Impaired sensory processing contributes to deficits in cognitive and psychosocial functioning in individuals with schizophrenia (SZ). Mismatch Negativity (MMN), an event-related potential (ERP) index of sensory discrimination associated with cognitive and psychosocial functioning, is a candidate biomarker of auditory discrimination and thus possibly of changes following auditory-based Targeted Cognitive Training (TCT). Here we evaluated the acute effect of TCT on cortical processes supporting auditory discrimination.MMN was assessed in 28 SZ outpatients before and after a single 1-hour (hr) session of “Sound Sweeps,” a pitch discrimination task that is a component of the TCT suite of exercises. Independent component (IC) analysis was applied to decompose 64-channel scalp-recorded electroencephalogram (EEG) activity into spatiotemporally stationary sources and their activities. ICs from all patients were pooled to find commonalities in their cortical locations. IC cluster-mean ERPs were evaluated to determine the clusters contributing to the (140–200 ms) MMN difference between responses to deviant and standard tone stimuli respectively.Two frontal IC clusters centered in orbitofrontal cortex (OFC) and anterior cingulate cortex (ACC) accounted for >77% of MMN variance across all scalp channels. After 1-hr auditory training, significant suppression of ACC cluster contributions was detected, whereas the OFC cluster contribution was unchanged.Prior to TCT, the MMN response was dominated by EEG effective sources in or near OFC and ACC. However, after 1-hr of auditory-based TCT, a significant attenuation of ACC was observed, whereas OFC contribution to MMN persisted. The present findings support further trials designed to test whether training-related MMN plasticity in the ACC after 1-hr may predict individual patient response to a full course of TCT.

It is well established that multisensory integration is a functional characteristic of the superior colliculus that disambiguates external stimuli and therefore reduces the reaction times toward simple audiovisual targets in space. However, in a condition where a complex audiovisual stimulus is used, such as the optical flow in the presence of modulated audio signals, little is known about the processing of the multisensory integration in the superior colliculus. Furthermore, since visual and auditory deficits constitute hallmark signs during aging, we sought to gain some insight on whether audiovisual processes in the superior colliculus are altered with age. Extracellular single-unit recordings were conducted in the superior colliculus of anesthetized Sprague-Dawley adult (10-12 months) and aged (21-22 months) rats. Looming circular concentric sinusoidal (CCS) gratings were presented alone and in the presence of sinusoidally amplitude modulated white noise. In both groups of rats, two different audiovisual response interactions were encountered in the spatial domain: superadditive, and suppressive. In contrast, additive audiovisual interactions were found only in adult rats. Hence, superior colliculus audiovisual interactions were more numerous in adult rats (38%) than in aged rats (8%). These results suggest that intersensory interactions in the superior colliculus play an essential role in space processing toward audiovisual moving objects during self-motion. Moreover, aging has a deleterious effect on complex audiovisual interactions.

Objective: To verify if a mismatch negativity (MMN) paradigm based on speech syllables can differentiate between good and poorer cochlear implant (CI) users on a speech recognition task.Methods: Twenty adults with a CI and 11 normal hearing adults participated in the study. Based on a speech recognition test, ten CI users were classified as good performers and ten as poor performers. We measured the MMN with /da/ as the standard stimulus and /ba/ and /ga/ as the deviants. Separate analyses were conducted on the amplitude and latency of the MMN.Results: A MMN was evoked by both deviant stimuli in all normal hearing participants and in well performing CI users, with similar amplitudes for both groups. However, the amplitude of the MMN was significantly reduced for the poorer CI users compared to the normal hearing group and the good CI users. The latency was longer for both groups of cochlear implant users. A bivariate correlation showed a significant positive correlation between the speech recognition score and the amplitude of the MMN.Conclusions: The MMN can distinguish between CI users who have good versus poor speech recognition as assessed with conventional tasks.Significance: Our findings suggest that the MMN can be use to assess speech recognition proficiency in CI users who cannot be tested with regular speech recognition tasks, like infants and other non-verbal populations. (C) 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Plasticity resulting from early sensory deprivation has been investigated in both animals and humans. After sensory deprivation, brain areas that are normally associated with the lost sense are recruited to carry out functions in the remaining intact modalities. Previous studies have reported that it is almost exclusively the visual dorsal pathway which is affected by auditory deprivation. The purpose of the current study was to further investigate the possible reorganization of visual ventral stream functions in deaf individuals in both the auditory and the visual cortices. Fifteen pre-lingual profoundly deaf subjects were compared with a group of 16 hearing subjects. We used fMRI (functional magnetic resonance imaging) to explore the areas underlying the processing of two similar visual motion stimuli that however were designed to evoke different types of processing: (1) a global motion stimulus (GMS) which preferentially activates regions of the dorsal visual stream, and (2) a form-from-motion (FFM) stimulus which is known to recruit regions from both visual streams. No significant differences between deaf and hearing individuals were found in target visual and auditory areas when the motion and form components of the stimuli were isolated (contrasted with a static visual image). However, increases in activation were found in the deaf group in the superior temporal gyrus (BA 22 and 42) and in an area located at the junction of the parieto-occipital sulcus and the calcarine fissure (encompassing parts of the cuneus, precuneus and the lingual gyrus) for the GMS and FFM conditions as well as for the static image, relative to a baseline condition absent of any visual stimulation. These results suggest that the observed cross-modal recruitment of auditory areas in deaf individuals does not appear to be specialized for motion processing, but rather is present for both motion and static visual stimuli.

Although the topic of sensory integration has raised increasing interest, the differing behavioral outcome of combining unisensory versus multisensory inputs has surprisingly only been scarcely investigated. In the present experiment, observers were required to respond as fast as possible to (1) lateralized visual or tactile targets presented alone, (2) double stimulation within the same modality or (3) double stimulation across modalities. Each combination was either delivered within the same hemispace (spatially aligned) or in different hemispaces (spatially misaligned). Results show that the redundancy gains (RG) obtained from the cross-modal conditions were far greater than those obtained from combinations of two visual or two tactile targets. Consistently, we observed that the reaction time distributions of cross-modal targets, but not those of within-modal targets, surpass the predicted reaction time distribution based on the summed probability distributions of each constituent stimulus presented alone. Moreover, we found that the spatial alignment of the targets did not influence the RG obtained in cross-modal conditions, whereas within-modal stimuli produced a greater RG when the targets where delivered in separate hemispaces. These results suggest that within-modal and cross-modal integration are not only distinguishable by the amount of facilitation they produce, but also by the spatial configuration under which this facilitation occurs. Our study strongly supports the notion that estimates of the same event that are more independent produce enhanced integrative gains.

Although significant progress has been made over the last decades, the chemical senses remain less well explored than vision or audition. One method to assess participants' ability to identify or localize odors consists in the application of dichotomous stimuli (e.g., left- and right-sided stimulation). In this study we aimed to explore localization and identification mechanisms by investigating whether response times and response accuracy were correlated, with the aim of establishing the pertinence of response times as an additional measure for assessment of the olfactory function (1). We further examined an advantage of the right nostril which has been reported in several publications (2). We delivered two mixed olfactory/trigeminal odors (benzaldehyde and eucalyptol) to one nostril at a time in a pseudorandomized order to 23 normosmic participants; the other nostril received an odor-free air puff. In half of the trials we asked the participants to detect the stimulated nostril; in the other half, they indicated which odor they had received. We recorded response accuracy and response times. Participants reached higher accuracy in odor identification than in localization, driven by benzaldehyde. For the stimulus eucalyptol exclusively, we observed that participants were faster to respond after stimulation of the right nostril than to the left nostril, in the localization task. Finally, response times were correlated with response accuracy in the identification task, but not in localization. Our findings suggest that odor identification is easier than odor localization. In addition, we find further support for an advantage of the right nostril over the left nostril. Moreover, the measurement of reaction times may supplement other techniques of the assessment of odor identification.

Introduction: Most studies investigating visual development have assessed lower (local) and higher (global) levels of processing in isolation. It therefore remains unknown whether immature perception at one level affects processing in the other as a function of development. The objective of the present study was to assess the typical development of low- to mid-level visual processes by evaluating the discrimination of circular shapes (global) differing in local attributes: luminance and texture. Methods: Typically developing school-aged children (n = 11, 7-12 years olds), adolescents (n = 13, 13-17 years old) and adults (n = 13, 18-25 years old) were asked to discriminate a deformed circle (target) from a pure circle in a 2-ATFC using the method of constant stimuli; deformation thresholds were measured. Stimuli consisted of radial frequency patterns: circular contours with a varying number of bumps or deformations (radial frequencies (RFs) of 3, 5, and 10), which establishes the global shape. The amount of deformation is set by the amplitude or size of the bumps (dependent measure), and the patterns are defined by either luminance or texture (local information). Results: A 3-way mixed factorial analysis revealed a Group x Local Attribute interaction, demonstrating that for both luminance and texture patterns, the school-aged group performed significantly worse compared to adolescents and adults. No significant difference between adolescents and adults was identified. A Local Attribute x RF interaction was also demonstrated, with discrimination thresholds for luminance-defined patterns differing significantly across all RFs. Alternatively, for texture-defined patterns, discrimination thresholds did not differ for RFs of 5 and 10. Conclusions: These results suggest that the typical development of low- to mid-level visual processes is only influenced by the type of local attributes (luminance vs texture) and not by the number of RFs defining the contour. Overall, immature low-level visual processes can potentially affect higher-level perception. Meeting abstract presented at VSS 2012

Visual deprivation is associated to crossmodal reorganization, leading to the recruitment of the visual cortex for non-visual processing (Bavelier & Neville, 2002). Because of important advances in visual restoration techniques, a crucial question concerns if, how and at what speed the brain of sight-recovery individuals can re-acquire its function to process visual inputs. We used behavioral measures and functional Magnetic Resonance Imaging (fMRI) to explore the potential neuro-functional modifications taking place in the visual cortex of a low-vision (i.e. legally blind) patient (female, 41) before and after partial vision restoration with Boston keratoprosthesis (Dagher & Dohlman, 2008). Behavioral tasks consisted of computerized tests evaluating visual acuity, contrast sensitivity, face perception and global motion perception. Each fMRI session comprised two runs testing the integrity of a key aspect of the ventral (i.e. face perception) and the dorsal (i.e. motion perception) visual pathways. In order to test for crossmodal reorganization, homologous conditions in the auditory modality were also included (i.e. voices in the ventral run; moving sounds in the dorsal run). The patient was tested 6 days before and 3 days following surgery with identical behavioral and fMRI tasks. In parallel to behavioral improvements, fMRI analyses contrasting differential activations before and after visual restoration revealed massive changes in brain responses. Specifically, we found (1) unspecific activity in the occipital cortex for auditory processing pre-surgery, which was reversed (deactivation) post-surgery; (2) enhanced functional tuning to faces in the right ventral visual pathway (fusiform and occipital "face areas", FFA and OFA) after visual restoration and; (3) reduced responses to motion in V5 bilaterally after visual restoration. These observations provide compelling evidence that the human brain maintains a high degree of plasticity well into adulthood, and that the ventral and dorsal visual pathways might be differently affected by visual deprivation and restoration. Meeting abstract presented at VSS 2012

 Most of the studies that have focused on the development of the visual system in children using visual evoked potentials (VEPs) have used stimuli soliciting only one level of visual processing (Pike & Marlow, 2000; Sheperds et al. 1999).  The perception of a visual scene requires a multitude of analytical processes ranging from the encoding of various characteristics of the visual stimuli, to the processing of top-down information and finally leading to segmentation of forms and recognition of stimuli (Arcand et al. 2007).  Numerous studies have shown that this more complex visual process can be objectively studied with specific VEPs, namely texture segregation visual evoked potentials (tsPEVs) (Bach & Meigen, 1997, 1998; Caputo & Casco, 1999)  Even though it has been demonstrated that texture segregation appears in the first few months of life and that it continues to develop within the first year, it is not known at what age texture segregation processes reach maturity (Arcand et al. 2007).

What distinguishes conscious from non-conscious visual perception? We investigated this question from an information-processing perspective by exploring which spatial frequencies (SFs) are correlated with observers’ responses during conscious vs. non-conscious face perception. Specifically, we used a face-gender repetition priming paradigm and the SF Bubbles technique (Willenbockel et al., 2010) to precisely map the SFs that prime as a function of awareness. A "visible prime" condition was set up by presenting the stimulus sequence mask-blank-prime-blank-mask-target (prime, blank, and mask durations ≤ 50 ms); an "invisible prime" condition was created by reversing the order of the masks and the blanks (see also Dehaene et al., 2001). Twenty grayscale face photographs (10 males; visual angle ~3º) served as primes and as targets, whereby the prime faces were randomly SF filtered trial-by-trial. Results show facilitatory priming effects in response times for both visibility conditions, albeit smaller for the invisible prime condition. A multiple linear regression on the SF filters from each trial and the transformed response times revealed that fast responses were linked to specific SFs (~12 cycles per face width) in the visible prime condition, but not to any specific SFs in the invisible prime condition. Interestingly, the SFs that led to faster responses in the visible prime condition led to slower responses in the invisible prime condition. The results imply that different visual information primes as a function of awareness and therefore provide strong support for a qualitative conscious/non-conscious dichotomy. Meeting abstract presented at VSS 2012

Recent studies demonstrated that auditory processing in the reorganized occipital cortex of congenitally blind (CB) humans maintains some level of specialization that is known to characterize the occipital cortex of sighted individuals. A crucial yet unresolved question concerns the existence of a sensitive period in order for such specific reorganization to occur. Therefore, we investigated the impact of early versus late visual deprivation in shaping the functional properties of the occipital cortex. Using functional magnetic resonance imaging (fMRI), we characterized brain activations of CB and late blind (LB) subjects when they processed either the pitch or the spatial attributes of sounds. Our data demonstrates massive recruitment of occipital regions for auditory processing in both blind groups relative to matched sighted groups, although the extent was less widespread in LB when compared to CB. Intriguingly, some auditory activity in the occipital cortex observed in LB was inversely proportional to blindness duration. We also observed that some regions of the right dorsal stream (lateral occipito-temporal and cuneus) were preferentially activated for the spatial processing of sounds in CB only. This suggests that vision has to be lost during an early sensitive period in life in order to transfer its functional specialization for space processing toward a non-visual modality. Finally, dynamic causal modeling revealed that different architectures of cortical pathways underlie auditory activity in primary occipital cortex of CB and LB. Altogether, these results demonstrate important quantitative and qualitative changes in the cortical reorganizations observed in the CB and LB, unraveling the critical role of early versus late experience in shaping the functional architecture of the occipital cortex. These results are clinically important now that a growing number of therapeutic interventions may restore vision after a period of visual deprivation. Meeting abstract presented at VSS 2012

Previous studies have shown that complex visual stimuli, such as emotional facial expressions, can influence brain activity independently of the observers' awareness. Little is known yet, however, about the "informational correlates" of consciousness i.e., which low-level information correlates with brain activation during conscious vs. non-conscious perception. Here, we investigated this question in the spatial frequency (SF) domain. We examined which SFs in disgusted and fearful faces modulate activation in the insula and amygdala over time and as a function of awareness, using a combination of intracranial event-related potentials (ERPs), SF Bubbles (Willenbeckel et al., 2010a), and Continuous Flash Suppression (CFS; Tsuchiya and Koch, 2005). Patients implanted with electrodes for epilepsy monitoring viewed face photographs (13 x 7) that were randomly SF filtered on a trial-by-trial basis. In the conscious condition, the faces were visible; in the non-conscious condition, they were rendered invisible using CFS. The data were analyzed by performing multiple linear regressions on the SF filters from each trial and the transformed ERP amplitudes across time. The resulting classification images suggest that many SFs are involved in the conscious and non-conscious perception of emotional expressions, with SFs between 6 and 10 cycles per face width being particularly important early on. The results also revealed qualitative differences between the awareness conditions for both regions. Non-conscious processing relied on low SFs more and was faster than conscious processing. Overall, our findings are consistent with the idea that different pathways are employed for the processing of emotional stimuli under different degrees of awareness. The present study represents a first step to mapping how SF information "flows" through the emotion-processing network with a high temporal resolution and to shedding light on the informational correlates of consciousness in general.

Injuries at various levels of the auditory system have been shown to lead to functional reorganization of the auditory pathways. In particular, it has recently been shown that such reorganization can occur in callosal agenesis. The pattern of cortical activity following callosotomy is however still unknown, but behavioral results suggest that it could be significantly different from that observed in callosal agenesis. We aimed to confirm this hypothesis by investigating fMRI responses to complex sounds presented binaurally and monaurally in a callosotomized patient. In the binaural condition, the callosotomized subject showed patterns of auditory cortical activation that were similar to those of neurologically intact individuals. However, in both monaural conditions, the callosotomized individual showed a significant increase of the asymmetries favoring the contralateral pathways. Such patterns of cortical responses are only partially consistent with the results obtained from callosal agenesis subjects using the exact same procedure. Indeed, the latter show differences compared with normals in both binaural and monaural conditions. These findings provide neurological evidence that callosotomy could lead to distinctive functional reorganization of the human auditory pathways.

Last year at VSS, we showed that the same spatial frequencies (SFs) are used for the identification of upright and inverted inner facial features (Abstract #153). Here, we report three follow-up experiments based on the same SF Bubbles technique to shed light on the relationship between the face inversion effect (Yin, 1969) and the composite face effect (Young, Hellawell, & Hay, 1987). In Experiment 1, we replicated our previous findings on the face inversion effect in a 10-choice identification task with 300 trials per orientation and per observer and with 20 faces from the set of Goffaux and Rossion (2006) revealed through an elliptical aperture hiding contour information—the same SFs were used to identify upright and inverted faces. In Experiment 2, we displayed the faces of Experiment 1 with contour information. For upright face identification, we replicated our previous results for inverted faces, however, the use of SFs was shifted toward lower SFs. Intriguingly, this shift is in the opposite direction to that predicted by Goffaux and Rossion (2006) who found that holistic processing is largely supported by low SFs. In Experiment 3, we re-examined SF tuning in the composite face paradigm of Goffaux and Rossion (2006) using the SF Bubbles technique. Preliminary results confirm and extend their results. In sum, holistic processing—as indexed by the composite face effect—and face identification appear to be mediated by different SFs.