The dorsal and ventral visual streams have been considered to play distinct roles in visual processing for action: the dorsal stream is assumed to support real-time actions, while the ventral stream facilitates memory-guided actions. However, recent evidence suggests a more integrated function of these streams. We investigated the neural dynamics and functional connectivity between them during memory-guided actions using intracranial EEG. We tracked neural activity in the inferior parietal lobule in the dorsal stream, and the ventral temporal cortex in the ventral stream as well as the hippocampus during a delayed action task involving object identity and location memory. We found increased alpha power in both streams during the delay, indicating their role in maintaining spatial visual information. In addition, we recorded increased alpha power in the hippocampus during the delay, but only when both object identity and location needed to be remembered. We also recorded an increase in theta band phase synchronization between the inferior parietal lobule and ventral temporal cortex and between the inferior parietal lobule and hippocampus during the encoding and delay. Granger causality analysis indicated dynamic and frequency-specific directional interactions among the inferior parietal lobule, ventral temporal cortex, and hippocampus that varied across task phases. Our study provides unique electrophysiological evidence for close interactions between dorsal and ventral streams, supporting an integrated processing model in which both streams contribute to memory-guided actions.
Humans ; Male ; Female ; Adult ; Young Adult ; Hippocampus/physiology* ; Memory/physiology* ; Parietal Lobe/physiology* ; Temporal Lobe/physiology* ; Visual Perception/physiology* ; Electrocorticography ; Visual Pathways/physiology* ; Electroencephalography

The thalamic reticular nucleus (TRN) plays a crucial role in regulating sensory encoding, even at the earliest stages of visual processing, as evidenced by numerous studies. Orientation selectivity, a vital neural response, is essential for detecting objects through edge perception. Here, we demonstrate that somatostatin (SOM)-expressing and parvalbumin (PV)-expressing neurons in the TRN project to the dorsal lateral geniculate nucleus and modulate orientation selectivity and the capacity for visual information processing in the primary visual cortex (V1). These findings show that SOM-positive and PV-positive neurons in the TRN are powerful modulators of visual information encoding in V1, revealing a novel role for this thalamic nucleus in influencing visual processing.
Animals ; Somatostatin/metabolism* ; Parvalbumins/metabolism* ; Neurons/physiology* ; Thalamic Nuclei/physiology* ; Visual Pathways/physiology* ; Mice ; Mice, Inbred C57BL ; Visual Perception/physiology* ; Male ; Mice, Transgenic ; Visual Cortex/physiology* ; Primary Visual Cortex/cytology*

The looming stimulus-evoked flight response to approaching predators is a defensive behavior in most animals. However, how looming stimuli are detected in the retina and transmitted to the brain remains unclear. Here, we report that a group of GABAergic retinal ganglion cells (RGCs) projecting to the superior colliculus (SC) transmit looming signals from the retina to the brain, mediating the looming-evoked flight behavior by releasing GABA. GAD2-Cre and vGAT-Cre transgenic mice were used in combination with Cre-activated anterograde or retrograde tracer viruses to map the inputs to specific GABAergic RGC circuits. Optogenetic technology was used to assess the function of SC-projecting GABAergic RGCs (scpgRGCs) in the SC. FDIO-DTA (Flp-dependent Double-Floxed Inverted Open reading frame-Diphtheria toxin) combined with the FLP (Florfenicol, Lincomycin & Prednisolone) approach was used to ablate or silence scpgRGCs. In the mouse retina, GABAergic RGCs project to different brain areas, including the SC. ScpgRGCs are monosynaptically connected to parvalbumin-positive SC neurons known to be required for the looming-evoked flight response. Optogenetic activation of scpgRGCs triggers GABA-mediated inhibition in SC neurons. Ablation or silencing of scpgRGCs compromises looming-evoked flight responses without affecting image-forming functions. Our study reveals that scpgRGCs control the looming-evoked flight response by regulating SC neurons via GABA, providing novel insight into the regulation of innate defensive behaviors.
Animals ; Superior Colliculi/physiology* ; Retinal Ganglion Cells/physiology* ; GABAergic Neurons/physiology* ; Mice, Transgenic ; Mice ; Optogenetics ; Visual Pathways/physiology* ; Mice, Inbred C57BL ; Photic Stimulation/methods* ; gamma-Aminobutyric Acid/metabolism* ; Male

BACKGROUNDPrevious studies have demonstrated interhemispheric functional connectivity alterations in schizophrenia. However, the relationship between these alterations and the disease state of schizophrenia is largely unknown. Therefore, we aimed to investigate this relationship using voxel-mirrored homotopic connectivity (VMHC) method.

METHODSThis study enrolled 36 schizophrenia patients with complete remission, 58 schizophrenia patients with incomplete remission and 55 healthy controls. The VMHC was calculated based on resting-state functional magnetic resonance imaging data. Differences in VMHC among three groups were compared using one-way analysis of variance. A brain region with a significant difference in VMHC was defined as a region of interest (ROI), and the mean VMHC value in the ROI was extracted for the post hoc analysis, i.e., pair-wise comparisons across the three groups.

RESULTSVMHC in the visual region (inferior occipital and fusiform gyri) and the sensorimotor region (paracentral lobule) showed significant differences among the three groups (P < 0.05, a false discovery rate method corrected). Pair-wise comparisons in the post hoc analysis showed that VMHC of the visual and sensorimotor regions in schizophrenia patients with complete remission and incomplete remission was lower than that in healthy controls (P < 0.05, Bonferroni corrected); however, there was no significant difference between the two patient subgroups.

CONCLUSIONSInterhemispheric functional connectivity in the sensorimotor and visual processing pathways was reduced in patients with schizophrenia, but this reduction was unrelated to the disease state; thus, this reduction may serve as a trait marker of schizophrenia.

Adult ; Brain ; physiology ; Brain Mapping ; Female ; Humans ; Image Processing, Computer-Assisted ; Magnetic Resonance Imaging ; Male ; Schizophrenia ; physiopathology ; Sensorimotor Cortex ; physiology ; Visual Pathways ; physiology

Brain computer interface is a control system between brain and outside devices by transforming electroencephalogram (EEG) signal. The brain computer interface system does not depend on the normal output pathways, such as peripheral nerve and muscle tissue, so it can provide a new way of the communication control for paralysis or nerve muscle damaged disabled persons. Steady state visual evoked potential (SSVEP) is one of non-invasive EEG signals, and it has been widely used in research in recent years. SSVEP is a kind of rhythmic brain activity simulated by continuous visual stimuli. SSVEP frequency is composed of a fixed visual stimulation frequency and its harmonic frequencies. The two-dimensional ensemble empirical mode decomposition (2D-EEMD) is an improved algorithm of the classical empirical mode decomposition (EMD) algorithm which extended the decomposition to two-dimensional direction. 2D-EEMD has been widely used in ocean hurricane, nuclear magnetic resonance imaging (MRI), Lena image and other related image processing fields. The present study shown in this paper initiatively applies 2D-EEMD to SSVEP. The decomposition, the 2-D picture of intrinsic mode function (IMF), can show the SSVEP frequency clearly. The SSVEP IMFs which had filtered noise and artifacts were mapped into the head picture to reflect the time changing trend of brain responding visual stimuli, and to reflect responding intension based on different brain regions. The results showed that the occipital region had the strongest response. Finally, this study used short-time Fourier transform (STFT) to detect SSVEP frequency of the 2D-EEMD reconstructed signal, and the accuracy rate increased by 16%.
Algorithms ; Brain ; physiology ; Brain Mapping ; Brain-Computer Interfaces ; Electroencephalography ; Evoked Potentials, Visual ; Humans ; Neural Pathways

In vertebrate visual system, information is firstly processed in retina. With the development of the multi-electrode recording technique, concerted activity has been extensively observed in retinal ganglion cells of different species. However, the role of concerted activity in visual information processing is still unclear and under debating. This article reviews the recent studies focused on concerted activity among retinal ganglion cells, discussing the issues about its category, detection and physiological function.
Animals ; Cell Communication ; physiology ; Humans ; Photic Stimulation ; Retina ; physiology ; Retinal Ganglion Cells ; physiology ; Visual Pathways ; physiology ; Visual Perception ; physiology

Cortical visual prosthesis, optic nerve visual prosthesis and vision substitution devices are alternative ways for repairing the visual impairment in case of optic nerve injury, retina lose or blindness without fully developed central visual system. This article is a state-of-art review of the principles, technical details and the limitations of different types of prostheses beyond the retinal prosthesis.
Animals ; Artificial Intelligence ; Electric Stimulation Therapy ; instrumentation ; methods ; Humans ; Optic Nerve ; physiopathology ; Prosthesis Design ; Prosthesis Implantation ; methods ; trends ; Retinal Ganglion Cells ; physiology ; Vision Disorders ; rehabilitation ; Visual Cortex ; physiopathology ; Visual Pathways ; physiopathology

The retinotopic topography of area 17 in cats was measured by optical imaging based on intrinsic signals. When stimulated with two neighboring gratings oriented orthogonally each other, which were positioned respectively in the upper and lower visual fields, one piece of cortex that had the retinal projection corresponding to the area around the border of the two stimulus gratings became blurred in the resultant function orientation map, because the neurons in this site received excitatory signals from both the horizontal and the vertical gratings via indirect ways. This functional map of the same cortex was compared with that elicited only by a horizontal or vertical grating stimulation in the whole visual field. Accordingly, the accurate position of the retinotopic eccentricity of the cortex in visual field can be demarcated by calculating the cross correlation coefficient of the two functional maps. Furthermore, compared with the electrophysiological measure of receptive fields of single cortical neurons, the retinotopic eccentricities revealed by optical imaging were identical. This experiment provides a fast and relatively accurate method to calculate the retinotopic eccentricities in a large cortical area of the visual cortex.
Animals ; Brain Mapping ; methods ; Cats ; Evoked Potentials ; Retina ; physiology ; Tomography, Optical ; Vision, Ocular ; physiology ; Visual Cortex ; physiology ; Visual Pathways ; physiology ; Visual Perception ; physiology

This review summarizes objective assessment of visual function using visual electrophysiology. Objective assessment of visual acuity using pattern visual evoked potential (PVEP) and sweep pattern visual evoked potential (SPVEP), objective assessment of visual field using multifocal visual evoked potential (MVEP).
Electrophysiology ; Evoked Potentials, Visual ; Humans ; Photic Stimulation ; Vision Tests/methods* ; Vision, Ocular/physiology* ; Visual Acuity/physiology* ; Visual Field Tests ; Visual Pathways/physiology*