Chapter 18 Summary & Outline

Attention Selects Stimuli for Processing

• Although we pay mostly overt attention to stimuli, we can also pay covert attention to stimuli or locations of our choosing. Attention helps us distinguish stimuli from distracters. Review Figure 18.1
• We can attend to only a small subset of available stimuli at any time; attention has been likened to a spotlight that picks out stimuli for processing. Review Web Activity 18.1
• Because we have limited processing capabilities, attention imposes a bottleneck on incoming information. The attentional bottleneck may occur early in processing or later, when stimuli reach awareness, as determined possibly by the processing load of the stimuli. Review Figures 18.2 and 18.3

Study questions: 1 | 2 | 3 | 4 | 5 | 6

Attention May Be Endogenous or Exogenous

• In endogenous attention we voluntarily select objects to attend to. It is said to be a top-down process and is studied using symbolic cuing tasks. Review Figures 18.4 and 18.6, Web Activity 18.2
• Exogenous attention is the involuntary capture of attention by stimuli. It is a bottom-up process, studied using peripheral spatial cuing tasks. Review Figures 18.5 and 18.6
• In visual search, targets may pop out if they are distinctive on a particular feature (feature search). More often, we use conjunction searches, identifying target stimuli on the basis of two or more features. Review Figure 18.7

Study questions: 7 | 8 | 9 | 10 | 11 | 12 | 13

Electrophysiological Techniques Trace Rapid Changes of Brain Activity

• Event-related potentials (ERPs) are created by the averaging of many EEG recordings from repeated experimental trials. ERPs can track neural operations with excellent temporal resolution. Review Figure 18.8
• We can study both the consequences of attention on neural processes, and the source and control of attention.
• Auditory attention enhances the N1 effect and the P20–50 effect—components of the ERP. Review Figure 18.9
• Endogenous visual attention enhances the P1 effect (the P1 component of the ERP), related to early attentional selection; and the P3 effect, related to later attentional selection. Review Figure 18.10
• Exogenous visual attention also enhances P1, but only for short delays between cue and stimulus. Review Figures 18.11 and 18.12

Study questions: 14 | 15 | 16 | 17 | 18 | 19

Many Brain Regions Are Involved in Processes of Attention

• Neuroimaging, single-cell recordings, and other anatomical studies provide excellent spatial resolution, helping us identify the brain sites involved in attention.
• Selective attention causes enhanced activations of discrete regions of sensory cortex, such as primary visual cortex and extrastriate visual areas. Review Figure 18.13
• Single-cell recordings in lab animals confirm that attention affects the responses of individual neurons. Review Figures 18.14–18.16
• Subcortical mechanisms involving the superior colliculi and the pulvinar are crucial for shifting visual attention and gaze between important objects of attention. Review Figure 8.17, Web Activity 18.3
• A dorsal frontoparietal attention network in the cortex is responsible for directing voluntary, endogenous attention. A right-sided temporoparietal attentional system, centered on the right temporoparietal junction(TPJ), is responsible for detecting and shifting attention to novel stimuli. The two networks interact extensively. Review Figures 18.19–18.21, Web Activities 18.4 and 18.5

Study questions: 20 | 21 | 22 | 23 | 24 | 25 | 26

Neurological Disorders Reveal the Anatomy of Attention

• Damage to the right hemisphere involving the right parietal cortex can cause hemispatial neglect. Patients with this condition ignore the left side of the world, presumably because of damage to attentional mechanisms. Review Figures 18.22 and 18.23
• Balint’s syndrome is a rare consequence of bilateral parietal damage. In Balint’s syndrome, patients are spatially disoriented and experience a dramatic narrowing of attention, to the point that only one object at a time can be seen (simultagnosia).
• Damage to the superior colliculi, as in progressive supranuclear palsy (PSP), may make it very difficult for the patient to switch attention between stimuli.

Study questions: 27 | 28 | 29 | 30 | 31 | 32

Consciousness Is the Most Mysterious Property of the Nervous System

• People in various unconscious states show reduced activity of frontoparietal regions. Review Figure 18.24
• The easy problem of consciousness is the problem of how to read specific current conscious experiences directly from people’s brains as they are happening. Although not currently possible, the needed technology to do this may someday be available. Review Figure 18.26
• The hard problem of consciousness is the problem of how to read people’s subjective experience of consciousness and determine the qualia that accompany perception. No one knows how to approach this problem, or even if a solution is possible. Review Figure 18.26
• Feelings of agency, sometimes referred to as free will, may rely on the activity of specific frontal lobe mechanisms. But even if that’s true, it’s possible that unconscious mechanisms make many of our decisions well before we consciously realize it. Review Figure 18.27

Study questions: 33 | 34 | 35 | 36 | 37 | 38 | 39

The Frontal Lobes Are Crucial for Higher-Order Cognitive and Emotional Functions

• Prefrontal cortex consists of dorsolateral and orbitofrontal divisions; damage in these regions produces a distinctive set of symptoms. Review Figure 18.28
• Medial aspects of the frontal lobes, including anterior cingulate regions, are associated with executive function.
• Prefrontal cortex appears to be essential for coordinating the resources needed for goal-directed behavior. Review Table 18.1
• A new field, neuroeconomics, is concerned with the neural mechanisms responsible for decision making. A current model emphasizes a ventromedial frontal evaluation system and a dorsolateral choice network.

Study questions: 40 | 41 | 42 | 43 | 44 | 45