scholarly journals The Topography of Visuospatial Attention as Revealed by a Novel Visual Field Mapping Technique

2009 ◽  
Vol 21 (7) ◽  
pp. 1447-1460 ◽  
Author(s):  
Julie A. Brefczynski-Lewis ◽  
Ritobrato Datta ◽  
James W. Lewis ◽  
Edgar A. DeYoe
Keyword(s):  
Visual Field ◽  
Visual Processing ◽  
Occipital Cortex ◽  
Cortical Activation ◽  
Neural Representation ◽  
Mapping Technique ◽  
Constant Area ◽  
Parietal Cortices ◽  
Visual Field Mapping ◽  
The Brain

Previously, we and others have shown that attention can enhance visual processing in a spatially specific manner that is retinotopically mapped in the occipital cortex. However, it is difficult to appreciate the functional significance of the spatial pattern of cortical activation just by examining the brain maps. In this study, we visualize the neural representation of the “spotlight” of attention using a back-projection of attention-related brain activation onto a diagram of the visual field. In the two main experiments, we examine the topography of attentional activation in the occipital and parietal cortices. In retinotopic areas, attentional enhancement is strongest at the locations of the attended target, but also spreads to nearby locations and even weakly to restricted locations in the opposite visual field. The dispersion of attentional effects around an attended site increases with the eccentricity of the target in a manner that roughly corresponds to a constant area of spread within the cortex. When averaged across multiple observers, these patterns appear consistent with a gradient model of spatial attention. However, individual observers exhibit complex variations that are unique but reproducible. Overall, these results suggest that the topography of visual attention for each individual is composed of a common theme plus a personal variation that may reflect their own unique “attentional style.”

Comparison of Human Occipital Cortical Activation to Lower and Upper Visual Field Stimuli

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 319-319
Author(s):  
K Portin ◽  
S Vanni ◽  
R Hari
Keyword(s):  
Visual Field ◽  
Visual Processing ◽  
Cortical Activation ◽  
Field Stimulation ◽  
Evoked Responses ◽  
Black Dot ◽  
Lower Field ◽  
Lower Quadrant ◽  
Upper Visual Field ◽  
Source Current

We compared cortical responses to lower and upper quadrant and full hemifield stimuli (90° and 180° sectors of circular checkerboards) measured from 15 healthy subjects with a Neuromag-122™ whole-scalp neuromagnetometer. The 0.2 s stimuli were presented once every second, while the subjects fixated a black dot in the centre of the screen. The first evoked responses, peaking at 70 ms in the contralateral hemisphere, were stronger for lower than for upper field stimulation (13/15 subjects, LVF; 11/15 RVF). The sources of the evoked responses, modelled as equivalent current dipoles, clustered around the calcarine fissure, with a trend for stronger sources after lower than after upper field stimulation (on average 12% LVF; 40% RVF; ns). Attention-related visual processing may be enhanced in the lower compared with the upper visual field (Rubin et al, 1996 Science271 651 – 653). Although our data showed a strong tendency to larger responses for lower than for upper visual field stimuli, this difference was not significant for source strengths, mainly because of different source depths for upper and lower field stimuli. However, the marked similarity of source current directions for full hemifield and lower quadrant stimuli (15° - 35° upwards from the horizontal axis, viewed from back, compared with directions 15° - 25° downwards for upper field stimuli) suggest that visual input from the lower field is preferred already at early stages of the human visual system.

A Neuromagnetic View of the Human Visual Brain

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 25-25
Author(s):  
S Vanni
Keyword(s):  
Visual Motion ◽  
Occipital Cortex ◽  
Task Demands ◽  
Cortical Activation ◽  
Visual Object ◽  
Source Regions ◽  
The Right ◽  
Visual Object Naming ◽  
The Brain ◽  
Good Agreement

A visual stimulus typically activates several cortical areas, both sequentially and overlapping in time. Characterisation of this temporal activation sequence has significantly improved with the recent development of whole-scalp neuromagnetometers. The magnetoencephalographic (MEG) signals mainly arise from time-locked cortical activity. Although the spatial localisation of several simultaneously active areas is ambiguous because of the non-uniqueness of the inverse problem, the comparison of estimated source regions across observers and utilisation of previous functional knowledge can usually resolve this ambiguity. Visual object naming, for example, generates cortical activation progressing bilaterally from occipital to temporal and frontal lobes. Simultaneously, the parieto-occipital alpha rhythm dampens as a function of task demands. Similarly, this rhythm is at a lower level after objects than non-objects in an object-detection task, which suggests that the parieto-occipital area is active when attending to visual form. In addition, this area generates evoked responses after voluntary blinks, saccades, and luminance increments, which in turn suggests that it participates in the updating of visual percepts. The sources of extrastriate MEG signals are generally in good agreement with the location of activation found with other imaging methods: visual motion activates the V5 in the ascending limb of the inferior temporal sulcus, faces the ventral temporo-occipital cortex, and objects the lateral occipital (LO) regions. Interestingly, the strength of the right LO activity closely follows the proportion of correctly detected objects. The future neuromagnetic studies will focus not only on functional localisation of the active areas, but also on how the brain processes various stimuli.

Connections and visual-field mapping in cat's tectoparabigeminal circuit

1979 ◽  
Vol 42 (6) ◽  
pp. 1656-1668 ◽  
Author(s):  
H. Sherk
Keyword(s):  
Visual Field ◽  
Visual Fields ◽  
Receptive Fields ◽  
Central Visual Field ◽  
Reciprocal Connections ◽  
Parabigeminal Nucleus ◽  
Visual Field Maps ◽  
Anterior Segments ◽  
Visual Field Mapping ◽  
The Brain

1. The aim of these experiments was to analyze the organization of the reciprocal connections between the cat's superior colliculus and parabigeminal nucleus. Both physiological and anatomical techniques were employed. 2. A population of cells in the superficial gray and upper optic layers of the colliculus was labeled retrogradely by horseradish peroxidase injections into the parabigeminal nucleus. No other sources of input to the nucleus were found in the brain stem or diencephalon. 3. A map of the visual field within the parabigeminal nucleus was reconstructed by plotting visual receptive fields at 350 parabigeminal sites with microelectrodes. The map resembled that found in the colliculus, although it was considerably less orderly. The entire contralateral visual field was represented and, in addition, roughly the central 40 degrees of the ipsilateral hemifield was included; futhermore, the expansion of the central visual field was similar to that of the tectal map. 4. The return parabigeminal projections to the caudal parts of the two colliculi, representing the contralateral hemifields, were in register with the tectal visual-field maps. In contrast, the parabigeminal pathways to the anterior segments of the two colliculi, representing part of the ipsilateral visual fields, were not clearly topographic. The projection to this part of the contralateral colliculus showed little order, while that to the ipsilateral colliculus was extremely sparse. 5. A single site in the colliculus can be the target of axons from nonhomologous locations in the two parabigeminal nuclei; so that both parabigeminal inputs are in register with the tectal map.

scholarly journals Cerebral Metabolic Relationships for Selected Brain Regions in Healthy Adults

1984 ◽  
Vol 4 (1) ◽  
pp. 1-7 ◽  
Author(s):  
E. Jeffrey Metter ◽  
Walter H. Riege ◽  
David E. Kuhl ◽  
Michael E. Phelps
Keyword(s):  
Visual Processing ◽  
Occipital Cortex ◽  
Brain Regions ◽  
Emission Tomography ◽  
Inferior Parietal Lobule ◽  
Cerebral Metabolic Rate ◽  
Positron Emission ◽  
Metabolic Systems ◽  
The Matrix ◽  
The Brain

The local cerebral metabolic rate for glucose was determined in 26 regions of the brain in 31 healthy subjects who underwent resting fluorodeoxyglucose positron emission tomography. Intercorrelations among the 26 regional measures were accepted as reliable at p < 0.01 (r > 0.45), uncorrected for the number of measures. From the matrix two apparently separate functional metabolic systems were identified: (1) a superior system involving the superior and middle frontal gyri, the inferior parietal lobule, and the occipital cortex; and (2) an inferior system involving the inferior frontal, Broca's, and posterior temporal regions. Evidence is presented to suggest that the superior system is involved in visual processing, memory recognition, and decision making, while the inferior system seems to at least participate in language-related functions.

scholarly journals Visual mapping on the brain - caveats for multifocal fMRI

2019 ◽  
Author(s):  
David P. Crewther ◽  
Shaun A. S. Seixas ◽  
Sheila G. Crewther
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Evoked Responses ◽  
Normal Vision ◽  
Visual Mapping ◽  
M Sequence ◽  
Cortical Magnification ◽  
Visual Field Mapping ◽  
The Brain ◽  
Correlational Model

AbstractWhile multifocal electroretinography has become a standard ophthalmological technique, its use in cortical neuroimaging has been lesser. Vanni et al. (2005) presented the first exploration of the multifocal visual mapping methodology with fMRI. This commentary confirms the utility of this method, but also presents empirical results which suggest caveats for the use of the technique. In the current study rapid multifocal fMRI was established using m-sequence pseudo-random binary stimuli applied to visual field mapping in six young adults with normal vision. Nine contiguous regions of visual field – two rings of 4 patches with a central patch, areas scaled for cortical magnification, were pseudo-randomly stimulated, with patterned or grey images. The decorrelation of stimulus patches allowed all 256 volumes to be used for the analysis of each of the nine stimulus areas. Strong localized activation was observed for each of the four peripheral regions with the location of the activation conforming to the expected visual field retinotopy. The inner regions, including the foveal patch, did not significantly activate. We propose, on the basis of a simple correlational model of simulated eye movements, that the loss of signal is due to gaze instability. Thus, while the rapid multifocal method can be successfully applied to fMRI, the results appear quite sensitive to eye movements, the effects of which may have been overlooked by smoothing evoked responses to achieve a retinotopic map.

Dynamic Domain Specificity In Human Ventral Temporal Cortex

2020 ◽  
Author(s):  
Brett B. Bankson ◽  
Matthew J. Boring ◽  
R. Mark Richardson ◽  
Avniel Singh Ghuman
Keyword(s):  
Visual Processing ◽  
Temporal Cortex ◽  
Processing System ◽  
Neural Representation ◽  
Domain Specificity ◽  
Individual Level ◽  
Ventral Temporal Cortex ◽  
Intracranial Recordings ◽  
Dynamic Domain ◽  
The Brain

ABSTRACTAn enduring neuroscientific debate concerns the extent to which neural representation is restricted to networks of patches specialized for particular domains of perceptual input (Kaniwsher et al., 1997; Livingstone et al., 2019), or distributed outside of these patches to broad areas of cortex as well (Haxby et al., 2001; Op de Beeck, 2008). A critical level for this debate is the localization of the neural representation of the identity of individual images, (Spiridon & Kanwisher, 2002) such as individual-level face or written word recognition. To address this debate, intracranial recordings from 489 electrodes throughout ventral temporal cortex across 17 human subjects were used to assess the spatiotemporal dynamics of individual word and face processing within and outside cortical patches strongly selective for these categories of visual information. Individual faces and words were first represented primarily only in strongly selective patches and then represented in both strongly and weakly selective areas approximately 170 milliseconds later. Strongly and weakly selective areas contributed non-redundant information to the representation of individual images. These results can reconcile previous results endorsing disparate poles of the domain specificity debate by highlighting the temporally segregated contributions of different functionally defined cortical areas to individual level representations. Taken together, this work supports a dynamic model of neural representation characterized by successive domain-specific and distributed processing stages.SIGNIFICANCE STATEMENTThe visual processing system performs dynamic computations to differentiate visually similar forms, such as identifying individual words and faces. Previous models have localized these computations to 1) circumscribed, specialized portions of the brain, or 2) more distributed aspects of the brain. The current work combines machine learning analyses with human intracranial recordings to determine the neurodynamics of individual face and word processing in and outside of brain regions selective for these visual categories. The results suggest that individuation involves computations that occur first in primarily highly selective parts of the visual processing system, then later recruits highly and non-highly selective regions. These results mediate between extant models of neural specialization by suggesting a dynamic domain specificity model of visual processing.

scholarly journals Effect of Methylphenidate on Resting-State Connectivity in Adolescents With a Disruptive Behavior Disorder: A Double-Blind Randomized Placebo-Controlled fMRI Study

2021 ◽  
Vol 12 ◽  
Author(s):  
Louise Pape ◽  
Koen van Lith ◽  
Dick Veltman ◽  
Moran Cohn ◽  
Reshmi Marhe ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Disruptive Behavior ◽  
Resting State ◽  
Visual Processing ◽  
Behavior Disorder ◽  
Occipital Cortex ◽  
Disruptive Behavior Disorder ◽  
Double Blind ◽  
Resting State Connectivity ◽  
The Brain

Some studies suggest that methylphenidate (MPH) might be an effective treatment for antisocial and aggressive behavior in adolescence. However, little is known about the mechanism of action of MPH in adolescents with this kind of psychopathology. MPH is a dopamine and norepinephrine reuptake inhibitor and thus it is likely to affect dopaminergic mesocorticolimbic pathways. This is the first study to investigate the effect of MPH on resting-state connectivity of three mesolimbic seed regions with the rest of the brain in clinical referred male adolescents with a disruptive behavior disorder (DBD). Thirty-six male DBD adolescents and 31 male healthy controls (HCs) were included. DBD subjects were randomly allocated to a single dose of MPH (DBD-MPH, n = 20) or placebo (DBD-PCB, n = 16). Seed-based resting-state functional connectivity of the nucleus accumbens (NAcc), amygdala, and ventral tegmental area (VTA) with the rest of the brain was compared between groups. The NAcc seed showed increased connectivity in DBD-PCB compared to HC with the occipital cortex, posterior cingulate cortex (PCC), precuneus, and inferior parietal lobule (IPL) and increased connectivity in DBD-PCB compared to DBD-MPH with occipital cortex, IPL, and medial frontal gyrus. The amygdala seed showed increased connectivity in DBD-PCB compared to HC with the precuneus and PCC. The VTA seed showed increased connectivity in the DBD-MPH compared to the DBD-PCB group with a cluster in the postcentral gyrus and a cluster in the supplementary motor cortex/superior frontal gyrus. Both NAcc and amygdala seeds showed no connectivity differences in the DBD-MPH compared to the HC group, indicating that MPH normalizes the increased functional connectivity of mesolimbic seed regions with areas involved in moral decision making, visual processing, and attention.

scholarly journals The brain dynamics of architectural affordances during transition

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zakaria Djebbara ◽  
Lars Brorson Fich ◽  
Klaus Gramann
Keyword(s):  
Occipital Cortex ◽  
The Body ◽  
Brain Dynamics ◽  
Alpha Band ◽  
Time Frequency ◽  
Posterior Cingulate ◽  
Sensory Signals ◽  
Event Related Desynchronization ◽  
The Brain ◽  
Attentional Mechanisms

AbstractAction is a medium of collecting sensory information about the environment, which in turn is shaped by architectural affordances. Affordances characterize the fit between the physical structure of the body and capacities for movement and interaction with the environment, thus relying on sensorimotor processes associated with exploring the surroundings. Central to sensorimotor brain dynamics, the attentional mechanisms directing the gating function of sensory signals share neuronal resources with motor-related processes necessary to inferring the external causes of sensory signals. Such a predictive coding approach suggests that sensorimotor dynamics are sensitive to architectural affordances that support or suppress specific kinds of actions for an individual. However, how architectural affordances relate to the attentional mechanisms underlying the gating function for sensory signals remains unknown. Here we demonstrate that event-related desynchronization of alpha-band oscillations in parieto-occipital and medio-temporal regions covary with the architectural affordances. Source-level time–frequency analysis of data recorded in a motor-priming Mobile Brain/Body Imaging experiment revealed strong event-related desynchronization of the alpha band to originate from the posterior cingulate complex, the parahippocampal region as well as the occipital cortex. Our results firstly contribute to the understanding of how the brain resolves architectural affordances relevant to behaviour. Second, our results indicate that the alpha-band originating from the occipital cortex and parahippocampal region covaries with the architectural affordances before participants interact with the environment, whereas during the interaction, the posterior cingulate cortex and motor areas dynamically reflect the affordable behaviour. We conclude that the sensorimotor dynamics reflect behaviour-relevant features in the designed environment.

scholarly journals Potential for imaging the high-affinity state of the 5-HT1B receptor: a comparison of three PET radioligands with differing intrinsic activity

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Anton Lindberg ◽  
Ryosuke Arakawa ◽  
Tsuyoshi Nogami ◽  
Sangram Nag ◽  
Magnus Schou ◽  
...  
Keyword(s):  
Pet Imaging ◽  
Specific Binding ◽  
Occipital Cortex ◽  
Intrinsic Activity ◽  
High Affinity ◽  
G Protein Coupled ◽  
Dose Dependent ◽  
The Brain ◽  
Agonist Affinity States ◽  
Different Doses

Abstract Background Over the last decade, a few radioligands have been developed for PET imaging of brain 5-HT1B receptors. The 5-HT1B receptor is a G-protein-coupled receptor (GPCR) that exists in two different agonist affinity states. An agonist ligand is expected to be more sensitive towards competition from another agonist, such as endogenous 5-HT, than an antagonist ligand. It is of interest to know whether the intrinsic activity of a PET radioligand for the 5-HT1B receptor impacts on its ability to detect changes in endogenous synaptic 5-HT density. Three high-affinity 11C-labeled 5-HT1B PET radioligands with differing intrinsic activity were applied to PET measurements in cynomolgus monkey to evaluate their sensitivity to be displaced within the brain by endogenous 5-HT. For these experiments, fenfluramine was pre-administered at two different doses (1.0 and 5.0 mg/kg, i.v.) to induce synaptic 5-HT release. Results A dose-dependent response to fenfluramine was detected for all three radioligands. At the highest dose of fenfluramine (5.0 mg/kg, i.v.), reductions in specific binding in the occipital cortex increased with radioligand agonist efficacy, reaching 61% for [11C]3. The most antagonistic radioligand showed the lowest reduction in specific binding. Conclusions Three 5-HT1B PET radioligands were identified with differing intrinsic activity that could be used in imaging high- and low-affinity states of 5-HT1B receptors using PET. From this limited study, radioligand sensitivity to endogenous 5-HT appears to depend on agonist efficacy. More extensive studies are required to substantiate this suggestion.

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