Moutoussis, K., A. Maier, S. Zeki and N. K. Logothetis: Seeing invisible motion: responses of area V5 neurons in the awake-behaving macaque. Soc. for Neurosci. Abstr. 390.11, 1.

Understanding how activity in the brain leads to a subjective percept is of great interest to philosophers and neuroscientists alike. In the last years, neurophysiological experiments have approached this problem directly by measuring neural signals in animals as they experience well-defined visual percepts. Stimuli in these studies are often inherently ambiguous, and thus rely upon the subjective report, generally from trained monkeys, to provide a measure of perception. By correlating activity levels in the brain to this report, one can speculate (...) on the role of individual neurons and groups of neurons in the formation and maintenance of a particular percept. However, in order to draw valid conclusions from such experiments, it is critical that the responses accurately and reliably reflect what is perceived. For this reason, a number of behavioural paradigms have been developed to control and evaluate the truthfulness of responses from behaving animals. Here we describe several approaches to optimizing the reliability of a monkey's perceptual report, and argue that their combination provides an invaluable approach in the study of subjective visual perception. (shrink)

Background: Continuous viewing of ambiguous patterns is characterized by wavering perception that alternates between two or more equally valid visual solutions. However, when such patterns are viewed intermittently, either by repetitive presentation or by periodic closing of the eyes, perception can become locked or "frozen" in one configuration for several minutes at a time. One aspect of this stabilization is the possible existence of a perceptual memory that persists during periods in which the ambiguous stimulus is absent. Here, we use (...) a novel paradgim of temporally interleaved ambiguous stimuli to explore the nature of this memory, with particular regard to its potential impact on perceptual organization. Results: We found that the persistence of a perceptual configuration was robust to interposed visual patterns and, further, that at least three ambiguous patterns, when interleaved in time, could undergo parallel, stable time courses. Then, using an interleaved presentation paradigm, we established that the occasional reversal in one pattern could be coupled with that of its interleaved counterpart, and that this coupling was a function of the structural similarity between the patterns. Conclusions: We postulate that the stabilization observed with repetitive presentation of ambiguous patterns can be at least partially accounted for by processes that retain a recent perceptual interpretation, and we speculate that such memory may be important in natural vision. We further propose tha the interleaved paradigm introduced here may be of great value to gauge aspects of stimulus similarity that appeal to particular mechanisms of perceptual organization. (shrink)

Contour adaptation is a recently described paradigm that renders otherwise salient visual stimuli temporarily perceptually invisible. Here we investigate whether this illusion can be exploited to study visual awareness. We found that CA can induce seconds of sustained invisibility following similarly long periods of uninterrupted adaptation. Furthermore, even fragmented adaptors are capable of producing CA, with the strength of CA increasing monotonically as the adaptors encompass a greater fraction of the stimulus outline. However, different types of adaptor patterns, such as (...) distinctive shapes or illusory contours, produce equivalent levels of CA suggesting that the main determinants of CA are low-level stimulus characteristics, with minimal modulation by higher-order visual processes. Taken together, our results indicate that CA has desirable properties for studying visual awareness, including the production of prolonged periods of perceptual dissociation from stimulation as well as parametric dependencies of that dissociation on a host of stimulus parameters. (shrink)

Name der Zeitschrift: Klio Jahrgang: 98 Heft: 2 Seiten: 465-494.

In his playThe Trojan War will not take place(1955), French novelist and diplomat Jean Giraudoux has his protagonist Hector struggle tremendously with convincing both Trojans and Greeks alike to prevent the looming war. Despite coming very close to negotiating a truce, Hector fails in the end owing to the belligerent aspirations of some other protagonists led by the Trojan poet Demokos. Cassandra's famous final line, ‘war cannot be avoided’, comes true and, in contrast to the title of the play, the (...) Trojan War does indeed take place. (shrink)

Correspondence should be addressed to David A. Leopold [email protected] the viewing of certain patterns, widely known as ambiguous or puzzle figures, perception lapses into a sequence of spontaneous alternations, switching every few seconds between two or more visual interpretations of the stimulus. Although their nature and origin remain topics of debate, these stochastic switches are generally thought to be the automatic and inevitable consequence of viewing a pattern without a unique solution. We report here that in humans such perceptual alternations (...) can be slowed, and even brought to a standstill, if the visual stimulus is periodically removed from view. We also show, with a visual illusion, that this stabilizing effect hinges on perceptual disappearance rather than on actual removal of the stimulus. These findings indicate that uninterrupted subjective perception of an ambiguous pattern is required for the initiation of the brain-state changes underlying multistable vision.Visual perception involves coordination between sensory sampling of the world and active interpretation of the sensory data. Human perception of objects and scenes is normally stable and robust, but it falters when one is presented with patterns that are inherently ambiguous or contradictory. Under such conditions, vision lapses into a chain of continually alternating percepts, whereby a viable visual interpretation dominates for a few seconds and is then replaced by a rival interpretation. This multistable vision, or 'multistability', is thought to result from destabilization of fundamental visual mechanisms, and has offered valuable insights into how sensory patterns are actively organized and interpreted in the brain1, 2. Despite a great deal of recent research and interest in multistable perception, however, its neurophysiological underpinnings remain poorly understood. Physiological studies have suggested that disambiguation of ambiguous patterns. (shrink)

BackgroundBiobanking biospecimens and consent are common practice in paediatric research. We need to explore children and young people’s (CYP) knowledge and perspectives around the use of and consent to biobanking. This will ensure meaningful informed consent can be obtained and improve current consent procedures.MethodsWe designed a survey, in co-production with CYP, collecting demographic data, views on biobanking, and consent using three scenarios: 1) prospective consent, 2) deferred consent, and 3) reconsent and assent at age of capacity. The survey was disseminated (...) via the Young Person’s Advisory Group North England (YPAGne) and participating CYP’s secondary schools. Data were analysed using a qualitative thematic approach by three independent reviewers (including CYP) to identify common themes. Data triangulation occurred independently by a fourth reviewer.ResultsOne hundred two CYP completed the survey. Most were between 16–18 years (63.7%, N = 65) and female (66.7%, N = 68). 72.3% had no prior knowledge of biobanking (N = 73).Acceptability of prospective consent for biobanking was high (91.2%, N = 93) with common themes: ‘altruism’, ‘potential benefits outweigh individual risk’, 'frugality', and ‘(in)convenience’.Deferred consent was also deemed acceptable in the large majority (84.3%, N = 86), with common themes: ‘altruism’, ‘body integrity’ and ‘sample frugality’. 76.5% preferred to reconsent when cognitively mature enough to give assent (N = 78), even if parental consent was previously in place. 79.2% wanted to be informed if their biobanked biospecimen is reused (N = 80).ConclusionProspective and deferred consent acceptability for biobanking is high among CYP in the UK. Altruism, frugality, body integrity, and privacy are the most important themes. Clear communication and justification are paramount to obtain consent. Any CYP with capacity should be part of the consenting procedure, if possible. (shrink)

ZusammenfassungMit den Fortschritten im Bereich der psychiatrisch-genetischen Forschung gehen auch intensive Diskussionen bezüglich der daraus erwachsenden Implikationen einher. Hoffnungen wie Befürchtungen gegenüber der neuen Technologie und deren Folgen werden gleichermaßen zum Ausdruck gebracht. Über die Einstellung der Bevölkerung und insbesondere der Patienten mit affektiven oder schizophrenen Erkrankungen und ihrer Angehörigen in Deutschland war bisher allerdings wenig bekannt. Daher führten wir im Rahmen des Deutschen Humangenomprojektes erstmals eine Studie durch, um die Einstellungen und ihre beeinflussenden Faktoren zu erfassen. Wir entwickelten einen (...) Fragebogen zur Erfassung der Erwartungen, Hoffnungen und Befürchtungen sowie der die Einstellung beeinflussenden Faktoren. Hiermit wurde eine repräsentative Stichprobe von 3077 Personen aus der Allgemeinbevölkerung am Telefon befragt. Weiterhin wurden mit 316 Patienten und 163 Angehörigen persönliche standardisierte Interviews anhand des Fragebogens durchgeführt. Die Mehrzahl der Befragten hatte eine positive Einstellung zu psychiatrisch-genetischer Forschung, äußerte jedoch gleichzeitig ethische Bedenken. Übereinstimmend waren die Befragten der Ansicht, dass Informationen aus genetischen Untersuchungen vertraulich behandelt werden sollten. Kleine, aber signifikante Unterschiede zwischen den Gruppen zeigten sich bezüglich der Einstellung zu präsymptomatischer genetischer Diagnostik. Unsere Ergebnisse weisen auf eine Ambivalenz der Befragten gegenüber der psychiatrisch-genetischen Forschung und Untersuchung hin: Neben einer überwiegend positiven Einstellung wurden auch moralische Bedenken geäußert. (shrink)

Although activated spinal cord glia contribute importantly to neuropathic pain, how nerve injury activates glia remains controversial. It has recently been proposed, on the basis of genetic approaches, that toll-like receptor 4 may be a key receptor for initiating microglial activation following L5 spinal nerve injury. The present studies extend this idea pharmacologically by showing that TLR4 is key for maintaining neuropathic pain following sciatic nerve chronic constriction injury. Established neuropathic pain was reversed by intrathecally delivered TLR4 receptor antagonists derived (...) from lipopolysaccharide. Additionally, -naltrexone, -naloxone, and -naloxone, which we show here to be TLR4 antagonists in vitro on both stably transfected HEK293-TLR4 and microglial cell lines, suppressed neuropathic pain with complete reversal upon chronic infusion. Immunohistochemical analyses of spinal cords following chronic infusion revealed suppression of CCI-induced microglial activation by -naloxone and -naloxone, paralleling reversal of neuropathic pain. Together, these CCI data support the conclusion that neuron-to-glia signaling through TLR4 is important not only for initiating neuropathic pain, as suggested previously, but also for maintaining established neuropathic pain. Furthermore, these studies suggest that the novel TLR4 antagonists -naloxone and -naloxone can each fully reverse established neuropathic pain upon multi-day administration. This finding with -naloxone is of potential clinical relevance. This is because -naloxone is an antagonist that is inactive at the -opioid selective receptors on neurons that produce analgesia. Thus, these data suggest that -opioid antagonists such as -naloxone may be useful clinically to suppress glial activation, yet -opioid agonists suppress pain. (shrink)

We propose an empirical mode decomposition (EMD-) based method to extract features from the multichannel recordings of local field potential (LFP), collected from the middle temporal (MT) visual cortex in a macaque monkey, for decoding its bistable structure-from-motion (SFM) perception. The feature extraction approach consists of three stages. First, we employ EMD to decompose nonstationary single-trial time series into narrowband components called intrinsic mode functions (IMFs) with time scales dependent on the data. Second, we adopt unsupervised K-means clustering to group (...) the IMFs and residues into several clusters across all trials and channels. Third, we use the supervised common spatial patterns (CSP) approach to design spatial filters for the clustered spatiotemporal signals. We exploit the support vector machine (SVM) classifier on the extracted features to decode the reported perception on a single-trial basis. We demonstrate that the CSP feature of the cluster in the gamma frequency band outperforms the features in other frequency bands and leads to the best decoding performance. We also show that the EMD-based feature extraction can be useful for evoked potential estimation. Our proposed feature extraction approach may have potential for many applications involving nonstationary multivariable time series such as brain-computer interfaces (BCI). (shrink)

The communication of de se attitudes poses a problem for “participant- neutral” analyses of communication in terms of propositions expressed or proposed updates to the common ground: when you tell me “I am an idiot”, you express a first person de se attitude, but as a result I form a different, second person attitude, viz. that you are an idiot. I argue that when we take seriously the asymmetry between speaker and hearer in semantics this problem disappears. To prove this (...) I propose a concrete model of communication as the transmission of information from the speaker’s mental state to the hearer’s. My analysis is couched in Discourse Representation Theory, a formal semantic framework that linguists use for modeling conversational common ground updates, but that can also be applied to describe the individual speech participants’ dynamically changing mental states. (shrink)

Lying and fiction both involve the deliberate production of statements that fail to obey Grice’s first Maxim of Quality (“do not say what you believe to be false”). The question thus arises if we can provide a uniform analysis for fiction and lies. In this chapter I discuss the similarities, but also some fundamental differences between lying and fiction. I argue that there’s little hope for a satisfying account within a traditional truth conditional semantic framework. Rather than immediately moving to (...) a fully pragmatic analysis involving distinct speech acts of fiction-making and lying, I will first explore how far we get with the assumption that both are simply assertions, analyzed in a Stalnakerian framework, i.e. as proposals to update the common ground. (shrink)

There are two Habsburg empires in our minds: One – that of Stefan Zweig and Joseph Roth – evokes melancholy and a sense of loss, a yearning not for simpler but perhaps more colourful, less exacting...

l. Die logische Theorie des Urteils bei Aristoteles. Berichtigte Neuausg., mit einem Anhang: Die Echtheit der aristotelischen Hermeneutik -- II. Logische theorie des syllogismus und die entstehung der aristotelischen logik: 1. hälfte. Formenlehre und technik des syllogismus. 2. hälfte. Entstehung der aristotelischen logik.

I show how, contrary to recent claims, so-called embedded imperatives are better analyzed in terms of mixed quotation. To this end I extend the presuppositional analysis of mixed quotation to include quotations of constructions.

We propose to analyze well-known cases of "imaginative resistance" from the philosophical literature (Gendler, Walton, Weatherson) as involving the inference that particular content should be attributed to either: (i) a character rather than the narrator or, (ii) an unreliable, irrational, opinionated, and/or morally deviant "first person" narrator who was originally perceived to be a typical impersonal, omniscient, "effaced" narrator. We model the latter type of attribution in terms of two independently motivated linguistic mechanisms: accommodation of a discourse referent (Lewis, Stalnaker, (...) Kamp) and 'cautious' updating as a model of non-cooperative information exchange (Eckardt). (shrink)

Introduction : last stands -- The world is weary of the past -- Reconstruction on a world scale -- The human zoo -- States of exception, exceptional states -- Postscript : toward Leviathan 3.0?