Week 8-Attention part 2 Flashcards
What is the neuroscience of attention?
-Behavioural cognitive psychology is essential for the study of attention and has generated many testable hypotheses.
-Studies assessing Reaction Times and accuracy cannot fully describe the neural mechanisms of attention, as they depend on relatively independent measures of cognitive phenomena
-With the development of neuroscientific methods, we can understand what happens in the brain (i.e. at what time, at what intensity and at which level) when we direct the focus of our attention on certain stimuli (focus today is how attention affects sensory inputs in the brain?)
-Attention works by altering neural activity in sensory information/tasks (focus on target/suppress distracting stuff)
What is the Neural Representation Hypothesis?
-Representations are not created equally
-Neural representations of relevant sensory information are enhanced relative to representations of irrelevant sensory information (i.e., filters out distracting stuff)
Neural measures to assess indifferent ways the brain measures stimuli:
-Spike rate, local field potential
-Event-related potentials, spectral power
-BOLD signal (Blood)
-These all reflect neural representations of sensory information and thus can be used to assess attentional modulation
What is the Dual mechanism model?
Selective attention is accomplished through the interplay (i.e., working together) of two mechanisms (key to understanding attention):
1. Target Enhancement: enhancing (increase) neural activity associated with relevant information (makes sense as we want to pay attention to this)
2. Distractor Suppression: suppressing neural activity associated with irrelevant information (this is when we want to focus on something)
-Suppression may function as a compensatory mechanism to target enhancement
-Selective attention helps visual processing by enhancing the cortical representations of behaviourally relevant stimuli (targets) while suppressing the representations of irrelevant stimuli (distractors)
How does the brain control the modulation of brain activity to allow selective attention?
-There are specific sets of (higher level control) regions that control and coordinate attention modulation
-Involvement and interaction of such regions can be measured with neuroscientific techniques (fMRI, EEG, TMS..) and clinical observations (e.g. brain damaged individuals)
What occurs when the stimulus (target) is the focus of attention?
-There is an enhanced amplitude of sensory VEPs components, with very little change in waveform (latency) or scalp distribution. (Eason et al., 1969)
-First EEG study in this area (to see what happens in the brain in response to a specific event, averaging these points out)
-Wanted to see if there’s a difference in the peaks when someone is paying attention or not
-If the target is in an area where attention is not being paid to, it is still processed but there is a smaller peak (i.e., there is a difference in our brain amplitude waves in whether we pay attention or not)
What evidence is there for Target-related enhanced activity? (Hopfinger et al., 2000)
-fMRI evidence
-Spatial attention enhances activity in the visual cortex contralateral to the attended target
-Attention effects on target processing result from a gain-control mechanism that enhances the excitability of extrastriate neurons coding attended regions of visual space (shows that there’s increases in activity in the extrastriate cortex contralateral to the… CHECK RECORDING)
What evidence suggests Target-related enhanced activity is retinotopic? (Heinze et al., 1994)
-With bilateral stimuli in the upper visual field…
-Retinotopically enhanced activation not only contralateral to the target but also in the ventral part of the occipital cortex
-PET evidence
-Confirmed EEG - enhanced P1 amplitude contralateral to the target
What evidence suggests evidence for Multiple Spotlights of Attentional Selection? (McMains et al., 2004)
Hypothesis+predictions:
-Testing a single spotlight moving in a visual field but what if there are more than one?
-Zoom lens type of attention (a little to the side or both needed) OR you split it e.g., one spotlight on one thing and something for the other
Procedure:
-Attend 1 task P’s was asked to find the word or something different from the rest of stimuli. Attend 2 P’s asked to pair same stimulus on the screen (recording brain activity)
Findings:
-Evidence for enhanced activation of the multiple spotlights of attention (or split focal attention) model
-Found attention is split into multiple parts and where P was attending to saw the visual activation
-Shows attention works as a multiple spotlight otherwise you’d see activation everywhere rather than where the person is looking to
What evidence suggests there is attention activity in the Lateral Geniculate Nucleus (LGN)? (O’Connor et al., 2002)
-Spatial attention modulates activity as early as the
Lateral Geniculate Nucleus.
-The LGN, traditionally viewed as the gateway to
visual cortex, may also serve as a ‘gatekeeper’ in controlling attentional response gain.
-Found that at early stages of LGN (before info gets sent for higher processing) there is enhanced activation for the object you want to pay attention to AND for what you are trying to suppress (i.e., distract away from focus)
What evidence suggests attention modulation for nonspatial features? (Anllo-Vento et al., 1998)
-Stimulus always at the same location where the task is to attend to colour e.g., red or blue
-Found you get this peak of the EEG when you are attending to colour (i.e., other features) regardless of whether the object appears
What evidence suggests attention modulation for nonspatial features? (Craven et al., 1997)
-The medial superior temporal part of the brain are sensitive to coherent motions of dots (i.e., moving dots)
-P’s presented with stationary black dots and white motioned dots moving towards fixation cross and asked to look at just one to shift attention (recorded level of activity in V5)
-Every time they attended to moving dot there was enhanced activity whereas for stationary one there was evidence of suppression activity
What evidence suggests that there is evidence for attention modulation on object processing? (Wojciulik et al., 1998)
-Object-Based attention. Covert attention modulates face-specific activity in the human fusiform face area (FFA)
-Dependent on trial, they were asked to match the houses, bars or faces for similarity
-If attention was directed to faces, FFA was very responsive to this. If attention was directed to house the para (CHECK RECORDING FOR NAME)
What Evidence is there for Target Enhancement & Distractor Suppression in the FFA? (O’Craven et al., 1999)
- FFA and PPA show greater signal when the area’s preferred stimulus was attended
- FFA and PPA show greater response to preferred stimulus when it was the irrelevant attribute of the
attended object
Two- Attention-Systems Model of Attention Control: What areas are involved in the Dorsal Attention System? (Maurizio et al., 2002; Vossel et al., 2014)
- FRONTO-PARIETAL NETWORK: (including Dorsal – Medial Prefrontal Cortex and intra-Parietal Sulcus-located in the parietal lobe)
- TOP-DOWN CONTROL: Attention is controlled by the individual’s expectations, knowledge and goals. aka ENDOGENOUS ATTENTION
Two- Attention-Systems Model of Attention Control: What areas are involved in the Ventral Attention System? (Maurizio et al., 2002; Vossel et al., 2014)
- TEMPORO-PARIETO-FRONTAL NETWORK:(including Temporo-Parietal Junction and Inferior Frontal Cortex, IFG IFJ)
- BOTTOM-UP CONTROL: Attention is driven and triggered by an unexpected, and potentially important, stimulus (e.g., a waiter smashing a glass) aka EXOGENOUS ATTENTION
