====== Three-dimensional perception ======

Three-dimensional perception refers to the [[cognitive]] [[ability]] to perceive and interpret visual stimuli in three [[dimension]]s, enabling individuals to understand the depth and spatial relationships of objects within their environment. This capability is crucial for navigation, object recognition, and interaction with the world. Here’s a closer look at the components and processes involved in three-dimensional perception:

Key Components of Three-Dimensional Perception
Depth Cues:

The brain uses various cues to infer depth and distance. These can be categorized into binocular and monocular cues:
Binocular Cues:
Binocular Disparity: The difference in images between the two eyes due to their horizontal separation. The brain processes these disparities to gauge the distance of objects.
Convergence: The inward movement of the eyes when focusing on a nearby object, providing information about how close the object is.
Monocular Cues:
Size: Familiar objects appear smaller as they are farther away, aiding in depth perception.
Interposition (Occlusion): When one object overlaps another, the overlapping object is perceived as closer.
Texture Gradient: The detail of a texture decreases with distance, helping to perceive depth.
Linear Perspective: Parallel lines appear to converge in the distance, indicating depth.
Motion Parallax: When moving, closer objects appear to move faster than those further away, providing depth information.
Visual Processing Regions:

Specific areas in the brain are involved in processing 3D visual information:
Primary Visual Cortex (V1): Responsible for initial processing of visual stimuli.
Middle Temporal Complex (hMT+): Involved in motion detection and 3D perception.
Parietal Cortex: Integrates sensory information and is crucial for spatial awareness and coordination.
Frontal Cortex: Engaged in higher-order processing and decision-making related to spatial information.
Integration of Sensory Information:

The brain combines visual input with information from other senses (like proprioception and vestibular input) to create a comprehensive understanding of 3D space. This multisensory integration is vital for accurate movement and interaction with the environment.
Importance of Three-Dimensional Perception
Navigation:

3D perception allows individuals to move through their environment effectively, avoiding obstacles and making spatial judgments.
Object Recognition:

Understanding the shape, size, and position of objects in three-dimensional space is crucial for tasks such as grasping and manipulating objects.
Social Interactions:

Accurate perception of others' positions and movements is essential for effective communication and social engagement.
Virtual Reality (VR) and Augmented Reality (AR):

3D perception is integral to creating immersive experiences in VR and AR, where users interact with virtual objects as if they were real.
Disorders Related to Three-Dimensional Perception
Akinetopsia:

A neurological condition characterized by an inability to perceive motion, leading to difficulties in understanding dynamic 3D scenes.
Depth Perception Deficits:

Conditions like strabismus (crossed eyes) can impair the ability to perceive depth due to misalignment of the eyes.
Spatial Neglect:

Often resulting from stroke, this condition involves neglecting one side of the visual field, affecting the perception of spatial relationships.
Research and Techniques
Research in three-dimensional perception often utilizes techniques such as:
Functional Magnetic Resonance Imaging (fMRI): To investigate brain activity associated with 3D perception tasks.
Electrophysiological Recordings: To study neural responses to 3D visual stimuli.
Virtual Environments: To assess how individuals perceive and interact with 3D space.
In summary, three-dimensional perception is a complex cognitive function that allows individuals to interpret spatial relationships and depth, facilitating effective navigation and interaction within their environment. It relies on a combination of depth cues, specific brain regions, and the integration of multisensory information.
----
The prevailing [[opinion]] emphasizes that the [[fronto-parietal network]] (FPN) is key in mediating general [[fluid intelligence]] (gF). Meanwhile, recent studies show that the human [[middle temporal complex]] (hMT+), located at the [[occipitotemporal]] border and involved in [[3D]] [[perception]] processing, also plays a key role in gF. However, the underlying mechanism is not clear, yet. To investigate this issue, a study targets [[visuospatial intelligence]], which is considered to have a high loading on gF. 
They use ultra-high field magnetic resonance spectroscopy (MRS) to measure GABA/Glu concentrations in hMT+ combining resting-state fMRI functional connectivity (FC), behavioral examinations including hMT+ perception suppression test and gF subtest in the visuospatial component. The findings show that both [[GABA]] in hMT+ and frontal-hMT+ [[functional connectivity]] significantly correlate with the performance of visuospatial intelligence. Further, the serial mediation model demonstrates that the effect of hMT+ GABA on visuospatial gF is fully mediated by the hMT+ frontal FC. Together the findings highlight the importance of integrating sensory and frontal cortices in mediating the visuospatial component of general [[fluid intelligence]]
((Gao Y, Cai YC, Liu DY, Yu J, Wang J, Li M, Xu B, Wang T, Chen G, Northoff G, Bai R, Song XM. GABAergic inhibition in human hMT+ predicts visuo-spatial intelligence mediated through the frontal cortex. Elife. 2024 Oct 1;13:RP97545. doi: 10.7554/eLife.97545. PMID: 39352734.))