55-101 Lecture Notes - Retinotopy, Optical Flow, Visual System

20 views1 pages
Outline of Lecture 66 (03-27 A; Connor)
Visual System III – Dorsal Pathway
I. Introduction to the dorsal pathway
- The dorsal pathway processes depth and motion
- Components of the dorsal pathway are V1, V2, V3, middle temporal (MT), medial superior
temporal (MST), intraparietal regions (lat., vent., med., ant.), and area 7a
- Lesions in the human parietal cortex can cause
- Attentional hemineglect: neglect of contralateral space, also manifested in memory
- Constructional apraxia: inability to reproduce complex objects
II. V1, V2: lower level processing of stereoscopic vision
- 3D depth perception is achieved by stereopsis: there is a slight disparity between the images on
the two retinas
- Both V1 and V2 are tuned to binocular image disparity and motion direction
III. MT: intermediate level processing
- MT cells respond to motion direction and speed, as well as to binocular disparity
- MT receptive fields are larger than in lower levels
- MT columns are organized in smooth gradients of direction preference and stereoscopic depth
- Microstimulation of MT cells can bias perception of motion direction and depth
IV. MST, VIP, LIP, MIP, AIP, 7a: higher level processing
- Medial superior temporal (MST)
- Dorsal: tuned to direction and foci of optic flow (due to self-motion)
- Lateral: has role in smooth eye pursuit
- Ventral intraparietal (VIP): integration of visual and tactile space, tuned to congruous
motion/tactile stimulus
- The sequence LIP MIP AIP is responsible for grabbing objects of interest
- Lateral intraparietal (LIP): eye saccades
- Medial intraparietal (MIP): arm reaching movements
- Anterior intraparietal (AIP): hand grasping
- Area 7a: considered highest level of ventral pathway, convergence and integration of several
types of visual info
V. Note on visuospatial coordinate systems
- Visual system must deal with information coded in various coordinate systems (e.g. retinotopic,
head-centered, body-centered, etc.)
- How coordinates systems are dealt with
- Sequential transformation from one system to another as one progresses along the visual
pathway, so any given level uses only one coord sys: evidence for this in lower levels
- Integration of info in multiple coordinate systems, resulting in a mix of spatial sensitivity: most
cells in higher areas do this
Summary of major ideas
- See Objectives on p. 1
Unlock document

This preview shows half of the first page of the document.
Unlock all 1 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Notes+

Unlimited access to class notes and textbook notes.

YearlyBest Value
75% OFF
$8 USD/m
$30 USD/m
You will be charged $96 USD upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.