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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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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




Signal to noise predictions
Signal-to-noise Predictions humans?

  • S α Nsectors

  • σ2α Nsectors σα √Nsectors

  • S/σα √Nsectors



Signal to noise predictions1
Signal-to-noise Predictions humans?

  • S α Nsectors

  • σ2= k (constant)

  • S α Nsectors



Two stage motion analysis

Σ humans?

Two-stage motion analysis

Local motion detectors

Contrast thresholded

Complex motion

integrator





Motion c oherence sensitivity

10 secs humans?

Motion coherence sensitivity

signal

noise



Segmentation has different temporal integration. humans?

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






Interim conclusions

Interim Conclusions humans?

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°.



How functional magnetic resonance imaging fmri works

Brain humans?

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 humans?

Posterior

Superior

Lateral

Unfolding

1 cm


Expanding ring

V1 humans?

Expanding ring

V2

V3


Rotating wedge

V1 humans?

Rotating wedge

V2

V3


Mt v1
MT V1 humans?


Demo in dos
Demo in dos humans?

Dos Demo


FLOW (30 s) NOISE (30 s) humans?

2 s

2 s

Inverting Direction

2 s

2 s

Rotation

Radial

Translation


MT humans?

a

Inverting Rotation / Inverting Noise

d

e

b

Continuous Rotation / Noise

Response

f

c

Gradually Changing Flow / Noise

MC

Time (s)


Translation humans?

Flow

SB



Motion signals integrate spatiotopically across saccades humans?

Two motion signals separated by delay

Melcher & Morrone

Nat. Neurosc. 2003


Summation of motion signals humans?

Two motion signals

separated by delay

one fixation

Percent correct

two different fixations


Integration of motion at threshold across saccades is s humans? patiotopic

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: humans? Spatially localized receptive fields in primary visual cortex

Cortex

Cortex


RETINOTOPIC MAP humans?

Monkey anatomy

Tootel et al, Science, 1982


Retinotopic visual areas
‘Retinotopic’ visual areas humans?

RETINOTOPIA: Neuroni vicini della retina poiettano a

Neuroni vicini della corteccia



S1 S2 S3 S4 and performs a different function.


Human mt complex

FLOW - NOISE and performs a different function.

Left

Hemisfere

Left VF – Right VF

15˚

4.5˚

-4 0 4

GDA

Human MT complex


Response is specific to controlateral stimuli and performs a different function.


V1 and performs a different function.

No modulation of response by gaze


MT: Strong and performs a different function.modulation of response by gaze


Gaze modulation of mt and v1
Gaze modulation of MT and V1 and performs a different function.

Central target

Eccentric target

D’Avossa et al.

Nat. Neurosc. 2007


Block design spatial selectivity with eccentric fixation

7 deg and performs a different function.

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 and performs a different function.


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 retinal coordinates.

D’Avossa et al.

Nat. Neurosc. 2007


Left MT retinal coordinates.


Indexes
Indexes retinal coordinates.


Fig1 retinal coordinates.


Fig 2 retinal coordinates.


Fig 3 retinal coordinates.


Fig 4 retinal coordinates.


Conclusion
Conclusion retinal coordinates.

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 retinal coordinates.

Biological motion


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