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Extrastriate cortex

The extrastriate cortex refers to the collection of visual processing areas in the brain located beyond the primary visual cortex (V1), primarily in the occipital lobe but extending into the parietal and temporal lobes, where it handles higher-level analysis of visual stimuli such as motion, color, form, and object identity.^[1] These regions receive inputs from V1 and are essential for transforming raw visual signals into meaningful perceptions that support recognition, navigation, and interaction with the environment.^[2] The extrastriate cortex is functionally organized into two parallel processing streams originating from early visual areas.^[1] The dorsal stream, often called the "where" or "how" pathway, extends toward the parietal lobe and specializes in spatial location, motion direction, and visuomotor coordination, with key areas like the middle temporal area (MT or V5) playing a central role in detecting and analyzing movement.^[3] In contrast, the ventral stream, known as the "what" pathway, projects to the temporal lobe and focuses on object identification, color discrimination, and form processing, involving regions such as V4 for color and shape selectivity and the inferotemporal cortex for complex object recognition.^[1] Early extrastriate areas, including V2 and V3, provide retinotopic maps of the visual field and process fundamental features like edges, orientations, and disparities, serving as bridges to more specialized functions.^[2] Lesions in these areas can produce profound deficits, such as cerebral achromatopsia (impaired color vision) from V4 damage or akinetopsia (motion blindness) from MT disruption, highlighting their specialized contributions to intact visual experience.^[1] Overall, the extrastriate cortex integrates sensory inputs with attentional and cognitive influences, forming a critical hub in the perception-cognition continuum that enables adaptive visual behavior.^[4]

Introduction

Definition and Location

The extrastriate cortex refers to the secondary and higher-order visual cortical areas that surround and extend beyond the primary visual cortex (V1, also known as the striate cortex), encompassing Brodmann areas 18 and 19 primarily within the occipital lobe.^[5] These areas form the initial stages of cortical visual processing beyond V1, receiving direct projections from it to support further elaboration of visual information.^[1] Anatomically, the extrastriate cortex is positioned posterior and lateral to V1, which is located along the calcarine sulcus on the medial surface of the occipital lobe, with extrastriate regions extending superiorly and laterally across the occipital lobe and into portions of the temporal and parietal lobes.^[5]^[1] The boundary between the striate (V1) and extrastriate cortex is defined by the striate-extrastriate transition zone, particularly at the occipital pole, where the prominent myelinated layer known as the line (or stria) of Gennari, characteristic of V1, abruptly disappears.^[6] This transition marks the shift from primary to secondary visual processing regions, with the calcarine sulcus serving as a key medial landmark delineating V1's extent.^[5] As part of the broader geniculostriate visual pathway, the extrastriate cortex receives its primary input from V1 via dense corticocortical connections, extending the relay of thalamic signals from the lateral geniculate nucleus through the optic radiations to V1 and onward.^[1]^[5] This positioning enables the extrastriate areas to integrate basic visual features processed in V1 for more complex analysis.^[1]

Historical Context

The term "extrastriate cortex" was coined by the German neurologist and anthropologist Korbinian Brodmann in his seminal 1909 work on comparative localization in the cerebral cortex, where he distinguished it from the striate cortex (Brodmann area 17) based on distinct cytoarchitectonic features, such as differences in laminar organization and cell density observed through Nissl staining.^[7] Brodmann identified areas 18 and 19 as comprising the extrastriate regions in the occipital lobe, laying the foundational anatomical framework for understanding visual processing beyond the primary visual area.^[2] In the mid-20th century, significant advancements came from the electrophysiological studies of David Hubel and Torsten Wiesel during the 1960s, who used single-unit recordings in cats and macaque monkeys to differentiate the primary visual cortex (V1) from surrounding higher-order visual areas, including extrastriate regions, by characterizing receptive field properties such as orientation selectivity and simple versus complex cell responses.^[8] Their work demonstrated a hierarchical organization in the visual cortex, with V1 processing basic features and extrastriate areas integrating more complex information, contributions that earned them the 1981 Nobel Prize in Physiology or Medicine shared with Roger Sperry. The 1970s and 1980s marked the identification of specialized functional subdivisions within the extrastriate cortex through targeted lesion and recording studies in primates. Jon Kaas and John Allman mapped the retinotopic organization of area MT (also known as V5) in 1971 in the middle temporal gyrus of owl monkeys, based on retinotopic mapping and direction-selective neuronal responses.^[9] Similarly, Semir Zeki identified area V4 in 1973 as predominantly responsive to color in rhesus monkeys, recording wavelength-selective cells in the prestriate cortex that supported its role in chromatic processing.^[10] Modern refinements in the understanding of extrastriate cortex emerged in the 1990s with the advent of noninvasive functional magnetic resonance imaging (fMRI), enabling the mapping of human homologues. Roger Tootell and colleagues in 1995 used fMRI to delineate areas V2 through V5 in humans, confirming retinotopic organization and selective responses to stimuli like motion in MT/V5, thus bridging primate electrophysiology with human neuroimaging data.^[11]

Anatomy

Gross Structure and Boundaries

The extrastriate cortex forms the predominant portion of the human visual cortex, occupying the majority of the occipital lobe and extending into the posterior temporal and parietal regions, thereby comprising approximately 20% of the total cerebral cortical surface area excluding the primary visual cortex (V1). Its irregular shape conforms to the folded architecture of surrounding gyri and sulci, enabling efficient packing within the constrained cranial space. This macroscopic organization allows for expansive representation of visual information beyond initial processing in V1.^[12] In terms of spatial extent, the extrastriate cortex spans the medial surface of the occipital lobe along the lingual and cuneus gyri, immediately adjacent to the calcarine sulcus that delineates V1. It extends laterally to encompass the fusiform gyrus and reaches the lateral occipitotemporal sulcus. Superiorly, it is delimited by the parieto-occipital sulcus, marking the transition to parietal lobe structures, while inferiorly it abuts the temporo-occipital junction, facilitating continuity with temporal lobe areas. These boundaries reflect its role in integrating visual inputs across multiple cortical surfaces.^[13]^[7]^[14] The primary vascular supply to the extrastriate cortex derives from branches of the posterior cerebral artery, particularly the calcarine and parieto-occipital arteries, which also nourish adjacent V1 via the calcarine branch. Input to the extrastriate cortex travels through the optic radiations, with dorsal components following a direct posterior course and ventral portions incorporating Meyer's loop, an anterior temporal extension that curves around the temporal horn of the lateral ventricle before projecting to inferior extrastriate regions. These white matter tracts ensure robust connectivity from thalamic relays to the cortical mantle.^[15]^[16]^[17]

Subdivisions and Cytoarchitecture

The extrastriate cortex encompasses several primary subdivisions beyond the primary visual cortex (V1), including area V2, V3, V4, and V5 (also known as MT), with additional higher-order areas such as V6 in the dorsal stream and inferotemporal (IT) regions in the ventral pathway.^[18] In nonhuman primates like macaques, these subdivisions are well-delineated, with V2 immediately adjacent to V1, V3 forming a concentric belt around V2 (divided into dorsal V3d and ventral V3v), V4 located anteriorly in the ventral occipital lobe, and V5 positioned in the superior temporal sulcus.^[19] Human extrastriate cortex exhibits analogous organization, with a comparable number of visual areas (approximately 25-30 in both humans and macaques), though the precise delineation in humans is often inferred through cytoarchitectonic and functional mapping.^[20]^[21] Cytoarchitectonic features distinguish these subdivisions from V1 and among themselves, primarily via Nissl staining and laminar organization. Brodmann area 18, corresponding largely to V2, features a thinner layer IV and broader layers II and III compared to V1's prominent sublayers IVa-IVc and dense granule cells; it also shows reduced myelination and larger pyramidal cells in layer V.^[22] Area 19, encompassing parts of V3, V4, and higher regions, displays more variable granular layer IV with less distinct lamination overall, including a conspicuous layer IIIc with large pyramidal cells in dorsal portions (hOc4d) and uniform cell density in others (hOc3d).^[20] V5/MT exhibits particularly dark cytochrome oxidase (CO) staining and higher cell packing density, reflecting its specialized architecture.^[19] Histological differences further highlight modular organization, especially in V2, which contains repeating CO stripes: thin stripes associated with color processing modules, pale stripes with form, and thick stripes with motion-disparity integration, contrasting V1's blob-interblob pattern.^[23] V3 demonstrates a concentric cytoarchitectonic layout surrounding V2, with dorsal and ventral segments showing subtle laminar asymmetries, such as sharper borders in dorsal V3d.^[18] Receptor architecture, including densities of GABA_A and M2 receptors, varies across layers and subdivisions, with V2 and V3 displaying more heterogeneous profiles than V1's uniform high GABA density.^[18] Species variations in extrastriate cytoarchitecture reflect evolutionary adaptations in visual processing. In primates, macaques show sharper laminar borders and higher interspecies cell volume density in V2 compared to hominoids, where human V2 and ventral posterior (VP) areas exhibit greater laminar complexity and receptor asymmetry between dorsal and ventral subdivisions.^[19] Humans have expanded visual map architectures similar to other primates but with proportionally larger areas like V3 and V4, aiding in refined cytoarchitectonic delineation via postmortem mapping.^[24] Seminal contributions include the 1925 atlas by Von Economo and Koskinas, which refined Brodmann's subdivisions by defining 107 human cortical areas through detailed Nissl-based cytoarchitectonics, identifying visual regions like OB (area 18/V2) with magnopyramidal features and OA (area 19) with peristriate granularity.^[25] Subsequent probabilistic mapping studies have built on this, confirming observer-independent borders for areas like hOc3d (V3d) using quantitative metrics from multiple brains.^[20]

Functional Organization

Ventral Stream Processing

The ventral stream, also known as the "what" pathway, is a hierarchical cortical network in the extrastriate cortex dedicated to processing visual features for object identification, form perception, and color analysis, originating from projections of the primary visual cortex (V1) through areas V2 and V3 to V4 and extending into the inferotemporal cortex (ITC).^[26] This pathway enables the recognition of objects regardless of their location or orientation in the visual field, contrasting with spatial and action-oriented processing in other streams.^[27] Key connections include feedforward inputs from V1's layer 4Cβ to V2's thin cytochrome oxidase stripes, which then project to V4, supporting progressive abstraction of visual features from basic edges to complex shapes.^[27] Area V4, located in the ventral occipitotemporal region, plays a central role in color and form processing within this stream, with neurons exhibiting selective responses to specific wavelengths organized into color columns that maintain retinotopic maps. These properties contribute to color constancy, allowing perception of stable hues under varying illumination, as well as shape-from-color cues where color boundaries aid in object segmentation.^[28] V4 receives inputs from V2's color-sensitive pale and thin stripes and projects forward to ITC areas, integrating color with form to support higher-level recognition.^[27] The koniocellular layers of the lateral geniculate nucleus (LGN), which convey blue-yellow color opponency and low-contrast signals, contribute to color signals in the ventral stream reaching V4. Additionally, general feedback from visual cortical areas including V4 to the LGN modulates early visual processing.^[29] Area V3, positioned between V2 and V4 in the ventral stream, serves an intermediate function in form processing, detecting boundaries and contours from oriented edges inherited from earlier areas.^[27] Neurons in V3 are sensitive to binocular disparity, facilitating the perception of depth and surface boundaries in three-dimensional forms, with disparity-tuned cells often preferring near disparities for object delineation.^[30] This area receives convergent inputs from V1 and V2, processing global form integration before relaying to V4 for further refinement.^[27] The inferotemporal cortex (ITC), the anterior terminus of the ventral stream, hosts specialized subregions for advanced object and category recognition, including the fusiform face area (FFA) in the lateral fusiform gyrus, which responds preferentially to faces over other stimuli.^[31] The FFA exhibits invariant responses to face identity across viewpoints and expressions, supporting rapid facial recognition essential for social cognition.^[31] Adjacent ITC areas handle other object classes, such as places in the parahippocampal place area, underscoring the stream's role in categorical visual expertise.^[27]

Dorsal Stream Processing

The dorsal stream, often referred to as the "where" or "how" pathway, processes spatial location, motion, and visuomotor guidance in the extrastriate cortex, originating from projections of primary visual cortex (V1) through areas V2 and V3 to specialized regions including V5/MT, V3A, and the posterior parietal cortex (PPC).^[26] This pathway supports functions such as object localization and action planning, contrasting with the ventral stream's focus on object identification. Key extrastriate nodes like V5/MT and V3A receive layered inputs that emphasize motion signals, enabling the integration of dynamic visual information for real-time behavioral responses. Area V5, also known as MT, exhibits strong directional selectivity for motion, with neurons tuned to specific directions and speeds of moving stimuli across large receptive fields. Seminal electrophysiological studies in awake behaving macaques by Movshon, Newsome, and colleagues in the 1980s revealed that MT neurons pool inputs from direction-selective cells in V1 to compute coherent global motion patterns, correlating closely with psychophysical discrimination thresholds for motion direction. For instance, these neurons demonstrate sensitivity to correlated random-dot motion, where increasing the proportion of dots moving in a consistent direction enhances firing rates, mirroring perceptual performance.^[32] This integration of speed and direction supports foundational motion analysis in the dorsal stream. V3A contributes to the processing of dynamic forms, particularly those defined by kinetic boundaries or motion contrasts, and modulates visual attention while aiding smooth pursuit eye movements. Functional imaging and physiological data indicate that V3A neurons respond robustly to motion-defined contours and exhibit enhanced activity during attentional shifts to moving targets, facilitating the tracking of objects in cluttered scenes.^[33] In relation to smooth pursuit, V3A provides early motion signals that initiate and stabilize eye tracking, with lesions or disruptions impairing pursuit initiation latency.^[34] The medial superior temporal area (MST), adjacent to MT, extends dorsal stream processing by analyzing complex optic flow fields for navigation and heading estimation. Neurons in the dorsal subdivision of MST (MSTd) are selectively tuned to radial expansion/contraction and rotational flow patterns simulating self-motion, as demonstrated in classic studies by Duffy and Wurtz. This enables the computation of heading direction from integrated visual cues during locomotion. The pathway's connectivity underscores its specialization: it draws parallel inputs predominantly from the magnocellular layers of the lateral geniculate nucleus (LGN), which convey transient, achromatic signals optimal for motion detection, relaying through V1's layer 4B. Outputs from MT and MST project to the superior colliculus, particularly its intermediate layers, to drive reflexive saccades toward salient moving targets.

Physiology

Neural Response Properties

Neurons in the extrastriate cortex display receptive field properties that are markedly larger and more complex compared to those in primary visual cortex (V1), reflecting a progression in visual processing hierarchy. In area V4, receptive fields typically measure 4-7 times larger than in V1, often encompassing 2-10 degrees of visual angle in the central visual field, and exhibit greater tolerance for stimulus position within the field. These fields frequently show end-stopped characteristics, where responses to elongated contours are suppressed beyond an optimal length, facilitating sensitivity to curved or bounded shapes such as object contours. In contrast, area MT neurons have receptive fields averaging around 5-15 degrees, with pronounced direction selectivity; the average direction tuning width is approximately 90 degrees, allowing robust encoding of motion trajectories despite variations in exact speed or orientation.^[35]^[36]^[37] Stimulus selectivity in extrastriate areas builds on V1 features but introduces higher-level invariances and specialized tunings. In V4, many neurons demonstrate color opponency, including red-green and blue-yellow double-opponent cells that respond maximally to specific hue contrasts while being inhibited by opponent colors, contributing to color constancy and boundary detection; approximately 54% of V4 neurons exhibit such opponent properties. Higher extrastriate regions, including parts of V4 and beyond, show increased orientation invariance, where responses remain stable across moderate shifts in stimulus orientation or position, unlike the sharp orientation tuning in V1. This selectivity extends to complex forms, with V4 cells often preferring specific contour configurations over simple bars or gratings.^[38]^[35] Temporal dynamics of neural responses vary across extrastriate areas, enabling rapid processing suited to their functional roles. In MT, onset latencies are relatively fast, ranging from 50-100 ms post-stimulus, supporting quick motion detection during dynamic scenes. V4 responses onset later, typically 80-150 ms, allowing integration of color, form, and spatial features before relaying to higher areas. These latencies were characterized through single-unit recordings in anesthetized or alert macaque monkeys, revealing sustained firing patterns that persist for 100-300 ms depending on stimulus duration and contrast. Plasticity in receptive field properties is evident in areas like V3A, where fields remap predictably during saccadic eye movements to maintain perceptual stability. Prior to a saccade, neurons in V3A begin responding to stimuli appearing in the future, postsaccadic receptive field location approximately 50-100 ms before eye movement onset, with remapping strength correlating to saccade amplitude. This predictive remapping, observed via single-unit electrophysiology in behaving macaques, minimizes disruptions in visual continuity across fixations. These properties have been primarily elucidated through single-unit electrophysiological recordings in nonhuman primates, such as awake or anesthetized macaques, using tungsten microelectrodes to isolate neuronal spikes while presenting controlled visual stimuli on tangent screens or monitors. Seminal studies, including those on V4 selectivity, employed quantitative tuning curves to map responses, confirming the transition from simple feature detection in V1 to invariant, object-relevant processing in extrastriate cortex.^[35]

Connectivity and Integration

The extrastriate cortex is characterized by a hierarchical network of intra-areal connections that support the progressive refinement of visual information. Feedforward projections originate from layer 4 of V1 and target layer 4 of V2, which in turn sends projections to layer 4 of V4, forming a ventral stream pathway for object recognition and form processing.^[27] These connections exhibit laminar specificity, with feedforward pathways terminating in middle layers and facilitating rapid transmission of basic features like orientation and color from lower to higher areas.^[39] In parallel, feedback loops from higher extrastriate areas, such as V4 to V2, originate primarily from layers 2/3 and 5/6, providing top-down modulation that enhances contextual influences on receptive fields in earlier stages.^[40] For instance, V4 feedback to V2 sharpens responses to complex contours by integrating global scene context, as demonstrated in primate tracing studies.^[41] Interconnections between the dorsal and ventral streams enable feature binding across modalities, such as combining motion from the dorsal pathway with color from the ventral pathway. Projections from area MT in the dorsal stream to V4 in the ventral stream support this cross-talk, allowing neurons in V4 to integrate motion signals with chromatic information for coherent object perception.^[42] These links are bidirectional, with ventral areas like V4 projecting back to MT to refine motion selectivity based on object identity, as evidenced by anatomical tracing in macaques. Such interactions prevent segregation artifacts, ensuring unified representations of dynamic colored objects.^[43] Extrinsic projections from the extrastriate cortex extend to higher cognitive regions, facilitating attentional and emotional processing. V4 sends projections to the prefrontal cortex (PFC) and posterior parietal cortex (PPC), forming reciprocal loops that modulate visual attention; for example, PFC inputs to V4 enhance spatial selectivity during selective attention tasks.^[44] Similarly, the inferior temporal cortex (ITC), a key extrastriate region, projects to the amygdala, conveying visual features with emotional valence to support rapid affective responses.^[45] These pathways are direct and monosynaptic, as confirmed by anterograde tracing in non-human primates.^[46] Subcortical inputs further integrate sensory and salience signals into extrastriate processing. The pulvinar nucleus provides dense projections to MT, bypassing V1 to convey salient or transient visual events, which aids in rapid motion detection and attentional orienting.^[47] These pulvinar-MT connections are myelinated for fast conduction and originate from the inferior pulvinar, as shown in tract-tracing experiments.^[48] Additionally, parvocellular layers of the lateral geniculate nucleus (LGN) project directly to V4, delivering high-resolution color and form signals that complement cortical inputs.^[49] This subcortical route supports fine-grained feature processing in V4 independent of primary visual input.^[50] These connectivity patterns underpin integration models like the two-streams hypothesis, which distinguishes dorsal (action-oriented) and ventral (perception-oriented) pathways originating from extrastriate divergences.^[51] Tract-tracing studies in primates reveal segregated yet interconnected projections, with V1 inputs splitting to MT (dorsal) and V4 (ventral), while cross-stream links ensure coordinated function.^[27] This architecture allows parallel processing with opportunities for synthesis, as supported by anatomical evidence from over 300 mapped connections.^[52]

Clinical Significance

Lesions and Visual Deficits

Lesions to the extrastriate cortex can produce specific visual deficits depending on the affected region, often resulting from vascular, traumatic, or degenerative causes. Damage to ventral stream areas, such as V4, leads to achromatopsia, a profound loss of color perception while preserving other visual functions like form and motion detection. A seminal case is patient HJA, who exhibited complete cerebral achromatopsia following bilateral lesions in the lingual and fusiform gyri, including area V4, rendering her unable to distinguish colors despite intact luminance-based vision. Similarly, lesions in the fusiform gyrus and inferior temporal cortex (ITC) cause prosopagnosia, impairing face recognition while sparing recognition of other objects. In HJA, concurrent damage to these ventral regions also produced prosopagnosia, highlighting the functional specialization of extrastriate areas for configural processing of faces. Dorsal stream lesions in the extrastriate cortex disrupt motion and spatial processing. Bilateral damage to area MT (V5) results in akinetopsia, a selective impairment in perceiving motion, where moving objects appear static or jumping discontinuously. Patient LM, following bilateral lesions from anoxic brain damage, exemplified this deficit, reporting that pouring tea appeared as frozen frames and traffic motion was imperceptible, severely limiting daily activities. In Balint's syndrome, involving bilateral parietal-extrastriate lesions, simultanagnosia prevents perception of multiple objects simultaneously, restricting attention to a single item at a time despite preserved fixation.^[53] Bilateral ventral stream lesions can cause visual form agnosia, dissociating "what" (object identification) from "how" (visuomotor guidance) processing. Patient DF, with damage to the lateral occipital complex, could not recognize shapes or orientations consciously but accurately grasped objects by scaling her hand posture, indicating intact dorsal stream function. Common etiologies include ischemic strokes in the posterior cerebral artery (PCA) territory, which supplies extrastriate areas and often spares primary visual cortex, leading to higher-order deficits like hemianopia with agnosia.^[54] Traumatic brain injury can produce similar focal damage, while degenerative diseases such as Alzheimer's pathology affect Brodmann areas 18 and 19, contributing to progressive visuospatial impairments.^[55] Insights into recovery come from blindsight phenomena in patients with primary visual cortex (V1) lesions, where subcortical pathways bypass V1 to activate extrastriate areas, enabling unconscious detection of stimuli in the blind field. This residual function, as studied in early cases by Weiskrantz and colleagues, suggests potential compensatory mechanisms involving direct projections from the lateral geniculate nucleus to motion-sensitive extrastriate regions like MT+.^[56]

Neuroimaging and Research Applications

Functional magnetic resonance imaging (fMRI) has been instrumental in mapping the retinotopic organization of extrastriate areas such as V2 through V5, utilizing phase-encoded stimuli to delineate visual field representations with high precision. This technique reveals the spatial layout of receptive fields in these regions, enabling researchers to identify boundaries and functional specializations non-invasively in humans. Diffusion tensor imaging (DTI) complements fMRI by assessing white matter connectivity, particularly the integrity of the optic radiation projecting to extrastriate cortex, which supports the structural basis for visual information relay. In research applications, fMRI and related methods have elucidated attentional mechanisms in extrastriate cortex, including biased competition models where top-down signals modulate V4 responses to resolve conflicts among multiple stimuli. Post-lesion plasticity studies employ transcranial magnetic stimulation (TMS) to probe reorganization in extrastriate areas, demonstrating how transient disruptions can reveal compensatory pathways in primate models of visual deficits. Optogenetics in animal models further dissects these dynamics, allowing targeted activation of specific neuronal populations to induce synaptic changes that mimic recovery processes in extrastriate circuits.^[57] For clinical diagnostics, positron emission tomography (PET) and single-photon emission computed tomography (SPECT) detect hypometabolism in extrastriate regions associated with achromatopsia, highlighting reduced activity in color-processing areas like V4 following vascular insults.^[58] Electroencephalography (EEG) measures motion-evoked potentials in the MT area, capturing early extrastriate responses to directional stimuli even in impaired vision, aiding in the assessment of residual function.^[59] Emerging research integrates extrastriate findings into artificial intelligence, where deep neural networks replicate hierarchical processing for object recognition, with intermediate layers analogous to V4 and IT responses in biological systems. Cross-species comparisons using ex vivo histology reveal cytoarchitectonic similarities and divergences between human and macaque extrastriate areas, informing evolutionary adaptations in visual processing.^[60] Studies from the 2010s and 2020s address gaps in subcortical-extrastriate pathways underlying blindsight, confirming preserved geniculo-extrastriate projections via advanced tractography in patients with V1 damage.^[61]

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In V1, compared with MT, direction-tuning bandwidths were narrower (mean = 68 degrees). Moreover, V1 responses to moving stimuli were weaker, and bidirectional ...Missing: width | Show results with:width
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Uniformity and Diversity of Structure and Function in ... - PubMed
By contrast, 54% of the cells in the V4 complex had opponent colour properties. 6. It is argued that despite its uniformity in cytoarchitectural appearance ...
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Segregation of feedforward and feedback projections in mouse ...
The anatomical hierarchy is based on the discovery of certain regularities that allow a given connection between any two cortical areas to be assigned a ...
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Notes on Visual Cortical Feedback and Feedforward Connections
Jan 28, 2022 · Thus, a strict comparison of cortical FFB and FBK connections is better addressed in extrastriate areas V2, V3, V4, MT, or TEO. Much of the ...
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A direct interareal feedback-to-feedforward circuit in primate visual ...
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Color signals through dorsal and ventral visual pathways - PMC
We will focus on two extrastriate regions, MT and V4/PIT (Figure 1). MT has traditionally been considered a motion area, with little involvement in color ...
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Interaction between dorsal and ventral processing streams
Aug 6, 2025 · Visual information is then processed through two interacting systems, the dorsal stream, from the visual cortex to the parietal and frontal ...
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Top-Down Control of Visual Attention by the Prefrontal Cortex ...
Anatomical and functional data support a role of PFC in modulating activity in extrastriate visual areas. The PFC is interconnected with several visual cortical ...Missing: loops | Show results with:loops
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The functional connectivity between amygdala and extrastriate ...
▷ Emotional modulation of the inferior temporal cortex (ITC) hardly habituates. ▷ Amygdala and ITC are correlated only during viewing novel emotional stimuli.
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The functional connectivity between amygdala and extrastriate ...
Aug 8, 2025 · Enhanced perceptual processing of emotional stimuli may be accomplished via amygdala-back-projections into the inferior temporal cortex.
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Functional Identification of a Pulvinar Path from Superior Colliculus ...
May 5, 2010 · We used physiological microstimulation to identify pulvinar neurons belonging to the path from SC to MT in the macaque. We made three salient observations.
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Evidence for adaptive myelination of subcortical shortcuts for visual ...
We found that PUL–MT connections are denser, but LGN–MT have greater myelination, suggesting faster signal transmission along these pathways.
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Mixed parvocellular and magnocellular geniculate signals in visual ...
Aug 27, 1992 · VISUAL information from the retina is transmitted to the cerebral cortex by way of the lateral geniculate nucleus (LGN) in the thalamus.
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(PDF) An investigation of collateral projections of the dorsal lateral ...
Aug 5, 2025 · Moreover, there are tinier projections from LGN to extrastriate visual areas including V2, V3, V4, in the inferotemporal cortex (Wong-Riley ...
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[PDF] Separate visual pathways for perception and action
We propose that the ventral stream of projections from the striate cortex to the inferotemporal cortex plays the major role in the perceptual identification of ...Missing: 1995 | Show results with:1995
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Interactions between dorsal and ventral streams for controlling ... - NIH
An influential theory divides the processing of visual information into two streams that follow different routes in the brain after the primary visual cortices.Missing: seminal | Show results with:seminal
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Post-Traumatic Balint's Syndrome: A Case Report and Review of the ...
Balint syndrome is caused by bilateral lesions of the parietal-occipital lobes, which affects the connection between the cortical regions of vision and motor ...
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Systematic evaluation of high-level visual deficits and lesions in ...
The posterior cerebral artery (PCA) supplies cortical areas in the occipital and ventral temporal lobes, regions involved in multi-level processing that leads ...
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Alzheimer's Disease Progressively Reduces Visual Functional ... - NIH
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Subcortical pathways to extrastriate visual cortex underlie residual ...
Residual vision, or blindsight, following damage to the primary visual cortex (V1) has been investigated for almost half a century.
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The phase of plasticity-induced neurochemical changes of high ...
Apr 7, 2023 · Posttraining transcranial magnetic stimulation of striate cortex disrupts consolidation early in visual skill learning. J. Neurosci. 32 ...Missing: extrastriate lesion
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Akinetopsia with achromatopsia due to focal epilepsy - ScienceDirect
Interictal single photon emission computed tomography (SPECT) revealed hyperperfusion in the right frontotemporal region and hypoperfusion in the bilateral ...
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Motion direction tuning in human visual cortex - Wiley Online Library
Jan 19, 2009 · Our data reveal differential extrastriate activation at 164–226 ms after motion onset that coded for motion direction with different ERP maps ...<|separator|>
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Receptor architecture of macaque and human early visual areas
Dec 20, 2021 · Aim of the present study is to characterize transmitter expression in the primary visual cortex and in early extrastriate visual areas of the ...
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Human blindsight is mediated by an intact geniculo-extrastriate ...
Oct 20, 2015 · We show that blindsight may be facilitated by an intact white-matter pathway between the lateral geniculate nucleus and motion area hMT+.