Attention as Information Selection. Early Selection Early Selection model postulated that attention acted as a strict gate at the lowest levels of sensory

Attention as Information Selection

Early Selection

• Early Selection model postulated that attention acted as a strict gate at the lowest levels of sensory processing

• Based on concept of a limited capacity bottleneck

Late Selection

• Late Selection models postulated that attention acted on later processing stages (not sensory)

Late vs. Early

• Various hybrid models have been proposed– Early attenuation of non-attended input

– Late enhancement of attended input

Electrophysiological Investigations of Attention

Modulation of Auditory Pathways• Hillyard et al. (1960s)

showed attention effects in human auditory pathway using ERP

• Selective listening task using headphones

– Every few minutes the attended side was reversed

– Thus they could measure the brain response to identical stimuli when attended or unattended

beep beep beep beep boop beep

beep beep beep boop beep beep

attending LEFTIgnoring RIGHT

Modulation of Auditory Pathways

• Result: ERP elicited by attended and unattended stimuli diverges by about 90ms post stimulus– Long before response is made

– Probably in primary or nearby auditory cortex

• Chellazi et al ( 1993) Neural Correlates of Visual Search

– Monkey is trained in a 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

Intracranial Recordings of Attentional Selection


• Note that monkey isn’t “pre-cued” to attend to a location– Only target features are known

prior to choice array onset

• 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


• Initial response of cells is “classical”



• Response during delay maintains a representation of the target feature



• Response during delay represents the target feature

• Initial response to search array is “classical”


• 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


• Conclusion: – Attentional selection of locations and/or objects has

physiological correlates and consequences

– The ‘bottleneck’ in a sustained shadowing paradigm is at least as early as ~100 ms

– The ‘bottleneck’ in a visual search paradigm can be at least as early as ~200ms and appears at least as “low” in the visual system as V4 (but note that 200ms is long enough for substantial feedback connections to be active)

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Attention as Information Selection. Early Selection Early Selection model postulated that attention acted as a strict gate at the lowest levels of sensory