Neuro Ch 8

• subjective awareness of ourselves and our surroundings 
• consciousness hard to study, but conscious perception is tractable (and requires attention)

the process of selecting some parts of a scene for more detailed analysis; it improves performance to attended stimuli and interferes with processing unattended stimuli

an inability to detect differences between two similar visual scenes

a failure to detect an otherwise salient stimulus when your attention is focused elsewhere

• only small part of input to retina reaches conscious awareness at any given movement 
• visual consciousness is not passive, but requires us to actively attend our world and select some subset of it for further processing

• attention is described as spotlight that can be moved to different parts of the world, enhancing we can see the spotlight of attention with Posner cueing task perception of whatever is in the spotlight
• Posner cueing task (fixation, cue, fixation, target stimuli, subject response)

• valid trails - participants respond faster: reaction time benefit
• invalid trails - participants respond slower: reaction time cost
• behaviour measure of attention: performance difference between valid and invalid trials

• voluntary attention
• participants must move the spotlight of attention to where the arrow is pointing
• top-down attention: goals motivate us to deliberately focus on something specific

• involuntary awareness
• a sudden flash of light or motion onset can automatically capture attention
• bottom-up attention: attention jumps to unexpected but salient features of the environment

ambiguous figures offer way to study changes of consciousness while keeping sensory stimulus the same

• refers to situation in which the same stimulus can produce more than one types of conscious percept 
• binocular rivalry: happens when a completely different image is presented to each eye

most of the brain is active during most events, isolate response to a cognitive event of interest via subtractive logic

brain activity during cognitive process - brain activity during cognitive process X = brain activity during cognitive process Y

detected change (present in X); person consciously  noticed it (Y) - undetected change = brain activity related to consciously noticing a change

• detected change minus undetected change
• undetected change minus no change

show enhanced activity whether or not a change was consciously detected

show enhanced activity only when a change is consciously detected

increases how long it takes to notice changes and decreases the number of changes detected 

shows how frontoparietal regions is casually related to conscious awareness not just correlated with it

the second stimulus masks the perception of the first 

stimulus not consciously perceived if it is presented very briefly and immediately followed by another stimulus

activity in frontoparietal regions increases during changes in the perceived stimulus though retinal stimulus is always the same

• necessary for conscious perception, damage to them should lead to impairments of awareness
• affect activity of lower level sensory areas, sites of attentional modulation

• syndrome in which the patient is unable to pay attention to, or interact with, stimuli in half of the sensory environment 
• no primary sensory deficits

• extends over multiple sensory modalities (not just vision) 
• neglect even extend to imagined scenes 
• over time, hemispatial neglect turns into a more subtle deficit, extinction

stimulus can be detected when presented alone in the neglected field but is no longer detected when presented simultaneously with another stimulus in the non-neglected field

• we've mostly been talking about externally oriented attention, but attention can also be directed internally to our thoughts or memories 
• e.g. when reflected on things learned during the day 
• lateral brain = external attention 
• medial brain = internal attention

• may represent particular stimulus with an ensemble of neurons.
• Pattern of activity across the population of neuron codes for the stimulus 
• population coding in these lower level sensory areas might be modulated by frontoparietal areas

sensory areas may represent multiple stimuli in the environment at any one time, with different populations of neurons

• different sensory inputs will compete with one another to control behaviour, but their competition can be biased by attention 
• top down control from FPA can be used to bias the competition in visual cortex  (site of attentional modulation)

the neural response is larger than the response to the same stimulus in the absence of attention

the neural response is more selective to the preferred stimulus than it is in the absence of attention

• attentional modulation (gain, sharpening, application of weak stimuli) increase signal to noise 
• the magnitiude of activity elicited for an attended, preferred stimulus will be higher than the baseline firing rate, and more likely to be transmitted downstream to higher order brain areas

• sensory stimuli are primarily represented by population level activity and not individual neurons 
• attention may sculpt patterns of activity, increasing the activity of some neurons and decreasing the activity of others, to emphasise a particular pattern over its competitors

noise correlations

• refers to the simultaneous firing of neurons in two distinct areas, their activity is correlated or coupled 
• important because more likely to respond to coordinated inputs vs those that are uncoordinated

• different aspects of a stimulus are represented in at least partly distinct brain regions somehow be bound in order for us to perceive objects as a whole rather than bundles of features
• synchronization may be mechanism by which the binding problem can be solved

• idea that the body is material where as the mind is spiritual (non material) 
• children lean towards dualism
• fallen out of favour

mental states are defined in terms of the functional role they perform rather than the specific kind of hardware in which they are implemented

• consciousness arises from lower order representation of stimulus, a higher order representation, and a functional link that makes the higher order one about the lower order one 
• issues: what counts a higher order

• conscious experience arises from coordinating the activity of functionally specilised brain areas into an integrated global workspace
• synchronised activity between FPA and lower level and motor areas consistent with this