Attention

Question 1

limits of perception

Answer 1

Inattentional blindness (Simons & Chabris, 1999) - gorilla demo
Change Blindness (Simons & Levin, 1997) - miss slowly changing items in scene
Ambiguous figures (Wittgenstein 1953) duck/rabbit

Question 2

why is perception limited

Answer 2

Concurrent coding across a system of neurons: challenges for putting objects back together and into their correct context (binding problem)
Distributed processing in assemblies - integration over vast distributed network
Competitive processing in neurons (within brain regions there is competition within RFs)
Requires selection and integration
May be some energy limitations

Question 3

what is the classic definition of attention

Answer 3

William James: Classic Definition
Attention is
A process about prioritisation and selection of a single item
It can operate within mental representations
It involves focusing and inhibiting
It is for guiding adaptive behaviour
It is essential for healthy cognition
It is proactive and can anticipate events

Question 4

what is the contemporary definition of attention

Answer 4

Attention refers to the psychological and neural functions for prioritisation and selection of information to guide adaptive behaviour (based on task goal)
Attention benefits and costs can be measured by quantifying the differential processing of the same item as a function of its relevance
Distinct from awareness, thought, will, effort, task-difficulty, motivation, arousal and executive control.

Question 5

what (taxonomical) distinctions have been proposed

Answer 5

Reflexive/involuntary/exogenous vs active/voluntary/endogenous (Posner, Jonides)
Sensorial/external vs intellectual/internal (Chun, Nobre)
Immediate (intrinsic) vs derived (associated)

Question 6

what are important factors in considering the mechanisms of attention

Answer 6

Purpose: performing vs learning (enhance/inhibiting what is relevant for this goal)
Source: perceptual exogenous vs endogenous STM, endogenous LTM
Mode: voluntary vs involuntary
Attribute: spatial, object, feature, temporal, associative, higher order etc
Substrate: early perceptual, late post-perceptual, STM, LTM

Question 7

what is the standard model of attention

Answer 7

sensory processing across the visual hierarchy is modulated based on RF properties (feature analysis of location, object and featurs) this is influences by top-down signals originating in STM (specifically goals)

Question 8

how has it been criticised

Answer 8

attention is broader than what this implies
Top-down signals originate from many time scales
Modulation is not restricted to RF properties, can be based on temporal expectations or higher order attributes (meaning/social constructs)
Prioritisation and selection of information can operate within memory

Question 9

Helmholtz (1867) experimental approach

Answer 9

Developed the first spatial orienting task
Box with peep hole and card covered in different letters, which was briefly illuminated by a spark
Illustrates the limits of perception as cannot see everything on the card
AND our ability to focus at will to items across space to enhance perceptual pickup even in the absence of eye movements
Systematically repeating the task allowed him to reconstruct everything that had been on the card
First demonstration of how directing attention enhances perception

Question 10

The competing streams task (Hillyard, 1978)

Answer 10

Adapted Cherry’s 1953 dichotic listening/ cocktail-party task
Participants monitor one of two competing streams to detect occasional targets embedded among standard stimuli
Task equates for appearance of stimuli as well as state-related variables (arousal, difficulty, fatigue)
Used to see the extent of processing of different types of attributes of stimuli when there is competition and when you focus vs divide attention.
Evaluates what stages modulation takes place
Good for studying neural modulation as it can control for various nuance factors

Question 11

visual search (triesman, 1982)

Answer 11

Provides important information about the nature of limits in capacity
Proposed that spatial attention is necessary for feature integration
Simple features are automatically extracted but when you have to combine or integrate features wilful attention is required

Question 12

spatial orienting task (posner, 1978)

Answer 12

Quantifies the functional consequences of shifting attention voluntarily or reflexively
Can study brain networks involved
Introduced the visual spatial orienting task to investigate how we move attention to spatial locations according to endogenous and exogenous factors
The task manipulates expectation or salience while keeping the goals the same.

Question 13

early theoretical dichotomies

Answer 13

When attention acts (where is the bottleneck)
Early, filtering sensory features (Broadbent, 1958, Triesma, 1960)
Late, gating access to awareness and action (Deutsch & Deutsch, 1963)
What attention acts on
Spatial location (Pavlov, 1927, Sokolov, 1960; Posner, 1978; Triesman & Felade, 1980; Eriksen & Yeh 1985)
Object-based representations (Duncan, 1984; Marshall & Halligan, 1993)

Question 14

current research has resolved these dichotomies how?

Answer 14

Attention modulation can occur at multiple stages of processing depending on task-specific demands
Attention modulation can be based on multiple types of attributes

Question 15

early notions regarding neural control of attention

Answer 15

Orienting refers to how our bodies orient to salient or relevant events
Descartes(1649): voluntary orienting was achieved by shifting the pineal gland
Orienting response:
Pavlov (1927); Sokolov (1960) automatic involuntary orienting toward inherently salient stimuli.
Involves positioning of sensory receptors toward the stimuli
Mediated by increased cortical excitability by the brainstain (reticular activating system

Question 16

what is neglect

Answer 16

lack of awareness for sensory events located towards the contralesional side of space together with a loss of the orienting behaviours, exploratory search and other actions that would normally be directed toward that side (Brain, 1941)

Question 17

what is hemianopia

Answer 17

able to orient to the half that cannot be seen whereas neglect extends to an inability to attend to this side of space

Question 18

how does neglect support a large scale network of attention

Answer 18

The complexity of neglect suggests attention is controlled by a large-scale network of brain areas with different individual contributions, but ultimately working together (Mesulam, 1981, 1990, 1999)
Mental orienting achieved through a distributed system including functionally specialised areas called ‘multimodal critical epicentres’
Parietal cortex highly associated with sensory areas (representation)
Motor areas/ frontal (exploration)
Motivational node in cingulate cortex
Epicentres have local circuits
Subcortical associative areas (striatum, pulvinar) are involved
Spatial orienting system interacts with the Reticular Activating System
Consistent with data regarding which lesions cause neglect as reported by Husain & Rorden (2003) and Karnath et al. (2002)
Associated with white matter links of control areas - have to break ability of system to interact with sensory motor areas

Question 19

what does neglect tell us about attention

Answer 19

Provides the initial knowledge about the brian areas important for the control of spatial attention
Impairments of awareness are separable from sensory deficits in neglect
Multiple spatial frames of reference can be affected, including object-based spatial frames
Multiple lesion sites, including subcortical lesions can lead to neglect

Question 20

brain imaging studies (e.g Corbetta et al., 1993; Nobre et al., 1997; Kim et al., 1999; Silver & Kastner, 2009)

Answer 20

Individual level mapping of the system using PET and fMRI revealed the large-scale network for the control of spatial orienting with increasing refinement and granularity.
The network for spatial orienting bears a close relation to brain areas involved in eye movement control, suggesting a close relationship between these cognitive and sensory-motor functions (although NOT the same)
The network is often referred to as the dorsal frontoparietal network BUT additional areas e.g subcortical structures are also involved

Question 21

Single-unit studies in non-human primates (Colby, 1996)

Answer 21

Show gain of control of neurons in dorsal parietal (e.g LIP) and prefrontal areas (e.g FEF).
LIP maps sensorimotor information in retinotopic coordinates that guide movements
FEF modulated by task-relevance of stimulus ( → attentional modulation)
Shows memory-related and motor-related activity
Neurons often show modulation by attention and eye movements, but there can also be some dissociations
E.g eye movement can occur independently of attention
By recording simultaneously from multiple regions it has been possible to show that the dynamics of attention control is flexible.
Different areas can take the lead depending on the nature of information guiding attention

Question 22

what do microstimulatioin and neural recordings combined show us

Answer 22

Confirm that neurons in dorsal parietal and PF regions can influence activity of neurons in visual areas
These modulations impact task performance
Using non-invasive methods, it is possible to replicate the finding that doral frontal and parietal regions change visual activity
e.g Buschman & Miller 2007
Moore & Fallah 2003

Question 23

Buschman & Miller, 2007

Answer 23

Monkeys had stimulus they had to detect from an array, on some trials this required WM on others this required sensory reasoning (pop out vs search trials)
Recorded simultaneously from LIP, FEF and dorsolateral prefrontal cortex.
Showed different temporal dynamics between the areas when orienting attention based on stimulus-driven (exogenous) and memory-driven (endogenous) factors.
Recorded field potentials and showed synchronisation of neural activity between areas with spatial attention
Suggests frontal lobes are modulating sensory areas - although this is correlational
Simultaneous recording of multiple regions demonstrates flexibility of attentional control within the network.
Different areas can ‘take the lead’ depending on the nature of information guiding attention.

Question 24

Moore & Fallah,2003;2004

Answer 24

Microstimulationed FEF and found systematic and correlated effects upon behavioural and neuronal activity
FEF and V4 share RFs and are connected with feedback
Performance on task depends on amount of stimulation in FEF and V4
Further studies combining microstimulation and neuronal recordings indicate that neurons in dorsal parietal and prefrontal regions can influence activity of neurons in visual areas and that these modulations impact task performance.
Microstimulation of FEF have shown that activity in FEF can directly influence visual processing in ventral visual areas (V4) and behaviour.
The changes in visual activity and behavioural performance are tightly coupled.
animals can also modulate their own behaviour

Question 25

Recordings of field potentails in non human primates | Taylor, Nobre & Rushworth, 2007

Answer 25

How attention related modulations in gamma-band and low-frequency oscillations Theoretical proposal suggest that changes in oscillations can provide a means for the brain to change which neuronal populations are talking to one another and which object features are integrated TMS & ERPs (Taylor, Nobre & Rushworth, 2007) Stimulate FEF (change in saccades) with TMS and found direct effects upon visual components of ERPs Record EEG in attention task Can change visual activity in same area - not produced in control areas Indicating cross communication with modulating effect Repeated with TMS and fMRI

Question 26

What is biased competion theory (desimone & Duncan, 1995)

Answer 26

Prevailing model of attention modulation Holds that competitive interactions between objects/features for neuronal outputs is biassed through both bottom-up(salience) and top-down (goals) mechanisms Attention guides the integration of objects in a self-reinforcing way Overcomes the binding problem Cells with large RFs compete for information processing within cells Feature templates in WM hyper-excite compatible RFs Cells can gain priority through evolution or acquisition

Question 27

what do ERP studies show Voorhis & Hillyard 1977 Mangun et al. 1987

Answer 27

Voorhis & Hillyard, 1977) Reveal sensory modulation Multiple stages of sensory processing are affected and can be modulated in dissociated ways ERPs have tended not to reveal very early modulation of V1 Attended stimuli elicit larger visual potentials than ignored stimuli The first effects occur on potentials generated in extrastriate visual cortex (P1) Posner orienting task (Mangun et al., 1987) Modulation is not localised to one place - different parts of the ERP are differentially modulated depending on task requirements Attention can act at multiple points

Question 28

Brain imaging studies

Answer 28

Tootel et al., 1998) Clearly reveal modulation in sensory areas Competing streams task applied to fMRI Retinotopic waves used to separate out different visual areas Compare observation of the same stimulus with attention directed to different locations Modulation spatially related to attention No temporal resolution in MRI so can’t conclude at what point attention modulates Affects many areas including V1 and the LGN (thalamus) But these modulations could happen early or late (as a consequence of later feedback)

Question 29

neuronal recordings in non-human primates (Moran & Desimone, 1985)

Answer 29

Recorded V2, V4, IT RFs (not V1 as not accessible) - stimulus placed within RFs The same array will produce different response depending on whether the effect stimulus is attended or not Reveal competition for processing within RFs Reveal filtering of unattended information from RFs Does not provide the complete picture of the mechanism for attention modulation there are many additional interesting findings about how neuronal activity is modulated

Question 30

Field potential recordings in non-human primates (Fries et al., 2001)

Answer 30

Reveals changes in oscillatory brain activity by selective attention Investigated effects of selective attention on neuronal oscillations and synchronisation Recorded single-unit activity and field potentials Spatial attention enhances the high-frequency gamma-band activity and increased the synchronisation between spikes This increases the impact of neuronal activity from relevant locations on the next level of hierarchical processing

Question 31

Neuronal recordings supporting proactive anticipation (Chelazzi et al., 1993)

Answer 31

Recorded IT while monkeys had to detect a stimulus presented in a display and make a display When both stimuli were in the RF, the selectively attended desired stimulus produces a large response (opposite for undesirable stimulus) Reveal a bias signal during the interval of stimulus anticipation Neurons that were attuned to a particular stimulus had their baseline activity elevated during the anticipatory period Such increases in baseline activity are proposed to bias sensory processing toward those stimulus Evidence for top-down pre-activation of task relevant locations (or object features/attributes) that would provide a competitive advantage to the coding of these locations (or objects) (the BIAS in biassed competition) The effect may be specific to brain areas that code the type of expectation that is task relevant E.g IT: object-based

Question 32

brain imaging in humans using multivoxel pattern analysis (Stokes et al., 2009)

Answer 32

fMRI study Specific pattern of individual units differ depending on whether we observe an X or O Mapping this enables us to see if an individual anticipating a stimulus is the same as observing it Found that endogenous attention can lead to preactivation of the same neuronal assemblies that code for the perception of the task-relevant expected objects Supports the interpretation that top-down biases act upon perceptual codes to bias bottom-up competitive processes during perception

Question 33

EEG studies in humans (Worde et al., 2000; Gould et al., 2011)

Answer 33

State of anticipation changes oscillatory signals Below frequency oscillations happens at alpha band Amount of alpha desynchronization contrived with amount of anticipation over posterior recording sites Through to reflect excitability in visual areas

Question 34

beyond the standard model

Answer 34

Selective attention is the prioritisation and selection of relevant attributes to guide adaptive behaviour Can use different types of information from different sources to bias processing of incoming sensory signals or stored in memory