Movimento complesso flusso ottica
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Movimento complesso: flusso ottica. Lettura. Morrone, M.C., Burr, D.C., and Vaina, L. (1995). Two stages of visual processing for radial and circular motion. Nature 376 , 507-509.

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Movimento complesso flusso ottica

Movimento complesso: flusso ottica


Lettura

Lettura

  • Morrone, M.C., Burr, D.C., and Vaina, L. (1995). Two stages of visual processing for radial and circular motion. Nature376, 507-509.

  • Morrone, M.C., Tosetti, M., Montanaro, D., Burr, D.C., Fiorentini, A., and Cioni, G. (2000). A cortical area that responds specifically to optic flow, revealed by function Magnetic Resonance Imaging. Nature Neuroscience3, 1322-1328.

  • d'Avossa, G. et al. (2007). Spatiotopic selectivity of BOLD responses to visual motion in human area MT. Nat Neurosci 10, 249-255.


Neural response in mstd duffy wurtz 1991

Neural response in MSTdDuffy & Wurtz, 1991


Psychophysical evidence for detection of optic flow in humans

Psychophysical evidence for detection of optic flow in humans?


Spatial summation

Spatial summation


Signal to noise predictions

Signal-to-noise Predictions

  • S α Nsectors

  • σ2α Nsectors σα √Nsectors

  • S/σα √Nsectors


Spatial summation in noise

Spatial summation in noise


Signal to noise predictions1

Signal-to-noise Predictions

  • S α Nsectors

  • σ2= k (constant)

  • S α Nsectors


Spatial summation of contrast

Spatial summation of contrast


Two stage motion analysis

Σ

Two-stage motion analysis

Local motion detectors

Contrast thresholded

Complex motion

integrator


Spatial summation of contrast in noise

Spatial summation of contrast in noise


Spatial summation of contrast in noise1

Spatial summation of contrast in noise


Temporal summation of contrast sensitivity

Temporal summation of contrast sensitivity


Motion c oherence sensitivity

10 secs

Motion coherence sensitivity

signal

noise


Summation constants

Summation constants


Movimento complesso flusso ottica

Segmentation has different temporal integration.

Even a weak signal embedded in noise can be seen given a long enough view


Summation with large fields

Summation with large fields


Summation with large fields in noise

Summation with large fields in noise


Spatial summation for flow is extensive

Spatial summation for flow is extensive


Spatial summation of contrast sensitivity of sinusoids anderson and burr 1987

Spatial summation of contrast sensitivity of sinusoidsAnderson and Burr, 1987


Interim conclusions

Interim Conclusions

There exists psychophysical evidence for detectors tuned to complex optical flow.

Evidence suggest that the detectors are “second-stage” after contrast thresholding.

Temporal summation is extensive: ~ 3 sec.

Spatial summation is extensive, ~ 70°.


A neural centre for optic flow

A neural centre for optic flow?


How functional magnetic resonance imaging fmri works

Brain

Physics

Increased brain activity

Oxygenated and De-

produces a local increase

oxygenated blood have

in blood oxygenation

different magnetic properties

MR images are brighter where there

is greater brain activity

How Functional Magnetic Resonance Imaging (fMRI) Works:


Unfolding

Superior

Posterior

Superior

Lateral

Unfolding

1 cm


Expanding ring

V1

Expanding ring

V2

V3


Rotating wedge

V1

Rotating wedge

V2

V3


Mt v1

MT V1


Demo in dos

Demo in dos

Dos Demo


Movimento complesso flusso ottica

FLOW (30 s) NOISE (30 s)

2 s

2 s

Inverting Direction

2 s

2 s

Rotation

Radial

Translation


Movimento complesso flusso ottica

MT

a

Inverting Rotation / Inverting Noise

d

e

b

Continuous Rotation / Noise

Response

f

c

Gradually Changing Flow / Noise

MC

Time (s)


Movimento complesso flusso ottica

Translation

Flow

SB


Spatiotopic coding of visual motion in human mt

Spatiotopic coding of visual motion in human MT


Movimento complesso flusso ottica

Motion signals integrate spatiotopically across saccades

Two motion signals separated by delay

Melcher & Morrone

Nat. Neurosc. 2003


Movimento complesso flusso ottica

Summation of motion signals

Two motion signals

separated by delay

one fixation

Percent correct

two different fixations


Movimento complesso flusso ottica

Integration of motion at threshold across saccades is spatiotopic

Where in the human brain does the spatiotopic integration occur?


David hubel and torsten wiesel spatially localized receptive fields in primary visual cortex

David Hubel and Torsten Wiesel:Spatially localized receptive fields in primary visual cortex

Cortex

Cortex


Movimento complesso flusso ottica

RETINOTOPIC MAP

Monkey anatomy

Tootel et al, Science, 1982


Retinotopic visual areas

‘Retinotopic’ visual areas

RETINOTOPIA: Neuroni vicini della retina poiettano a

Neuroni vicini della corteccia


Movimento complesso flusso ottica

Each visual brain area contains a map of the visual world and performs a different function.


Movimento complesso flusso ottica

S1 S2 S3 S4


Human mt complex

FLOW - NOISE

Left

Hemisfere

Left VF – Right VF

15˚

4.5˚

-4 0 4

GDA

Human MT complex


Movimento complesso flusso ottica

Response is specific to controlateral stimuli


Movimento complesso flusso ottica

V1

No modulation of response by gaze


Movimento complesso flusso ottica

MT: Strong modulation of response by gaze


Gaze modulation of mt and v1

Gaze modulation of MT and V1

Central target

Eccentric target

D’Avossa et al.

Nat. Neurosc. 2007


Block design spatial selectivity with eccentric fixation

7 deg

2X8deg

S1 S2 S3 S4

Block design: spatial selectivity with eccentric fixation

F0

F1

F2

D’Avossa et al.

Nat. Neurosc. 2007


Spatial selectivity with central fixation

Spatial selectivity with central fixation


Spatial selectivity of bold responses in hmt is modulated by eye position

Spatial selectivity of BOLD responses in hMT is modulated by eye position

D’Avossa et al.

Nat. Neurosc. 2007


Spatial selectivity of hmt is invarient in external but not retinal coordinates

Spatial selectivity of hMT is invarient in external but not retinal coordinates.

D’Avossa et al.

Nat. Neurosc. 2007


Spatiotopicity of v1 and mt

Spatiotopicity of V1 and MT

D’Avossa et al.

Nat. Neurosc. 2007


Movimento complesso flusso ottica

Left MT


Indexes

Indexes


Movimento complesso flusso ottica

Fig1


Movimento complesso flusso ottica

Fig 2


Movimento complesso flusso ottica

Fig 3


Movimento complesso flusso ottica

Fig 4


Conclusion

Conclusion

A specific portion of the hMT complex shows spatiotopic tuning, suggestion that the transformation from retinal to external coordinates may occur within this structure.

The spatiotopicity requires attention.


Experiment in dos

Experiment in dos

Biological motion


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