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Chapter 13

PSYB45H3 Chapter Notes - Chapter 13: Calcarine Sulcus, Temporal Lobe, Two-Streams Hypothesis


Department
Psychology
Course Code
PSYB45H3
Professor
Zachariah Campbell
Chapter
13

Page:
of 8
1
PSYB65 HUMAN BRAIN AND BEHAVIOUR FINAL TEXTBOOK NOTES
CHAPTER 13: THE OCCIPITAL LOBES
ANATOMY OF THE OCCIPITAL LOBES
Figure 13.1
Parietal-occipital sulcus: separates occipital andparietal lobes
Calcarine sulcus: lateraly separates occipital lobe (dividing upper and lower half of visual field)
Collateral sulcus: ventral surface of occipital lobe extending towards temporal
Cuneate gyrus:
Lingual gyrus: includes part of V2 and VP
Fuciform gyrus: V4
No clear divisions between occipital and temporal lobe and parietal lobe on lateral surface
(confusion of actuall boundries)
The discovery that V1 is heterogeneous (that a single cortical area could have multiple separate
functions) was unexpected
Striate cortex (striped cortex): thin stripe-colour perception; thick stripes- form percepropn and
pale stripes- moton perception
We previously thought that motion perception was independent of colour, but now we know
colour vision is integral to the analysis of position, depth, motion, and structure of objects (ie.
The way the light falls on an object gives us clues about motion and depth.)
Colour perception-adaptive- primates-selecting edible fruit on background of green leaves
CONNECTIONS OF THE VISUAL CORTEX
Before we had a hierarchical view of visual pathway but now we know that it Is more like a
distributed hierarchical process with multiple parallel and interconnecting pathways
V1-is the striate cortex- primary vision area- receives largest LGN input and projects to all other
visual areas- most basic/ fundamental level of processing
V2- input from V1- projects to all other occipital regions- second level
After v2 there are 3 distinct pathways
Dorsal stream (top) –where pathway- guidance of visual movement (towards parietal- spatial
function)
Ventral stream (bottom) –what pathway- object perception including colour
2
PSYB65 HUMAN BRAIN AND BEHAVIOUR FINAL TEXTBOOK NOTES
Superior Temporal Sulcus (STS stream) (middle) – visuospatial functions –perception of
selective types of movement (integrating the where and the what)
A THEORY OF OCCIPITAL LOBE FUNCTION
V1 and V2 are like mailboxes into which info is assembled before shipment to specialized areas
V1-lesion- blind sight – act as though you can’t see, BUT some visual input still gets
trough (via LGN to V2 which projects to V3 and so on) therefore although you can’t
consciously see you are still influenced by visual stimuli. Therefore v1 must be
functioning in order for the rest of the brain to make sense of what it is “seeing”.
V3- dynamic form: the shape of the objects in motion – lesion – results in parietal disruption of
form perception why? b/c V4 also perceives form in colour perception
V4- colour perception- lesion results in black and white vision (you couldn’t even imagine or
remember colour anymore)
V5: motion perception (also called MT for medial temporal area) lesion- results in “snap shot
vision” where moving objects vanish then reappear when they are still.
Summary of pathway connections:
V1 &V2 -> specialized areas
V1 blobs project to -> V4
V1-> V2-> V5
V1-> V2-> V3
VISUAL FUNCTIONS BEYOND THE OCCIPITAL LOBE
Table 13.1: summary of visual regions beyond the occipital lobe
VENTRAL REGIONS
Region function
LO Lateral occipital Object analysis
FFA Fuciform face area Face analysis
EBA Extrastriate body area Body analysis
FBA Fuciform body area Body analysis
STS Superior temporal sulcus Analysis of biological
motion
3
PSYB65 HUMAN BRAIN AND BEHAVIOUR FINAL TEXTBOOK NOTES
STS
p
Superior temporal sulcus (posterior) Moving-body analysis
PPA Parahipocampal place area Analysis of landmarks
DORSAL REGIONS
LIP Lateral intraparietal sulcus Voluntary eye movement
AIP Anterior intraparietal sulcus Object-directed grasping
VIP Ventral intraparietal sulcus Visuomotor guidance
PR
R
Parietal reach region Visually guided reach
cIP
S
Intraparietal sulcus Object-directed action
1900s- vision in the occipital lobes
Past few decades- we realized vision extends past occipital lobes
Vision- is concerned by more cortical areas than any other function
In fMRI studies, the localization of these functions are a matter of difference in degree of activity
associated with particular stimuli not presence of activity (meaning that all these areas light up
all at once but certain areas get associated with certain functions because they are more
prominently active in response to certain stimuli)
Ex. Rubins vase (the picture that looks half face/ half vase)
The FFA is more active is participant reports seeing a face eventho the physical stimuli
remains the same.
Other parietal-visual areas are thought to play a role in visual information used to calculate
spatial actions.
5 categories of visual processing: vision for action, action for vision, visual recognition, visual
space, and visual attention
VISION FOR ACTION
The function of the visual parietal areas
Movement that is directed by visual info ex. catching a baseball