NEUR 3680 Midterm II Review Megan Metzler

Attention Operational Definition: Controlling how information flows through the brain Key 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 disregarded 2.Relevant neural representations enhanced  Consider examples of evidence supporting each conceptualization.

Which conceptualization does the evidence support? 1.Irrelevant neural representations disregarded 2.Relevant neural representations enhanced Change blindness Chelazzi et al. (1993)

Posner et al. (1980) Which conceptualization does the evidence support? 1.Irrelevant neural representations disregarded 2.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 Selection 2.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 Selection 2.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 Selection 2.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 effect Transient Attention Priming not as effective Tata et al. (2001) CZ Tata, Prime, McDonald, & Ward (2001) Tata et al. (2001) - + 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 stimulus Hopfinger 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).

Questions 1.Name a difference between auditory and visual attention (other than the type of stimulus).

Questions 1.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

Questions 2.Describe an example of “neglect” in the “normal” population. What may account for this phenomenon?

Questions 2.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

Questions 3.Give two examples of how unilateral spatial neglect may impact attention.

Questions 3.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

Questions 4.Describe the Posner paradigm with individuals with parietal lobe lesions. What does it tell us about the parietal lobe?

Questions 4.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