Investigation of the stimulation capabilities of a high-resolution neurorecording probe for the application of closed-loop deep brain stimulation

Deep brain stimulation is an established surgical treatment for several neurological and movement disorders, such as Parkinson's disease, in which electrostimulation is applied to targeted deep nuclei in the basal ganglia through implanted electrode leads. Recent technological improvements in the field have focused on the theoretical advantage of current steering and adaptive (closed-loop) deep brain stimulation. Current steering between several active electrodes would allow for improved accuracy when targeting the desired brain structures. This has the additional benefit of avoiding undesired stimulation of neural tracts that are related to side effects, e.g., internal capsule fibres of passage in subthalamic nucleus deep brain stimulation. Closed-loop deep brain stimulation is based on the premise of continuous recording of a proxy for pathological neural activity (such as beta-band power of measured local field potentials in patients with Parkinson's disease) and accordingly adapting the used stimulus parameters. In this study, we investigate the suitability of an existing highresolution neurorecording probe for high-precision neurostimulation. If a subset of the probe's recording electrodes can be used for stimulation, then the probe would be a suitable candidate for closed-loop deep brain stimulation. A finiteelement model is used to calculate the electric potential, induced by current injection through the high-resolution probe, for different sets of active electrodes. Volumes of activated tissue are calculated and a comparison is made between the highresolution probe and a conventional stimulation lead. We investigate the capability of the probe to shift the volume of activated tissue by steering currents to different sets of active electrodes. Finally, safety limits for the injected current are used to determine the size of the volume in which neurons can be activated with the relatively small electrodes patches on the highresolution probe

Incomplete and Inaccurate Vocal Imitation after Knockdown of FoxP2 in Songbird Basal Ganglia Nucleus Area X

The gene encoding the forkhead box transcription factor, FOXP2, is essential for developing the full articulatory power of human language. Mutations of FOXP2 cause developmental verbal dyspraxia (DVD), a speech and language disorder that compromises the fluent production of words and the correct use and comprehension of grammar. FOXP2 patients have structural and functional abnormalities in the striatum of the basal ganglia, which also express high levels of FOXP2. Since human speech and learned vocalizations in songbirds bear behavioral and neural parallels, songbirds provide a genuine model for investigating the basic principles of speech and its pathologies. In zebra finch Area X, a basal ganglia structure necessary for song learning, FoxP2 expression increases during the time when song learning occurs. Here, we used lentivirus-mediated RNA interference (RNAi) to reduce FoxP2 levels in Area X during song development. Knockdown of FoxP2 resulted in an incomplete and inaccurate imitation of tutor song. Inaccurate vocal imitation was already evident early during song ontogeny and persisted into adulthood. The acoustic structure and the duration of adult song syllables were abnormally variable, similar to word production in children with DVD. Our findings provide the first example of a functional gene analysis in songbirds and suggest that normal auditory-guided vocal motor learning requires FoxP2

Studien zur Evolution und Funktion des FoxP2-Gens in Singvögeln

Title and Table of Content Introduction Material and Methods Results Discussion References AppendixThe FoxP2 gene, which encodes a forkhead box transcription factor is essential for developing the full articulatory power of human language. Mutations of FoxP2 cause a speech and language disorder which compromises the fluent production of words and affects the correct use and comprehension of grammar. FoxP2 patients have structural and functional abnormalities in the striatum of the basal ganglia, which also expresses high levels of FoxP2. But how FoxP2 affects brain function remains unknown. The first part of my thesis addresses this question in songbirds, since learning to speak bears behavioral and neural parallels to how songbirds learn to sing. In zebra finches, FoxP2 expression increases in Area X, a basal ganglia structure necessary for song acquisition, during the time when song learning occurs. In canaries, FoxP2 expression levels in Area X are similarly associated with vocal plasticity. Using lentivirus-mediated RNAi in zebra finches we shown that FoxP2 knockdown in Area X impairs song learning. This suggests that auditory-guided vocal learning in the basal ganglia requires FoxP2. These findings provide the first example of a functional gene analysis in songbirds, a widely studied neuroethological model system. Finally, the fact that FoxP2 is involved in both birdsong and speech suggests that the molecular substrate from which the uniquely human capacity of language evolved might not be exclusive to the hominid lineage. Consistent with this, the FoxP2 protein sequence shows a high degree of conservation among vertebrates. However, human FoxP2 contains changes in amino-acid coding and a pattern of nucleotide polymorphisms which suggests that it has been the target of selection during recent human evolution. This indicates that FoxP2 might have been pivotal for the development of human language. Although language is a uniquely human trait, learned vocalizations are also found in a few other species, among them whales, bats, and most prominently in three orders of birds. Thus, in the second part of my thesis I compared the FoxP2 sequence from 11 bird species covering the 3 orders of vocally learning birds as well as 3 orders in which vocal learning did not evolve and the crocodile, the closest non-avian relative. There was no evidence for an association between specific amino acid substitutions and the capacity for vocal learning. In conclusion, FoxP2 was either not directly involved in the evolution of vocal-learning in birds or selection acted on the large non-coding regions of FoxP2, which were not examined in this study.Mutationen im FoxP2-Gen führen zu einer Sprech- und Sprachstörung (developmental verbal dyspraxia, DVD), welche vor allem durch gestörte Artikulationsfähigkeit und Probleme mit dem Verständnis und Gebrauch von Grammatik gekennzeichnet ist. Patienten mit DVD zeigen funktionelle und strukturelle Auffälligkeiten im Striatum der Basalganglien. Im Striatum ist FoxP2 auch stark exprimiert, aber wie genau sich die FoxP2 Mutationen auf die Sprachfähigkeit auswirken ist unbekannt. Im ersten Teil meiner Dissertation nähere ich mich dieser Fragestellung durch Experimente in Singvögeln, da zwischen Sprachlernen und Gesangslernen viele neurobiologische und ethologische Parallelen bestehen. Das Expressionsmuster von FoxP2 in Gehirn der Singvögel stimmt mit den bereits beschriebenen Mustern aus der Maus und dem Mensch überein. Darüber hinaus ist in Area X von Zebrafinken, einer für das Gesangslernen essentiellen Struktur, die Expression von FoxP2 während der Gesangslernphase höher als davor und danach. Das Expressionsniveau von FoxP2 korreliert also zeitlich mit der Lernphase. In Kanarienvögeln ist FoxP2 ebenfalls dann besonders stark experimentiert, wenn sich die Vögel in einer plastischen Phase ihres Gesangs befinden. Dies weist auf eine mögliche Funktion von FoxP2 bei der Gesangsplastizität hin. Durch die Verwendung eines lentiviralen Expressionssystems zur Induktion von RNAi im Zebrafinken wird gezeigt, daß die experimentelle Reduktion von FoxP2 das Gesangslernen tatsächlich beeinträchtigt. Das bedeutet, daß FoxP2 notwendig für auditorisch geleitetes, vokales Lernen ist. Diese Ergebnisse liefern das erste Beispiel einer funktionellen Genanalyse in einem Singvogel. Darüber hinaus deutet die Tatsache, daß FoxP2 sowohl notwendig für die Sprache des Menschen als auch den Gesang von Singvögeln ist darauf hin, daß die Ähnlichkeiten zwischen Gesangslernen und Spracherwerb bis auf die molekulare Ebene hinabreichen. Das molekulare Substrat für die Evolution der menschlichen Sprachfähigkeit ist demnach nicht ausschließlich bei den Hominiden zu finden. Im Einklang damit steht, daß die Proteinsequenz von FoxP2 in allen Vertebraten extrem stark konserviert ist. Allerdings wurden beim Menschen Aminosäuresubstitutionen und ein Muster an Sequenzvariationen gefunden, welche darauf schließen lassen, daß FoxP2 in der jüngeren Vergangenheit der menschlichen Evolution unter Selektionsdruck gestanden hat. FoxP2 könnte demnach entscheidend zur Evolution von Sprache beigetragen haben. Zwar ist Sprache dem Menschen vorbehalten, aber einige wenige Arten, darunter Wale, Fledermäuse und drei Ordnungen von Vögeln, sind in der Lage ihre Vokalisation durch Imitation zu erlernen. Im zweiten Teil meiner Dissertation, untersuche ich daher, ob ein Zusammenhang zwischen der Fähigkeit zur erlernten Vokalisation und dem Muster an Aminosäuresubstitutionen im FoxP2-Gen besteht. Hierzu werden die FoxP2-Sequenzen von 11 Vogelspezies, darunter Vertreter aus den drei Ordnungen von Gesangslernern und aus drei nicht-lernenden Vogelordnungen verglichen. Zur besseren phylogenetischen Einordnung wird zusätzlich die FoxP2-Sequenz des Krokodils, dem nächsten Verwandten der Vögel, analysiert. Es zeigen sich jedoch keine Hinweise darauf, daß die Fähigkeit zum Gesangslernen mit einer bestimmten FoxP2-Sequenz einhergeht. Demnach war FoxP2 entweder nicht direkt an der Evolution des Gesangslernens beteiligt, oder aber die Selektion hat auf die nicht-kodierenden Regionen von FoxP2 gewirkt, welche hier nicht untersucht wurden

Ultra-compact integrated electrical and optical silicone probe for recording and illumination in vivo

status: publishe

Neuron-Type-Specific Signals for Reward and Punishment in the Ventral Tegmental Area

Dopamine has a central role in motivation and reward. Dopaminergic neurons in the ventral tegmental area (VTA) signal the discrepancy between expected and actual rewards (that is, reward prediction error)1–3, but how they compute such signals is unknown. We recorded the activity of VTA neurons while mice associated different odour cues with appetitive and aversive outcomes. We found three types of neuron based on responses to odours and outcomes: approximately half of the neurons (type I, 52%) showed phasic excitation after reward-predicting odours and rewards in a manner consistent with reward prediction error coding; the other half of neurons showed persistent activity during the delay between odour and outcome that was modulated positively (type II, 31%) or negatively (type III, 18%) by the value of outcomes. Whereas the activity of type I neurons was sensitive to actual outcomes (that is, when the reward was delivered as expected compared to when it was unexpectedly omitted), the activity of type II and type III neurons was determined predominantly by reward-predicting odours. We ‘tagged’ dopaminergic and GABAergic neurons with the light-sensitive protein channelrhodopsin-2 and identified them based on their responses to optical stimulation while recording. All identified dopaminergic neurons were of type I and all GABAergic neurons were of type II. These results show that VTA GABAergic neurons signal expected reward, a key variable for dopaminergic neurons to calculate reward prediction error.Molecular and Cellular Biolog

Spontaneous rapid odor source localization behavior requires interhemispheric communication

Navigation, finding food sources and avoiding danger critically depend on the identification and spatial localization of airborne chemicals. When monitoring the olfactory environment, rodents spontaneously engage in active olfactory sampling behavior, also referred to as exploratory sniffing [1]. Exploratory sniffing is characterized by stereotypical high frequency respiration, which is also reliably evoked by novel odorant stimuli [2,3]. To study novelty-induced exploratory sniffing, we developed a novel, non-contact method for measuring respiration by infrared (IR) thermography in a behavioral paradigm, in which novel and familiar stimuli are presented to head-restrained mice. We validated the method by simultaneously performing nasal pressure measurements, a commonly used invasive approach [2,4], and confirmed highly reliable detection of inhalation onsets. We further discovered that mice actively orient their nostrils towards novel, previously unexperienced, smells. In line with the remarkable speed of olfactory processing reported previously [3,5,6], we find that mice initiate their response already within the first sniff after odor onset. Moreover, transecting the anterior commissure (AC) disrupted orienting, indicating the orienting response requires interhemispheric transfer of information. This suggests, mice compare odorant information obtained from the two bilaterally symmetric nostrils to locate the source of the novel odorant. We further demonstrate that asymmetric activation of the AON is both necessary and sufficient for eliciting orienting responses. These findings support the view that the AON plays an important role in the internostril difference comparison underlying rapid odor source localization.publisher: Elsevier articletitle: Spontaneous Rapid Odor Source Localization Behavior Requires Interhemispheric Communication journaltitle: Current Biology articlelink: http://dx.doi.org/10.1016/j.cub.2017.04.027 content_type: article copyright: © 2017 The Authors. Published by Elsevier Ltd.status: publishe

Cue-Evoked Dopamine Promotes Conditioned Responding during Learning

Dopamine neurons mediate the association of conditioned stimuli (CS) with reward (unconditioned stimuli, US) by signaling the discrepancy between predicted and actual reward during the US. Some theoretical models suggest that learning is also influenced by the salience or associability of the CS. A hallmark of CS associability models is that they can explain latent inhibition, i.e., the observation that novel CS are more effectively learned than familiar CS. Novel CS are known to activate dopamine neurons, but whether those responses affect associative learning has not been investigated. Here, we used fiber photometry to characterize dopamine responses to inconsequential familiar and novel stimuli. Using bidirectional optogenetic modulation during conditioning, we then show that CS-evoked dopamine promotes conditioned responses. This suggests that Pavlovian conditioning is influenced by CS dopamine, in addition to US reward prediction errors. Accordingly, the absence of dopamine responses to familiar CS might explain their slower learning in latent inhibition.status: publishe

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 which 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 due to 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.status: publishe