Controlling conflict from interfering long-term memory representations.

Remembering is more than an activation of a memory trace. As retrieval cues are often not uniquely related to one specific memory, cognitive control should come into play to guide selective memory retrieval by focusing on relevant while ignoring irrelevant information. Here, we investigated, by means of EEG and fMRI, how the memory system deals with retrieval interference arising when retrieval cues are associated with two material types (faces and spatial positions), but only one is task-relevant. The topography of slow EEG potentials and the fMRI BOLD signal in posterior storage areas indicated that in such situations not only the relevant but also the irrelevant material becomes activated. This results in retrieval interference that triggers control processes mediated by the medial and lateral PFC, which are presumably involved in biasing target representations by boosting the task-relevant material. Moreover, memory-based conflict was found to be dissociable from response conflict that arises when the relevant and irrelevant materials imply different responses. The two types of conflict show different activations in the medial frontal cortex, supporting the claim of domain-specific prefrontal control systems.

Analysis of pneumatization and neurovascular structures of the sphenoid sinus using cone-beam tomography (CBT).

BACKGROUND: The sphenoid sinus is a frequent target of paranasal sinus surgery. Because of the high risk of injuring the surrounding structures (e.g. internal carotid artery, optical nerve) a preoperative imaging is absolutely necessary. PURPOSE: To analyze the possibilities of cone-beam computed tomography (CBCT), which is especially quite a new technique in ENT, in the evaluation of the sphenoid sinus, its surrounding structures, and the corresponding anatomical variations. MATERIAL AND METHODS: This was a retrospective, single-centre study of 580 patients (1160 sides = cases). The Accu-I-Tomo-F17 was used. Pneumatization of sphenoid sinus, course of internal artery, course of optical nerve, and dehiscence of the bony canals were evaluated. RESULTS: In the case of pneumatization a type I (completely missing or minimal sphenoid sinus) was found in two patients (0.3%), type II (posterior wall of sphenoid sinus is in front of the anterior wall of the sella) in 38 patients (6.6%), type III (posterior wall is between anterior and posterior wall of sella) in 332 patients (57,2%), type IVa (posterior wall is behind the posterior wall of sella without air dorsal the sella) in 104 patients (17.9%), and type IVb (similar to type IVa but with air dorsal the sella) in 104 patients (17.9%). In 1025 cases (89.5%) a smooth course of the internal carotid artery was found whereas a free course could be detected in 120 cases (10.5%). Defects of the bony canal of the optical nerve were found in 16.7% and of the internal carotid artery in 2.7% of the cases. The optical nerve showed a free course through the sphenoid in 151 cases (13.7%) and a smooth course in 1007 cases (87.0%). CONCLUSION: CBCT could evaluate all relevant anatomic structures and answer the questions of different anatomical variants. A modified classification of the pneumatization of the sphenoid sinus could be described. Frequencies of anatomical variations are in accordance with the current literature of CT research.

Memory-based decision-making with heuristics: evidence for a controlled activation of memory representations.

Many of our daily decisions are memory based, that is, the attribute information about the decision alternatives has to be recalled. Behavioral studies suggest that for such decisions we often use simple strategies (heuristics) that rely on controlled and limited information search. It is assumed that these heuristics simplify decision-making by activating long-term memory representations of only those attributes that are necessary for the decision. However, from behavioral studies alone, it is unclear whether using heuristics is indeed associated with limited memory search. The present study tested this assumption by monitoring the activation of specific long-term-memory representations with fMRI while participants made memory-based decisions using the "take-the-best" heuristic. For different decision trials, different numbers and types of information had to be retrieved and processed. The attributes consisted of visual information known to be represented in different parts of the posterior cortex. We found that the amount of information required for a decision was mirrored by a parametric activation of the dorsolateral PFC. Such a parametric pattern was also observed in all posterior areas, suggesting that activation was not limited to those attributes required for a decision. However, the posterior increases were systematically modulated by the relative importance of the information for making a decision. These findings suggest that memory-based decision-making is mediated by the dorsolateral PFC, which selectively controls posterior storage areas. In addition, the systematic modulations of the posterior activations indicate a selective boosting of activation of decision-relevant attributes.

Frontal and parietal contributions to arithmetic fact retrieval: a parametric analysis of the problem-size effect.

The goal of the present study was to investigate the neuroanatomical basis of arithmetic fact retrieval. The rationale was that areas playing a crucial role in arithmetic fact retrieval should show a systematic increase of activation with increasing retrieval effort. To achieve this goal, we utilized the problem-size effect as this is known to be systematically related to retrieval effort. In contrast to many previous studies, we here took a parametric approach to account for the continuous increase of retrieval effort with problem size. BOLD signals were modeled with problem size as parametric regressor and negative slow waves of the EEG were categorized into six levels of problem size. The fMRI data showed that activation in the angular gyrus and ACC/SMA increased parametrically with problem size. The ERP data showed a systematic amplitude increase with increasing problem size, especially at fronto-central electrodes. Consistent with the fMRI data, source modeling localized this effect to the ACC. While these findings support previous notions about the crucial role of the angular gyrus during fact retrieval, they also provide evidence that the medial frontal cortex is involved when single-digit multiplications are solved. Thus, both parietal and frontal structures seem to be integral parts of a system that enables and controls arithmetic fact retrieval.

Early side effects after embolization of a carotid body tumor using Onyx.

The case of a 20-year-old woman with a carotid body tumor of Shamblin class III is reported. Ten hours after preoperative direct intralesional embolization with 20 mL Onyx (ethylene-vinyl alcohol copolymer; Micro Therapeutics, Irvine, Calif), the patient showed symptoms of Horner syndrome and deficits of the hypoglossal and glossopharyngeal nerves. Intraoperative examination 12 hours after Onyx embolization revealed a massive swelling of the hypoglossal and glossopharyngeal nerves. The patient's tongue motility and glossopharyngeal function improved after surgery, but Horner syndrome was still present. Owing to the delayed occurrence of these adverse effects, the optimal time of surgical intervention after Onyx embolization should be discussed and perhaps expedited.

The human dorsal action control system develops in the absence of vision.

The primate dorsal pathway has been proposed to compute vision for action. Although recent findings suggest that dorsal pathway structures contribute to somatosensory action control as well, it is yet not clear whether or not the development of dorsal pathway functions depends on early visual experience. Using functional magnetic resonance imaging, we investigated the pattern of cortical activation in congenitally blind and matched blindfolded sighted adults while performing kinesthetically guided hand movements. Congenitally blind adults activated similar dorsal pathway structures as sighted controls. Group-specific activations were found in the extrastriate cortex and the auditory cortex for congenitally blind humans and in the precuneus and the presupplementary motor area for sighted humans. Dorsal pathway activity was in addition observed for working memory maintenance of kinesthetic movement information in both groups. Thus, the results suggest that dorsal pathway functions develop in the absence of vision. This favors the idea of a general mechanism of movement control that operates regardless of the sensory input modality. Group differences in cortical activation patterns imply different movement control strategies as a function of visual experience.

Dissociating the solution processes of small, large, and zero multiplications by means of fMRI.

The present study investigated the neuroanatomical basis of different solution processes in single-digit multiplication by means of fMRI. Sixteen participants silently produced the solution of three distinct types of multiplication, i.e., problems involving zero (e.g., 3*0), small (e.g., 2*4), or large operands (e.g., 8*7). Zero and small problems are assumed to be solved by rule application and fact retrieval, respectively, and problems with large operands sometimes involve backup strategies when direct retrieval is not sufficient. Small problems, when compared with a high-level baseline not requiring any kind of calculation, activated a network of parietal, subcortical, and frontal areas. This activation pattern supports the hypothesis that arithmetic fact retrieval is mediated by a verbal processing loop including the angular gyrus and the basal ganglia. Problems with larger operands showed increased activation in the anterior cingulate cortex, SMA, and the left inferior frontal gyrus, which could reflect increased conflict during the fact-retrieval process, but also higher demands for controlling and coordinating multiple processing steps when a problem cannot be solved by direct retrieval. Zero problems, in comparison to multiplications with small operands, activated the caudate nucleus and the right inferior frontal cortex, showing that rule application is separable from fact retrieval on a neuroanatomical level, too.

Kinesthetic working memory and action control within the dorsal stream.

There is wide agreement that the "dorsal (action) stream" processes visual information for movement control. However, movements depend not only on vision but also on tactile and kinesthetic information (=haptics). Using functional magnetic resonance imaging, the present study investigates to what extent networks within the dorsal stream are also utilized for kinesthetic action control and whether they are also involved in kinesthetic working memory. Fourteen blindfolded participants performed a delayed-recognition task in which right-handed movements had to be encoded, maintained, and later recognized without any visual feedback. Encoding of hand movements activated somatosensory areas, superior parietal lobe (dorsodorsal stream), anterior intraparietal sulcus (aIPS) and adjoining areas (ventrodorsal stream), premotor cortex, and occipitotemporal cortex (ventral stream). Short-term maintenance of kinesthetic information elicited load-dependent activity in the aIPS and adjacent anterior portion of the superior parietal lobe (ventrodorsal stream) of the left hemisphere. We propose that the action representation system of the dorsodorsal and ventrodorsal stream is utilized not only for visual but also for kinesthetic action control. Moreover, the present findings demonstrate that networks within the ventrodorsal stream, in particular the left aIPS and closely adjacent areas, are also engaged in working memory maintenance of kinesthetic information.

Motor learning affects visual movement perception.

In the present study we investigated whether imitation of artificial movement trajectories of meaningless objects has an effect on how these trajectories are later perceptually processed within the human brain. During observation of a sequence of artificial object movements 10 participants (experimental group) actively imitated the trajectories during motor training and 10 participants (control group) solved a working memory task without motor training. The haemodynamic responses were recorded before and after the intervention while participants observed the movements and either had to detect colour changes of one of the objects (colour task, motor-irrelevant) or had to judge whether the movement pattern could be imitated with the hands (simulation judgement task, motor-relevant). The between-group comparison of the post-intervention haemodynamic responses revealed stronger activity for the motor training than for the control group during the simulation judgement task. This activity appeared in motor-related areas (supplementary motor area and inferior parietal lobe) and in the occipito-temporal area. During the colour task, the motor training group showed stronger activity in the occipital lobe. The control group did not reveal any stronger activity than the motor training group for either task. The results suggest that motor training has task-specific effects on neural processes that are involved in perception of movements. Furthermore, they indicate that motor-related areas are triggered by observed artificial object movements, but only if a motor-relevant task is pursued.

What activates the human mirror neuron system during observation of artificial movements: bottom-up visual features or top-down intentions?

In a recent study we could show that during observation of artificial object movements a similar cortical network, including the areas of the so-called human mirror neuron system (hMNS), was activated as during the observation of hand movements. The present study investigated whether activation of the hMNS during the observation of artificial object movements depends more on the visual features of the movements (buttom-up), or, by manipulating the task instructions, on the intentional goal of an observer (top-down). Using a factorial design we recorded the hemodynamic responses in 20 healthy participants while they watched arbitrary artificial object movements following two types of movement trajectories (smooth vs. discontinuous). In one part of the experiment participants had to detect color changes of two objects (color task) and in another part they had to judge whether the movement pattern of two objects could be performed with human hands (simulation task). We found stronger activation in the hMNS during the simulation than during the color task for both types of movement trajectories. In contrast, the color task activated the left ventral-occipital area (human V4). A direct comparison of smooth vs. discontinuous movement trajectories revealed significant effects neither in the structures of the hMNS nor in human V4. The present findings suggest that it is not a specific visual feature, such as a smooth biological movement trajectory, that activates the hMNS. Rather, the hMNS seems to respond when an observed movement is matched to a motor representation triggered by the intentional goal of the observer.

Preoperative 3-Dimensional Angiography Data and Intraoperative Real-Time Vascular Data Integrated in Microscope-Based Navigation by Automatic Patient Registration Applying Intraoperative Computed Tomography.

OBJECTIVE: To establish a workflow integrating preoperative 3-dimensional (3D) angiography data and intraoperative real-time vascular information in microscope-based navigation for aneurysm and arteriovenous malformation (AVM) surgery. METHODS: In 7 patients (3 with AVMs and 4 with aneurysms), preoperative 3D rotational angiography or computed tomography (CT) or magnetic resonance angiography data were navigated applying a 32-slice movable CT scanner for low-dose registration scanning. The 3D vasculature was segmented and visualized by microscope-based navigation along with navigated intraoperative real-time imaging data from indocyanin green angiography and duplex ultrasonography. RESULTS: Automatic registration applying intraoperative CT resulted in high accuracy (registration error, 0.80 ± 0.79 mm). The effective radiation dose of the registration CT scans (0.28-0.42 mSv) was only approximately one-sixth of a standard diagnostic head CT scan. The 3D vessel architecture could be visualized accurately in the operating microscope heads-up display and on the navigation screens in the same projection as the view angle of the surgeon, both facilitating orientation in 3D space, providing a better understanding of anatomy. In addition, intraoperative real-time modalities could be coregistered with high precision, providing further information during the course of the vascular procedure. CONCLUSIONS: Registration CT imaging facilitates integrating preoperative and intraoperative vascular image data with a low registration error and low radiation exposure for the patient, improving the understanding of 3D vascular anatomy during surgery with easier identification of feeding vessels in AVMs, and of the projection and configuration of aneurysms.

Regional Differences in Thrombectomy Rates : Secondary use of Billing Codes in the MIRACUM (Medical Informatics for Research and Care in University Medicine) Consortium.

BACKGROUND AND PURPOSE: Mechanical thrombectomy, in addition to intravenous (i.v.) thrombolysis is recommended for treatment of acute stroke in patients with large vessel occlusions (LVO) in the anterior circulation up to 6 h after symptom onset. We compared thrombectomy rates of eight university hospitals of the MIRACUM consortium to analyze the implementation of this guideline in clinical routine. METHODS: Anonymized billing data in a standardized format were loaded into a local i2b2 data warehouse by applying already existing extract, transform and load (ETL) routines. A locally executed uniform SQL (structured query language) query delivered aggregated site data for all inpatients with a discharge diagnosis of ischemic stroke (ICD-10 I63) containing counts for type of acute treatment, type of admission and age groups, which were centrally analyzed with R. RESULTS: From 2014 to 2016, the thrombectomy rate almost doubled from a mean of 4.7% to 9.6%, although significant differences between centers exist (range in 2016: 5.8-17%). The number of drip-and-ship procedures increased in 3 out of 8 centers. There was no evidence for a decrease in thrombectomy rates during weekends/holiday or among patients older than 80 years, but this age group is more likely to receive i.v. recombinant tissue plasminogen activator (rtPA). CONCLUSION: The observed increase of thrombectomy rates and drip-and-ship procedures without a significant difference between weekdays and weekends or patients of different ages is substantiating a rapid implementation of stroke guidelines within the analyzed neurovascular centers. The prototype of the MIRACUM Data Integration Center already contributes to health services research in Germany.

Surgery of intracranial aneurysms previously treated endovascularly.

OBJECTIVE: To perform a retrospective study on the patients who underwent aneurysmal surgery following endovascular treatment. PATIENTS AND METHODS: We performed a retrospective study on eight patients who underwent aneurysmal surgery following endovascular treatment (-attempts) with gugliemi detachable coils (GDCs). The indications for surgery, surgical techniques and clinical outcomes were analyzed. RESULTS: The indications for surgical treatment after GDC coiling of aneurysm were classified into three groups. First group: surgery of incompletely coiled aneurysms (n=4). Second group: surgery of mass effect on the neural structures due to coil compaction or rebleeding (n=2). Third group: surgery of vascular complications after endovascular procedure due to parent artery occlusion or thrombus propagation from aneurysm (n=2). Aneurysm obliterations could be performed in all cases confirmed by postoperative angiography. Six patients had an excellent outcome and returned to their profession. Patient's visual acuity was improved. One individual experienced right hemiparesis (grade IV/V) and hemihypesthesia. CONCLUSIONS: Microsurgical clipping is rarely necessary for previously coiled aneurysms. Surgical treatment is uncommonly required when an acute complication arises during endovascular treatment, or when there is a dynamic change of a residual aneurysm configuration over time that is considered to be insecure.

Acute haemorrhage in patients with advanced head and neck cancer: value of endovascular therapy as palliative treatment option.

AIMS: Acute or subacute haemorrhage is one of the most frightening complications in patients suffering from advanced head and neck cancer. Few articles report experience with superselective endovascular therapy for this purpose. Is endovascular therapy underestimated in the field of palliative head and neck cancer therapy? This study set out to investigate this question. PATIENTS AND METHODS: A review was undertaken of the clinical courses of seven patients (six men, one woman) suffering from incurable, advanced head and neck cancer (four pharyngeal, two laryngeal, one neck) and treated with superselective endovascular strategies as an emergency procedure for acute bleeding. RESULTS: All patients were successfully treated without evidence of neurological complication. Patients reached a median survival of 20 weeks (range eight-168 weeks). Following endovascular treatment all patients were discharged from the hospital within several days. Three patients survived almost free of symptoms for several weeks and were able to stay at home with their families until their death. CONCLUSION: We conclude that in the field of palliative care, superselective endovascular therapy deserves to be considered alongside standard treatment options for the management of acute haemorrhage from advanced head and neck cancer.

Inferior parietal and right frontal contributions to trial-by-trial adaptations of attention to memory.

The attention to memory theory (AtoM) proposes that the same brain regions might be involved in selective processing of perceived stimuli (selective attention) and memory representations (selective retrieval). Although this idea is compelling, given consistently found neural overlap between perceiving and remembering stimuli, recent comparisons brought evidence for overlap as well as considerable differences. Here, we present a paradigm that enables the investigation of the AtoM hypothesis from a novel perspective to gain further insight into the neural resources involved in AtoM. Selective attention in perception is often investigated as a control process that shows lingering effects on immediately following trials. Here, we employed a paradigm capable of modulating selective retrieval in a similarly dynamic manner as in such selective-attention paradigms by inducing trial-to-trial shifts between relevant and irrelevant memory representations as well as changes of the width of the internal focus on memory. We found evidence for an involvement of bilateral inferior parietal lobe and right inferior frontal gyrus in reorienting the attentional focus on previously accessed memory representations. Moreover, we could dissociate the right inferior from the parietal activation in separate contrasts, suggesting that the right inferior frontal gyrus plays a role in facilitating attentional reorienting to memory representations when competing representations have been activated in the preceding trial, potentially by resolving this competition. Our results support the AtoM theory, i.e. that ventral frontal and parietal regions are involved in automatic attentional reorienting in memory, and highlight the importance of further investigations of the overlap and differences between regions involved in internal (memory) and external (perceptual) attentional selection.

Intraoperative spinal digital subtraction angiography: technique and results.

OBJECTIVE: To evaluate technical and methodological aspects of intraoperative spinal digital subtraction angiography (ISDSA) in our clinical practice and to assess its practicability, safety, and accuracy for the surgical treatment of spinal vascular malformations. METHODS: Between August 1997 and February 2002, a total of 30 patients were treated either surgically (n = 18) or endovascularly (n = 12) for spinal vascular lesions at our institution. The clinical records of five patients who underwent ISDSA were analyzed retrospectively. The thoracic segment was involved in three patients and the medullary cone in two. RESULTS: ISDSA could be performed in four cases. In one patient, the segmental artery could not be probed sufficiently while the patient was prone. No complications occurred from the application of ISDSA. The method was beneficial for the neurosurgeon in all but one patient because the vascular anatomy of the malformation was shown with respect to the surgical approach, including the nidus, and immediate resection control could be performed before wound closure. The duration of the procedure was prolonged by 45 minutes on average. CONCLUSION: ISDSA is safe and effective, especially in surgery for complex vascular and recurrent malformations. Benefits to the patient outweigh the additional expense and prolongation of the surgical procedure.

Hypoxia-inducible factor and vascular endothelial growth factor are expressed more frequently in embolized than in nonembolized cerebral arteriovenous malformations.

OBJECTIVE: In previous studies, we documented a marked neoangiogenesis and endothelial proliferation in cerebral arteriovenous malformations (AVMs) that were embolized before surgery compared with those that were not embolized. We hypothesized that embolization caused a local hypoxia that promotes neoangiogenesis as a possible pathomechanism. To support this hypothesis, we now examined the angiogenesis-related proteins in a larger cohort of patients. In addition, we investigated hypoxia-inducible factor-1 alpha as a possible protein operative during neoangiogenesis of cerebral AVMs. METHODS: Paraffin-embedded specimens of 56 AVMs obtained from surgical resection and 14 brain tissue controls were immunohistochemically stained with antibodies to proliferating cell nuclear antigen, MIB-1, vascular endothelial growth factor, Flk1, and hypoxia-inducible factor-1 alpha by standard protocols. RESULTS: In AVMs treated with embolization before surgery (n = 35, 63%), the expression of hypoxia-inducible factor-1 alpha (P = 0.0101) and vascular endothelial growth factor (P = 0.0007) was significantly higher (Fisher's exact test) than in patients who did not have previous endovascular treatment. Differences in the expression of Flk-1 (P = 0.0798) and proliferating cell nuclear antigen (P = 0.0423) were in the same direction but were not significant when corrected for multiple testing. CONCLUSION: Our results provide circumstantial evidence that a partial occlusion of cerebral AVMs might induce local hypoxia-related neoangiogenesis. To support these data, future animal studies should be performed.

Arteriovenous malformation surrounding the trigeminal nerve--case report.

A 57-year-old man presented with subarachnoid hemorrhage due to the rupture of an arteriovenous malformation (AVM) located at the base of the root of the right trigeminal nerve. In contrast to previous similar cases, his history included no evidence of trigeminal neuralgia or sensory loss. Right vertebral artery angiography revealed a doubled superior cerebellar artery feeding the angioma nidus. The patient refused radiotherapy and preferred surgical treatment. Intraoperatively, a close relationship between arterial feeders and rootlets of the trigeminal nerve was observed. Complete removal of the malformation was achieved and confirmed angiographically. The postoperative course was complicated by subdural hygroma that required repeated drainage and eventually a shunting procedure. This case demonstrates that microsurgical treatment of a trigeminal AVM is feasible. However, stereotactic radiosurgery may be the preferred treatment option considering the potential for postoperative complications.

Visualisation of the Bonebridge by means of CT and CBCT.

BACKGROUND: With the Bonebridge, a new bone-anchored hearing aid has been available since March 2012. The objective of the study was to analyse the visualisation of the implant itself as well as its impact on the representation of the bony structures of the petrosal bone in CT, MRI and cone beam CT (CBCT). METHODS: The Bonebridge was implanted unilaterally in two completely prepared human heads. The radiological imaging by means of CBCT, 64-slice CT, 1.5-T and 3.0-T MRI was conducted both preoperatively and postoperatively. The images were subsequently evaluated from both the ENT medical and nd radiological perspectives. RESULTS: As anticipated, no visualisation of the implant or of the petrosal bones could be realised on MRI because of the interactive technology and the magnet artefact. In contrast, an excellent evaluability of the implant itself as well as of the surrounding neurovascular structures (sinus sigmoideus, skull base, middle ear, inner ear, inner auditory canal) was exhibited in both the CT and in the CBCT. CONCLUSION: The Bonebridge can be excellently imaged with the radiological imaging technologies of CT and CBCT. In the process, CBCT shows discrete advantages in comparison with CT. No relevant restrictions in image quality in the evaluation of the bony structures of the petrosal bones could be seen.

Analysis of the fossa olfactoria using cone beam tomography (CBT).

CONCLUSION: A cone beam tomography (CBT) examination of the olfactory area with its different variants allows development of an individual anatomical-radiological risk profile of the ethmoid and the identification of so-called 'dangerous ethmoids.' OBJECTIVE: Preoperative imaging performed with high-resolution CBT is imperative for analysis of the risk of injuring the olfactory fossa during sinus surgery. This study aimed to analyze the relevant parameters. METHODS: This was a retrospective, single-center study of 141 patients. The Accu-I-Tomo F17 was used. Keros type, the point of the anterior ethmoid artery, and the angle between the lateral lamella and the cribriform plate (α(lc)) were evaluated. RESULTS: The Keros types were distributed as follows: type I, 13% (α(lc): 131°); type II, 64% (α(lc): 116°); type III, 23% (α(lc): 108°) (p < 0.001). The angle of the olfactory fossa and the position of the anterior ethmoid artery (free course: α(lc)=112° vs integrated into the skull base: α(lc)= 120°) was significantly different. DISCUSSION: Surgical procedures in Keros type III where the height of the lateral lamella is much longer than in type II or type I, with an angle of nearly 107° between the lateral lamella and the cribriform plate, are expected to be safer in comparison with Keros type II with 116° and Keros type I with 131°.