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.

scholarly journals Longitudinal changes in brain activation during anticipation of monetary loss in bipolar disorder

2018 ◽  
Vol 49 (16) ◽  
pp. 2781-2788 ◽  
Author(s):  
Anna Manelis ◽  
Richelle Stiffler ◽  
Jeanette C. Lockovich ◽  
Jorge R. C. Almeida ◽  
Haris A. Aslam ◽  
...  
Keyword(s):  
Bipolar Disorder ◽  
Mood State ◽  
Brain Activation ◽  
Emotional Arousal ◽  
Occipital Cortex ◽  
Cortical Activation ◽  
Future Research ◽  
Longitudinal Changes ◽  
The Right ◽  
Cue Processing

AbstractBackgroundIndividuals with bipolar disorder (BD) show aberrant brain activation patterns during reward and loss anticipation. We examined for the first time longitudinal changes in brain activation during win and loss anticipation to identify trait markers of aberrant anticipatory processing in BD.MethodsThirty-four euthymic and depressed individuals with BD-I and 17 healthy controls (HC) were scanned using functional magnetic resonance imaging twice 6 months apart during a reward task.ResultsHC, but not individuals with BD, showed longitudinal reductions in the right lateral occipital cortex (RLOC) activation during processing of cues predicting possible money loss (p-corrected <0.05). This result was not affected by psychotropic medication, mood state or the changes in depression/mania severity between the two scans in BD. Elevated symptoms of subthreshold hypo/mania at baseline predicted more aberrant longitudinal patterns of RLOC activation explaining 12.5% of variance in individuals with BD.ConclusionsIncreased activation in occipital cortex during negative outcome anticipation may be related to elevated negative emotional arousal during anticipatory cue processing. One interpretation is that, unlike HC, individuals with BD were not able to learn at baseline that monetary losses were smaller than monetary gains and were not able to reduce emotional arousal for negative cues 6 months later. Future research in BD should examine how modulating occipital cortical activation affects learning from experience in individuals with BD.

Functional Magnetic Resonance Imaging of Visual Object Construction and Shape Discrimination: Relations among Task, Hemispheric Lateralization, and Gender

2001 ◽  
Vol 13 (1) ◽  
pp. 72-89 ◽  
Author(s):  
Apostolos P. Georgopoulos ◽  
Kenneth Whang ◽  
Maria-Alexandra Georgopoulos ◽  
Georgios A. Tagaris ◽  
Bagrat Amirikian ◽  
...  
Keyword(s):  
Cerebral Cortex ◽  
Left Hemisphere ◽  
Block Design ◽  
Blood Oxygenation ◽  
Hemispheric Lateralization ◽  
Visual Object ◽  
Anatomical Landmarks ◽  
Object Construction ◽  
The Right ◽  
The Brain

We studied the brain activation patterns in two visual image processing tasks requiring judgements on object construction (FIT task) or object sameness (SAME task). Eight right-handed healthy human subjects (four women and four men) performed the two tasks in a randomized block design while 5-mm, multislice functional images of the whole brain were acquired using a 4-tesla system using blood oxygenation dependent (BOLD) activation. Pairs of objects were picked randomly from a set of 25 oriented fragments of a square and presented to the subjects approximately every 5 sec. In the FIT task, subjects had to indicate, by pushing one of two buttons, whether the two fragments could match to form a perfect square, whereas in the SAME task they had to decide whether they were the same or not. In a control task, preceding and following each of the two tasks above, a single square was presented at the same rate and subjects pushed any of the two keys at random. Functional activation maps were constructed based on a combination of conservative criteria. The areas with activated pixels were identified using Talairach coordinates and anatomical landmarks, and the number of activated pixels was determined for each area. Altogether, 379 pixels were activated. The counts of activated pixels did not differ significantly between the two tasks or between the two genders. However, there were significantly more activated pixels in the left (n = 218) than the right side of the brain (n = 161). Of the 379 activated pixels, 371 were located in the cerebral cortex. The Talairach coordinates of these pixels were analyzed with respect to their overall distribution in the two tasks. These distributions differed significantly between the two tasks. With respect to individual dimensions, the two tasks differed significantly in the anterior-posterior and superior-inferior distributions but not in the left-right (including mediolateral, within the left or right side) distribution. Specifically, the FIT distribution was, overall, more anterior and inferior than that of the SAME task. A detailed analysis of the counts and spatial distributions of activated pixels was carried out for 15 brain areas (all in the cerebral cortex) in which a consistent activation (in ≥ 3 subjects) was observed (n = 323 activated pixels). We found the following. Except for the inferior temporal gyrus, which was activated exclusively in the FIT task, all other areas showed activation in both tasks but to different extents. Based on the extent of activation, areas fell within two distinct groups (FIT or SAME) depending on which pixel count (i.e., FIT or SAME) was greater. The FIT group consisted of the following areas, in decreasing FIT/SAME order (brackets indicate ties): GTi, GTs, GC, GFi, GFd, [GTm, GF], GO. The SAME group consisted of the following areas, in decreasing SAME/FIT order: GOi, LPs, Sca, GPrC, GPoC, [GFs, GFm]. These results indicate that there are distributed, graded, and partially overlapping patterns of activation during performance of the two tasks. We attribute these overlapping patterns of activation to the engagement of partially shared processes. Activated pixels clustered to three types of clusters: FIT-only (111 pixels), SAME-only (97 pixels), and FIT + SAME (115 pixels). Pixels contained in FIT-only and SAME-only clusters were distributed approximately equally between the left and right hemispheres, whereas pixels in the SAME + FIT clusters were located mostly in the left hemisphere. With respect to gender, the left-right distribution of activated pixels was very similar in women and men for the SAME-only and FIT + SAME clusters but differed for the FIT-only case in which there was a prominent left side preponderance for women, in contrast to a right side preponderance for men. We conclude that (a) cortical mechanisms common for processing visual object construction and discrimination involve mostly the left hemisphere, (b) cortical mechanisms specific for these tasks engage both hemispheres, and (c) in object construction only, men engage predominantly the right hemisphere whereas women show a left-hemisphere preponderance.

Visually Evoked Magnetic Field Induced by Ring Motion Aftereffect

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 301-301
Author(s):  
N Osaka ◽  
M Osaka ◽  
S Koyama ◽  
R Kakigi
Keyword(s):  
Magnetic Field ◽  
Goodness Of Fit ◽  
Visual Motion ◽  
Motion Aftereffect ◽  
Adaptation Period ◽  
Luminance Profile ◽  
The Subject ◽  
The Right ◽  
Clear Increase ◽  
Good Agreement

Motion aftereffect (MAE) is a negative aftereffect caused by prolonged viewing of visual motion: after gazing at a moving grating for a while, a stationary image will appear to move in the opposite direction (Ashida and Osaka, 1995 Vision Research35 1825). Evoked magnetic field (magnetoencephalogram: MEG) was measured when a human subject observing ring MAE in which concentric circles appear to contract continuously after viewing continuously expanding rings. The diameter of the stimulus was 20 deg with fixation point in the centre. The magnetic evoked field (80 averagings at a latency of 190 ms) was measured from 37 points over the occipital and parietal areas (Magnes SQUID biomagnetometer, BTi) while the subject was observing stationary rings after an adaptation period of 2 s at low spatial frequency (4 cycles deg−1, 4 Hz). The luminance profile was sinusoidally changed across rings. MRI image fitting (sagittal, coronal, and axial view) for each of four subjects, and dipole estimates obtained for equal magnetic field contours (with value of goodness of fit greater than 0.98) from the right brain hemisphere suggest that the main loci subserving MAE lie in the surrounding region over the lateral occipitotemporal areas in the human brain, close to area MT. This is in good agreement with another study with fMRI-based MAE measures [Tootell et al, 1995 Nature (London)375 139] in which a clear increase in activity in these areas was observed when subjects viewed MAE.

Brain olfactory activation measured by near-infrared spectroscopy in humans

2006 ◽  
Vol 120 (8) ◽  
pp. 638-643 ◽  
Author(s):  
H Harada ◽  
M Tanaka ◽  
T Kato
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Cortical Activation ◽  
Olfactory Stimulation ◽  
Olfactory Test ◽  
Olfactory Stimuli ◽  
Preliminary Study ◽  
The Right ◽  
The Brain

In recent years, near-infrared spectroscopy (NIRS) has been used to study functional activation of various areas of the brain. This is based on the assumption that an increase in the recorded oxygenated haemoglobin (HbO2) concentration represents an increase in blood flow, which in turn reflects neuronal activation. The aim of this preliminary study was to use NIRS to monitor the activity of the olfactory cortex, as mirrored by the haemodynamic response, when subjects were exposed to olfactory stimuli.A NIRO 300 (Hamamatsu Photonics, Hamamatsu, Japan) device was used. The optodes were placed on the right forehead and right temporal, parietal and occipital regions. Changes in the concentration of HbO2 and deoxygenated haemoglobin during olfactory stimulation were monitored. Olfactory stimulation was performed with vanilla essence, strawberry essence and scatol.During olfactory stimulation, cerebral HbO2 concentration increased over the frontal region. However, in the temporal, parietal and occipital regions, little or no HbO2 changes were recorded.This study shows that human brain cortical activation following olfactory stimulation can be recorded by NIRS. This NIRS analysis may therefore provide the basis for future development of an objective olfactory test in humans.

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.”

5HT2 Receptors in Cerebral Cortex of Migraineurs Studied Using PET and 18F-Fluorosetoperone

Cephalalgia ◽  
1995 ◽  
Vol 15 (2) ◽  
pp. 104-108 ◽  
Author(s):  
H Chabriat ◽  
A Tehindrazanarivelo ◽  
P Vera ◽  
Y Samson ◽  
S Pappata ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Occipital Cortex ◽  
Emission Tomography ◽  
Specific Distribution ◽  
Positron Emission ◽  
Migraine Pathogenesis ◽  
5Ht2 Receptors ◽  
The Right ◽  
The Brain

Since the brain 5HT2 receptors might be implicated in migraine pathogenesis, we have used positron emission tomography and 18F-fluorosetoperone, a 5HT2 specific radioligand, to investigate in vivo the cortical 5HT2 receptors in migraine subjects. Nine migraineurs who had either migraine with and without aura ( n = 5) or only migraine without aura ( n = 4) were studied between attacks. Twelve unmedicated healthy subjects of similar mean age were used as controls. Brain radioactivity was measured after 18F-setoperone IV injection for 90 min. A decrease of the regional specific distribution volumes (SDV) of the ligand was observed both in migraineurs and in controls. The age adjusted group means of SDV did not differ between patients and controls for the whole and for the right or left frontal, temporal, parietal and occipital cortex. These results suggest that cortical 5HT2 receptors may be unaltered between attacks in migraine sufferers.

scholarly journals Recruitment of occipital cortex by arithmetic processing follows computational bias in early blind

2018 ◽  
Author(s):  
Virginie Crollen ◽  
Latifa Lazzouni ◽  
Antoine Bellemare ◽  
Mohamed Rezk ◽  
Franco Lepore ◽  
...  
Keyword(s):  
Brain Activity ◽  
Occipital Cortex ◽  
Spatial Processing ◽  
Functional Flexibility ◽  
Multiplication Task ◽  
The Right ◽  
High Level ◽  
Blind Individuals ◽  
The Brain

AbstractArithmetic reasoning activates the occipital cortex of early blind people (EB). This activation of visual areas may reflect functional flexibility or the intrinsic computational role of specific occipital regions. We contrasted these competing hypotheses by characterizing the brain activity of EB and sighted participants while performing subtraction, multiplication and a control verbal task. In both groups, subtraction selectively activated a bilateral dorsal network commonly activated during spatial processing. Multiplication triggered more activity in temporal regions thought to participate in memory retrieval. No between-group difference was observed for the multiplication task whereas subtraction induced enhanced activity in the right dorsal occipital cortex of the blind individuals only. As this area overlaps and exhibits increased functional connectivity with regions showing selective tuning to auditory spatial processing, our results suggest that the recruitment of occipital regions during high-level cognition in the blind actually relates to the intrinsic computational role of the reorganized regions.

scholarly journals Dynamic Construction of Reduced Representations in the Brain for Perceptual Decision Behavior

2018 ◽  
Author(s):  
Jiayu Zhan ◽  
Robin A. A. Ince ◽  
Nicola van Rijsbergen ◽  
Philippe G. Schyns
Keyword(s):  
Occipital Cortex ◽  
Brain Regions ◽  
High Dimensional ◽  
Information Theoretic ◽  
Perceptual Decision ◽  
Layered Architecture ◽  
Feature Representations ◽  
The Right ◽  
Reduced Representations ◽  
The Brain

AbstractCurrent models propose that the brain uses a multi-layered architecture to reduce the high dimensional visual input to lower dimensional representations that support face, object and scene categorizations. However, understanding the brain mechanisms that support such information reduction for behavior remains challenging. We addressed the challenge using a novel information theoretic framework that quantifies the relationships between three key variables: single-trial information randomly sampled from an ambiguous scene, source-space MEG responses and perceptual decision behaviors. In each observer, behavioral analysis revealed the scene features that subtend their decisions. Independent source space analyses revealed the flow of these and other features in cortical activity. We show where (at the junction between occipital cortex and ventral regions), when (up until 170 ms post stimulus) and how (by separating task-relevant and irrelevant features) brain regions reduce the high-dimensional scene to construct task-relevant feature representations in the right fusiform gyrus that support decisions. Our results inform the occipito-temporal pathway mechanisms that reduce and select information to produce behavior.

Neuromagnetic Cortical Activation during Initiation of Optokinetic Nystagmus: An MEG Pilot Study

2015 ◽  
Vol 20 (3) ◽  
pp. 189-194
Author(s):  
Paulus S. Rommer ◽  
Roland Beisteiner ◽  
Kirsten Elwischger ◽  
Eduard Auff ◽  
Gerald Wiest
Keyword(s):  
Visual Motion ◽  
Optokinetic Nystagmus ◽  
Occipital Cortex ◽  
Cortical Activation ◽  
Slow Phase ◽  
Large Set ◽  
Optokinetic Stimulation ◽  
Imaging Studies ◽  
Visuomotor Integration ◽  
Cortical Areas

Purpose: To investigate the spatiotemporal evolution of cortical activation during the initiation of optokinetic nystagmus using magnetoencephalography. Background: Previous imaging studies of optokinetic nystagmus in humans using positron emission tomography and functional magnetic resonance imaging discovered activation of a large set of cortical and subcortical structures during steady-state optokinetic stimulation, but did not provide information on the temporal dynamics of the initial response. Imaging studies have shown that cortical areas responsible for vision in occipital and temporo-occipital areas are involved, i.e. cortical areas control optokinetic stimulation in humans. Magnetoencephalography provides measures that reflect neural ensemble activity in the millisecond time scale, allowing the identification of early cortical components of visuomotor integration. Design/Methods: We studied neuromagnetic cortical responses during the initiation of optokinetic nystagmus in 6 right-handed healthy subjects. Neuromagnetic activity was recorded with a whole-head magnetoencephalograph, consisting of 143 planar gradiometers. Results: The mean (±SD) latency between stimulus onset and initiation of optokinetic nystagmus was 177.7 ± 59 ms. Initiation of optokinetic nystagmus evoked an early component in the primary visual cortex starting at 40-90 ms prior to the onset of the slow phase of nystagmus. Almost simultaneously an overlapping second component occurred bilaterally in the temporo-occipital area (visual motion areas), pronounced in the right hemisphere, starting at 10-60 ms prior to the slow-phase onset. Both components showed long-duration activity lasting for up to 100 ms after slow-phase onset. Conclusions: Our findings suggest that the initiation of optokinetic nystagmus induces early cortical activation in the occipital cortex and almost simultaneously bilaterally in the temporo-occipital cortex. These cortical regions might represent essential areas for the monitoring of retinal slip.

The brain structure and neurosecretory cells of noctuid moth Anadevidia peponis: Noctuidae

1990 ◽  
Vol 48 (3) ◽  
pp. 436-437
Author(s):  
M. Sato ◽  
Y. Ogawa ◽  
M. Sasaki ◽  
T. Matsuo
Keyword(s):  
Biological Clock ◽  
Virgin Female ◽  
Basic Structure ◽  
Fixed Time ◽  
Neurosecretory Cells ◽  
Nerve Cells ◽  
Noctuid Moth ◽  
The Right ◽  
20 Nm ◽  
The Brain

A virgin female of the noctuid moth, a kind of noctuidae that eats cucumis, etc. performs calling at a fixed time of each day, depending on the length of a day. The photoreceptors that induce this calling are located around the neurosecretory cells (NSC) in the central portion of the protocerebrum. Besides, it is considered that the female’s biological clock is located also in the cerebral lobe. In order to elucidate the calling and the function of the biological clock, it is necessary to clarify the basic structure of the brain. The observation results of 12 or 30 day-old noctuid moths showed that their brains are basically composed of an outer and an inner portion-neural lamella (about 2.5 μm) of collagen fibril and perineurium cells. Furthermore, nerve cells surround the cerebral lobes, in which NSCs, mushroom bodies, and central nerve cells, etc. are observed. The NSCs are large-sized (20 to 30 μm dia.) cells, which are located in the pons intercerebralis of the head section and at the rear of the mushroom body (two each on the right and left). Furthermore, the cells were classified into two types: one having many free ribosoms 15 to 20 nm in dia. and the other having granules 150 to 350 nm in dia. (Fig. 1).

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