PSYC 273 Lecture Notes - Lecture 14: Ventromedial Prefrontal Cortex, Dorsolateral Prefrontal Cortex, Hemispatial Neglect
Chapter 14 Notes
Attention focuses cognitive processing on specific objects.
• Attention: a state or condition of selective awareness or perceptual receptivity, by
which specific stimuli are selected for enhanced processing.
o Overt Attention: attention in which the focus coincides with sensory orientation.
o Covert Attention: attention in which the focus can be directed independently of
sensory orientation.
o Cocktail Party Effect: the selective enhancement of attention in order to filter
out distracters, as you might do while listening to one person talking in the midst
of a noisy party.
• There are limits on attention.
o Shadowing: a task in which the participant is asked to focus attention on one ear
or the other while stimuli are being presented separately to both ears, and to
repeat aloud the material presented to the attended ear.
o Inattentional Blindness: the failure to perceive nonattended stimuli that seem
so obvious as to be impossible to miss.
o Divided Attention Task: a task in which the participant is asked to focus
attention on 2 or more stimuli simultaneously.
▪ Difficult to focus on more than thing and shows that attention is a limited
resource.
o Attentional Spotlight: the shifting of our limited selective attention around the
environment to highlight stimuli for enhanced processing.
o Attentional Bottleneck: a filter created by the limits intrinsic to our attentional
processes, whose effect is that only the most important stimuli are selected for
special processing.
▪ Early Selection Model: unattended information is filtered out right away.
▪ Late Selection Model: important but unattended stimuli many undergo
substantial unconscious processing before suddenly coming to attention.
▪ Current thought is that these models are combined.
▪ Perceptual Load: the immediate processing demands presented by a
stimulus.
Attention may be endogenous or exogenous.
• Sustained Attention Tasks: a task in which a single stimulus source or location must be
held in the attentional spotlight for a protracted period.
• We can choose which stimuli we will attend to.
o Endogenous Attention: the voluntary direction of attention toward specific
aspects of the environment.
o Symbolic Cuing: a technique for testing endogenous attention in which a visual
stimulus is presented and participants are asked to respond as soon as the
stimulus appears on a screen.
• Some stimuli are hard to ignore. (Important changes usually).
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o Exogenous Attention: the involuntary reorienting of attention toward a specific
stimulus source cued by an unexpected object or event.
▪ Considered to be a bottom up process because attention is being seized
by sensory inputs from lower levels of the nervous system.
▪ Peripheral Spatial Cuing: a technique for testing exogenous attention in
which a visual stimulus is preceded by a simple task irrelevant sensory
stimulus either in the location where the stimulus will appear or in an
incorrect location.
• Inhibition of Return: the phenomenon observed in peripheral
spatial cueing tasks when the interval between cue and target
stimulus is 200 ms or more, in which the detection of stimuli at
the former location of the cue is increasingly impaired.
o Normally endogenous and exogenous attention work together to control
cognitive activities.
▪ Ex: squirrel searching for food (endogenous attention) and slight noises
(exogenous attention cues) distracts the squirrel.
• We use visual search to make sense of a cluttered world.
o Feature Search: a search for an item in which the target pops out right away not
matter how many distracters are present because it possesses a unique
attribute. (Ex: Searching for your red car among a bunch of silver cars).
o Conjunction Search: a search for an item that is based on 2 or more features (ex:
size and color) that together distinguish the target from distracters that may
share some of the same attributes. (E: searhig for our fried’s fae i a
crowd= hair, eyes, nose, and smile. Find the green square.) Takes longer than a
feature search.
▪ Binding Problem: the question of how the brain understands which
idiidual’s attributes blend together into a single object when these
different features are processed by different regions in the brain.
o To uncover finer details of attentional mechanisms, neuroscientists use 2 general
experimental strategies:
▪ Consequences of attention: how selective attention to stimuli modifies
brain activity and thus enhances stimulus processing.
• Temporal Resolution: the ability to track changes in the brain that
occur very quickly.
▪ Mechanisms of attention: the brain regions that produce and control
attention, shifting it between different stimuli in different sensory
modalities.
• Spatial Resolution: the ability to observe the detailed structure of
the brain.
The electrical activity of the brain provides clues about mechanisms of attention.
• Event Related Potential (ERP): averaged EEG recordings measuring brain responses to
repeated presentations of a stimulus. Component of this tend to be reliable because the
background noise of the cortex has been averaged out.
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• Distinctive patterns of brain electrical activity mark voluntary shifts of attention.
o P1 Wave: an initial positive wave seen in the ERP after a stimulus is introduced.
o Auditory N1 Effect: a negative deflection of the event related potential occurring
about 100 ms after stimulus presentation that is enhanced for selectively
attended auditory input compared with ignored input.
▪ N1 Wave: follows P1 wave, is much bigger after a stimulus that is being
attended to than a stimulus that was not being attended to.
o P20-50 Effect: a positive deflection of the event related potential, occurring
about 20-50 ms after stimulus presentation, that is enhanced for selectively
attended auditory input compared with ignored input.
o P3 Effect: a positive deflection of the event related potential occurring about 300
ms after stimulus presentation that is associated with higher order auditory
stimulus processing and late attentional selection.
▪ P3 Wave: reflects higher order cognitive processing of the stimuli.
▪ Abnormal P3 responses are found in people with schizophrenia.
o Effects of visual stimuli:
▪ Distinctive changes in the ERP:
• Collect ERP date while doing a symbolic cuing task.
• During task electrodes show enhanced P1: occurs 70-100 ms after
stimulus and carries an increased N1 response afterwards.
o Visual P1 Effect: a positive deflection of the event related
potential occurring 70-100 ms after stimulus presentation
that is enhanced for selectively attended visual input
compared with ignored input.
▪ Only evident in visual tasks involving spatial
attention (where is the target?)
• Enhancement occurs in the contralateral occipital cortex.
• Reflexive visual attention has its own electrophysiological signature.
o Does endogenous attention involve the same brain mechanisms as endogenous
attention?
▪ Endogenous: visual P1 effect is seen in the contralateral ERP.
• Attention affects the activity of individual neurons.
o Affired sustaied attetio tasks.
▪ Ee he the aial’s gaze staed the sae, ut attetio trasferred
to a new object— the activity of the neuron changed.
▪ Showed that:
• The stimuli are identical in both conditions.
• The fixation poit had’t haged.
• The same cell was being recorded in both conditions.
Many brain regions are involved in processes of attention.
Pulvinar, Superior Colliculus, Reticular Activating system, thalamus.
• 2 subcortical systems guide shifts of attention.
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