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NYU / Psychology / PSY 25 / What is the difference between spatial neglect and blindness?

What is the difference between spatial neglect and blindness?

What is the difference between spatial neglect and blindness?


School: New York University
Department: Psychology
Course: Cognitive Neuroscience
Professor: Clay curtis
Term: Winter 2016
Tags: cognitive neuroscience nyu, Cognitive Neuroscience, Psychology, cog neuro, neuroscience, psych, and NYU
Cost: 25
Name: Attention I & II
Description: These notes are the entire unit on Attention (should be equivalent to 2 lectures)
Uploaded: 03/10/2016
5 Pages 116 Views 12 Unlocks

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2.0.1. Attention I & II

What is the difference between spatial neglect and blindness?

William James: ​Attention can be something we voluntarily control (selective). We can’t attend to all things at once

● “It [attention] is the taking possession by the mind...of what seems [like] several simultaneously possible objects or trains of thought.Focalization, concentration of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others.”

Neglect Syndrome: ​Patients with neglect act as if portions of their world do not exist. They may deny the existence of certain parts of their body or objects in certain visual fields. ● Unilateral spatial neglect: ​Most commonly follows lesions to

What does cocktail party effect entail?

right hemisphere in patients. Spatial neglect affects visual Don't forget about the age old question of What distinguishes an incoporated mismatch from mismatch and mutation?

fields contralaterally, so a lesion to the right hemisphere

would result in neglect of the left visual field.

○ Patients with unilateral spatial neglect have problems

copying drawings.​They do not draw what is on the

left side.

○ Line Bisection Test:​The test requires that subjects

indicate the midpoint of a horizontal line. Patients with

neglect may put a mark on the line where they see it is half and usually that is towards the side of the brain with the lesion. The test proves that not only is space neglected, but objects in that space are neglected as well.

What are the two separate fronto-parietal cortical system?

○ Gaze Bias: ​Eye movements typically do not focus on the side that is neglected.** ○ When a neglect patient recalls a visual memory, the portion of the scene contralateral to the lesion is not described. Don't forget about the age old question of What is the function of pharynx?

○ Several studies have revealed that even though a stimulus to the neglected side of space may fail to be reported, it may nevertheless be processed to a 

substantial degree, at least to its meaning or identity (Semantic Priming​) 

How we distinguish Spatial Neglect from Blindness 

● Extinction: ​Failure to perceive objects contralateral to lesions (so objects in left side) when simultaneously presented with objects ipsilateral to the lesion (On the same side of lesion). The object presented on the ipsilateral (right) side wins out because the rightDon't forget about the age old question of What did the bretton woods conference do?
We also discuss several other topics like What influences chronic medical conditions?

visual field is still intact, and the left side of the brain (W/o the lesion) is managing that field.

○ Those who are affected by extinction have a lack of awareness in the contralesional side of space (towards the left side space following a right lesion) and a loss of exploratory search and other actions normally directed toward that side.’ We also discuss several other topics like How can a person maximize utility?

Balint’s Syndrome: ​Associated with bilateral damage in the occipito­parietal region. Balint’s Syndrome is associated with a triad of impairments 

1. Simultanagnosia: T​he inability to recognize more than one object presented at the same time. When the patient is focused on one object, the other object isn't seen. Attention can be focused on an object but they cannot shift attention to multiple objects at the same time. 

2. Ocular Apraxia: ​The inability to voluntarily control their gaze. People with ocular apraxia must turn their heads to follow an object since they have the most trouble initiating a change in gaze direction. 

3. Optic Ataxia: ​The inability to move the hand to to an object they are looking at. (aTAXia => TACtile) Patients cannot reach out and grab objects they are looking at. i. Optic ataxia may be caused by lesions to the posterior parietal cortex, which is responsible for combining and expressing positional information and relating it to Don't forget about the age old question of What is the role of bulge as a part of the milky way's structure?


Attention disorders tell us that in order to focus on one thing, we have to ignore another. 

Balint’s Syndrome is different from Neglect. P​eople with Balint’s Syndrome can see objects in any region of space but they have trouble focusing their attention on multiple things. People with Balint’s Syndrome can detect objects as a whole. People with neglect CANNOT. 

Spatial Neglect is different from Cortical Blindness.​People with cortical blindness are perceptually blind in a particular area of the visual field, but they are able to respond to visual stimuli. Blindsight is caused by injury to the occipital lobe (responsible for vision), their eyes themselves are not damaged. Patients with Blindsight are able to make very good predictions of location and movement of the stimulus even though they report not seeing one. and they are responding to the stimuli without consciously perceiving them.

● The level to which stimuli may be processed implicitly or unconsciously in neglect patients is far more substantial than in individuals with blindsight who have primary visual field deficits. Things in the afflicted side of space for neglect patients do not exist. 

Orienting of Attention 

Attended stimuli produce greater neural responses in visual cortical areas than ignored stimuli.

Exogenous Attention (outside):​Stimulus­ driven attention. 

● Reflexive Cueing:​When the interstimulus interval is short, responses are faster to cued locations. When the interval between stimuli is longer, responses are slower to cued location. (inhibition of return​: We have difficulty focusing on objects we have already looked at.) 

We are primed to search for things without having to go back. Its evolutionarily advantageous to do this so we stay sharp. 

Endogenous Attention(inside): G​oal oriented, voluntary attention. 

The neural mechanisms in the brain have been shown to produce different patterns of activity for endogenous and exogenous attention. 

Overt Attention:​Directing and shifting attention (eye­movements) 

Covert Attention: ​Internal shift of attention. 

Helmholtz described this idea. Attending to something without moving the body. 

Cocktail Party Effect:​The ability to focus one's auditory attention on a particular stimulus while filtering out other stimuli, similar to the way a partygoer can focus on a single conversation in a noisy room. It also describes when one may immediately detect words of importance originating from unattended stimuli (hearing one's name in another conversation). 

Posner Paradigm:​A neuropsychological test to assess attention. Posner's spatial cueing task measures manual and eye­movement reaction times to target stimuli in order to investigate the effects of covert orienting of attention in response to different cue conditions. ● Overt attention involves directed eye movements (saccades) 

● Covert attention involves mental focus or attention to an object without significant eye movement 

Dichotic Listening:​Selective filtering of auditory inputs. ​Unattended speech seems like it does not even register. 

● During a dichotic listening task, a subject wears headphones where two auditory streams are being delivered to each ear. Participants were instructed to repeat the words they heard in one ear while a different message was presented to the other ear. As a result of focusing to repeat the words, participants noticed little of the message that was playing in the other ear, often not even realizing that at some point it changed from English to German. At the same time, participants did notice when the voice in the unattended ear changed from a male’s to a female’s. This suggested that the selectivity of consciousness can work to tune­in some information. 

Attentional capacity is limited

Early Selection: ​Unattended information does not receive full perceptual processing Late Selection: ​Unattended input is fully processed but stops at semantic (meaning) analysis. 

Broadbent’s Model of Selective Attention (E​arly Selection Theory) 

All stimuli are processed initially for basic, physical properties. Attention is filtered based on perceptual qualities, information that is to be processed is selected early. Channel selection is guided through attention. 

● If one is attempting to attend to a stimulus based on their current goals, they will employ voluntary attention;​whereas if a sensory event catches one's attention, reflexive attention​will be employed. Information selected to pass through the filter is then available for short­term memory and manipulation of the selected information, prior to storage in long­term memory.

ERP Research in Dichotic Listening

Spatial Cueing: ​Effects of covert spatial attention. Compared to neutral cues, valid cues are faster to detect and invalid ones are slower to detect.

Sustained Spatial Attention ​(ERP study w/ electrodes in occipital lobe) Stimuli are heightened when the stimulus appears in an attended location versus an unattended one.

● In visual cortex (using fMRI), attentional effects are seen in the hemisphere that is contralateral to the attended target (recording in V4 neurons)

● Spatial attention influences processing of visual stimuli. Attended stimuli produce greater neural responses in visual cortical areas, than ignored stimuli.

● Attention related modulation tends to be more robust in extrastriate regions (especially V4)

Biased Competition Model: ​When multiple stimuli fall within the receptive field of a visual neuron, the signals compete to control the neuron’s firing. Attention can resolve the competition. ● Higher order neurons have larger receptive fields. 

Visual Search 

Pop­Out vs. Conjunction Search:​Conjunction search takes longer because you have to pay attention to multiple characteristics. Suggests we can’t look for two things simultaneously. 

Treisman’s Feature Integration Theory p​roposes 2 stages of processing: Preattentive Stage: ​Featural “primitives” in a visual scene (color, movement) are extracted automatically in parallel 

Focused Attention Stage: A​ttention is directed to a location. The primitives are combined to form a whole.

Spotlight of Attention​: Attention is like a spotlight that is directed towards intended targets, focusing on each target in a serial manner. Information under the spotlight is processed in a more efficient manner, and stimuli surrounding the spotlight is inhibited from being processed. 

● Spatial Attention​itself is the ability to focus on specific stimulus in a visual environment. 

Feature Attention: ​Attention to basic features without assigning meaning. (The color and the shape, size, orientation) 

Two separate fronto­parietal cortical systems 

Dorsal Attention System (Spatial)​​involved in voluntary (top­down) orienting and shows activity increases after presentation of cues indicating where, when, or to what subjects should direct their attention.(You choose what you want to pay attention to.) 

Ventral Attention System (Non­spatial) I​ts main function is to reorient attention towards salient stimuli. TN is considered to be involved mostly, if not entirely, in involuntary actions. (ex. Hearing your name in a crowd.)

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