Large-scale single-neuron speech sound encoding across the depth of human cortex

Understanding the neural basis of speech perception requires that we study the human brain both at the scale of the fundamental computational unit of neurons and in their organization across the depth of cortex. Here we used high-density Neuropixels arrays1-3 to record from 685 neurons across cortical layers at nine sites in a high-level auditory region that is critical for speech, the superior temporal gyrus4,5, while participants listened to spoken sentences. Single neurons encoded a wide range of speech sound cues, including features of consonants and vowels, relative vocal pitch, onsets, amplitude envelope and sequence statistics. Neurons at each cross-laminar recording exhibited dominant tuning to a primary speech feature while also containing a substantial proportion of neurons that encoded other features contributing to heterogeneous selectivity. Spatially, neurons at similar cortical depths tended to encode similar speech features. Activity across all cortical layers was predictive of high-frequency field potentials (electrocorticography), providing a neuronal origin for macroelectrode recordings from the cortical surface. Together, these results establish single-neuron tuning across the cortical laminae as an important dimension of speech encoding in human superior temporal gyrus.

Modified Neuropixels probes for recording human neurophysiology in the operating room

Neuropixels are silicon-based electrophysiology-recording probes with high channel count and recording-site density. These probes offer a turnkey platform for measuring neural activity with single-cell resolution and at a scale that is beyond the capabilities of current clinically approved devices. Our team demonstrated the first-in-human use of these probes during resection surgery for epilepsy or tumors and deep brain stimulation electrode placement in patients with Parkinson's disease. Here, we provide a better understanding of the capabilities and challenges of using Neuropixels as a research tool to study human neurophysiology, with the hope that this information may inform future efforts toward regulatory approval of Neuropixels probes as research devices. In perioperative procedures, the major concerns are the initial sterility of the device, maintaining a sterile field during surgery, having multiple referencing and grounding schemes available to de-noise recordings (if necessary), protecting the silicon probe from accidental contact before insertion and obtaining high-quality action potential and local field potential recordings. The research team ensures that the device is fully operational while coordinating with the surgical team to remove sources of electrical noise that could otherwise substantially affect the signals recorded by the sensitive hardware. Prior preparation using the equipment and training in human clinical research and working in operating rooms maximize effective communication within and between the teams, ensuring high recording quality and minimizing the time added to the surgery. The perioperative procedure requires ~4 h, and the entire protocol requires multiple weeks.

Large-scale high-density brain-wide neural recording in nonhuman primates

High-density, integrated silicon electrodes have begun to transform systems neuroscience, by enabling large-scale neural population recordings with single cell resolution. Existing technologies, however, have provided limited functionality in nonhuman primate species such as macaques, which offer close models of human cognition and behavior. Here, we report the design, fabrication, and performance of Neuropixels 1.0-NHP, a high channel count linear electrode array designed to enable large-scale simultaneous recording in superficial and deep structures within the macaque or other large animal brain. These devices were fabricated in two versions: 4416 electrodes along a 45 mm shank, and 2496 along a 25 mm shank. For both versions, users can programmatically select 384 channels, enabling simultaneous multi-area recording with a single probe. We demonstrate recording from over 3000 single neurons within a session, and simultaneous recordings from over 1000 neurons using multiple probes. This technology represents a significant increase in recording access and scalability relative to existing technologies, and enables new classes of experiments involving fine-grained electrophysiological characterization of brain areas, functional connectivity between cells, and simultaneous brain-wide recording at scale.

High-density single-unit human cortical recordings using the Neuropixels probe

The action potential is a fundamental unit of neural computation. Even though significant advances have been made in recording large numbers of individual neurons in animal models, translation of these methodologies to humans has been limited because of clinical constraints and electrode reliability. Here, we present a reliable method for intraoperative recording of dozens of neurons in humans using the Neuropixels probe, yielding up to ∼100 simultaneously recorded single units. Most single units were active within 1 min of reaching target depth. The motion of the electrode array had a strong inverse correlation with yield, identifying a major challenge and opportunity to further increase the probe utility. Cell pairs active close in time were spatially closer in most recordings, demonstrating the power to resolve complex cortical dynamics. Altogether, this approach provides access to population single-unit activity across the depth of human neocortex at scales previously only accessible in animal models.

Large-scale neural recordings with single neuron resolution using Neuropixels probes in human cortex

Recent advances in multi-electrode array technology have made it possible to monitor large neuronal ensembles at cellular resolution in animal models. In humans, however, current approaches restrict recordings to a few neurons per penetrating electrode or combine the signals of thousands of neurons in local field potential (LFP) recordings. Here we describe a new probe variant and set of techniques that enable simultaneous recording from over 200 well-isolated cortical single units in human participants during intraoperative neurosurgical procedures using silicon Neuropixels probes. We characterized a diversity of extracellular waveforms with eight separable single-unit classes, with differing firing rates, locations along the length of the electrode array, waveform spatial spread and modulation by LFP events such as inter-ictal discharges and burst suppression. Although some challenges remain in creating a turnkey recording system, high-density silicon arrays provide a path for studying human-specific cognitive processes and their dysfunction at unprecedented spatiotemporal resolution.

Chronic chemogenetic stimulation of the anterior olfactory nucleus reduces newborn neuron survival in the adult mouse olfactory bulb

During adult rodent life, newborn neurons are added to the olfactory bulb (OB) in a tightly controlled manner. Upon arrival in the OB, input synapses from the local bulbar network and the higher olfactory cortex precede the formation of functional output synapses, indicating a possible role for these regions in newborn neuron survival. An interplay between the environment and the piriform cortex in the regulation of newborn neuron survival has been suggested. However, the specific network and the neuronal cell types responsible for this effect have not been elucidated. Furthermore, the role of the other olfactory cortical areas in this process is not known. Here we demonstrate that pyramidal neurons in the mouse anterior olfactory nucleus, the first cortical area for odor processing, have a key role in the survival of newborn neurons. Using DREADD (Designer Receptors Exclusively Activated by Designer Drugs) technology, we applied chronic stimulation to the anterior olfactory nucleus and observed a decrease in newborn neurons in the OB through induction of apoptosis. These findings provide further insight into the network regulating neuronal survival in adult neurogenesis and strengthen the importance of the surrounding network for sustained integration of new neurons.

Estimation of the Endometriosis Fertility Index prior to operative laparoscopy

STUDY QUESTION

Can the Endometriosis Fertility Index (EFI) be estimated accurately before surgery?

SUMMARY ANSWER

The EFI can be estimated accurately based on mere clinical/ultrasound information, with some improvement after adding data from diagnostic laparoscopy.

WHAT IS KNOWN ALREADY

The EFI is a validated clinical instrument predicting the probability of pregnancy after endometriosis surgery without the use of ART. Being an end-of-surgery-score, it implies the decision for operative laparoscopy to be made in advance-hence, its role in the pre-surgical decision-making process remains to be established.

STUDY DESIGN, SIZE, DURATION

Single-cohort prospective observational study in 82 patients undergoing complete endometriosis excision (between June and December 2016). Two methods were used to estimate the final EFI: type A based on non-surgical clinical/ultrasound findings only, and type B based on the combination of non-surgical clinical/ultrasound findings and diagnostic laparoscopy data. To calculate EFI type A, an algorithm was created to translate non-surgical clinical/imaging information into rASRM (revised American Society of Reproductive Medicine)-and EFI points. EFI type A and type B estimates were assessed for their clinical and numerical agreement with the final EFI score. Agreement was defined as clinical if EFI scores were within the same range (0-4, 5-6, 7-10), and numerical if their difference was ≤1.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All 82 patients underwent complete laparoscopic CO2-laser excision of any rASRM stage of endometriosis in the Leuven University Fertility Centre (LUFC) of University Hospitals Leuven, a tertiary referral centre for both endometriosis and infertility. An anonymized clinical research file was created. For each patient, three different data sets were created, in order to allow the estimation of the (surgical part) EFI and of the rASRM scores, defined as follows: 'Estimated type A' contained only non-surgical clinical/imaging data, 'Estimated type B' included type A information plus the information of the diagnostic laparoscopy and 'Final EFI' included information of type A, type B and all intra-operative information required to calculate the final EFI. To calculate EFI type A without surgical information, a set of rules was used to translate pre-surgical clinical/imaging information into (rASRM and EFI points). Scoring was done by one person (C.T.), with a time interval of 4 weeks between sessions for each EFI type. Next to the EFI, also rASRM score and stage were calculated.

MAIN RESULTS AND THE ROLE OF CHANCE

Agreement rate between estimated EFI type A and final EFI was high for both the clinical (0.915; 95% CI 0.832-0.965) and numerical definition (0.878; 95% CI 0.787-0.940). Agreement rates between estimated EFI type B and final EFI were even higher (clinical (0.988; 95% CI 0.934-1.000), numerical (0.963; 95% CI 0.897-0.992)).

LIMITATIONS, REASONS FOR CAUTION

Type A estimation is dependent on high-level gynaecological ultrasound expertise, which may not be available in all clinics. A small number of patients had no prior clinical, ultrasound (hard markers) or surgical confirmation of the diagnosis of endometriosis. When applying the estimated EFI type A in clinical practice, a priori assumptions of the presence or absence of endometriosis will need to be made in adjunct to the estimation of the estimated type A EFI when counselling patients on the potential benefit of an (at least diagnostic) laparoscopy. The level of agreement for type A or B should also be taken into account when counselling patients on the type of efforts undertaken to attempt to diagnose or rule out endometriosis.

WIDER IMPLICATIONS OF THE FINDINGS

As this study reports, the EFI can be estimated accurately based on clinical/ultrasound data only without the need for any surgical data. This means that the EFI could be used as an instrument to guide joint physician-patient decision-making between surgery, ART or other fertility management options for the individualized treatment of women with endometriosis-related infertility.

STUDY FUNDING/COMPETING INTEREST(S)

During this study period, C.T. was supported by FWO (Research Fund Flanders, Grant number 1700816N) and UZ Leuven KOF (University Hospitals Leuven, Klinisch Onderzoeksfonds).The LUFC received unrestricted research grants from Ferring Pharmaceuticals and Merck SA. Gedeon Richter and MSD sponsored travel to and attendance at scientific meetings. C.M. received consultancy fees from Lumenis (paid to KU Leuven, no private revenue). T.D. has been vice-president and head of global medical affairs infertility for the multinational pharmaceutical company Merck (Darmstadt, Germany) since 1 October 2015. He continues his academic appointment on a part-time basis as Professor of Reproductive Medicine at the University of Leuven (KU Leuven). T.D. has been vice-president and head of global medical affairs infertility for the multinational pharmaceutical company Merck (Darmstadt, Germany) since October 2015. He is also a Guest Professor in Reproductive Medicine and Biology at the Department of Development and Regeneration, Group Biomedical Sciences, KU Leuven (University of Leuven), Belgium, and an Adjunct Professor at the Department of Obstetrics and Gynecology in the University of Yale, New Haven, USA. This work was initiated before he joined Merck KGaA in October 2015, and completed during the subsequent years.

TRIAL REGISTRATION NUMBER

study registration number at UZ Leuven Clinical Trial Centre: S59221.

Neuropixels 2.0: A miniaturized high-density probe for stable, long-term brain recordings

Measuring the dynamics of neural processing across time scales requires following the spiking of thousands of individual neurons over milliseconds and months. To address this need, we introduce the Neuropixels 2.0 probe together with newly designed analysis algorithms. The probe has more than 5000 sites and is miniaturized to facilitate chronic implants in small mammals and recording during unrestrained behavior. High-quality recordings over long time scales were reliably obtained in mice and rats in six laboratories. Improved site density and arrangement combined with newly created data processing methods enable automatic post hoc correction for brain movements, allowing recording from the same neurons for more than 2 months. These probes and algorithms enable stable recordings from thousands of sites during free behavior, even in small animals such as mice.

Neuropixels 2.0: A miniaturized high-density probe for stable, long-term brain recordings

Measuring the dynamics of neural processing across time scales requires following the spiking of thousands of individual neurons over milliseconds and months. To address this need, we introduce the Neuropixels 2.0 probe together with newly designed analysis algorithms. The probe has more than 5000 sites and is miniaturized to facilitate chronic implants in small mammals and recording during unrestrained behavior. High-quality recordings over long time scales were reliably obtained in mice and rats in six laboratories. Improved site density and arrangement combined with newly created data processing methods enable automatic post hoc correction for brain movements, allowing recording from the same neurons for more than 2 months. These probes and algorithms enable stable recordings from thousands of sites during free behavior, even in small animals such as mice.

Reproducibility of the Endometriosis Fertility Index: a prospective inter-/intra-rater agreement study

OBJECTIVE

To evaluate the reproducibility of the Endometriosis Fertility Index (EFI).

DESIGN

Single-cohort prospective observational study.

SETTING

University hospital.

POPULATION

Women undergoing laparoscopic resection of any rASRM-stage endometriosis.

METHODS

Details of pre- and peroperative findings were collected into a coded research file. EFI scoring was performed en-bloc by three different raters (expert-1 [C.T.], expert-2 [C.M.], junior [C.B.]). Required sample size: 71. Definitions used for agreement: clinical (scores within same range: 0-4, 5-6, 7-10) and numerical (difference ≤1 EFI point).

MAIN OUTCOME MEASURES

Primary outcome: rate of clinical agreement between two experts.

SECONDARY OUTCOMES

expert numerical agreement, clinical and numerical agreement between expert-1 and junior, and within expert-1 (intra-observer), agreement of rASRM score and -stage.

RESULTS

A near 'inter-expert' clinical agreement rate (1.000, 95% CI 0.956-1.000; P = 0.0149) was observed. The numerical agreement between two experts was also high (0.988, 95% CI 0.934-1.000); similarly, high agreement rates were observed for both 'junior-expert' comparisons (clinical 0 .963, 95% CI 0.897-0.992; numerical 0.988, 95% CI 0.934-1.000) and 'intra-expert' comparisons (clinical 0.988, 95% CI 0.934-1.000; numerical 1.000, 95% CI 0.956-1.000). Reasons for disagreements were different scoring of the least-function score and disagreements in rASRM scores. The reproducibility of the rASRM score was clearly inferior to that of the EFI for all comparisons.

CONCLUSION

The EFI can be reproduced reliably by different raters, further supporting its use in daily clinical practice as the principal clinical tool for postoperative fertility counselling/management of women with endometriosis.

TWEETABLE ABSTRACT

A study confirming the high reproducibility of the EFI substantiates its use in daily clinical practice.

Proximal and distal modulation of neural activity by spatially confined optogenetic activation with an integrated high-density optoelectrode

Optogenetic manipulations are widely used for investigating the contribution of genetically identified cell types to behavior. Simultaneous electrophysiological recordings are less common, although they are critical for characterizing the specific impact of optogenetic manipulations on neural circuits in vivo. This is at least in part because combining photostimulation with large-scale electrophysiological recordings remains technically challenging, which also poses a limitation for performing extracellular identification experiments. Currently available interfaces that guide light of the appropriate wavelength into the brain combined with an electrophysiological modality suffer from various drawbacks such as a bulky size, low spatial resolution, heat dissipation, or photovoltaic artifacts. To address these challenges, we have designed and fabricated an integrated ultrathin neural interface with 12 optical outputs and 24 electrodes. We used the device to measure the effect of localized stimulation in the anterior olfactory cortex, a paleocortical structure involved in olfactory processing. Our experiments in adult mice demonstrate that because of its small dimensions, our novel tool causes far less tissue damage than commercially available devices. Moreover, optical stimulation and recording can be performed simultaneously, with no measurable electrical artifact during optical stimulation. Importantly, optical stimulation can be confined to small volumes with approximately single-cortical layer thickness. Finally, we find that even highly localized optical stimulation causes inhibition at more distant sites. NEW & NOTEWORTHY In this study, we establish a novel tool for simultaneous extracellular recording and optogenetic photostimulation. Because the device is built using established microchip technology, it can be fabricated with high reproducibility and reliability. We further show that even very localized stimulation affects neural firing far beyond the stimulation site. This demonstrates the difficulty in predicting circuit-level effects of optogenetic manipulations and highlights the importance of closely monitoring neural activity in optogenetic experiments.

Time Multiplexed Active Neural Probe with 1356 Parallel Recording Sites

We present a high electrode density and high channel count CMOS (complementary metal-oxide-semiconductor) active neural probe containing 1344 neuron sized recording pixels (20 µm × 20 µm) and 12 reference pixels (20 µm × 80 µm), densely packed on a 50 µm thick, 100 µm wide, and 8 mm long shank. The active electrodes or pixels consist of dedicated in-situ circuits for signal source amplification, which are directly located under each electrode. The probe supports the simultaneous recording of all 1356 electrodes with sufficient signal to noise ratio for typical neuroscience applications. For enhanced performance, further noise reduction can be achieved while using half of the electrodes (678). Both of these numbers considerably surpass the state-of-the art active neural probes in both electrode count and number of recording channels. The measured input referred noise in the action potential band is 12.4 µVrms, while using 678 electrodes, with just 3 µW power dissipation per pixel and 45 µW per read-out channel (including data transmission).

A closed-loop compressive-sensing-based neural recording system

OBJECTIVE

This paper describes a low power closed-loop compressive sensing (CS) based neural recording system. This system provides an efficient method to reduce data transmission bandwidth for implantable neural recording devices. By doing so, this technique reduces a majority of system power consumption which is dissipated at data readout interface. The design of the system is scalable and is a viable option for large scale integration of electrodes or recording sites onto a single device.

APPROACH

The entire system consists of an application-specific integrated circuit (ASIC) with 4 recording readout channels with CS circuits, a real time off-chip CS recovery block and a recovery quality evaluation block that provides a closed feedback to adaptively adjust compression rate. Since CS performance is strongly signal dependent, the ASIC has been tested in vivo and with standard public neural databases.

MAIN RESULTS

Implemented using efficient digital circuit, this system is able to achieve >10 times data compression on the entire neural spike band (500-6KHz) while consuming only 0.83uW (0.53 V voltage supply) additional digital power per electrode. When only the spikes are desired, the system is able to further compress the detected spikes by around 16 times. Unlike other similar systems, the characteristic spikes and inter-spike data can both be recovered which guarantes a >95% spike classification success rate. The compression circuit occupied 0.11mm(2)/electrode in a 180nm CMOS process. The complete signal processing circuit consumes <16uW/electrode.

SIGNIFICANCE

Power and area efficiency demonstrated by the system make it an ideal candidate for integration into large recording arrays containing thousands of electrode. Closed-loop recording and reconstruction performance evaluation further improves the robustness of the compression method, thus making the system more practical for long term recording.

Towards a noise prediction model for in vivo neural recording

The signal-to-noise ratio of in vivo extracellular neural recordings with microelectrodes is influenced by many factors including the impedance of the electrode-tissue interface, the noise of the recording equipment and biological background noise from distant neurons. In this work we study the different noise sources affecting the quality of neural signals. We propose a simplified noise model as an analytical tool to predict the noise of an electrode given its geometrical dimensions and impedance characteristics. With this tool we are able to quantify different noise sources, which is important to determine realistic noise specifications for the design of electronic neural recording interfaces.

Targeting bed nucleus of the stria terminalis for severe obsessive-compulsive disorder: more unexpected lead placement in obsessive-compulsive disorder than in surgery for movement disorders

BACKGROUND

In preparation for a multicenter study, a protocol was written on how to perform surgical targeting of the bed nucleus of the stria terminalis, based on the lead implantation experience in patients with treatment-refractory obsessive-compulsive disorder (OCD) at the Universitaire Ziekenhuizen Leuven (UZ Leuven). When analyzing the postoperative images, we were struck by the fact that the difference between the postoperative position of the leads and the planned position seemed larger than expected.

METHODS

The precision of targeting in four patients with severe OCD who received bilateral model 3391 leads (Medtronic) was compared with the precision of targeting in the last seven patients who underwent surgery at UZ Leuven for movement disorders (four with Parkinson disease and three with essential tremor; all received bilateral leads). Because the leads implanted in six of the seven patients with movement disorders were model 3387 leads (Medtronic), targeting precision was also analyzed in four patients with OCD in whom model 3387 leads were implanted in the same target as the other patients with OCD.

RESULTS

In the patients with OCD, every implanted lead deviated at least 1.3 mm from its intended position in at least one of three directions (lateral, anteroposterior, and depth), whereas in the patients with movement disorders, the maximal deviation of any of all implanted leads was 1.3 mm. The deviations in lead placement were comparable in patients with OCD who received a model 3387 implant and patients who received a model 3391 implant. In the patients with OCD, all leads were implanted more posteriorly than planned.

CONCLUSIONS

The cause of the posterior deviation could not be determined with certainty. The most likely cause was an increased mechanical resistance of the brain tissue along the trajectory when following the targeting protocol compared with the trajectories classically used for subthalamic nucleus or ventral intermediate nucleus of the thalamus stimulation.

Neuronal activity in the bed nucleus of the stria terminalis in a rat model for obsessive-compulsive disorder

In search of a new potential target for deep brain stimulation in patients with obsessive-compulsive disorder (OCD), we evaluated the single-cell activity of neurons in the bed nucleus of the stria terminalis (BST) in urethane-anesthetized rats in an animal model for OCD, the schedule-induced polydipsia (SIP) model, and compared this to the BST activity in control rats and to a third group of rats which were introduced in the model but did not develop the SIP, and thus were considered resistant. We compared the firing rate and firing pattern of BST neurons between these groups, between hemispheres and made a correlation of the firing rate and firing pattern to the position in the BST. The variability of BST neurons in SIP rats was lower and the randomness higher than BST neurons in control rats or resistant rats. The firing rate of BST neurons in SIP rats was significantly higher and the burst index lower than BST neurons in resistant rats but not in control rats. Also, neurons from the right hemisphere in the SIP group had a higher burst index than neurons from the left hemisphere. However, this is opposite in the resistant and control group. Third, we found a higher bursting index with increasing (more ventral) depth of recording. These findings suggest that schedule-induced polydipsia, which models compulsive behavior in humans, induces a change in firing behavior of BST neurons.

Histological alterations induced by electrode implantation and electrical stimulation in the human brain: a review

Objectives.  Electrical brain stimulation is used as a treatment for patients with intractable chronic pain and movement disorders. However, the implantation of electrodes and electrical stimulation may induce histological changes around the electrode tip. We aimed to review the histological changes in humans that were electrically stimulated in the brain. Methods.  We traced 26 autopsy studies of which 19 patients received cerebellar stimulation and 37 patients deep brain stimulation. Results.  Electrode implantation and electrical stimulation induced in part of the cases formation of a fibrous sheath around the electrode, loss of fairly large neurons, and limited gliosis. Macroscopic lesions were present in only some cases, mostly due to pulling at the extension cable in the postoperative evaluation period preceding definite implantation of the electrode wire and stimulator. Conclusions.  Electrical brain stimulation induces histological changes in some patients. According to electrical brain stimulation studies in animals, these changes can be related to the charge and charge density per phase (and their interaction).

Chronic behavior evaluation of a micro-machined neural implant with optimized design based on an experimentally derived model

Understanding the mechanical interactions between implants and the surrounding tissue is known to have an important role for improving the bio-compatibility of such devices. Using a recently developed model, a particular micro-machined neural implant design aiming the reduction of insertion forces dependence on the insertion speed was optimized. Implantations with 10 and 100 μm/s insertion speeds showed excellent agreement with the predicted behavior. Lesion size, gliosis (GFAP), inflammation (ED1) and neuronal cells density (NeuN) was evaluated after 6 week of chronic implantation showing no insertion speed dependence.

Parenthood motives, well-being and disclosure among men from couples ready to start treatment with intrauterine insemination using their own sperm or donor sperm

BACKGROUND

As pregnancy and childbirth have long been considered women's issues and male infertility has long been surrounded by taboo, limited research has focused on the experience of infertile men. The purpose of this study was to compare male motives for parenthood, male well-being and disclosure patterns concerning the method of conception among men from couples starting treatment with IUI using their own sperm (autologous sperm recipient, ASR) or donor sperm (donor sperm recipient, DSR).

METHODS

This prospective study included 46 DSR- and 151 ASR-couples. Self-report questionnaires assessing parenthood motives, well-being and disclosure patterns concerning the method of conception were administered to both men and women prior to treatment. Unpaired T-tests and Fisher's exact tests were used to test for significant differences.

RESULTS

When compared with ASR-men, DSR-men expect more positive effects from parenthood on relationships and feelings of fulfilment, and report less negative effects of infertility on sexuality, but a lower self-image and more guilt. DSR-men plan to disclose the method of conception less frequently and have so far disclosed to a lesser degree than ASR-men.

CONCLUSIONS

DSR-men feel differently about parenthood and infertility compared with ASR-men, and their higher expectations combined with lower self-esteem need (more) attention during counselling.

In vitro and in vivo electrochemical characterization of a microfabricated neural probe

The electrochemical behavior of neural implants with 50 microm-diameter platinum electrodes was tested during acute implantations in the motor cortex of anesthetized rats. Custom Ag|AgCl reference electrodes were prepared that could be co-implanted with the probes. The results obtained in vivo are compared with in vitro measurements performed in buffered saline solution (PBS) with and without the addition of bovine serum albumin (BSA). The presence of BSA clearly altered the performance of the electrodes which was studied by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), voltage transient measurements (VT) and monitoring of the open circuit potential (OCP). We found that hydrogen gas evolved at 1.22 A/cm(2) in BSA-free PBS whereas in BSA-containing PBS it occurred already at 0.51 A/cm(2).

The effects of electrical stimulation or an electrolytic lesion in the mediodorsal thalamus of the rat on survival, body weight, food intake and running activity in the activity-based anorexia model

The glucose metabolism in the mediodorsal thalamus (MD) is increased in rats in the activity-based anorexia (ABA) model. In patients, electrical stimulation in hyperactive brain regions reduced symptoms in e.g. major depressive disorder and cluster headache. In two blinded randomised controlled experiments, we therefore examined the effects of high-frequency electrical stimulation and an electrolytic lesion in the MD in a validated rat model for anorexia nervosa. The ABA model was successfully replicated in all our experiments, with a reduction in body weight, food intake, and survival time and an increase in running activity. In a first experiment, we evaluated the effect of electrical stimulation or a curative lesion in the MD on survival, body weight, food intake and locomotor activity in ABA rats. Electrical MD stimulation or an electrolytic MD lesion did not improve the symptoms of rats in the ABA model, compared to control groups. In a second experiment, we investigated the effect of a preventive electrolytic lesion in the MD on rats in the ABA model. Although there was no significant improvement of survival, body weight and food intake, locomotor activity was significantly reduced in the lesion group compared to the control group. Apart from this positive effect on running activity, we found no convincing evidence for the suitability of the MD as a neuromodulation target for anorexia nervosa patients.

Electrical stimulation in the lateral hypothalamus in rats in the activity-based anorexia model

Object

One quarter of patients with anorexia nervosa have a poor outcome and continue to suffer chronically or die. Electrical brain stimulation may be of therapeutic benefit in some of these patients; however, the brain target for inducing symptom relief is unknown. In this study, the authors evaluated the effects of acute and chronic electrical stimulation in the lateral hypothalamus on food intake, locomotor activity, and survival time in rats in an activity-based anorexia model.

Methods

In an acute experiment, the authors electrically stimulated at 100 Hz and 0, 25, 50 and 75% of the maximal stimulation amplitude (that is, the amplitude leading to severe side effects) in the lateral hypothalamus on consecutive days during 4 test sessions in 10 rats and evaluated food intake and locomotor activity. In a chronic experiment, they compared food intake, wheel revolutions, and survival time between 6 rats that underwent electrical stimulation in the lateral hypothalamus (50% of maximal stimulation amplitude) and 8 rats that did not undergo stimulation.

Results

In the acute experiment, overall electrical stimulation (25, 50, and 75% combined) and stimulation at 75% of the maximal stimulation amplitude significantly decreased the locomotor activity. However, if the authors omitted results of 1 rat, in which the electrode tip was not located in the lateral hypothalamus on one side but rather in the supraoptic chiasm, the remaining results did not yield significance. No other differences were observed.

Conclusions

When the findings of the current study are extrapolated to patients with anorexia nervosa, the authors do not expect major effects on symptoms with electrical stimulation at high frequency in the lateral hypothalamus.

Cancer Genetics Service Provision: A Comparison of Seven European Centres

OBJECTIVE

To conduct a survey in seven European cancer genetics centres to compare service provision, organisation and practices for familial breast and colon cancer consultations and testing. Information was obtained on aspects of services both nationally and locally.

METHODS

A detailed survey questionnaire was adapted collaboratively to obtain the required information. Initial survey data were collected within each centre and interim results were discussed at two European Workshops. Where differences in practice existed, details were clarified to ensure accuracy and adequacy of information. Participating centres were Haifa (Israel), Hannover (Germany), Leiden (The Netherlands), Leuven (Belgium), Manchester (UK), Marseille (France) and Milan (Italy), representing countries with populations ranging from 6.5 to 80 million.

RESULTS

The European countries diverged in regard to the number of cancer genetics centres nationally (from 8 in Belgium to 37 in France), and the average population served by each centre (from 0.59 million in Israel to 3.32 million in Italy). All centres offered free care at the point of access, but referral to specialist care varied according to national health care provision. At a centre level, staff roles varied due to differences in training and health care provision. The annual number of counsellees seen in each participating centre ranged from 200 to over 1,700. Access to breast surveillance or bowel screening varied between countries, again reflecting differences in medical care pathways. These countries converged in regard to the wide availability of professional bodies and published guidelines promoting aspects of service provision. Similarities between centres included provision of a multidisciplinary team, with access to psychological support, albeit with varying degrees of integration. All services were dominated (70-90%) by referrals from families with an increased risk of breast cancer despite wide variation in referral patterns. Collection of pedigree data and risk assessment strategies were broadly similar, and centres used comparable genetic testing protocols. Average consultation times ranged between 45 and 90 min. All centres had access to a laboratory offering DNA testing for breast and bowel cancer-predisposing genes, although testing rates varied, reflecting the stage of service development and the type of population. Israel offered the highest number of genetic tests for breast cancer susceptibility because of the existence of specific founder mutations, in part explaining why the cancer genetics service in Haifa differed most from the other six.

CONCLUSION

Despite considerable differences in service organisation, there were broad similarities in the provision of cancer genetic services in the centres surveyed.

General practitioners and predictive genetic testing for late-onset diseases in Flanders: what are their opinions and do they want to be involved?

OBJECTIVE

Investigate the attitudes of general practitioners (GPs) concerning predictive testing for late-onset diseases, as well as the perception of their own role in this context.

METHODS

356 GPs received mail questionnaires with telephone pre-notifications and reminders.

RESULTS

The questionnaire was returned by 60% (n=215). The GPs' attitudes toward predictive testing for breast cancer, thyroid cancer, Alzheimer disease and Huntington's disease were influenced by the availability and the type of preventive and therapeutic options, the age of onset of the disease as well as by ethical concerns. Regarding a possible tasks for GPs, most of the GPs focussed on gate-keeping aspects, such as providing information and making referrals.

CONCLUSION

The GPs were supportive of a limited role for general practice in predictive testing. Genetic education for GPs is needed, with attention to non-directiveness and the characteristic psychosocial and ethical implications of this particular type of genetic testing.

The language of uncertainty in genetic risk communication: framing and verbal versus numerical information

Within a group of 300 medical students, two characteristics of risk communication in the context of a decision regarding prenatal diagnosis for cystic fibrosis are manipulated: verbal versus numerical probabilities and the negative versus positive framing of the problem (having a child with versus without cystic fibrosis). Independently of the manipulations, most students were in favor of prenatal diagnosis. The effect of framing was only significant in the conditions with verbal information: negative framing produced a stronger choice in favor of prenatal diagnosis than positive framing. The framing effect in the verbal conditions and its absence in the numerical conditions are explained by the dominance of the problem-occurrence orientation in health matters as well as a recoding process which is more likely to occur in the numerical (the probability "1-P" switches to its counterpart "P") than in the verbal conditions. The implications for the practice of genetic counseling are discussed.

Cognitive representations of breast cancer, emotional distress and preventive health behaviour: a theoretical perspective

Individuals at high risk for developing breast and/or ovarian cancer are faced with difficult decisions regarding genetic testing, cancer prevention and/or intensive surveillance. Large interindividual differences exist in the uptake of these health-related services. This paper is aimed at understanding and predicting how people emotionally and behaviourally react to information concerning genetic predisposition to breast/ovarian cancer. For this purpose, the self-regulation model of illness representations is elaborated. This model suggests that health-related behaviour is influenced by a person's cognitive and emotional representation of the health threat. These representations generate coping behaviour aimed at resolving the objective health problems (problem-focussed coping) and at reducing the emotional distress induced by the health threat (emotion-focussed coping). Based on theoretical considerations and empirical studies, four interrelated attributes of the cognitive illness representation of hereditary breast/ovarian cancer are described: causal beliefs concerning the disease, perceived severity, perceived susceptibility to the disease and perceived controllability. The paper also addresses the complex interactions between these cognitive attributes, emotional distress and preventive health behaviour.

The psychological complexity of predictive testing for late onset neurogenetic diseases and hereditary cancers: implications for multidisciplinary counselling and for genetic education

Increasing knowledge about the human genome has resulted in the availability of a steadily increasing number of predictive DNA-tests for two major categories of diseases: neurogenetic diseases and hereditary cancers. The psychological complexity of predictive testing for these late onset diseases requires careful consideration. It is the main aim of the present paper to describe this psychological complexity, which necessitates an adequate and systematic multidisciplinary approach, including psychological counselling, as well as ongoing education of professionals and of the general public. Predictive testing for neurogenetic diseases--in an adequate counselling context--so far elicits optimism regarding the short- and mid-term impact of the predictive test result. The psychosocial impact has been most widely studied for Huntington's disease. Longitudinal studies are of the utmost importance in evaluating the long-term impact of predictive testing for neurogenetic diseases on the tested person and his/her family. Given the more recent experience with predictive DNA-testing for hereditary cancers, fewer published scientific data are available. Longitudinal research on the mid- and long-term psychological impact of the predictive test result is essential. Decision making regarding health surveillance or preventive surgery after being detected as a carrier of one of the relevant mutations should receive special attention. Tailoring the professional approach--inside and outside genetic centres--to the families' needs is a continuous challenge. Even if a continuous effort is made, several important questions remain unanswered, last but not least the question regarding the best strategy to guarantee that the availability of predictive genetic testing results in a reduction of suffering caused by genetic disease and in an improvement of the quality of life of families confronted with genetic disease.

Predictive testing for hereditary breast and ovarian cancer: a psychological framework for pre-test counselling

Since the identification of two breast-ovarian cancer susceptibility genes (BRCA1/2), predictive testing for hereditary breast/ovarian cancer (HBOC) has been available. Given the complexity and uncertainties of HBOC and the potential impact of predictive testing on psychological well-being, we offer the test applicants a combination of information-oriented and psychological counselling. In this paper, we describe the multidisciplinary approach for predictive testing for HBOC as a clinical service in Leuven, hereby focusing on psychological and decision counselling practice. Attention is paid to the theoretical framework used for pre-test psychological counselling in Leuven. We discuss three important interacting dimensions of psychological counselling: individual emotional support, decision counselling and support of the family communication process. Decision counselling consists of an evaluation of the cognitive and the emotional processing of the information given and strategies and resources for coping. This serves as a starting point to facilitate free informed decision making. Scenario development is used as a decision aid.

Uptake and Impact of Carrier Testing for Cystic Fibrosis

The first aim of the paper is to review research into the uptake of carrier testing for cystic fibrosis and into the impact of carrier testing on self-esteem, risk perception and reproductive decisions. The second aim is to connect the most important findings to psychological theories and concepts. Thirdly, we infer practical suggestions for genetic counselling. The uptake of genetic testing for CF could be explained by at least three (complementary) interrelated psychological concepts: the (lack of) genetic information, the individual's health beliefs and the concept of coping with a health threat. Cognitive and/or emotional coping mechanisms played also an important role in preserving self-esteem after a positive carrier test and in the subjective evaluation of the residual risk after a negative test result. Suggestions are given regarding genetic counselling in general and regarding free informed decision making.

Attitudes toward predictive testing for Alzheimer's disease in a student population

Attitudes toward predictive testing for Alzheimer's disease and knowledge about this disease were investigated in a group of medical and psychology students. Overall, knowledge was poor and their own chance of getting Alzheimer's disease was mostly perceived as small. About half the students thought the development of a predictive test for Alzheimer's disease important, while the other half held the opposite view. Considerable variability was also observed in the judgement of the (dis)advantages of such a test. Only a minority of the students would like to have a predictive test themselves. Important arguments against a predictive test concerned the absence of a treatment for Alzheimer's disease and the emotional burden of a positive test result. Arguments in favour dealt with the ability to make plans for the future and to prepare oneself for the disease. The divergence in attitudes and opinions reflects the complexity of predictive testing for Alzheimer's disease. Stepwise regression revealed that knowledge about Alzheimer's disease and, to a lesser extent, risk perception are significant predictors of attitudes toward predictive testing. However, they only explain a small part of the variance in attitudes. Moreover, why attitudes are less positive when knowledge and perceived susceptibility increase is not clear.

Risk perception after CF carrier testing and impact of the test result on reproductive decision making

A correct interpretation of the result of a CF carrier test and a correct understanding of the risk of having a CF child is complicated by the limited sensitivity of the DNA test. The present paper addresses this problem, with special attention for the residual risk after a negative test result. Secondly, the impact of the test results on child bearing decisions is evaluated. Seventy percent of a sample of 200 subjects tested in the Center for Human Genetics in Leuven answered a mailed questionnaire and participated in an interview. Knowledge about the recessive transmission of CF was weak. In the case of both partners receiving a negative test result, more than half the subjects were not aware of the restrictions of DNA testing, and were convinced that there was no residual risk. Two thirds of the subjects from the 'carrier + negative test result couples' were aware of the residual risk of having a CF child. This risk did not hamper further reproduction. Carriers who were single or whose partner was not tested, had much difficulties to understand the risk. Although most of them had no idea about their exact risk level, it influenced their childbearing decisions to some extent. It was also shown that the own risk of having a CF child had an impact on attitudes toward reproduction in hypothetical situations with different risk levels.

Attitudes toward predictive testing for Alzheimer's disease in a student population

Attitudes toward predictive testing for Alzheimer's disease and knowledge about this disease were investigated in a group of medical and psychology students. Overall, knowledge was poor and their own chance of getting Alzheimer's disease was mostly perceived as small. About half the students thought the development of a predictive test for Alzheimer's disease important, while the other half held the opposite view. Considerable variability was also observed in the judgement of the (dis)advantages of such a test. Only a minority of the students would like to have had a predictive test themselves. Important arguments against a predictive test concerned the absence of a treatment for Alzheimer's disease and the emotional burden of a positive test result. Arguments in favour dealt with the ability to make plans for the future and to prepare oneself for the disease. The divergence in attitudes and opinions reflects the complexity of predictive testing for Alzheimer's disease. Stepwise regression revealed that knowledge about Alzheimer's disease and, to a lesser extent, risk perception are significant predictors of attitudes toward predictive testing. However, they only explain a small part of the variance in attitudes. Moreover, why attitudes are less positive when knowledge and perceived susceptibility increase is not clear.

The CF carrier status is not associated with a diminished self-concept or increased anxiety: results of psychometric testing after at least 1 year

To evaluate whether the CF carrier status has any lasting effect on anxiety and on self-concept at least 1 year after the disclosure of the test result, an in-depth interview and additional psychological tests were administered in a group of adults who participated in a previous study which suggested a slight stigmatizing effect of the CF carrier status. Besides carrier status, the role of a second factor-degree of relationship-was investigated. Analysis of Variance (MANOVA or ANOVA) revealed no effect on state and trait anxiety (STAI) and almost no effect on the six subscales of the Tennessee Self-Concept Scale. The absence of a lasting negative effect of the CF carrier status on anxiety and self-concept is a very important finding. Nevertheless, an intriguing significant interaction effect was found: the group of sibs carrying the CF gene felt less integrated in the family than the group of non-carrier sibs. This effect of carrier status was not found in the more distant relatives. It is important to pay sufficient attention to this problem during genetic counseling when brothers or sisters of a CF patient receive a test result.

Adolescents' attitude towards carrier testing for cystic fibrosis and its relative stability over time

Attitudes towards cystic fibrosis (CF) carrier testing, benefits of and barriers to having such a test were assessed within a randomly selected group of high school students in Flanders, after they had received sufficient basic information about the nature and the mode of inheritance of CF. Attitudes towards carrier testing for CF were not negative, but the majority preferred to wait to have a test. This result changed little after 6 months. A hypothetical testing offer from the Medical School Health Service elicited positive answers from nearly two thirds, suggesting that such an offer may function as a cue to action. Nevertheless, the appropriateness of such an offer may be questioned, considering the disadvantages of testing adolescents. Concern about a negative impact of the carrier status on self-image was reported by 10% of the students. These findings suggest that education about genetics is not only a prerequisite for allowing more informed decisions about CF carrier testing, but also for avoiding negative psychosocial effects of such a test.

Adolescents' opinions about genetic risk information, prenatal diagnosis, and pregnancy termination

Advances in genetics create increasing possibilities of diagnosing and preventing genetic disease. In most countries, the community is poorly informed about the role of genetic factors in human disease and about genetic testing and its social, emotional, and ethical implications. School education about genetics may improve this situation. Students are, of course, the adults of the future and the potential users of the new genetic tests. To gain further insight into the perception of genetic risk of adolescents and their perception of the new genetic techniques and as a starting point for setting up an adequate information campaign in Flanders, we assessed the opinions and beliefs of students with regard to health, genetic diseases, genetic risk, and genetic testing.

A standardised interview and questionnaire were administered within the scope of the two yearly medical check up of 166 fifth grade students. They were randomly selected from the group of all fifth grade high school students in seven different schools.

This paper focuses on the attitudes of adolescents towards obtaining genetic information, towards prenatal diagnosis and pregnancy termination. Adolescents in Flanders are interested in being informed about genetic risks and genetic diseases and in making use of prenatal diagnosis because they want to make informed reproductive decisions in the future and to be emotionally prepared for the birth of an affected child. They adopt a critical attitude towards pregnancy termination. The association between these attitudes and several relevant factors was investigated. This showed significant correlations between some attitudes and general health related prevention, perceived burden of genetic diseases, the importance of the value “own health”, the perceived role of society, and the regularity of religious practice. Some points for special attention were formulated with regard to information campaigns for adolescents.

Reply to the commentary on Decruyenaere et al "adolescents' opinions about genetic risk information, prenatal diagnosis, and pregnancy termination"

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A stigmatizing effect of the carrier status for cystic fibrosis?

The emotional impact of carrier detection for CF was assessed in a group of adults tested before 1992. Of the 200 adults who received a mailed questionnaire, 70% participated. One third were CF gene carriers. The Health Orientation Scale (HOS) was used to evaluate perceived feelings about three situations: (a) How would you describe your feelings about yourself when you consider your test result? (b) How do you think most people feel when they are told that they carry the CF gene? (c) How do you think most people feel when they are told that they do not carry the CF gene? Comparing the profiles of CF carriers and non-carriers, we found that carriers had significantly less positive feelings about themselves than non-carriers. Carriers as well as non-carriers attribute significantly more negative feelings to most carriers of the CF gene than to most non-carriers. Moreover, carriers of the Cf gene attribute more negative feelings to other CF carriers than to themselves. Analysis of variance revealed a significant effect of carrier status on self-description, as well as a significant effect of carrier status and degree of kinship with a CF patient on feelings attributed to most carriers. Although these results suggest some danger of stigmatization of CF carriers, the cognitive bias of 'illusory superiority' seems to counterbalance some of its effects.