week 10 Flashcards
(20 cards)
Attention = Selection
Multiple sources of sensory information (colour, shape, sounds, smells, etc) compete with each other
A need to prioritise sensory information according to relevance (e.g. current goals)
Both selection processes attention
Effects of attention
In 1890, William James wrote that attention helps to:
perceive
conceive
distinguish
remember
shorten reaction time
Hillyard (1973) Dichotic Listening Experiment
N1 Event-Related Potentials for attended stimuli were larger in amplitude than when they were not being attended to/ignored.
When a stimulus appears in focus of attention, increased visual P1.
Attention to specific stimulus properties enhances later ERP components
P3: linked to attentional engagement and higher-order cognitive processing of a stimulus
Stimuli appearing in field of attention affect early sensory areas
Tones in the attended ear evoke larger magnetic brain responses (magnetoencephalography; MEG) than unattended tones in auditory cortex as early as 20 msec post stimulus.
Why study the effects of attention on the brain?
At what stage is information filtered? Where we see modulation in the brain suggests early or late selection
Early sensory areas (e.g. V1 and A1) suggests early selection
Higher brain areas suggests late selection
Brain imaging (fMRI/MEG) & behaviour after brain damage:
assess which perceptual/ cognitive processes may be affected (i.e., where in the brain)
Changes in measurements (e.g., enhanced/suppressed processing) provide insight into how
Time-sensitive recordings (EEG/MEG/single cell recordings):
can help assess when
Selective attention effects on single neuron activity
Macaque monkey trained to covertly attend stimuli.
Activity recorded in visual neuron that responds to red stimuli; receptive field covers both red and green targets.
Attention to specific properties changes activity later in visual stream
O’Craven et al. 1999 fMRI study
Presented faces overlaid on houses
By changing instruction to attend to the faces and ignore the houses, and vice versa, found ↑ activity in different areas of cortex:
The question of early vs. late selection
Electrophysiology; early comes before late
fMRI; early is early sensory areas late is parietal, temporal and frontal cortex
Emerging consensus: both early and late selection can occur depending on task/stimulus demands; not mutually exclusive (Lavie and Tsal 1994; Vogel, Woodman, and Luck 2005; Yantis and Johnston 1990).
BUT a strong case against pure late selection theories.
How is Attention Directed?
Informed by studies of patients with focal brain damage and cell recordings in animals.
An orienting network: responsible for moving the focus of attention.
disengaging attention (parietal cortex),
moving attention to a new target (superior colliculus)
engaging attention with the new target (the pulvinar).
An alerting network: detects salient events and prepares motor responses.
An executive network: sustains attention and resolves conflict
The superior colliculus guides attentional eye movements
Subcortical effects of attention too
Sustained attention – e.g., tracking moving stimuli – can increase activity in structures before the visual signal meets primary visual cortex
The pulvinar drives shifts of attention (engagement)
Reducing/increasing pulvinar activity with GABA agonists/antagonists disrupts/enhances covert orienting of attention to targets (Robinson & Petersen 1992)
Helps filter out distracting stimuli
Attentional disorders arising from parietal damage
neglect- A disorder of space-based attention. An inability to process and perceive (i.e., ignorance to) stimuli to one side of the centre of gaze (contra-lesional side). Neglect can be object-centred.
extinction-Attentional bias. Detection of stimuli on the ipsi-lesional side (usually right) overrules detecting simultaneous stimuli on the contra-lesional side (usually left)
Balint’s syndrome-A disorder of object-based attention. Dramatic narrowing of attentional spotlight + spatial disorientation.
Bálint’s Syndrome
Difficulty steering gaze toward specific targets (oculomotor ataxia) and accurately reach for them (optic ataxia)
Simultanagnosia: Difficulty attending to more than one object at a time
Implications for the role of the parietal cortex in attention
These syndromes suggest that the parietal lobes help to link perception and action, and assign importance (or ‘interest’) to the contralateral space
Parietal lobe guide shifting/orienting of attention (Posner & Peterson, 1990).
Cortical attention networks
The parietal cortex is important for directing attention
A dorsal fronto-parietal network for voluntary, top down control of attention
A ventral temporo-parietal network for reflexive attention orienting
How is Attention Directed 2
Frontoparietal network: Voluntary, top-down control of attention
lateral intraparietal (LIP) cell activity in monkeys correlated with direction of attention; visual or auditory
↑ fMRI activity in human equivalent, intraparietal sulcus (IPS), when covert attention is directed
Frontal Eye Fields – directs gaze in line with task demands
Temporoparietal Network: Reflexive, bottom-up attention
Automatic steering of attention to novel/unexpected stimuli
Temporoparietal (TPJ) junction – ↑ activity like an alerting signal;
TPJ damage: poor responses to unexpected stimuli
Input from ventral frontal cortex involved in working memory
Prefrontal Top-Down Control
Top-down control of attention
Use previously acquired internal information (e.g., in working memory; abstract rules/knowledge) to:
select a goal
plan corresponding actions
stay ‘on task’ while achieving it
High-level influence on attentional processing
Executive attention network
Anterior Cingulate, Medial Frontal Cortex and Lateral Prefrontal Cortex
Underlies the capacities to:
Use relevant information
Ignore irrelevant information
Resolve conflicts between competing information
Where ADHD fits in?
Attention Deficit Hyperactivity Disorder: difficulty with directing sustained attention and higher impulsivity
Biological basis unclear but is often associated with:
Slightly ↓ brain volume (~ 3-4% smaller than unaffected children), partic. cerebellum and frontal lobes
Symptom reduction with drugs which inhibit dopamine/norepinephrine neurotransmitters (e.g., methylphenidate, “Ritalin”); main cortical pathways are in the frontal lobes
Hypoactivity in lateral prefrontal cortex
Attentional control: individual differences
Trait variation in prefrontal attentional control related to range of psychological and behavioural profiles.
Default mode: the ‘anti’-attention network…?
Default-mode network ‘anti-correlated’ with attention tasks.
Often thought of as off-task
Hyperactivation of DMN in ADHD (Rubia, 2018)
Associated with internally-directed attention
