Preperation Lecture 5
Postma (2016) Neuropsychology of Space. Chapter 2
Part 1. Visuospatial perception
- Sensation -> refers to the process of sensing the environment through touch, taste, sight, sound,
and smell. This information is sent to the brain where perception comes into play.
- Perception -> the way humans select, organize, and interpret these sensations and therefore make
sense of everything around them.
- Visual perception -> the ability to interpret the surrounding environment by processing the
information that is contained in visible light.
- Visuospatial perception -> the ability to process and interpret visual information about where
objects are in space.
- Visuospatial processing -> encompasses a wide variety of neurocognitive operations raging form
that basic ability to analyze how parts or features of an object combine to form an organized
whole, to the dynamic and interactive spatial processes required to track moving object, to
visualize displacement, and to localize, attend, or reach for objects or visual targets in a spatial
array.
2.1 Seeing 3D from 2D images
Seeing starts when the cornea and then the lens focuses an image onto a light-sensitive membrane in
the back of the eye, the retina. The retina is part of the brain that is isolated to serve as a transducer for
the conversion of patterns of light into neuronal signals. Humans perceive the world in three
dimensions because of depth cues.
- Depth cues -> can be monocular, based on the input of one eye, and binocular, based on cues that
reflect the images from both eyes. Depth perception allows the perception of the distance between
elements in an environment and a conception of the length, width, and height of an object.
- Perceptual work -> demonstrated that human observers make judgements about size, shape, and
orientation by integrating visual cues in close to a statically optimal way. They rely more on
whatever cues are most reliable in a given stimulus.
2.2 The visual pathway from retina to cortex
Visual system -> visual information passes through the lateral geniculate nucleus (LGN) and the striate
cortex of the occipital lobe. The vast majority of optic tract fibers terminate on neurons in the LGN.
Each LGN neuron responds to stimulation of one eye only. The axons terminate in different layers or
sublayers of the primary visual cortex.
- Primary visual cortex/striate cortex (V1) -> because of the unique layers also known as the striate
cortex. It is involved in the initial cortical processing of all visual information necessary for visual
perception. It sends input to extrastriate cortex, the prestriate cortex, and to the visual association
cortex.
- Prestriate cortex (V2) -> receives strong feedforward connection form V1 and sends strong
connections to the extrastriate cortex.
- Extrastriate cortex -> includes all of the occipital areas surrounding the primary visual cortex
(V3, V4, V5/MT).
1
, - The visual association cortex -> extends anteriorly from the extrastriate cortex to encompass
adjacent areas of the posterior parietal lobe and much of the posterior temporal lobe. In most
cases, these areas receive visual input via the extrastriate cortex, which sends color, shape/form,
location, and motion information to different areas of the visual association cortex.
There are two broad streams of visual projections from area V1 and other early visual areas:
1. Ventral stream -> begins at the retina and projects via the LGN of the thalamus to the primary
visual cortex. the pathway proceeds to prestriate and extrastriate visual areas V2 and V4, and then
projects ventrally to the posterior (PIT) and anterior (AIT) regions of the inferior temporal lobe.
Input to the ventral pathway is derived principally, though not exclusively, from the parvocellular
layers of the LGN. Parvocellular input to V1 organizes into distinct areas called the blob and
interblobs regions. At a functional level the ventral stream processes information about visual
properties of objects and patterns.
2. Dorsal stream -> begins at the retina and projects via the LGN to area V1. The pathway proceeds
toV2 and V3, then projects dorsally to the medial (MT/V5) and medial superior (MST) regions of
the temporal lobe, and then to the ventral inferior parietal (IP) lobe. Input to the dorsal pathway
is derived principally, though not exclusively, from the magnocellular layers of LGN and then to
layer 4C alpha of V1. Cells in this pathway are maximally sensitive to movement and direction
and are less responsive to color or form. At a functional level, the dorsal stream is essentially
involved in spatial localization tasks, spatial attention and mental rotation. Furthermore, the
pathway is also involved in the integration of visual and motor functions.
There are three principal projection pathways from the parietal lobe.
1. Parietal-prefrontal pathways -> formed by the subregions LIP, VIP, MT, and MST; strongly
involved in the initiation and control of eye movements and crucial for spatial working memory.
2
Postma (2016) Neuropsychology of Space. Chapter 2
Part 1. Visuospatial perception
- Sensation -> refers to the process of sensing the environment through touch, taste, sight, sound,
and smell. This information is sent to the brain where perception comes into play.
- Perception -> the way humans select, organize, and interpret these sensations and therefore make
sense of everything around them.
- Visual perception -> the ability to interpret the surrounding environment by processing the
information that is contained in visible light.
- Visuospatial perception -> the ability to process and interpret visual information about where
objects are in space.
- Visuospatial processing -> encompasses a wide variety of neurocognitive operations raging form
that basic ability to analyze how parts or features of an object combine to form an organized
whole, to the dynamic and interactive spatial processes required to track moving object, to
visualize displacement, and to localize, attend, or reach for objects or visual targets in a spatial
array.
2.1 Seeing 3D from 2D images
Seeing starts when the cornea and then the lens focuses an image onto a light-sensitive membrane in
the back of the eye, the retina. The retina is part of the brain that is isolated to serve as a transducer for
the conversion of patterns of light into neuronal signals. Humans perceive the world in three
dimensions because of depth cues.
- Depth cues -> can be monocular, based on the input of one eye, and binocular, based on cues that
reflect the images from both eyes. Depth perception allows the perception of the distance between
elements in an environment and a conception of the length, width, and height of an object.
- Perceptual work -> demonstrated that human observers make judgements about size, shape, and
orientation by integrating visual cues in close to a statically optimal way. They rely more on
whatever cues are most reliable in a given stimulus.
2.2 The visual pathway from retina to cortex
Visual system -> visual information passes through the lateral geniculate nucleus (LGN) and the striate
cortex of the occipital lobe. The vast majority of optic tract fibers terminate on neurons in the LGN.
Each LGN neuron responds to stimulation of one eye only. The axons terminate in different layers or
sublayers of the primary visual cortex.
- Primary visual cortex/striate cortex (V1) -> because of the unique layers also known as the striate
cortex. It is involved in the initial cortical processing of all visual information necessary for visual
perception. It sends input to extrastriate cortex, the prestriate cortex, and to the visual association
cortex.
- Prestriate cortex (V2) -> receives strong feedforward connection form V1 and sends strong
connections to the extrastriate cortex.
- Extrastriate cortex -> includes all of the occipital areas surrounding the primary visual cortex
(V3, V4, V5/MT).
1
, - The visual association cortex -> extends anteriorly from the extrastriate cortex to encompass
adjacent areas of the posterior parietal lobe and much of the posterior temporal lobe. In most
cases, these areas receive visual input via the extrastriate cortex, which sends color, shape/form,
location, and motion information to different areas of the visual association cortex.
There are two broad streams of visual projections from area V1 and other early visual areas:
1. Ventral stream -> begins at the retina and projects via the LGN of the thalamus to the primary
visual cortex. the pathway proceeds to prestriate and extrastriate visual areas V2 and V4, and then
projects ventrally to the posterior (PIT) and anterior (AIT) regions of the inferior temporal lobe.
Input to the ventral pathway is derived principally, though not exclusively, from the parvocellular
layers of the LGN. Parvocellular input to V1 organizes into distinct areas called the blob and
interblobs regions. At a functional level the ventral stream processes information about visual
properties of objects and patterns.
2. Dorsal stream -> begins at the retina and projects via the LGN to area V1. The pathway proceeds
toV2 and V3, then projects dorsally to the medial (MT/V5) and medial superior (MST) regions of
the temporal lobe, and then to the ventral inferior parietal (IP) lobe. Input to the dorsal pathway
is derived principally, though not exclusively, from the magnocellular layers of LGN and then to
layer 4C alpha of V1. Cells in this pathway are maximally sensitive to movement and direction
and are less responsive to color or form. At a functional level, the dorsal stream is essentially
involved in spatial localization tasks, spatial attention and mental rotation. Furthermore, the
pathway is also involved in the integration of visual and motor functions.
There are three principal projection pathways from the parietal lobe.
1. Parietal-prefrontal pathways -> formed by the subregions LIP, VIP, MT, and MST; strongly
involved in the initiation and control of eye movements and crucial for spatial working memory.
2
