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Attention. Squire et al Ch 48. Can you elaborate more on statistical decision theory for control of movement by giving an example? Prior: P(state)-memory Likelihood: P( data|state )-sensory data Posterior: P( state|data )

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Attention

Squire et al Ch 48


Can you elaborate more on statistical decision theory for control of movement by giving an example?

Prior: P(state)-memory

Likelihood: P(data|state)-sensory data

Posterior: P(state|data)

In an example of movement control, is state the desired position, data the current position? So the nervous system

would try to compute the posterior: given current position, what's the probability of desired position.

(b) I wonder how is this posterior implemented in motor system, and where could this be computed.

(c) What's the role of loss function?

What is the timeline for developmental plasticity for learning movements? Are there clear points in childhood

and/or adolescence where plasticity greatly decreases?

1). About visuomotor plasticity in development: are there any motor skills that must be learned in early childhood,

that otherwise would be extremely difficult to learn in adulthood? And why? (phoneme pronunciation? basketball tricks?)

2). Attention and gaze. When the subject is blanking/absent-minded, How does his/her gaze look like? Any fixation?

Especially in driving.

The strength of Fitt’s law and the plasticity of the visuo-motor system seems contradictory. I would expect that

Fitt’s law could be easily violated with training. Or, is it unlikely to see improvement in basic movements like moving

the hand forward on a single plane?

Regarding eye-hand coordination, while watching shoppers remove items from a shelf, the hand closely follows

the eyes until the actual moment of grasping the object. As the hand approaches the target the eyes tend to focus

in another location, usually directly forward in the field-of-vision. The hand movements are generally successful without

the overt visual attention. Could this be evidence of “reverse covert attention”? Meaning that the eyes have moved

overtly, yet the visual system is covertly still on the last position to help guide the hand?

It is commonly believed that seeing a word, for a native speaker, activates comprehension, implying that attention is

automatic. Are there ways of isolating the region or regions associated with the conceptual response to visual stimuli.

For example words vs. nonsense words or drawing of animals with specific common names vs. nondescript.


Visuo control of movement by giving an example? -motor coordination; Held & Hein

Language learning: critical period??? Production and perception.

Motor skills: Rosenbaum – performance depends on practice.


Attention is a hypothetical internal variable control of movement by giving an example? with limited/no explanatory power.

Central idea: selection – of stimulus and action

Also: resource limitations – not necessarily a problem, but an inevitable aspect

of goal directed behavior. Ie it wouldn’t help if we were able to process more

information – however, learning allows more compact codes.

Potential role of basal ganglia:


  • Spatial Neglect: lesions of parietal lobe, the control of movement by giving an example? frontal lobe, anterior cingulate cortex

  • profound inability to attend to certain spatial regions

  • Subcortical level - lesions of the basal ganglia or of the pulvinar

  • thalamic nucleus, which is heavily connected with the parietal cortex

  • Not sensory or motor: failure to select – therefore thought of as attentional deficit.

Neglect may be object centered (above), eye centered, gaze centered, or body centered

Affects imagined images.

Extinction: image on good side suppresses image on bad side

Note other disorders of attention: schizophrenia (disordered eye movements), ADD


Fronto control of movement by giving an example? -parietal network: FEF (frontal eye fields), SEF (supplementary eye fields,

and SPL (superior parietal lobule) Note similarity of areas involved in eye movements and attention. Note also, not just spatial attention but attention to objects and features.


Feedback from control of movement by giving an example? fronto-parietal network affects responses of cells in visual cortex.


Event related potentials ERP’s evoked control of movement by giving an example? in visual cortex recorded on scalp when attending right or left


Fronto control of movement by giving an example? -parietal attentional control system (LIP/FEF)

Cells in LIP do not

respond to steady

stimuli

Cells respond to behaviorally relevant

stimuli


LIP cell responses modulated by reward control of movement by giving an example?

towards

Different reward probabilities

away

LIP cell responds when relevant cue is

in receptive field and when left hand

is used.

Ie modulated by task and hand


Summary: multiple influences on goal ( control of movement by giving an example? attentional) selection in LIP


Microstimulation control of movement by giving an example? of FEF modulates response to visual stimulus in V4

Response of a single V4 neuron with (gray) and without (black) FEF microstimulation


Has attention been shown to control of movement by giving an example? affect background spike rate (i.e decreasing noise and

increasing the contrast of a response to the stimulus) or just to increase the magnitude

of the response to the attended stimulus?

Do I understand correctly that attention is thought to bias the responses in the visual

pathway as low as V1 and LGN?


LGN receives control of movement by giving an example? input from multiple sources including striate cortex, the thalamic

reticular nucleus (TRN), and the brain stem. (plus retina)

The LGN therefore represents the firststage in the visual pathway at which

cortical top-down feedback signals could affect information processing.

fMRIexpts show attentional modulation of LGN (even stronger than attentional

effects in early visual areas.


Attentional control of movement by giving an example? capture or popout

Where are the bottlenecks? What is the nature of the limitation???


Bayesian Approach: control of movement by giving an example?

Cueing effect in Posner paradigm without enhanced processing at attended location.

Eckstein et al, 2002.


Greater prior control of movement by giving an example? liklihood of stimulus at cues location leads to

better performance (detectability).


Search Templates control of movement by giving an example?

Classification Image Technique:

Subject detects a signal in noise

Sort out the False Alarm trials

Add all the images that resulted in false alarms

Reveals the information that led to a false alarm.

Cf reverse correlation technique


Simulation results using classification images control of movement by giving an example?


Classification images from simulations using different control of movement by giving an example?

filters in cued and uncued locations.


Classification images from subjects in Posner experiment. control of movement by giving an example?

Supports Bayesian interpretation of performance, not use of different filters in cued and uncued locations.


Biased competition control of movement by giving an example?


  • What is attention? control of movement by giving an example?

  • Capacity to select information from the environment and select actions to

  • perform

  • Substantial overlap between circuitry for eye movements and circuitry for

  • spatial attention.

  • Parietal – frontal network influences visual cortical areas including V1.

  • LGN may gate incoming visual signals.

  • Attention appears to act in a way that biases competition between stimuli

  • within a receptive field.

  • Attention is limited - why?

  • Limitations may derive from multiple levels of processing in the brain

  • eg sensory, motor, and sub-cortical circuitry such as basal ganglia.


Change Blindness control of movement by giving an example? : insensitivity to changes in visual scenes made

during an eye movement/transient occlusion.

Change blindness challenges idea that perception delivers a

comprehensive representation of world.

What is represented? Attended objects/regions of central interest?


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