perception

Question 1

perceptual decision making

Answer 1

From moment to moment, our brain is making deci- sions about what we should perceive, and those decisions are based on prior experiences and current incoming sensory information. bistable figures illustrates perceptual decision making at work.

brain areas: Dorsolateral PFC and posterior parietal cortex –> both involved in decision to initiate a physical movement. so those brain structures involved in action decision mak- ing are the same as those implicated in perceptual decision making.

Question 2

phantom percepts

Answer 2

the products of perception when there is an absence of sensory input.
- One example of this is the phenomenon of phantom limbs, wherein amputees perceive the presence of their missing limb long after it has been lost to injury or amputation.
- other example when an individual is deprived of visual input later in life, such as is the case for individuals who develop glaucoma (a medical condition wherein there is irreversible damage to the optic nerve). Some of these individuals experience rich and complex hallucinations (e.g., people’s faces, complex landscapes). This condition is known as Charles Bonnet Syndrome

Question 3

binding problem

Answer 3

Yet, complex stimuli are normally perceived as integrated wholes, not as combinations of independent attributes. How does the brain combine individual sensory attributes to produce integrated perceptions?

One possible solution to the binding problem is that there is a single area of the cortex at the top of the sensory hierarchy that receives signals from all other areas of the various sensory systems and puts them together to form a percept. One area of the brain that has received recent attention as the potential location for the binding of sensory information is the claustrum

An alternative solution to the binding problem is that there is no single area responsible for putting together per- ceptions. Rather, perceptions might be the result of multiple interactions at each of the cortical levels of the hierarchy.

Question 4

selective attention characteristics:

Answer 4

2 characteristics
1. It improves the perception of the stimuli that are its focus
2. interferes with the perception of the stimuli that are not its focus

Question 5

Attention can be focused in two different ways:

Answer 5

1. internal cognitive processes (endogenous attention) mediated by top-down (from higher to lower levels) neural mechanisms (prefrontal cortex and posterior parietal cortex play major roles in directing top-down attention)
2. external events (exogenous attention) mediated by bottom-up (from lower to higher levels) neural mechanisms

Question 6

covert vs overt attention

Answer 6

covert attention: a shift of visual attention without any corresponding eye movement. overt attention: A change in visual attention that involves a shift in gaze.

attentional gaze: the shift in attention from one perceptual object to another
frontal eye field (an area on the ventral surface of the frontal cortex) as important. –> The frontal eye field, which is also active during eye movements, is active during shifts in attentional gaze.

Question 7

cocktail-party phenomenon

Answer 7

is the fact that even when you are focusing so intently on one conversation that you are totally unaware of the content of other conversations going on around you, the mention of your name in one of the other conversations will immediately gain access to your consciousness. This phenomenon suggests that your brain can block from conscious awareness all stimuli except those of a particular kind while still unconsciously monitor- ing the blocked-out stimuli just in case something comes up that requires your attention.

Question 8

neural mechanisms of selective attention

Answer 8

Selective attention works by strengthening the neural responses to attended-to stimuli and by weakening the responses to others . This dual mechanism has been termed a push–pull mechanism.

Question 9

simultanagnosia

Answer 9

disorder of attention: visual-simultanagnosia: a difficulty in attending visually to more than one object at a time. Because the dorsal stream (which includes the posterior parietal association cortex) is responsible for visually localizing objects in space, you may have hypothesized that the patient’s problem was associ- ated with damage to this area. If you did, you were correct. Simultanagnosia is usually associated with bilateral dam- age to the posterior parietal cortex.