L’impianto cocleare come potenziatore cognitivo? Una prospettiva neuroetica sulle obiezioni della comunità sorda

Riassunto: L’impianto cocleare (IC) è una neuroprotesi che consente un recupero parziale dell’udito nella persona sorda. Nonostante la sua generale efficacia nel contrastare alcuni dei problemi legati alla sordità, il suo utilizzo è stato fortemente osteggiato da quella parte della comunità sorda che vede nella sordità una forma di identità culturale e non una patologia. Questo articolo inquadra in una prospettiva neuroetica le preoccupazioni della comunità sorda – difficilmente comprensibili agli udenti – esaminando le analogie fra il rifiuto dell’IC e il disagio che si osserva nella popolazione generale relativamente al Potenziamento Cognitivo (PCog). Nel PCog, individui sani insoddisfatti delle proprie prestazioni, o comunque desiderosi di migliorarle, ricorrono ad interventi artificiali per potenziare le proprie funzioni cognitive. L’analisi evidenzia come, nel rifiutare l’IC, la comunità sorda possa voler tutelare un insieme di valori non così diverso da quello che la comunità generale richiama spesso nelle sue preoccupazioni rispetto alla diffusione dei PCog.Parole chiave: Impianto cocleare; Potenziamento cognitivo; Sordità; Cultura sordaThe cochlear implant as cognitive enhancement? A neuroethical perspective on some issues raised by the deaf community Abstract: The cochlear implant (CI) is a neuroprosthesis that allows for partial recovery of auditory function in individuals who are deaf. Despite its general efficacy, its use has been strongly opposed by a part of the deaf community that perceives deafness as a form of cultural identity, rather than a pathology. This article considers the concerns of the deaf community – which are often difficult for hearing people to understand – from a neuroethics perspective, proposing that such opposition to CI is analogous to the general population’s unease with regard to Cognitive Enhancement (CE). CE allows healthy individuals who are unsatisfied with – or would like to improve – their performance to use artificial interventions that enhance cognitive functions. The analysis reveals that, when opposing CIs, the deaf community may be protecting a set of values similar to those that the general community often evokes when voicing concerns about CE diffusion.Keywords: Cochlear Implant; Cognitive Enhancement; Deafness; Deaf Cultur

Losing One's Hand: Visual-Proprioceptive Conflict Affects Touch Perception

BACKGROUND: While the sense of bodily ownership has now been widely investigated through the rubber hand illusion (RHI), very little is known about the sense of disownership. It has been hypothesized that the RHI also affects the ownership feelings towards the participant's own hand, as if the rubber hand replaced the participant's actual hand. Somatosensory changes observed in the participants' hand while experiencing the RHI have been taken as evidence for disownership of their real hand. Here we propose a theoretical framework to disambiguate whether such somatosensory changes are to be ascribed to the disownership of the real hand or rather to the anomalous visuo-proprioceptive conflict experienced by the participant during the RHI. METHODOLOGY/PRINCIPAL FINDINGS: In experiment 1, reaction times (RTs) to tactile stimuli delivered to the participants' hand slowed down following the establishment of the RHI. In experiment 2, the misalignment of visual and proprioceptive inputs was obtained via prismatic displacement, a situation in which ownership of the seen hand was doubtless. This condition slowed down the participants' tactile RTs. Thus, similar effects on touch perception emerged following RHI and prismatic displacement. Both manipulations also induced a proprioceptive drift, toward the fake hand in the first experiment and toward the visual position of the participants' hand in the second experiment. CONCLUSIONS/SIGNIFICANCE: These findings reveal that somatosensory alterations in the experimental hand resulting from the RHI result from cross-modal mismatch between the seen and felt position of the hand. As such, they are not necessarily a signature of disownership

Tactile stimuli at the fingers coding is modulated by hand posture

Introduzione. In due esperimenti abbiamo esaminato l’importanza relativa dei sistemi di riferimento (mano-, corpo- o spazio-specifico) per la codifica di stimoli tattili alle mani usando un paradigma di mascheramento tattile. Metodo. 12 soggetti hanno preso parte all’Esp. 1 (età media 29 anni, 3 femmine) e 12 soggetti hanno preso parte all’Esp. 2 (età media 27 anni, 5 femmine). In entrambi gli esperimenti, il soggetto eseguiva un compito di detezione di un bersaglio vibrotattile, presentato per 5 ms al dito indice o medio di una delle due mani. Il dito bersaglio era specificato dallo sperimentatore all’inizio di ciascun blocco (es., indice destro). Il bersaglio poteva comparire da solo o contemporaneamente ad un distrattore sulla stessa mano (es., medio destro) o sulla mano opposta (al dito omologo o non-omologo rispetto al dito bersaglio; es., indice sinistro o medio sinistro). Inoltre erano previsti catch trial nei quali comparivano i soli distrattori. Nell’Esp.1 entrambe le mani erano in posizione prona; nell’Esp.2 una delle due mani veniva ruotata in posizione supina in metà delle prove. Le variabili dipendenti erano i tempi di reazione e la sensitività (d’). Risultati. Nelle prove in cui il bersaglio era presentato assieme ad un distrattore è emerso un generale effetto di mascheramento. Tuttavia, nell’Esp.1, l’effetto di mascheramento era presente in misura simile per distrattori alla mano contenente il bersaglio (mascheramento intra-mano), o distrattori al dito non-omologo dell’altra mano (mascheramento inter-mano). L’Esp.2 replicava questo risultato quando le mani erano entrambe in posizione prona. Tuttavia, quando una delle due mani era in posizione supina, l’unica condizione interferente rimaneva quella intra-mano. Conclusioni. Questo risultato dimostra che la codifica spaziale di uno stimolo tattile alle dita varia in funzione di quanto le informazioni posturali richiedono un aggiornamento della posizione spaziale dello stimolo tattile

Tactile masking within and between hands: Insights for spatial coding of touch at the fingers

A tactile stimulus at the fingers can be encoded according to multiple reference frames (hand-, body- or space-specific). We examined the relative importance of these reference frames by adapting a tactile masking paradigm for stimuli at the index or middle fingers of either hand (unseen). In Exp.1, participants performed a go-no-go task to detect a vibrotactile target at a pre-specified finger (e.g., right index), when this was presented alone or with a concurrent distractor either on the same hand (right middle finger), or on the opposite hand (at homologous or non-homologous locations with respect to the target finger; e.g., left index or left middle finger, respectively). Tactile masking emerged under double stimulation, both for a distractor within the target-hand and for distractors at the non-homologous location on the opposite hand. This suggests use of hand-specific (than body- or space-specific) reference frames when solving this task. In Exp.2, one hand rotated by 180° around the wrist in half of the trials. Masking effects changed only between-hands. Intriguingly, masking from the non-homologous finger reduced only when the hand that changed posture contained the target. This suggests that spatial coding for touches at the fingers depend upon the behavioural relevance of tactile stimuli

Multiple spatial representations of touch: an MEG investigation

An increasing amount of evidence in animals, as well as behavioural and neuroimaging studies in humans has documented the involvement of primary somatosensory cortices in coding the tactile stimuli coming from the two sides of the body. Using fMRI adaptation, we have shown in a previous experiment that the primary somatosensory cortex can homotopically integrate somatosensory inputs from the two sides of the body, despite its prominent contralateral response. However, the low temporal resolution of fMRI does not allow determining the time course of the interaction between contralateral and ipsilateral hemispheres. The aim of the present study, using magnetoencephalography together with an adaptation paradigm, is to track the tactile information flow across the two hemisphere in the primary (SI) and secondary (SII) somatosensory cortices. We measured the relative changes in neuromagnetic responses evoked by the test stimulus (i.e., always the left index finger) alone and the test stimulus presented together with a conditioning stimulus simultaneously, 25 ms or 125 ms before the test stimulus, respectively. The rational for this manipulation was to explore how the neuromagnetic activity of the test stimulus can be modulated by the conditioning stimulus delivered to different body parts (i.e., same or different fingers within and between the hands) with different timing, compared to the test stimulus presented alone. Results showed the presence of an adaptation effect selective for the stimulation onset asynchrony (25 ms). Moreover, the effect was selective for the pairs of fingers stimulated (i.e., homologous vs non-homologous) and for the side of stimulation (unilateral vs bilateral). Finally, the left index finger (test) showed a special response characteristic in the tested brain areas that differ from all the other fingers. We can conclude that tactile stimuli on the fingers are integrated, at an early stage in the somatosensory cortices following different neural pathways

Bilateral representations of touch in the primary somatosensory cortex

According to current textbook knowledge, primary somatosensory cortex (SI) supports unilateral tactile representations, whereas structures beyond SI, in particular the secondary somatosensory cortices (SII), support bilateral tactile representations. However, dexterous and well-coordinated bimanual motor tasks require early integration of bilateral tactile information. Sequential processing, first of unilateral and subsequently of bilateral sensory information might not be sufficient to accomplish these tasks. This view of sequential processing in the somatosensory system might therefore be questioned, at least for demanding bimanual tasks. Evidence from the last fifteen years is forcing a revision of this textbook notion. Studies in animals and humans indicate that SI is more than a simple relay for unilateral sensory information and, together with SII, contributes to the integration of somatosensory inputs from both sides of the body. Here, we review a series of recent works from our own and other laboratories in favour of interactions between tactile stimuli on the two sides of the body at early stages of processing. We will focus on tactile processing, although a similar logic may also apply to other aspects of somatosensation. We begin by describing the basic anatomy and physiology of interhemispheric transfer, drawing on neurophysiological studies in animals and behavioural studies in humans that showed tactile interactions between body sides, both in healthy and brain-damaged individuals. Then we describe the neural substrates of bilateral interactions in somatosensation as revealed by neurophysiological work in animals and neuroimaging studies in humans (i.e., functional magnetic resonance imaging, magnetoencephalography, and transcranial magnetic stimulation). Finally, we conclude with considerations on the dilemma of how efficiently integrating bilateral sensory information at early processing stages can coexist with more lateralised representations of somatosensory input, in the context of motor control

Multiple spatial representation of touch: An fMRI adaptation study

When two repeating stimuli activate the same neuronal population, a decreased overall neural response is observed. This neurophysiological response is detectable by functional magnetic resonance imaging, and has been termed fMRI adaptation. Following this logic, when two tactile events are repeated on exactly the same region of skin, all neurons that have a strictly somatotopic response should reduce their activity. Here we used fMRI adaptation to address the issue of reference frames for touch. In particular, we asked if there exist neuronal populations that adapt to stimulation that repeats over distinct regions of skin when some other aspect of spatial coding of touch is identical (e.g., homologous finger stimulated between the two hands). We examined this question for SI and SII, measuring the blood-oxygen level-dependent (BOLD) effect to touches delivered in sequence within or between hands, to homologous or non-homologous fingers. The results showed stronger adaptation (i.e., a lower BOLD effect) at the level of SI when stimulation repeated over same (i.e., homologous) in comparison to different (i.e., non-homologous) fingers, regardless of whether stimulation occurred within or between hands. This pattern of results is less clear in SII. These results suggest a bilateral representation for touch in human SI, in agreement with neurophysiological data on monkeys

Endothelial overexpression of LOX-1 increases plaque formation and promotes atherosclerosis in vivo

Aims Lectin-like oxLDL receptor-1 (LOX-1) mediates the uptake of oxidized low-density lipoprotein (oxLDL) in endothelial cells and macrophages. However, the different atherogenic potential of LOX-1-mediated endothelial and macrophage oxLDL uptake remains unclear. The present study was designed to investigate the in vivo role of endothelial LOX-1 in atherogenesis. Methods and results Endothelial-specific LOX-1 transgenic mice were generated using the Tie2 promoter (LOX-1TG). Oxidized low-density lipoprotein uptake was enhanced in cultured endothelial cells, but not in macrophages of LOX-1TG mice. Six-week-old male LOX-1TG and wild-type (WT) mice were fed a high-cholesterol diet (HCD) for 30 weeks. Increased reactive oxygen species production, impaired endothelial nitric oxide synthase activity and endothelial dysfunction were observed in LOX-1TG mice as compared with WT littermates. LOX-1 overexpression led to p38 phosphorylation, increased nuclear factor κB activity and subsequent up-regulation of vascular cell adhesion molecule-1, thereby favouring macrophage accumulation and aortic fatty streaks. Consistently, HCD-fed double-mutant LOX-1TG/ApoE−/− displayed oxidative stress and vascular inflammation with higher aortic plaques than ApoE−/− controls. Finally, bone marrow transplantation experiments showed that endothelial LOX-1 was sufficient for atherosclerosis development in vivo. Conclusions Endothelial-specific LOX-1 overexpression enhanced aortic oxLDL levels, thereby favouring endothelial dysfunction, vascular inflammation and plaque formation. Thus, LOX-1 may serve as a novel therapeutic target for atherosclerosi