wk 4 SP - visual cortex

Question 1

Ganglion cell fibres leave
retina along _________ _________

Answer 1

optic nerve

Question 2

Beyond optic
chiasm the optic
nerve becomes
the ______ _______

Answer 2

optic tract

Question 3

Optic Tract
info now separated by _____ _____rather than by ______

Answer 3

visual field
eye

Question 4

LGN =

Answer 4

Lateral Geniculate Nucleus

Question 5

the optic tract feeds into the

Answer 5

LGN

Question 6

LGN = bilateral
structure meaning

Answer 6

(one in left
hemisphere and one
in right)

Question 7

Each LGN receives
input from left and
right eyes – but keeps
these inputs

Answer 7

separate

Question 8

LGN Receptive Fields

Answer 8

LGN cells have the same
receptive field organisation
as retinal ganglion cells:
centre-surround
antagonism.

Ideal for detecting spots of
light & edges
* But NOT able to detect
orientation of lines/ edges

Question 9

Objects close
together in the
visual scene are
analysed by
(neighbouring/far) parts
of V1.

choose one

Answer 9

neighbouring

Question 10

Amount of cortex
devoted to
representing each part
of the retinal field is
distorted, e.g:

Fovea represented by (small/large) area of cortex

choose one

Answer 10

large

Question 11

Fovea accounts of _____% of the
retina but is represented by___ - __ % of V1

Answer 11

0.01%

8-
10%

Question 12

do V1 cells have a level of baseline activity when no stimulus is presented

Answer 12

yes

Question 13

V1 cells prefer lines of a

Answer 13

particular orientation

Question 14

3 different types of cell in V1 each with distinct receptive field organisation

Answer 14

• simple cells
  -complex cells
  -Hypercomplex cells

Question 15

Simple Cell Receptive Fields

Answer 15

Simple cells respond to
oriented lines and
edges

The receptive field has
excitatory and inhibitory
regions, but they are
elongated

e.g. if the excitatory region is vertical, a vertical line would cover the excitatory and not the inhibitory, causing a big excitatory response
whereas a slanted line would cover inhibitory regions, causing a weaker response

Search image up on google to get better idea

Question 16

Orientation tuning

similar orientations

Answer 16

Orientation tuned neurons
respond best to their
preferred orientation but
also respond to other
similar orientations

Question 17

different types of simple cells (v1)

Answer 17

Some simple cells have ON-centre RFs and some have
Off-centre RFs, but all have a preferred orientation

Question 18

Complex Cell Receptive Fields

Answer 18

Respond to oriented lines but no discrete ON
and OFF regions

respond to moving oriented lines and edges
- respond best to a particular direction of
movement

Question 19

Hypercomplex Cell Receptive Fields

Answer 19

Also called End-stopped cells
* Respond to lines of:
– particular orientation AND
– moving in a particular
direction AND
– particular length

Question 20

Areas seem to be
specialised e.g.
– v3 =
– v4 =
– v5 =

Answer 20

form
colour
motion

Question 21

Processing streams: What vs. Where

‘What’ stream

Answer 21

Travels ventrally to inferotemporal cortex
* Important for recognising and
discriminating objects

Question 22

Processing streams: What vs. Where

‘Where’ stream

Answer 22

Travels dorsally to posterior parietal cortex
* Important for determining where an object is and how to
act upon it
* Sometimes referred to as the ‘How’ stream

Question 23

Optic ataxia

Answer 23

Damage to dorsal pathway (‘where/ how’ stream):
* Cannot reach to grasp objects, but can recognise
and describe them
* Opposite deficits to those shown patients with
visual form agnosia (e.g. patient DF)

Question 24

Visual form agnosia

Answer 24

Damage to ventral pathway (‘what’ stream):
* Cannot identify objects despite knowing their features