Read this article for Friday next week [1]Chelazzi L, Miller EK, Duncan J, Desimone R. A neural basis for visual search in inferior temporal cortex. Nature 1993; 363:
Test Oct. 21 Review Session Oct 19 2pm in TH201 (that’s here)
Test Oct. 21 Test will cover everything including vision (i.e. including the lecture on Friday Oct. 9 th )
Video
Attention Controlling how information flows through the brain
Attention as Information Selection – consider a simple visual scene:
Attention as Information Selection – consider a simple visual scene:
Attention as Information Selection – consider a simple visual scene: – What happens in the brain when this scene appears?
Attention as Information Selection – consider a slightly more complex scene – What happens in the brain when this scene appears?
Attention as Information Selection – consider a slightly more complex scene and a simple task: – What has to happen in order for this task to be accomplished? “point to the vertical line”
Attention as Information Selection That might not seem complex because the visual target and the output “device” are represented by the same hemisphere
Attention as Information Selection – What if the scene gets more complex? – What has to happen in order for this task to be accomplished?
Attention as Information Selection – What if the scene gets more complex? – What has to happen in order for this task to be accomplished?
Attention as Information Selection – What if the scene and task gets more complex: “Point to the red vertical line”? – What has to happen in order for this task to be accomplished?
Attention as Information Selection problem: When those stimuli appear, activity begins simultaneously among many different neurons in the cortex. How does the rest of the brain (memory, motor planning, consciousness) know which is the target?
Attention as Information Selection It get’s trickier: – Recall that the visual system has two pathways: what(ventral) and where (dorsal) – the dorsal pathway doesn’t “know” anything about orientation (or color or complex forms or identities) – The ventral pathway doesn’t “know” anything about location – What if the scene is really complicated!?
Point to Waldo
Attention as Information Selection One conceptualization of attention is that it is the process by which irrelevant neural representations are disregarded (deemphasized? suppressed?) Another subtly different conceptualization is that attention is a process by which the neural representations of relevant stimuli are enhanced (emphasized? biased?)
Attention as Information Selection These ideas apply to other modalities – auditory “Cocktail Party” problem – somatosensory “I don’t feel my socks” problem
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)
Early Selection Early Selection model was intuitive and explained most data but failed to explain some findings Shadowing studies found that certain information could “intrude” into the attended stream – Subject’s name, loud noises, etc.
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 LEFT Ignoring 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
Modulation of Auditory Pathways Other groups have found ERP modulation even earlier – as early as Brainstem Auditory Response Probably no robust modulation as low as cochlea by ~40 ms, feed forward sweep is already well into auditory and associated cortex – Thus ERP effects may reflect recurrent rather than feed forward processes
Modulation of Auditory Pathways Different ways to use attention in space beep beep beep beep boop beep beep beep beep boop beep beep attending LEFT Ignoring RIGHT beep beep beep beep boop beep now left, now right, now left, now right beep beep beep boop beep beep SUSTAINEDTRANSIENT
Modulation of Auditory Pathways Response times are faster for attended relative to unattended targets The theory is that transient and sustained attention act on auditory pathways the same way beep beep beep beep boop beep now left, now right, now left, now right beep beep beep boop beep beep TRANSIENT
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – Three speakers – Steady stream of tones – Respond to each tone
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – Three speakers – Steady stream of tones – Respond to each tone BEEP
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – Three speakers – Steady stream of tones – Respond to each tone
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – Three speakers – Steady stream of tones – Respond to each tone BEEP
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – Three speakers – Steady stream of tones – Respond to each tone
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – Three speakers – Steady stream of tones – Respond to each tone BEEP
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – Three speakers – Steady stream of tones – Respond to each tone
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – Three speakers – Steady stream of tones – Respond to each tone BEEP
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – We can compare targets preceded by targets at the same location with targets preceded by targets on the other side
Modulation of Auditory Pathways Transient Attention: The Target-Target Paradigm – Does transient attention modulate auditory system like sustained attention?
Modulation of Auditory Pathways ERP is markedly different in the two situations! Tata et al. (2001) CZ Tata, Prime, McDonald, & Ward (2001) Tata et al. (2001) - +
Modulation of Auditory Pathways ERP is markedly different in the two situations! One possibility: – sustained attention allows for attentional configuration of sensory cortex to modulate feed- forward sweep but… – Transient attention can only modulate recurrent processes
Modulation of Auditory Pathways Earliest attention-related component (called the Nd1) is over contralateral posterior scalp - not primary cortex Tata & Ward (2005)