tissue were illuminated by UV light (365nm), and hyperspectral datacubes were acquired over the visible range (420-720nm). Linear unmixing was used to delineate RFA lesions from surrounding tissue, and lesion diameters derived from unmixed component images were quantitatively compared to gross pathology. RFA caused two consistent changes in the autofluorescence emission profile: a decrease at wavelengths below 490nm (ascribed to a loss of endogenous NADH) and an increase at wavelengths above 490nm (ascribed to increased scattering). These spectral changes enabled high resolution, in situ delineation of RFA lesion boundaries without the need for additional staining or exogenous markers. Our results confirm the feasibility of using aHSI to visualize RFA lesions at clinically relevant locations. If integrated into a percutaneous visualization catheter, aHSI would enable widefield optical surgical guidance during RFA procedures and could improve patient outcome by reducing atrial fibrillation recurrence.

Laparoscopic radical lymph node dissection for advanced colon cancer close to the hepatic flexure.

Complete mesocolic excision is currently recognized as a standard procedure for colon cancer. Gastroepiploic, infrapyloric, and superficial pancreatic head lymph node metastases in the gastrocolic ligament have been reported for colon cancer close to the hepatic flexure. We sought to investigate metastases in the gastrocolic ligament in colon cancer close to the hepatic flexure. This was a single-center retrospective study. All patients with T2 or deeper invasive colon cancer in the relevant tumor location who underwent laparoscopic right hemicolectomy or extended right hemicolectomy at our institution between 1 April 2011 and 31 March 2015 were included. Lymph node dissection in the gastrocolic ligament was performed in 35 cases. Complications occurred in 11 patients (31%) and were grades I and II according to the Clavien-Dindo classification. Lymph node metastases in the gastrocolic ligament were found in only three patients (9%). Each metastasis was larger than 9 mm. Metastases in the gastrocolic ligament occurred in 9% of patients with T2 or deeper invasive colon cancer close to the hepatic flexure. Laparoscopy was feasible and useful during gastrocolic ligament resection. This study included a small sample and lacked an extended follow-up. Further studies are needed to determine the clinical relevance of this finding, particularly in terms of recurrence and long-term survival.

Spatial probabilistic pulsatility model for enhancing photoplethysmographic imaging systems.

Photoplethysmographic imaging (PPGI) is a widefield noncontact biophotonic technology able to remotely monitor cardiovascular function over anatomical areas. Although spatial context can provide insight into physiologically relevant sampling locations, existing PPGI systems rely on coarse spatial averaging with no anatomical priors for assessing arterial pulsatility. Here, we developed a continuous probabilistic pulsatility model for importance-weighted blood pulse waveform extraction. Using a data-driven approach, the model was constructed using a 23 participant sample with a large demographic variability (11/12 female/male, age 11 to 60 years, BMI 16.4 to 35.1??kg·m?2). Using time-synchronized ground-truth blood pulse waveforms, spatial correlation priors were computed and projected into a coaligned importance-weighted Cartesian space. A modified Parzen–Rosenblatt kernel density estimation method was used to compute the continuous resolution-agnostic probabilistic pulsatility model. The model identified locations that consistently exhibited pulsatility across the sample. Blood pulse waveform signals extracted with the model exhibited significantly stronger temporal correlation (W=35,p<0.01) and spectral SNR (W=31,p<0.01) compared to uniform spatial averaging. Heart rate estimation was in strong agreement with true heart rate [r2=0.9619, error (?,?)=(0.52,1.69) bpm].

Absence of skin discoloration after transarterial embolization of a subcutaneous auricular arteriovenous malformation with PHIL

One of the treatment options for arteriovenous malformations consists of embolization, with a choice of various embolic agents, with or without subsequent surgical excision. If embolization is offered without subsequent surgery, the embolic material will stay in situ, in which case the consistency and color become important in superficial lesions. The purpose of this case report is to describe if the use of a novel liquid embolic agent (PHIL) is well suited for treatment of superficial AVMs without subsequent surgery. A 30-year-old male presented with a painful reddish, pulsatile swelling of the left ear that had been present for more than 10 years. Angiography confirmed an arteriovenous malformation supplied by the superficial temporal artery and the posterior auricular artery. The lesion was successfully treated by embolization with PHIL, through the superficial temporal artery. A minute residual shunt, from the posterior auricular artery, was accepted. Immediate disappearance of pulsatile tinnitus was reported. Moreover, return of normal skin color was observed without discomfort from the embolic deposits. This result has been stable throughout one year of clinical follow-up. To our knowledge, this is the first case report describing PHIL embolization as a treatment option for superficial arteriovenous malformations without the necessity for subsequent surgery. The white color and rubbery consistency are beneficial characteristics of PHIL in treatment of subcutaneous lesions, especially in cosmetically relevant locations.

Competition between Visual Events Modulates the Influence of Salience during Free-Viewing of Naturalistic Videos.

In daily life the brain is exposed to a large amount of external signals that compete for processing resources. The attentional system can select relevant information based on many possible combinations of goal-directed and stimulus-driven control signals. Here, we investigate the behavioral and physiological effects of competition between distinctive visual events during free-viewing of naturalistic videos. Nineteen healthy subjects underwent functional magnetic resonance imaging (fMRI) while viewing short video-clips of everyday life situations, without any explicit goal-directed task. Each video contained either a single semantically-relevant event on the left or right side (Lat-trials), or multiple distinctive events in both hemifields (Multi-trials). For each video, we computed a salience index to quantify the lateralization bias due to stimulus-driven signals, and a gaze index (based on eye-tracking data) to quantify the efficacy of the stimuli in capturing attention to either side. Behaviorally, our results showed that stimulus-driven salience influenced spatial orienting only in presence of multiple competing events (Multi-trials). fMRI results showed that the processing of competing events engaged the ventral attention network, including the right temporoparietal junction (R TPJ) and the right inferior frontal cortex. Salience was found to modulate activity in the visual cortex, but only in the presence of competing events; while the orienting efficacy of Multi-trials affected activity in both the visual cortex and posterior parietal cortex (PPC). We conclude that in presence of multiple competing events, the ventral attention system detects semantically-relevant events, while regions of the dorsal system make use of saliency signals to select relevant locations and guide spatial orienting.

Looking for symmetry: fixational eye movements are biased by image mirror symmetry.

Humans are highly sensitive to symmetry. During scene exploration, the area of the retina with dense light receptor coverage acquires most information from relevant locations determined by gaze fixation. We characterized patterns of fixational eye movements made by observers staring at synthetic scenes either freely (i.e., free exploration) or during a symmetry orientation discrimination task (i.e., active exploration). Stimuli could be mirror-symmetric or not. Both free and active exploration generated more saccades parallel to the axis of symmetry than along other orientations. Most saccades were small (<2°), leaving the fovea within a 4° radius of fixation. Analysis of saccade dynamics showed that the observed parallel orientation selectivity emerged within 500 ms of stimulus onset and persisted throughout the trials under both viewing conditions. Symmetry strongly distorted existing anisotropies in gaze direction in a seemingly automatic process. We argue that this bias serves a functional role in which adjusted scene sampling enhances and maintains sustained sensitivity to local spatial correlations arising from symmetry.

Machine learning and dynamic user interfaces in a context aware nurse application environment

The increasing usage of smartphones in daily life has received considerable attention in academic and industry driven research to be utilized in the health sector. There has been development of a variety of health-related smartphone applications. Currently, however, there are few to none applications based on nurses’ historical or behavioral preferences. Mobile application development for the health care sector requires extensive attention to security, reliability, and accuracy. In nursing applications, the users are often required to navigate in hospital environments, select patients to support, read the patient history and set action points to assist the patient during their shift. Finally, they have to report their performance on patient related activities and other relevant information before they leave for the day. In a working day, a nurse often visits different locations such as the patient’s room, different laboratories, and offices for filling reports. There is still a limited capability to access context relevant information on a smartphone with minimal recourse such as Wi-Fi triangulation. The Wi-Fi triangulation signals fluctuate significantly for indoor location positioning. Therefore, providing relevant location based services to a mobile subscriber has become challenging. This paper addresses this gap by applying machine learning and behavior analysis to anticipate the potential location of the nurse and provide the required services. The application concept was already presented at the IMCOM 2015 conference. This paper focuses on the process to ascertain a user’s context, the process of analyzing and predicting user behavior, and finally, the process of displaying the information through a dynamically generated UI.

Avoiding pitfalls in the diagnostics of bone neoplasms from pathologists point of view : Importance of reference pathology

Bone tumors account for only approximately 1 % of the total number of malignant tumors in humans so that they are only rarely diagnosed and appropriate experience is difficult to acquire. Although the number of entities is limited there exist very different clinical and radiological images depending on the manifestation in the different regions of the skeleton. Bone tumors are also histologically structured very differently even within a particular entity. Prior to the histopathological diagnosis the location of the lesion within the entire skeleton and in relation to the tumor-bearing bone must be clarified based on imaging findings, i.e. which bone is affected, which portion of the bone is affected and is the tumor centrally located in the marrow cavity, in the area of the corticalis or on the outside? It is known that bone tumors show diagnostically relevant preferential locations in both the total skeleton as well as within the affected bone depending on the entity and that the age of onset also varies. In this article the most common reasons for errors in assessment are discussed. In most cases it is possible for reference pathology to still correctly classify specific cases by a consistent consideration of diagnostic radiology in combination with morphology. Although diagnostic progress for specific entities of bone tumors has been achieved using molecular methods, the established principle of interdisciplinary cooperation is the prerequisite for the correct diagnosis of these tumors. The therapeutic consequences for patients can be substantial and result in life-long functional limitations depending on the diagnosis (e.g. joint resection for osteosarcoma in childhood and adolescence). A correct diagnosis is therefore of great importance for far-reaching therapeutic decision-making.

Of "what" and "where" in a natural search task: Active object handling supports object location memory beyond the object's identity.

Looking for as well as actively manipulating objects that are relevant to ongoing behavioral goals are intricate parts of natural behavior. It is, however, not clear to what degree these two forms of interaction with our visual environment differ with regard to their memory representations. In a real-world paradigm, we investigated if physically engaging with objects as part of a search task influences identity and position memory differently for task-relevant versus irrelevant objects. Participants equipped with a mobile eye tracker either searched for cued objects without object interaction (Find condition) or actively collected the objects they found (Handle condition). In the following free-recall task, identity memory was assessed, demonstrating superior memory for relevant compared to irrelevant objects, but no difference between the Handle and Find conditions. Subsequently, location memory was inferred via times to first fixation in a final object search task. Active object manipulation and task-relevance interacted in that location memory for relevant objects was superior to irrelevant ones only in the Handle condition. Including previous object recall performance as a covariate in the linear mixed-model analysis of times to first fixation allowed us to explore the interaction between remembered/forgotten object identities and the execution of location memory. Identity memory performance predicted location memory in the Find but not the Handle condition, suggesting that active object handling leads to strong spatial representations independent of object identity memory. We argue that object handling facilitates the prioritization of relevant location information, but this might come at the cost of deprioritizing irrelevant information.

Radiology of epiploic appendages: acute appendagitis, post-infarcted appendages, and imaging natural history.

Our aim was to demonstrate the imaging characteristics of epiploic appendages in native, acute inflamed/ischemic and post-infarcted states through retrospective imaging analysis, with clinical and pathologic correlation, and to discuss clinical implications. Cases were gathered mostly retrospectively and reviewed for inclusion based on established diagnostic criteria. Radiology report text search was used to find cases, using terms "epiploic," "appendage," "appendagitis," and "peritoneal body." Data records included patient demographics, relevant clinical data, lesion size, location and apparent imaging composition, and the presence of change or stability in features over multiple studies. Pathologic and clinical data were sought and assessed for correlation. Imaging studies of 198 individuals were included (mean age 50, range 9-95), with a total of 228 lesions: 63 acute and 165 non-acute presentations. All included subjects had CT imaging and some had lesions visible on radiographs, MRI, PET/CT, and sonography. 23 subjects had more than one studied lesion. In addition to classic acute appendagitis, more frequently encountered are post-infarcted appendages either in situ along the colon, adhered to peritoneal or serosal surfaces, or freely mobile in the peritoneum as loose bodies. The majority of the non-acute varieties are recognizable due to peripheral calcification that develops over time following ischemic insult. Multiple cases demonstrated the imaging natural history and confirmed pathologic basis for imaging findings. In summary, acute and post-infarcted epiploic appendages have characteristic imaging appearances and natural history which should provide correct diagnosis in most cases. Incidental post-infarcted epiploica are more commonly encountered than acute presentations.

Oxygen-independent FbFP: Fluorescent sentinel and oxygen sensor component in Saccharomyces cerevisiae and Candida albicans

FMN-binding fluorescent proteins (FbFPs) outperform GFP and its derivatives because of their oxygen-independence, small size and rapid maturation. FbFPs have been used successfully as reliable reporters of gene expression in the cytoplasm of pro- and eukaryotes. Here we extend previous findings on the codon-adapted CaFbFP variant, which functions in the apathogenic yeast Saccharomyces cerevisiae and the human fungal pathogen Candida albicans. In both fungal species, CaFbFP could be targeted to the nucleus and the cell wall by endogenous signals (H2B-/Aga2-fusions) demonstrating its use as a fluorescent beacon in these relevant cellular locations. Transformants of both fungal species producing a CaFbFP-YFP fusion (YFOS) showed variable energy transfer from CaFbFP to YFP (FRET) that depended in its extent on external O2 concentrations. Applications as fluorescent sentinel and oxygen biosensor expand the FbFP toolbox to study oxygen-independent cellular processes under hypoxia.

Abstract B37: Dural and parenchymal brain metastases in breast cancer are characterized by distinct inflammatory tumour microenvironments

Abstract Central nervous system metastases develop in ~15% of metastatic breast cancer patients and are associated with a very poor prognosis due to the lack of effective therapies. Intracranial metastases are mainly located within the brain parenchyma, in the skull, at the leptomeninges or at the dura. Although simultaneous involvement of multiple intracranial locations is very common in breast cancer, the experimental studies have been focusing mainly on parenchymal brain metastases. To address the knowledge gap in understanding of metastases at other CNS locations, we developed preclinical mouse models of intracranial breast cancer metastases with simultaneous involvement of brain parenchyma and the dura. This enabled us to subsequently study and compare cancer cell phenotype and inflammatory tumour microenvironment at the two intracranial locations. Simultaneous colonization of brain parenchyma and the dura was achieved by administration of cancer cells into the internal carotid artery of mice. This resulted in a significantly higher dural as compared to the parenchymal tumour burden across 3 different breast cancer models. The inflammatory tumour microenvironment in dural and parenchymal brain metastases was subsequently analysed by flow cytometry. Although model-specific differences in metastases-infiltrating immune cell populations were detected, microglia/macrophages were the most abundant cell population across all 3 models. Further analysis of this cell population revealed that microglia were the predominant population within parenchymal metastases, while they were almost absent from the dural metastases. Macrophages were present at both locations and were significantly more abundant at the dura. In comparison to parenchymal macrophages, dural macrophages expressed significantly higher levels of MHCII and CD11c, which was suggestive of a higher antigen presenting capacity. We next investigated site-specific cancer cell phenotypes. To this end, dura- and brain parenchyma-tropic cancer cell variants were generated through 3 rounds of in vivo selection and investigated by gene expression profiling. Among others, this revealed significant differences in inflammation-related pathways, expression of inflammatory cytokines and differences in activity of transcription factors NFKB1 and TCF4. This was in line with distinct expression of antigen presenting cell markers in dural versus parenchymal macrophages. Further investigation into polarization of macrophages revealed site-specific polarization patterns, with dural macrophages being skewed towards M1 phenotype as compared to the parenchymal macrophages. In the above study we established pre-clinical models of intracranial breast cancer metastases with simultaneous involvement of brain parenchyma and the dura. Our study demonstrated that cancer cells at those two clinically relevant intracranial locations acquire different site-specific phenotypes, which was reflected in distinct polarization phenotypes of macrophages. Due to distinct phenotypes of cancer cells as well as macrophages, parenchymal brain metastases and dural metastases may respond differently to certain therapies (e.g. immune therapies). Therefore, these site-specific differences may need to be considered in the treatment of “multi-site” central nervous system metastases. Citation Format: Nora Rippaus, Jennifer Williams, David Taggart, Tereza Andreou, Krzysztof Wronski, Mihaela Lorger. Dural and parenchymal brain metastases in breast cancer are characterized by distinct inflammatory tumour microenvironments. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr B37.

Complementary Functional Organization of Neuronal Activity Patterns in the Perirhinal, Lateral Entorhinal, and Medial Entorhinal Cortices.

Contrary to the common view that brain regions in the "what" and "where" streams distinctly process object and spatial cues, respectively, we found that both streams encode both object and spatial information but distinctly organize memories for objects and space. Specifically, perirhinal cortex and lateral entorhinal cortex represent objects and, within the object-specific representations, the locations where they occur. Conversely, medial entorhinal cortex represents relevant locations and, within those spatial representations, the objects that occupy them. Furthermore, these findings reach beyond simple notions of perirhinal cortex and lateral entorhinal cortex neurons as object detectors and MEC neurons as position detectors, and point to a more complex organization of memory representations within the medial temporal lobe system.

Just in time? Using QR codes for multi-professional learning in clinical practice

Clinical guidelines and policies are widely available on the hospital intranet or from the internet, but can be difficult to access at the required time and place. Clinical staff with smartphones could use Quick Response (QR) codes for contemporaneous access to relevant information to support the Just in Time Learning (JIT-L) paradigm. There are several studies that advocate the use of smartphones to enhance learning amongst medical students and junior doctors in UK. However, these participants are already technologically orientated. There are limited studies that explore the use of smartphones in nursing practice. QR Codes were generated for each topic and positioned at relevant locations on a medical ward. Support and training were provided for staff. Website analytics and semi-structured interviews were performed to evaluate the efficacy, acceptability and feasibility of using QR codes to facilitate Just in Time learning. Use was intermittently high but not sustained. Thematic analysis of interviews revealed a positive assessment of the Just in Time learning paradigm and context-sensitive clinical information. However, there were notable barriers to acceptance, including usability of QR codes and appropriateness of smartphone use in a clinical environment. The use of Just in Time learning for education and reference may be beneficial to healthcare professionals. However, alternative methods of access for less technologically literate users and a change in culture of mobile device use in clinical areas may be needed.

Revision of Paleogene plate motions in the Pacific and implications for the Hawaiian-Emperor bend: COMMENT

According to literature summarized by Wright et al. (2015), it is generally accepted that hotspots have moved relative to each other since 80 Ma, and that the Hawaiian hotspot moved south relative to the spin axis during formation of the Emperor seamounts prior to 48 Ma. Koivisto et al. (2014) advanced the alternative view that the minimum relative motion between hotspots is much smaller than generally accepted, implying errors in the global plate circuit are larger than generally accepted. In particular, they suggest that the global circuits are incorrect for motion prior to 48 Ma between East and West Antarctica. In this view, southward motion of the Hawaiian hotspot is evidence for motion of the entire lower mantle relative to the spin axis. Wright et al. defend conventional wisdom using freshly calculated relative motion solutions for plates in the Pacific basin. They conclude that the Hawaiian-Emperor bend (HEB), formed at ca. 50-42 Ma and sharpest at 47.5 Ma, is a result of the cessation of southward motion of the Hawaiian hotspot and is not a result of change of absolute motion of the Pacific plate. The purpose of this Comment is to point out that their results are at least as consistent with a large change in motion of the Pacific plate that was responsible for a significant part of the HEB. Wright et al. calculate Pacific-Farallon finite half-rotations from the Pacific-plate record at more frequent intervals than previous workers. They recognize an acceleration from ~75 mm/yr full rate prior to 60 Ma to ~180 mm/yr after 40 Ma. According to their preferred Cande and Kent (1995) time scale, this acceleration is spread out over 57–40 Ma, but according to the Ogg (2012) time scale, the acceleration is contained within the interval of 50–43 Ma, a time interval entirely within the age span of the HEB. Their statement that their “results are not strongly dependent on the time scale used” is hard to understand. In the discussion associated with Wright et al.’s figure 3, they suggest that this acceleration is dominated by eastward acceleration of the Farallon plate in an absolute reference frame. Any conclusion that Pacific absolute motion didn’t change much is circular because they assume that one of three published models for Pacific plate absolute motion is correct, and for all of these published models, changes in Pacific plate absolute motion are small. This discussion does not address the possibility that all three of these models for absolute reference frames share common errors in the global plate circuit. Wright et al. briefly mention their analysis of Pacific-Antarctic motion, presented in their figure 2, in terms of rate and direction of motion at the Pitman Fracture Zone in the far south Pacific. In discussion of Northern Hemisphere events possibly related to Pacific-Farallon acceleration, they suggest that westward acceleration of the Pacific plate would correspond to increased Pacific-Antarctic spreading rates. Because they observe a rate decrease at the Pitman Fracture Zone, they suggest that change in Pacific absolute motion was “relatively minor.” Here they make a serious error in failing to consider spherical geometry. The Pitman transform fault active at 48 Ma was 90–100° of arc away from the Molokai and Murray Fracture Zones, and the HEB. Their discussion frames the most relevant issue as how the motion of the Pacific plate changes at the location of the Hawaiian hotpsot. The velocity of the Pacific plate relative to Antarctica when calculated at relevant Northern Hemisphere locations does increase sharply near 48 Ma. Calculated at the location of Hawaii, the velocity of the Pacific plate changes from slow (35 mm/yr) northwest motion to fast (83 mm/yr) west-northwest motion

The European lightning location system EUCLID – Part 1: Performance analysis and validation

Abstract. In this paper we present a performance analysis of the European lightning location system EUCLID for cloud-to ground flashes/strokes in terms of location accuracy (LA), detection efficiency (DE) and peak current estimation. The performance analysis is based on ground truth data from direct lightning current measurements at the Gaisberg Tower (GBT) and data from E-field and video recordings. The E-field and video recordings were collected in three different regions in Europe, namely in Austria, Belgium and France. The analysis shows a significant improvement of the LA of the EUCLID network over the past 7 years. Currently, the median LA is in the range of 100 m in the center of the network and better than 500 m within the majority of the network. The observed DE in Austria and Belgium is similar, yet a slightly lower DE is determined in a particular region in France, due to malfunctioning of a relevant lightning location sensor during the time of observation. The overall accuracy of the lightning location system (LLS) peak current estimation for subsequent strokes is reasonable keeping in mind that the LLS-estimated peak currents are determined from the radiated electromagnetic fields, assuming a constant return stroke speed. The results presented in this paper can be used to estimate the performance of the EUCLID network related to cloud-to-ground flashes/strokes for regions with similar sensor baselines and sensor technology.

An Educational Hardware/Software Tool for the First Course in Computer Architecture

In this paper, we briefly present our design decisions and challenges involved in designing the hardware/software tools that we prepared based on our several years of experience in teaching logic circuits and computer architecture which help students of the first course in computer architecture to familiarize themselves with the basic operations of a computer. In fact, we first present the hardware of an 8-bit processor and its I/O and memory board that we have specifically designed and built using basic logic ICs for pedagogical purposes. We then go over the features and design challenges of a special monitor program we created. This monitor program directly runs on the top of our 8-bit processor and provides invaluable features, such as executing the students’ program in two possible modes (single step and continuous run), displaying the contents of CPU registers, flags, and relevant memory locations, in addition to the ability to pause the program execution on real hardware, and modify these contents and continue.

Climate change impacts on the power generation potential of a European mid-century wind farms scenario

Wind energy resource is subject to changes in climate. To investigate the impacts of climate change on future European wind power generation potential, we analyze a multi-model ensemble of the most recent EURO-CORDEX regional climate simulations at the 12 km grid resolution. We developed a mid-century wind power plant scenario to focus the impact assessment on relevant locations for future wind power industry. We found that, under two greenhouse gas concentration scenarios, changes in the annual energy yield of the future European wind farms fleet as a whole will remain within ±5% across the 21st century. At country to local scales, wind farm yields will undergo changes up to 15% in magnitude, according to the large majority of models, but smaller than 5% in magnitude for most regions and models. The southern fleets such as the Iberian and Italian fleets are likely to be the most affected. With regard to variability, changes are essentially small or poorly significant from subdaily to interannual time scales.

An Attention-Sensitive Memory Trace in Macaque MT Following Saccadic Eye Movements.

We experience a visually stable world despite frequent retinal image displacements induced by eye, head, and body movements. The neural mechanisms underlying this remain unclear. One mechanism that may contribute is transsaccadic remapping, in which the responses of some neurons in various attentional, oculomotor, and visual brain areas appear to anticipate the consequences of saccades. The functional role of transsaccadic remapping is actively debated, and many of its key properties remain unknown. Here, recording from two monkeys trained to make a saccade while directing attention to one of two spatial locations, we show that neurons in the middle temporal area (MT), a key locus in the motion-processing pathway of humans and macaques, show a form of transsaccadic remapping called a memory trace. The memory trace in MT neurons is enhanced by the allocation of top-down spatial attention. Our data provide the first demonstration, to our knowledge, of the influence of top-down attention on the memory trace anywhere in the brain. We find evidence only for a small and transient effect of motion direction on the memory trace (and in only one of two monkeys), arguing against a role for MT in the theoretically critical yet empirically contentious phenomenon of spatiotopic feature-comparison and adaptation transfer across saccades. Our data support the hypothesis that transsaccadic remapping represents the shift of attentional pointers in a retinotopic map, so that relevant locations can be tracked and rapidly processed across saccades. Our results resolve important issues concerning the perisaccadic representation of visual stimuli in the dorsal stream and demonstrate a significant role for top-down attention in modulating this representation.

The attentive homunculus: ERP evidence for somatotopic allocation of attention in tactile search

Our brain constantly receives tactile information from the body’s surface. We often only become aware of this information when directing our attention towards the body. Here, we report a study investigating the behavioural and neural response when selecting a target amongst distractor vibrations presented simultaneously to several locations either across the hands or body. Comparable visual search studies have revealed the N2pc as the neural correlate of visual selective attention. Analogously, we describe an enhanced negativity contralateral to the tactile target side. This effect is strongest over somatosensory areas and lasts approximately 200ms from the onset of the somatosensory N140 ERP component. Based on these characteristics we named this electrophysiological signature of attentional tactile target selection during tactile search the N140-central-contralateral (N140cc). Furthermore, we present supporting evince that the N140cc reflects attentional enhancement of target rather than suppression of distractor locations; the component was not reliably altered by distractor but rather by target location changes. Taken together, our findings present a novel electrophysiological marker of tactile search and show how attentional selection of touch operates by mainly enhancing task relevant locations within the somatosensory homunculus.