Invariance of primate object recognition

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Invariance of primate object recognition
FIAS
By Thomas Weißwange
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Outline

• Introduction - Inferotemporal Cortex and Object
  Vision
• Ventral visual pathway
• Feature recognition cells in TE
• Afferents to TE
• Organisation of TE
• Receptive fields of IT/STS-neurons
• Crowding and Familiarity
• Conclusion

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Introduction Ventral Visual Pathway
Quelle http//thebrain.mcgill.ca
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Introduction - Feature Recognition

• Specific Stimuli Selection
• Large receptive field including the fovea
• Orientation-sensitivity
• Size-dependent and independent cells

Orientation
Size
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Introduction - Feature Recognition

• Trained monkeys have more representations of the
  trained stimuli
• They can also develop cells responsible for
  associative pairs

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Introduction TE-Afferents

• Few feature-cells also in TEO and V4
• Various levels of complexity
• Cells from TEO projects only on to small focussed
  areas of TE

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Introduction - Organisation of TE

• Columnar organisation (Respond to same Stimuli)
• Maximal response at slightly different stimuli
• Different features stimulate overlapping regions

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Introduction - Organisation of TE

• A feature is represented by a whole column
• -gt Large invariances through differences inside
  the column
• -gt High discrimination through single-cell-respons
  e
• -gt By overlappings the discrimination acuity can
  be very high

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Receptive Fields of IT/STS-Neurons

• The problem of multiple objects
• Influences of attention
• Natural scenes

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Receptive Fields of IT/STS-Neurons

• Firing rate at fixation does not change much
  (Background Invariance, Association
  Invariance)
• Receptive field size differs with background

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Receptive Fields of IT/STS-Neurons

• Attention only has an effect on the receptive
  field
• A second stimulus decreases field size

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Crowding and Familiarity

• Crowding
• Impairement of recognizability by neighbouring
  objects within a critical spacing
• Familiarity
• Context dependent improvement/impairment of
  recognizability

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Crowding and Familiarity
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Crowding and Familiarity

• Critical spacing increases with eccentricity,
  independent of size
• Critical spacing is roughly half of the
  eccentricity

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Crowding and Familiarity

• Context improves recognition at low, hinders at
  high eccentricities
• Crowding has a bigger impact on recognition than
  familiarity

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Conclusion

• Invariance of Object Recognition originate from
  groups of neurons with similar specific stimuli
  but differences in attributes of those
• Receptive fields depend on backgrounds
• Object Recognition depends on feature-context

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Quellen

• K. Tanaka, Inferotemporal Cortex and Object
  Vision, Annu. Rev. Neurosci., 1996
• E.T. Rolls et al., The Receptive Fields of
  Inferior Tempral Cortex Neurons in Natural
  Scenes, J. Neurosci., 2003
• M. Martelli et al., Are faces processed like
  words? A diagnostic test for recognition by
  parts, Journal of Vision, 2005.

Thank you for your attention