PSYC 375: Brain and Sensory Processes Exam 3 Copy

What are the four other names for the primary visual cortex?

1. V1
2. Brodmann's area
3. Area 17
4. Striate cortex

How many layers does the primary visual cortex have?

6 layers

Which of the 6 layers of the primary visual cortex splits up into three sublayers?

The 4th layer (4A, 4B, 4C)

Which of the three sublayers of the 4th layer of the primary visual cortex is the major recipient from the LGN?

Layer 4C

What is retinotopy?

Map of the visual field into a target structure

What are the target structures that a visual field can appear on?

Retina, LGN, superior colliculus, striate cortex

Where do retinatopic maps begin?

In the retina

How does projection work in retinotropy?

Adjacent cells in retina project to adjacent neurons in LGN, which in turn project to adjacent cells in striate cortex

What creates the visual image in retinotopic maps?

Receptive fields

How does the visual image appear on the target structures?

Appears inverted/flipped

What kind of cells are layers 4C?

Spiny stellate cells

What are spiny stellate cells?

Spine-covered dendrites

What kind of cells are layers 3, 4B, 5, and 6?

Pyramidal cells and inhibitory neurons

What kind of cells does layer 1 have?

NONE--most superficial layer

What are pyramidal cells?

Spines; thick apical dendrites

What is special about pyramidal neurons?

They have active membranes--can generate AP's on their dendrites through voltage gated channels

What are inhibitory neurons?

Lack spines; all cortical layers; form local connections

What does the 4Ca layer receive input from?

Magnocellular neurons

What does the 4Cb layer receive input from?

Parvocellular neurons

How is the organization of the projection from retina to the visual cortex?

HIGHLY organized

What layer does magnocellular neurons project into?

Layer 4Ca

What layer does parvocellular neurons project into?

Layer 4Cb

What layers do koniocellular neurons make synapses in?

Layer 1 and 3--bypasses layer 4

What kind of inputs to the striate cortex are all three of these (magnocellular, parvocellular, koniocellular)?

Monocular

What does ONLY layer 4 contain?

Ocular dominance columns

What are ocular dominance columns?

Blue input from one eye, tan inputs from other eye (monocular)

What layer innervates layers 2 and 3?

Layer 4C

Are cells in layer 3 monocular or binocular?

Binocular (although input from one eye still dominant)

What does binocular mean?

Receives input from both eyes

What do layers 2, 3 and 4B of the striate cortex send outputs to?

Projects to other cortical areas

What does layer 5 of the striate cortex send outputs to?

Projects to the superior colliculus and pons

What does layer 6 of the striate cortex send outputs to?

Project back to the LGN

What is cytochrome oxidase?

A mitochondrial enzyme used for cell metabolism

What contains cytochrome oxidase?

Cytochrome oxidase blobs

How are these blobs visualized?

By cytochrome oxidase staining in cross sections of the striate cortex

What do blobs receive inputs from?

Direct input from Koniocellular LGN neurons and input from layer 4Cb neurons

What layers are koniocellular cells in?

Layers 1 and 3

What are the neurons in layer 4Cb called?

Parvocellular neurons

What kind of pathways do magnocellular, parvocellular, and koniocellular neurons have?

Parallel pathways

What is the magnocellular pathway?

M-type ganglion cells (in retina) > Magnocellular neurons (in LGN) > Layers 4Ca and 4B (in V1) > Extrastriate cortical areas

What kind of receptive field does the magnocellular pathway have?

Large, binocular receptive fields

What are the large receptive fields in the magnocellular pathway best at detecting?

Motion

Other facts about magnocellualar pathway RF's?

Orientation selective, some direction sensitive, not wavelength selective (color-opponent)

What is the blob pathway (or koniocellular pathway)?

nonM-nonP ganglion cells (in retina) > Koniocellular cells (in LGN) > Blobs (in V1) > Extrastriate cortical areas

What is the blob pathway involved in?

Color vision

Facts about blob pathway RF's?

Monocular, typically center-surround, color-opponent

What do the blobs in the blob pathway also receive input from?

From layer 4C in the magnocellular and parvocellular pathways

What is the interblob pathway (or parvocellular pathway)?

P-type ganglion cells (in retina) > Parvocellular cells (in LGN) > Layers 4C and interblob (in V1) > Extrastriate cortical areas

What kind of receptive fields does the interblob pathway have?

Binocular, small receptive field

What is the interblob pathway involved in?

Detecting fine object shapes

Facts about parvo-interblob pathway RF's?

Orientation selective, not direction or wavelength sensitive

What does "direction selective" mean?

Only in one direction

What is "orientation selectivity" mean?

Visual stimulus must be in a certain position for optimal AP's

Which neurons have orientation selectivity?

Magnocellular and parvocellular

Is the visual stimuli the same for every neuron?

NO--neurons have different "best" visual stimuli

How does visual stimulus change?

Preference changes as it goes down orientation columns

Bar stimulus or spot stimulus for orientation stimulus?

Bar stimulus

Which layer is direction and orientation selective?

Layer 4B

What is direction selectivity?

Neuron fires action potentials in response to moving bar of light only if it moves in a particular direction

Facts about simple cells?

Binocular, orientation-selective, elongated on-off region with antagonistic flanks responds to optimally oriented bar of light

How to simple cells arise?

Possible as a result of convergent input from cells with linearly arranged center-surround receptive fields

What are complex cells?

Similar to simple cells, but give excitatory response in both center and flanking regions

One place you will never find simple cell receptive fields?

Blob pathways

What is the dorsal stream?

Analysis of visual motion and the visual control of action

What else is the dorsal stream called?

Where pathway

What is the dorsal stream a continuation of?

Largely a continuation of the magnocellular pathway

What is the ventral stream?

Perception of the visual world and the recognition of object

What else is the ventral stream called?

What pathway

What is the ventral stream a continuation of?

Largely a continuation of the parvocellular (inter-blob) and koniocellular (blob) pathways

Recognition is to ___, as registering is to ___.

Dorsal, ventral

What areas are apart of the dorsal stream?

V1, V2, V3, MT, MST, other dorsal areas

What is Area MT?

Temporal lobe

What are features of most cells in Area MT?

Direction-selective, respond more to the motion of objects than their shape

What does area MST receive input from?

MT

What are the cells in Area MST responsive to?

Optic flow

Primary output of MT goes too?

MST

What does Area MST deal with?

Movement

What areas are apart of the ventral stream?

V1, V2, V3, V4, IT, and other ventral areas

Features of many of the cells in Area V4?

Many cells have complex RF's and color selectivity

What is achromatopsia?

Clinical syndrome in humans caused by damage to area V4--partial or complete loss of color vision (no damage to retina, LGN, or V1)

V4 isn't just a vision area--what else is it?

Form and shape processing

Major output of Area IT?

V4

Features of Area IT?

Respond to a wide variety of colors and abstract shapes,
Some evidence of position invariance,
Evidence for 'face-selective" neurons in IT

What is the region within IT that shows evidence for "face-selective" neurons?

Fusiform Face Area (FFA)

What is a Grandmother cell?

Hypothetical neuron that represents any complex and specific concept or object

Are face-selective neurons in area IT 'grandmother cells'?

Would be a need for every single object in the visual world to be encoded by its own unique neuron;
Not likely: Perception is not based on the activity of individual, higher order cells

What are the three channels of information processing?

M, P and Blob

What do different cortical areas contribute to?

The perception of color, motion and form

What is the binding problem?

How the various features are combined or bound together to generate perception of an object is presently not known

How does vision occur?

Parallel processing by several visual pathways

What is the operational definition of consciousness?

If a cooperative person reports the presence of one stimulus and can not report the presence of a second
stimulus, then he or she is conscious of the first and not of the second

What does consciousness require?

Attention

We are only conscious of stimuli that we _ ____. We are not conscious of the __ __.

We are only conscious of stimuli that we attend to. We are not conscious of ignored stimuli.

What is attention?

Attention is the selective
processing of a portion of a larger group of simultaneous sensory stimuli

What does the stimuli to which we can attend to represent?

Represents a fraction of the
stimuli that stimulate the retina and primary visual cortex

What is enhanced detection?

Detection of brief, faint stimuli is facilitated when attention is directed towards the location where the stimulus will be presented

Why is enhanced detection important?

This is how attention is studied

What is an invalid cue?

Cues that direct attention away from the location where the stimulus will appear-

What do invalid cues reduce?

Reduce detectability to chance levels

What does attention do to the reaction speed?

Increases it