NEUR 3680Midterm II Review

Megan Metzlermegan.metzler@uleth.ca

AttentionOperational Definition:• Controlling how information flows through

the brainKey Concepts:• Focused on vision, but encompasses all

sensory modalities• “Spotlight” of attention• Highly complex process

– Multiple stimuli commonly present– Hemispheric specialization, specialized pathways

Conceptualizations of Attention:1.Irrelevant neural representations disregarded2.Relevant neural representations enhanced

Consider examples of evidence supporting each conceptualization.

Which conceptualization does the evidence support?1. Irrelevant neural representations disregarded2. Relevant neural representations enhanced

• Change blindness• Chelazzi et al. (1993)

Posner et al. (1980)

Which conceptualization does the evidence support?1. Irrelevant neural representations disregarded2. Relevant neural representations enhanced

Models of Attention:1.Early Selection Model- at sensory level

2.Late Selection Model- at higher level

3.Hybrid Models- early attenuation of non-attended input and late enhancement of attended input

Be able to provide examples of lines of evidence supporting early and late selection models.

Which model does the evidence support?1. Early Selection2. Late Selection

Cherry et al. (p. 496)• Used dichotic listening; told to attend to one ear

• Subjects could not report information from the unattended ear.

Which model does the evidence support?1. Early Selection2. Late Selection

Others (Moray, Treisman) (p. 497)• Used dichotic listening; told to attend to one ear

• Subjects could report information such as their name (high priority) from the unattended ear

Which model does the evidence support?1. Early Selection2. Late Selection

Hillyard et al. (1960s) • Used ERP to study auditory attention

• 90 ms post stimulus- likely in or near auditory cortex

Differences Between Sustained and Transient Attention

Sustained Attention • Not environmentally valid• Strong priming effectTransient Attention• Priming not as effective

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Tata et al. (2001)

CZCZ

Tata, Prime, McDonald, & Ward (2001)

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Tata et al. (2001)

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Transient

Sustained

Chelazzi et al. (1993)• Neural Correlates of Visual Search

• Intracranial recordings at inferior temporal cortex

– Delayed match-to-sample task• Cue appears 1.5 seconds before search array• Monkey saccades to target

– “good” and “poor” stimuli are identified for each recorded neuron

• Note that monkey isn’t “pre-cued” to attend to a location

– Only target features are known prior to choice array onset

Is this testing sustained or transient attention?

• With this paradigm it is possible to measure cell activity during delay, during search, and after selection

• Note that search array always contains a “good” stimulus for the recorded cell – but that might not be the target

Chelazzi et al. (1993)Intracranial Recordings of Attentional Selection

• Initial response of cells is “classical”

Chelazzi et al. (1993)Intracranial Recordings of Attentional Selection

• Response during delay maintains a representation of the target feature

Chelazzi et al. (1993)Intracranial Recordings of Attentional Selection

• Initial response to search array is “classical”

Chelazzi et al. (1993)Intracranial Recordings of Attentional Selection

• About 200 ms after array onset, response of cell begins to depend on attention

– Response becomes more vigorous if cell is tuned to features of the target (i.e. the selected stimulus)

– Response becomes suppressed if cell is tuned to a non-target distractor

Chelazzi et al. (1993)Intracranial Recordings of Attentional Selection

Is this evidence of early selection or late selection for attention?

Attention Orienting

Corbetta et al. (1993)• Contralateral parietal and premotor areas

active during attention tracking task, BUT• Confounded by activations related to stimulusHopfinger et al. (2000)• Examined cue-related activations• Left frontal and parietal structures active

Unilateral Spatial Neglect• Results from lesion of parietal or temporo-

parietal junction (often the right hemisphere)• Hemispatial neglect may relate to

– Extrapersonal space or own body (personal space)– the visual field or be object-based

Unilateral Spatial Neglect• Remember Posner’s experiment with valid

and invalidly cued targets? Here’s the same paradigm used with individuals with USN.

Extinction• Subtle form of neglect• Individual fails to attend to

stimuli in affected field when stimuli present in unaffected field (when presented one at a time, the individual is able to attend to stimuli in the affected field).

Questions1. Name a difference between auditory and

visual attention (other than the type of stimulus).

Questions1. Name a difference between auditory and

visual attention (other than the type of stimulus).

Length of attentional units• Several seconds for auditory, ms for visual

Questions2. Describe an example of “neglect” in the

“normal” population. What may account for this phenomenon?

Questions2. Describe an example of “neglect” in the

“normal” population. What may account for this phenomenon?

Change blindness (provide an example) Spotlight of attention or early

attenuation of irrelevant stimuli If you missed class, check out

BBC.Brain.Story.3of6.The.Minds.Eye.XriD.AC3.NewMov.avi

Questions3. Give two examples of how unilateral spatial

neglect may impact attention.

Questions3. Describe two examples of how unilateral

spatial neglect may impact attention. Auditory neglect for information from one

side of external space (usually left) Visual: Object-based neglect, personal

neglect, etc. usually of left

Questions4. Describe the Posner paradigm with

individuals with parietal lobe lesions. What does it tell us about the parietal lobe?

Questions4. Describe the Posner paradigm with

individuals with parietal lobe lesions. What does it tell us about the parietal lobe?

Close to normal performance for validly cued trials

Poor performance for invalid trials with target in the affected visual field

The parietal lobe may play a role in disengaging the spotlight of attention