Olivier Collignon

Audio-visual integration of emotion expression.

Regardless of the fact that emotions are usually recognized by combining facial and vocal expressions, the multisensory nature of affect perception has scarcely been investigated. In the present study, we show results of three experiments on multisensory perception of emotions using newly validated sets of dynamic visual and non-linguistic vocal clips of affect expressions. In Experiment 1, participants were required to categorize fear and disgust expressions displayed auditorily, visually, or using congruent or incongruent audio-visual stimuli. Results showed faster and more accurate categorisation in the bimodal congruent situation than in the unimodal conditions. In the incongruent situation, participant preferentially categorized the affective expression based on the visual modality, demonstrating a visual dominance in emotional processing. However, when the reliability of the visual stimuli was diminished, participants categorized incongruent bimodal stimuli preferentially via the auditory modality. These results demonstrate that visual dominance in affect perception does not occur in a rigid manner, but follows flexible situation-dependent rules. In Experiment 2, we requested the participants to pay attention to only one sensory modality at a time in order to test the putative mandatory nature of multisensory affective interactions. We observed that even if they were asked to ignore concurrent sensory information, the irrelevant information significantly affected the processing of the target. This observation was especially true when the target modality was less reliable. Altogether, these findings indicate that the perception of emotion expressions is a robust multisensory situation which follows rules that have been previously observed in other perceptual domains.

Cross-modal plasticity for the spatial processing of sounds in visually deprived subjects

Until only a few decades ago, researchers still considered sensory cortices to be fixed or “hardwired,” with specific cortical regions solely dedicated to the processing of selective sensory inputs. But recent evidences have shown that the brain can rewire itself, showing an impressive range of cross-modal plasticity. Visual deprivation is one of the rare human models that allow us to explore the role of experience-dependent plasticity of a sensory cortex deprived of its natural inputs. The objective of this paper is to describe recent results regarding the spatial processing of sounds in blind subjects. These studies suggest that blind individuals may demonstrate exceptional abilities in auditory spatial processing and that such enhanced performances may be intrinsically linked to the recruitment of occipital areas deprived of their normal visual inputs. Such results highlight the brain’s remarkable ability to rewire its components to compensate for the challenging neurological condition that is visual deprivation. Moreover, we shall discuss that such cross-modal recruitment may, to some extent, follow organizational principles similar to the functional topography of the region observed in the sighted. Even if such recruitment is especially present in individuals having lost their sight in early infancy, occipital regions also show impressive plastic properties when vision is lost at a later age. This observation will be related to recent results demonstrating that occipital regions play a more important role than previously expected in the spatial processing of sounds, even in sighted subjects. Putative physiological mechanisms underlying such cross-modal recruitment will then be discussed. All these results have important implications for understanding the role of visual experience in shaping the development of occipital regions and may guide the implementation of rehabilitative methods such as sensory substitution or neural implants.

Functional specialization for auditory–spatial processing in the occipital cortex of congenitally blind humans

The study of the congenitally blind (CB) represents a unique opportunity to explore experience-dependant plasticity in a sensory region deprived of its natural inputs since birth. Although several studies have shown occipital regions of CB to be involved in nonvisual processing, whether the functional organization of the visual cortex observed in sighted individuals (SI) is maintained in the rewired occipital regions of the blind has only been recently investigated. In the present functional MRI study, we compared the brain activity of CB and SI processing either the spatial or the pitch properties of sounds carrying information in both domains (i.e., the same sounds were used in both tasks), using an adaptive procedure specifically designed to adjust for performance level. In addition to showing a substantial recruitment of the occipital cortex for sound processing in CB, we also demonstrate that auditory–spatial processing mainly recruits the right cuneus and the right middle occipital gyrus, two regions of the dorsal occipital stream known to be involved in visuospatial/motion processing in SI. Moreover, functional connectivity analyses revealed that these reorganized occipital regions are part of an extensive brain network including regions known to underlie audiovisual spatial abilities (i.e., intraparietal sulcus, superior frontal gyrus). We conclude that some regions of the right dorsal occipital stream do not require visual experience to develop a specialization for the processing of spatial information and to be functionally integrated in a preexisting brain network dedicated to this ability.

Auditory motion perception activates visual motion areas in early blind subjects.

We have previously shown that some visual motion areas can be specifically recruited by auditory motion processing in blindfolded sighted subjects [Poirier, C., Collignon, O., De Volder, A.G., Renier, L., Vanlierde, A., Tranduy, D., Scheiber, C., 2005. Specific activation of V5 brain area by auditory motion processing: an fMRI study. Brain Res. Cogn. Brain Res. 25, 650-658]. The present fMRI study investigated whether auditory motion processing may recruit the same brain areas in early blind subjects. The task consisted of simultaneously determining both the nature of a sound stimulus (pure tone or complex sound) and the presence or absence of its movement. When a movement was present, blind subjects had to identify its direction. Auditory motion processing, as compared to static sound processing, activated the brain network of auditory and visual motion processing classically observed in sighted subjects. Accordingly, brain areas previously considered as specific to visual motion processing could be specifically recruited in blind people by motion stimuli presented through the auditory modality. This indicates that the occipital cortex of blind people could be organized in a modular way, as in sighted people. The similarity of these results with those we previously observed in sighted subjects suggests that occipital recruitment in blind people could be mediated by the same anatomical connections as in sighted subjects.

Women process multisensory emotion expressions more efficiently than men

Despite claims in the popular press, experiments investigating whether female are more efficient than male observers at processing expression of emotions produced inconsistent findings. In the present study, participants were asked to categorize fear and disgust expressions displayed auditorily, visually, or audio-visually. Results revealed an advantage of women in all the conditions of stimulus presentation. We also observed more nonlinear probabilistic summation in the bimodal conditions in female than male observers, indicating greater neural integration of different sensory-emotional informations. These findings indicate robust differences between genders in the multisensory perception of emotion expression.

Impact of blindness onset on the functional organization and the connectivity of the occipital cortex

Contrasting the impact of congenital versus late-onset acquired blindness provides a unique model to probe how experience at different developmental periods shapes the functional organization of the occipital cortex. We used functional magnetic resonance imaging to characterize brain activations of congenitally blind, late-onset blind and two groups of sighted control individuals while they processed either the pitch or the spatial attributes of sounds. Whereas both blind groups recruited occipital regions for sound processing, activity in bilateral cuneus was only apparent in the congenitally blind, highlighting the existence of region-specific critical periods for crossmodal plasticity. Most importantly, the preferential activation of the right dorsal stream (middle occipital gyrus and cuneus) for the spatial processing of sounds was only observed in the congenitally blind. This demonstrates that vision has to be lost during an early sensitive period in order to transfer its functional specialization for space processing toward a non-visual modality. We then used a combination of dynamic causal modelling with Bayesian model selection to demonstrate that auditory-driven activity in primary visual cortex is better explained by direct connections with primary auditory cortex in the congenitally blind whereas it relies more on feedback inputs from parietal regions in the late-onset blind group. Taken together, these results demonstrate the crucial role of the developmental period of visual deprivation in (re)shaping the functional architecture and the connectivity of the occipital cortex. Such findings are clinically important now that a growing number of medical interventions may restore vision after a period of visual deprivation.

Improved selective and divided spatial attention in early blind subjects

Spatial attention paradigms using auditory or tactile stimulation were used to explore neural and behavioral reorganization in early blind subjects. Although it is commonly assumed that blind subjects outperform sighted subjects in such tasks, the empirical data to confirm this remain controversial. Moreover, previous studies have often confounded factors of sensory acuity with those of attention. In the present work, we compared the performance of individually matched early blind and sighted subjects during auditory and tactile tasks. These consisted of sensory acuity tests, simple reaction time task as well as selective and divided spatial attention tasks. Based on sensory measurements, we made sure that the reliability and salience of auditory and tactile information were identical between the two populations to estimate attentional performance independently of sensory influence. Results showed no difference between groups in either sensory sensitivity or simple reaction time task for both modalities. However, blind subjects displayed shorter reaction times than sighted subjects in both tactile and auditory selective spatial attention tasks and also in bimodal divided spatial attention tasks. The present study thus demonstrates an enhanced attentional performance in early blind subjects which is independent of sensory influence. These supra-normal abilities could be related to quantitative and qualitative changes in the way early visually deprived subjects process non-visual spatial information.

Cross-modal activation of visual cortex during depth perception using auditory substitution of vision

Previous neuroimaging studies identified multimodal brain areas in the visual cortex that are specialized for processing specific information, such as visual-haptic object recognition. Here, we test whether visual brain areas are involved in depth perception when auditory substitution of vision is used. Nine sighted volunteers were trained blindfolded to use a prosthesis substituting vision with audition both to recognize two-dimensional figures and to estimate distance of an object in a real three-dimensional environment. Using positron emission tomography, regional cerebral blood flow was assessed while the prosthesis was used to explore virtual 3D images; subjects focused either on 2D features (target search) or on depth (target distance comparison). Activation foci were found in visual association areas during both the target search task, which recruited the occipito-parietal cortex, and the depth perception task, which recruited occipito-parietal and occipito-temporal areas. This indicates that some brain areas of the visual cortex are relatively multimodal and may be recruited for depth processing via a sense other than vision.

Neuron-Specific Enolase as a Predictor of Death or Poor Neurological Outcome After Out-of-Hospital Cardiac Arrest and Targeted Temperature Management at 33°C and 36°C

BACKGROUND Neuron-specific enolase (NSE) is a widely-used biomarker for prognostication of neurological outcome after cardiac arrest, but the relevance of recommended cutoff values has been questioned due to the lack of a standardized methodology and uncertainties over the influence of temperature management. OBJECTIVES This study investigated the role of NSE as a prognostic marker of outcome after out-of-hospital cardiac arrest (OHCA) in a contemporary setting. METHODS A total of 686 patients hospitalized after OHCA were randomized to targeted temperature management at either 33°C or 36°C. NSE levels were assessed in blood samples obtained 24, 48, and 72 h after return of spontaneous circulation. The primary outcome was neurological outcome at 6 months using the cerebral performance category score. RESULTS NSE was a robust predictor of neurological outcome in a baseline variable-adjusted model, and target temperature did not significantly affect NSE values. Median NSE values were 18 ng/ml versus 35 ng/ml, 15 ng/ml versus 61 ng/ml, and 12 ng/ml versus 54 ng/ml for good versus poor outcome at 24, 48, and 72 h, respectively (p < 0.001). At 48 and 72 h, NSE predicted neurological outcome with areas under the receiver-operating curve of 0.85 and 0.86, respectively. High NSE cutoff values with false positive rates ≤5% and tight 95% confidence intervals were able to reliably predict outcome. CONCLUSIONS High, serial NSE values are strong predictors of poor outcome after OHCA. Targeted temperature management at 33°C or 36°C does not significantly affect NSE levels. (Target Temperature Management After Cardiac Arrest [TTM]; NCT01020916).

A panel of 4 microRNAs facilitates the prediction of left ventricular contractility after acute myocardial infarction.

Background Prediction of clinical outcome after acute myocardial infarction (AMI) is challenging and would benefit from new biomarkers. We investigated the prognostic value of 4 circulating microRNAs (miRNAs) after AMI. Methods We enrolled 150 patients after AMI. Blood samples were obtained at discharge for determination of N-terminal pro-brain natriuretic peptide (Nt-proBNP) and levels of miR-16, miR-27a, miR-101 and miR-150. Patients were assessed by echocardiography at 6 months follow-up and the wall motion index score (WMIS) was used as an indicator of left ventricular (LV) contractility. We assessed the added predictive value of miRNAs against a multi-parameter clinical model including Nt-proBNP. Results Patients with anterior AMI and elevated Nt-proBNP levels at discharge from the hospital were at high risk of subsequent impaired LV contractility (follow-up WMIS>1.2, n = 71). A combination of the 4 miRNAs (miR-16/27a/101/150) improved the prediction of LV contractility based on clinical variables (P = 0.005). Patients with low levels of miR-150 (odds ratio [95% confidence interval] 0.08 [0.01–0.48]) or miR-101 (0.19 [0.04–0.97]) and elevated levels of miR-16 (15.9 [2.63–95.91]) or miR-27a (4.18 [1.36–12.83]) were at high risk of impaired LV contractility. The 4 miRNA panel reclassified a significant proportion of patients with a net reclassification improvement of 66% (P = 0.00005) and an integrated discrimination improvement of 0.08 (P = 0.001). Conclusion Our results indicate that panels of miRNAs may aid in prognostication of outcome after AMI.