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1.
J Vis ; 24(1): 3, 2024 Jan 02.
Article in English | MEDLINE | ID: mdl-38190145

ABSTRACT

Visual scene perception is based on reciprocal interactions between central and peripheral information. Such interactions are commonly investigated through the semantic congruence effect, which usually reveals a congruence effect of central vision on peripheral vision as strong as the reverse. The aim of the present study was to further investigate the mechanisms underlying central-peripheral visual interactions using a central-peripheral congruence paradigm through three behavioral experiments. We presented simultaneously a central and a peripheral stimulus, that could be either semantically congruent or incongruent. To assess the congruence effect of central vision on peripheral vision, participants had to categorize the peripheral target stimulus while ignoring the central distractor stimulus. To assess the congruence effect of the peripheral vision on central vision, they had to categorize the central target stimulus while ignoring the peripheral distractor stimulus. Experiment 1 revealed that the physical distance between central and peripheral stimuli influences central-peripheral visual interactions: Congruence effect of central vision is stronger when the distance between the target and the distractor is the shortest. Experiments 2 and 3 revealed that the spatial frequency content of distractors also influence central-peripheral interactions: Congruence effect of central vision is observed only when the distractor contained high spatial frequencies while congruence effect of peripheral vision is observed only when the distractor contained low spatial frequencies. These results raise the question of how these influences are exerted (bottom-up vs. top-down) and are discussed based on the retinocortical properties of the visual system and the predictive brain hypothesis.


Subject(s)
Brain , Visual Perception , Humans , Semantics
2.
Vision Res ; 211: 108281, 2023 10.
Article in English | MEDLINE | ID: mdl-37421829

ABSTRACT

Models of emotion processing suggest that threat-related stimuli such as fearful faces can be detected based on the rapid extraction of low spatial frequencies. However, this remains debated as other models argue that the decoding of facial expressions occurs with a more flexible use of spatial frequencies. The purpose of this study was to clarify the role of spatial frequencies and differences in luminance contrast between spatial frequencies, on the detection of facial emotions. We used a saccadic choice task in which emotional-neutral face pairs were presented and participants were asked to make a saccade toward the neutral or the emotional (happy or fearful) face. Faces were displayed either in low, high, or broad spatial frequencies. Results showed that participants were better to saccade toward the emotional face. They were also better for high or broad than low spatial frequencies, and the accuracy was higher with a happy target. An analysis of the eye and mouth saliency ofour stimuli revealed that the mouth saliency of the target correlates with participants' performance. Overall, this study underlines the importance of local more than global information, and of the saliency of the mouth region in the detection of emotional and neutral faces.


Subject(s)
Emotions , Saccades , Humans , Happiness , Facial Expression
3.
Vision Res ; 206: 108191, 2023 05.
Article in English | MEDLINE | ID: mdl-36773476

ABSTRACT

Predictive coding theories of visual perception assume that expectations based on prior knowledge modulate the processing of information. However, the underlying mechanisms remain debated. Some accounts propose that expectations enhance the perception of expected relative to unexpected stimuli while others assume the opposite. Recently, the opposing process theory suggested that enhanced perception of expected vs. unexpected stimuli may occur alternatively depending upon the reliability of the visual signal. When the signal is noisy, perception would be biassed toward what is expected since anything else may be too noisy to be resolved. When the signal is unambiguous, perception would be biassed toward what diverges from expectations and is more informative. Our study tested this hypothesis, using a perceptual matching task to investigate the influence of expectations on the perceived sharpness of objects in context. Participants saw two blurred images depicting the same object and had to adjust the blur level of one object to match the blur level of the other one. We manipulated the validity of expectations about objects by varying their scene context (congruent or incongruent context leading to valid or invalid expectations about the object). We also manipulated the reliability of the visual signal by varying the initial blur level of object pairs. Results showed that expectations validity differentially affected the perception of objects depending on signal reliability. Perception of validly expected objects was enhanced (sharpened) relative to unexpected objects when visual inputs were unreliable while this effect reversed to the benefit of unexpected objects when the signal was more reliable.


Subject(s)
Motivation , Visual Perception , Humans , Reproducibility of Results , Knowledge
4.
Vis Neurosci ; 40: E001, 2023 02 08.
Article in English | MEDLINE | ID: mdl-36752177

ABSTRACT

Glaucoma is an eye disease characterized by a progressive vision loss usually starting in peripheral vision. However, a deficit for scene categorization is observed even in the preserved central vision of patients with glaucoma. We assessed the processing and integration of spatial frequencies in the central vision of patients with glaucoma during scene categorization, considering the severity of the disease, in comparison to age-matched controls. In the first session, participants had to categorize scenes filtered in low-spatial frequencies (LSFs) and high-spatial frequencies (HSFs) as a natural or an artificial scene. Results showed that the processing of spatial frequencies was impaired only for patients with severe glaucoma, in particular for HFS scenes. In the light of proactive models of visual perception, we investigated how LSF could guide the processing of HSF in a second session. We presented hybrid scenes (combining LSF and HSF from two scenes belonging to the same or different semantic category). Participants had to categorize the scene filtered in HSF while ignoring the scene filtered in LSF. Surprisingly, results showed that the semantic influence of LSF on HSF was greater for patients with early glaucoma than controls, and then disappeared for the severe cases. This study shows that a progressive destruction of retinal ganglion cells affects the spatial frequency processing in central vision. This deficit may, however, be compensated by increased reliance on predictive mechanisms at early stages of the disease which would however decline in more severe cases.


Subject(s)
Glaucoma , Space Perception , Humans , Reaction Time , Photic Stimulation/methods , Visual Perception , Pattern Recognition, Visual
5.
Psychopharmacology (Berl) ; 240(2): 271-282, 2023 Feb.
Article in English | MEDLINE | ID: mdl-36688964

ABSTRACT

RATIONALE: Dominant theoretical models postulate the presence of an automatic attentional bias (AB) towards alcohol-related stimuli in alcohol use disorder, such AB constituting a core feature of this disorder. An early alcohol AB has been documented in subclinical populations such as binge drinking (i.e., a drinking pattern prevalent in youth and characterized by repeated alternation between alcohol intoxications and withdrawals, generating cerebral consequences). However, the automatic nature of AB remains to be established. OBJECTIVES: We investigated the automatic nature of AB in binge drinkers through the saccadic choice task. This eye-tracking paradigm consistently highlights the extremely fast and involuntary saccadic responses elicited by faces in humans, relative to other object categories. Through an alcohol-related adaptation of the saccadic choice task, we tested whether the early and automatic capture of attentional resources elicited by faces can also be found for alcohol-related stimuli in binge drinkers, as predicted by theoretical models. METHODS: Forty-three binge drinkers and 44 control participants performed two versions of the saccadic choice task. In the original version, two images (a face, a vehicle) were displayed on the left and right side of the screen respectively. Participants had to perform a saccade as fast as possible towards the target stimulus (either face or vehicle). In the alcohol-related version, the task was identical, but the images were an alcoholic beverage and a non-alcoholic stimulus. RESULTS: We replicated the automatic attraction towards faces in both groups, as faces generated higher saccadic accuracy, speed, and amplitude than vehicles, as well as higher corrective saccade proportion. Concerning the alcohol-related adaptation of the task, groups did not differ for the accuracy, speed, and amplitude of the first saccade towards alcohol. However, binge drinkers differed from controls regarding the proportion of corrective saccade towards non-alcoholic stimuli after an error saccade towards alcohol, suggesting the presence of an alcohol disengagement bias specific to binge drinkers. CONCLUSIONS: Alcohol-related AB in binge drinkers is not characterized by an early and automatic hijacking of attention towards alcohol. This AB rather relies on later and more controlled processing stages, namely a difficulty to disengage attentional resources from alcohol-related stimuli.


Subject(s)
Eye-Tracking Technology , Saccades , Adolescent , Humans , Attention/physiology , Alcohol Drinking , Ethanol , Cues
6.
Heliyon ; 8(12): e11964, 2022 Dec.
Article in English | MEDLINE | ID: mdl-36561662

ABSTRACT

In this article, we tested the respective importance of low spatial frequencies (LSF) and high spatial frequencies (HSF) for conscious visual recognition of emotional stimuli by using an attentional blink paradigm. Thirty-eight participants were asked to identify and report two targets (happy faces) embedded in a rapid serial visual presentation of distractors (angry faces). During attentional blink, conscious perception of the second target (T2) is usually altered when the lag between the two targets is short (200-500 ms) but is restored at longer lags. The distractors between T1 and T2 were either non-filtered (broad spatial frequencies, BSF), low-pass filtered (LSF), or high-pass filtered (HSF). Assuming that prediction abilities could be at the root of conscious visual recognition, we expected that LSF distractors could result in a greater disturbance of T2 reporting than HSF distractors. Results showed that both LSF and HSF play a role in the emergence of exogenous consciousness in the visual system. Furthermore, HSF distractors strongly affected T1 and T2 reporting irrespective of the lag between targets, suggesting their role for facial emotion processing. We discuss these results with regards to other models of visual recognition. .

7.
J Exp Psychol Hum Percept Perform ; 48(4): 331-350, 2022 Apr.
Article in English | MEDLINE | ID: mdl-35130017

ABSTRACT

Predictive coding theories of visual perception postulate that expectations based on prior knowledge modulate the processing of information by sharpening the representation of expected features of a stimulus in visual cortex but few studies directly investigated whether expectations qualitatively affect perception. Our study investigated the influence of expectations based on prior experience and contextual information on the perceived sharpness of objects and scenes. In Experiments 1 and 2, we used a perceptual matching task. Participants saw two blurred images depicting the same object or scene and had to adjust the blur level of the right image to match the blur level of the left one. We manipulated the availability of relevant information to form expectations about the image's content: one of the two images contained predictable information while the other one unpredictable. At an equal level of blur, predictable objects and scenes were perceived as sharper than unpredictable ones. Experiment 3 involving explicit sharpness judgments confirmed these results. Our findings support the sharpening account of predictive coding theories by showing that expectations increase the perceived sharpness of the visual signal. Expectations about the visual environment help us understand it more easily, but also makes us perceive it better. (PsycInfo Database Record (c) 2022 APA, all rights reserved).


Subject(s)
Visual Cortex , Humans , Judgment , Pattern Recognition, Visual , Visual Perception
8.
Neuroimage Clin ; 33: 102906, 2022.
Article in English | MEDLINE | ID: mdl-34891045

ABSTRACT

BACKGROUND: Parkinson's disease (PD) manifests with the appearance of non-motor symptoms before motor symptoms onset. Among these, dysfunctioning visual structures have recently been reported to occur at early disease stages. OBJECTIVE: This study addresses effective connectivity in the visual network of PD patients. METHODS: Using functional MRI and dynamic causal modeling analysis, we evaluated the connectivity between the superior colliculus, the lateral geniculate nucleus and the primary visual area V1 in de novo untreated PD patients (n = 22). A subset of the PD patients (n = 8) was longitudinally assessed two times at two months and at six months after starting dopaminergic treatment. Results were compared to those of age-matched healthy controls (n = 22). RESULTS: Our results indicate that the superior colliculus drives cerebral activity for luminance contrast processing both in healthy controls and untreated PD patients. The same effective connectivity was observed with neuromodulatory differences in terms of neuronal dynamic interactions. Our main findings were that the modulation induced by luminance contrast changes of the superior colliculus connectivity (self-connectivity and connectivity to the lateral geniculate nucleus) was inhibited in PD patients (effect of contrast: p = 0.79 and p = 0.77 respectively). The introduction of dopaminergic medication in a subset (n = 8) of the PD patients failed to restore the effective connectivity modulation observed in the healthy controls. INTERPRETATION: The deficits in luminance contrast processing in PD was associated with a deficiency in connectivity adjustment from the superior colliculus to the lateral geniculate nucleus and to V1. No differences in cerebral blood flow were observed between controls and PD patients suggesting that the deficiency was at the neuronal level. Administration of a dopaminergic treatment over six months was not able to normalize the observed alterations in inter-regional coupling. These findings highlight the presence of early dysfunctions in primary visual areas, which might be used as early markers of the disease.


Subject(s)
Parkinson Disease , Dopamine , Dopamine Agents , Humans , Magnetic Resonance Imaging , Neural Pathways/diagnostic imaging , Parkinson Disease/complications , Parkinson Disease/diagnostic imaging , Parkinson Disease/drug therapy
9.
Cogn Sci ; 45(10): e13042, 2021 10.
Article in English | MEDLINE | ID: mdl-34606110

ABSTRACT

Previous studies have shown that the human visual system can detect a face and elicit a saccadic eye movement toward it very efficiently compared to other categories of visual stimuli. In the first experiment, we tested the influence of facial expressions on fast face detection using a saccadic choice task. Face-vehicle pairs were simultaneously presented and participants were asked to saccade toward the target (the face or the vehicle). We observed that saccades toward faces were initiated faster, and more often in the correct direction, than saccades toward vehicles, regardless of the facial expressions (happy, fearful, or neutral). We also observed that saccade endpoints on face images were lower when the face was happy and higher when it was neutral. In the second experiment, we explicitly tested the detection of facial expressions. We used a saccadic choice task with emotional-neutral pairs of faces and participants were asked to saccade toward the emotional (happy or fearful) or the neutral face. Participants were faster when they were asked to saccade toward the emotional face. They also made fewer errors, especially when the emotional face was happy. Using computational modeling, we showed that this happy face advantage can, at least partly, be explained by perceptual factors. Also, saccade endpoints were lower when the target was happy than when it was fearful. Overall, we suggest that there is no automatic prioritization of emotional faces, at least for saccades with short latencies, but that salient local face features can automatically attract attention.


Subject(s)
Emotions , Saccades , Attention , Facial Expression , Humans , Reaction Time
10.
Neuroimage ; 244: 118559, 2021 12 01.
Article in English | MEDLINE | ID: mdl-34562697

ABSTRACT

The human lateral geniculate nucleus (LGN) of the visual thalamus is a key subcortical processing site for visual information analysis. Due to its small size and deep location within the brain, a non-invasive characterization of the LGN and its microstructurally distinct magnocellular (M) and parvocellular (P) subdivisions in humans is challenging. Here, we investigated whether structural quantitative MRI (qMRI) methods that are sensitive to underlying microstructural tissue features enable MR-based mapping of human LGN M and P subdivisions. We employed high-resolution 7 Tesla in-vivo qMRI in N = 27 participants and ultra-high resolution 7 Tesla qMRI of a post-mortem human LGN specimen. We found that a quantitative assessment of the LGN and its subdivisions is possible based on microstructure-informed qMRI contrast alone. In both the in-vivo and post-mortem qMRI data, we identified two components of shorter and longer longitudinal relaxation time (T1) within the LGN that coincided with the known anatomical locations of a dorsal P and a ventral M subdivision, respectively. Through ground-truth histological validation, we further showed that the microstructural MRI contrast within the LGN pertains to cyto- and myeloarchitectonic tissue differences between its subdivisions. These differences were based on cell and myelin density, but not on iron content. Our qMRI-based mapping strategy paves the way for an in-depth understanding of LGN function and microstructure in humans. It further enables investigations into the selective contributions of LGN subdivisions to human behavior in health and disease.


Subject(s)
Geniculate Bodies/diagnostic imaging , Magnetic Resonance Imaging/methods , Adult , Female , Geniculate Bodies/cytology , Humans , Male , Young Adult
11.
J Cogn Neurosci ; 33(5): 799-813, 2021 04 01.
Article in English | MEDLINE | ID: mdl-34449843

ABSTRACT

Theories of visual recognition postulate that our ability to understand our visual environment at a glance is based on the extraction of the gist of the visual scene, a first global and rudimentary visual representation. Gist perception would be based on the rapid analysis of low spatial frequencies in the visual signal and would allow a coarse categorization of the scene. We aimed to study whether the low spatial resolution information available in peripheral vision could modulate the processing of visual information presented in central vision. We combined behavioral measures (Experiments 1 and 2) and fMRI measures (Experiment 2). Participants categorized a scene presented in central vision (artificial vs. natural categories) while ignoring another scene, either semantically congruent or incongruent, presented in peripheral vision. The two scenes could either share the same physical properties (similar amplitude spectrum and spatial configuration) or not. Categorization of the central scene was impaired by a semantically incongruent peripheral scene, in particular when the two scenes were physically similar. This semantic interference effect was associated with increased activation of the inferior frontal gyrus. When the two scenes were semantically congruent, the dissimilarity of their physical properties impaired the categorization of the central scene. This effect was associated with increased activation in occipito-temporal areas. In line with the hypothesis of predictive mechanisms involved in visual recognition, results suggest that semantic and physical properties of the information coming from peripheral vision would be automatically used to generate predictions that guide the processing of signal in central vision.


Subject(s)
Semantics , Visual Perception , Hemodynamics , Humans , Magnetic Resonance Imaging , Pattern Recognition, Visual , Photic Stimulation , Recognition, Psychology
12.
J Vis ; 21(2): 4, 2021 02 03.
Article in English | MEDLINE | ID: mdl-33544121

ABSTRACT

Previous studies have shown that face stimuli influence the programming of eye movements by eliciting involuntary and extremely fast saccades toward them. The present study examined whether holistic processing of faces mediates these effects. We used a saccadic choice task in which participants were presented simultaneously with two images and had to perform a saccade toward the one containing a target stimulus (e.g., a face). Across three experiments, stimuli were altered via upside-down inversion (Experiment 1) or scrambling of thumbnails within the images (Experiments 2 and 3) in order to disrupt holistic processing. We found that disruption of holistic processing only had a limited impact on the latency of saccades toward face targets, which remained extremely short (minimum saccadic reaction times of only ∼120-130 ms), and did not affect the proportion of error saccades toward face distractors that captured attention more than other distractor categories. It, however, resulted in increasing error rate of saccades toward face targets. These results suggest that the processing of isolated face features is sufficient to elicit extremely fast and involuntary saccadic responses toward them. Holistic representations of faces may, however, be used as a search template to accurately detect faces.


Subject(s)
Facial Recognition/physiology , Saccades/physiology , Adult , Attention/physiology , Eye Movements , Female , Humans , Male , Orientation, Spatial/physiology , Reaction Time/physiology , Young Adult
13.
Vision Res ; 170: 60-72, 2020 05.
Article in English | MEDLINE | ID: mdl-32259648

ABSTRACT

Studies on scene perception have shown that the rapid extraction of low spatial frequencies (LSF) allows a coarse parsing of the scene, prior to the analysis of high spatial frequencies (HSF) containing details. Many studies suggest that scene gist recognition can be achieved with only the low resolution of peripheral vision. Our study investigated the advantage of peripheral vision on central vision during a scene categorization task (indoor vs. outdoor). In Experiment 1, we used large scene photographs from which we built one central disk and four circular rings of different eccentricities. The central disk either contained or not an object semantically related to the scene category. Results showed better categorization performances for the peripheral rings, despite the presence of an object in central vision that was semantically related to the scene category that significantly improved categorization performances. In Experiment 2, the central disk and rings were assembled from Central to Peripheral vision (CtP sequence) or from Peripheral to Central vision (PtC sequence). Results revealed better performances for PtC than CtP sequences, except when no central object was present under rapid categorization constraints. As Experiment 3 suggested that the PtC advantage was not explained by a reduction of the visibility of the object in the central disk by the surrounding peripheral rings (CtP sequence), results are interpreted in the context of a predominant coarse-to-fine processing during scene categorization, with greater efficiency and utility of coarse peripheral vision relative to fine central vision during rapid scene categorization.


Subject(s)
Recognition, Psychology , Semantics , Visual Perception , Humans , Vision, Ocular
14.
J Vis ; 19(14): 7, 2019 12 02.
Article in English | MEDLINE | ID: mdl-31826252

ABSTRACT

Predictive models of visual recognition state that predictions based on the rapid processing of low spatial frequencies (LSF) may guide the subsequent processing of high spatial frequencies (HSF). While the HSF signal necessarily comes from central vision, most of the LSF signal comes from peripheral vision. The present study aimed at understanding how LSF in peripheral vision may be used to generate predictive signals that guide visual processes in central vision. In two experiments, participants performed an object categorization task in central vision while a semantically congruent or incongruent scene background was displayed in peripheral vision. In Experiment 1, results showed a congruence effect when the peripheral scene was displayed before the object onset. In Experiment 2, results showed a congruence effect only when the peripheral scene was intact, thus carrying a semantic meaning, but not when it was phase-scrambled, thus carrying only low-level information. The study suggests that the low resolution of peripheral vision facilitates the processing of foveated objects in the visual scene, in line with predictive models of visual recognition.


Subject(s)
Pattern Recognition, Visual/physiology , Recognition, Psychology/physiology , Vision, Ocular/physiology , Visual Perception/physiology , Adolescent , Adult , Female , Humans , Male , Photic Stimulation , Semantics , Young Adult
15.
Sci Rep ; 9(1): 560, 2019 01 24.
Article in English | MEDLINE | ID: mdl-30679472

ABSTRACT

Previous studies have shown that face stimuli elicit extremely fast and involuntary saccadic responses toward them, relative to other categories of visual stimuli. In the present study, we further investigated to what extent face stimuli influence the programming and execution of saccades examining their amplitude. We performed two experiments using a saccadic choice task: two images (one with a face, one with a vehicle) were simultaneously displayed in the left and right visual fields of participants who had to initiate a saccade toward the image (Experiment 1) or toward a cross in the image (Experiment 2) containing a target stimulus (a face or a vehicle). Results revealed shorter saccades toward vehicle than face targets, even if participants were explicitly asked to perform their saccades toward a specific location (Experiment 2). Furthermore, error saccades had smaller amplitude than correct saccades. Further analyses showed that error saccades were interrupted in mid-flight to initiate a concurrently-programmed corrective saccade. Overall, these data suggest that the content of visual stimuli can influence the programming of saccade amplitude, and that efficient online correction of saccades can be performed during the saccadic choice task.


Subject(s)
Face , Facial Recognition/physiology , Motor Vehicles , Saccades/physiology , Adult , Data Accuracy , Female , Healthy Volunteers , Humans , Male , Photic Stimulation/methods , Reaction Time/physiology , Visual Fields/physiology , Young Adult
16.
Neural Netw ; 109: 19-30, 2019 Jan.
Article in English | MEDLINE | ID: mdl-30388430

ABSTRACT

Different studies have shown the efficiency of a feed-forward neural network in categorizing basic emotional facial expressions. However, recent findings in psychology and cognitive neuroscience suggest that visual recognition is not a pure bottom-up process but likely involves top-down recurrent connectivity. In the present computational study, we compared the performances of a pure bottom-up neural network (a standard multi-layer perceptron, MLP) with a neural network involving recurrent top-down connections (a simple recurrent network, SRN) in the anticipation of emotional expressions. In two complementary simulations, results revealed that the SRN outperformed the MLP for ambiguous intensities in the temporal sequence, when the emotions were not fully depicted but when sufficient contextual information (related to previous time frames) was provided. Taken together, these results suggest that, despite the cost of recurrent connections in terms of energy and processing time for biological organisms, they can provide a substantial advantage for the fast recognition of uncertain visual signals.


Subject(s)
Anticipation, Psychological , Emotions , Facial Expression , Neural Networks, Computer , Synapses , Adult , Anticipation, Psychological/physiology , Brain Mapping/methods , Emotions/physiology , Female , Humans , Magnetic Resonance Imaging , Male , Synapses/physiology
17.
Front Aging Neurosci ; 10: 235, 2018.
Article in English | MEDLINE | ID: mdl-30123123

ABSTRACT

Normal aging is characterized by decline in cognitive functioning in conjunction with extensive gray matter (GM) atrophy. A first aim of this study was to determine GM volume differences related to aging by comparing two groups of participants, middle-aged group (MAG, mean age 41 years, N = 16) and older adults (OG, mean age 71 years, N = 14) who underwent an magnetic resonance images (MRI) voxel-based morphometry (VBM) evaluation. The VBM analyses included two optimized pipelines, for the cortex and for the cerebellum. Participants were also evaluated on a wide range of cognitive tests assessing both domain-general and language-specific processes, in order to examine how GM volume differences between OG and MAG relate to cognitive performance. Our results show smaller bilateral GM volume in the OG relative to the MAG, in several cerebral and right cerebellar regions involved in language and executive functions. Importantly, our results also revealed smaller GM volume in the right cerebellum in OG relative to MAG, supporting the idea of a complex cognitive role for this structure. This study provides a broad picture of cerebral, but also cerebellar and cognitive changes associated with normal aging.

18.
Vis Neurosci ; 35: E006, 2018 01.
Article in English | MEDLINE | ID: mdl-29905126

ABSTRACT

In age-related macular degeneration (AMD), the processing of fine details in a visual scene, based on a high spatial frequency processing, is impaired, while the processing of global shapes, based on a low spatial frequency processing, is relatively well preserved. The present fMRI study aimed to investigate the residual abilities and functional brain changes of spatial frequency processing in visual scenes in AMD patients. AMD patients and normally sighted elderly participants performed a categorization task using large black and white photographs of scenes (indoors vs. outdoors) filtered in low and high spatial frequencies, and nonfiltered. The study also explored the effect of luminance contrast on the processing of high spatial frequencies. The contrast across scenes was either unmodified or equalized using a root-mean-square contrast normalization in order to increase contrast in high-pass filtered scenes. Performance was lower for high-pass filtered scenes than for low-pass and nonfiltered scenes, for both AMD patients and controls. The deficit for processing high spatial frequencies was more pronounced in AMD patients than in controls and was associated with lower activity for patients than controls not only in the occipital areas dedicated to central and peripheral visual fields but also in a distant cerebral region specialized for scene perception, the parahippocampal place area. Increasing the contrast improved the processing of high spatial frequency content and spurred activation of the occipital cortex for AMD patients. These findings may lead to new perspectives for rehabilitation procedures for AMD patients.


Subject(s)
Occipital Lobe/physiology , Spatial Processing/physiology , Visual Perception/physiology , Wet Macular Degeneration/metabolism , Aged , Brain Mapping , Exudates and Transudates , Female , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Tomography, Optical Coherence , Visual Fields , Wet Macular Degeneration/diagnostic imaging
19.
Clin Linguist Phon ; 32(7): 595-621, 2018.
Article in English | MEDLINE | ID: mdl-29148845

ABSTRACT

The rehabilitation of speech disorders benefits from providing visual information which may improve speech motor plans in patients. We tested the proof of concept of a rehabilitation method (Sensori-Motor Fusion, SMF; Ultraspeech player) in one post-stroke patient presenting chronic non-fluent aphasia. SMF allows visualisation by the patient of target tongue and lips movements using high-speed ultrasound and video imaging. This can improve the patient's awareness of his/her own lingual and labial movements, which can, in turn, improve the representation of articulatory movements and increase the ability to coordinate and combine articulatory gestures. The auditory and oro-sensory feedback received by the patient as a result of his/her own pronunciation can be integrated with the target articulatory movements they watch. Thus, this method is founded on sensorimotor integration during speech. The SMF effect on this patient was assessed through qualitative comparison of language scores and quantitative analysis of acoustic parameters measured in a speech production task, before and after rehabilitation. We also investigated cerebral patterns of language reorganisation for rhyme detection and syllable repetition, to evaluate the influence of SMF on phonological-phonetic processes. Our results showed that SMF had a beneficial effect on this patient who qualitatively improved in naming, reading, word repetition and rhyme judgment tasks. Quantitative measurements of acoustic parameters indicate that the patient's production of vowels and syllables also improved. Compared with pre-SMF, the fMRI data in the post-SMF session revealed the activation of cerebral regions related to articulatory, auditory and somatosensory processes, which were expected to be recruited by SMF. We discuss neurocognitive and linguistic mechanisms which may explain speech improvement after SMF, as well as the advantages of using this speech rehabilitation method.


Subject(s)
Aphasia, Broca/therapy , Language , Neuronal Plasticity , Speech Therapy/methods , Speech/physiology , Feedback, Sensory/physiology , Female , Humans , Lip , Magnetic Resonance Imaging , Tongue
20.
Front Hum Neurosci ; 11: 325, 2017.
Article in English | MEDLINE | ID: mdl-28690506

ABSTRACT

It has been suggested that dorsal and ventral pathways support distinct aspects of language processing. Yet, the full extent of their involvement and their inter-regional connectivity in visual word recognition is still unknown. Studies suggest that they might reflect the dual-route model of reading, with the dorsal pathway more involved in grapho-phonological conversion during phonological tasks, and the ventral pathway performing lexico-semantic access during semantic tasks. Furthermore, this subdivision is also suggested at the level of the inferior frontal cortex, involving ventral and dorsal parts for lexico-semantic and phonological processing, respectively. In the present study, we assessed inter-regional brain connectivity and task-induced modulations of brain activity during a phoneme detection and semantic categorization tasks, using fMRI in healthy subject. We used a dynamic causal modeling approach to assess inter-regional connectivity and task demand modulation within the dorsal and ventral pathways, including the following network components: the ventral occipito-temporal cortex (vOTC; dorsal and ventral), the superior temporal gyrus (STG; dorsal), the dorsal inferior frontal gyrus (dIFG; dorsal), and the ventral IFG (vIFG; ventral). We report three distinct inter-regional interactions supporting orthographic information transfer from vOTC to other language regions (vOTC -> STG, vOTC -> vIFG and vOTC -> dIFG) regardless of task demands. Moreover, we found that (a) during semantic processing (direct ventral pathway) the vOTC -> vIFG connection strength specifically increased and (b) a lack of modulation of the vOTC -> dIFG connection strength by the task that could suggest a more general involvement of the dorsal pathway during visual word recognition. Results are discussed in terms of anatomo-functional connectivity of visual word recognition network.

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