Invariance of primate object recognition

FIASFIAS

By Thomas WeißwangeBy Thomas Weißwange

OutlineOutline

► Introduction - Introduction - InferotemporalInferotemporal Cortex and Object Cortex and Object VisionVision Ventral visual pathwayVentral visual pathway Feature recognition cells in TEFeature recognition cells in TE Afferents to TEAfferents to TE Organisation of TEOrganisation of TE

► Receptive fields of IT/STS-neuronsReceptive fields of IT/STS-neurons

► Crowding and FamiliarityCrowding and Familiarity

► ConclusionConclusion

Introduction – Ventral Visual Introduction – Ventral Visual PathwayPathway

Qu

elle

: http

://thebra

in.m

cgill.ca

Introduction - Feature Introduction - Feature RecognitionRecognition

► Specific Stimuli Specific Stimuli SelectionSelection

► Large receptive field Large receptive field including the foveaincluding the fovea

►Orientation-Orientation-sensitivitysensitivity

► Size-dependent and Size-dependent and –independent cells–independent cells Orientation Size

Introduction - Feature Introduction - Feature RecognitionRecognition

►Trained monkeys have more Trained monkeys have more representations of the trained stimulirepresentations of the trained stimuli

►They can also develop cells They can also develop cells responsible for associative pairsresponsible for associative pairs

Introduction – TE-AfferentsIntroduction – TE-Afferents

► Few feature-cells Few feature-cells also in TEO and V4also in TEO and V4

► Various levels of Various levels of complexitycomplexity

► Cells from TEO Cells from TEO projects only on to projects only on to small focussed small focussed areas of TEareas of TE

Introduction - Organisation of Introduction - Organisation of TETE

► Columnar Columnar organisation organisation (Respond to same (Respond to same Stimuli)Stimuli)

► Maximal response at Maximal response at slightly different slightly different stimulistimuli

► Different features Different features stimulate overlapping stimulate overlapping regionsregions

Introduction - Organisation of Introduction - Organisation of TETE

►A feature is represented by a whole A feature is represented by a whole columncolumn

->-> Large invariances through differences inside the Large invariances through differences inside the columncolumn

->-> High discrimination through single-cell-response High discrimination through single-cell-response

->-> By overlappings the discrimination acuity can be By overlappings the discrimination acuity can be very highvery high

Receptive Fields of IT/STS-Receptive Fields of IT/STS-NeuronsNeurons

► The problem of The problem of multiple objectsmultiple objects

► Influences of Influences of attentionattention

►Natural scenesNatural scenes

Receptive Fields of IT/STS-Receptive Fields of IT/STS-NeuronsNeurons

► Firing rate at fixation Firing rate at fixation does not change does not change much much („Background („Background Invariance“, Invariance“, „Association „Association Invariance“)Invariance“)

► Receptive field size Receptive field size differs with differs with backgroundbackground

Receptive Fields of IT/STS-Receptive Fields of IT/STS-NeuronsNeurons

► Attention only has an effect on the receptive fieldAttention only has an effect on the receptive field

► A second stimulus decreases field sizeA second stimulus decreases field size

Crowding and FamiliarityCrowding and Familiarity

►Crowding:Crowding: Impairement of recognizability by Impairement of recognizability by

neighbouring objects within a „critical neighbouring objects within a „critical spacing“spacing“

►Familiarity:Familiarity: Context dependent Context dependent

improvement/impairment of recognizabilityimprovement/impairment of recognizability

Crowding and FamiliarityCrowding and Familiarity

thin

or

fat

Crowding and FamiliarityCrowding and Familiarity

► Critical spacing Critical spacing increases with increases with eccentricity, eccentricity, independent of sizeindependent of size

► Critical spacing is Critical spacing is roughly half of the roughly half of the eccentricityeccentricity

Crowding and FamiliarityCrowding and Familiarity

► Context improves Context improves recognition at low, recognition at low, hinders at high hinders at high eccentricitieseccentricities

► Crowding has a bigger Crowding has a bigger impact on recognition impact on recognition than familiaritythan familiarity

ConclusionConclusion

► Invariance of Object Recognition originate Invariance of Object Recognition originate from groups of neurons with similar from groups of neurons with similar specific stimuli but differences in specific stimuli but differences in attributes of thoseattributes of those

►Receptive fields depend on backgroundsReceptive fields depend on backgrounds

►Object Recognition depends on feature-Object Recognition depends on feature-contextcontext

QuellenQuellen

► K. Tanaka, Inferotemporal Cortex and Object Vision, Annu. K. Tanaka, Inferotemporal Cortex and Object Vision, Annu. Rev. Neurosci., 1996Rev. Neurosci., 1996

► E.T. Rolls et al., The Receptive Fields of Inferior Tempral E.T. Rolls et al., The Receptive Fields of Inferior Tempral Cortex Neurons in Natural Scenes, J. Neurosci., 2003Cortex Neurons in Natural Scenes, J. Neurosci., 2003

► M. Martelli et al., Are faces processed like words? A diagnostic M. Martelli et al., Are faces processed like words? A diagnostic test for recognition by parts, Journal of Vision, 2005.test for recognition by parts, Journal of Vision, 2005.

Thank you for your attention