Cognitive Neuroscience notes

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Attention Part II – Thursday March

20th

o Last

class – basics of attentional processing, early vs. late attentional models,

and neuroimaging of visual attention

o Spatial

attention vs feature attention

o Distinct

representations for features in visual brain regions (color, shape, motion,

etc)

o Spatial

attention and objects

o Duncan

(1984) – two perceptual judgments about the same object can b made

simultaneously without a loss of accuracy

§

Reveals processing limitation in object

attention

§

Attention is facilitated within an object but

there is a cost to move attention between objects

§

Implies that object attention may be a separate

system from the spatial attention system

o Object

attention (Mueller and Klein, 2003)

§

fMRI study design to directly contrast attention

to location with attention to objects

§

Valid trials, two types of invalid trials

·

Inside same object

·

On a different object

§

Results = reaction times are fastest for valid

cues, and slowest when the target appeared on a different object

§

Presence of objects can influence spatial attention

o O’Craven

(1999) – superimposed transparent faces and houses on to the same space,

spatial differences are eliminated from the experimental design

§

One objet moved back and forth while one

stationary

§

Which object moved carried across blocks

§

Subjects told to selectively attend to motion,

houses, or faces

§

Brain activity in select areas that should track

the objects that are attended

§

Results = FFA which is used specifically for

face recognition was lit up when asked to watch the face moving, same effect

for house when looking at the PPA; when asked to pay attention to the static

object, the results were reversed and held up

o Attentional

control networks

o A

major component of attention is shigting in and out of various attentional

states

o How

does the brain accomplish this?

§

Brain activation in various sensory and motor

areas are altered during occurring of attention and are considered the site of attentional

modulation

§

Higher-order

executive control system of attention projects to sensory specific cortical

areas to impact their excitability or responsiveness

o Hopfinger

(2000)

§

Stimuli presented to both visual fields,

subjects cued to attend to one side

§

Press a button if some squares are grayed out,

but only on CUED side

§

Lag between cue and onset f visual stimuli is

the time where attention is allocated

§

Results reveal there are distinct regions for

the attentional control task vs. the visuospatial task

§

A frontoparietal network (+STS) appears to

control attention

§

Areas where attention to the LEFT produced more

activity than attention on the right, same as vice versa

o With

selective visual attention, a cortical network seems to mediate the neural

activation in the visual cortex (frontal parietal) à including the:

§

Posterior parietal cortex

§

Dorsolateral and superior prefrontal cortex

§

Anterior cingulated cortex

§

Superior temporal sulcus

§

^^ Dorsal attention network à Cuing activates this frontoparietal

network à

does not activate the network if the cue is irrelevant à modulation of visual stream

processing depends on the activation of the dorsal attention network

o When

we allocate attention to invalid cues, a different set of brain regions is

activated though to track reorienting and novelty in attention

o Temporoparietal

junction, and inferior and middle frontal gyri à

damage leads to neglect syndrome

o Ventral

attention network areas of activation in the right hemisphere for invalid cue

trials

o Dorsal

attentional network might give detection to assailants

o Subcortical

structures is how things get from one place to another

o Superior

colliculus

o Midbrain

nucleus

o Has

receptive fields like other visual areas

o Involved

in the orientation of attention indirectly

o Controls

eye movements in attention

o Receives

inputs from the cortex and basal ganglia, retina

o Outputs

to the thalamus and motor and visual system

o Damage

to the superior colliculus will show reduced inhibition of return

o Pulvinar

nucleus of the thalamus

o Activated

during attentional focus

o Widely

connected to many brain regions

o Has

visual subdivisions of neurons selective to color, motion, and orientation

o Involved

in both voluntary and involuntary attention and filtering

o Drugs

that inhibit pulvinar activity lead to inhibition in shifting of covert

attention, and deficits in color perception

o Damage

to the neurology of attentional systems

o Self

portraits following brain damage from stroke

§

Neglect to the visual field that is contralateral

to the side of the brain with damage

§

Recovery is evident in the improvement in the

clarity of the portraits over time

o Unilateral

spatial neglect (Hemifield neglect) – ignoring one half of the visual world

completely

§

Will not properly segment lines or reproduce

figures

§

Will eat off of half of the plate; shave half of

the face, etc.

o R

parietal is specialized or spatial info

o L

parietal is more bilaterally represents left and right visual fields

o Right

hemisphere is biased toward more global processing à less likely to be sever in

left hemisphere, and is generally transient

o No

prob with visual system per se, but with attention

§

Neglect are linked to differential brain damage

o Viewer-based

neglect – damage o right inferior/parietal lobe; ignore left half of space

o Object

based neglect – damage to right superior temporal gyrus; ignore left half of

objects

o Bisiach

& Luzzatti (1978)

§

Asked neglect patients to describe a piazza they

were familiar with

§

They neglected the portion that was contralteral

to the cortical damage

§

Shows that vision is not the impairment, and

that imagery is also susceptible to attention biases

§

Memory is preserved, but not readily accessible

§

Neglected information is highly processed,

neglect patients can make same/different judggments even if they canot report

what was in the neglected hemisphere (Volpe)

o Balint’s

syndrome – bilateral damage to portions of posterior parietal and occiptal

cortices à

inability to pereceive multiple objects in space

Tuesday March 25, 2014 – Memory

o Working

memory = short term memory

o Long-term

memory = semantic memory and episodic memory

o GUEST

SPEAKER

o Riding

a bike or snowboarding = procedural memory/skill learning

o Fear

of dogs after having been bitten = conditioning

o Increased

probability of using a word or phrase that has recently been uttered à conceptual/lexical

priming

o Increased

ease of recognizing a face due to having seen the person recently à perceptual priming

o Learning

and memory stages

o Encoding

– acquisition (sensory of registration of input), consolidation

o Structures

of memory

o Medial

temporal lobes

§

Amygdala

§

Parahippocampal gyrus

·

Entorhinal cortex

·

Perirhinal cortex

·

Parahippocampal cortex

o Amnesia

o Deficits

in memory

o Soap-opera

amnesia – what is portrayed in the movies as a claim of total amnesia from the

past = retrograde amnesia

o Real

life – people generally have partial recall of memories for events prior to the

amnesia onset

o Can’t

remember things before the event = retrograde amnesia, can’t remember things

after the event = anterograde amnesia

o HM

– hippocampus removed in surgery to prevent epileptic seizures à resulted in dense

amnesia

§

Bilateral removal of hippocampus and medial

temporal lobe (surrounding parahippocampal gyrus)

§

Intact à

normal working memory (short term), language, attention, childhood memories

§

He could not form any new memories, but he

showed intact learning and retention, although there was no “conscious” memory

of the episode

o Long-term

memory à

declarative and non-declarative

§

Declarative à

episodic (remembering your first day at school) à

semantic (knowing the capital of France)

§

Non-declarativeà

skill learning (knowing how to ride a bike) à

priming (being more likely to use a word you hard recently) à conditioning

(salivating when you see a favorite food)

o Memory

consolidation à

hippocampus is essential for consolidation and initial encoding of episodic

information and perhaps recall

o MTL

(medial temporal lobe) memory models

o Declarative

memory models à

Hippocampus ßà perirhinal cortex ßà parahippocampal cortex

o Dual

process models – division of labor in the MTL (certain structures are for the

“what” and others are for the “where”)

o How

to quantify memory processes

o Familiarity

tests (Willie Nelson example)

§

Combo of R&F = bow shape

§

Double dissociation – recollection vs.

familiarity data that shows different sensitivities in different parts of the

brain depending on whether the subject is recollecting or only finds the

stimulus familiar = proof of the double processing model of how memory works

o Hippocampal

lesions impair recollection but spare familiarity in both humans and rats

§

Encode 10 odors in 10 cups, then give them 30

minutes, then let them retrieve it à

train rat to know that if they smell a new scent, they can dig for reward, if

the scent is old, they go to the back of the cage for the reward

·

Testing for confidence – cup size (they’re only

going to dig in the deeper cups if they are really confident)

§

Results – hippocampal lesions in rats bring

about the same results as hippocampal lesions in humans à hippocampus is necessary for

recollection, and the perirhinal cortex is sufficient for familiarity

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