ventral visual stream
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Recognition memory is the ability to recognize previously encountered objects. Even this relatively simple, yet extremely fast, ability requires the coordinated activity of large-scale brain networks. However, little is known about the sub-second dynamics of these networks. The majority of current studies into large-scale network dynamics is primarily based on imaging techniques suffering from either poor temporal or spatial resolution. We investigated the dynamics of large-scale functional brain networks underlying recognition memory at the millisecond scale. Specifically, we analyzed dynamic effective connectivity from intracranial electroencephalography while epileptic subjects (n = 18) performed a fast visual recognition memory task. Our data-driven investigation using Granger causality and the analysis of communities with the Louvain algorithm spotlighted a dynamic interplay of two large-scale networks associated with successful recognition. The first network involved the right visual ventral stream and bilateral frontal regions. It was characterized by early, predominantly bottom-up information flow peaking at 115 ms. It was followed by the involvement of another network with predominantly top-down connectivity peaking at 220 ms, mainly in the left anterior hemisphere. The transition between these two networks was associated with changes in network topology, evolving from a more segregated to a more integrated state. These results highlight that distinct large-scale brain networks involved in visual recognition memory unfold early and quickly, within the first 300 ms after stimulus onset. Our study extends the current understanding of the rapid network changes during rapid cognitive processes.
Spatial reference frames (RFs) play a key role in spatial cognition, especially in perception, spatial memory, and navigation. There are two main types of RFs: egocentric (self-centered) and allocentric (object-centered). Although many fMRI studies examined the neural correlates of egocentric and allocentric RFs, they could not sample the fast temporal dynamics of the underlying cognitive processes. Therefore, the interaction and timing between these two RFs remain unclear. Taking advantage of the high temporal resolution of intracranial EEG (iEEG), we aimed to determine the timing of egocentric and allocentric information processing and describe the brain areas involved. We recorded iEEG and analyzed broad gamma activity (50-150 Hz) in 37 epilepsy patients performing a spatial judgment task in a three-dimensional circular virtual arena. We found overlapping activation for egocentric and allocentric RFs in many brain regions, with several additional egocentric- and allocentric-selective areas. In contrast to the egocentric responses, the allocentric responses peaked later than the control ones in frontal regions with overlapping selectivity. Also, across several egocentric or allocentric selective areas, the egocentric selectivity appeared earlier than the allocentric one. We identified the maximum number of egocentric-selective channels in the medial occipito-temporal region and allocentric-selective channels around the intraparietal sulcus in the parietal cortex. Our findings favor the hypothesis that egocentric spatial coding is a more primary process, and allocentric representations may be derived from egocentric ones. They also broaden the dominant view of the dorsal and ventral streams supporting egocentric and allocentric space coding, respectively.
INTRODUCTION: Intracranial EEG (iEEG) data is a powerful way to map brain function, characterized by high temporal and spatial resolution, allowing the study of interactions among neuronal populations that orchestrate cognitive processing. However, the statistical inference and analysis of brain networks using iEEG data faces many challenges related to its sparse brain coverage, and its inhomogeneity across patients. METHODS: We review these challenges and develop a methodological pipeline for estimation of network structure not obtainable from any single patient, illustrated on the inference of the interaction among visual streams using a dataset of 27 human iEEG recordings from a visual experiment employing visual scene stimuli. 100 ms sliding window and multiple band-pass filtered signals are used to provide temporal and spectral resolution. For the connectivity analysis we showcase two connectivity measures reflecting different types of interaction between regions of interest (ROI): Phase Locking Value as a symmetric measure of synchrony, and Directed Transfer Function-asymmetric measure describing causal interaction. For each two channels, initial uncorrected significance testing at p < 0.05 for every time-frequency point is carried out by comparison of the data-derived connectivity to a baseline surrogate-based null distribution, providing a binary time-frequency connectivity map. For each ROI pair, a connectivity density map is obtained by averaging across all pairs of channels spanning them, effectively agglomerating data across relevant channels and subjects. Finally, the difference of the mean map value after and before the stimulation is compared to the same statistic in surrogate data to assess link significance. RESULTS: The analysis confirmed the function of the parieto-medial temporal pathway, mediating visuospatial information between dorsal and ventral visual streams during visual scene analysis. Moreover, we observed the anterior hippocampal connectivity with more posterior areas in the medial temporal lobe, and found the reciprocal information flow between early processing areas and medial place area. DISCUSSION: To summarize, we developed an approach for estimating network connectivity, dealing with the challenge of sparse individual coverage of intracranial EEG electrodes. Its application provided new insights into the interaction between the dorsal and ventral visual streams, one of the iconic dualities in human cognition.
- Publikační typ
- časopisecké články MeSH
Human perception and cognition are based predominantly on visual information processing. Much of the information regarding neuronal correlates of visual processing has been derived from functional imaging studies, which have identified a variety of brain areas contributing to visual analysis, recognition, and processing of objects and scenes. However, only two of these areas, namely the parahippocampal place area (PPA) and the lateral occipital complex (LOC), were verified and further characterized by intracranial electroencephalogram (iEEG). iEEG is a unique measurement technique that samples a local neuronal population with high temporal and anatomical resolution. In the present study, we aimed to expand on previous reports and examine brain activity for selectivity of scenes and objects in the broadband high-gamma frequency range (50-150 Hz). We collected iEEG data from 27 epileptic patients while they watched a series of images, containing objects and scenes, and we identified 375 bipolar channels responding to at least one of these two categories. Using K-means clustering, we delineated their brain localization. In addition to the two areas described previously, we detected significant responses in two other scene-selective areas, not yet reported by any electrophysiological studies; namely the occipital place area (OPA) and the retrosplenial complex. Moreover, using iEEG we revealed a much broader network underlying visual processing than that described to date, using specialized functional imaging experimental designs. Here, we report the selective brain areas for scene processing include the posterior collateral sulcus and the anterior temporal region, which were already shown to be related to scene novelty and landmark naming. The object-selective responses appeared in the parietal, frontal, and temporal regions connected with tool use and object recognition. The temporal analyses specified the time course of the category selectivity through the dorsal and ventral visual streams. The receiver operating characteristic analyses identified the PPA and the fusiform portion of the LOC as being the most selective for scenes and objects, respectively. Our findings represent a valuable overview of visual processing selectivity for scenes and objects based on iEEG analyses and thus, contribute to a better understanding of visual processing in the human brain.
- Publikační typ
- časopisecké články MeSH
Visual processing difficulties are often present in Alzheimer's disease (AD), even in its pre-dementia phase (i.e. in mild cognitive impairment, MCI). The default mode network (DMN) modulates the brain connectivity depending on the specific cognitive demand, including visual processes. The aim of the present study was to analyze specific changes in connectivity of the posterior DMN node (i.e. the posterior cingulate cortex and precuneus, PCC/P) associated with visual processing in 17 MCI patients and 15 AD patients as compared to 18 healthy controls (HC) using functional magnetic resonance imaging. We used psychophysiological interaction (PPI) analysis to detect specific alterations in PCC connectivity associated with visual processing while controlling for brain atrophy. In the HC group, we observed physiological changes in PCC connectivity in ventral visual stream areas and with PCC/P during the visual task, reflecting the successful involvement of these regions in visual processing. In the MCI group, the PCC connectivity changes were disturbed and remained significant only with the anterior precuneus. In between-group comparison, we observed significant PPI effects in the right superior temporal gyrus in both MCI and AD as compared to HC. This change in connectivity may reflect ineffective "compensatory" mechanism present in the early pre-dementia stages of AD or abnormal modulation of brain connectivity due to the disease pathology. With the disease progression, these changes become more evident but less efficient in terms of compensation. This approach can separate the MCI from HC with 77% sensitivity and 89% specificity.
- MeSH
- Alzheimerova nemoc komplikace MeSH
- kognitivní dysfunkce diagnostické zobrazování etiologie patologie MeSH
- kyslík krev MeSH
- lidé středního věku MeSH
- lidé MeSH
- magnetická rezonanční tomografie MeSH
- modely neurologické MeSH
- mozek patologie MeSH
- nervové dráhy diagnostické zobrazování patofyziologie MeSH
- počítačové zpracování obrazu MeSH
- psychofyzika MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- stárnutí * MeSH
- světelná stimulace MeSH
- zraková percepce fyziologie MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
Audio-visual integration has been shown to be present in a wide range of different conditions, some of which are processed through the dorsal, and others through the ventral visual pathway. Whereas neuroimaging studies have revealed integration-related activity in the brain, there has been no imaging study of the possible role of segregated visual streams in audio-visual integration. We set out to determine how the different visual pathways participate in this communication. We investigated how audio-visual integration can be supported through the dorsal and ventral visual pathways during the double flash illusion. Low-contrast and chromatic isoluminant stimuli were used to drive preferably the dorsal and ventral pathways, respectively. In order to identify the anatomical substrates of the audio-visual interaction in the two conditions, the psychophysical results were correlated with the white matter integrity as measured by diffusion tensor imaging.The psychophysiological data revealed a robust double flash illusion in both conditions. A correlation between the psychophysical results and local fractional anisotropy was found in the occipito-parietal white matter in the low-contrast condition, while a similar correlation was found in the infero-temporal white matter in the chromatic isoluminant condition. Our results indicate that both of the parallel visual pathways may play a role in the audio-visual interaction.
- MeSH
- akustická stimulace MeSH
- anizotropie MeSH
- bílá hmota fyziologie MeSH
- dospělí MeSH
- lidé MeSH
- mapování mozku MeSH
- sluchová percepce fyziologie MeSH
- světelná stimulace MeSH
- teorie detekce signálu fyziologie MeSH
- zobrazování difuzních tenzorů MeSH
- zobrazování trojrozměrné MeSH
- zraková percepce fyziologie MeSH
- zrakové dráhy fyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Inconsistent information from different modalities can be delusive for perception. This phenomenon can be observed with simultaneously presented inconsistent numbers of brief flashes and short tones. The conflict of bimodal information is reflected in double flash or fission, and flash fusion illusions, respectively. The temporal resolution of the vision system plays a fundamental role in the development of these illusions. As the parallel, dorsal and ventral pathways have different temporal resolution we presume that these pathways play different roles in the illusions. We used pathway-optimized stimuli to induce the illusions on separately driven visual streams. Our results show that both pathways support the double flash illusion, while the presence of the fusion illusion depends on the activated pathway. The dorsal pathway, which has better temporal resolution, does not support fusion, while the ventral pathway which has worse temporal resolution shows fusion strongly.
- MeSH
- akustická stimulace MeSH
- časové faktory MeSH
- iluze * MeSH
- lidé MeSH
- mladý dospělý MeSH
- psychometrie MeSH
- sluchová percepce MeSH
- světelná stimulace metody MeSH
- teorie detekce signálu MeSH
- zraková percepce * MeSH
- zrakové dráhy fyziologie MeSH
- zrakové korové centrum fyziologie MeSH
- Check Tag
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Zpětně jsme hodnotili nálezy zrakových evokovaných potenciálů (VEPs) vyvolaných reverzací šachovnice (R-VEPs) a pohybovou stimulací (M-VEPs) u 20 pacientů vyšetřených během 1. ataky zánětu zrakového nervu (ON) následně sledovaných po dobu 36-135 měsíců. U 10 pacientů byla diagnostikována roztroušená skleróza (RS), u dalších 10 se v průběhu sledování RS nevyvinula. Obě skupiny se signifikantně nelišily v počtu patologických nálezů R-VEPs (u pacientů s RS 100 %, bez RS 80 %) ani M-VEPs (u pacientů s RS 80 %, bez RS 90 %). Riziko vzniku RS u pacientů s 1. atakou jednostranné ON je významně vyšší, pokud je nález R-VEPs patologický také při stimulaci nepostiženého oka (u RS v 67 %, bez RS v 22 % případů). Ačkoliv rozšíření sady VEPs o pohybové stimulace v tomto souboru pacientů s ON nezvyšuje senzitivitu vyšetření, použití M-VEPs zvyšuje spolehlivost diagnostických závěrů a umožňuje lépe posuzovat vývoj onemocnění z hlediska postižení parvocelulárního/magnocelulárního systému a ventrálního/dorzálního proudu zrakové dráhy.
Retrospective analysis of pattern-reversal VEPs (R-VEPs) and motion-onset VEPs (M-VEPs) was performed in 20 patients with first attack of acute Optic Neuritis (ON) subsequently monitored for 36-135 months during which Multiple Sclerosis (MS) developed and was confirmed in 10 of them. It did not develop in the other 10 during the term of the study. The groups with MS and without MS did not differ significantly in the extent of pathological VEP findings: in MS patients, R-VEPs were abnormal in 100 % and M-VEPs in 80 % and the non-MS patients exhibited pathology in 80 % of R-VEPs and in 90 % of M-VEPs. A higher risk of MS after unilateral optic neuritis was found in cases displaying pathological R-VEPs also in the non-affected eye (67 % of MS patients vs 22 % of non-MS patients). Although the inclusion of M-VEPs did not increase VEP examination sensitivity in ON patients, their use improves diagnostic reliability and enables better monitoring of the parvocellular/ magnocellular system and ventral/dorsal stream involvement of the visual pathway.
Zrakový systém je funkčně specializovaný a zpracovává informace hierarchicky ve dvou hlavních proudech označovaných jako systém Kde? a systém Co?. Zrakové korové mapy umístěné na zadních a vnitřních plochách hemisfér se označují VI, V2 a V3. Ventrální, neboli „přední" zrakové korové mapy jsou hV4 a VO-1. Dorzální, neboli „zadní" zrakové korové mapy V3A, V3B a V7 se rozkládají od zadní části sulcus intra-parietalis dopředu. Laterální, neboli zevní zrakové korové mapy hMT+ a LOC (MT od midtemporal, LOC je laterální okcipitální komplex) se rozkládají od týlního pólu až k sulcus temporalis superior. Mozkový systém poznávání barev začíná u S, M a L čípků sítnice, jeho hierarchicky nejvyšší místo se označuje V4. Důsledkem poškození systému je cerebrální achromatopsie. Hierarchicky nejvyšší oblastí systémů pozná¬vajícího pohyb je oblasti hMT/V5+. Důsledkem poškození je akinetopsie. Existují tři korové oblasti, které se aktivují při poznávání předmětů. Důsledkem jejich poškození je zraková agnosie objektů. Poznávání tváří je pro lidi a další primáty sociálně fundamentální. Těžištěm systému je oblast označovaná tvářová oblast gyrus fusiformis, FFA. Důsledkem poškození je prosopagnosie. Čtyři druhy topografické dezorientace jsou podmíněny poškozením systému ego - nebo exocentrické reprezentace.
The visual systém of the brain is functionally specialized. The visual information is processed through two main streams, dorsal and ventral, called the WHERE systém and the WHAT systém. VI, V2 and V3 are visual cortical maps at the posterior and medial hemispheral surface. Human V4 (hV4) and VO1 (ventral occi-pital 1) are visual cortical maps at the ventral surface of the occipital lobe. Dorsal visual cortical maps V3A, V3B and V7 are situated forwardly from the posterior part of intraparietal sulcus. Lateral visual cortical maps hMTl and LOC (lateral occipital complex) are situated from the occipital pole to the superior temporal sulcus. The brain systém of colour cognition starts with S, M and L retinal cones. Its hierarchical focal point is called V4. Cerebral achromatopsia is a result of damage to V4. Neurons of the hMT V5 visual cortical area are tuned to motion recognition. Akinetopsia results from damage to this cortical area. There are three cortical areas activated in visual object cognition. Their damage results in visual object agnosia. Face cognition is socially fundamental in humans and other sociál primates. Its hierarchical focal point is the fusiform face area, FFA. Damage here results in prosopagnosia. Four types of topographical disorientation are due to damage of ego- and/or exocentric representational systems.
Five children with a history of preterm birth (mean gestational age of 27 weeks; birth weight 870-1,380 g) and perinatal post-hemorrhagic hydrocephalus were examined ophthalmologically at ages ranging from 4-11 years. An extended visual evoked potentials (VEPs) examination was simultaneously performed, using pattern-reversal, motion-onset, and cognitive visual stimuli. Although 3 of the 10 eyes displayed about normal visual acuity (> or =0.9), all of the examined eyes were abnormal for at least one variant of the tested VEPs. Pathological changes in VEPs (missing responses, shape abnormalities due to delayed VEPs maturation, prolonged peak latencies, and reduced amplitudes) were roughly proportional to both gestational age and reduction in visual acuity. A more severe pathology was found in the motion-onset VEPs (in all five subjects - nine eyes) when compared to the pattern-reversal VEPs (in four subjects - eight eyes). These observations suggest that the magnocellular system/dorsal stream of the visual pathway (which is particularly activated in response to motion stimuli) may be more frequently affected in preterm children than the parvocellular system/ventral stream (tested mostly by the standard pattern-reversal VEPs). This pilot study may encourage further testing of the combined pattern and motion-related VEPs examinations in preterm children as a way of detecting hidden cortical/cerebral visual impairment (CVI).
- MeSH
- dítě MeSH
- financování organizované MeSH
- gestační stáří MeSH
- lidé MeSH
- nemoci centrálního nervového systému patofyziologie MeSH
- novorozenec nedonošený MeSH
- novorozenec s nízkou porodní hmotností MeSH
- novorozenec MeSH
- pilotní projekty MeSH
- předškolní dítě MeSH
- refrakce oka fyziologie MeSH
- zraková ostrost fyziologie MeSH
- zrakové dráhy patofyziologie MeSH
- zrakové evokované potenciály fyziologie MeSH
- zrakové korové centrum patofyziologie MeSH
- Check Tag
- dítě MeSH
- lidé MeSH
- novorozenec MeSH
- předškolní dítě MeSH
