scholarly journals Metabolic Activity Patterns in the Monkey Visual Cortex as Revealed by Spectral Analysis

1999 ◽  
Vol 19 (4) ◽  
pp. 401-416 ◽  
Author(s):  
Yannis Dalezios ◽  
Georgia G. Gregoriou ◽  
Helen E. Savaki
Keyword(s):  
Spectral Analysis ◽  
Visual Cortex ◽  
Metabolic Activity ◽  
Activity Patterns ◽  
Spatial Arrangement ◽  
Spectral Amplitude ◽  
Two Dimensional ◽  
Reaching Task ◽  
Area V2 ◽  
Monkey Visual Cortex

The metabolic activity pattern of the monkey visual cortex was mapped quantitatively with [14C]-2-deoxyglucose during the performance of a visually guided reaching task. After bandpass filtering of the reconstructed two-dimensional metabolic maps of areas V1 and V2, alternating bands of high and low metabolic activity were apparent in control and experimental hemispheres. The spatial arrangement of active bands was studied with two-dimensional spectral analysis, and bands were found to be more organized in the experimental monkey. In area V1 of the control monkey the spectral amplitude was spread over a wider range of directions and frequencies than in the experimental subject. The finding that layer IV is characterized by more complex spectra than layers I through III suggests the coexistence of more than one active columnar system in the geniculorecipient layer. In area V2, stripes running almost perpendicular to the V1/V2 border were found along with superimposed patches of enhanced metabolic activity. In the experimental hemispheres, the corresponding spectra were extremely sharp yielding a constant periodicity. It is suggested that the well-organized columnar arrangement within areas V1 and V2 of the experimental hemispheres emerges from the diffusely organized background network of activity patterns in the control state.

scholarly journals Transformation from independent to integrative coding of multi-object arrangements in human visual cortex

2017 ◽  
Author(s):  
Daniel Kaiser ◽  
Marius V. Peelen
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Activity Patterns ◽  
Spatial Arrangement ◽  
Living Room ◽  
Natural Scenes ◽  
Response Patterns ◽  
Object Representations ◽  
Individual Object ◽  
Object Coding

AbstractTo optimize processing, the human visual system utilizes regularities present in naturalistic visual input. One of these regularities is the relative position of objects in a scene (e.g., a sofa in front of a television), with behavioral research showing that regularly positioned objects are easier to perceive and to remember. Here we use fMRI to test how positional regularities are encoded in the visual system. Participants viewed pairs of objects that formed minimalistic two-object scenes (e.g., a “living room” consisting of a sofa and television) presented in their regularly experienced spatial arrangement or in an irregular arrangement (with interchanged positions). Additionally, single objects were presented centrally and in isolation. Multi-voxel activity patterns evoked by the object pairs were modeled as the average of the response patterns evoked by the two single objects forming the pair. In two experiments, this approximation in object-selective cortex was significantly less accurate for the regularly than the irregularly positioned pairs, indicating integration of individual object representations. More detailed analysis revealed a transition from independent to integrative coding along the posterior-anterior axis of the visual cortex, with the independent component (but not the integrative component) being almost perfectly predicted by object selectivity across the visual hierarchy. These results reveal a transitional stage between individual object and multi-object coding in visual cortex, providing a possible neural correlate of efficient processing of regularly positioned objects in natural scenes.

Development of metabolic activity patterns in the somatosensory cortex of cats

1993 ◽  
Vol 70 (5) ◽  
pp. 2117-2127 ◽  
Author(s):  
S. L. Juliano ◽  
R. A. Code ◽  
M. Tommerdahl ◽  
D. E. Eslin
Keyword(s):  
Somatosensory Cortex ◽  
Metabolic Activity ◽  
Activity Patterns ◽  
Vertical Displacement ◽  
Two Dimensional ◽  
Small Spot ◽  
Cortical Responses ◽  
Different Ages ◽  
Evoked Activity ◽  
The Individual

1. The development of cortical responses to somatic stimulation was studied in kittens 2-5 wk of age using the 2-deoxyglucose (2DG) technique. During the 2DG experiment each kitten received an innocuous intermittent vertical displacement stimulus to the forepaw. 2. The pattern of metabolic activity was substantially different in young animals compared with adults. In the individual autoradiographs of the 2-wk-old kittens stimulus-evoked 2DG uptake in primary somatosensory cortex was localized to a small spot in the upper portion of the cortex, whereas in the adult the label extended vertically through the cortical layers and appeared more column-like. Individual patches of label were substantially smaller and less dense in young animals. Over a period of several weeks the evoked activity evolved to the more extensive adult pattern. The 2DG uptake displayed a mature distribution by approximately 4-5 wk of age. During this period, the cortical architecture also evolved from an immature to a mature arrangement. 3. The evoked activity was reconstructed into two-dimensional maps; the distribution of label > or = 1.5 SD above background was considered to be stimulus related. In the adult, the pattern appeared as a strip or strips of increased metabolic activity that extended in the rostrocaudal direction for approximately 1 mm. In contrast, the activity pattern in animals 2-4 wk old was less discretely organized into "strips" and was more diffusely spread over several mms of somatosensory cortex. The two-dimensional pattern gradually coalesced into a more localized strip by approximately 4-5 wk of age. Although the pattern of label was more widespread in the young animals, the absolute distance of the spread of activity did not vary substantially, regardless of the age of the animal. 4. Other measurements regarding the distribution of activity at different ages indicate that the amount of cortex activated increases in absolute terms, although the percent of cortex activated by the stimulus decreases. The overall intensity of the 2DG uptake as measured on the two-dimensional maps increases with age, as does the variability of the 2DG uptake; a wider range of intensity values is seen in the adult. Plots created from the individual two-dimensional reconstructions allowed a measure of "patch strength" at different ages. These histograms relate the most intense region of uptake in a given map to the spatial distribution of activity spreading in the medial and lateral directions.(ABSTRACT TRUNCATED AT 400 WORDS)

Is there a high concentration of color-selective cells in area V4 of monkey visual cortex?

1982 ◽  
Vol 47 (2) ◽  
pp. 193-213 ◽  
Author(s):  
S. J. Schein ◽  
R. T. Marrocco ◽  
F. M. de Monasterio
Keyword(s):  
Visual Cortex ◽  
Central Field ◽  
High Concentration ◽  
Field Representation ◽  
Area V4 ◽  
Area V2 ◽  
Sufficient Detail ◽  
Prelunate Gyrus ◽  
Color Selectivity ◽  
Monkey Visual Cortex

1. Recordings were made from neurons located within the central-field representation of the V4 area of extrastriate visual cortex using a semichronic, nitrous-oxide preparation; the properties of 174 cells were examined in sufficient detail to permit their classification. Cyto- and myeloarchitectural studies confirmed the identification of the area. 2. Color-selective cells with either color-biased or color-opponent properties represented about 20% of the examined population. Their incidence was not significantly different from that of similar cells encountered in penetrations into the central-field representation of area V2. 3. Most color-selective cells had color-biased properties, responding best to wave-lengths shorter than 460 nm, or longer than 580 n, or both. No examples of "green-biased" cells were found. Some color-biased cells responded to photopically matched white light, while others did not. Very few cells showed overt color-opponent responses. The spectral sensitivity of color-selective cells was not unusually narrow. 4. Cells lacking color selectivity and responding equally well to chromatic and achromatic lights of equal photopic luminosity, were the most commonly encountered cell type in penetrations of different parts of the V4 area (56%). Other than color, these cells showed stimulus preferences like those of color-selective cells. 5. One-fourth of V4 cells could not be systematically driven with the various stimuli used. This finding is consistent with recent results of recordings from the prelunate gyrus of the behaving monkey suggesting that some V4 cells receive extraretinal signals. 6. Our results do not support recent claims that V4 is specialized in the detailed analysis of color information.

scholarly journals “Real-time” obstacle avoidance in the absence of primary visual cortex

2009 ◽  
Vol 106 (37) ◽  
pp. 15996-16001 ◽  
Author(s):  
Christopher L. Striemer ◽  
Craig S. Chapman ◽  
Melvyn A. Goodale
Keyword(s):  
Visual Cortex ◽  
Real Time ◽  
Obstacle Avoidance ◽  
Primary Visual Cortex ◽  
Posterior Parietal Cortex ◽  
Dorsal Stream ◽  
Visual Pathways ◽  
Visual Stream ◽  
Reaching Task ◽  
Visual Inputs

When we reach toward objects, we easily avoid potential obstacles located in the workspace. Previous studies suggest that obstacle avoidance relies on mechanisms in the dorsal visual stream in the posterior parietal cortex. One fundamental question that remains unanswered is where the visual inputs to these dorsal-stream mechanisms are coming from. Here, we provide compelling evidence that these mechanisms can operate in “real-time” without direct input from primary visual cortex (V1). In our first experiment, we used a reaching task to demonstrate that an individual with a dense left visual field hemianopia after damage to V1 remained strikingly sensitive to the position of unseen static obstacles placed in his blind field. Importantly, in a second experiment, we showed that his sensitivity to the same obstacles in his blind field was abolished when a short 2-s delay (without vision) was introduced before reach onset. These findings have far-reaching implications, not only for our understanding of the time constraints under which different visual pathways operate, but also in relation to how these seemingly “primitive” subcortical visual pathways can control complex everyday behavior without recourse to conscious vision.

scholarly journals Myelin densities in retinotopically defined dorsal visual areas of the macaque

2021 ◽  
Author(s):  
Xiaolian Li ◽  
Qi Zhu ◽  
Wim Vanduffel
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Cortical Thickness ◽  
New World Monkeys ◽  
Isotropic Resolution ◽  
Density Mapping ◽  
Area V2 ◽  
Visual Areas ◽  
Density Results

AbstractThe visuotopic organization of dorsal visual cortex rostral to area V2 in primates has been a longstanding source of controversy. Using sub-millimeter phase-encoded retinotopic fMRI mapping, we recently provided evidence for a surprisingly similar visuotopic organization in dorsal visual cortex of macaques compared to previously published maps in New world monkeys (Zhu and Vanduffel, Proc Natl Acad Sci USA 116:2306–2311, 2019). Although individual quadrant representations could be robustly delineated in that study, their grouping into hemifield representations remains a major challenge. Here, we combined in-vivo high-resolution myelin density mapping based on MR imaging (400 µm isotropic resolution) with fine-grained retinotopic fMRI to quantitatively compare myelin densities across retinotopically defined visual areas in macaques. Complementing previously documented differences in populational receptive-field (pRF) size and visual field signs, myelin densities of both quadrants of the dorsolateral posterior area (DLP) and area V3A are significantly different compared to dorsal and ventral area V3. Moreover, no differences in myelin density were observed between the two matching quadrants belonging to areas DLP, V3A, V1, V2 and V4, respectively. This was not the case, however, for the dorsal and ventral quadrants of area V3, which showed significant differences in MR-defined myelin densities, corroborating evidence of previous myelin staining studies. Interestingly, the pRF sizes and visual field signs of both quadrant representations in V3 are not different. Although myelin density correlates with curvature and anticorrelates with cortical thickness when measured across the entire cortex, exactly as in humans, the myelin density results in the visual areas cannot be explained by variability in cortical thickness and curvature between these areas. The present myelin density results largely support our previous model to group the two quadrants of DLP and V3A, rather than grouping DLP- with V3v into a single area VLP, or V3d with V3A+ into DM.

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